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1
Wolcott, John Fredric. "Flume studies of gravel bed surface response to flowing water". Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/31033.
Testo completoAbstract (sommario):
Almost all sediment transport equations incorporate the Shields parameter, which is a ratio of the total boundary shear stress as a driving force and the particle weight as a resisting force. Shields (1936) equated particle resistance to entrainment with particle weight, which is proportional to particle diameter, or bed texture. The present work analyses the particle resistance term in the Shields parameter.
As the bed material adjusts to a given flow condition, bed stability increases. The arrangement of particles into more stable configurations is here termed geometric structure, and includes the formation of pebble clusters, and imbrication. After an initial surface coarsening, here termed textural structure, particle resistance to movement is a function primarily of geometric structure. The Shields number for entrainment is thus a measure of particle resistance due to both types of bed structure rather than the conventional notion of particle resistance due to particle weight.
The response of a mobile bed surface composed of < 8 mm diameter gravels to flowing water was explored in a 6 meter by 0.5 meter flume using four different slopes and various water depths. Corrected bed shear stresses varied between 0.05 and 2.79 Pa. Step increases in discharge with a constant slope caused the bed surface to develop a structure which was more stable at the end of a run than at the beginning. Under these conditions, the Shields number for incipient motion was found to vary between 0.001 and 0.066. This variability can be explained by the degree of geometric structure present. Previous studies, including Shields' work (1936), have implicitly included the effects of geometric structure on incipient motion.
Surface coarsening develops with very low flows, but subsequent coarsening in higher flows is minor, with less than 5% increase in median diameter following a 50% increase in bed shear stress. Calculations of Manning's n based on depth, slope, and velocity measurements show an increase in flow resistance as structure develops. The development of a coarse surface layer appears to be limited by flow characteristics near the bed which are in turn modified by the development of structure. Measurements of the area occupied by the largest stones show that they do not cover more than 14% of the surface during maximum coarsening. Froude scaling of the flume data indicates that the time necessary for development of maximum strength is on the order of a month for natural rivers under steady flow conditions. This suggests that gravel river beds are rarely in equilibrium with natural flow conditions.Arts, Faculty of
Geography, Department of
Graduate
2
Nyander, Annie. "River bed sediment surface characterisation using wavelet transform-based methods". Thesis, Edinburgh Napier University, 2004. http://researchrepository.napier.ac.uk/Output/5885.
Testo completoAbstract (sommario):
The primary purpose of this work was to study the morphological change of river-bed sediment surfaces over time using wavelet transform analysis techniques. The wavelet transform is a rapidly developing area of applied mathematics in both science and engineering. As it allows for interrogation of the spectral made up of local signal features, it has superior performance compared to the traditionally used Fourier transform which provides only signal averaged spectral information. The main study of this thesis includes the analysis of both synthetically generated sediment surfaces and laboratory experimental sediment bed-surface data. This was undertaken using two-dimensional wavelet transform techniques based on both the discrete and the stationary wavelet transforms. A comprehensive data-base of surface scans from experimental river-bed sediment surfaces topographies were included in the study. A novel wavelet-based characterisation measure - the form size distribution ifsd) - was developed to quantify the global characteristics of the sediment data. The fsd is based on the distribution of wavelet-based scale-dependent energies. It is argued that this measure will potentially be more useful than the traditionally used particle size distribution (psd), as it is the morphology of the surface rather than the individual particle sizes that affects the near bed flow regime and hence bed friction characteristics. Amplitude and scale dependent thresholding techniques were then studied. It was found that these thresholding techniques could be used to: (1) extract the overall surface structure, and (2) enhance dominant grains and formations of dominant grains within the surfaces. It is shown that assessment of the surface data-sets post-thresholding may allow for the detection of structural changes over time.
3
Stromback, Anna Christina. "A sub-surface evaluation of the Weissliegend facies, UK, southern North Sea". Thesis, University of Liverpool, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250239.
Testo completo
4
Jönsson, Anette. "Model studies of surface waves and sediment resuspension in the Baltic Sea /". Linköping : Faculty of Arts and Science, Linköping University, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-4680.
Testo completo
5
Jönsson, Anette. "Model Studies of Surface Waves and Sediment Resuspension in the Baltic Sea". Doctoral thesis, Linköpings universitet, Tema vatten i natur och samhälle, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-4680.
Testo completoAbstract (sommario):
Wave heights and periods of surface waves in the Baltic Sea have been modelled for a two-year period (1999-2000) with the wave model Hypas on an 11x11-km grid scale. There is a clear seasonal variation with higher waves during winter and lower during summer. This is mainly a reflection of the wind climate in the area where the winters are windier than the summers. The largest waves are found in the Skagerrak and over the deeper, eastern areas in the Baltic Proper. In the Baltic Sea, the surface waves influence the bottom sediment by initiating resuspension down to 80 m depths. This process is dependent not only on the waves but also on the varying grain size diameters. Fine and medium sand resuspend more often than other sediment types, and these sediments cover together about 25% of the Baltic Proper area. On average sediment is here resuspended 4-5 times per month with a duration for each event of 22 hours. The highest resuspension frequencies are found on the eastern and southern side of the Baltic Proper. During resuspension sediment grains are lifted up into the water mass and matters earlier bound in the sediment can be released. This may stimulate both production and degradation of organic matter.
6
He, Zhiguo. "Numerical simulation of flow, sediment, and contaminant transport in integrated surface-subsurface systems /". Full text available from ProQuest UM Digital Dissertations, 2007. http://0-proquest.umi.com.umiss.lib.olemiss.edu/pqdweb?index=0&did=1414125241&SrchMode=1&sid=1&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1221163101&clientId=22256.
Testo completo
7
Solaimani, Karim. "Estimating changes in morphology and sediment supply using remote sensing and field techniques in the Lar Dam Basin, Iran". Thesis, University of Glasgow, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321067.
Testo completo
8
Beasley, Jeffrey S. "Nitrogen Regime Influence on Nutrient and Sediment Surface Runoff During Vegetative Establishment of Bermudagrass". Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/31900.
Testo completoAbstract (sommario):
Bermudagrass (Cynodon dactylon (L.) Pers.) is a popular turfgrass used throughout the Southeast. Bermudagrass is established primarily as sprigs on large acreage sites. Currently, the industry standard practice (ISP) of fertilization during
bermudagrass sprig establishment is 48.8 kg N ha-1 wk-1. This fertilizer rate can be excessive on morphologically immature sprigs in the initial weeks of establishment, thus making the possibility of offsite surface runoff N events more likely. Two experiments were conducted in 2000 and 2001 where sprigs were established at 2, 4, 6, 8, and 10 weeks prior to applying simulated rainfall (WPRS) following N fertilization rates of the ISP or a lower initial N (LIN) rate of 12.2 kg N ha-1 wk-1 the first four weeks and then
48.8 kg N ha-1 wk-1 until full establishment. At the tenth week all treatments were subjected to rainfall simulation at 63.5 mm hr-1. Once surface runoff was induced, rainfall continued for thirty minutes during which time runoff samples were taken every five minutes and analyzed for sediment losses, N concentrations in the nitrate and ammonium forms, and phosphorus losses as dissolved reactive P (DRP). Experimental results indicate an ability to curb N losses through surface runoff during the initial weeks of sprig establishment following the LIN with only modest delays in sprig establishment.
Sprigs established for the same time period, under the ISP or LIN, were very similar in
growth, release of surface runoff, and sediment losses during runoff events.Master of Science
9
Steenhauer, Kate. "An experimental and numerical study of surface-subsurface interaction for bore-driven swash on coarse-grained beaches". Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources. Restricted: no access until Nov. 24, 2011, 2010. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=59381.
Testo completo
10
Ståhlberg, Carina. "Mineralisation rates of natural organic matter in surface sediments affected by physical forces : a study of fresh- and brackish-water sediments subjected to changed redox conditions, resuspension, and advective pore water flow /". Linköping : Department of Water and Environmental Studies, [The Tema Institute], Linköping University, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-8332.
Testo completo
11
Bilici, Cagdas. "Development of a Sediment Sampling Free Fall Penetrometer Add-on Unit for Geotechnical Characterization of Seabed Surface Layers". Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/96146.
Testo completoAbstract (sommario):
In-situ geotechnical testing of surficial sediment layers in areas of active sediment dynamics can provide essential information about physical and geotechnical variations of sediment properties with regards to active sediment remobilization processes. For example, portable free fall penetrometers (PFFPs) can assist with the detection of mobile sediment layers. They are easy to deploy, and can provide a large spatial coverage in a time- and cost-effective manner. However, they often struggle to provide more detailed information about the properties of mobile sediment layers due to a lack of calibration and validation in existing data sets. Currently, existing sediment samplers often disturb, or ignore the uppermost sediment layers. Simultaneous sediment sampling and geotechnical profiling is needed to fill this gap, and to drive data interpretation forward. A field investigation of surficial sediments was conducted in the wetland waterways of coastal Louisiana in 2014. In-situ tests were conducted using PFFP, and disturbed sediment samples were collected in selected locations. The results allowed us to map changes in sediment strength and stratification, and correlate the geotechnical results to local site characteristics. However, the need for high quality sediment samples for calibration and validation was emphasized by the results. Three different sediment sampler add-on units targeting mobile layers were designed and manufactured based on lessons-learned from the literature. The designs were tested in the laboratory and in the field (Yakutat, Alaska and York River, Virginia) in 2017. The samples were analyzed to understand the influence of different sampler characteristics on collected sample quality, and, to define mobile layer sampler characteristics that enable simultaneous geotechnical testing and the collection of high quality samples. Following field survey campaigns in the York River, Virginia in 2016 allowed to assess surficial sediment layer characteristics and behavior based on a coupled analysis of geotechnical data from in-situ PFFP tests and the sedimentological data collected using box cores and the novel sediment sampler. In summary, novel strategies and instrumentation to carry out simultaneous sediment sampling and geotechnical profiling of seabed surface layers were tested, and new pathways for geotechnical data analysis for the investigation of mobile seabed layers were presented.PHD
12
Reid, David A. "Reach-scale contributions of road-surface sediment to the Honna River, Haida Gwaii, B.C". Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/50061.
Testo completoAbstract (sommario):
Unpaved resource road surfaces may act as dominant sources of fine sediment to streams, yet their relative contribution to in-channel sediment yields remains poorly understood. Significant quantities of road-surface sediment have been observed entering the Honna River, B.C, a 5th order channel located is close proximity to a major, intensively used resource road. In September 2012, a reach of the Honna River was selected for measurement and instrumentation to compile a sediment balance with a focus on the relative importance of road surface sediment over an annual scale. An additional four months of suspended-sediment data were collected at 6 locations in the reach to determine spatial and temporal dynamics of suspended-sediment concentrations and yields. Road surface sediment contributed 19% ± 6% of the total annual fine sediment balance for the reach, even though only ~20% of the road area was an effective sediment source. Persistent clockwise hysteresis was observed in the SSC-discharge relation in the main river channel, but was not as apparent in ditch drainage channels. As a proportion of total input, road surface material ranged from 0.5% to 15% during dry conditions from April to the end of September, and from 5% to 70% in the wet season from October to the end of March. Road surface material appears likely to settle on the river channel bed during low flow conditions, but only temporarily, and in small quantities relative to natural sediment sources. Additional research is needed to assess basin-scale contributions of road surface sediment.Arts, Faculty of
Geography, Department of
Graduate
13
Barlow, James Vincent. "Accumulation, transport and potential treatment of surface sediment on car parks with channel drains". Thesis, Cranfield University, 2015. http://dspace.lib.cranfield.ac.uk/handle/1826/10599.
Testo completoAbstract (sommario):
Urban pollutants have been identified as a significant source of environmental pollution, posing a risk to human health, the environment, and are toxic to flora and fauna. Highways are recognised as one of the key sources of pollution, from both vehicles, and surrounding infrastructure. A number of studies have investigated accumulation of sediment and the associated pollutants on highways, and the runoff generated as a result of rainfall. Car parks share many potential contributory sources of pollutants with highways, but there is a lack of studies regarding car parks, despite them being identified as a significant percentage of urban land use. A series of experiments were undertaken in order to develop an understanding of the characteristics of car park sediment. The physical and chemical characteristics of sediment were analysed at different stages throughout the drainage system. Firstly on the sediment accumulated on car park surfaces, followed by that mobilised and transported into a channel drain during simulated rainfall events. Finally, potential treatment of pollutants within sediment in a channel was quantified. The physical and chemical characteristics of car park sediment was shown to be similar during both the accumulation (build-up) and wash-off stages, suggesting that the accumulated sediment is generally mobilised and transported to the channel drain (wash-off). Furthermore, both the physical and chemical characteristics of the sediment were shown to be similar to those found on highways, thorough the build-up and wash-off phases. Finally, potential treatment of organic pollutants (PAH) by biodegradation was demonstrated, but not comprehensively proved.
14
Shmelev, Alexey Alexandrovich. "Three-dimensional acoustic propagation through shallow water internal, surface gravity and bottom sediment waves". Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/69241.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and the Woods Hole Oceanographic Institution), 2011.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 185-193).
This thesis describes the physics of fully three-dimensional low frequency acoustic interaction with internal waves, bottom sediment waves and surface swell waves that are often observed in shallow waters and on continental slopes. A simple idealized model of the ocean waveguide is used to analytically study the properties of acoustic normal modes and their perturbations due to waves of each type. The combined approach of a semi-quantitative study based on the geometrical acoustics approximation and on fully three-dimensional coupled mode numerical modeling is used to examine the azimuthal dependence of sound wave horizontal reflection from, transmission through and ducting between straight parallel waves of each type. The impact of the natural crossings of nonlinear internal waves on horizontally ducted sound energy is studied theoretically and modeled numerically using a three-dimensional parabolic equation acoustic propagation code. A realistic sea surface elevation is synthesized from the directional spectrum of long swells and used for three-dimensional numerical modeling of acoustic propagation. As a result, considerable normal mode amplitude scintillations were observed and shown to be strongly dependent on horizontal azimuth, range and mode number. Full field numerical modeling of low frequency sound propagation through large sand waves located on a sloped bottom was performed using the high resolution bathymetry of the mouth of San Francisco Bay. Very strong acoustic ducting is shown to steer acoustic energy beams along the sand wave's curved crests.
by Alexey Alexandrovich Shmelev.
Ph.D.
15
Eke, O. C. Enyinna. "Surface water and sediment geochemistry in understanding mobility of nitrates in mesic Kansas grassland". Thesis, Kansas State University, 2011. http://hdl.handle.net/2097/13273.
Testo completoAbstract (sommario):
Master of ScienceDepartment of Geology
Saugata Datta
To understand ambient nitrate dynamics in an unmanaged grassland environment, the stable isotope chemistry of various substrates at the Konza Prairie Biological Station were studied. Sediments consisted of alluvium, loess and bedrock materials are mostly limestone and shale. To gain a better understanding of the biogeochemistry of N cycling in this unmanaged grassland, 34 water samples have been collected along a full stretch of the major onsite creeks (Kings and Shane Creeks). These samples have been analyzed for δD, δ18O, and δ15N to determine the manner by which water allows nitrates to be leached into sediment, and to determine if additional nitrate is contributed from weathering of the bedrock. The anion chemistry of the waters show the presence of bicarbonates, sulfates, chlorides, nitrates, and fluorides. Although an obvious correlation among the anions is not present, data shows high alkalinity content due to the presence of shallow bedrock that is continuously being weathered. Using a hydraulic geoprobe, sediment cores were collected up to 8 ft deep using 2 ft core liners adjacent to the creeks to study δ15N and δ13C spatial variation of the sediments. This research also indicated the presence of C3 and C4 derived soil organic carbon with the latter being dominant. There is also an approximate 1:9 correlation between the total nitrogen and carbon content of these core sediments including NO3 and NH4 that are mostly concentrated in the upper 2 – 4 ft of the sediment profile. The results of this study provide a broader context for ambient nitrate cycling in unmanaged grassland and a baseline comparison for nitrate levels in surrounding agricultural lands.
16
Fincham, Mark J. "Coccoliths and oxygen isotope observations from the sediment surface of the southwest Indian Ocean". Master's thesis, University of Cape Town, 1986. http://hdl.handle.net/11427/26540.
Testo completoAbstract (sommario):
The interplay of three important parameters, dissolution, dilution and winnowing seem to be controlling the state in which sediment material is preserved in the study area though most samples examined under the SEM were generally well preserved. The distribution of forty-four coccolithophore species in one hundred deep sea core-tops from the southwest Indian Ocean is described. Three coccolith assemblages have been recognised (Maputo, Agulhas Current and deep water) and are delineated by the relative abundances of four ecologically significant coccolithophore species (Gephyrocapsa oceanica, Emiliania huxleyi, Calcidiscus leptoporus and Umbilicosphaera sibogae). These four species are the most abundant in the study area and the major factors influencing their geographical distribution seem to be temperature, nutrient concentration and dissolution. Coccolith and foraminifera preservations indicate that the carbonate lysocline lies somewhere between 3500 and 4000 meters, resulting in the concentration of dissolution resistant microfossils below this depth. Stable oxygen isotope ratios in a planktonic foraminifera and percent abundances of E. huxleyi reveal that apart from cores taken in the Agulhas Passage, most of the core-top samples are probably less than 85,000 yrs. BP. Lightest isotope ratios of -1.5 to -1.0 per mil PDB (equal to 22.8 to 25.1°C) occur in a narrow band on the sea floor beneath the "A" route of the Agulhas Current. These values are about 0.5 per mil PDB lighter than samples analyzed on either side of this band and can be explained by the Agulhas Current's elevated temperature at the ocean surface of between 2 to 3°C. Thus, an oxygen isotope imprint of the Agulhas Current exists beneath it on the sea floor. The Agulhas Current is probably the major factor influencing sedimentation, sediment distribution patterns and geological features in the study area. At present it is voluminous and fast flowing, possibly eroding sediments 2500 meters below the surface. The oxygen-isotope ratios and nannoplankton counts obtained in this study indicate however, that the majority of samples are most probably recent or at least not older than 85,000 years except for sediments found in the Agulhas Passage. This implies that sediments are accumulating on the ocean floor and that the current does not have a pronounced erosional influence, at least in areas from which cores were retrieved for this study.
17
Huang, Lingyan. "Mass transport due to surface waves in a water-mud system". Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B35380457.
Testo completo
18
Schmidt, Susanne I. "Surface water, groundwater interactions and their association with sediment fauna in a Western Australian catchment /". Marburg : Tectum-Verl, 2005. http://deposit.ddb.de/cgi-bin/dokserv?id=2660074&prov=M&dok_var=1&dok_ext=htm.
Testo completo
19
Desilets, Sharon. "Flood Processes in Semi-arid Streams: Sediment Transport, Flood Routing, and Groundwater - Surface Water Interactions". Diss., The University of Arizona, 2007. http://hdl.handle.net/10150/195652.
Testo completoAbstract (sommario):
Flooding in semi-arid streams is highly variable but distinguished from its humid counterpart in terms of forcing conditions, landscape response, flood severity, and stream-aquifer connectivity. These floods have the potential for great benefit in a water-limited environment, but also great devastation when powerful floods encounter human infrastructure. This dissertation employs an integrative approach to address several facets of flooding in semi-arid streams. In particular, information from field sampling during flood events combined with modeling are used to evaluate the processes of post-disturbance sediment transport, flood routing, transient bank storage, and stream disconnection. The major findings show: (1) Suspended sediment composition in floods following wildfire depends on the number, timing, and intensity of preceding storms and flood events, implicating overland flow hillslope processes as a dominant mass wasting mechanism (2) Isotopic chemographs for two representative intense convective storm events demonstrate that the flash flood bore develops from predominantly high elevation event water that overcomes, incorporates, and pushes baseflow to the front of the hydrograph peak (3) Isotope information combined with a plug-flow model can simulate this flood bore mixing process simultaneously in two separate canyons in the basin in order to calculate the timing and quantity of flow; this could be a useful tool for watersheds that are not extensively instrumented, or for calibrating a more complex or distributed model, (4) For a stream connected to an underlying aquifer, a circulation pattern develops at the onset of flooding that causes an upwelling of antecedent water into the unsaturated zone, challenging the assumptions of one dimensional, lateral flow and transport into the streambank, and (5) For small stream-aquifer disconnections, large increases in infiltration, large decreases in seepage, and a dominantly vertical profile for floodwater were observed. This implies that a stream that supports a wide riparian corridor may be in danger of vegetation die-offs with even shallow depletions of the groundwater table.
20
Bai, Yang. "Simulating Surface Flow and Sediment Transport in Vegetated Watershed for Current and Future Climate Condition". Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/333038.
Testo completoAbstract (sommario):
The complex interaction between flow, vegetation and sediment drives the never settled changes of riverine system. Vegetation intercepts rainfall, adds resistance to surface flow, and facilitates infiltration. The magnitude and timing of flood flow are closely related to the watershed vegetation coverage. In the meantime, flood flow can transport a large amount of sediment resulting in bank erosion, channel degradation, and channel pattern change. As climate changes, future flood frequency will change with more intense rainfalls. However, the quantitative simulation of flood flow in vegetated channel and the influence of climate change on flood frequency, especially for the arid and semi-arid Southwest, remain challenges to engineers and scientists. Therefore, this research consists of two main parts: simulate unsteady flow and sediment transport in vegetated channel network, and quantify the impacts of climate change on flood frequency. A one-dimensional model for simulating flood routing and sediment transport over mobile alluvium in a vegetated channel network was developed. The modified St. Venant equations together with the governing equations for suspended sediment and bed load transport were solved simultaneously to obtain flow properties and sediment transport rate. The Godunov-type finite volume method is employed to discretize the governing equations. Then, the Exner equation was solved for bed elevation change. Since sediment transport is non-equilibrium when bed is degrading or aggrading, a recovery coefficient for suspended sediment and an adaptation length for bed load transport were used to quantify the differences between equilibrium and non-equilibrium sediment transport rate. The influence of vegetation on floodplain and main channel was accounted for by adjusting resistance terms in the momentum equations for flow field. A procedure to separate the grain resistance from the total resistance was proposed and implemented to calculate sediment transport rate. The model was tested by a flume experiment case and an unprecedented flood event occurred in the Santa Cruz River, Tucson, Arizona, in July 2006. Simulated results of flow discharge and bed elevation changes showed satisfactory agreements with the measurements. The impacts of vegetation density on sediment transport and significance of non-equilibrium sediment transport model were accounted for by the model. The two-dimensional surface flow model, called CHRE2D, was improved by considering the vegetation influence and then applied to Santa Cruz River Watershed (SCRW) in the Southern Arizona. The parameters in the CHRE2D model were calibrated by using the rainfall event in July 15th, 1999. Hourly precipitation data from a Regional Climate Model (RCM) called Weather Research and Forecasting model (WRF), for three periods, 1990-2000, 2031-2040 and 2071-2079, were used to quantify the impact of climate change on the magnitude and frequency of flood for the Santa Cruz River Watershed (SCRW) in the Southern Arizona. Precipitation outputs from RCM-WRF model were bias-corrected using observed gridded precipitation data for three periods before directly used in the watershed model. The watershed model was calibrated using the rainfall event in July 15th, 1999. The calibrated watershed model was applied to SCRW to simulate surface flow routing for the selected three periods. Simulated annual and daily maximum discharges are analyzed to obtain future flood frequency curves. Results indicate that flood discharges for different return periods are increased: the discharges of 100-year and 200-year return period are increased by 3,000 and 5,000 cfs, respectively.
21
Cantone, Carolina. "Modelling sediment connectivity in Swedish catchments and application for flood prediction of roads". Thesis, KTH, Mark- och vattenteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-190612.
Testo completoAbstract (sommario):
Climate changes are predicted to increase precipitation intensities and occurrence of extreme rainfall events in the near future. Scandinavia has been identified as one of the most sensitive regions in Europe to such changes; therefore, an increase in the risk for flooding, landslides and soil erosion is to be expected also in Sweden. An increase in the occurrence of extreme weather events will impose greater strain on the built environment and major transport infrastructures such as roads and railways. This research aimed to identify the risk of flooding at the road-stream intersections, crucial locations where water and debris can accumulate and cause failures of the existing drainage facilities. Two regions in southwest of Sweden affected by an extreme rainfall event in August 2014, were used for calibrating and testing a statistical flood prediction model. A set of Physical Catchment Descriptors (PCDs) including road and catchment characteristics was identified for the modelling. Moreover, a GIS-based topographic Index of Sediment Connectivity (IC) was used as PCD. The novelty of this study relies on the adaptation of IC for describing sediment connectivity in lowland areas taking into account contribution of soil type, land use and different patterns of precipitation during the event. A weighting factor for IC was calculated by estimating runoff calculated with SCS Curve Number method, assuming a constant value of precipitation for a given time period, corresponding to the critical event. The Digital Elevation Model of the study site was reconditioned at the drainage facilities locations to consider the real flow path in the analysis. These modifications led to highlight the role of rainfall patterns and surface runoff for modelling sediment delivery in lowland areas. Moreover, it was observed that integrating IC into the statistic prediction model increased its accuracy and performance. The calibrated model was then validated in another area, located in the central part of Sweden, affected by severe rainfall event in August 2004, in order to verify its robustness even in ungauged catchments.
22
Rouse, Helen Louise. "The development of a transfer function relating surface waves to bedload gravel transport using the self-generated noise technique". Thesis, University of Hull, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265126.
Testo completo
23
Huang, Lingyan, e 黃凌燕. "Mass transport due to surface waves in a water-mud system". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B35380457.
Testo completo
24
Cakiroglu, Ayse Idil. "Salinity Inference In Inland Turkish Shallow Lakes On Paleoecology Using Sub-fossil Cladocera". Phd thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615450/index.pdf.
Testo completoAbstract (sommario):
In the current study, sub-fossil Cladocera collected from the surface sediment of 44 shallow lakes spanning over five latitudes from north to south of Turkey using snap-shot methodology revealed strong impact of salinity on cladoceran community structure. To see the whole picture, sediment cores collected from six of the lakes and long-term monitoring data from two of the lakes were also investigated.
Contemporary cladocerans and sub-fossil assemblages were compared to reveal that their responses to salinity changes were highly similar. This lead us to use sub-fossil cladocerans and salinity data from water column together while generating the calibration data set using ordination techniques. Salinity transfer function models were developed utilising weighted averaging techniques. The developed salinity transfer function was applied to cladocera assemblages from dated sediment cores. Hindcasting of the salinity inference model was performed using monitoring data and the reconstructed salinities from two central Anatolian lakes and reflected good linear correlation with the known lake salinity history.
This thesis has confirmed that sub-fossil Cladocera is a valuable indicator of historical salinity change and marker for the monitoring of lakes. For the first time, the lake environmental variables and sub-fossil cladoceran species composition from the surface sediments of Turkish shallow lakes were studied and a salinity transfer function was developed to elucidate past salinity change. The approach of the current study has been proven to be reliable while interpreting past salinity conditions. Since monitoring programmes are scarce in Turkey, paleolimnological analyses would be beneficial especially when defining effective restoration strategies.
25
Graham, George W. "Biomediation of turbulence and suspended sediment characteristics in marsh surface flows : the influence of Spartina anglica". Thesis, University of Plymouth, 2008. http://hdl.handle.net/10026.1/1765.
Testo completoAbstract (sommario):
Laboratory experimentation in a large aimular flume (radius 3 m, channel width and water depth 0.4 m) has been conducted using a geometrically and dynamically similar Spariina anglica mimic (canopy height 0.21 m, stem density 1000 stems m~^) to investigate the influence of submerged Spartina on hydrodynamics under unidirectional currents {Uh = 0.2 m s~*) and the impact upon the dynamics of suspended cohesive sediments near the bed within the canopy. The vertical distribution of canopy biomass strongly influences vertical profiles of time-averaged velocity and turbulent quantities. An inflected velocity profile is observed in the region 0.79 < z/h < 0.9 which generates shear, T K E and Reynolds Stress peaks within vicinity of the canopy top. In this region T K E peaks at 15 times the levels observed in un-vegetated experiments. Flows at the canopy top are strongly intermittent with extremely efficient downward momentum transfer, uf] and ufz (stream-wise and vertical zero-mean fluctuating velocity) skewness are 0.5 and -0.5 indicating the presence of intermittent downward penetrating gusts. Near the bed (0 < z/h < 0.3) mean flow velocities are reduced by 88 - 90% in comparison to un-vegetated flows but turbulence intensities are strongly augmented by wake shedding from vegetative elements. TKE in this region is approximately equal to that in un-vegetated flows. Novel field observations in a low energ>', estuarine fringing marsh site on the Tavy Estuary, UK, with a vertical array of synchronous velocimeters and optical backscatter sensors exhibit low velocities (<0.6 ra s"*) and suspension concentrations (<100 mg L"*) in agreement with laboratory simulations. While field observations of near bed flows exhibit similarity to those measured in the laboratory, magnitudes of time-averaged flow throughout the water column are so small that the velocity profile appears constant over depth. Superimposed upon the low field velocities are small wind generated waves ( < 0.05 m in height and with periods < 3 s) which have a considerable impact on flow energy and stress estimates, but crucially, cannot be replicated in the laboratory experiments. Dissipation rates within the laboratory canopy are 70-200x10"'* m~^s"^ giving reduced Kohnogorov length scales of 0.04 - 0.14 mm. Field values for dissipation are generally of similar magnitude but peak at up to 600 X10"** m~^s~^. Kolmogorov length scales are consequently 0.06 - 2.6 mm. Using natural intertidal mud, suspension concentrations of 100-200 mg L~* have been sheared through the mimic canopy. Observations from a vertical array of miniaturised OBS sensors suggests sediments are maintained in suspension twice as long, under constant unidirectional currents, compared to un-vegetated flows. In the field initial concentrations of 100 mg L~* quickly decay to background levels of <20 mg L"* indicating the rapid setthng of material from suspension. Use of a novel digital in-line holographic particle iinaging system and the development of a particle tracking methodology has enabled the high resolution observation of both sample size and settling velocities of suspended cohesive particles. Laboratory observations of sample averaged size (74.5 - 111.7 mm) and settling rates (0.35 - 1 mm s~*) are in agreement with published estimates and the limited observational data that exists for settling rates in marsh systems. Settling velocities estimated in the field at 0.1 - 0.8 mm s~^. Significantly larger and fast settling aggregates have been observed than previously recorded. In the narrow range of experimental suspension concentrations and shear stresses utilised in the present experiments, significant diff^erences in particle size and settling velocity between vegetated and un-vegetated flows cannot be identified. Contrasting flux estimates using sample averaged settling rates and concentrations with full spectral estimates derived from the holographic particle imager indicate an error in the former fluxes of, on average, 62%. The range of settling rates observed during the pr^ent study raises questions regarding the accurate representation of marsh surface settling fluxes in numerical simulations. Large magnitude flux errors may have significant implications for accurate accretion rates in numerical models of marsh sedimentation.
26
Sibali, LL, JO Okonkwo e C. Zvinowanda. "Determination of DDT and Metabolites in Surface Water and Sediment Using LLE, SPE, ACE and SE". Springer Science, 2009. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1001502.
Testo completoAbstract (sommario):
Abstract
Surface water and sediment samples collected
from Jukskei River in South Africa, were subjected to
different extraction techniques, liquid–liquid (LLE), solidphase
extraction (SPE), activated carbon extraction (ACE)
and soxhlet extraction (SE) for sediment. The samples were
extracted with dichloromethane, cleaned in a silica gel
column and the extracts quantified using a Varian 3800
GC-ECD. The percentage recovery test for 2,40DDT, DDE
and DDD and 4,40DDT, DDE and DDD in water ranged
from 80%–96% and 76%–95% (LLE); 56%–76% and
56%–70% (SPE) and 75%–84% (ACE), respectively; while
that recoveries for sediment samples varied from 65%–
95% for 2,40DDT, DDE and DDD and 80%–91% for
4,40DDT, DDE and DDD. The high recoveries exhibited by
ACE compared very well with LLE and SE. This was not
the case with SPE which exhibited the lowest value of
recoveries for both 2,4 and 4,40DDD, DDE and DDT
standard samples. The mean concentrations of DDT and
metabolites ranged from nd-1.10 lg/L, nd-0.80 lg/L, nd-
1.21 lg/L and 1.92 lg/L for LLE, SPE, ACE and SE,
respectively. The total DDT (2,40 and 4,40-DDT) in water
and sediment samples ranged from 1.20–3.25 lg/L and
1.82–5.24 lg/L, respectively. The low concentrations of
the DDT metabolites obtained in the present study may
suggest a recent contamination of the river by DDT.
27
Roussel, Erwan G. "Subseafloor archaeal communauties : from the surface to a deep hot biosphere ?" Brest, 2008. http://www.theses.fr/2008BRES2019.
Testo completoAbstract (sommario):
La biosphère de sub-surface océanique représente les deux tiers de la biomasse de la Terre. Ces importantes populations microbiennes enfouies sous la surface du plancher océanique jouent un rôle clé dans les cycles biogéochimiques. Bien que la profondeur maximale de cette biosphère de sub-surface ne soit toujours pas déterminée actuellement, celle-ci serait limitée par des facteurs physico-chimiques tels que la température ou l’absence de source d’énergie. Certains microorganismes non-cultivés du domaine des Archaea jouent probablement un rôle majeur dans l’écosystème sédimentaire marin profond et hydrothermal. Afin de contourner les limitations des approches culturales, les outils moléculaires sont principalement utilisés pour l’étude des communautés microbiennes de la biosphère profonde. Ainsi, dans le but de déterminer les facteurs environnementaux contrôlant la distribution des Archaea dans la biosphère profonde océanique, ce travail de recherche a comparé la diversité moléculaire (ARNr 165 et les gènes codant pour des enzymes spécifiques de différentes voies métaboliques) associée à quatre écosystèmes différents de subsurface les sédiments marins profonds côtiers, océaniques, ceux des marges continentales, et l’environnement hydrothermal. Ce travail de recherche a permis (i) de caractériser la distribution des communautés d’Archaea dans différents contextes biogéochimiques, (ii) de mettre en évidence de nouveaux phylotypes, (Hi) de proposer une nouvelle définition de la sub-surface profonde (iv) d’étendre la profondeur de la biosphère marine profonde jusqu’à au moins 1626 m sous la surface du sédimentThe sub-seafloor biosphere may contain two thirds of Earth’s total prokaryotic biomass. The large and active microbial populations buried in the sub-seafloor play a key role in global biogeochemical cycles. However, little is known about these prokaryotic communities. The depth limit of this sub-seafloor biosphere is still unreached, and elevated temperatures as well as insufficient energy sources are the likely factors limiting life at depth. Lnterestingly, archaeal communities with unknown physiologies and no cultured relatives seem to have a key role in deep marine sediments and hydrothermal ecosystems. As most deep biosphere microorganisms detected so far have been extremely resistant to cultivation, molecular approaches remain to date the most appropriate tools for the analysis of the overall prokaryotic communities in sub-surface environments. In order to determine the main environmental factor driving the archaeal diversity in the sub-seafloor, the present study is mainly focused on the comparison of the 165 rRNA (RNA- or DNA- derived) and functional gene diversity associated with four different sub-seafloor ecosystems: deep coastal margin and open-ocean sediments, and hydrothermal environment. The present study (i) shows the distribution of the archaeal communities within different biogeochemical habitats, (ii) reveals new phylogenetic lineages, (iii) proposes a different definition of the deep sub-surface, (iv) expands the known sub-seafloor biosphere to at least 1,626 meters below seafloor
28
Ruiz, Rueda Olaya. "Nitrifying and denitrifying bacterial communities in the sediment and rhizosphere of a free water surface constructed wetland". Doctoral thesis, Universitat de Girona, 2008. http://hdl.handle.net/10803/7871.
Testo completoAbstract (sommario):
La contínua descàrrega de nutrients, sobretot fosfats i nitrogen, és la major causa d'eutrofització dels ecosistemes aquàtics. Els sistemes de tractament basats en aiguamolls construïts s'han emprat per reduir ells nivells de nitrogen a l'aigua com a alternativa de baix cost als mètodes de depuració convencionals. L'eliminació del nitrogen a aquests sistemes depèn en bona part de la vegetació, i l'alternança de condicions aeròbiques i anaeròbiques per promoure els processos de nitrificació i desnitrificació. En aquest treball hem volgut investigar les activitats microbianes de nitrificació i desnitrificació en relació a dues espècies de plantes macròfites en un sistema d'aiguamolls de tractament de flux superficial (FS-SAC), dissenyat per minimitzar l'impacte de l'alliberament d'aigua carregada de nutrients a la reserva natural dels Aiguamolls de l'Empordà (Girona, Espanya).The continuous delivery of nutrients, mainly phosphate and nitrogen, is the major cause of eutrophication of aquatic environments. Treatment technologies based on constructed wetlands have been applied to reduce the levels of nitrogen as a cost-effective alternative compared to conventional treatment methods. The nitrogen removal efficiency in wetlands relies on the presence of plants and the alternation of aerobic and anaerobic conditions to promote both nitrification and denitrification. Although the role of emergent macrophytes in such systems is largely recognized, their contribution to the overall treatment process has not been quantified very frequently. We have investigated the microbial nitrification and denitrification activities in relation to two plant species in a free water surface constructed wetland (FWS-CW), designed to minimize the impact of nutrient release into the Natural Reserve of Els Aiguamolls de l'Empordà (Girona, Spain).
29
Langlois, Jacques. "Nutrient and sediment movements from soil to surface water in a forested watershed and two agricultural fields". Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19751.
Testo completoAbstract (sommario):
In North America, the acceleration of the eutrophication of surface waters due to nutrient pollution is still present. Soil studies have not entirely succeeded in linking nutrient and sediment losses to field hydrology because relationships between discharge and dissolved ions/sediments are complicated by a hysteresis effect which has been only described qualitatively. The objective of this thesis was to better understand the effects of hydrology on N, P, and sediment transfer from agricultural and forest soils to surface waters. This was done by developing a technique, called the H index, to quantify the hysteretic behaviour of ion and sediment transport in stream/overland water. The chemical and sediment concentrations in a stream of a forested watershed in the Sierra Nevada during snowmelt and in overland runoff of two agricultural fields during rain events in the Montreal area were examined. In the stream of the forested watershed, H indices for suspended sediment increased (looser hysteresis loop) with the availability of sediments and the lag between peaks in suspended sediment concentrations and discharge. In agricultural fields, nutrient concentrations increased with time during each event with presence of counterclockwise and clockwise hysteresis. The hysteretic behaviour of suspended sediments was not significantly related with either prior soil moisture content or rainfall characteristics. In order to simultaneously monitor P and N in the stream and soils of the forested watershed, a laboratory study was conducted to investigate the efficacy of various mixedbed exchange resins in absorbing dissolved organic and inorganic N and P. Results showed that mixed-bed resin was adequate for characterizing P on a short-time scale but longer exposure periods were required for N. Results from the resin exchange reveal the possibility that the spring time pulse of NOs'-N in stream water was due to the melting of the snowpack.
30
Sabat, Mira. "Mathematical modeling of suspended sediment transport in free surface flows : from the empirical to the numerical approach". Strasbourg, 2011. http://www.theses.fr/2011STRA6130.
Testo completoAbstract (sommario):
La distribution verticale de la concentration des sédiments en suspension joue un rôle majeur dans l’étude du taux et la capacité de transport d’une rivière. Il existe, dans la bibliographie, plusieurs modèles de distribution des vitesses et des concentrations dont les conditions d’utilisation sont souvent ambigües. Vue la difficulté des mesures sur terrain, il est nécessaire d’utiliser et de savoir choisir un profil numérique. Le but de cette thèse est de concevoir de nouveaux outils pour étudier la distribution verticale des vitesses et des concentrations. Dans ce contexte, nous présentons deux nouveaux coefficients de diffusivités obtenus par l’introduction d’opérateurs de corrections au profil parabolique. Ces deux modèles donnent en utilisant l’équation de convection diffusion et le principe de Boussinesq deux profils analytiques de concentration et de vitesse. Aussi nous mettons au point une méthode qui permet de faire le choix entre les différents modèles mathématiques représentants le même phénomène physique et deux méthodes pour l’intersection des profils et pour l’extension des profils dans les cas où le modèle applicable n’est pas unique ou n’existe pas. Ensuite, nous appliquons cette méthode à l’étude des profils verticaux de vitesse et des distributions de la concentration des sédiments en suspension en régime stationnaire et uniforme, et nous développons le code expert pour la distribution verticale des concentrations, code_ERESA. Dans une annexe, nous testons l’utilisation du code de volumes finies code_Saturne pour l’étude de la distribution verticale des vitesses et des concentrations des sédiments en suspension dans les écoulements de surfaceThe vertical distribution of suspended sediment concentration and velocity plays a major role in the study of the transport rate and the transport capacities of a river. Many suspended sediments concentration and velocity profiles exist in the literature, having ambiguous conditions of application. In addition, it is not easy to conduct in – situ measurements. This reveals, not only the utility of using numerical profiles, but also the responsibility of choosing an optimal one. The present thesis aims to conceive new tools for studying the vertical velocity and concentration distribution. In this context, we present two new sediment diffusivity coefficients obtained by the introduction of correction operator on the parabolic diffusivity coefficient. These models are implemented in the convection diffusion equation to generate two analytical concentration profiles and using the Boussinesq assumption, they lead to two analytical velocity profiles. Also, we conceive a method for choosing between different mathematical representation of a same physical phenomenon, and two methods for the intersection between these representations when more than one is applicable and for the extension of the representations to the cases where no model is applicable. We apply this method on the study of the vertical velocity profile and the sediment distribution in steady and uniform sediment laden open channel flows, and we develop the expert system for the vertical sediment concentration distribution code_ERESA. In an appendix, we test the use of the finite volume code_Saturne for the study of the vertical velocity distribution and suspended sediment concentration in open channel flows
31
Yu, Chunshui. "Two Dimensional Finite Volume Model for Simulating Unsteady Turbulent Flow and Sediment Transport". Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/301662.
Testo completoAbstract (sommario):
The two-dimensional depth-averaged shallow water equations have attracted considerable attentions as a practical way to solve flows with free surface. Compared to three-dimensional Navier-Stokes equations, the shallow water equations give essentially the same results at much lower cost. Solving the shallow water equations by the Godunov-type finite volume method is a newly emerging area. The Godunov-type finite volume method is good at capturing the discontinuous fronts in numerical solutions. This makes the method suitable for solving the system of shallow water equations. In this dissertation, both the shallow water equations and the Godunov-type finite volume method are described in detail. A new surface flow routing method is proposed in the dissertation. The method does not limit the shallow water equations to open channels but extends the shallow water equations to the whole domain. Results show that the new routing method is a promising method for prediction of watershed runoff. The method is also applied to turbulence modeling of free surface flow. The κ - ε turbulence model is incorporated into the system of shallow water equations. The outcomes prove that the turbulence modeling is necessary for calculation of free surface flow. At last part of the dissertation, a total load sediment transport model is described and the model is tested against 1D and 2D laboratory experiments. In summary, the proposed numerical method shows good potential in solving free surface flow problems. And future development will be focusing on river meandering simulation, non-equilibrium sediment transport and surface flow - subsurface flow interaction.
32
Silva, Camila MagalhÃes. "Detection Aeromonas spp. in surface water samples and sediment along a salinity gradient in river estuary Cocà - CearÃ". Universidade Federal do CearÃ, 2009. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=13386.
Testo completoAbstract (sommario):
This research work was designed to detect the presence of Aeromonas in the Cocà River estuary, Fortaleza, Cearà State, Brazil. The database consisted of 30 samples of the riverâs surface water and 30 samples of the riverâs sooil, in the period from September, 2007 to April, 2008.. They were amenable, simultaneously, to counting of bacteria on Agar Gelatin Phosphate Salt (GSP) plus 20μg/mL of ampicilim (UFC/mL or UFC/g) The results showed dissemination of Aeromonas in the estuary. The counts for the water samples varied from 10 to 7,050 and from 25 to 38,500 UFC/mL at points A and B respectively; and from 100 to 37,500 UFC/g, and 1,200 to 43500 UFC/g at points A and B respectively. At point C, the counts for water and sediment were smaller than 10 UFC per ml or gram in all samples The occurrence of the greatest indices of Aeromonas in April, at the height of the rainy season, and the lowest in Septemer, at the height of the dry season, suggests there to be a probable seasonality of bacteria density in the studied environment. Among the 41 isolated strains were found the species A. caviae, A. sobria, A. trota, A. salmonicida and A. allossacharophyla. All the strains of Aeromonas sp. were found to be sensitive to cloranfenicol and ceftriaxona except for ampicillim, to which they showed 100% resistance.All the stirps showed resistance to two out of the nine tested antibiotics. After the Curingâ technique, the eritromicina resistance seems to be of plasmidian origin.Este projeto teve como objetivo principal a pesquisa de Aeromonas spp. em Ãgua de superfÃcie e sedimento em trÃs pontos distintos ao longo do rio CocÃ, CearÃ. Foram realizadas coletas no perÃodo de outubro de 2007 a abril de 2008 gerando um total de 30 amostras de Ãgua e 30 de sedimento. A quantificaÃÃo da comunidade bacteriana pertencente ao gÃnero Aeromonas foi feita atravÃs de plaqueamento direto sobre Agar Gelatina Fosfato Sal (Agar GSP acrescido de 20μg/mL de ampicilina). Nas amostras de Ãgua, os valores obtidos variaram de 10 a 7.050 UFC/mL e de 25 a 38.500 UFC/mL nos pontos A e B, respectivamente. Nas amostras de sedimento, as contagens variaram de 100 a 37500 UFC/g e 1.200 a 43.500 UFC/g nos pontos A e B, respectivamente. Nas amostras de Ãgua e sedimento do ponto C, os valores foram menores que 10 UFC (por mL ou g) em todas as coletas. As maiores contagens foram verificadas no mÃs de abril, perÃodo de chuva, e as menores no mÃs de setembro, perÃodo de estiagem. Foram feitos isolamentos e apÃs identificaÃÃo as estirpes foram submetidas à teste de antibiograma e à tÃcnica da âcuraâ do plasmÃdio. Dentre as 41 cepas isoladas, foram identificadas as espÃcies A. caviae, A. sobria, A. trota, A. salmonicida e A. allossacharophyla. Todas as cepas se mostraram sensÃveis ao cloranfenicol e ceftriaxona. Todas as estirpes apresentaram resistÃncia a, pelo menos, dois dos nove antibiÃticos testados. ApÃs a tÃcnica de cura, a maior parte da resistÃncia a eritromicina ficou caracterizada como de origem plasmidial.Conclui-se que o estuÃrio do Rio Cocà està contaminado por Aeromonas e que muitas delas apresentam resistÃncias a antibiÃticos denotando um ambiente poluÃdo e de risco para a populaÃÃo que usa suas Ãguas para lazer, pesca ou outra atividade qualquer.
33
Ståhlberg, Carina. "Mineralisation rates of natural organic matter in surface sediments affected by physical forces". Licentiate thesis, Linköping University, Linköping University, Department of Water and Environmental Studies, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-8332.
Testo completoAbstract (sommario):
Nedbrytning av organiskt material är en nyckelfaktor som påverkar omvandlingar av de många grundämnen som utgör eller är associerade till just organiskt material. En stor del av nedbrytningen av akvatiskt organiskt material (OM) sker i gränsskiktet mellan sediment och vatten. Eftersom så många biogeokemiska cykler styrs av nedbrytningen av OM är det viktigt att ha kunskap om processer och påverkansfaktorer både på mikro- och makronivå. Mineraliseringshastigheten av OM är en vanligt förekommande mätparameter, men vanligtvis inkluderar mätningarna inte de naturliga processer som kan påverka nedbrytnings-hastigheterna, t.ex. fysiska krafter.
Syftet med den här studien är att studera mineraliseringshastigheten av det OM som finns naturligt i ytsediment i söt- och brackvatten när det utsätts för fysiska krafter som orsakar förändringar i redox-förhållanden, resuspension eller advektivt porvattenflöde. Fem
laborativa experiment har utförts för att belysa syftet:
Åldrat ytsediment från en sötvattens å utsattes för olika redox förhållanden där oxisk respiration, sulfatreduktion respektive metanogenes gynnades. Resultaten visade ingen skillnad i mineraliseringshastighet beroende på behandling. Detta motsäger studier utförda i marina miljöer, där anoxiska förhållanden ger en lägre mineraliseringshastighet än oxiska.
Vidare gjordes två studier på brackvattensediment där effekten av resuspension var i centrum. Den ena studien fokuserade på frekvens och varaktighet av resuspensionstiderna, den andra på olika typer av sediment. Studierna visade att väldigt korta resuspensionstider med upp till 48 timmars stillhet mellan varje resuspension ökade mineraliseringstakten med fem gånger jämfört med diffusivt utbyte, och mer än dubblerades i jämförelse med kontinuerlig resuspension eller resuspension i långa perioder. Resuspensionen under kort tid var troligen gynnande då resuspension fysiskt stör bildningen av stabila bakteriesamhällen. Mineraliseringshastigheterna i sediment som domineras av väldigt fin, fin eller medium sand visade lika hastigheter, medan grov sand visade en signifikant lägre mineraliseringshastighet. Likheterna mellan de tre första sedimenttyperna kan dock ha påverkats av tillgång på lättnedbrytbart OM då sediment och vatten hämtades in under en algblomning.
Till sist studerades effekten på mineraliseringshastigheten av advektivt porvattenflöde. Detta gjordes på åldrat sediment dels från en sötvattensbäck dels från en brackvattenstrand. Inget av de två sedimenttyperna visade någon skillnad i mineraliseringshastighet i jämförelse med diffusivt styrda system. Det är i motsats till tidigare marina studier, men är i linje med den första studien, där mineraliseringshastigheten var oberoende av redox-förhållande.
Den generella slutsatsen från den här studien är nödvändigheten att studera samma aspekter i olika typer av akvatiska system, eftersom responsen verkar vara annorlunda beroende på system, t.ex. söt- brack- och saltvatten. Faktorer som kan förklara de här skillnaderna finns ännu inte, vilket gör att småskaliga studier och modeller blir viktiga verktyg för att utreda detta.
Organic matter mineralisation is a key parameter that affects most other element transformations associated with organic matter. A substantial part of aquatic organic matter (OM) mineralisation takes place at the interface between sediment and water. Understanding OM mineralisation is important at both the micro and macro scales, since it drives many biogeochemical cycles. OM mineralisation rates are widely measured, but generally not all the natural factors possibly affecting the rates, such as physical forcing, are considered.
This thesis examines the mineralisation rates of indigenous OM in fresh and brackish surface sediments, subjected to different physical forces inducing changed redox conditions, resuspension, and advective pore water flow. Five experiments were performed to this end.
Aged surface sediment from a freshwater river was subjected to different redox conditions favouring oxic respiration, sulphate reduction, and methanogenesis, respectively. Results indicated no difference in mineralisation rate irrespective of treatment. This contradicts what has been found in marine environments, where anoxic mineralisation rates are lower than oxic ones.
Further, two studies of resuspension of brackish sediments were performed, one addressing the impact of the frequency and duration of the resuspension events, and the other addressing the impact of resuspension on different types of sediments. The studies found that very brief resuspension events followed by calm periods of up to 48 h increased mineralisation rates by five times compared to diffusion, and more than doubled the rate compared to continuous or long-term resuspension. The short-term events were possibly favoured because resuspension physically disturbs the arrangement of a stable bacteria community. Mineralisation rates on sediments dominated by very fine, fine, or medium-grained sand were the same, while coarse sand displayed a significantly lower rate. The similar rates of the three first sediment types could stem from access to labile OM, due to an ongoing algae bloom when the sediment and water samples were collected.
Finally, the effect of advective pore water flow on aged sediment from one fresh and one brackish sediment was studied. Neither of the sediments displayed a mineralisation rate different from those occurring in incubations in which only diffusive exchange occurred. This contradicts the findings of previous marine studies, but is in line with the first study, which did not detect different mineralisation rates irrespective of redox conditions.
The general conclusion is that it is necessary to study the same physical forces in different aquatic environments, since responses appear to differ, for example, between freshwater, brackish, and marine environments. Factors explaining these differences have not yet been expressed, making small-scale studies and modelling a challenge for future research.
34
Saxton, H. Thomas. "Soil genesis studies of upland soils formed in transported materials overlying the Virginia Piedmont using trend-surface analyses". Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-01102009-063235/.
Testo completo
35
Russo, Joseph Paul. "INVESTIGATION OF SURFACE FINE GRAINED LAMINAE, STREAMBED, AND STREAMBANK PROCESSES USING A WATERSHED SCALE HYDROLOGIC AND SEDIMENT TRANSPORT MODEL". UKnowledge, 2009. http://uknowledge.uky.edu/gradschool_diss/750.
Testo completoAbstract (sommario):
Sediment transport at the watershed scale in the Bluegrass Region of Kentucky is dominated by surface fine grained laminae, streambed, and streambank erosion; high instream sediment storage; and surface erosion processes. All these processes can be impacted by agricultural, urban, and suburban land-uses as well as hydrologic forcing. Understanding sediment transport processes at the watershed scale is a need for budgeting and controlling sediment pollution, and watershed modeling enables investigation of the cumulative effect of sediment processes and the parameters controlling these processes upon the entire sediment budget for a watershed. Sediment transport is being modeled by coupling the hydrologic model Hydrologic Simulations Program-FORTRAN (HSPF) with an in-house conceptually based hydraulic and sediment transport model. The total yield at the watershed outlet as well as the source fractions from surface fine grained lamina, streambed, and streambank sources; deposition; and biological generation within the streambed are predicted with the sediment transport model. Urbanization scenarios are then run on the calibrated model so as to predict the sediment budget for the South Elkhorn watershed for present and future conditions.
36
CARDOSO, CARLOS EDUARDO. "SOLID SURFACE ROOMTEMPERATURE PHOSPHORIMETRY FOR THE SELETIVE DETERMINATION OF NITROGENATED AND SULPHURATED POLYCICLIC AROMATIC COMPOUNDS INGASOLINE AND SEDIMENT SAMPLE". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2007. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=10085@1.
Testo completoAbstract (sommario):
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROPETRÓLEO BRASILEIRO S. A.
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Neste trabalho, métodos analíticos baseados na fosforimetria na temperatura ambiente foram desenvolvidos para a determinação de sete compostos policíclicos aromáticos (CPA) sulfurados e nitrogenados presentes do petróleo. Mais especificamente, o objetivo foi o de fornecer ferramentas analíticas que permitissem avaliar e quantificar estes CPA em gasolina e em uma amostra ambiental (sedimento). Adicionalmente, a informação obtida através da fosforimetria mostrou potencial para permitir diferenciar amostras (por exemplo, a identificação de amostras contaminadas) por meio de perfil em três dimensões ou curvas de nível. A aplicação de técnica de varredura sincronizada e o uso do efeito externo seletivo do átomo pesado aumentaram o grau de seletividade e de discriminação entre amostras, pois induziu fosforescência de componentes específicos na amostra e melhorou a resolução espectral dos resultados. Inicialmente, foi feito um estudo das características fosforescentes das substâncias em diferentes condições experimentais, seguido da maximização do sinal fosforescente de cada uma das substâncias nas condições experimentais mais propícias para observação do sinal fosforescente. Para tal, o papel filtro, previamente tratado para redução do sinal de fundo, foi utilizado como substrato sólido para imobilização dos analitos, permitindo a observação de intensa fosforescência na temperatura ambiente. Os parâmetros de mérito das metodologias desenvolvidas para cada um dos analitos em questão foram obtidos. As faixas lineares se estenderam entre 1,0 x 10-7 e 5,0 x 10-4 mol L-1, considerando as concentrações das soluções dos analitos aplicadas no substrato. Os coeficientes de determinação (r2) obtidos ficaram sempre acima de 0,9784. Os limites de detecção absolutos (para 5 µL de amostra) foram todos na ordem do ng, mostrando a capacidade para detecção sensível em termos de massa efetiva de analito. Os testes de repetibilidade mostraram valores variando entre 12 e 18%, o que pode ser considerado satisfatório para a técnica realizada em substrato sólido. Também foram conduzidos estudos de robustez e reprodutibilidade. Alternativamente, sinais fosforescentes foram maximizados em condições experimentais secundárias do ponto de vista da magnitude de sinal, mas potencialmente relevantes do ponto de vista da seletividade. Testes de recuperação indicaram, na maioria dos casos, resultados bastante satisfatórios no caso das misturas sintéticas contendo quantidades eqüimolares de componentes (nesse caso, foram testadas várias combinações de analitos e de interferentes) ou contendo interferentes, em concentrações cinco vezes maior que a do analito de interesse. Nos casos mais críticos em termos de interferências, recursos instrumentais ou quimiométricos foram aplicados para melhorar a seletividade e possibilitar a quantificação. Os métodos desenvolvidos foram testados em amostras simuladas de gasolina, em gasolina comercial e em uma matriz ambiental (sedimento) fortificadas com os analitos de interesse. As recuperações obtidas foram bastante satisfatórias e compreendidas entre 90% e 117%. Estudos envolvendo varreduras de fosforescência total (TPS) também foram realizados, com o intuito de se obter uma impressão digital característica para cada um dos analitos. Testes de TPS em gasolina comercial indicaram a presença de pelo menos seis dos sete analitos estudados, devido à obtenção de perfis espectrais muito semelhantes aos dos padrões. Testes adicionais mostraram a capacidade de identificar contaminações (misturas) na gasolina pela adição de diesel e de querosene.
In this work, analytical methods based on room-temperature phosphorimetry were developed aiming the quantification of seven polycyclic aromatic compounds (PAC) containing sulfur and nitrogen present in petroleum. More specifically, the goal was to obtain analytical tool to allow the evaluation and the quantification of these PCA in sediment and gasoline. In addition, the phosphorimetric information displayed potential for the discrimination of samples (for instance, the identification of contaminated samples) by means of three dimension plots or level curves. The application of synchronized sweeping technique and the use of the selective external heavy atom effect had increased the degree of selectivity and discrimination between samples, since it induces phosphorescence from specific components of the sample and improved the spectral resolution of the results. Initially, a study of the phosphorescent characteristics of the compounds in different experimental conditions was made, followed of the signal maximization in the most appropriate experimental conditions for the observation of phosphorescence. Filter paper, previously treated for background reduction, was employed as solid substrate for the immobilization of analytes. The analytical figures of merit for each one of the methods had been obtained. The linear range varied between 1,0 x 10-7 mol L-1 and 5,0 x 10-4 mol L-1, taking into consideration the concentration of the solutions spotted on the substrate. The determination coefficient values (r2) were always above of 0.9784. The absolute limits of detection (5 µL sample) were in ng order, showing the sensitivity of the developed methods. The repeatability tests had enabled values varying between 12 and 18%, which can be considered satisfactory for solid substrate technique. Robustness and reproducibility studies were also carried out. Additionally, secondary experimental conditions, in terms of signal magnitude, were optimized since these could be relevant from the selective point of view. Recovery tests indicated, in most of the cases, satisfactory results for synthetic mixtures containing equimolar quantities of components (in these cases, several analyte/interferent combinations were tested) and containing interferents in concentrations five times higher than the one of the analytes. In the most critical cases in terms of interferences, instrumental or quimiometric approaches had been applied to improve selectivity and make the quantification possible. The developed methods had been tested in simulated gasoline samples, commercial gasoline and in a sediment sample fortified with the analytes of interest. The obtained recoveries had been considered satisfactory and within 90 and 117%. Total phosphorescence scanning (TPS) studies had been also carried out in order to get the characteristic fingerprint for each one of the compounds of interest. TPS tests in gasoline had indicated the presence of six out of seven of the studied analytes, since very similar fingerprints were obtained. Additional tests had demonstrated the capability of this procedure to detect gasoline contaminations with diesel or kerosene.
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Bartlett, Joseph Hollis. "Impacts of Transportation Infrastructure on Stormwater and Surface Waters in Chittenden County, Vermont, USA". ScholarWorks @ UVM, 2016. http://scholarworks.uvm.edu/graddis/426.
Testo completoAbstract (sommario):
Transportation infrastructure is a major source of stormwater runoff that can alter hydrology and contribute significant loading of nutrients, sediment, and other pollutants to surface waters. These increased loads can contribute to impairment of streams in developed areas and ultimately to Lake Champlain. In this study we selected six watersheds that represent a range of road types (gravel and paved) and road densities (rural, suburban, and urban) present in Chittenden County, one of the most developed areas in Vermont. The location and density of road networks were characterized and quantified for each watershed using GIS analysis. Monitoring stations in each watershed were constructed and instrumented to measure discharge and water quality parameters continuously from spring through early winter. Storm event composite samples and monthly water chemistry grab samples were collected and analyzed for total nitrogen, total phosphorus, chloride, and total suspended sediments. Results from this study show that road type and road density are closely linked with the level of impairment in each watershed. Total phosphorus and total nitrogen from storm event composite samples and monthly grab samples significantly increased along a gradient of increasing road network density. Chloride concentrations increased several orders of magnitude along this same gradient. With the exception of Alder Brook where total suspended sediment (TSS) concentrations tended to be high, there were no significant differences in TSS concentrations between rural and developed watersheds. The elevated storm event TSS concentrations in the rural streams suggest that the unpaved roads in the rural watersheds contribute to stormwater runoff loads and that sediment control, at least in the developed watersheds, might be fairly effective. The overall results from this study show that local roads are a significant source of impairment for streams in the Chittenden County area. Most of these roads are municipal roads that are not under management of the Vermont Agency of Transportation. Thus, local actions will be necessary to reduce runoff and pollutant loading from these roads.
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Beazley, Melanie J. "The significance of organic carbon and sediment surface area to the benthic biogeochemistry of the slope and deep water environments of the northern Gulf of Mexico". Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969/534.
Testo completo
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Pollock, Matthew John. "Geomorphic Differences between Unmined and Surface Mined Lands in Southeastern Ohio". The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429613137.
Testo completo
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Brummer, Christopher Jon. "Influence of mass wasting on bed-surface armoring, lag formation, and sediment storage in mountain drainage basins of western Washington State /". Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/6738.
Testo completo
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Brown, Kristopher Ryan. "Sediment Delivery from Reopened Forest Roads at Stream Crossings in the Virginia Piedmont Physiographic Region, USA". Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/48424.
Testo completoAbstract (sommario):
Efforts to control surface runoff and erosion from forest roads at stream crossings are critical for the protection of aquatic ecosystems in forests. In this research, annual and event-based sediment delivery rates were estimated for reopened legacy roads at forest stream crossings in the Virginia Piedmont physiographic region, USA. Sediment delivery rates were compared among stream crossing approaches with diverse intensities of best management practice (BMP) implementations for surface cover and water control. Model predictions from the Water Erosion Prediction Project (WEPP) were compared to field observations of surface runoff and sediment delivery to evaluate model performance.
Annual sediment delivery rates from reopened (bare) legacy road approaches to stream crossings were 7.5 times higher than those of completely graveled approaches. Sediment delivery rates ranged from 34 to 287 Mg ha⁻¹ year⁻¹ for the bare approaches and from 10 to 16 Mg ha⁻¹ year⁻¹ for the graveled approaches. Event-based surface runoff and associated total suspended solids (TSS) concentrations were compared among a succession of gravel surfacing treatments that represented increasing intensities of BMP implementations on reopened approaches. The three treatments were No Gravel (10-19% cover), Low Gravel (34-60% cover), and High Gravel (50-99% cover). Median TSS concentration of surface runoff for the No Gravel treatment (2.84 g L⁻¹) was greater than Low Gravel (1.10 g L⁻¹) and High Gravel (0.82 g L⁻¹) by factors of 2.6 and 3.5, respectively. WEPP predictions of event-based sediment yield show clear differences among the different road surface treatments, but prediction intervals were wide, reflecting substantial prediction uncertainty.
These findings show that reopened legacy roads and associated stream crossing approaches can deliver significant quantities of sediment if roads are not adequately closed or maintained and that corrective best management practices (BMPs), such as gravel and appropriate spacing of water control structures, can reduce sediment delivery to streams. Watershed management decisions that hinge upon WEPP predictions of sediment yield from forest roads must necessarily take into account a wide range of potential erosion rates for specific management scenarios.Ph. D.
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Wijekoon, Nishanthi. "SPATIAL AND TEMPORAL VARIABILITY OF SURFACE COVER IN AN ESTUARINE ECOSYSTEM FROM SATELLITE IMAGERY AND FIELD OBSERVATIONS". Kent State University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=kent1194621824.
Testo completo
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Kreuger, Jenny. "Pesticides in the environment : atmospheric deposition and transport to surface waters /". Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 1999. http://epsilon.slu.se/avh/1999/91-576-5485-9.pdf.
Testo completo
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Santos, Julio Cesar Neves dos. "Hydrological and sedimentological processes in a tropical semiarid climate". Universidade Federal do CearÃ, 2015. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=15010.
Testo completoAbstract (sommario):
Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgicoThe understanding of processes such as the generation of surface runoff, sediment yield and their relations with the rainfall regime is the basis for the planning and effective management of soil and water resources in a watershed. In this context, the present study aims to identify the main processes that influence the generation of surface runoff and sediment yield in small watersheds, and determine parameters for empirical sedimentological models, as well as the Sediment Delivery Ratio (SDR) for the tropical, semi-arid region of Brazil. The study area is the Iguatu Experimental Basin (IEB), which comprises a watershed of 16.74 km2, three small nested watersheds (from 1 to 3 ha) and three erosion plots of 20 m2. One of the watersheds had been under regenerating Caatinga for 35 years, another subjected to a management, which involved thinning the Caatinga, and the last faced deforestation followed by burning and the cultivation of grass. The period of study was six years (2009 to 2014). Collections to quantify surface runoff and sediment yield were taken for each erosive rainfall event in an accumulated period of 24 hours. Surface runoff in the watersheds was quantified using Parshall flumes, and sediment yield was measured with towers and trenches to collect suspended sediment and bedload. On the watershed scale, runoff was measured by means of a spillway, and sediment yield by a turbidimeter. Cluster analysis was used to determine rainfall regimes and groups of similar rainfall-runoff events. With data from the erosion plots and watersheds, the C factors and coefficients of the Modified Universal Soil Loss Equation (MUSLE) were calibrated and validated. From data measured in the basin, sediment delivery ratios were determined. The occurrence of dry spells and the formation of cracks in the soil were important factors in controlling the generation of runoff and consequently sediment yield. The dry spells made it possible for the soil to dry out, with the formation of cracks, which acted as pathways for preferential flow, generating higher initial abstraction during the start of the rainy season. Changes in ground cover had little influence on accumulated flow, demonstrating that the soil characteristics and conditions as moisture and the presence of cracks, best explain the generation of runoff on expansive soils. The greatest runoff losses in all the watersheds under study were for Rainfall Regime II, characterized by higher depth, intensity and occurrence of the rainfall. For the ground covers under study, values for the C factors and the fit of the coefficients "a" and "b" of MUSLE, proved to be appropriate and recommended according to the statistical indices employed. Values for sediment delivery ratio for individual rainfall events ranged from 0.08 to 1.67%, with an average of 0.68%. In the basin, extreme events may cause high disaggregation of soil particles, but without sufficient transporting energy for dragging the sediment, generating low SDR.
O entendimento de processos como geraÃÃo do escoamento superficial, produÃÃo de sedimentos e suas relaÃÃes com o regime pluviomÃtrico à a base para o planejamento e a gestÃo eficaz dos recursos solo e Ãgua em uma bacia hidrogrÃfica. Nesse contexto, o presente estudo tem como objetivos identificar os principais processos que influenciam a geraÃÃo do escoamento superficial e a produÃÃo de sedimento em pequenas bacias hidrogrÃficas, e calibrar parÃmetros de modelos sedimentolÃgicos empÃricos, bem como a razÃo de aporte de sedimentos (SDR) para a regiÃo semiÃrida tropical do Brasil. A Ãrea de estudo à a Bacia Experimental de Iguatu (BEI), composta de uma bacia de 16,74 km2, trÃs pequenas microbacias aninhadas (de 1 a 3 ha) e trÃs parcelas de erosÃo de 20 m2. Uma das microbacias foi mantida com Caatinga em regeneraÃÃo hà 35 anos, outra submetida ao manejo de raleamento da Caatinga e na Ãltima foi realizado o desmatamento seguido de queimada e cultivo de capim. O perÃodo de estudo foi de seis anos (2009 a 2014). As coletas para quantificaÃÃo do escoamento superficial e da produÃÃo de sedimentos foram realizadas a cada evento de chuva erosiva, no acumulado de 24 horas. O escoamento superficial nas microbacias foi quantificado atravÃs de calhas Parshall e as produÃÃes de sedimentos foram mensuradas atravÃs de torres e fossos coletores de sedimentos em suspensÃo e arraste. Na bacia de 16,74 km2, o escoamento superficial foi mensurado por meio de um vertedor e a produÃÃo de sedimentos atravÃs de um turbidÃmetro. AnÃlises de agrupamento foram utilizadas para determinaÃÃo de regimes de chuvas e grupos de eventos similares de chuva-deflÃvio. Com dados das parcelas de erosÃo e das microbacias foram calibrados e validados os fatores C e os coeficientes da EquaÃÃo Universal de Perdas de Solo Modificada (MUSLE). A partir dos dados medidos na bacia foram determinadas as razÃes de aporte de sedimentos. A ocorrÃncia de veranicos e a formaÃÃo de fendas no solo foram determinantes no controle da geraÃÃo de escoamento e consequentemente da produÃÃo de sedimentos. A ocorrÃncia de veranicos possibilitou o secamento do solo com a formaÃÃo de fendas, que agem como caminhos preferenciais para o fluxo de Ãgua, gerando elevadas abstraÃÃes inicias durante o inÃcio da estaÃÃo chuvosa. As mudanÃas da cobertura vegetal apresentaram pouca influÃncia sobre o escoamento acumulado, indicando que as caracterÃsticas e condiÃÃes do solo, como umidade e presenÃa de fendas, explicam melhor a geraÃÃo de escoamento em solos expansivos. Maiores perdas por escoamento em todas as microbacias estudadas foram para chuvas do Regime II caracterizado por maiores alturas pluviomÃtricas, intensidades e ocorrÃncias. Quanto aos valores dos fatores C e dos coeficientes de ajuste âaâ e âbâ da MUSLE, para as coberturas estudadas, mostraram-se apropriados e recomendados de acordo com os Ãndices estatÃsticos empregados. Os valores da razÃo de aporte de sedimentos para eventos pluviomÃtricos individuais variaram de 0,08 a 1,67%, com mÃdia de 0,68%. Na bacia, eventos extremos podem causar elevada desagregaÃÃo de partÃculas de solo, mas podem nÃo dispor de energia de transporte suficiente para arrastÃ-las, gerando baixo SDR.
45
Marchal, Noe͏̈lle. "Relargage des micropolluants organiques par les sédiments de fond de rivière". Paris 5, 1992. http://www.theses.fr/1992PA05P044.
Testo completo
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Pankau, Ryan C. "CONCENTRATED FLOW PATHS IN RIPARIAN BUFFER ZONES OF SOUTHERN ILLINOIS". OpenSIUC, 2010. https://opensiuc.lib.siu.edu/theses/212.
Testo completoAbstract (sommario):
Riparian buffers in agricultural landscapes are designed to trap pollutants in overland flow by slowing, filtering, and infiltrating surface runoff entering the buffer via sheet flow. However, observational evidence suggests that concentrated flow is prevalent from agricultural fields. Also, over time sediment can accumulate in riparian buffers forming berms that restrict sheet flow from moving into the buffers; these berms ultimately back up surface runoff, resulting in an eventual breakthrough which concentrates runoff. Breakthrough by concentrated flow can lead to gully formation that may reduce the filtering capacities of buffer systems by providing direct conduits to stream channels. This study explores the frequency of concentrated flow paths in riparian buffers at both the field and watershed scale. At the field scale, intensive topographic surveys were conducted at 10 field sites in southern Illinois to characterize concentrated flow paths, accumulated berm sediments, and field area drained by concentrated flow. Detailed digital elevation models (DEMs) were created for each site and riparian buffer and agriculture field characteristics were analyzed to assess the development and occurrence of concentrated flow paths. At each site, soil samples were analyzed to characterize sediment deposition patterns within the buffer. To assess the prevalence of concentrated flow paths at the watershed scale, three watersheds in southern Illinois were selected for walking stream surveys. Five stream segments, approximately 1000 m long, were randomly selected within each watershed and surveyed for the occurrence and size of concentrated flow paths. These data were analyzed with respect to riparian buffer vegetation, buffer width, and surrounding land cover data. Concentrated flow paths were identified in all topographic surveys and all walking stream surveys indicating a common occurrence in agricultural watersheds of southern Illinois. Among field scale sites, concentrated flow accounted for 82.5-100% of the drainage areas contributing to riparian buffers. Results from the watershed scale analysis suggest that concentrated flow paths are significantly more abundant in agricultural land cover, than forested land. Current riparian buffer design principles are based on the assumption that sheet flow is the primary form of surface runoff entering buffers. Furthermore, buffers are installed and not maintained which can lead to berm accumulation and buffer failure. Results from this study indicate that concentrated flow was the prevalent form of runoff at field scale sites. Managers need to consider the occurrence of concentrated flow paths when designing riparian buffers to protect stream water quality.
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Lécrivain, Nathalie. "Étude de la contamination et de l'écotoxicité associée des sédiments de surface en zone littorale lacustre". Thesis, Lyon, 2019. http://www.theses.fr/2019LYSET001/document.
Testo completoAbstract (sommario):
La zone littorale, de grande importance pour le fonctionnement écologique du lac, est souvent la première zone réceptrice de la contamination provenant du bassin versant. Cette pollution est majoritairement piégée dans les sédiments de surface. Pour autant, les conditions environnementales variables qui règnent en zone littorale sont susceptibles de favoriser la biodisponibilité des contaminants par le jeu des réactions physico-chimiques et biologiques. Cette thèse s’appuie sur l’étude de deux grands lacs péri-alpins, le Lac du Bourget et le Lac d’Annecy, pour mieux comprendre le comportement des polluants sédimentaires (ETM, HAP et PCB) en zone littorale lacustre. Nos travaux visent notamment (1) à caractériser la contamination littorale et l’influence des sources locales dans cette contamination, (2) à évaluer l’écotoxicité des sédiments littoraux et les changements de mobilité et de biodisponibilité des polluants sédimentaires sous l’influence de changements abiotiques de la zone littorale tels que ceux induits par le marnage lacustre. Nos résultats montrent que la contamination des sédiments et organismes autochtones présente une hétérogénéité spatiale significative sur le littoral des deux lacs, tant en intensité qu’en composition (i.e. profil de contamination). L’implication de sources locales (e.g. eaux pluviales drainées sur le bassin-versant) dans cette hétérogénéité spatiale a été mise en évidence. L’écotoxicité des sédiments de la zone littorale, évaluée via la réponse de biomarqueurs enzymatiques (AChE, GST), physiologiques (e.g. taux d’ingestion chez D. magna) et des traits de vie (e.g. taux de croissance, reproduction et survie) présente également une hétérogénéité spatiale significative. La biodisponibilité des ETM sédimentaires a été plus spécifiquement étudiée aux interfaces sédiment-eau-biote. Elle varie selon l’élément, le biote exposé (benthique ou pélagique) et sous l’effet du marnage. L’assèchement et remise en eau du sédiment littoral s’accompagnent d’une réduction de la fraction biodisponible des ETM. L’abaissement de la hauteur d’eau, en revanche, entraîne une accentuation de la remise en suspension de particules sédimentaires susceptibles d’exercer un risque écotoxicologique sur le biote littoral. Nos résultats soulignent la complexité de la contamination littorale et de son transfert dans les grands lacs péri-alpins et encouragent les approches écotoxicologiques dans l’évaluation de l’état écologiqueThe littoral zone of lakes is of great ecological importance and yet receives a large array of contaminants from the watershed. This pollution is mainly trapped by the surface sediment, but its bioavailability may be allowed by physico-chemical and biological reactions in this zone of high environmental fluctuations. This work aims at improving knowledge about the behavior of sediment-borne contaminants (trace metals, PAHs and PCBs) in the lake littoral zone by using two large perialpine lakes; Lake Bourget and Lake Annecy. More precisely, our goals were to (1) characterize the littoral contamination and the influence of local sources in this contamination, (2) assess the ecotoxicity of the sediment-borne contamination and the main changes in its mobility and bioavailability under abiotic changes in the littoral zone, such as those related to water-level fluctuations in lakes. The contamination of the sediments and native organisms exhibited a significant spatial heterogeneity along the lake littoral, in both intensity and profile’s composition. The involvement of local sources of contamination (e.g. stormwater runoff) as drivers of this spatial heterogeneity has been highlighted. The ecotoxicity of littoral sediments was assessed through the responses of enzymatic biomarkers (AChE and GST), physiological traits (e.g. ingestion rates in D. magna) and life-history traits (e.g. growth, reproduction and survival rates). Our results also underscored a significant spatial heterogeneity of the littoral sediment ecotoxicity. A greater focus on the bioavailability of trace metals at the sediment-water-biota interfaces showed that bioavailability depends on the metal, the exposed biota (benthic vs pelagic) and fluctuate under water-level fluctuations. Drought and re-immersion of surface sediments were followed with a reduction of the bioavailable fractions of the trace metals. However, decreases in the water-level led to increase suspended sediments in the water column, which may exert an ecotoxicological risk for the littoral biota. Our results underline how complex the littoral contamination and bioavailability are and promote ecotoxicological approaches in the assessment of the ecological status of large lakes
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Gonçalves, Paulo Eduardo Reinach da Silva. "Determinação de metais potencialmente tóxicos em amostras de água e sedimentos nas bacias dos rios Cuiabá e São Lourenço - MT". Universidade Federal de Mato Grosso, 2014. http://ri.ufmt.br/handle/1/656.
Testo completoAbstract (sommario):
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CAPES
A contaminação dos recursos hídricos está diretamente ligada às atividades antrópicas. Algumas dessas atividades estão relacionadas à presença de metais que uma vez na água causam grande preocupação, pois estes não possuem caráter de biodegradabilidade, podendo acumular na biota aquática e chegar a níveis elevados causando efeitos adversos para o ambiente e a saúde humana. As bacias do rio Cuiabá e São Lourenço são de grande importância, pois a água dos seus rios é utilizada para diversos usos, além de abrangerem as principais cidades de Mato Grosso e por serem afluentes do rio Paraguai, o principal rio formador do Pantanal. Frente ao exposto, o objetivo deste trabalho foi a determinação da concentração de Cu, Cr, Cd, Mn, Fe, Pb e Zn em águas superficiais e sedimentos de fundo de rio das bacias do Rio Cuiabá e São Lourenço, Mato Grosso, Brasil. Os metais nas amostras de água foram determinados por espectrometria de absorção Atômica em chama e por espectrometria de emissão atômica com plasma indutivamente acoplado e, as amostras de sedimento por espectroscopia de absorção atômica em chama. Os resultados obtidos foram comparados com os valores máximos permitidos (VMP) pela Resolução no 357/2005 para a água doce de Classe II e pela Canadian Council of Ministers of the Environment (CCME) para os sedimentos. A análise de agrupamento hierárquica (AHA) revelou a existência de quatro agrupamentos para as amostras de água e dois agrupamentos para as amostras de sedimento. Com intuito de avaliar a qualidade dos agrupamentos foi realizada uma análise discriminante (AD) que mostrou uma classificação correta em 80% para as amostras de água e 79% para as amostras de sedimento. Além disso, a AD no modo “stepwise forward” mostrou que foi possível reduzir o número de variáveis avaliadas mantendo a mesma eficácia na classificação dos grupos. Gráficos de excedência mostraram que a maior parte dos resultados de concentração dos metais encontrados ficou abaixo do limite estabelecido pela legislação. Porém atenção deve ser dada para Pb e Cr que tanto nas amostras de água, quanto nas de sedimento foram encontrados valores de concentração acima do estabelecido pela legislação em alguns pontos da bacia do rio Cuiabá e São Lourenço, possivelmente proveniente de atividades antrópicas, como descartes de efluentes domésticos e industriais.
Contamination of water resources is directly linked to anthropic activities. Some of these activities can release metals in the environment which, once in the water, cause great concern since they are not biodegradable, can accumulate in the biota and so reach critical levels causing adverse effects to human health and to the environment. The watersheds of Cuiabá and São Lourenço rivers are of great importance since their water is applied to multiple uses, involving the main municipalities of Mato Grosso State. Moreover they are the main affluent of Paraguay river which is the most important contributor to the Pantanal of Mato Grosso. Thus, this study aimed to determine the concentration of Cu, Cr, Cd, Mn, Fe, Pb and Zn in surface water and riverbed sediment of Cuiabá and São Lourenço watersheds. Metals were analysed in water using flame atomic absorption spectrometry and inductive couple plasma emission spectrometry and in sediment using flame atomic absorption spectrometry. The metal concentrations in water were compared to the maximum allowed values established in the Resolution CONAMA n. 357/2005 for class II river waters while for sediments the values established by the Canadian Council of Ministers of the Environment (CCME) were used for comparison. The hierarchical cluster analysis revealed the existence of four groups regarding water quality and two groups of sediment. Discriminant analysis (DA) was applied to evaluate the grouping quality showing a correct classification of 80% of water and 79% of sediment samples. A análise de agrupamento hierárquica (AHA) revelou a existência de quatro agrupamentos para as amostras de água e dois agrupamentos para as amostras de sedimento. Moreover, DA in stepwise forward mode showed that it was possible to reduce the number of evaluated variables keeping the same efficiency in the groups classification. Exceedence curves showed that the majority of metal concentrations were below the limits established in the legislation. However, especial attention should be given to Pb and Cr that were detected in concentrations above these limits in water as well as in sediment samples in some sampling points, probably related to anthropic activities such as domestic and industrial effluents discharge.
49
Rodrigues, Joseilson Oliveira. "O uso da terra e a resposta hidrolÃgica de pequenas bacias em regiÃes semiÃridas". Universidade Federal do CearÃ, 2009. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=5215.
Testo completoAbstract (sommario):
Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgicoO objetivo central desse trabalho foi avaliar e comparar o comportamento hidrolÃgico e sedimentolÃgico em pequenas bacias rurais no semiÃrido nordestino, verificando a influÃncia da aÃÃo antrÃpica sobre os recursos solo e Ãgua. O estudo desses processos à de suma importÃncia na definiÃÃo de estratÃgias para o melhor gerenciamento de pequenas bacias hidrogrÃficas e na definiÃÃo de planos de sustentabilidade. A Ãrea de investigaÃÃo localiza-se na bacia do Alto Jaguaribe, mais precisamente no municÃpio de Iguatu, na regiÃo conhecida como Centro Sul do estado do CearÃ. A Ãrea experimental à composta por quatro microbacias com denominaÃÃo de B1, B2, B3 e B4 localizadas prÃximas entre si, foram delimitadas e equipadas com calhas Parshall, sensores de nÃvel de Ãgua, pluviÃgrafos e coletores automÃticos de sedimentos visando estudos hidrossedimentolÃgicos em condiÃÃes de chuva natural. Nessa pesquisa as Ãreas das bacias em avaliaÃÃo nÃo excederam 3 hectares, sendo na microbacia B1 aplicado um tratamento (raleamento), que permitiu avaliar a influÃncia da alteraÃÃo na cobertura vegetal da Caatinga sobre o escoamento superficial, descarga mÃxima e produÃÃo de sedimentos. As demais microbacias experimentais B2, B3 e B4 foram mantidas inalteradas, sem intervenÃÃo antrÃpica, representando condiÃÃes naturais de pequenas bacias rurais do semiÃrido do nordeste. Os dados analisados abrangem toda a estaÃÃo chuvosa de 2009 nas quatro unidades experimentais e alguns eventos nos meses de janeiro, fevereiro e marÃo de 2008 na microbacia B2. Apesar da proximidade entre as unidades de monitoramento, os resultados revelaram grande variabilidade espaÃo-temporal das respostas hidrossedimentolÃgicas, sendo a umidade anterior do solo a variÃvel de destaque na modificaÃÃo destas. Os resultados mostraram que a prÃtica de raleamento da Caatinga teve influÃncia na alteraÃÃo do escoamento superficial e produÃÃo de sedimentos, sendo os efeitos maiores sobre os primeiros eventos. A produÃÃo acumulada de sedimentos atingiu ao final de 2009 valores de 1,45; 1,39 e 0,12 ton ha-1 para as microbacias B1, B2 e B4, respectivamente. De todas as microbacias investigadas, B3 apresentou os maiores valores de escoamento superficial, e descargas mÃximas, com coeficiente de escoamento mÃdio em torno de 86%. A unidade experimental B4 mostrou-se com comportamento hidrossedimentolÃgico bastante diferenciado das demais microbacias, sendo nesta encontrado as menores magnitudes de descarga mÃxima, escoamento superficial e produÃÃo de sedimentos, comportamento este associado principalmente Ãs caracterÃsticas fÃsicas do solo da microbacia. Os resultados encontrados fornecem elementos importantes no campo hidrossedimentolÃgico em regiÃes semiÃridas, podendo ser empregados para nortear pesquisas futuras em microbacias com escoamento efÃmero.
This work was carried out to evaluate and to compare the hydrologic and sedimentologic behaviour of small rural catchments in the semiarid Northeast of Brazil, as well as to asses the influence of the anthropogenic action over soil and water resources. The study of theses processes is very important for the definition of strategies to a better management of small watersheds and the definition of sustainability plans. The study area is located in the Alto Jaguaribe basin, in the Iguatu County, State of CearÃ, Brazil. Four small catchments B1, B2, B3 and B4, neibor to each other, were delimited and equipped with Parshall flumes, water level sensors, rain-gauges and automatic sediment samplers, aiming hydrossedimentologic studies under natural rainfall conditions. In this research, the areas of studied catchments areas are smaller than three ha. In the B1 part of cover vegetation was cut, making it possible to assess the influence of changes in the vegetation cover over runoff, peak discharge and sediment yield. In the others catchments (B2, B3 and B4), cover vegetation was keeping in undisturbed condition, representing the natural condition in the semiarid region of northeast Brazil. The data analysed comprises the hydrologic year of 2009 on the four experimental unities and some events on the months of January, February and March of 2008 on the small catchment B2. Despite the proximity of the monitored unities, the results show high spatial and temporal variability of the hydrossedimentologic answer, and the antecedent soil moisture as the main variable responsible for such modifications. It was observed that lowering the density of the Caatinga vegetation influenced runoff and sediment yield, with greater effects over the first events. Accumulated sediment yield reached values of 1.45, 1.39 and 0.12 ton.ha-1 for the micro-catchments B1, B2 e B4, respectively, at the end of the year 2009. Among all investigated catchments, B3 presented the highest values of runoff and peak discharges, with runoff coefficient average around 28%. The B4 experimental unit had a hydrossedimentologic behaviour very different from the other catchments, showing the lowest values of peak discharge, runoff and sediment yield, and this behaviour can be explained to the soil characteristics. The results presented in this study contribute with important information for the hydrossedimentologic study of semiarid regions, and can be used to guide further research in small catchments with ephemeral regime.
50
Rodrigues, Joseilson Oliveira. "O uso da terra e a resposta hidrológica de pequenas bacias em regiões semiáridas". reponame:Repositório Institucional da UFC, 2009. http://www.repositorio.ufc.br/handle/riufc/18197.
Testo completoAbstract (sommario):
RODRIGUES, Joseilson Oliveira. O uso da terra e a resposta hidrológica de pequenas bacias em regiões semiáridas. 2009. 128 f. : Dissertação (mestrado) - Universidade Federal do Ceará, Centro de Ciências Agrárias, Departamento de Engenharia Agrícola, Curso de Mestrado em Engenharia Agrícola, Fortaleza-CE, 2009.Submitted by demia Maia (demiamlm@gmail.com) on 2016-07-07T14:22:18Z No. of bitstreams: 1 2009_dis_jorodrigues.pdf: 16309402 bytes, checksum: b2ab17d81f17cb85baf29eae39b670db (MD5)
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This work was carried out to evaluate and to compare the hydrologic and sedimentologic behaviour of small rural catchments in the semiarid Northeast of Brazil, as well as to asses the influence of the anthropogenic action over soil and water resources. The study of theses processes is very important for the definition of strategies to a better management of small watersheds and the definition of sustainability plans. The study area is located in the Alto Jaguaribe basin, in the Iguatu County, State of Ceará, Brazil. Four small catchments B1, B2, B3 and B4, neibor to each other, were delimited and equipped with Parshall flumes, water level sensors, rain-gauges and automatic sediment samplers, aiming hydrossedimentologic studies under natural rainfall conditions. In this research, the areas of studied catchments areas are smaller than three ha. In the B1 part of cover vegetation was cut, making it possible to assess the influence of changes in the vegetation cover over runoff, peak discharge and sediment yield. In the others catchments (B2, B3 and B4), cover vegetation was keeping in undisturbed condition, representing the natural condition in the semiarid region of northeast Brazil. The data analysed comprises the hydrologic year of 2009 on the four experimental unities and some events on the months of January, February and March of 2008 on the small catchment B2. Despite the proximity of the monitored unities, the results show high spatial and temporal variability of the hydrossedimentologic answer, and the antecedent soil moisture as the main variable responsible for such modifications. It was observed that lowering the density of the Caatinga vegetation influenced runoff and sediment yield, with greater effects over the first events. Accumulated sediment yield reached values of 1.45, 1.39 and 0.12 ton.ha-1 for the micro-catchments B1, B2 e B4, respectively, at the end of the year 2009. Among all investigated catchments, B3 presented the highest values of runoff and peak discharges, with runoff coefficient average around 28%. The B4 experimental unit had a hydrossedimentologic behaviour very different from the other catchments, showing the lowest values of peak discharge, runoff and sediment yield, and this behaviour can be explained to the soil characteristics. The results presented in this study contribute with important information for the hydrossedimentologic study of semiarid regions, and can be used to guide further research in small catchments with ephemeral regime.
O objetivo central desse trabalho foi avaliar e comparar o comportamento hidrológico e sedimentológico em pequenas bacias rurais no semiárido nordestino, verificando a influência da ação antrópica sobre os recursos solo e água. O estudo desses processos é de suma importância na definição de estratégias para o melhor gerenciamento de pequenas bacias hidrográficas e na definição de planos de sustentabilidade. A área de investigação localiza-se na bacia do Alto Jaguaribe, mais precisamente no município de Iguatu, na região conhecida como Centro Sul do estado do Ceará. A área experimental é composta por quatro microbacias com denominação de B1, B2, B3 e B4 localizadas próximas entre si, foram delimitadas e equipadas com calhas Parshall, sensores de nível de água, pluviógrafos e coletores automáticos de sedimentos visando estudos hidrossedimentológicos em condições de chuva natural. Nessa pesquisa as áreas das bacias em avaliação não excederam 3 hectares, sendo na microbacia B1 aplicado um tratamento (raleamento), que permitiu avaliar a influência da alteração na cobertura vegetal da Caatinga sobre o escoamento superficial, descarga máxima e produção de sedimentos. As demais microbacias experimentais B2, B3 e B4 foram mantidas inalteradas, sem intervenção antrópica, representando condições naturais de pequenas bacias rurais do semiárido do nordeste. Os dados analisados abrangem toda a estação chuvosa de 2009 nas quatro unidades experimentais e alguns eventos nos meses de janeiro, fevereiro e março de 2008 na microbacia B2. Apesar da proximidade entre as unidades de monitoramento, os resultados revelaram grande variabilidade espaço-temporal das respostas hidrossedimentológicas, sendo a umidade anterior do solo a variável de destaque na modificação destas. Os resultados mostraram que a prática de raleamento da Caatinga teve influência na alteração do escoamento superficial e produção de sedimentos, sendo os efeitos maiores sobre os primeiros eventos. A produção acumulada de sedimentos atingiu ao final de 2009 valores de 1,45; 1,39 e 0,12 ton ha-1 para as microbacias B1, B2 e B4, respectivamente. De todas as microbacias investigadas, B3 apresentou os maiores valores de escoamento superficial, e descargas máximas, com coeficiente de escoamento médio em torno de 86%. A unidade experimental B4 mostrou-se com comportamento hidrossedimentológico bastante diferenciado das demais microbacias, sendo nesta encontrado as menores magnitudes de descarga máxima, escoamento superficial e produção de sedimentos, comportamento este associado principalmente às características físicas do solo da microbacia. Os resultados encontrados fornecem elementos importantes no campo hidrossedimentológico em regiões semiáridas, podendo ser empregados para nortear pesquisas futuras em microbacias com escoamento efêmero.