Dissertations / Theses: 'Lake core'

1

Manson, K. J. "Aspects of the palaeolimnology of three Norfolk Broads." Thesis, University of East Anglia, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378901.

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Bridges, K. S. "Deposition processes and their impact on a heavily industrialized region of the northern Czech Republic." Thesis, University of East Anglia, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266752.

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Thapalia, Anita. "Zinc and copper isotopes as tracers of anthropogenic contamination in a sediment core from an urban lake." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.

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Fransner, Oscar. "Sediment variations in the Kuchi Lake, southern Taiwan: : Climate signal or tectonics?" Thesis, Stockholms universitet, Institutionen för geologiska vetenskaper, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-62193.

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Climate archives are of greatest significance when it comes to paleoclimate studies, since these types of archives in a natural way have registered and preserved the conditions of the past. There are several types of climate archives, one of the most commonly used are lake sediments, because lakes can reveal different types of information, for example weathering, vegetation and precipitation. Another reason why lakes are important in climate research is because they are widely spread over the world, and therefore they can be chosen depending on where the focus of the study will be. In this study, -the Lake Kuchi in the southern part of Taiwan, situated at the boundary between the Asian Mainland and the Western Pacific, was used. What makes this densely populated region of the world particularly interesting for climate research is because it is affected not only by monsoons, but also by typhoons and earthquakes. In this paleoclimate study, a total 16 core sections from three different coring points in the Kuchi Lake were analyzed. The main goal was to clarify if the lake could be used as a reliable climate archive, and also interpret the depositional environment of the sediment layers in the cores. All core sections were described and analyzed with the ITRAX XRF-scanner, which lead to the conclusion that the cores consist of a sedimentary sequence of alternating gray clay and dark gray gyttja clay layers, capped by peat, gyttja or clayey gyttja at topmost part. By sieving samples from all different layers, it was observed that some dark gyttja clay layers contained terrestrial organic matter, and hard, angular clay clasts that suggest intense rain falls and flash floods as transportation mechanism. The uppermost part of the cores, from 310 cm to the top layers, consist of homogenous clay and in situ organic matter which indicate calmer depositional environments compared to the alternation between dark gyttja clay and homogenous gray clay. LOI-950 data indicate that the carbonate content of the Kuchi Lake is low, since the weight loss during this temperature is insignificant compared to LOI-550, which stood for the majority of the weight loss. Thus, the sediment sequence in the Kuchi Lake consist of alternation of clays deposited in a calm and relatively deep lake, mixed with layers apparently flushed in from land, possibly due to typhoons. This alternation is capped by organic rich layers, including peat, which indicating filling up of the basin, and shallower conditions.

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Kilpatrick, Douglas. "The effects of population growth on Ecosystem services in lake Ekoln : A multi-proxy data analysis of a lake core and historical records." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-128822.

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Throughout human history man has utilized the environment to varying degrees, depending on technology and population. These ¨ecosystem services¨ have suffered sustained degradation over the centuries, resulting in large investments having to be made to prevent and reverse further changes to the environment. Few studies have attempted to quantitatively compare how these changes, occurring long before modern environmental monitoring programs started, affected important ecosystem services such as species diversity, water quality, carbon burial and soil stability. The aims of this study were to i) assess whether human impact on ecosystem services have varied over time in perspective of relative change, and ii) to assess the individual (per capita) contributions. I used multiple sediment proxies from a 6 m C¹⁴-dated core collected from lake Ekoln, South-Central Sweden, to reconstruct environmental changes while tracking the population growth in the city of Uppsala during the last ten centuries. Through the use of pollen and diatom assemblages I reconstructed the changing terrestrial and aquatic diversities over time, while sediment accumulation rates and the X-ray fluorescence spectroscopy of the sediment was used to reconstruct soil stability, carbon burial and water quality, respectively. In the latter case, sediment phosphorus concentrations were used as a proxy for freshwater eutrophication while metals (mercury and lead) were used to infer inputs of toxic pollutants. Finally, I normalized (z) all data to create meta-data. The z-values and reconstructed population for Uppsala made it possible to differentiate 5 unique time periods based on anthropogenic induced change, which were not previously visible in the data, and all of which have been linked to the most likely historical causes, including the Black Death. The results show that the most significant anthropogenic impacts in terms of pollution volume occurred in the 1960s, while the period from 1200-1500 AD saw the most significant environmental change in terms per head of capita, most likely caused by the shift from woodland to open landscape through twiddening, a process of burning forest to create agricultural land, prior to 1500 AD. Moreover, rapid recovery is visible after the implementation of environmental policies from the 1970s onwards.

Full surname: Kilpatrick van Houte

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Rojas, Rodríguez Clara. "Reconstructing the historic input of mercury in Lake Ekoln : A long-term (millennia) perspective derived from a sediment core." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-105160.

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Anthropogenic activities are often considered to be the main sources of mercury (Hg) found in aquatic systems. The aim of this study was to reconstruct the historic input of Hg to a large lake (Lake Ekoln) situated downstream the City of Uppsala using a dated sediment core. The main objective was to reveal general long-term (millennia-scale) trend in mercury loadings to the lake assess to what extent the lake has received an increase input of mercury during the last century from atmospheric inputs or local sources (mining activities, hospital effluents, industries or agricultural activities). Sediment samples were analyzed with X-ray fluorescence spectroscopy for measurements of lead and phosphorous (used as a proxy for atmospheric inputs and effluent water, respectively). Total Hg was analyzed using a mercury analyzer. My results indicate high Hg concentrations in sediment of Lake Ekoln during the last three centuries. Hg concentrations was not correlated to atmospheric derived metals (Pb) or effluent water derived nutrients (P) and only weakly correlated to the organic matter content of the sediment. Highest concentrations was found during a period around 1850 and in the last few years. The weak correlation with Pb suggest that the Hg is entering the lake from other sources than atmospheric inputs. The most likely local sources are argued to be mining activities (including fossil fuel burning during the production of iron) or Uppsala university hospital situated upstream of Lake Ekoln. However, there is a large uncertainty regarding the importance of these historical Hg sources for the lake.

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Le, Tran Thai. "Mineralogy of Lake Hotagen Sediments: Variations with Grain Size throughout Vertical Profile of a Sediment Core." Thesis, Umeå universitet, Kemiska institutionen, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-160376.

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Friedman, Richard M. "Geology and geochronometry of the eocene Tatla Lake metamorphic core complex, western edge of the intermontane belt, British Columbia." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/28780.

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The Tatla Lake Metamorphic Complex (TLMC) underlies 1000 km² on the western side of the Intermontane Belt (1MB) northeast of the Yalakom fault Three fault-bounded lithotectonic assemblages are recognized in the area studied: an amphibolite grade gneissic and migmatitic core, structurally overlain by a 1 to 2.5 + km-thick zone of amphibolite and greenschist grade mylonite and ductilely sheared metamorphic rocks, the ductilely sheared assemblage (DSA), which is in turn structurally overlain by weakly deformed to unstrained subgreenschist grade rocks of the upper plate which flank the TLMC on three sides. Structures in the gneissic core include a gneissic foliation and schistosity (Sic), which has been deformed by west to northwest-trending tight to isoclinal folds (F2c). Tectonic fabrics observed throughout the DSA which formed during Ds deformation include a gently dipping mylonitic foliation (Ss), containing a mineral elongation (stretching) lineation (Ls) which trends towards 280° ± 20°. Minor folds of variable trend (Fs), almost exclusively confined to DSA metasedimentary rocks, are interpreted as coeval with ductile shear. Vergence of these folds defines movement sense and direction of top towards 290° ± 20°. Kinematic indicators from DSA rocks which have not been deformed by syn-ductile shear folds indicate a top-to-the-west sense of shear while those deformed by Fs folds yield conflicting results, with a top-to-the-west sense predominating. The entire lower plate comprising the TLMC has been deformed by broad, upright, west to west-northwest trending, shallowly plunging map-scale folds (F3) during D3, which deform Sic and Ss surfaces. The steeply dipping, northwest-trending Yalakom fault truncates all units and structures of the TLMC. Gently to moderately dipping normal faults of Ds and post-D3 relative age are the southern and eastern boundaries between DSA upper plate rocks and 1MB lower plate rocks. U-Pb zircon dates from igneous arid meta- igneous rocks from the lower plate range from Late Jurassic (157 Ma) through Eocene (47 Ma). These dates bracket the timing of Cretaceous (107 Ma to 79 Ma, in the core) and Eocene (55 Ma to 47 Ma, in the DSA) deformation and metamorphism in the lower plate. Biotite and hornblende K-Ai dates of 53.4 Ma to 45.6 Ma for lower plate rocks are in sharp contrast to Jurassic dates from nearby upper plate rocks; they record the uplift and cooling of the TLMC. Whole rock initial ⁸⁷Sr/⁸⁶Sr ratios (and for most samples present-day values) of less ≤0.704 have been determined for igneous and meta-igneous rocks of the TLMC; such values are typical of magmatic arc rocks of the 1MB and Coast Plutonic Complex of B.C. Whole rock major and trace element chemistry of lower plate igneous and meta-igneous rocks indicate sub-alkaline, calcalkaline, volcanic arc affinities. Garnet-biotite temperatures (interpreted as Eocene in age), from pelitic schist in the southern part of the DSA increase from about 400 ± 50 to 650 ± 50 C with increasing structural depth. A GT-BI-QZ-Al₂SiO₅ pressure of 8 ± 3 kb has been calculated for one of these samples. A T-P of 650 ± 50 C and 5.3 ± 3 kb, calculated from inclusions and garnet cores in a small pelitic pendant in the northwest part of the DSA, reflects conditions during intrusion of the surrounding 71 ± 3 Ma igneous body. A pressure of 7.2 ± 1.4 kb, based on the total Al in hornblende, has been calculated for this body. Cretaceous ductile deformation in the gneissic core may be related to folding and thrusting which occured in high level rocks to the west and east of the field area. During Early Eocene time (55-47 Ma) the TLMC acquired the characteristics of a Cordilleran metamorphic core complex. Mylonites of the DSA were emplaced by faulting beneath weakly deformed, low metamorphic grade rocks of the upper plate. Synchronously, metamorphic rocks of the gneissic and migmatitic core of the TLMC were moved to higher crustal levels along the footwall of the DSA normal ductile shear zone. The formation of F3 folds and final uplift of the TLMC (47-35 Ma) is postulated to be the consequence of transpression related to later Eocene dextral motion along the Yalakom fault The TLMC has structural style and timing of deformation similar to metamorphic core complexes in southeastern B.C. Local and regional evidence is consistent with the formation of the TLMC in a regional extensional setting within a vigorous magmatic arc.
Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate

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Starr, Lindsay D. "Mercury pollution in an urban and suburban lacustrine system in Summit County, Ohio." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron149434254589456.

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Fordyce, Nicholas. "Muddy memories : environmental change at Hluhluwe Imfolozi Game Reserve, KwaZulu-Natal, South Africa - evidence from diatoms." Bachelor's thesis, University of Cape Town, 2010. http://hdl.handle.net/11427/26382.

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Diatoms are microscopic algae found in almost all aquatic environments. They are habitat specific and have silica frustules which preserve well in sediments. They have been used extensively to provide a multitude of palaeoecological data relating to pH, nutrient loads and water levels. Here, the diatoms in a lake sediment core from Hluhluwe-Imfolozi, South Africa, are analysed to show fluctuations in littoral to benthic taxa, and brackish to freshwater taxa as indicators of lake level changes over time. Changes in lake level act as a proxy for warm/dry or cold/wet periods over time. During the last 240 years lake levels have remained consistently low but nevertheless indicate four alternating periods of cold/wet and warm/dry climate. From c. A.D. 1770 (the last few decades of the Little Ice Age) to the c. A.D. 1840 the climate was cool and wet, but nonetheless gradually warmed up and became drier. From c. A.D. 1840 through to c. A.D. 1920 a there was a gradual increase in temperature and corresponding decrease in rainfall. Then, from c. A.D. 1920 till c. A.D. 1980 there was another colder, wetter period. Finally, very recently, from around c. A.D. 1980 till the present day, Hluhluwe-Imfolozi has experienced warmer, drier conditions once. Pollution-tolerant diatoms increase during the last 100 years and indicate eutrophication of the lake, a consequence of anthropogenic activity in the region. The diatom sequence from Phindiswene provides a high resolution climatic proxy for the critical period covering the latter stages of the Little Ice Age (LIA), post LIA warming, and recent increasing anthropogenic impacts.

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Yamada, Keitaro. "Reconstruction of high-resolution geological records and development of a method to identify sedimentary disturbance using Quaternary sedimentary cores from Beppu Bay and Lake Suigetsu, Japan." 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225413.

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Lundberg, Robert. "Preliminary Investigation into Quantitation of Pharmaceuticals in Lake Victoria Sediments : Development of a Method for Analysis of 11 Pharmaceuticals." Thesis, Linköpings universitet, Tema Miljöförändring, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-176660.

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Although Lake Victoria is threatened by pollution there is a lack of knowledge about pharmaceuticals contaminants drained into the lake from large cities bordering the lake. Hence, the purpose of this project was to develop, validate and apply a method for analysis of pharmaceutical compounds accumulating in the Lake Victoria sediments. A simple quantitative method for 11 pharmaceuticals combining accelerated solvent extraction, solid phase extraction, trimethylsilylation derivatization, and gas chromatography mass spectrometry was developed, partly validated, and applied to 18 surface sediments and a sediment core dated using the 210Pb method. The results showed the presence of the pharmaceuticals estriol, gemfibrozil, metoprolol, ketoprofen, naproxen, 17α-ethinylestradiol and estrone concentrated around the regions Napoleon Gulf and Thurston Bay with accumulation rates decreasing towards the top of the sediment core. Nonetheless, a randomness in the distribution of these compounds behooves a systematic assessment investigating not only the provenance of these compounds but also further investigations to errors meaning that this study should be treated as a preliminary investigation.

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Balch, Deborah P. "Quaternary Ostracode Paleoecology and Its Link to Climate Change in the Bonneville Basin: A Detailed Study of the Glad800 Core GSL00-4, Great Salt Lake, Utah." Thesis, The University of Arizona, 2003. http://hdl.handle.net/10150/249251.

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We report the results of a detailed paleoecological study of the Bonneville Basin covering the last ~240,000 years. Our study used fossil ostracodes and a sedimentological record obtained from the August 2000 GLAD800 drilling operation at the Great Salt Lake. We analyzed 125 samples, taken at ~1 meter intervals from core GSL00-4, for ostracodes and other paleoecologic and sedimentological indicators of environmental change. Multivariate analyses applied to the ostracode data indicate an alternation between three major environments at the core site over the cored interval. The environments fluctuated most often between shallow saline, open -water lake conditions (when the lake was high enough to inundate the core site) and salt or freshwater, spring -fed marsh (when the water level was at or lower than the core site). But occasionally, the core site was submerged by deep fresh water. Immediately following deep lake phases, crashes in lake level from rapid desiccation resulted in the deposition of thick evaporite units. These environmental changes are consistent with shoreline studies of regional lake level fluctuations, but provide considerable new detail on both the timing and environmental conditions associated with the various lake phases. Our age model (using dates obtained from ¹⁴C, U- series, tephra and biostratigraphic chronologies) allowed us to associate the core's record of regional paleohydrology to the marine oxygen isotope stages record of global climate change. The core contains high resolution, continuous records for the last three glacial/interglacial sequences. In each case we found that fresh open-water conditions (i.e. lake highstands) correspond with maximum glacial advances, except for the smaller, less intense OIS 4 glaciation, when the lake remained saline. Salt and freshwater marshes were dominant environments for most of the interglacials. However, throughout most of the Quaternary, this basin has contained a shallow, saline open-water lake.

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Gunnell, Nathan Vaun. "A Study of the Anthropogenic Impact in Farmington Bay through Isotopic and Elemental Analysis." BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/9208.

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The influence of human activity on surrounding environments is an important field of research. With respect to aquatic settings, lacustrine deposits provide excellent proxies of environmental change since the sediment accumulates at a relatively constant rate, recording environmental change. This study employs isotopic, mineral, and chemical records from Farmington Bay freeze cores, in particular δ13C, δ15N, and 210Pb isotopes as well as phosphorus level fluctuation and trace metal analysis. In particular, 210Pb isotopes permit estimation of the age of sediment with depth and δ15N, δ13C, and concentration of P provides a record of changing nutrient sources and level of eutrophication. Results from 210Pb isotopes have allowed ages to be assigned to depths along the core dating back roughly 100 years at 30 cm. At this depth, a dramatic shift in the δ15N isotope is observed. Initial δ15N levels indicated a nutrient source related to agriculture. However, beginning around 100 years ago, the δ15N shows the main nutrient source for the bay became wastewater which correlates to the completion of a sewage canal in 1911 that began routing wastewater directly into the bay. Results have also shown a large rise in phosphorus levels beginning around 1970 which may be due to the construction of the automobile causeway that isolated Farmington Bay from the rest of the Great Salt Lake.

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Gura, Colby J. "Characterization of Organisms in Vostok (Antarctica) Glacial, Basal, and Accretion Ice." Bowling Green State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1566486484767222.

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Baxstrom, Kelli W. "Climate and Vegetation Change in Late Pleistocene Central Appalachia: Evidence fromStalagmites and Lake Cores." Ohio University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1554978401327246.

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Berzins, Nicole Kay. "A PRACTICUM PROJECT RESEARCHING THE MICROBIAL COMMUNITY IN SEDIMENT CORES AND THE CURRENT CHEMICAL PARAMETERS OF LAKE QINGHAI, CHINA." Miami University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=miami1324745188.

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Hodelka, Bailee Nicole. "STRATIGRAPHY AND ORGANIC GEOCHEMISTRY REVEAL PATTERNS OF LATE QUATERNARY PALEO-PRODUCTIVITY AT MONO LAKE, CALIFORNIA." UKnowledge, 2018. https://uknowledge.uky.edu/ees_etds/58.

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Mono Lake (CA) is a hydrologically closed lacustrine basin well-known for its paleo-shorelines, which record fluctuations in water level for the last deglacial and late Holocene. Mono Lake is a sentinel of California’s water supply, situated in the rain shadow of the Sierra Nevada, a mountain range whose snowpack is a vital source of freshwater for urban and agricultural districts to the west and south. Recent droughts, floods, and wildfires show that California is threatened by climate change, but how these changes impact and get recorded by Mono Lake sediments remains poorly known. Here, we use a new radiocarbon-dated deepwater sediment core from Mono Lake to test the hypothesis that organic facies development is controlled by climate and limnological change. An integrated stratigraphic analysis of the core reveals seven lithostratigraphic units that track environmental changes from ~16-4 ka. When compared to available paleo-shoreline and shallow water core data, our results show that high amplitude lakelevel fluctuations of the late Pleistocene produce different patterns of sedimentation and organic enrichment than lower-amplitude water level changes of the early and middle Holocene. The results have implications for understanding patterns of paleo-production and hydroclimate change at Mono Lake.

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Cawley, Jon C. "A Re-Evaluation of Mountain Lake, Giles County, Virginia: Lake Origins, History and Environmental Systems." Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/29869.

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This project included the following goals: 1. To review and assess the geomorphology and lake morphometry of Mountain Lake, Giles County, Virginia with regard to its age and origin. This included production of an updated bathymetric map of Mountain Lake using Sonar imaging of the lake bottom. 2. To evaluate present trophic conditions in the lake waters. This analysis included the first-reported nutrient conditions for input streams to the lake and rainwater. 3. To collect representative "modern" bottom sediment samples and to analyze these sediment samples for sedimentological characteristics, diatoms , and terrestrial pollen. This analysis focussed on present environmental conditions in the lake, and the determination of modern diatom thanatocommunities. 4. To collect complete bottom sediment cores from the lake. Coring was done using a diver-assisted manual coring device designed specifically for this project. 5. To analyze Mountain Lake sediment cores for sedimentology, age determination, and temporal differences in sediment characteristics, diatoms and pollen. This analysis focussed on interpretation and documentation of environmental changes through the lake's history. Primary discharge from the lake presently occurs through a leaky subterranean pathway associated with the deepest, crevice-like portion of the lake. This discharge results in the crevice drain not filling shut with sediment despite its location within the lowest portion of the lake. The lake structure, crevice, and subterranean drain are associated with a regional lineation feature represented in part by the path of Salt Pond Drain and a small input stream ("I-4") to the lake. Initial damming was caused by downdrop of overlying rock. The damming is not complete, and the rate of discharge through time is controlled, in part, by regional tectonic events and by a balance of hydrologic conditions and sedimentation factors. The present lake is generally oligotrophic in nature, with phosphorus representing the major limiting nutrient. Rainfall presently represents the largest source of nutrient to the lake. Present diatom flora in Mountain Lake includes 66 individual taxa, representing 25 genera. Of these, 12 forms or species have not been reported in Virginia inland waters prior to this project. The diatoms reflect the oligotrophic and circumneutral nature of the lake. At least seven diatom thanatocommunities can be defined in the lake, based on taxa, delineated by depth and nutrient conditions. The ratio metric of planktonic to littoral diatoms can be used to estimate past water depths in the lake from bottom sediment. An orange clay layer at 5 cm from the modern sediment/water interface represents human intervention in lake history, namely the hotel and road building in the early 20th Century. The age of the lake is greater than 6000 years. Specific 14C from sediment produced dates of 1860 +100, 4220 +50 and 6160 +70 bp. Within this interval, at least 6 extended periods of low or empty lake level occurred (at approximately 100, 400, 900, 1200, 1800, and 4200 yrs bp). Several of these low intervals are likely to correspond with cool dry conditions co-incident with solar minima events. When the lake has been low or empty, it has tended to develop Sphagnum bog conditions with the low lake surrounded by open or wooded meadows. Terrestrial flora surrounding the lake appears to have remained relatively similar through 6100 years, although red spruce originally accompanied hemlock.
Ph. D.

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Grochocki, Julian Lucian. "Late Holocene Environmental Variability as Recorded in the Sediment of a Northeastern Ohio Kettle Lake." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1491558782637496.

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van, Blarcum Ronald A. "Anthropogenic Impacts as Revealed from Sediment Cores from Punderson Lake Ohio." Cleveland State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=csu1448536586.

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DeRosa, Edith, Lee Clark, and David Parsons. "Late Corn Variety Trial, Greenlee County - 1985." College of Agriculture, University of Arizona (Tucson, AZ), 1986. http://hdl.handle.net/10150/200574.

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Buck, Michael. "Modelling of the late phase of core degradation in light water reactors." [S.l. : s.n.], 2007. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-33311.

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Beierle, Brandon Dennis. "Early Holocene climate of southwestern Alberta, Canada, reconstructed from lake sediment cores." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq20816.pdf.

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Salat, Alexandre. "Tracking the History of Alberta Oil Sands Contaminants Using Lake Sediment Cores." Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/39749.

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Petroleum hydrocarbons are emitted into the environment via natural and anthropogenic activities. Once emitted, these hydrocarbons can be transported globally, persisting and accumulating in aquatic ecosystems. In the Alberta oil sands region (AOSR), mining activities have significantly altered and polluted the surrounding aquatic and terrestrial environments with heavy metals and various petroleum hydrocarbons including polycyclic aromatic hydrocarbons (PACs). Though PACs have been tracked through time using dated lake sediment cores, separating natural and anthropogenic PACs can be difficult. In the Peace Athabasca Delta (PAD) this task is especially difficult as this region has been receiving annual inputs of naturally eroded bitumen throughout history. Petroleum biomarkers are unique petrogenic compounds (i.e. derived from petroleum) which may provide a secondary proxy to track mining impacts. This thesis investigated the impacts of mining activities on the AOSR and the PAD using two different proxies, PAC and petroleum biomarkers. These two regions were compared to reference lakes to the south and northwest of the Athabasca oil sands formation, in order to provide a natural signal, with minimal oil sands mining contamination. Historically deposited PACs and petroleum biomarkers were analysed in radiometrically dated lake sediment cores from the AOSR and the PAD, Alberta. Sediment profiles in the AOSR (Saline Lake) showed increases in PAC fluxes for both alkylated and parent compounds coeval with mining activities. Alkylated PAC fluxes in reference lakes (Mariana Lake and BM11) increased at the height of oil sands development (1990s). PAD lakes showed no statistical increase in PAC flux through time due to high levels of naturally eroded bitumen entering the system. Parent PAC diagnostic ratios, however, showed clear shifts from pyrogenic (primarily wood burning) in pre-development sediments to petrogenically derived PACs in modern sediments, in both AOSR and PAD lakes, coeval with oil sands development. Petroleum biomarker diagnostic ratios in Saline Lake and PAD lakes remained stable through time, indicating a clear current and historical petroleum signal originating from the AOSR. Reference lakes (Mariana Lake and BM11) showed the greatest change in petroleum biomarkers. Historically, these lakes had signatures uncommon of petroleum sources, however, in recent years petroleum inputs from mining development were revealed by these petroleum biomarkers. This study compared the historical trends of several petroleum hydrocarbons in lake sediment to the historical emissions of these petroleum hydrocarbons from oil sands mining operations. Notably, we show the potential for petroleum biomarkers to trace petroleum hydrocarbon contamination in the environment.

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Kekonen, T. (Teija). "Environmental information from the Svalbard ice core for the past 800 years." Doctoral thesis, University of Oulu, 2006. http://urn.fi/urn:isbn:9514281853.

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Abstract Major water soluble ions (Cl-, NO3-, SO42-, CH3SO3-, Na+, K+, NH4+, Mg2+, Ca2+) were determined and the results interpreted from a 121 m long ice core drilled at the summit of the Lomonosovfonna dome, Svalbard. The core covers about the past 800 years. The reliability of anion chemistry for paleoenvironmental studies, and various insoluble particles were also investigated. The ice core studied in this Thesis is the first relatively deep ice core from the central Svalbard that has been analyzed and the results interpreted and published at high resolution for all major ions. One of the clearest features of the ion profiles is anthropogenic impact. SO42- and NO3- concentrations show significant increases by the mid-20th century with slight increases already at the end of the 19th century. In addition excess Cl- and NH4+ from anthropogenic sources are detected arriving after the mid-20th century. Anthropogenically derived SO42- and NO3- have different sources on Lomonosovfonna. NO3- is correlated with NH4+ and requires interpretation in terms of both natural and anthropogenic NH4NO3 sources. The ice core ionic load consists mostly of sea salt ions (Na+, Cl-, K+ and Mg2+). Water soluble Ca2+ are mostly terrestrial in origin. Ion balance together with the Na+/Cl- ratio shows considerable change about 1730 that is most probably due to Na2CO3 input to the ice cap before 1730. Marine biogenic CH3SO3- concentrations are high and stable during the Little Ice Age. CH3SO3- concentrations show a clear change in concentrations in 1920, that is the end of the Little Ice Age in Svalbard. Regardless of anthropogenic impact, marine biogenic SO42- is appreciable in total SO42- budget even in the 20th century. The Laki volcanic eruption in Iceland in 1783 is identified in the ice core as a volcanic tephra layer and high SO42- concentration and acidity peaks. These show that SO42- arrived to the Lomonosovfonna ice cap 6–12 months later than insoluble tephra and the SO42- aerosol caused a drop in temperature. The reliability of ice core ion chemistry analyses was estimated – for the first time in an ice core using two different analytical procedures on 500 adjacent samples from the same depth. Small-scale inhomogeneity in ion concentrations shows that information from ice core layers is representative of the regional environmental and suitable for paleoclimate studies.

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Satow, Christopher George. "The tephrostratigraphy of three, late quaternary, mediterranean marine cores." Thesis, University of London, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.589613.

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Isochronous tephra layers provide the potential for the precise correlation of environmental records and, in the case of tephra layers of known age, for the importation of age estimates into sequences that lack independent ages, or for which the chronology is equivocal. This PhD project explored this potential for three important late Quaternary core sequences from the Mediterranean Sea: ODP975, which lies close to the Balearics in the western Mediterranean; LC21 in the Aegean Sea, close to Crete; and OPD967 in the far eastern Mediterranean, close to Cyprus. Each sequence was investigated for the presence of visible volcanic ash and cryptotephra layers. Very low amounts of volcanic glass shards were found in the ODP975 sequence, while 15 discrete tephra layers were found in core LC21 and 5 in the ODP967 sequence. These were geochemically analysed for constituent major and trace element ratios using EPMA-WDS, LA-ICP-MS and SIMS micro-analytical methods. Correlations of tephra layers were based on graphical comparison of the resulting geochemical data-sets to a developing data-base of the representative glass chemical compositions of European proximal and distal tephra deposits. The results reveal evidence for 19 separate volcanic eruptions spanning the last 166 ka, originating from Campania, Pantelleria, Santorini, Yali/Nisyros and Kos, and possibly also from Central Anatolia and Iceland. 12 of these eruptions were previously unknown and thus are here characterised for the first time. The results add to the tephrostratigraphical record ofthe eastern Mediterranean, but also demonstrate that further progress requires some crucial procedural problems to be -addressed first. Several chronologically distinct tephra layers have identical elemental abundances, which complicates their applicability as robust stratigraphic and chronological markers. In addition, proximal and distal deposits derived from the same eruption phase may have different geochemical attributes, and some evidence suggests a degree of chemical heterogeneity between different distal components of the same eruption. If confirmed, these findings have serious implications for assigning distal tephra layers to a contemporaneous proximal deposit, and hence impede the reliable transfer of age estimates obtained from proximal layers to distal tephra and environmental records. These problems notwithstanding, the discovery of 12 previously unknown tephra layers demonstrates that the tephrostratigraphical record of the eastern Mediterranean is far from complete, and highlights the need for further research of this type. In particular, rhvolitic eruptions from Santorini are here shown to be more common than were previously thought. These findings therefore have importance for augmenting the history of volcanic activity in the region, especially as a contribution to understanding magma recharge rates and eruption frequencies and their relevance for developing more robust hazard assessments. 3

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Buckingham, Heather Marie. "Evolution and late stage deformation of the Himalayan metamorphic core, Kanchenjunga region, eastern Nepal." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/51563.

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Understanding the recent history of the Himalayan orogen not only helps elucidates near-surface convergence accommodation processes, but also provides constraints for geometric modification of earlier midcrustal structures. New ⁴⁰Ar/³⁹Ar and fission track (FT) data from the former Himalayan metamorphic core exposed in the Kanchenjunga region of eastern Nepal help constrain the evolution and low temperature uplift history of this portion of the orogen. Within the Lesser Himalayan Sequence (LHS), new apatite FT dates, combined with existing apatite and zircon FT dates from the region, define general younging trends towards the north - up structural section - of ~2.9 to 1.3 Ma and ~6.2 to 4.6 Ma respectively. There appears to be a significant jump in apatite FT dates from 1.3 Ma to 2.4 Ma that is coincident with an abrupt change in existing muscovite ⁴⁰Ar/³⁹Ar ages from the Proterozoic to the Cenozoic. This break in ages is consistent with the mapped location of the Main Central thrust (MCT) fault in the area. In structurally lower rocks in the Greater Himalayan Sequence (GHS), north of the MCT, trends in both muscovite ⁴⁰Ar/³⁹Ar and apatite FT continue to decrease to the north. These trends are interpreted to be consistent with the exhumation and uplift of these rocks associated with the growth of a duplex system within the LHS developed through underplating. Cooling rates across the mapped area indicate fast cooling in the GHS in early to mid Miocene, coupled with very slow cooling in the LHS. In the late Miocene to Pleistocene, cooling rates slow down in the GHS and increase in the LHS, such that they are similar. This is consistent with development of late-stage duplexing within the LHS at this time and the coupled exhumation of the GHS. Biotite ⁴⁰Ar/³⁹Ar dates may indicate a complex history across the study area. Some biotite dates (~24-16 Ma) are older than nearby ²³²Th-²⁰⁸Pb monazite melt crystallization dates (~18-16 Ma). Previous studies have attributed similar old biotite dates to excess argon. It is possible, however, the old biotite dates indicate crystallization along the retrograde path prior to final melt crystallization.
Irving K. Barber School of Arts and Sciences (Okanagan)
Earth and Environmental Sciences, Department of (Okanagan)
Graduate

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Stroup, Justin Sirico. "Glacial Lake Ojibway, lacustrine stratigraphy and implications for drainage." Cincinnati, Ohio : University of Cincinnati, 2009. http://rave.ohiolink.edu/etdc/view.cgi?acc_num=ucin1243303456.

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Thesis (M.S.)--University of Cincinnati, 2009.
Advisor: Thomas V. Lowell. Title from electronic thesis title page (viewed Aug. 18, 2009). Includes abstract. Keywords: Lake Ojibway; lacustrine; 8,200 year event; lake cores; XRF chemistry; stratigraphy; Laurentide; Ice proximal; varves; drainage; Canada. Includes bibliographical references.

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Zirker, Kelly Ann Hill. "Intrasentential vs. Intersentential Code Switching in Early and Late Bilinguals." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1885.pdf.

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Kaspari, Susan. "Late Holocene Asian Climate and Environmental Variability as Inferred from a Mt. Everest Ice Core." Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/KaspariS2007.pdf.

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Vitorino, Tatiana Mendes. "A closer look at brazilwood and its lake pigments." Master's thesis, Faculdade de Ciências e Tecnologia, 2012. http://hdl.handle.net/10362/10179.

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Dissertação para obtenção do Grau de Mestre em Mestrado em Conservação e Restauro, especialização em Ciências da Conservação
Brazilwood is a soluble redwood that was used as source of organic dye and for lake pigments. It was widely applied in medieval times to colour textiles and in the form of pigment for manuscript illumination and, although it is relatively unstable, it is still found in the 19th oil palette. However, this colorant has received little attention. In this sense, the present work aims to contribute knowledge on the characterisation of brazilwood and its lake pigments. The flavonoid brazilein is the red chromophore that can be extracted from the brazilwood tree. To study with more detail its behaviour, the molecule was isolated from brazilwood scrapes. As confirmed by NMR and HPLC-DAD, a high purity compound was obtained (for which a pKa1 of 7 was determined) and a pure brazilein-Al3+ complex was produced. Characterisation with UV-Vis spectroscopy and μ-spectrofluorimetry revealed that in its acidic form, the chromophore presents absorption, excitation and emission maxima at 446, 475 and 536 nm, respectively, and at 540, 548 and 560 nm when deprotonated. When complexed with Al3+ these values are changed to 510, 520 and 585 nm. Brazilwood lake reconstructions with as much historical accuracy as possible were also prepared based on recipes from the 15th century documentary text Livro de como se fazem as cores and the Winsor & Newton 19th century archive. This led to a greater understanding of the manufacture of the lakes and its evolution through time. Furthermore, in order to investigate the best strategy to characterise such pigments and paints, and to provide reference samples, the lakes produced and applied as temperas were then analysed by colorimetry, FTIR, SEM-EDS, FORS and UV-Vis μ-spectrofluorimetry. Despite some differences exist between the two sources, mainly with respect to the dye extraction method, both are guided by the same principles and are constructed in order that the same final pH, adequate for pigment precipitation, is obtained. In particular, the 15th century Livro de como se fazem as cores, so distant in time, allowed for the successful preparation of brazilwood lake pigments, which can be obtained in a variety of different hues from light pink to dark red and purple. Concerning the analysis carried out, FTIR was essential to characterise extenders, while FORS spectra (λabs 560 nm) and μ-spectrofluorimetry (λex 553 nm for excitation and λem 585-90 nm for emission) data were very consistent and fundamental to identify the brazilwood chromophore. These three techniques were essential and complementary in the characterisation of the paints produced. Medieval reconstructions were compared with pink and red colours of illuminations found in three French books of hours (Palácio Nacional de Mafra, Portugal) from the 15th century. Good correlation between FTIR, FORS and μ-spectrofluorimetry spectra of the reconstructions and historic samples suggest that the illuminations colours were prepared with brazilwood lakes.

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Cedillo, Paula. "Hydrodynamic modeling of the Green Bay of Lake Michigan using the environmental fluid dynamics code." Thesis, The University of Wisconsin - Milwaukee, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=1606696.

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In this project we created a hydrodynamic model of the Lower Green Bay of Lake Michigan in Wisconsin, United States using the Visual Environmental Fluid Dynamics Code (EFDC). The model includes four tributary rivers to Lower Green Bay as well as the open boundary flow conditions at Chambers Island. This case study is used to: 1) compare the results obtained with a previous study of Lower Green Bay to validate the creation of the model 2) examine the hydrodynamics of the bay, and 3) create a framework for future studies at Lower Green Bay. The Geographic Information used to build the Grid was obtained from the NOAA web site. Meteorological and flow information was obtained from the National Weather Service and USGS web sites, respectively. It was necessary to create a new model grid as a platform for future studies of Lower Green Bay, and the Visual EFDC 1.2 code was a useful tool in the development of the grid. However, some limitations in the code made the creation of the grid a challenge. In this project, we summarize the process used to overcome challenges in creating a correct grid, and analyze the hydrodynamic results of the model simulation for the period between June and October 2011. Overall, we conclude that the model reproduces field data reasonably well, and a correct modeling framework for hydrodynamic modeling of Lower Green Bay was created.

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Reboul, Guillaume. "Metabarcoding and metagenomic approaches to decipher microbial communities in suboxic environments Microbial eukaryotes in the suboxic chemosyn- thetic ecosystem of Movile Cave, Romania Hyper- diverse archaea near life limits at the polyextreme geothermal Dallol area Performance of the melting seawater-ice elution method on the metabarcoding characterization of benthic protist communities Core microbial communities of lacustrine microbialites sampled along an alkalinity gradient Environmental drivers of plankton protist communities along latitudinal and vertical gradients in the oldest and deepest freshwater lake Ancient Adaptive Lateral Gene Transfers in the Symbiotic Opalina-Blastocystis Stramenopile Lineage Marine signature taxa and microbial community stability along latitudinal and vertical gradients in sediments of the deepest freshwater lake." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASL041.

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L’écologie microbienne concerne l’étude des microorganismes et de leurs interactions biotiques et abiotiques dans un écosystème donné. Ces vingt dernières années, l’avancement des techniques moléculaires pour analyser la diversité microbienne et, notamment, les nouvelles technologies de séquençages (NGS) ont permis de surmonter les limitations associées aux approches traditionnelles basées sur la culture et la microscopie. Ces approches moléculaires ont conduit à une accumulation des données de diversité microbienne et de potentiel métabolique dans des communautés microbiennes des écosystèmes variés.Cependant, ces efforts ont été principalement appliqués sur des environnements facilement accessibles ou liés à l’humain, comme le plancton (marin principalement) et la flore intestinale. Néanmoins, ceci a conduit à une très forte augmentation de données environnementales et au développement de la bioinformatique par le biais de nombreux outils. Parmi les environnements délaissés des études, les environnements faibles en oxygène sont probablement également porteurs de nouveautés phylogénique ou métaboliques.Afin de palier à cela, nous avons choisi d’explorer deux environnements suboxiques relativement peu étudiés : la cave Movile (Roumanie) et les sédiments du lac Baikal (Sibérie, Russie). Notre but étant de montrer les diversités phylogénétiques et fonctionnelles des microbes de ces biotopes.Pour cela, j’ai d'abord développé un pipeline d’analyse de données métabarcoding (petite sous-unités ribosomique). Ensuite, j’ai appliqué cet outil sur des données de métabarcoding de protistes provenant d’échantillons d’eau et de tapis microbiens de la cave de Movile, un écosystème chemosynthétique pratiquement fermé. Nous avons montré que la diversité des protistes de la cave s’étendait à quasiment tous les grands groupes eucaryotes et provenait à la fois d’origine d’eaux douces et marines. De plus, la plupart ont été affiliées à des groupes d’organismes typiquement anaérobies, ce qui est concordant avec les paramètres abiotiques de la cave. Écologiquement, ces protistes sont des prédateurs mais aussi vraisemblablement des partenaires symbiotiques avec des espèces procaryotes de la cave.Dans une deuxième étude, j’ai eu l’opportunité d’appliquer ce pipeline de métabarcoding sur des données procaryotes et eucaryotes provenant des couches superficielles des sédiments du lac d’eau douce Baikal. Comme attendu, les communautés microbiennes dans ces sédiments sont particulièrement diverses et relativement enrichis en archées. Nous avons aussi pu mettre en évidence des lignées que l’on pensait exclusivement marines dans ces sédiments. Ces lignées sont probablement planctoniques mais s’accumulent au fond par sédimentation. Enfin, les échantillons ont été prélevés dans le but de tester les influences de la profondeur, du bassin et de la latitude sur les communautés. Aucune d’elles ne s’est révélée significative.Dans une troisième étude, j'ai utilisé une approche métagénomique afin de révéler les acteurs écologiquement majeurs dans les sédiments, leurs rôles et de reconstruire leurs génomes. Cela nous a permis notamment de mettre en évidence le rôle primordial des Thaumarchaeota dans le cycle de l’azote et la production primaire de molécules de carbone. Les chloroflexi et les protéobacteries ont aussi un rôle important dans la surface des sédiments du lac Baikal. Ce travail de thèse participe à la connaissance globale de la diversité microbienne sur la planète en mettant en lumière des environnements peu étudiés. De plus, l’étude de la surface des sédiments du lac Baikal apporte de nouvelles données sur le sujet de la transition eau douces/eau marines des microbes. Enfin, la métagénomique a permis de révéler le cycle des nutriments et les microorganismes y participant dans ces échantillons de sédiment. En résumé, ce travail vient mettre en lumière l’écologie microbienne d’écosystèmes suboxiques, notamment la surface des sédiments du lac Baikal
Microbial ecology is the science of micro-organisms and their biotic and abiotic interactions in a given ecosystem. As technology has advanced, molecular techniques have been widely used to overcome the limitations of classical approaches such as culturing and microscopy. Indeed, the development of Next Generation Sequencing (NGS) technologies in the past twenty years has largely helped to unravel the phylogenetic diversity and functional potential of microbial communities across ecosystems.Nonetheless, most of the environments studied through these techniques concentrated on relatively easily accessible, tractable and host-related ecosystems such as plankton (especially in marine ecosystems), soils and gut microbiomes. This has contributed to the rapid accumulation of a wealth of environmental diversity and metagenomic data along with advances in bioinformatics leading to the development of myriads of tools. Oxygen-depleted environments and especially their microbial eukaryote components are less studied and may lead to future phylogenetic and metabolic discoveries.In order to address this, we conducted analyses on two poorly studied suboxic ecosystems: Movile Cave (Romania) and lake Baikal sediments (Siberia, Russia). In this task, we aimed at unveiling the taxonomic and functional diversity of microorganims in these environments.To do so, I first evaluated the available bioinformatics tools and implemented a bioinformatics pipeline for 16S/18S rRNA gene-based metabarcoding analysis, making reasoned methodological choices. Then, as a case study, I carried out metabarcoding analyses of the water and floating microbial mats found in Movile Cave in order to investigate its protist diversity. Our study showed that Movile Cave, a sealed off chemosynthetic ecosystem, harbored a substantial protist diversity with species spanning most of the major eukaryotic super groups. The majority if these protists were related to species of freshwater and marine origins. Most of them were putatively anaerobic, in line with the cave environment, and suggesting that in addition to their predatory role, they might participate in prokaryote-protist symbioses.In a second study, I applied my metabarcoding pipeline to explore unique and relatively unexplored environment of Lake Baikal sediments. I first applied a metabarcoding approach using 16S and 18S rRNA genes to describe prokaryotic as well as protist diversity. Overall, the communities within these ecosystems were very diverse and enriched in ammonia-oxidizing Thaumarchaeota. We also identified several typical marine taxa which are likely planktonic but accumulate in sediments. Finally, our sampling plan allowed us to test whether differences across depth, basin or latitude affected microbial community structure. Our results showed that the composition of sediment microbial communities remained relatively stable across the samples regardless of depth or latitude.In a third study, we applied metagenomics to study the metabolic potential of communities associated to Baikal sediments and to reconstruct metagenome-assembled genomes (MAGs) of dominant organisms. This revealed the considerable ecological importance of Thaumarchaeota lineages in lake Baikal sediments, which were found to be the major autotrophic phyla and also very implicated in the nitrogen cycle. Chloroflexi and Proteobacteria-related species also appeared ecologically important.This PhD thesis reveals the taxonomic diversity of poorly studied suboxic ecosystems and therefore contributes to our knowledge of microbial diversity on Earth. Additionally, the analyses of surface sediment samples in lake Baikal adds new light on freshwater-marine transitions. The metagenomic analyses reported here allowed us to postulate a model of nutrient cycle carried out by microorganismsin these sediments. Overall, this work sheds light on the microbial ecology of oxygen-depleted environments, and most notably lake Baikal surface sediments

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Buck, Michael [Verfasser]. "Modelling of the late phase of core degradation in light water reactors / vorgelegt von Michael Buck." Stuttgart : IKE, 2007. http://d-nb.info/997050047/34.

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Díaz, Viviana Díaz. "Late cretaceous SR isotopic and sequence stratigraphy of the Dixon Core, Outer Coastal Plain, North Carolina." View electronic thesis (PDF), 2009. http://dl.uncw.edu/etd/2009-1/rp/diazv/vivianadiaz.pdf.

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Claypoole, Micah N. "Mineral Ridge| A Late Cretaceous Orogenic Gold System in the Miocene Silver Peak-Lone Mountain Metamorphic Core Complex." Thesis, University of Nevada, Reno, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10821834.

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Gold deposits in rocks of the Silver Peak metamorphic core complex in west-central Nevada are contained in highly deformed, sheeted milky quartz veins that cut Neoproterozoic metasedimentary rocks and Cretaceous peraluminous granite and migmatite. Gold production at Mineral Ridge since discovery in 1864 has been approximately 1 million oz. Gold-bearing veins are concentrated in a major low-angle ductile shear system active during the Late Cretaceous. However, a broadly coincident brittle detachment cuts the ductile shear, separating metasedimentary and foliated granitic rocks from overlying non-metamorphosed Cambrian carbonates and Cenozoic volcanics. The Mineral Ridge biotite-muscovite granite pluton bounds the ductile shear along its roof, defining a wedge of prospective metamorphic rocks generally <50-m-thick. Zones of intense shearing generally correspond to highest vein density and therefore, gold grades, and such zones are overprinted with strong but narrowly defined quartz-sericite-pyrite-carbonate alteration. Vein boudins are subparallel to the strong planar to anastomosing shear fabric best developed over 1-10 meter thicknesses at contacts between muscovite schist and/or marble, and foliated granite. Goldbearing veins contain Au:Ag of ≥4, zoned base metals, low As, Sb, and Hg, but high Bi, the latter correlating with gold.

Vein-bearing granites at Mineral Ridge yield U/Pb zircon ages of 91.7+/-0.3 Ma and 89.9+/-0.5 Ma and likely derive from crustal melts during peak metamorphism. Hydrothermal monazite in goldbearing quartz veins yielded a U/Pb age of 76.0+/-1.8 Ma, indicating veins are unrelated to granites and formed during retrograde greenschist conditions. Previous cooling ages on mica in granites of ∼42 and 53 Ma further define the cooling path to ∼300°C. Mineral Ridge is interpreted as an orogenic gold system associated with a brittle-ductile shear that formed at depths as much as 11-20 km during the waning stages of Late Cretaceous Sevier contraction. Major exhumation occurred in the late Miocene in association with detachment and transtension in the Walker Lane deformation belt.

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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.

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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.

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Kirchgeorg, Torben [Verfasser], and Ralf [Akademischer Betreuer] Ebinghaus. "Specific Molecular Markers in Lake Sediment Cores for Biomass Burning Reconstruction during the Holocene / Torben Kirchgeorg. Betreuer: Ralf Ebinghaus." Lüneburg : Universitätsbibliothek der Leuphana Universität Lüneburg, 2015. http://d-nb.info/1077913729/34.

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Neil, Karen. "Ecosystem Responses to Holocene Climate Variability Through the Analysis of High-resolution Lake Sediment Cores from Southwestern Québec, Canada." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/38120.

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Lake biotic responses to natural climate variability, fire disturbances, and human impacts over the Holocene were studied at two proximate sites in southwestern Québec. Sediments from Lac Noir and Lac Brûlé had annually deposited laminations (varves), enabling for the precise dating of continuous time-series and high-resolution analysis of subfossil diatom assemblages. The Lac Noir (45°46’31”N, 75°8’23”W, 176 m a.s.l.) record spanned ~11000 years of the Holocene. Stratigraphic changes in diatom assemblages of the lake could be divided into early, mid-, and late periods, broadly paralleling Milankovitch-scale climate intervals and vegetation changes inferred from regional palynological records. The early Holocene (11.1-8.0 ka) climate was cooler and dry, vegetation in the region was comprised of Picea-dominated woodlands, and the lake diatom flora included primarily benthic taxa. Warming in the mid-Holocene (8.0-3.6 ka) allowed for stabilization of soils and forests in the catchment, stronger thermal stratification in the lake, and resultant increases in oligo-mesotrophic diatom taxa such as Discostella stelligera. During the late Holocene (3.6 ka to present), an increase in the abundance of deciduous trees (e.g. Betula and Alnus) in response to cooling led to nutrient-enrichment and higher overall lake productivity. The record from Lac Brûlé (45°43’09”N, 75°26’32”W, 270 m a.s.l.) encompassed the last ~1200 years of the late Holocene. Generalized additive models (GAM) revealed a tight coupling between diatoms and catchment-mediated processes (e.g. vegetation and disturbances), which were closely aligned with climate variations. During the Medieval Warm Period (800-1300 CE), pollen-based inferences of warmer summer temperatures were associated with high abundances of Cyclotella bodanica var. intermedia and Cyclotella rossii; this signalled oligotrophic lake conditions and prolonged thermal stratification. The onset of the Little Ice Age (1450-1850 CE) marked a cooling in the region, and a decline in Tabellaria flocculosa str. IIIp indicated increased nutrient loading from the catchment area. Situated less than 300m from Lac Brûlé are remnants of the Wallingford-Back Mine, which ran from 1924-1972 CE; activities at the mine resulted in local changes to nutrient availability and primary productivity at this site. In previous studies of both Lac Noir and Lac Brûlé, pollen records had indicated overall similarities in the vegetation histories in response to climate variability during the late Holocene. Diatom assemblages were influenced by individual lake conditions and were thus unique to each site; nevertheless, they were closely linked with local and regional patterns of vegetation composition. A main point of difference in the paleo-records from both lakes was attributed to a local fire in the Lac Brûlé catchment at 1345 CE, which caused an early decline in hemlock (Tsuga). The decrease in hemlock was seen at Lac Noir only centuries later, and diatoms in each lake responded according to vegetation changes within their own respective catchments. This research shows that high-resolution sampling of lake sediments is able to detect diatom responses to both long-term and abrupt changes in the environment. Individual sites show similarly timed responses of other proxy-indicators, such as pollen and cladocera, to climate and land-use changes. However, distinct differences in the aquatic biota of well-dated proximate sites can be used to identify influences of regional climate variations, which are sometimes masked by localized, non-climatic processes.

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Foulds, Chantal M. (Chantal Marguerite). "Field testing of five legume forages as interseedings in early and late cole crops." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59942.

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Experimental plots were overlaid on commercial fields of broccoli (Brassica oleraceae L. var. Italica) and cauliflower (Brassica oleraceae L. var. botrytis L.) to evaluate legume species as interseedings in vegetable production. White clover (Trifolium repens L.), red clover (T. pratense L.), yellow sweet clover (Melilotus officinalis L.), hairy vetch (Vicia villosa Roth.) and crimson clover (T. incarnatum L.) were seeded 4-5 weeks after an early planting of broccoli and a late planting of cauliflower. Crop yields, forage biomass, weed biomass and percent fall ground cover were recorded.
A dry year coupled with difficulties in applying the treatments resulted in low forage biomass. Hairy vetch yielded the most within the early broccoli planting system. High rainfall the next year resulted in high biomass yields. Over the two year study, hairy vetch and crimson clover emerged as the two most productive species. Significant effects on fall weed biomass were observed with broccoli in the second year of the study, where interseeded plots reduced weed populations by at least 66%. No evidence was seen of weed suppression by interseedings prior to harvest. Crop yields were not affected by interseedings. All interseeded treatments provided the minimum of 30% ground cover required to help reduce erosion.

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Almeida, André Filipe de Oliveira. "Comportamento de lajes alveoladas sujeitas a cargas pontuais – análise numérica da distribuição de esforços." Master's thesis, FCT - UNL, 2009. http://hdl.handle.net/10362/3615.

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Dissertação para obtenção do Grau de Mestre em Engenharia Civil – Ramo de Estruturas e Geotecnia pela Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa
Esta dissertação tem como objectivo aprofundar o conhecimento sobre o comportamento de lajes alveolares sujeitas a cargas concentradas e a forma como o esforço transverso se distribui pelas nervuras. Para o efeito, utilizaram-se modelos numéricos com elementos finitos de sólido para caracterizar as propriedades mecânicas destes elementos. Conhecendo estas grandezas, modelaram-se painéis de laje alveolar em elementos finitos de laje que foram submetidos a diversas situações de carga, nos quais se fizeram variar as dimensões do vão dos painéis de laje, o número de painéis justapostos e o tipo painel de laje alveolar. Com a análise dos resultados destes procedimentos, tiraram-se conclusões quanto à influência da variação de cada um dos parâmetros acima enumerados na distribuição do esforço transverso pelas nervuras, assim como a contribuição da fendilhação longitudinal nas juntas entre painéis e no alvéolo adjacente à secção carregada, na distribuição de esforços. Para concluir, será apresentada uma proposta para calcular o esforço transverso actuante máximo para que, comparando com o esforço transverso resistente, possa ser verificada a segurança das lajes alveolares ao punçoamento.

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Camillo, Carolina Alvares. "Continuidade de painéis de laje alveolar em edifícios." Universidade Federal de São Carlos, 2012. https://repositorio.ufscar.br/handle/ufscar/4679.

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Made available in DSpace on 2016-06-02T20:09:17Z (GMT). No. of bitstreams: 1 4849.pdf: 4074086 bytes, checksum: 7e455ae6da74787b0840ce6589520e40 (MD5) Previous issue date: 2012-12-10
The floors consist of hollow core slabs are being increasingly used in Brazil, because it can overcome large spans, have a low self-weight, allow fast assembly, require no shoring in many situations and are more economical than other solutions. These floors are normally designed for ease of implementation, so that the slabs act as simply supported, without continuity. This work presents a roadmap of calculation and verification based on known theoretical models and tests already carried out considering that the hollow core slabs of pavement work as continuous. This continuity is made by adding passive reinforcement in the topping region. The calculation procedures are also detailed for the situations in which there are alternate accidental actions, as well as the situation in which there are concentrated mobile loads acting on the floor. Numerical examples comparative considering continuity with the situation simply supported show what can be achieved: the active reinforcement economy, increasing the value of accidental load and checks excessive deformation that is not checked on a system simply supported. Some situations are also pointed in which the consideration of continuity fails to bring great advantage. In all the examples developed are shown the details required to perform continuity. Every calculation methodology is based on Brazilian codes and should be noted that the calculations are done considering the simultaneous loss of prestressing. At the end of the work are proposed studies that may be performed to improve understanding of the behavior of pavements with continuous hollow core slabs.
Os pavimentos formados por laje alveolar estão sendo cada vez mais utilizados no Brasil, porque podem vencer grandes vãos, ter um baixo peso próprio, permitirem rapidez de montagem, não necessitam de escoramento e em diversas situações são mais econômicos do que outras soluções. Tais pavimentos são normalmente projetados, por facilidade de execução, para que as lajes funcionem como simplesmente apoiadas, sem continuidade. Apresenta-se neste trabalho um roteiro de cálculo e verificações baseados em modelos teóricos conhecidos e ensaios já realizados considerando que as lajes alveolares do pavimento funcionam como contínuas. Esta continuidade é feita através da adição de armadura passiva na capa das lajes. Detalham-se os procedimentos de cálculo também para as situações em que existem ações acidentais alternadas, assim como para a situação em que há cargas concentradas móveis atuantes no pavimento. Exemplos numéricos comparativos considerando a continuidade com a situação simplesmente apoiada mostram, que é possível alcançar: economia na armadura longitudinal ativa, aumento do valor de carga acidental atuante e atender verificações de deformação excessiva, não atendidas em um sistema simplesmente apoiado. Aponta-se também em quais situações a consideração da continuidade não chega a trazer grande vantagem. Em todos os exemplos desenvolvidos são mostrados os detalhes necessários para executar a continuidade. Toda a metodologia de cálculo é baseada nas instruções das normas Brasileiras e salienta-se que os cálculos são feitos considerando-se as perdas de protensão simultâneas. No final do trabalho são propostos estudos que podem ser realizados para melhorar o entendimento do comportamento de pavimentos contínuos com lajes alveolares.

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Hoare, Mary-Jo. "A comparison of the pollution record of South Merseyside from sediment cores taken from the estuary and a small lake." Thesis, University of Liverpool, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.569449.

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The ability to assess the contamination of sediments in estuaries and lakes is extremely important. This is because of various factors, both natural (tidal action, chemical remobilisation) and anthropogenic (e.g. building work), that lead to the disturbance of the sediment can result in the remobilisation or resuspension of the pollutants and, if high levels of pollutants are present in ,a region, they can be responsible for a number of health impacts on the local population. The use of sediment cores to investigate the pollution levels in the sediment is a relatively easy method of assessing contamination. The main aims of this study were to investigate pollution in saltmarsh, intertidal and lake sediment cores taken from the South Liverpool area and to attempt to distinguish different pollutant transport pathways between cores. This was done using sediment cores taken from a saltmarsh, intertidal area and lake in ,. South Merseyside and measuring the heavy metal and persistent organic pollutant (P AH and PCB) content using a variety of methods including; X-Ray Fluorescence, Environmental Magnetism, Gas ChromatographylMass Spectrometry and Flame Atomic Absorption Spectrometry. The results showed that, although the pollution input to the region has reduced over the last 30 years, there are still high levels of certain chemicals (including lead, mercury and PCBs) in the environment. The concentrations of the main pollutants (Pb, Zn, Hg, Cd, PCBs and PARs) are above guideline levels that are considered dangerous to aquatic organisms, however with the exception of Cd at Speke, none of the metals are present at a concentration that would be considered dangerous to human health. The main source of pollution to the saltmarsh is aquatic, whilst the main input to the lake core is from atmospheric deposition. From the data acquired for this project it would appear that the core from the Speke Hall Lake location provides a more accurate record of the pollution history of the area than those from the more dynamic saltmarsh environment.

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Susser, Jessica R. "Can we reduce phosphorus runoff into Lake Erie by stimulating soil biota?" University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1515756009087471.

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Råhlander, Moa. "How Beads come Together : Late Iron Age glass beads as past possessions and present sources." Thesis, Stockholms universitet, Institutionen för arkeologi och antikens kultur, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-185146.

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This study aims to demonstrate the potential for understanding first millennium glass beads not as individual representatives of types, but as collections of objects brought together and curated by owners. It uses the author’s experience as a skilled bead maker to investigate processes of bead production and mechanics of bead collection current in Scandinavia and Anglo-Saxon England in the period of 6th to 9th century AD. In the study the bead collections of seven graves are examined from the perspective of their production techniques, materials, and damage from wear and cremation. The results point to beads being acquired in different numbers and often worn for long periods of time before being buried.

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King, Leighton R. "The Response of Utah Lake's Plant and Algal Community Structure to Cultural Eutrophication." DigitalCommons@USU, 2019. https://digitalcommons.usu.edu/etd/7631.

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Human activities have long had a negative impact on the water quality of freshwater lakes around the world. Utah Lake, located in north-central Utah, has been a subject of such impacts, as the lake experiences recurrent harmful algal blooms during the summer months. Lake warnings and closures have made the public increasingly aware of the ecological and economic impact of these blooms. The objectives of this study were to: 1) compare historical and present-day water quality and ecosystem conditions using environmental data contained in sediment cores, 2) identify whether, and when, Utah Lake transitioned from clearwater to turbid conditions, and 3) incorporate historically-validated lake plant community structure models into establishing forward-thinking lake management targets. The first two objectives will guide lake remediation efforts by providing insight into where lake managers should set our water quality goals and help identify the main driver(s) of eutrophication in Utah Lake. Environmental data from sediment cores indicate a transition in the lake’s recent history, marking a shift to greater phytoplankton dominance, which I attribute to the introduction of invasive common carp around 1881. The third objective provides management and restoration efforts with the water clarity requirements for returning the lake to its historical ecological state.

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Schultz, Lynn L. "Agricultural Land Use, Watershed Characteristics, and Hydrological Forces Contributing to the Impairment of a Shallow Lake in the Western Corn Belt Ecoregion." Thesis, Minnesota State University, Mankato, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10254675.

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The Lake Titlow watershed (approximately 35,000 acres) in south-central Minnesota is part of the Minnesota River Basin. The lake is listed in the draft 2010 Clean Water Act Section 303d for nutrient pollution, eutrophication, and biological indicators for impairment of aquatic life and recreational use. Over 90 percent of pre-settlement wetlands are currently drained for agricultural land use. The Lake Titlow watershed is over 80 percent row crops and land use is implicated as a primary cause of impairment in the lake.

Water samples were collected from the Lake Titlow tributaries McLeod-Sibley Judicial Ditch Number 18 (JD18), Sibley County Ditch Number 18 (CD18), and Ditch 250 (D250) during 2009 and 2010 and were analyzed for total suspended solids (TSS), total phosphorus (TP), and nitrate-nitrite nitrogen (NOx). Investigative methods included continuous recording stream stage and through the use of rating curves, discharge. Runoff, sediment loads, and nutrient loads were then determined from the field data. Four rain gauges collected precipitation each year and were used to assess the impact of precipitation on runoff and loading. Four characteristic precipitation events were selected for each of the calendar years 2009 and 2010 to estimate the loads of sediment and nutrients to the lake and more fully understand the specific roles that land use, hydrologic soil group, slope, and precipitation play with regard to causing sediment and nutrient loading in the lake.

Results indicate runoff and loads are significant and highly variable by position within the watershed, areas referred to herein as subsheds. The row crop land use, soils characteristics, and precipitation do contribute to overall runoff and loads; however, they do not control subshed variability. Although the low-sloping land surfaces of the watershed should not contribute to overall runoff and loads, results indicate that subtle slope changes in the JD18Lo and CD18Lo subsheds could contribute to the variability of loads seen in these portions of the watershed.

The location and type of best management practices to implement is debatable because the results of this study indicate that large runoffs and loads could originate within any given subshed during any given rainstorm event. This study was unable to precisely identify the root cause of the variability in subshed runoff and loading. Therefore, it is suggested to look at other factors (e.g., antecedent soil moisture, rainfall intensity, mass wasting, etc.) to explain the subshed variability in the sediment and nutrient loading in future studies of this lakeshed.

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Sunderlage, Brent. "LATE APPLICATION NITROGEN ON CORN IN SOUTHERN ILLINOIS AND SOIL PROPERTIES AFFECTING AMMONIA VOLATILIZATION FROM UREA FERTILIZER." OpenSIUC, 2017. https://opensiuc.lib.siu.edu/theses/2154.

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AN ABSTRACT OF THE THESIS OF BRENT C. SUNDERLAGE, for the Master of Science degree in Plant, Soil, and Agricultural Systems, presented on March 8, 2017, at Southern Illinois University Carbondale. TITLE: LATE APPLICATION NITROGEN ON CORN IN SOUTHERN ILLINOIS AND SOIL PROPERTIES AFFECTING AMMONIA VOLATILIZATION FROM UREA FERTILIZER MAJOR PROFESSOR: Dr. Rachel L. Cook In corn (Zea mays L.) production systems, typical nitrogen fertilization occurs either before planting or after crop emergence, as late as the V6 stage. Since the majority of nitrogen uptake does not occur until V10 through R1, delaying nitrogen fertilization until V10 may reduce potential for early season soil N transformations and losses, while sustaining crop yields. A two-year study, conducted across three southern Illinois locations, evaluated the effects of various late sidedress nitrogen applications and enhanced efficiency fertilizers on corn yield and residual mineral soil N. The various nitrogen treatments compared: rates from 0-224 kg N ha-1; sources of urea and 32% UAN, with and without urease inhibitors 0.09% N-(n-butyl) thiophosphoric triamide (NBPT) as Agrotain® Ultra (AT) and 0.06% NBPT + 0.02% N-(n-propyl) thiophosphoric triamide (NPPT) as Limus® (L), and polymer-coated urea (ESN®); application timings at planting, V6, V10, and VT; placement either dribble applied, broadcasted, or injected. Across sites and years, late (V10) nitrogen split applications generally resulted in corn yields greater than or equal to the same total nitrogen rate applied at planting. Most late N treatment differences varied between sites and years, but 56 kg N ha-1 as broadcasted UAN at planting with 112 kg N ha-1 as broadcasted urea, either with or without AT or L at V10 were on average highest yielding treatments among sites in both years, with 16% greater yield than 168 kg N ha-1 as broadcasted UAN at planting. Urease inhibitors did not enhance yield in most instances, likely due to sufficient incorporating rainfall shortly after application. The effects of urease inhibitors used with late-application nitrogen on corn yield and actual ammonia volatilization remained ambiguous. Residual soil mineral nitrogen concentrations between 0-30 cm after harvest in the late nitrogen treatments did not elicit water quality concerns. Furthermore, ammonia volatilization from surface applied urea is controlled by many interrelated soil properties as well as environmental conditions. However, conclusions about the influence of soil properties on ammonia volatilization differ according to geographies and are not well established across a wide range of soil types. A laboratory soil incubation experiment measured the effects of soil properties on ammonia volatilization over 7 days from surface-applied urea and the efficacy of three urease inhibitors: Agrotain® Ultra (AT) as 0.09% NBPT, Limus® (L) as 0.06% NBPT + 0.02% NPPT, and NutriSphere-N® (NS) 30% calcium salt of maleic-itaconic copolymer among 83 soil surface samples from across the United States with a wide range of soil properties. The soil properties evaluated were: total exchange capacity, 1:1 CaCl2 pH, organic matter, buffering capacity, clay content, and urease activity. In Urea (R2 = 0.69) and Urea + NS (R2 = 0.62) models, total exchange capacity, clay, and buffering capacity significantly reduced ammonia volatilization, and organic matter significantly increased ammonia volatilization, while 1:1 CaCl2 pH and urease activity were non-significant. Clay, organic matter, and buffering capacity were correlated to total exchange capacity. Total exchange capacity was the strongest predictor and best consolidated variable to predict N loss of urea. In Urea + AT (R2 = 0.54) and Urea + L (R2 = 0.67) models, ammonia volatilization was significantly reduced at lower 1:1 CaCl2 pH and total exchange capacity, and all other soil properties were non-significant. The NBPT in Urea + AT and Urea + L likely decayed more rapidly under acidic soil conditions, resulting reduced NBPT efficacy and greater N loss at lower pH. Urea + AT and Urea + L reduced volatilization significantly by 18.2 percentage points compared to Urea or Urea + NS, and there were no significant differences between Urea + AT and Urea + L (α = 0.05). On average, NutriSphere-N® did not reduce volatilization.

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Marambe, Kodippili Arachchilage Yahampath Anuruddha Marambe. "Monitoring Crop Evapotranspiration in the Western Lake Erie Basin Using Optical Sensors." Bowling Green State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1535362877977252.

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Dissertations / Theses on the topic 'Lake core'

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