Dissertations / Theses on the topic 'Salt – Environmental aspects – Ontario'
To see the other types of publications on this topic, follow the link: Salt – Environmental aspects – Ontario.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 18 dissertations / theses for your research on the topic 'Salt – Environmental aspects – Ontario.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Paul, Morrie. "The application of remote sensing in the assessment of pipeline construction and oil spill impacts on farmland in Glengarry County, Ontario /." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65950.
Full text
2
Ueckermann, Julius. "Green initiatives in hospitals in Ontario : is there a business case." Thesis, Stellenbosch : Stellenbosch University, 2011. http://hdl.handle.net/10019.1/80784.
Full textAbstract:
Thesis (MBA)--Stellenbosch University, 2011.This study was conducted to investigate on what basis hospitals in Ontario could justify the capital and resource requirements needed to implement green initiatives. The study used two theoretical references as the basis for the literature review as well as for the interpretation of the results. The one reference used was a report released by the World Health Organization (WHO) and Health Care Without Harm (HCWH) in 2009, that addressed the responsibility of hospitals towards reducing greenhouse gas emissions. The second reference looked at a theoretical model that discussed four potential competitive environmental strategies that businesses can use to differentiate themselves based on green initiatives. The literature review more specifically discussed the seven opportunities that were identified by the WHO and HCWH that hospitals can use to reduce their carbon footprint. These were: (1) energy efficiency; (2) built environment; (3) alternative energy; (4) transportation; (5) waste; (6) water; and (7) food. Each opportunity was discussed in detail and was evaluated in both a competitive and non-competitive environment. In addition, each opportunity was evaluated in light of its ability to be used in one of the competitive environmental sustainability strategies. In order to assess what the regulatory pressures are on Ontario hospitals, the Canadian Environmental Protection Act was evaluated. No major environmental legislative pressures on hospitals could be identified. Another important part of the literature review was the evaluation of the funding model for Ontario hospitals. It was seen, that hospitals in Ontario received around 85 percent of their funding from the Ontario government and that hospitals and the ministry are both under financial pressure. This is an important indicator that funding to hospitals is very restricted. The research data for this study was obtained through a survey that was conducted among hospital representatives who have already implemented some form of green initiatives. The results from 33 questionnaires indicated that hospitals primarily implemented green initiatives to obtain cost savings. In this regard, an eco-efficiency strategy would be a logical competitive strategy for Ontario hospitals to follow. This is a clear indication that green initiatives are seen more as a cost reduction tool than a direct attempt to reduce greenhouse gas emissions. Projects that are quick to implement, require low capital and have a quick payback, are favoured. The areas on which hospitals have focused, were energy efficiency, waste management and water savings. In general, it seems that most green initiative projects were still in an immature stage. Further results also showed that hospitals had no opportunity to increase revenue by making use of the benefits of green initiative projects. The research concluded that the only basis on which Ontario hospitals could justify the capital and resource required to implement green initiatives, were on a cost savings basis. This report concludes with a discussion on the use of certain competitive strategies in a non-competitive environment before recommendations are made on how to improve the current situation. The study concludes with shortcomings of this study and recommendations on further research to be done.
3
Branfireun, Marnie. "The role of decomposing plant litter in methylmercury cycling in a boreal poor fen /." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33382.
Full textAbstract:
Decomposition and MeHg concentration were measured for Sphagnum fuscum, Sphagnum angustifolium and Chamaedaphne calyculata in a poor fen in the low boreal forest zone of the Canadian Shield. Litter bags were transplanted reciprocally into hummocks, hollows and lawns and retrieved after 1, 2, 3,11 and 15 months.Mass losses follow the trend: Chamaedaphne calyculata >> S. angustifolium > S. fuscum. Between species differences were far more significant than differences between locations or depths, indicating that litter quality is the major control on decomposition.
McHg concentrations generally increased during decomposition, particularly near the water table: for C. calyculata up to 13000%, for the two Sphagnum mosses up to 500%, suggesting that decomposition stimulates mercury methylation or McHg scavenging.
The discovery of a high McHg substance on C. calyculata leaf surfaces (25 ng g-1) suggests that much plant MeHg data may by skewed by the presence of a biologically active 'film'.
4
Sauer, Robert Eugene Jr. "Development and use of saltmarsh mesocosms in studies of sedimentary mercury transformation." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/19608.
Full text
5
Shaw, Gregory Alan. "Rehabilitation of the Orange River Mouth Salt Marsh : seed, wind and sediment characteristics." Thesis, Nelson Mandela Metropolitan University, 2007. http://hdl.handle.net/10948/603.
Full textAbstract:
The Orange River is an important source of freshwater and like many other wetlands in semi-arid regions, supports various social (Spurgeon, 1998), economic (Spurgeon, 1998; Bornman et al., 2005) and ecological functions. The saltmarsh at the Orange River Mouth has become degraded over time following numerous anthropogenic impacts. As a result the Transboundary RAMSAR site was placed on the Montreux record emphasising the importance for rehabilitation. The potential of the marsh for natural rehabilitation was assessed through three physical factors which were considered to have the most influence on the saltmarsh i.e. 1) sediment 2) water 3) wind. Three sampling areas were chosen to investigate the sediment characteristics of the ORM saltmarsh and the suitability for seed germination and adult survival. Site A was representative of the general marsh area, Site B was thought to have favourable sediment conditions for saltmarsh growth because of the large numbers of seedlings and Site C was prone to inundation by wind blown sediment. The sites were sampled in 2005 (dry conditions) and in 2006 after high rainfall and river flooding. Electrical conductivity (EC) of the sediment throughout the marsh was hypersaline in many instances above the tolerance range for S. pillansii (> 80 mS.cm-1) The freshwater event in 2006 lowered salinity significantly in two of the three sites. Differences in sediment characteristics were also compared for three habitats i.e. driftlines, open sites and under vegetation. Driftlines (C. coronopifolia = 872 seedlings m-2; S. pillansii = 1296 seedlings m-2) and the microhabitat associated with adult plants (C. coronopifolia = 803 seedlings m-2; S. pillansii = 721 seedlings m-2) created favourable conditions for seedling growth, however open unvegetated (C. coronopifolia = 56 seedlings m-2; S. pillansii = 49 seedlings m-2) areas had significantly lower seedling density. Due to the marsh currently being in a desertified state this study aimed to establish whether the remaining vegetation could produce enough seed to revegetate the marsh. Laboratory studies indicated that seeds of both species germinated best in freshwater (0 psu). The germination of S. pillansii seeds was 40 percent at 0 psu compared to 5 percent at 35 psu. After storage under hypersaline conditions (35 psu) C. coronopifolia showed 100 percent seed germination when returned to freshwater whereas storage at 70 psu decreased the viability of S. pillansii seeds. The plants are producing adequate seed that will allow for regrowth and rehabilitation if sediment and groundwater characteristics are suitable for seed germination, seedling growth and adult survival. However the increase in bare areas at the Orange River mouth as a result of salt marsh dieback has increased the available sediment source. The wind blown sediment has covered large areas of the remaining adult salt marsh vegetation, particularly in the northern corner at Site C, causing further die-back.
6
Blackburn, Lynda G. "Quantification and estimation of nitrous oxide emissions from dairy manure applications in a western Quebec pea-forage and an eastern Ontario alfalfa-forage cropping system : by Lynda G. Blackburn." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100771.
Full textAbstract:
Agricultural systems are known to emit nitrous oxide (N2O)---a potent greenhouse gas. The roving flux tower measuring system of Agriculture and Agri-Food Canada was used to make continuous measurements of N2O fluxes in an edible pea field in Western Quebec in 2003-04 and then in an alfalfa-timothy forage field in Eastern Ontario in 2004-05. The experiment was designed to capture, at the field scale, the expected large N2O emissions occurring as a result of fertilizer application for a year, in relation to both large precipitation events and spring thaw.Growing season N2O emissions averaged 0.5 to 5 mg N2 O-N m-2 d-1 with peaks following snow melt (between 5 and 8 mg N2O-N m-2 d-1) and manure applications (8 to 37 mg N2O-N m-2 d -1). Although generally small (<0.25 mg N2O-N m -2 d-1), emissions were detectable during the fall and winter, indicating the importance of including them in annual emission totals.
The measurements were used to verify the performance of the simulation model DNDC (DeNitrification-DeComposition) in estimating N2O emissions from legumes and in response to dairy manure application. Sensitivity tests were also carried out in which baseline input values were modified. Results suggest that the current model version (DNDC8.9) requires further modification prior to application for estimating greenhouse gas emissions in national accounting systems.
7
Patterson, Tai Zachary. "Freight shipper mode choice in the Quebec City-Windsor Corridor and its impact on carbon dioxide emissions." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102823.
Full textAbstract:
The Quebec City - Windsor corridor is the busiest and most important trade and transportation corridor in Canada. The transportation sector is the second largest greenhouse gas (GHG) emission category in the country. Governments around the world, including Canada, are considering increased mode share by rail as a way to reduce transportation emissions. To understand whether freight mode shift is a realistic means to reduce transportation emissions, an analytical model is needed that can predict the effect of government policy on mode split.This thesis provides background on the freight transportation-GHG nexus in Canada and describes the development, implementation, reasoning behind, and results of, a Stated Preference shipper carrier choice survey for the Quebec City - Windsor corridor conducted during the fall of 2005. It then describes how the resulting carrier choice models are used to estimate the potential to displace truck traffic to rail (premium-intermodal) under current conditions, as well as to test the effectiveness of different possible future policy or service offering scenarios.
The results show that premium-intermodal has the potential to capture a substantial share of traffic between the main destinations in the Quebec City - Windsor Corridor. However, its ability to contribute significantly to reducing CO2 emissions is limited. According to the analyses conducted, potential reductions are considered to be in the range of nil to 0.413 Mt---a fraction of what the federal government was hoping to be able to achieve through "further public-private collaboration to promote the use of intermodal freight opportunities and to increase the use of low-emission vehicles and modes" (Government of Canada 2002).
At the same time, these potential reductions are based on a small proportion of total truck-related emissions and a few city-pairs. Extension of the current analysis to more city-pairs separated by longer distances might arrive at different conclusions.
8
Sibley, Samuel D. Jr. "The Impact of Salt Marsh Hydrogeology on Dissolved Uranium." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/7262.
Full textAbstract:
We quantified U removal and investigated the efficacy of uranium as a quantitative tracer of groundwater discharge in a headwater salt marsh of the Okatee River, Bluffton, SC. Determining the magnitude of U removal is important for advancing U as a tracer of paleo-oceanic conditions. Since salt marsh groundwater is typically enriched in nutrients and other biologically and chemically reactive species, quantifying groundwater discharge from marshes is critical for understanding the ability of salt marshes to modify the chemistry of important species in surface waters.
We hypothesized that water-column U(VI) was removed by tidally-induced advection of surface water into permeable, anoxic salt marsh sediments, a process resulting in bacterially-mediated precipitation of insoluble U(IV)O2 and/or sorption of uranium to iron-oxides at the oxic/anoxic sediment interface. Furthermore, we suggested that hydraulic pressure gradients established by marsh-surface tidal inundation and seasonally-variable rainfall promote the discharge of salt-marsh-processed, uranium-depleted groundwater to tidal creeks, producing the surface-water U-removal signal.
Groundwater and surface water data revealed non-conservative uranium behavior. We documented extensive uranium removal from shallow marsh groundwater and seasonally variable uranium removal from surface waters. These observations allowed for the calculation of seasonally-dependent salt marsh uranium removal rates. On a yearly basis, our removal rate (58 to 104 mol m-2 year-1) reemphasized the importance of anoxic coastal environments for U removal.
High uranium removal, high barium concentration water observed seeping from creek banks at low tide supported our hypothesis that groundwater discharge must contribute to uranium removal documented in tidal surface waters. Average site groundwater provided an analytically reasonable endmember for explaining uranium depletion in surface water. Therefore, we used three endmember mixing models for estimating the fraction of surface water with presumed a groundwater signature. Our discharge estimates of 8 to 37 L m-2 day-1 agreed closely with previously published salt marsh values. Seasonality in discharge rates can be rationalized with appeal to seasonal patterns in observed rainfall, tidal forcing, and marsh surface bioturbation. Although more work is needed, the results of this portion of the study suggest that U may be an effective quantitative tracer of groundwater discharge from salt marshes.
9
Mudumbi, John-Baptist Nzukizi. "Perfluorooctane sulfonate and perfluorooctanoate contamination of riparian wetlands of the Eerste, Diep and Salt Rivers." Thesis, Cape Peninsula University of Technology, 2012. http://hdl.handle.net/20.500.11838/2017.
Full textAbstract:
Thesis (MTech (Environmental Management))--Cape Peninsula University of Technology, 2012.Perfluorinated compounds (PFCs), in particular perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) have been found in aquatic environments throughout the world. Recent studies have reported that owing to their bioaccumulative nature, PFCs may also be present in various water sources, resulting in human and wild-life exposure. Although, these PFCs usually occur at low concentration levels, their presence in the environment has nevertheless been a concern in both developed and developing countries, since water remains an important natural resource for most living species. Water and sediment from rivers are one of the matrices in which PFC contamination is studied, since rivers receive water from various sources. However, limited studies have been conducted in South Africa on PFC contamination of river water and sediments. Although PFCs are sometimes unintentionally released into the environment, the concentration and type of PFCs that contaminate water sources vary among countries and depend on the types of industry releasing them into the environment, suggesting that PFC contamination patterns can be expected to differ from country to country, with PFOA and PFOS being the predominant perfluorinated contaminants. The aim of this study was therefore to determine the concentration of PFOS and PFOA in riparian wetlands of the Western Cape, focusing on the Eerste, Diep and Salt rivers, which are the primary rivers in the largest catchment areas of the Western Cape, South Africa.
10
Wartena, Ryan Craig. "Generation of sodium oxide and discharge of carbon by the electrolysis of multi-component molten salt systems : a recycle process for kraft pulping chemicals." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/10281.
Full text
11
Martin, Alicia. "The Socio-Environmental Aspects of Students’ Food Literacy: An Exploratory Case Study of Two Ontarian High Schools." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37320.
Full textAbstract:
North American food environments have gone through dramatic shifts over the past six decades. During this period, we have witnessed the consolidation of a globalizing industrial agrifood regime, accompanied by new types of foods available and an excess of marketing. In recent years however, a growing number of scholars, environmentalists, rural organizations and consumers have highlighted the negative environmental and social impacts of this model of large scale, intensive monocultures. Another critique that has been more and more common is the lack of a comprehensive food literacy among youth populations. This thesis starts from the assumption that such knowledge is crucial to equip younger generations with the ability to understand the connections among these issues, to make conscious and informed choices and become engaged citizens, participating in transforming today’s predominantly unsustainable agrifood systems. This is essential as younger generations are the future consumers, heads of households and decision-makers in Canadian society. As such, one of the primary objectives of this research was to (re)situate the concept of food literacy amidst the many literatures while also providing an original comprehensive framework of analysis, reaffirming both its health and well-being and agrifood systems components. Consequently, and based on such assessments, the thesis offers an original and exploratory analysis of high school students’ food literacy levels. Using a mixed methods approach, it draws from qualitative and quantitative primary data resources and secondary literature to survey and compare eight groups of students in grades 9 and 10 in Ontario. Four of these groups took a food-related class and four were control groups, between two different types of food-related curricula. The research shows that a majority of the high school students who participated in the study have a basic level of food literacy. This is especially notable when including socio-environmental considerations in order to assess their level of agrifood systems’ literacy, which is the main focus and contribution that this research sought to evaluate.
12
Cuthbert, Iain Dawson. "Predicting the riverine concentrations and catchment exports of metals in rural drainage basins of Ontario and Québec." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60672.
Full textAbstract:
Concentrations of Fe, Al, Mn and Zn were measured monthly from April to October at 24 rural riverine sites in Ontario and Quebec. Empirical models were developed predicting riverine metal concentrations from a small set of within-stream and catchment variables. Models explained a significant proportion of the variation in Fe (85%), Al (90%), Mn (57%) and Zn (37%). Simple models predicting annual catchment exports of metals from average riverine suspended particulate concentrations and runoff were also developed. These models explained most of the variation in annual exports of Fe (94%), Al (92%), Mn (62%) and Zn (75%) from the 24 catchments.Models such as these can be used both to estimate catchment exports of metals to lakes, and to estimate riverine metal concentrations without requiring chemical analyses. The models also serve to distinguish background levels from those indicating metal contamination, and will, therefore, be useful in design of water quality guidelines.
13
Raffel, Ann Eileen. "Methyl Halide Production by Calcareous Periphyton Mats from the Florida Everglades." PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/1524.
Full textAbstract:
Methyl halides are trace gases with both natural and anthropogenic origins. Once generated, these gases transport chlorine and bromine into the stratosphere, where they play an important role in ozone depleting catalytic cycles. The Florida Everglades is one location where methyl halide emissions have been proposed to be elevated due to high primary production and ionic halogens. This region also provides a unique study environment due to salt water intrusions, which occur during storm or low marsh water level-high tide events. The purpose of this research was twofold. First, quantification of methyl chloride (CH3Cl) and methyl bromide (CH3Br) production from periphyton mats on a temporal scale was needed. Secondly, to determine how varying concentrations of salinity affect CH3Cl and CH3Br production originating from calcareous periphyton mats within the Everglades. Periphyton was exposed to continuous 12 hour dark/light cycles in varying concentrations of salt water (0, 0.1, 1, 5, and 10 parts per thousand). All water samples were analyzed to determine the production rate of CH3Cl and CH3Br in periphyton samples using a gas chromatograph coupled with an electron capture detector (GC-ECD). Periphyton mats were found to be a producer of CH3Cl in all freshwater (0 parts per thousand) trials and sampling times; however, results from CH3Br analysis found production rates that suggest consumption occurred in the majority of the 0 parts per thousand trials. Production rates for CH3Cl ranged from 0.077 to 0.109 g-1hr-1 after 24 hours, 0.027 to 0.073 pM g-1hr-1 after 48 hours, and 0.034 to 0.047 pM g-1hr-1 after 72 hours. Production rates for the CH3Br freshwater experiments ranged from -0.00025 to 0.00185 pM g-1hr-1 after 24 hours, -0.00022 to -0.00078 pM g-1hr-1 after 48 hours, and -0.00042 to -0.00061 pM g-1hr-1 after 72 hours. This research has also shown that increased salinity does have a significant positive effect on the production of CH3Cl and CH3Br from calcareous periphyton mats, which is important in areas that could be prone to salt water intrusions or rising sea levels due to global climate change.
14
Wettasinghe, Asoka. "Environmental behavior of Dacthal." Thesis, 1991. http://hdl.handle.net/1957/36972.
Full textAbstract:
The herbicide, Dacthal (dimethyl 2,3,5,6,-tetrachloroterephthalate) is
hydrolyzed to give the corresponding diacid and this derivative is a common
contaminant in ground water. In the Ontario region of eastern Oregon the
use of this herbicide on onions has resulted in the contamination of an
aquifer with this derivative. Since movement to groundwater is determined
by the hydrolysis of the parent compound to a more soluble derivative. The
rate at which this hydrolysis reaction occurs and the stability of the
metabolite must be defined. These parameters have been determined using
soils from Ontario in which onions had been raised. At room temperature
and 50% field capacity, the parent was hydrolyzed rapidly (half-life 16 days)
to the diacid derivative. An increase of the incubation temperature to 38°C
reduced the hydrolysis rate significantly (half-life 86.8 days). It is assumed
that this response reflects reduced microbial activity at the higher
temperature. At both temperatures only small amounts of the monoacid
intermediate were detected suggesting that the Dacthal monoacid was
being hydrolyzed at a faster rate than the parent. It was established that at
room temperature, the half-life of the monoacid was only 2.8 days. Over
the 300 days the experiments were carried out, little if any degradation of
the diacid metabolite could be detected.
There was virtually no degradation of the parent over a 60 day period in
sterilized soil, suggesting that microbial activity is primarily responsible for
this step. By contract, the monoacid was hydrolyzed at comparable rates
in sterilized and nonsterilized soil.
This study explains why the Dacthal metabolite is a common contaminant
in groundwater. The parent is rapidly hydrolyzed to the diacid which is
much more water soluble. More important, however, is the persistence of
the diacid metabolite in the environment.Graduation date: 1992
15
Ko, Lih-jong. "Factors influencing the atmospheric aerosol composition at two sites in western Oregon." Thesis, 1992. http://hdl.handle.net/1957/28977.
Full textAbstract:
Fine and coarse particles were collected for eight weeks during the
summer of 1991, at a coastal site (Yaquina Head) and a non-industrial site
(Corvallis) in Western Oregon to characterize the aerosol composition and
evaluate whether the sites are appropriate for sampling "background" marine
air. Concentrations of up to 11 species (S0₄²⁻, NO₃⁻, Cl⁻, Na, Fe, Ni, Pb, Cr, Co,
Sb, and CH₃SO₃H) for 95 samples were determined using four chemical
analysis techniques.
The influences of seasalt and soil dust were identified by analyzing
concentrations of Na and Fe in the aerosol samples. Relative elemental
composition in fine and coarse fractions indicated that the aerosol
composition at Yaquina Head was greatly affected by seasalt. "Seasalt"
enrichment factors (relative to Na) indicated that seasalt is the only source of
Cl⁻ and SO₄²⁻ in coarse particles at Yaquina Head. In contrast, the seasalt
influence was relatively weak at the Corvallis site. "Crustal" enrichment
factors suggested that soil dust was not a major source of Na⁺, Cl⁻, or S0₄²⁻ at
either site.
A simple conceptual model that relies on meteorological conditions was
used to identify sampling periods with long range transport from either
marine or continental areas as well as local influences. This model suggested
that during 61% of the experiment period the aerosols were advected from
marine areas. At Yaquina Head, 52% of the sampling periods are associated
with the "clean" background air (marine air with no local influences). Thus,
Yaquina Head represents a useful location for collecting marine background
air from the Pacific Ocean. The chemical composition of the marine
background air collected at the Yaquina Head site is similar to that for other
remote sites around the world. At Corvallis, "clean" marine background air
can occasionally (21%) be collected even though Corvallis is located 64 km
from the ocean.Graduation date: 1993
16
Bell, Justin Robert William Civil & Environmental Engineering Faculty of Engineering UNSW. "Cyclic deposition of salt-laden dusts as an explanation of salinisation in a groundwater recharge zone Coleambally irrigation area Riverine plain NSW." 2007. http://handle.unsw.edu.au/1959.4/40549.
Full textAbstract:
Salinisation of the shallow groundwater system has occurred coincident with the development of irrigation in the Coleambally Irrigation Area. Salinisation in irrigation areas has previously been attributed to the evaporative concentration of the water table; however, there are other sources of salt such as the accumulation of rainfall by vegetation and the dry deposition of salt-laden dusts. A significant store of crystalline gypsum, together with high concentrations of Na, Mg and Confidence limit, was found within the previously unsaturated zone of the Upper Shepparton Formation. The salt store was identified both within and outside of the groundwater mound; therefore evaporative concentration of the water table cannot be the source of salt. The transition from regional groundwater quality, as applied as irrigation to the ground surface, to shallow groundwater quality is simply explained by solubilisation of this salt store in the presence of soil CO2. Dating of basal palaeochannel sands indicates that the identified salt store, a profile of only 20 m, was accumulated during the last glacial cycle. Radiocarbon dating indicates that the peak in eluate salinity, at approximately 2 m below ground surface, is between 15,000 and 25,000 years old, coincident with the Last Glacial Maximum. The Last Glacial Maximum was a period of significantly enhanced aridity on the Australian continent. It was also found that the peak in eluate salinity coincided with a bi-modal particle size distribution. The bi-modal signature implies that these sediments were subject to the aeolian accession of dusts. It was found that the contribution of salt from dry deposition of dusts exceeded the contribution from rainfall by at least 1.9 to 11 times during the last glacial cycle. The results of this study imply that salt-laden dusts have, and continue to play an important role in the salinity and sodicity of soils in the Coleambally Irrigation Area and beyond.
17
Hillwalker, Wendy E. "Selenium and trace metal accumulation in detrital-benthic food webs of lotic and lentic wetlands, Utah, USA." Thesis, 2004. http://hdl.handle.net/1957/29920.
Full textAbstract:
Concentrations of selenium (Se), manganese (Mn), zinc (Zn), cadmium (Cd), lead
(Pb) and arsenic (As) were measured in the water column, sediment and biota, in conjunction
with selected physicochemical data, from representative wetland types at a mining site within
Salt Lake County, Utah, USA. The selected field sites included Oolitic Pond (lentic) and Lee
Creek (lotic), which are moderately contaminated brackish, alkaline aquatic wetlands
managed by a copper mining industry. These fishless wetlands are located in a geographic
region that poses risk to migratory shorebird populations from dietary Se. A spatial sampling
study demonstrated the extent of variation in total Se concentration within the wetlands. With
the exception of the sediment compartment, Se concentration did not differ significantly along
the 2-mile length of Lee Creek or within the Pond. The differences in sediment total Se
concentrations between the Creek East and West segments characterize lower Lee Creek as
having two segments distinguished by unique processes that influence the sediment Se
accumulation profiles. Se accumulation trends were observed temporally over 3-years (2000
to 2002) and over two seasons (spring and autumn). Total Se body burden in benthic
invertebrates was more clearly associated with sediment/detritus Se concentrations than with
surface water concentrations. Three invertebrate groups dominated the aquatic invertebrates
assemblage in the lotic and lentic benthos; primary consumers (Chironomidae, Diptera),
generalist feeders (Hemiptera) and predators (Odonata). The chironomid larvae accumulated
1.3 to 39 times the trace metal concentrations of the Hemiptera or odonate taxa, independent
of trace metal type (essential or non-essential) or wetland occupation. Organism-specific
factors, such as habitat selection and preferential feeding habits, were proposed to influence
benthic invertebrate accumulation profiles by modifying trace metal exposure. Mixed diets,
trophic omnivory and the complexity of wetland biogeochemistry limit the power of stable
nitrogen fractionation signatures to define benthic food web relationships. Wetland site-specific
processes impacted Se accumulating efficiency, with trace metal concentrations from
4 to 7 times greater within the lentic benthic system than the lotic. The fractionation of the
natural abundant stable carbon isotopes revealed the importance of sedimentary and detrital
organic carbon as dietary sources for the benthic food web. Sediment organic content was not
significantly associated with sediment, or invertebrate, Se accumulation profiles. Ecological
risk assessments based on sound understanding of metal chemistry and the interactions
between the sediment matrix and benthic organisms are necessary to provide tools for
environmental management.Graduation date: 2005
18
Martin, Katherine Clare. "Interactive effects of salinity and nutrients on mangrove physiology : implications for mangrove forest structure and function." Phd thesis, 2007. http://hdl.handle.net/1885/149911.
Full text