Dissertations / Theses on the topic 'Salt – Environmental aspects'

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.

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.

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.

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.

Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2008.
Committee Chair: Spyros G. Pavlostathis; Committee Member: Ching-Hua Huang; Committee Member: John A. Pierson.

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The present dissertation had with main objective to analyse the regulatory framework of the pre ¿salt the light of national policy on climate change, identifying whether there are points of confronting between the two legal frameworks. Therefore, it was necessary to demonstrate the evolution of environmental law in the world and in Brazil, as well as the institutionalization of climate protection policy in Brazil, their policies and objectives. In the oil industry sector, evaluate the influence of owning countries and oil producers in the Brazilian energy matrix, the legal changes that have altered the ownership of natural resources throughout history, the change of legislation for oil exploration in the pre -salt field in 2010, and the current scenario of oil exploration in the polygon. In order to achieve the proposed goal, there was a brief overview on the scientific aspects of climate change and the voluntary commitments made by Brazil, in an effort to reduce gas emissions between 36,1 % to 38,9 % by 2020. It was found that oil is a finite resource and that, according to the theory of Peak Oil and the current target for oil exploration in the pre-salt, there are two possible future scenarios with different consequences to Brazil. It was understood that the country published two legislations, one of climate protection and other oil exploration in the pre-salt, which does not establish a dialogue and demonstrate a route of confront between the policies. Still, proposals were searched for confronting of the two scenarios mentioned above.
A presente dissertação teve como objetivo principal analisar o marco regulatório do pré-sal sob a luz da política nacional sobre mudança do clima, identificando se existem pontos de colidência entre os dois marcos legais. Para tanto, foi preciso demonstrar a evolução do direito ambiental do mundo e no Brasil, assim como a institucionalização da política de proteção ao clima no Brasil, suas diretrizes e objetivos. No setor da indústria petrolífera, foi necessário avaliar a influência dos países possuidores e produtores de petróleo na matriz energética brasileira, as mudanças legais que alteraram a propriedade dos recursos naturais ao longo da história, a mudança da legislação do petróleo para a exploração no campo do pré-sal em 2010, e o atual cenário de exploração de petróleo no polígono do pré-sal. De modo a cumprir o objetivo proposto, realizou-se uma breve abordagem sobre os aspectos científicos das mudanças climáticas publicadas pelo IPCC e os compromissos voluntários assumidos pelo Brasil, no sentido de reduzir suas emissões de GEE entre 36,1% a 38,9%, até 2020. Constatou-se que o petróleo é um recurso finito e que, de acordo com a teoria do Peak Oil e a atual meta de exploração de petróleo no pré-sal, existem dois possíveis cenários futuros com consequências distintas paras o Brasil. Entendeu-se que o país editou duas legislações: uma de proteção ao clima e outra de regulamentação da exploração de petróleo no pré-sal, que que não estabelecem um diálogo e demonstram uma rota de confronto entre as políticas. Ainda, buscou-se propostas para o enfrentamento dos dois cenários mencionados acima.

Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Pavlostathis, Spyros G.; Committee Member: Huang, Ching-Hua; Committee Member: Hughes, Joseph B.; Committee Member: Sobecky, Patricia A.; Committee Member: Spain, Jim C.

Thesis (PhD (Botany and Zoology))—University of Stellenbosch, 2009.
ENGLISH ABSTRACT: Metal pollution is a problem of increasing global concern. It could arise from industrial activities, as well as pesticide use in agriculture, among other sources. For adequate protection of the soil ecosystem from metal toxicity, the bioavailability of metals must be properly evaluated. A plethora of soil factors affect the bioavailability of metals to soil organisms. These include pH, clay and organic matter contents, salinity among others. While much is known about the influence of some of these parameters, little is known on how clay content and salinity modify the bioavailability of metals to soil organisms. This study investigated the influence of clay content and salinity on partitioning, uptake and toxicity of two essential metals (Cu and Zn) to the earthworm Eisenia fetida in separate laboratory trials. Partitioning of the metals was evaluated with 0.01 M CaCl2, DTPA (di-ethylene-triamine-penta acetic acid), and nitric acid extractions. The metal content of worms was determined by acid digestion, while growth, cocoon production, and mortality were used as endpoints showing toxicity to metals and/or salinity. To test the validity of some of the laboratory results, a field study was undertaken, using the earthworm Aporrectodea caliginosa. Further, the study assessed the effect of salinity, using a battery of laboratory tests (acute, chronic and avoidance tests) with natural and/or artificial soils on four species of organisms (a collembolan Folsomia candida, a potworm Enchytraeus doerjesi and two earthworm species E. fetida and A. caliginosa), representing different feeding patterns and ecological roles in soil. Results showed that with increased clay content, there was increased availability of Cu in the substrate, and increased toxicity to E. fetida as shown by data for mortality and growth. The situation with Zn was less significant at sub-lethal concentrations but much so at lethal concentrations. DTPA and CaCl2 extracted metals revealed changes in partitioning of Cu and Zn with changes in clay content, but this trend was not always consistent. Both DTPA and CaCl2 revealed increased availability of Zn in substrates with increased salinity. Salinity had an additive to synergistic effect with Zn in toxicity to E. fetida. When combined with Cu, salinity also increased the availability of Cu as shown by CaCl2 extracted fraction, and had additive effect on toxicity of Cu to the earthworm. The field study did not succeed in in iv confirming the results of the laboratory study due to confounding role of flooding after heavy rainfall and subsequent leaching of salts and Cu. The results of the experiment on acute and chronic toxicity tests for NaCl on E. fetida showed LC50 of 5436 mg/kg NaCl and EC50 for growth and cocoon production of 4985 and 2020 mg/kg NaCl. These values showed that earthworms might be negatively affected in many soils containing fairly moderate concentrations of salts. Similarly, A. caliginosa could not survive in natural soil containing relatively low salt concentrations (EC = 1.62 dS/m) while reproduction was severely affected at lower EC value of 0.52 dS/m. F. candida and E. doerjesi could survive in the highest salinity soil (EC = 1.62 dS/m) used in this study but their reproduction was severely affected from 1.03 dS/m. Overall, it appears that of all the taxa used, earthworm species were the most sensitive to saline stress and could proof useful in determining ‘safe levels’ of salt in contaminated soils. The results of the avoidance test showed that A. caliginosa avoided both natural and artificial saline soil containing concentrations lower than those avoided by E. fetida. The conclusion is that the influence of clay content and salinity on the bioavailability of Cu and Zn depends largely on the metal in question, but generally speaking, bioavailability and toxicity of the metals were reduced with increased clay content while the opposite was true for salinity. If the species used in this study can be seen as fairly representative of a wide range of soil organisms, the conclusion is that salinisation of soil will be detrimental to most soil organisms at relatively low saline concentrations. Given the role of beneficial soil organisms in several soil processes which in turn contribute to soil fertility and sustainable use of land, it is recommended that any farming practices that may lead to an increase in salt content of agricultural soils should be discouraged.
AFRIKAANSE OPSOMMING: Metaalbesoedeling is ‘n probleem wat toenemende globale kommer veroorsaak. Dit kan ontstaan as gevolg van industriële aktiwiteite sowel as van plaagmiddelgebruik in die landbou en ander bronne.Ten einde die grondekostelsel genoegsaam te beskerm, moet die biobeskikbaarheid van metale ge-evalueer word. ‘n Verskeidenheid van grondfaktore be-invloed die biobeskikbaarheid van metale vir grondorganismes Hulle sluit onder andere in pH, klei, organiese inhoud en soutgehalte. Hoewel heelwat bekend is oor die rol van sommige van hierdie parameters, is min bekend oor hoe klei en soutgehalte die biobeskikbaarheid van metale vir grondorganismes kan modifieer. Hierdie studie het die invloed van kleiinhoud and soutgehalte op die verdeling/partisie, opname en toksisiteit van twee essensiële metale (Cu en Zn) vir die erdwurm Eisenia fetida in afsonderlike laboratoriumproewe ondersoek. Kompartementele verdeling van die metale is geevalueer deur middel van ekstraksie-metodes met 0.01 M CaCl2, DTPA (di-etileentriamien- penta asysnsuur), en salpertersuur ekstraksies. Die metaalinhoud van wurms is bepaal deur suurverterings en spektrofotometriese analises te doen terwyl groei, kokonproduksie en mortaliteit van organismes gebruik is as gevoeligheidseindpunte om toksisiteit van metale en soutgehalte aan te toon. Om die geldigheid van somige van die laboratoriumresultate te toets, is ‘n veldstudie ook onderneem met die erdwurm Aporrectodea caliginosa. Die effek van soutgehalte is verder ondersoek deur ‘n battery van laboratoriumtoetse met vier spesies (‘n kollembool Folsomia candida,’n potwurm Enchytraeus doerjesi en twee erdwurmspesies E. fetida en A. caliginosa), wat verskillende voedingspatrone verteenwoordig. Die resultate het getoon dat met toenmende klei-inhoud was daar ‘n toename in die beskikbaarheid van Cu vir opname vanuit die substraat, asook ‘n toename in toksisiteit vir E. fetida soos deur die gegewens vir mortaliteit en groei uitgewys. Die situasie met Zn was minder betekenisvol by subletale konsentrasies en selfs baie minder so by letale konsentrasies. DTPA en CaCl2 ge-ekstraheerde metale het veranderinge in die partisie/verdeling van Cu en Zn uitgewys met verandering in klei-inhoud, maar die tendens was nie altyd konstant nie. Beide DTPA en CaCl2 ekstraksie het toenemende beskikbaarheid van Zn in substrate uitgewys met toenemende soutinhoud. Soutinhoud het ‘n additiewe/toegevoegde tot sinergistiese vi toksisiteitseffek saam met Zn vir E. fetida. In kombinasie met Cu het soutgehalte ook die geskatte biobeskikbaarheid van Cu verhoog soos uitgewys deur die CaCl2, geekstraheerde fraksie, en het ‘n additiewe effek gehad op die toksisitiet van Cu vir die erdwurm. Die veldstudie kon nie die resultate van die laboratoriumstudie bevestig nie weens die belemmerende rol van vloede na swaar reënneerslae en daaropvolgende uitloging van soute en Cu. Die resultate van die eksperimentele ondersoek na die akute en chroniese effekte van NaCl op E. fetida het ‘n LC50 van 5436 mg/kg NaCl en EC50 vir groei en kokonproduksie van 4985 en 2020 mg/kg NaCl opgelewer. Hierdie waardes het aangetoon dat erdwurms moontlik negatief beinvloed kan word in baie gronde wat ‘n redelike gemiddelde konsentrasie van soute bevat. Soortgelyk kon A. caliginosa nie oorleef in natuurllike grond wat relatief lae soutkonsentrasies bevat het (EC=1.62 dS/m) nie terwyl voortplanting sterk ge-affekteer is by ‘n lae EC waarde van 0.52 dS/m. F. candida en E. doerjesi kon oorleef in die grond met die hoogste soutgehalte (EC= 1.62 dS/m) maar hulle voortplanting is ernstig geknou vanaf 1.03 dS/m. In geheel blyk dit dat van allle taksa wat gebruik is, erdwurms die sensitiefste was vir die stres wat deur soutgehalte veroorsaak is. Die kennis kan nuttig wees in die bepaling van “veilige vlakke” van sout in gekontamineerde gronde. Die resultate van die vermydingstoetse het getoon dat A. caliginosa beide natuurlike en kunsmatig versoute gronde vermy het by konsentrasies wat heelwat laer was as dié wat deur E. fetida vermy is Die gevolgtrekking is dat die invloed van klei en soutgehalte op die biobeskikbaarheid van Cu en Zn grootliks afhanklik is van die metale wat betrokke is en dat biobeskikbaarheid en toksisiteit normaalweg verminder het met verhoogde klei-inhoud, met die teenoorgestelde wat waar was in die geval van soutgehalte. Indien die spesies wat in die studie gebruik is beskou kan word as redelik verteenwoordigend van ‘n wye reeks van grondorganismes, is die gevolgtrekking dat versouting van gronde nadelig sal wees vir meeste grondorganismes, selfs by relatief lae soutkonsentrasies. In die lig van die rol wat nuttige grondorganismes speel in verskeie grondprosesse wat bydraend is tot grondvrugbaarheid en volhoubare gebruik van gronde, word dit aanbeveel dat enige boerderypraktyk wat mag lei tot verhoging van die soutinhoud van landbougronde ontmoedig moet word.

En période hivernale, des fondants routiers sont épandus sur les chaussées afin de préserver la sécurité des usagers. Sous l'influence de divers paramètres, ces produits se retrouvent en partie dans l'environnement, le reste étant collecté par des systèmes de rétention des eaux de ruissellement routières. Or, les bassins de rétention ne sont pas conçus pour traiter ces fondants, et jouent uniquement un rôle de régulation des flux rejetés dans l’environnement. L’effet du NaCl sur l’environnement est néfaste, en raison de sa toxicité directe envers certains organismes et, indirectement parce qu’il contribue à augmenter la mobilité des ETM (Éléments Traces Métalliques), eux-mêmes toxiques. Ceci démontre un besoin d'assainissement particulier pour ces produits. L'objectif de cette thèse est d'étudier les transferts de NaCl par un bassin de rétention, mais également d'investiguer la possibilité d'utiliser la phytoremédiation comme base d'une solution d'assainissement des eaux de ruissellement routières. Le bassin de rétention choisi comme modèle est un bassin récent situé à Chenevières (Lorraine, France), en bordure d’une route nationale. La première partie du travail a porté sur la mesure et la caractérisation des transferts de NaCl dans ce bassin. L’eau a été collectée en entrée/sortie chaque semaine pendant 3 ans, et les concentrations en NaCl et ETM mesurées. Les conditions météorologiques et les données d’épandage de sel ont été suivies pour évaluer la proportion de sel effectivement transférée vers le réseau de collecte des eaux de ruissellement routières. Les résultats montrent que 25 à 50 % du sel épandu est effectivement collecté. De plus, les résultats sur la dynamique du NaCl prouvent que le bassin joue uniquement un rôle de rétention temporaire et de dilution avant rejet vers l’environnement. Ensuite, des mesures et analyses des sédiments du bassin et des sols de bord de route ont été conduites pour caractériser la spéciation et la mobilité des ETM dans ce contexte routier particulier. Dans ce cas précis, le NaCl n’a pas eu d’effet significatif sur la mobilisation des ETM, hormis le zinc (Zn). En revanche, il a provoqué la mobilisation d’autres ions majeurs. Concernant le traitement, les procédés conventionnels de dessalement d’eau sont trop coûteux et inadaptés. C’est pourquoi les potentialités d’une solution d’assainissement par phytoremédiation ont été explorées. Trois plantes halophytes ont été sélectionnées selon des critères permettant leur utilisation en contexte routier, Armeria maritima, Atriplex halimus et Atriplex hortensis L. Des expériences de germination/croissance ont été effectuées dans différentes conditions de salinité et de concentration en Zn pour évaluer leur tolérance à la salinité, à la présence de Zn et leurs capacités d’accumulation. Ces plantes ont montré une tolérance au NaCl dans des conditions de salinité représentatives de celles mesurées dans les réseaux d’assainissement routiers à Chenevières. De plus, les trois espèces accumulent dans leurs parties aériennes des quantités significatives de NaCl, ainsi que du zinc. L'utilisation des halophytes pour la phytodésalinisation en domaine routier s'avère être une technologie prometteuse pour répondre à la problématique de l'impact environnemental des fondants routiers
During winter, deicing salts are spread on roads in order to preserve road safety for users. Under the influence of different parameters, these compounds are partly transferred to the environment, the rest of it being collected by the road runoff retention systems. However, road runoff retention ponds have not been designed for deicing salt treatment; they only play a role in the regulation of fluxes before their rejection into the environment. Furthermore, NaCl has a harmful impact on the environment, because of its toxicity to certain aquatic organisms and because it contributes to the increase of trace metal (TM) mobility, which are toxic as well. This shows the need for a specific treatment for these compounds. The objective of this research is to bring better understanding of deicing salt dynamics in a retention pond, but also to investigate the potential use of phytoremediation as a treatment solution for road runoff. A model retention pond was selected; it is located along a highway in Chenevières (Lorraine region, France). The first part of the work focused on the monitoring and the characterization of NaCl transfers in this pond. Water was weekly sampled for 3 years at the pond input and output and NaCl and TM concentrations were measured. Meteorological conditions and salt spreading data were monitored to appraise the salt fraction actually collected by the pond. Results showed that only 25 to 50 % of the spread salt is effectively collected. Moreover, results on NaCl dynamics proved that the pond only plays a role on transient storage and salt dilution before rejection into the environment. Moreover, measurements and analyses of sampled basin sediments and roadside soils were performed to assess speciation and TM mobility in this particular context. In this case, no significant effect of NaCl was recorded except for zinc (Zn); but major ions were mobilized. When it comes to treatments, conventional desalination technologies are too expensive and inappropriate in this context. Then, potentialities of phytodesalination were explored. Three halophyte plants were selected on the basis of specific criteria, allowing their use in road runoff context: Armeria maritima, Atriplex halimus and Atriplex hortensis L. Germination and growth experiments were run in various salinity conditions and in the presence/absence of Zn, in order to assess their tolerance to salt and Zn, as well as their accumulation abilities. These plants showed a high tolerance for NaCl in salinities in the range of those encountered in road runoff existing treatment systems at Chenevières. The three species accumulated significant amounts of NaCl and zinc in their aerial parts. The use of halophytes for phytodesalination of road runoff is a promising technique to address the issue of environmental impact of deicing salts

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

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.

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