Le lagon de la Nouvelle Calédonie (Pacifique Sud-Ouest), est drainé par les entrées fluviales et océaniques sous la pression de l’érosion des sols ultramafiques (enrichies en Nickel et Cobalt). Le but de cette thèse était de mieux comprendre les sources et la variabilité spatio-temporelle de la matière organique dissoute colorée (MODC) et fluorescente (MODF) le long de continuum rivière-côte-lagon-large en zone lagonaire tropicale du Pacifique dans un contexte de changement climatique et d’anthropisation locale (activité minière). Les côtes Est et Ouest calédoniennes ont été échantillonnées pendant 1 an et demi et pendant la campagne CALIOPE 3 (côte Est) lors d’un épisode El Niño fort (2015-2016), ponctués de forts épisodes pluvieux. L’analyse parallèle factorielle (PARAFAC) des matrices d’excitation-émission de fluorescence (MEEFs) a abouti à l’indentifications de 5 fluorophores : humique-like marin, 2 tyrosine-like, et tryptophane-like d’origine autochtone issus des compartiments phytoplanctoniques et bactériens, et un fluorophore humique-like d’origine allochtone provenant des rivières drainant les côtes. La MODC à 350 et 442 nm suivait une dynamique fortement dépendante des apports fluviaux pouvant être découplée de la dynamique de la MODF. La MODF sur la côte Est suivait un cycle saisonnier (saison sèche/humide) contrairement à la côte Ouest dépendante de d'évènements pluvieux sporadiques. Des fluorophores (humique, tyrosine et tryptophane-like) ont montré des affinités avec certains métaux traces (Nickel, Manganèse, Cobalt) ce qui a permis de développer une expérience de quenching de fluorescence pour déterminer le pouvoir complexant de la MODF naturelle. / New Caledonia (South-West Pacific) is a tropical area under strong environmental pressure (climate change and local anthropogenic forcing). The aim of this thesis was to gain a better understanding of the colored (CDOM) and fluorescent (FDOM) dissolved organic matter dynamic in the New Caledonia Lagoon where strong ultramafic erosion pressure is associated with trace metals (i.e., nickel, manganese and cobalt). 3D spectrofluorimetry was used to characterize the CDOM/FDOM. The West and East coasts were sampled during one year and a half in a context of El Niño (2015-2016), interrupted by strong rainy events (storms) and during CALIOPE 3 cruise (East coast). A parallel factor analysis (PARAFAC) of EEMF led to the identification of 5 fluorophores: marine humic-like, 2 tyrosine-like and tryptophan-like peaks (T2 peak) from the biological balance between phytoplankton and bacterioplankton and a terrestrial humic-like from rivers draining caledonian coast. The CDOM signal at 350 and 442 nm had a strong dependency on river inputs accentuated during storms and revealed photodegraded CDOM. The FDOM signal in the East showed a seasonal cycle (wet/dry season) contrary to the West coast depending on sporadic rainy events. Data acquired during the CALIOPE 3 were coupled with trace metal concentrations, biogeochemical parameters, and plankton communities. Some fluorophores displayed a preferential association with nickel and cobalt. The complexation capacities of these fluorophores toward trace metals were revealed by a quenching experiment that allowed to derive complexation constants.

A espécie de cianobactéria Cylindrospermopsis raciborskii vem se destacando na literatura atual devido à sua presença e dominância em lagos e reservatórios em diversas regiões do planeta e a principal preocupação deste cenário é por ela ser potencialmente tóxica. Estudos revelaram que o crescimento e a síntese de toxinas em espécies de microrganismos fitoplanctônicos estão atrelados à limitação ou excesso de micronutrientes, porém, ainda são desconhecidos os efeitos desta variação na produção de saxitoxina (STX) por C. raciborskii. Para contribuir com o esclarecimento desta questão, investigou-se o efeito de diferentes concentrações dos micronutrientes Fe, Zn, Cu, Mn, Co e B no crescimento e na produção de STX de uma linhagem de C. raciborskii. Em salas climatizadas, culturas desta linhagem foram expostas durante 20 dias a 5 concentrações de cada micronutriente, com alteração do meio de cultura ASM-1. As respostas fisiológicas de C. racibosrkii a estas modificações foram verificadas através da velocidade máxima de crescimento (μmáx), rendimento do biovolume, tempo de duplicação (Td), concentração de clorofila a, assimilação de nitrato e ortofosfato e síntese de STX total (intra e extracelular). As maiores concentrações de STX por biovolume (STX/biovolume) foram obtidas nos tratamentos com baixa concentração de Fe (0,4 μM) e elevada concentração de Cu (0,8 μM). Nos micronutrientes Zn, Co e B, houve uma tendência de redução da síntese de STX nas maiores concentrações destes metais. Enquanto as concentrações extremas de Fe e Mn inibiram o crescimento (Fe: 0,4 e 400 μM e Mn: 0,7 e 600 μM), as concentrações centrais favoreceram (Fe: 4 a 60 μM e Mn: 7 a 200 μM). Elevada concentração de Cu (0,8 μM) causou aumento de 2,6 vezes (160%) do volume celular e redução na síntese de clorofila a, sem alterações significativas em μmáx e rendimento. O aumento da concentração dos micronutrientes Fe, Zn, Mn e B no meio de cultura causaram maior assimilação de ortofosfato por biovolume (P/biovolume). Estes principais resultados demonstraram que os micronutrientes afetam a síntese de STX e o crescimento de C. raciborskii, podendo ser associados aos diversos mecanismos de captura e detoxificação de metais que as cianobactérias possuem. Embora as extrapolações dos resultados laboratoriais para o ambiente devam ser realizadas com prudência, estudos relacionados à ecofisiologia de cianobactérias como este, são fundamentais para análise criteriosa de cada variável podendo ser utilizado como ferramenta de diagnóstico e prevenção de florações tóxicas. / Cylindrospermopsis raciborskii has been highlighted in several researches due to the dominance in many lakes and reservoirs around the world, the main concern about it due to the ability to produce toxins. Studies have revealed that growth and toxins production in phytoplankton species are linked to micronutrients limitation or excess. Nevertheless, micronutrient variation effects on saxitoxin (STX) production by C. raciborskii are still unknown. To contribute to clarify this issue, we investigated the effect of different micronutrients concentration, such as Fe, Zn, Cu, Mn, Co and B, on the growth and saxitoxin production of C. raciborskii strain. In climatized growth room, the cultures of C. raciborskii strain were exposed to 5 different concentration of each micronutrient, present in ASM-1 medium, during 20 days. The C. racibosrkii physiological responses was detected through maximum growth rate (μmáx), biovolume yield, doubling time (Td), chlorophyll-a, nitrate and orthophosphate assimilation and the total STX production (intra and extracellular). The higher concentrations of STX per biovolume (STX/biovolume) were observed in treatments with low Fe concentration (0.4 μM) and high Cu concentrations (0.8 μM). Higher concentrations of Zn, Co and B lead to low STX production. While the Fe and Mn extreme concentrations inhibited the growth (Fe: 0.4 and 400 μM and Mn: 0.7 to 600 μM), the central concentrations favored (Fe: 4 to 60 μM, and Mn: 7-200 μM). A high Cu concentration (0,8 μM) leads to 2,6 fold increase (160%) in cellular volume and decrease the chlorophyll-a content, however máx and biovolume yield did not change. Increasing the Fe, Zn, Mn and B concentration in the culture caused higher assimilation of orthophosphate per biovolume (P/biovolume). These results indicated that micronutrients affected C. raciborskii growth and STX production, and may be associated with the diverse cyanobacterial mechanisms of metals capture and detoxification. Cyanobacteria ecophysiology studies, as this research, are fundamental to careful analysis of each variable, which could be used as diagnostic and a tool to prevention of toxic blooms.

In order to understand the mineralogical association and distribution of arsenic (As) in the Hawthorn Group in central Florida, I examined in detail the chemical and mineralogical composition of 361 samples that were collected from 16 cores. Geochemical analyses were performed by hydride generation - atomic fluorescence spectrometry (HG-AFS) and inductively coupled plasma optical emission spectrometry (ICP-OES). The identification of discrete minerals was aided by scanning electron microscopy (SEM) and chemical compositions were obtained by electron-probe microanalyses (EMPA). Arsenic concentrations for all Hawthorn samples vary from 0.1 to 69.0 ppm with a mean of 5.6 ppm. Average As concentrations for the individual units of the Hawthorn Group vary significantly from 9.0 ppm in the Peace River Formation to 3.0 ppm in the Tampa Member of the Arcadia Formation. This detailed mineralogical and geochemical study demonstrates that: (1) Arsenic in the Hawthorn Group varies from the formation to formation and is primarily concentrated in trace minerals, such as pyrite; (2) Concentrations of arsenic in pyrite crystals can vary drastically from a minimum of 0 ppm to a maximum of 8260 ppm; (3) Pyrite occurs in framboidal and euhedral forms and is unevenly distributed throughout the Hawthorn Group; (4) Hydrous ferric oxides can contain up to 540 ppm of arsenic; (5) Phosphate and organic material, and clays contain lower arsenic concentrations that pyrite and hydrous ferric oxides; and (6) Arsenic, sulfur, and iron have lognormal distribution throughout the Hawthorn Group. This study is important because phosphorous, arsenic and sulfur are chemically closely related, and thus they co-occur posing a potential problem for the phosphate industry. Information about the concentration, distribution and mineralogical association of naturally occurring arsenic is essential to forecast its behavior during anthropogenically induced physico-chemical changes in the aquifer. Recently, aquifer storage and recovery (ASR) facilities in west-central Florida reported arsenic concentrations in excess of 100 micro g/L (100 ppb) in recovered water. The ASR storage zone in this area is in the Suwannee Limestone, which directly underlies the Hawthorn sediments. It is crucial to the future of ASR in this area to understand the source, distribution, and cycling of arsenic in the overlying Hawthorn Group and the Florida Platform.

This study examines the occurrence, distribution and storage of selenium in seagrass communities of Lake Macquarie, which is a heavily industrialised area of NSW, where notably high trace metal concentrations have been reported previously. Initially a suite of organisms was collected from a seagrass bed (Zostera capricornia) in the southeastern section of the lake to investigate the bioaccumulation and biomagnification of selenium. All organisms contained selenium, with sediment-dwelling organisms containing the highest Se concentrations. No consistent pattern of significant Se-metal correlations with Cu, Zn and Cd was found. Biomagnification of Se was evident, as concentrations increased from sediments and water to flora (algae and seagrass) to bivalves to Crustacea. However, this trend was not continued to the higher trophic groups of invertebrate predators and teleost fish. The bivalve Anadara trapezia was further studied. Intrinsic and extrinsic factors affecting the accumulation of Se were examined. Gender and mass were assessed in a single day study, followed by a temporal investigation of the effect of gender, reproductive cycle, temperature and salinity on Se accumulation. Gender had no effect on the accumulation of Se in A. trapezia. Se was present in all tissues (adductor, blood, foot, gills, intestine and mantle) and not immobilised or stored in a specific tissue, indicating that it plays a structural role in the tissues of A. trapezia. Se burden increased relative to size (shell length and dry mass) suggesting that Se is metabolically controlled within the organism. Se concentrations were found to fluctuate temporally because of: food availability in response to water temperatures; the reproductive cycle; and associated metabolic activities responding to temperature changes and food availability. Subcellular selenium associations in A. trapezia were examined to assist in the understanding of the fate of Se in marine tissues. Most of the Se was associated with proteins, suggesting that Se has a metabolic role in this marine organism. Proteins are intrinsically associated with the lipid bilayer of the cell membranes. A number of proteins (94, 85, 43, 36.5, 30, 23.4, 17.4 and 15 kDa) were separated by SDS PAGE from ethanol fractions. Determination of the Se concentration within individual proteins was not possible because the ratio of Se to protein was too low for further analysis. These findings indicated that Se plays a metabolic role in the tissues of the marine organism A. trapezia. The biochemical regulatory mechanism responsible for maintaining Se concentrations within the tissues is currently unknown.

Zinc, copper and cadmium accumulation was measured in two herbivorous gastropod molluscs Austrocochlea constricta and Bembicium auratum from Lake Macquarie NSW an area with a history of trace metal pollution. The investigation consisted of three main parts. The first part examined the influence of organism mass and location within the Lake on whole body tissue metal concentrations. This part of the study also compared the distributions of tissue metal concentrations of populations from Lake Macquarie, a known polluted environment, with those of populations from Jervis Bay NSW, an unpolluted environment, to establish whether either species is a net accumulator of zinc copper or cadmium. The second part of the investigation examined a range of factors which may influence whole body metal concentrations. One location in Lake Macquarie was sampled monthly from August 1995 to July 1996. The factors examined were temporal variation, gender, breeding cycle, and tissue distribution. The final part of the investigation examined the detoxification and storage of excess metals in the gastropods from Lake Macquarie. The mechanisms studied were metallothioneins and granules. The tissue metal concentrations of both species were found to be independent of mass. Location within Lake Macquarie did not significantly influence tissue metal concentrations. Variation between individuals was the most significant contribution to overall variation, resulting in a positive skewing of sample trace metal distributions. B. auratum populations from Lake Macquarie had significantly higher copper and cadmium tissue concentrations and A. constricta populations had significantly higher zinc, copper and cadmium tissue concentrations than the populations from Jervis Bay. This suggests that regulation of these metals is not occurring. A. constricta may therefore be considered a net accumulator of zinc, copper and cadmium and B. auratum of copper and cadmium. Tissue metal concentrations did not vary significantly over time. It is suggested that the organisms are in equilibrium with their environment. B. auratum has higher natural equilibrium concentrations than A. constricta particularly for copper and cadmium, suggesting different routes of exposure, uptake or accumulation for the two species. Gender and breeding cycle did not significantly influence tissue metal concentrations. Most of the variability in total copper and cadmium concentrations of both species was explained by variability in gonad tissue metal concentration, while variability in the gonad and somatic tissues zinc concentration explained about an equal amount of the variability in total zinc concentration. A. constricta and B. auratum were both found to induce a cadmium binding protein which has some features in common with metallothionein. A protein of around 10 000 Da which binds approximately 60% of the soluble cadmium was isolated using gel filtration. This protein was further separated into two isoforms using anion exchange. The first isoform eluted at the same time as MT I and the second at the same time as MT II rabbit liver standard. Large cells containing granular material which stained positive for calcium were observed interspersed among the connective tissue immediately behind the columnar epithelial cells lining the gut wall in both species under a light microscope. Calcium positive granular particles were also observed within the columnar epithelial cells of B. auratum. These species have been shown to be net accumulators of the trace metals investigated, with the exception of zinc in B. auratum. It has also been established that organism mass, gender and reproductive state, the partitioning of metals between tissues, and temporal effects are not confounding factors for the purposes of comparing trace metal concentrations between populations. They should therefore be effective biomonitors of the trace metals investigated, with the exception of zinc in B. auratum.

Trace metal speciation in aquatic environments is inherently complex due to the large number of possible interactions with dissolved and particulate components. Adsorption onto iron oxyhydroxide and bacterial surfaces, as well as the formation of metal-ligand complexes can play important roles in controlling the fate and transport of trace metals in natural environments. The objective of this study is to describe and understand metal speciation and distribution in a complex biogeochemical system by incrementally increasing the complexity from simple binary systems to a dynamic quaternary system containing a trace metal, iron oxide and bacteria that are active and metabolizing an organic ligand. Copper, cadmium, and phthalic acid (H2Lp) adsorption onto ferrihydrite in binary systems was well reproduced using the diffuse layer model (DLM). The adsorption of H2Lp adsorption was analogous to that of inorganic diprotic acids in terms of the relationship between the adsorption constants and acidity constants. In ternary systems H2Lp caused Cu2+ or Cd2+ adsorption to be either enhanced (due to surface ternary complex formation) or inhibited (due to solution complex formation) depending on the conditions. The DLM could only describe the effect of H2Lp on metal ion sorption by including ternary complexes of the form ≡FeOHMLp (0), where ≡FeOH is a surface site and M is Cu or Cd. The relationship between binary metal adsorption constants and the ternary complex adsorption constants from this and previous studies suggest several properties of ternary complexes. First, ternary complex structures on both ferrihydrite and goethite are either the same or similar. Second, those cations having large adsorption constants also have large equilibrium constants for ternary complex formation. Third, ligands forming stronger solution complexes with cations will also form stronger surface ternary complexes but because of the strong solution complexes these ligands will not necessarily enhance cation adsorption. The bacterial strain Comamonas spp. was isolated from the activated sludge of a wastewater treatment plant. Comamonas spp. could effectively degrade H2Lp in the presence of Cd2+ and ferrihydrite and was therefore chosen to study the effect of H2Lp degradation on Cd2+ speciation. Proton, cadmium and H2Lp adsorption onto Comamonas spp. were measured. The Comamonas spp. titration curve is flatter than that of ferrihydrite, indicating a higher degree of site heterogeneity at the bacterial surface. Adsorption edges of Cd2+ adsorption onto Comamonas spp. occurred over about 4~5 pH units compared to those of ferrihydrite which occurred over ≈ 2 pH units on a dry weight basis. Comamonas spp. can accumulate a larger amount of Cd2+ than ferrihydrite especially under lower pH conditions. Proton and Cd2+ adsorption onto Comamonas spp. cells over a wide sorbent/sorbate and pH range was reasonably well described by a four site non-electrostatic model. The acid-base and Cd2+ adsorption behaviour of Comamonas spp. in this work were within the range of studies of bacteria adsorption. Phthalic acid adsorption onto inactive Comamonas spp. was negligible over a pH range of 3 to 8 and became significant only at pH < 3 where H2Lp was fully protonated. This is consistent with the proposed mechanism for ligand adsorption onto bacterial surfaces which involved a balance between hydrophobic interaction and electrostatic repulsion. The presence of H2Lp decreased Cd2+ adsorption onto Comamonas spp. due to competition for Cd2+ between the bacterial cell surface and the formation of solution complexes of Cd2+. This was accurately modelled with the Cd-Lp solution species indicating that no significant surface ternary interaction occurred between Cd2+, phthalic acid and Comamonas spp.. Cadmium adsorption onto ferrihydrite-Comamonas spp. mixtures was slightly less than the simple additive predicted adsorption of ferrihydrite plus Comamonas spp.. This suggests there is a weak interaction between ferrihydrite and Comamonas spp. and this interaction could be modelled by including a generic reaction between the ferrihydrite and Comamonas spp. surface sites. Cadmium distribution in a system of inactive Comamonas spp.-ferrihydrite in the absence and presence of H2Lp could be predicted by combining the ferrihydrite and bacteria models with the inclusion of the ferrihydrite-bacteria interaction. The effects of H2Lp degradation on Cd2+ distribution were investigated in dynamic systems with live bacteria. Results showed that Cd2+ adsorption in these dynamic systems was reasonably estimated with the model parameters developed in the proceeding experiments though uncertainty exists in the dynamic process with regards to H2Lp biodegradation products and changes in the bacteria population. This thesis was therefore able to provide a better understanding of metal speciation in complex and heterogeneous realistic environments by experimentally examining and modelling metal speciation and distribution in various systems with increasing complexity. This helps to bridge the gap of quantitative description of metal speciation from simple laboratory experiment systems to real world systems, both natural and engineered.

Abstract In order to understand the source, transport pathway and sink of settling particulates off northeast Taiwan, time-series sediment traps (PPS-3/3) were deployed on the north slope of Ilan ridge (T18) and in the Okinawa trough (T15 and T16) to collect settling particulates. The trapped particulate samples were determined for apparent mass flux (T18), particle size distribution, and contents of lithogenic portion, metals (Al, Mg, Ca, Fe, Mn, Cu), opal, OC (organic carbon) and IC (inorganic carbon). The results show that mass flux in winter is higher than in summer except for typhoon or rainstorm in summer which may cause high particulate flux. At mooring T11 and T17, only 2 cups had collected particulates but with rapid decrease, and the remaining cups were empty. It is not clear whether Kuroshio plays a role and further investigation is needed. The trapped particulates were mainly clay and silt in the north slope of Ilan ridge and south Okinawa trough, and were sand and silt in the Mien-Hwa canyon. The portion of coarse silt and larger particles (>31 mm) decreases with an increase of distance from the land (from T11 to T18). The grain size distribution of particulate at T18 is similar to that at T15 and T16, but the mass flux in the north slope of Ilan ridge is an order of magnitude higher than in the south Okinawa trough. The size distribution pattern below 600m water depth is very similar at both T15 and T16, but the coarse fraction (> 31 mm) is more at the upper than lower traps, presumably due to lateral transport. The Mn content of the trapped particulates in the south Okinawa trough is twice as hign as that in the north slope of Ilan ridge. High Mn/Al ratio in the trough suggests that Mn is supplied by hydrothermal activities. Lithogenic portions occupy about 84~88.5% at T18, T16 and T15. Relative to other marginal seas biogenic contributions are clearly lower.

Trace metal speciation in aquatic environments is inherently complex due to the large number of possible interactions with dissolved and particulate components. Adsorption onto iron oxyhydroxide and bacterial surfaces, as well as the formation of metal-ligand complexes can play important roles in controlling the fate and transport of trace metals in natural environments. The objective of this study is to describe and understand metal speciation and distribution in a complex biogeochemical system by incrementally increasing the complexity from simple binary systems to a dynamic quaternary system containing a trace metal, iron oxide and bacteria that are active and metabolizing an organic ligand. Copper, cadmium, and phthalic acid (H2Lp) adsorption onto ferrihydrite in binary systems was well reproduced using the diffuse layer model (DLM). The adsorption of H2Lp adsorption was analogous to that of inorganic diprotic acids in terms of the relationship between the adsorption constants and acidity constants. In ternary systems H2Lp caused Cu2+ or Cd2+ adsorption to be either enhanced (due to surface ternary complex formation) or inhibited (due to solution complex formation) depending on the conditions. The DLM could only describe the effect of H2Lp on metal ion sorption by including ternary complexes of the form ≡FeOHMLp (0), where ≡FeOH is a surface site and M is Cu or Cd. The relationship between binary metal adsorption constants and the ternary complex adsorption constants from this and previous studies suggest several properties of ternary complexes. First, ternary complex structures on both ferrihydrite and goethite are either the same or similar. Second, those cations having large adsorption constants also have large equilibrium constants for ternary complex formation. Third, ligands forming stronger solution complexes with cations will also form stronger surface ternary complexes but because of the strong solution complexes these ligands will not necessarily enhance cation adsorption. The bacterial strain Comamonas spp. was isolated from the activated sludge of a wastewater treatment plant. Comamonas spp. could effectively degrade H2Lp in the presence of Cd2+ and ferrihydrite and was therefore chosen to study the effect of H2Lp degradation on Cd2+ speciation. Proton, cadmium and H2Lp adsorption onto Comamonas spp. were measured. The Comamonas spp. titration curve is flatter than that of ferrihydrite, indicating a higher degree of site heterogeneity at the bacterial surface. Adsorption edges of Cd2+ adsorption onto Comamonas spp. occurred over about 4~5 pH units compared to those of ferrihydrite which occurred over ≈ 2 pH units on a dry weight basis. Comamonas spp. can accumulate a larger amount of Cd2+ than ferrihydrite especially under lower pH conditions. Proton and Cd2+ adsorption onto Comamonas spp. cells over a wide sorbent/sorbate and pH range was reasonably well described by a four site non-electrostatic model. The acid-base and Cd2+ adsorption behaviour of Comamonas spp. in this work were within the range of studies of bacteria adsorption. Phthalic acid adsorption onto inactive Comamonas spp. was negligible over a pH range of 3 to 8 and became significant only at pH < 3 where H2Lp was fully protonated. This is consistent with the proposed mechanism for ligand adsorption onto bacterial surfaces which involved a balance between hydrophobic interaction and electrostatic repulsion. The presence of H2Lp decreased Cd2+ adsorption onto Comamonas spp. due to competition for Cd2+ between the bacterial cell surface and the formation of solution complexes of Cd2+. This was accurately modelled with the Cd-Lp solution species indicating that no significant surface ternary interaction occurred between Cd2+, phthalic acid and Comamonas spp.. Cadmium adsorption onto ferrihydrite-Comamonas spp. mixtures was slightly less than the simple additive predicted adsorption of ferrihydrite plus Comamonas spp.. This suggests there is a weak interaction between ferrihydrite and Comamonas spp. and this interaction could be modelled by including a generic reaction between the ferrihydrite and Comamonas spp. surface sites. Cadmium distribution in a system of inactive Comamonas spp.-ferrihydrite in the absence and presence of H2Lp could be predicted by combining the ferrihydrite and bacteria models with the inclusion of the ferrihydrite-bacteria interaction. The effects of H2Lp degradation on Cd2+ distribution were investigated in dynamic systems with live bacteria. Results showed that Cd2+ adsorption in these dynamic systems was reasonably estimated with the model parameters developed in the proceeding experiments though uncertainty exists in the dynamic process with regards to H2Lp biodegradation products and changes in the bacteria population. This thesis was therefore able to provide a better understanding of metal speciation in complex and heterogeneous realistic environments by experimentally examining and modelling metal speciation and distribution in various systems with increasing complexity. This helps to bridge the gap of quantitative description of metal speciation from simple laboratory experiment systems to real world systems, both natural and engineered.

Trace metal speciation in aquatic environments is inherently complex due to the large number of possible interactions with dissolved and particulate components. Adsorption onto iron oxyhydroxide and bacterial surfaces, as well as the formation of metal-ligand complexes can play important roles in controlling the fate and transport of trace metals in natural environments. The objective of this study is to describe and understand metal speciation and distribution in a complex biogeochemical system by incrementally increasing the complexity from simple binary systems to a dynamic quaternary system containing a trace metal, iron oxide and bacteria that are active and metabolizing an organic ligand. Copper, cadmium, and phthalic acid (H2Lp) adsorption onto ferrihydrite in binary systems was well reproduced using the diffuse layer model (DLM). The adsorption of H2Lp adsorption was analogous to that of inorganic diprotic acids in terms of the relationship between the adsorption constants and acidity constants. In ternary systems H2Lp caused Cu2+ or Cd2+ adsorption to be either enhanced (due to surface ternary complex formation) or inhibited (due to solution complex formation) depending on the conditions. The DLM could only describe the effect of H2Lp on metal ion sorption by including ternary complexes of the form ≡FeOHMLp (0), where ≡FeOH is a surface site and M is Cu or Cd. The relationship between binary metal adsorption constants and the ternary complex adsorption constants from this and previous studies suggest several properties of ternary complexes. First, ternary complex structures on both ferrihydrite and goethite are either the same or similar. Second, those cations having large adsorption constants also have large equilibrium constants for ternary complex formation. Third, ligands forming stronger solution complexes with cations will also form stronger surface ternary complexes but because of the strong solution complexes these ligands will not necessarily enhance cation adsorption. The bacterial strain Comamonas spp. was isolated from the activated sludge of a wastewater treatment plant. Comamonas spp. could effectively degrade H2Lp in the presence of Cd2+ and ferrihydrite and was therefore chosen to study the effect of H2Lp degradation on Cd2+ speciation. Proton, cadmium and H2Lp adsorption onto Comamonas spp. were measured. The Comamonas spp. titration curve is flatter than that of ferrihydrite, indicating a higher degree of site heterogeneity at the bacterial surface. Adsorption edges of Cd2+ adsorption onto Comamonas spp. occurred over about 4~5 pH units compared to those of ferrihydrite which occurred over ≈ 2 pH units on a dry weight basis. Comamonas spp. can accumulate a larger amount of Cd2+ than ferrihydrite especially under lower pH conditions. Proton and Cd2+ adsorption onto Comamonas spp. cells over a wide sorbent/sorbate and pH range was reasonably well described by a four site non-electrostatic model. The acid-base and Cd2+ adsorption behaviour of Comamonas spp. in this work were within the range of studies of bacteria adsorption. Phthalic acid adsorption onto inactive Comamonas spp. was negligible over a pH range of 3 to 8 and became significant only at pH < 3 where H2Lp was fully protonated. This is consistent with the proposed mechanism for ligand adsorption onto bacterial surfaces which involved a balance between hydrophobic interaction and electrostatic repulsion. The presence of H2Lp decreased Cd2+ adsorption onto Comamonas spp. due to competition for Cd2+ between the bacterial cell surface and the formation of solution complexes of Cd2+. This was accurately modelled with the Cd-Lp solution species indicating that no significant surface ternary interaction occurred between Cd2+, phthalic acid and Comamonas spp.. Cadmium adsorption onto ferrihydrite-Comamonas spp. mixtures was slightly less than the simple additive predicted adsorption of ferrihydrite plus Comamonas spp.. This suggests there is a weak interaction between ferrihydrite and Comamonas spp. and this interaction could be modelled by including a generic reaction between the ferrihydrite and Comamonas spp. surface sites. Cadmium distribution in a system of inactive Comamonas spp.-ferrihydrite in the absence and presence of H2Lp could be predicted by combining the ferrihydrite and bacteria models with the inclusion of the ferrihydrite-bacteria interaction. The effects of H2Lp degradation on Cd2+ distribution were investigated in dynamic systems with live bacteria. Results showed that Cd2+ adsorption in these dynamic systems was reasonably estimated with the model parameters developed in the proceeding experiments though uncertainty exists in the dynamic process with regards to H2Lp biodegradation products and changes in the bacteria population. This thesis was therefore able to provide a better understanding of metal speciation in complex and heterogeneous realistic environments by experimentally examining and modelling metal speciation and distribution in various systems with increasing complexity. This helps to bridge the gap of quantitative description of metal speciation from simple laboratory experiment systems to real world systems, both natural and engineered.

Trace metal speciation in aquatic environments is inherently complex due to the large number of possible interactions with dissolved and particulate components. Adsorption onto iron oxyhydroxide and bacterial surfaces, as well as the formation of metal-ligand complexes can play important roles in controlling the fate and transport of trace metals in natural environments. The objective of this study is to describe and understand metal speciation and distribution in a complex biogeochemical system by incrementally increasing the complexity from simple binary systems to a dynamic quaternary system containing a trace metal, iron oxide and bacteria that are active and metabolizing an organic ligand. Copper, cadmium, and phthalic acid (H2Lp) adsorption onto ferrihydrite in binary systems was well reproduced using the diffuse layer model (DLM). The adsorption of H2Lp adsorption was analogous to that of inorganic diprotic acids in terms of the relationship between the adsorption constants and acidity constants. In ternary systems H2Lp caused Cu2+ or Cd2+ adsorption to be either enhanced (due to surface ternary complex formation) or inhibited (due to solution complex formation) depending on the conditions. The DLM could only describe the effect of H2Lp on metal ion sorption by including ternary complexes of the form ≡FeOHMLp (0), where ≡FeOH is a surface site and M is Cu or Cd. The relationship between binary metal adsorption constants and the ternary complex adsorption constants from this and previous studies suggest several properties of ternary complexes. First, ternary complex structures on both ferrihydrite and goethite are either the same or similar. Second, those cations having large adsorption constants also have large equilibrium constants for ternary complex formation. Third, ligands forming stronger solution complexes with cations will also form stronger surface ternary complexes but because of the strong solution complexes these ligands will not necessarily enhance cation adsorption. The bacterial strain Comamonas spp. was isolated from the activated sludge of a wastewater treatment plant. Comamonas spp. could effectively degrade H2Lp in the presence of Cd2+ and ferrihydrite and was therefore chosen to study the effect of H2Lp degradation on Cd2+ speciation. Proton, cadmium and H2Lp adsorption onto Comamonas spp. were measured. The Comamonas spp. titration curve is flatter than that of ferrihydrite, indicating a higher degree of site heterogeneity at the bacterial surface. Adsorption edges of Cd2+ adsorption onto Comamonas spp. occurred over about 4~5 pH units compared to those of ferrihydrite which occurred over ≈ 2 pH units on a dry weight basis. Comamonas spp. can accumulate a larger amount of Cd2+ than ferrihydrite especially under lower pH conditions. Proton and Cd2+ adsorption onto Comamonas spp. cells over a wide sorbent/sorbate and pH range was reasonably well described by a four site non-electrostatic model. The acid-base and Cd2+ adsorption behaviour of Comamonas spp. in this work were within the range of studies of bacteria adsorption. Phthalic acid adsorption onto inactive Comamonas spp. was negligible over a pH range of 3 to 8 and became significant only at pH < 3 where H2Lp was fully protonated. This is consistent with the proposed mechanism for ligand adsorption onto bacterial surfaces which involved a balance between hydrophobic interaction and electrostatic repulsion. The presence of H2Lp decreased Cd2+ adsorption onto Comamonas spp. due to competition for Cd2+ between the bacterial cell surface and the formation of solution complexes of Cd2+. This was accurately modelled with the Cd-Lp solution species indicating that no significant surface ternary interaction occurred between Cd2+, phthalic acid and Comamonas spp.. Cadmium adsorption onto ferrihydrite-Comamonas spp. mixtures was slightly less than the simple additive predicted adsorption of ferrihydrite plus Comamonas spp.. This suggests there is a weak interaction between ferrihydrite and Comamonas spp. and this interaction could be modelled by including a generic reaction between the ferrihydrite and Comamonas spp. surface sites. Cadmium distribution in a system of inactive Comamonas spp.-ferrihydrite in the absence and presence of H2Lp could be predicted by combining the ferrihydrite and bacteria models with the inclusion of the ferrihydrite-bacteria interaction. The effects of H2Lp degradation on Cd2+ distribution were investigated in dynamic systems with live bacteria. Results showed that Cd2+ adsorption in these dynamic systems was reasonably estimated with the model parameters developed in the proceeding experiments though uncertainty exists in the dynamic process with regards to H2Lp biodegradation products and changes in the bacteria population. This thesis was therefore able to provide a better understanding of metal speciation in complex and heterogeneous realistic environments by experimentally examining and modelling metal speciation and distribution in various systems with increasing complexity. This helps to bridge the gap of quantitative description of metal speciation from simple laboratory experiment systems to real world systems, both natural and engineered.