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This study investigates the interactions between dissolved trace metals and plastic debris under controlled laboratory conditions by using polyethylene pellets as a model plastic particle. Specifically, the study compared virgin pellets sourced from a local moulding plant with those collected from local beaches and subjected to aging, attrition and deposition of extraneous material. Pellets collected from the coastline of Southwest England were mainly polyethylene according to Fourier transform infra-red spectroscopy (FTIR), although occasional polypropylene pellets were present. Additionally, FTIR was used to identify the extent of degradation of pellets according to a photo-oxidation index derived from the relative magnitudes of specific absorbance peaks, and suggests pellet colour may give an indication of polymer degradation. Acid extractions of pellets collected from the coastline of Southwest England yielded metal concentrations ranging from low ng g-1 for metals such as Cd, Ni and Cr, to 7.7, 10.3 and 290 g g-1 for Cu Pb and Zn, respectively, while Al, Fe and Mn were present on beached pellets at concentrations of up to 171, 314 and 308 g g-1, respectively. Metal concentrations exhibited a high degree of inter- and intra-site variability. Correlation of metal concentrations with the photo-oxidation index indicates that pellet age is not a reliable indicator of metal concentrations. Batch experiments where metals (Cd, Co, Cr, Cu, Ni, Pb, Zn) were added to suspensions of pellets in seawater and estuarine water were performed in order to understand the extent and rates of trace metal adsorption to pellets. Langmuir modelling of adsorption isotherms in seawater indicated a range of maximum values for the accumulation of trace metals on beached pellets from 10 ng g-1 to 720 ng g-1 for Cd and Pb, respectively, in seawater spiked with 5 g L-1 of each trace metal. Langmuir constants for these relationships ranged from 0.140 (Cd) to 2.67 (Ni) mL g-1. Differences between trace metal affinities for pellets collected from the environment (beached) and those obtained directly from a plastics processing facility (virgin) were also identified. Adsorption maxima for virgin pellets ranged from < 1 ng g-1 (Cd) to 300 ng g-1 (Cr) with corresponding, respective Langmuir constants of 0.413 and 0.127 mL g-1. Adsorption of trace metals to beached pellets exceeds that to virgin pellets owing to the development of viable surface sites by photo-oxidation, biofouling and deposition of fine sediment particles on the former during exposure to environmental conditions. Adsorption kinetics were modelled successfully using a pseudo first-order reversible model. Chemical response times derived from kinetic constants ranged from 1.5 – 12 h for beached pellets and 0.2 to 4.5 h for virgin pellets, and were generally lower in seawater than in river water. Applying a similar batch approach to a system simulating an estuarine salinity gradient, the controlling effects of ionic strength and pH on the adsorption of trace metals to pellets were identified. Partitioning of Cd, Co and Ni exhibited inverse relationships with salinity, with partition coefficients (KD) decreasing from values of the order 101 to 10-1 or 10-2 mL g-1 (for beached pellets) as salinity is increased from < 0.05 to 33. Chromium exhibited contrasting behaviour within the estuarine gradient, with partitioning increasing with salinity, while Pb appears to be independent of salinity within this system. Chemical modelling was used to explain the results in context of changes in trace metal speciation which occur through the estuarine gradient. The bioaccessibility of metals on beached pellets to avian species was determined using an in vitro approach. Metal bioaccessibility in a simulated avian gastric environment comprising 10 g L-1 pepsin, 0.1 M NaCl and HCl at pH 2.8 indicated metals on pellets are labile (bioaccessibility ranges from < 10 % (Cr) to > 80 % (Mn)) and may be released readily within the digestive tract. Dissolution kinetics were modelled using the Noyes-Whitney equation, from which rate constants were determined in the range 3.1 x10-4 (Cr) to 8.7 x10-1 %-1 h-1 (Mn). This study has shown, for the first time, that plastic pellets have the potential to accumulate and transport trace metals in the marine environment. Furthermore, metal accumulation on plastic pellets is controlled by estuarine master variables such that conditions which favour or limit adsorption can be defined. Pellets present a previously unreported vector for the transport of metals in the environment, and have the potential to convey metals to organisms upon ingestion. The findings of this thesis have implications for interactions between metals and plastics more generally in the marine environment.

This study combined concentration-discharge analyses (filtration at 0.45 m), cascade filtrations (at 1.2, 0.4, and 0.025 m) and asymmetrical flow field flow fractionation (AF4) to probe the influence of colloidal carriers (dissolved organic matter and inorganic nanoparticles) on observed concentration-discharge relationships for trace metals in a 155 ha forested catchment of the Santa Catalina Mountains Critical Zone Observatory (SCM CZO), Arizona. Many major elements (Na, Mg, Si, K, Ca) show no colloidal influence, and concentration-discharge relationships for these species are explained by previous work. However, the majority of trace metals (Al, Ti, V, Mn, Fe, Cu, Y, REE, U) show at least some influence of colloids on chemistry when filtered at the standard 0.45 m cutoff. Concentration-discharge slopes of trace metals with modest colloidal influence are shallow (approximate to 0.3) similar to that measured for dissolved organic carbon (DOC, 0.24), whereas elements with greater colloidal influence have steeper concentration-discharge slopes approaching that of Al (0.76), the element with the largest colloidal influence in this study (on average 68%). These findings are further supported by AF4 measurements that show distinct and resolvable pools of low hydrodynamic diameter DOC-sized material coexistent with larger diameter inorganic colloids, and the ratio of these carriers changes systematically with discharge because the DOC pool has a concentration-discharge relationship with shallower slope than the inorganic colloidal pool. Together these data sets illustrate that positive concentration-discharge slopes of trace metals in stream waters may be explained as the relative partitioning of trace metals between DOC and inorganic colloids, with contributions of the latter likely increasing as a result of increased prevalence of macropore flow.

Despite the importance of coalbed methane (CBM) as a natural gas resource, little is known about the microbial communities responsible for production of biogenic CBM (~20% of all CBM gas). It is thought that coal-associated microbial communities are limited by nutrients, such as nitrogen or phosphate and a of suite trace elements, but it's not clear whether these nutrients are sourced from in-situ biodegradation of the coal or transported in with groundwater recharge. To address this knowledge gap, we examined the nitrogen and phosphorous species and trace metal geochemistry of the solid coal and overlying siliciclastic sediment and associated groundwater from monitoring wells across the Powder River Basin (PRB). Four Groups were identified that represent the geochemical evolution of groundwater from shallow unconsolidated siliciclastic aquifers, to recharge-associated coal waters, to sulfate-reducing coal waters, and finally, methanogenic coal waters, along a hydrologic gradient within single coal seams. The highest nutrient concentrations were found in the first two water types, and the lowest in the last two, suggesting that essential nutrients are mobilized at the surface and transported downgradient into the coal and overlying unconsolidated siliciclastic sediment. However, by the time groundwater reaches sulfate-reducing or methanogenic conditions, the nutrients are either utilized in reactions or precipitated under changing redox conditions. Sequential chemical extraction experiments of coal and siliciclastic core materials revealed that all essential nutrients for microbial methanogenesis are present and easily leachable into groundwater. Therefore, under anoxic conditions, microbial communities are unlikely to be limited by the presence of essential elements; rather, they are likely limited by the slow rates of coal biodegradation and liberation of essential nutrients.

A contaminação dos ecossistemas aquáticos por metais-traço demanda preocupação já que estes contaminantes podem exercer efeitos tóxicos sobre a biota e aumentar os custos para tratamento da água. Em geral, tais problemas de degradação são decorrentes de uma gestão de recursos hídricos deficiente. Tendo como área de estudo a represa Paiva Casto, reservatório integrante do Sistema Cantareira, maior sistema de abastecimento público da região metropolitana de São Paulo, este trabalho teve o intuito de: investigar o histórico da contaminação por metais-traço (Cd, Cr, Cu, Ni, Pb, Zn, Mn, Al) por meio da geocronologia por 210Pb e indicar um valor de referência para estes; identificar a heterogeneidade espacial destes contaminantes; analisar a biodisponibilidade e com base na possibilidade de adequar etapas do sistema de gestão de recursos hídricos europeu, a Diretiva Quadro da Água (DQA) discutir a qualidade química dos sedimentos da represa em estudo. Foram efetuadas duas coletas em campo, destinadas à avaliação do histórico da contaminação ambiental por metais-traço e à análise da biodisponibilidade por meio da técnica de sulfetos volatilizáveis por acidificação (SVA) e metais simultaneamente extraídos (MES). O histórico da contaminação por metais-traço abrangeu um período de 100 anos e indicou que os maiores impactos na região, em relação a estes contaminantes, ocorreu em período anterior ao início de operação da represa Paiva Castro, com exceção do Cu. Para o Cu, em sedimentos superficiais, os teores excederam até três vezes e meia o VR. Este resultado é provável consequência da aplicação de sulfato de cobre para o controle de florações de algas. Os dados para os VR divergiram daqueles estabelecidos para a crosta terrestre, porém foram semelhantes aos encontrados para a bacia do Alto Tietê, com exceção dos metais Cr e Pb. A análise de (SVA/MES) indicou que os metais não estavam biodisponíveis. Dentre as áreas amostradas, a região da barragem apresentou ao longo do tempo as maiores taxas de acumulação para metais-traço em contraposição à área de captação das águas para abastecimento público. Em relação a DQA, constatou-se que existe capacidade científica para avançar na incorporação de novos instrumentos na gestão, principalmente no Estado de São Paulo, entretanto, é preciso que haja sistemas de saneamento e monitoramento adequados e especialmente decisão política e rigor na aplicação destes novos instrumentos, caso contrário a incorporação da DQA é inviável. Aplicando algumas das normas da DQA na avaliação da qualidade química dos sedimentos da represa Paiva Castro constatou-se que a qualidade geral para este manancial é boa. Apesar disto é necessário que as políticas públicas sejam de fato aplicadas contra a degradação deste importante manancial, caso contrário a boa qualidade deste reservatório estará em risco / Contamination of aquatic ecosystems by trace metals demand concern since these contaminants may cause toxic effects on biota and increase costs for water treatment. In general, such degradation problems are due to a poor water management. A study was conducted at Paiva Castro reservoir, one of the reservoirs of the Cantareira System, largest public water supply system in the metropolitan region of São Paulo, this study aimed to: investigate the history of the accumulation of trace-metals (Cd, Cr, Cu, Ni, Pb, Zn, Mn, Al), through geochronology by 210Pb; establish background values (BV); analyze spatial heterogeneity; bioavailability and based on the possibility of adjusting some instruments of the European water resources management system, the Water Framework Directive (WFD), discuss the chemical quality of Paiva Castro\'s sediments. Two collections were performed, to assess the historical environmental contamination by trace-metals and to analyze the bioavailability using the technique of sulfides volatilizable by acidification (AVS) and simultaneously extracted metals (SEM). The history of contamination by trace- metals covered a period of 100 years and indicated that the greatest impacts in the region occurred in periods prior to the reservoir operation, with the exception of Cu. For Cu, in surface sediments, the levels exceeded three times and a half the BV. This result is probable consequence of copper sulphate application for controlling algal blooms. Data for BV were different from those found in the earth\'s crust, but similar to those found for the Alto Tietê basin, except for Cr and Pb metals. Analysis (AVS/ SEM) indicated that metals were not bioavailable. Among the sampled areas, the region of the dam, showed the highest rates of accumulation for trace- metals in contrast to the catchment area for public water supply. Regarding WFD, it was observed that there is scientific capacity to incorporate new instruments in the management, mainly in São Paulo, however, there must be adequate sanitation and monitoring systems and especially political decision and rigor in the application of these new tools, otherwise the incorporation of the WFD is unviable. Applying some of the WFD instruments in assessing the chemical quality of Paiva Castro\'s sediments, it was found that the quality of this ecosystem is good. Nevertheless, it is necessary that public policies are actually applied against the degradation of this important ecosystem; otherwise, reservoir\'s \'good quality\' will be at risk

An improved understanding of the geochemical partitioning of trace metals and tributyltin (TBT) in sediments is of great importance in risk assessment and remedial investigation. The aim of this thesis was to examine the distribution and partitioning behaviour of trace metals and TBT in benthic, estuarine sediments. This was achieved by a series of field- and laboratory-based studies investigating factors controlling the geochemical behaviour of trace metals and TBT in sediments from south-east Queensland, Australia. The distribution and enrichment of selected trace metals in benthic sediments of the Southport Broadwater (a semi-enclosed coastal body of water adjacent to the Gold Coast city, south-eastern Queensland, Australia) was studied. Sediment contamination for Cd, Cr, Cu, Ni, Pb, Sn and Zn was assessed by (1) comparison with Australian sediment quality guidelines, (2) calculation of the index of geoaccumulation based on regional background values, and (3) geochemical noi-malisation against Al (i.e. the abundance of alumino-silicate clay minerals). Based on this approach, several sites were found to be strongly enriched with Cu, Pb, Sn and Zn, arising from sources related to either urban runoff or vessel maintenance activities. The geochemical partitioning of Cu, Pb and Zn was examined in sediments collected from three of these sites of sediment contamination. Total Cu, Pb and Zn concentrations in coarse-textured (65 to 90 % sand sized particles), sub-oxic sediments (Eh + 120 to +260 mV) ranged from 8.3 to 194 mg/kg for Cu, 16.3 to 74.8 mg/kg for Pb and 30.1 to 220 mg/kg for Zn, and were related to vertical trends in sediment texture. The association of Cu, Pb and Zn with amorphous oxides, crystalline oxides and organic matter was linearly dependent on the abundance of each phase. For retention by amorphous oxide minerals, the trace metal retention ranged from 5.2 to 23.7 mgcjgFe oxide as Fe for Cu, 1 2.8 to 21 .5 mgpb/gFe oxide as Fe for Pb, and 23. I to 85.7 mgm/gFe oxide as Fe for Zn. Corresponding values for association with crystalline oxides were an order of magnitude less than those for amorphous oxides, indicating a weaker affinity of trace metals for crystalline oxides. The relationships describing association with organic matter ranged from 17.6 to 54.0 mgcu/gorg c for Cu, 6.1 to 9.6 mgpb/gorg c for Pb and 6.4 to 16.4 mgzn/gorg c for Zn. The in-situ solid/pore-water partitioning of TBT and the degradation products, dibutyltin (DBT) and monobutyltin (MBT), was determined for an estuarine sediment profile with previously identified elevated Sn concentrations. Total butyltin levels were (depending on depth) 220 to 8750 jig/kg for TBT, 150 to 5450 jig/kg for DBT and 130 to 4250 jig/kg for MBT. Pore-water butyltin concentrations ranged from 0.05 to 2.35 jig/L for TBT, 0.07 to 3.25 jiglL for DBT, and 0.05 to 0.53 J.tgIL for MBT. The organic carbon normalised distribution ratios (Doc) were similar for TBT, DBT and MBT, and were io to 106 L/kg. Values for the Butyltin Degradation Index (BDI) were larger than I at depths greater than 10 cm below the sediment/water-column interface, indicating that substantial TBT degradation has occurred in the sediments. This suggests that natural attenuation may be a viable sediment remediation strategy. Factors controlling the partitioning behaviour of Cu, Pb and Zn in nonsulfidic, estuarine sediments were examined in controlled laboratory-based studies with the use of combined sorption curve - sequential extraction analysis. This allowed determination of sorption parameters for Cu, Pb and Zn partitioning to individual geochemical fractions. Partitioning behaviour in sulfidic sediments was also determined by sequentially extracting Cu, Pb and Zn from synthetic sulfide minerals, and from natural sediment and pure quartz sand after spiking with acid-volatile sulfide (AVS). Trace metal sorption to the 'carbonate' fraction (pH 5, NaOAc extraction) increased with metal loading due to saturation of sorption sites associated with the 'Fe-oxide' (NH2OH.HCI extraction) and 'organic' (H202 extraction) fractions in non-sulfidic sediments. Freundlich isotherm parameters describing sorption to the 'Fe-oxide' and 'organic' fractions were dependent on the sediment Fe-oxide and organic carbon content, respectively. Sequential extraction of Cu from pure CuS, AVS-spiked sediment and AVS-spiked quartz sand showed that AVS-bound Cu was quantitatively recovered in association with the 'organic' fraction. However, some AVS-bound Pb and Zn were recovered by the NH2OH.HCI step (which has been previously interpreted as 'Fe-oxide' bound metals) in the sequential extraction procedure used in this study. This indicates that the sequential extraction of Pb and Zn in sulfidic sediments may lead to AVS-bound metals being mistaken as Fe-oxide bound species. Caution should therefore be exercised when interpreting sequential extraction results for Pb and Zn in anoxic sediments. Tributyltin (TBT) sorption to four natural sediment samples in artificial seawater was also examined under a range of modified pH and salinity conditions in controlled laboratory-based studies. Three of the sediment samples were relatively pristine with regard to TBT contamination, but the fourth was a TBT-contaminated sediment from a commercial marina. Sorption of TBT was described well by linear sorption isotherms, with distribution coefficients ranging from 6.1 to 5210 L/kg depending on pH and salinity. Sediment organic C content and particle size distribution were important determinants of sorption behaviour. The presence of resident TBT in the contaminated marina sediment caused a substantial reduction in TBT sorption due to satuaration of high selectivity sites. Desorption of TBT from the marina sediment was described by relatively large observed distribution coefficients ranging from 5100 to 9400 L/kg, suggesting that aging effects may reduce sorption reversibility. Increased artificial seawater salinity generally reduced TBT sorption at pH 4 and pH 6, but enhanced TBT sorption at pH 8. Regardless of salinity, maximum sorption of TBT was observed at pH 6, which is attributed to an optimal balance between abundance of the cationic TBT species and deprotonated surface ligands. Consideration of aqueous TBT speciation along with octanol-water partitioning behaviour suggest that hydrophobic partitioning of TBTCI to non-polar organic matter was important for pH (up to) 6, whilst partitioning of TBTOH was important at higher pH. The effect of aging on the solid/pore-water partitioning and desorption behaviour of TBT in sediments was examined. Three sediment samples with contrasting physical and chemical properties were spiked with 10 mg/kg TBT and aged under sterile conditions for periods of time ranging from I to 84 days. Aging had a negligible effect in a sandy sample with very low organic carbon content (0.2 % w/w). In contrast, for samples with larger amounts of organic carbon (2.6 and 4.8 % w/w), the effect of aging on the solid/pore-water partitioning behaviour was significant. For these samples, the apparent distribution coefficients (Ks) obtained from sequential two hour desorption experiments exhibited a two-fold increase between spiked sediments subjected to aging for 1 day and 84 days. This study demonstrates that aging effects may be an important aspect of TBT fate in contaminated sediments. Overall, the results described in this thesis demonstrate that environmental factors (i.e. pH, salinity, Eh, aging) and sediment composition (i.e. abundance of fine alumino-silicate minerals, organic matter, Fe-oxides, reactive sulfides) exert substantial effects on trace metal and TBT partitioning. The current reliance on measurement of total trace metal and TBT concentrations in contaminated sediment management may consequently lead to inaccurate estimates of environmental risk and inappropriate remediation measures if other factors regulating contaminant distribution and partitioning are ignored.

The atmospheric transport of various substances from the continents to the oceans plays an important role in biogeochemical processes. Trace metals, iron in particular is of great interest as its availability regulates the growth of phytoplankton over large areas of the ocean. This dissertation focuses on examining and characterizing the factors that affect the solubility of trace metals in Miami and Barbados aerosols and precipitation, in particular species that could play a role in surface seawater biogeochemistry (Fe and trace metals such as Al, V, Cr, Mn, Cu, Co, Ni, Zn, As, Tl, Ba, Cd, Pb, Th, Ti, Zr, and REE's). To enable this study existing methods of colorimetric spectroscopic and inductively coupled plasma mass spectrometry analysis were improved and modified. This dissertation examines several issues related to source inputs: 1.) Are single spot sources within the North African dust source distinguishable after long transport by their bulk metal composition and thus important in the characteristics of individual mineral dust samples? 2.) What is the temporal variability and controlling factors in trace metal solubility in trade wind aerosols collected over Barbados? 3.) Which factors control the observed trend of speciation and increasing iron solubility in decreasing aerosol loading? Additionally a kinetic model of species specific iron (II) to iron(III) oxidation kinetics in NaCl Brines was conducted at nano-molar levels. This study greatly expands the ability to predict rates of iron oxidation at concentrations closer to those observed in natural systems.

Water samples were collected along salinity gradients during different seasons from three estuaries (Tseng-Wen, Gao-Ping, Er-Ren) and coasts in/off southwestern Taiwan. In order to assess the partitioning of trace metals between solution and particle, the concentrations of dissolve and particulate trace metals (Cd, Cu, Ni, Pb) along with their chemical affinity fractions, were determined. This study investigated the variations in distribution and partitioning of the different metals in estuarine waters, and examined the effects of oxides and particulate organic matter on the partitioning of trace metals in waters from different estuaries. Fractionation of dissolved trace metal species was based on ion exchange (Chelex-100 and AG MP-1 resins) separation techniques. The fractions obtained were operationally defined as labile (Chelex), organic (AG MP-1) and inert. Particles were extracted to three phases (surface adsorbed phases, Fe¡VMn oxide/organic phases and refractory phases) using sequential extraction techniques. Seasonally variable distributions of dissolved trace metals were found in the Tseng-Wen estuary. The behavior of trace metals was mainly influenced by anthropogenic input during the dry season in the upper Tseng-Wen estuary, while mixing processes controlled the distribution of trace metals during the wet season. The dilution effect was a major factor in the metal distribution in the Gao-Ping estuary due to high river discharge. The higher concentration of metals in the Er-Ren estuary, in contrast to other estuaries indicated that the Er-Ren estuary has serious pollution concerns. According to the results of particulate metal fractions obtained, Cd and Pb existed predominantly in the surface adsorbed phase. The speciation and spatial distribution of Cd were similar to those of Mn, indicating that the formation of authigenic Mn oxides affected the distribution of Cd in estuaries. The percentage of oxide /organic phase for Cu accounted for 25% of total particulate Cu, but dose not correlate well with particulate organic carbon, implying that organic carbon is not the only factor controlling particulate Cu distribution. Ni was present mainly in lattice phase, except in the Er-Ren estuary where anthropogenic Ni loading was high. In the Tseng-Wen and Gao-Ping estuaries, the percentages of lattice phase of all metals determined in this study during the wet season were higher than those during the dry season. These seasonal variations are probably resulted from different flushing times in dry/wet seasons, which control the extent of geochemical processes for trace elements.

Studies of phase speciation of trace metals were conducted in Kao-ping river estuary in September 2001 and May 2002. Influence of seasonal variation, salinity and organic carbon content on the trace metal¡¦s phase speciation were of special interest. Water samples collected from four different sampling stations were analyzed for their contents which include salinity, pH value, dissolved oxygen, turbidity, total organic carbon and trace metals. Subsamples observed by cross-flow filtration treatment were further analyzed for the contents of total organic carbon and trace metals. The results showed that manganese has the highest concentration( 8.23 ~ 291.24 £gg/L ), followed by zinc( 2.83 ~ 5.89 £gg/L), nickel( 1.69 ~ 5.82 £gg/L ), copper( 1.75 ~ 4.71 £gg/L ), lead( 0.27 ~ 0.89 £gg/L ) and cadmium( 0.01 ~ 0.27 £gg/L ). Cadmium existed in particulate phase predominately. Copper existed in truly dissolved phase predominately. Particle and truly dissolved phase were the major species of zinc, nickel, manganese and lead. Percentage of all metals in colloidal fraction of the filter-passing pool were low( 9 ~ 16 % for Cu, 5 ~ 21 % for Zn, 4 ~ 30 % for Ni, 2 ~ 38 % for Mn, 5 ~ 30 % for Pb and 8 ~ 34 % for Cd ), they were found predominately in truly dissolved fraction. Effect of seasonal variation was not significant on the distribution of trace metals. Percentage of all truly dissolved metals increased with increasing salinity, however, percentage of particulate metals decreased with increasing salinity ( except for Zn ). Values of partition coefficients between colloids and true solution( Kc ) were considerably higher than those between particles and true solution( Kp ) for all trace metals indicate a high complexation capacity and binding intensity of colloidal organic matter.