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The major constraints to food production in West Africa are related to the lack of suitable lands. Consequently, farmers incorporate organic amendments and wastewater to improve their yields. Within some limits, such wastes enhance soil fertility and can improve its physical properties. However, the advantages of using organic waste as fertilizer and soil amendment should be assessed with possible environmental and toxicological impacts due to the potential presence of heavy metals. The objective of this study was to assess the effect of organic amendments on heavy metal distribution in soils and vegetables in market gardens in Senegal. Organic amendments and soils samples were collected from four sites in eastern and southern Senegal. Samples were analyzed for physicochemical properties including particle size, total heavy metals, carbon content, nutrients, and pH. A sequential extraction procedure was conducted to determine heavy metal sinks. Results showed that sites were sandy in nature, low to medium in organic carbon content (8300 to 36600 mg kg-1), and had pH ranging from 5 to 7.9. The sequential extraction procedure showed that metals were distributed in the more stable soil fractions: Fe-Mn oxide, organic and residual. The highest soil metal concentrations in soils were found in Pikine and Rufisque sites. Plant samples were collected from these two sites and analyzed for total metal content. Results showed that all metal concentrations in soils, organic amendments, and vegetables were within the safe limits proposed by the World Health Organization, with the exception of Cd, Pb and Zn levels in vegetables. / Master of Science

Master of Science / Department of Geology / Saugata Datta / More than 75 million people in the Bengal Delta of eastern India and Bangladesh are exposed to drinking water with dangerously high arsenic (As) concentrations; the worst case of environmental poisoning in human history. Despite recognition of dangers posed to chronic exposure to drinking water with elevated As, its biogeochemical cycle is inadequately constrained in groundwater flow systems due to its complex redox chemistry and microbially-mediated transformations. Arsenic concentrations in Bengal Delta sediments are comparable to global averages, but its highly heterogeneous spatial distribution (on scales of meters to kilometers) in sediments and groundwaters is poorly understood. Though many research efforts have targeted understanding this heterogeneity in Bangladesh, less work has been done in eastern India. Murshidabad (23°56.355‘N, 88°16.156‘E), an eastern district in West Bengal, India, where groundwaters are highly As-affected (~4000 μg/l), was chosen as our study area. Research objectives were: (1) characterize sediment cores (mineralogically, geochemically) and groundwaters (hydrochemically, isotopically) in areas with contrasting As concentrations—west (low-As) and east (high-As) of river Bhagirathi, a major distributary of Ganges flowing through the heart of Murshidabad; (2) describe and understand the extent of spatial variability, laterally and vertically, of dissolved As concentrations in shallow (< 60 m) aquifers, comparing sediment core chemistry to water chemistry; (3) identify source(s) of aquifer recharge and (4) role(s) of inorganic carbon within the aquifer to understand the bioavailability and mobilization of As from sediments to groundwaters. Mineralogical differences between high-As (grey) and low-As (orange-brown) sediments, were the presence of greater amounts of micas, Fe- and Mg-rich clays, amphiboles, carbonates, and apatite in high-As sediments; these were virtually absent from low-As sediments. In high-As areas, As was associated with amorphous and poorly-crystalline Fe-oxyhydroxide phases and labile (specifically-sorbed) phases, especially where Fe(II):Fe[subscript]T was high in the sediments. High-As groundwaters had high As(III):As[subscript]T, iron, bicarbonate, phosphate, and ammonium, and low concentrations of chloride and sulfate. Dry season precipitation was probably the main source of aquifer recharge; lighter values of [superscript]13C in dissolved inorganic carbon resulted from oxidation of natural organic matter. This study points to an idea that both microbially-mediated oxidation-reduction and competitive ion-exchange processes occurring in shallow aquifers of Murshidabad drive As mobilization and sequestration by aquifer sediments.

The Mae Tao watershed, northwestern Thailand, has become contaminated with cadmium (Cd) from the zinc mining activities area in the nearby Thanon-Thongchai mountains. Consumption of Cd-contaminated rice has led to documented human health impacts. The aim of this study was to clarify transfer pathways from creek and canal waters to the paddy field soils near Baan Mae Tao Mai village and to determine the relationship between Cd forms in the soil and uptake by rice plants. Soils, irrigation canal sediments and water samples were collected during the dry season and at the onset of the rainy season. Rice samples were collected at harvesting time and samples of soil fertiliser were also obtained. Water samples were filtered, ultrafiltered and analysed by ICP-MS whilst sub-samples of dried, ground soils and sediments were first subjected to micro-wave assisted acid digestion (modified US EPA method 3052). XPRD and SEM-EDX methods were used for mineralogical characterisation and selective chemical extractions have assisted in the characterisation of solid phase Cd associations. Transfer mainly occurred in association with particulate matter during flooding and channel dredging and, in contrast with many other studies, most of the soil Cd was associated with exchangeable and carbonate-bound fractions. Moreover, there was a significant positive relationship between soil total Cd and rice grain Cd (R2=0.715), but a stronger relationship between both the Tessier-exchangeable soil Cd and the BCR-exchangeable soil Cd and rice grain Cd (R2=0.895 and 0.861, respectively). Stable Isotope Exchange (gives isotopically exchangeable Cd - E value) is generally considered to provide a better measure of bioavailability. The results of this study showed that SIE gave values which significantly positive correlated with the Tessier exchangeable fraction. Biochar has a porous structure and acidic functional groups on its surface which give it a high capacity to affect heavy metal adsorption when added to soils. Biochar samples were produced from rice husk (RHC) and miscanthus (MC) since these are cheap and readily available materials in Thailand. Indeed rice husk char is already used for rice seed germination by local farmers. Evaluation of the chemical and physical properties of the chars showed that the lower temperature (350°C) chars had greater proportions of oxygen-containing functional groups than those produced at 700°C. Moreover the low temperature RHC had the greater cation exchange capacity than the MC produced at the same temperature. In abiotic feasibility tests, it was shown that RHC was more effective than MC at lowering soil available Cd. The former reduced the E values for the medium-Cd soils by 4.7% and 16.0% when 1% and 5% RHC, was added, respectively. From pot experiments, in medium-Cd soils, 1% and 5% RHC amendment showed the potential to decrease Cd uptake by rice roots. However, further work involving addition of a greater proportion of biochar with a higher number of replicates is needed to reach more robust conclusions.

Potentially harmful elements (PHEs) have been researched in a wide variety of disciplines, including pedology, chemistry, pollution science and medicine. Within the scientific community, emphasis has usually been placed on the toxic elements, such as cadmium, chromium, lead and arsenic, but rarely has there been consideration of interactions between PHEs, the sediment matrix and processes occurring in the sediments. Dredging of canals is needed for navigability purposes and consequently testing of dredged sediments (to assess whether sediments are hazardous) and landfilling can be costly for British Waterways facing constantly changing regulations and reduction in government grants. PHE mobility and availability in canal sediments can be affected by oxygen availability, pH and Redox. Remediation is thus becoming a priority for British Waterways to limit their operational costs. Zeolites, a type of remediation tool, have been widely studied in the past 30 years due to their attractive properties, such as molecular-sieving, high cation exchange capacities and their affinity for PHEs. The pilot study to investigate the efficiency of the clinoptilolite showed that there was a concentration difference between PHEs adsorbed by the clinoptilolite and the PHE concentration lost from the sediments from three sites in the West Midlands. Thorough characterisation of the sediments was needed to understand the speciation of the PHEs and the secondary processes occurring in the sediments. The different components of the sediments were analysed using various analytical methods, such as X-Ray Fluorescence spectroscopy (XRF), particle size and X-ray Diffraction (XRD) for the solid-inorganic phase, Ion Chromatography (IC) and Inductively Coupled Plasma-Optical Emissions Spectroscopy (ICP-OES) for the liquid phase (pore water), Gas Chromatography-Mass Spectrometry (GC-MS) and organic loss on ignition for the organic phase, pH and Redox for the electrochemistry of the sediments and Scanning Electron Microscope with Energy Dispersive X-Ray analysis (SEM-EDX) for microscopy and imaging. The British Geological Survey (BGS) sequential extraction method was used to investigate the different phases in the sediments. pH remained near neutral for all three sites and Redox remained anoxic. Organic contents for all three sites were around 30% and contained most of the polycyclic aromatic hydrocarbons considered hazardous. Pore water showed only high concentrations of sulphates but low concentrations of PHEs, suggesting PHEs were not mobile. Sequential extraction confirmed the other results showing that PHEs were mainly associated with stable phases, such as iron and manganese oxides or sulphides. The results have been taken into consideration to design a new remediation strategy to maximise efficiency of the zeolite.

O Sistema Cananéia-Iguape sofreu importantes alterações ambientais devido à abertura do canal do Valo Grande que o conectou ao rio Ribeira de Iguape. Com a intensa atividade de mineração ocorrida no Vale do Ribeira, a bacia do rio Ribeira foi afetada, atingindo o Sistema através desse canal. Diante desse cenário, o principal objetivo deste estudo foi avaliar a disponibilidade de Cu, Pb e Zn no Sistema Cananéia-Iguape, a partir do teor associado aos principais componentes dos sedimentos. Para estimar a contaminação química, o teor desses elementos foi comparado aos limites canadenses (ISQG e PEL), ao teor na região em período que antecedeu à intensa atividade de mineração e a valores de background (composição média dos folhelhos). Considerando-se os resultados de Cu e Zn, estima-se que em caso de remobilização, possivelmente, não representariam perigo às comunidades bióticas. Entretanto, o teor disponível de Pb excedeu os valores de comparação em várias estações, sugerindo atenção quanto à sua biodisponibilidade. Em geral, a região que mais favoreceu o acúmulo de metais foi o Mar Pequeno, provavelmente, devido às condições oceanográficas. Dados de geoquímica e de geocronologia de testemunhos possibilitaram reconhecer a inserção antrópica do Pb no Sistema durante o período de mineração. / The Cananéia-Iguape System suffered important changes due to the opening of Valo Grande Channel, which connect this System to the Ribeira de Iguape River. The mining activities in the Ribeira Valley affected the river basin, reaching this System through Valo Grande. The main goal of this study was to evaluate the availability of Cu, Pb and Zn in the Cananéia-Iguape System, based on the content associated with the main components of the sediments. In order to estimate chemical contamination, the content of these elements was compared to Canadians limits (ISQG and PEL), to the content of these metals in the region in period preceding to the intense mining activity and to the background values (shale average composition). The results for Cu and Zn indicated that in case of remobilization, they possibly would not represent a hazard to the biotic communities. However, the available content for Pb exceeded the comparative values at various stations, suggesting attention regarding its bioavailability. In general, the region that favored the most the accumulation of metals was Mar Pequeno, possibly due to oceanographic conditions. Data regarding geochemistry and geochronology of cores enable the observation of the insertion the Pb anthropogenic in the System during the mining period.

A sequential extraction method was used to determine which dominant sedimentary mineral phase was involved in phosphorus retention in the sediments of Lake Rotorua and to verify the importance of iron phases in the role as a phosphorus sink. The observed influence of the experimental conditions upon the extent of phosphate adsorption to various iron phases shows a considerable quantity of phosphorus is present in the reducible phase and in the residual mineral phase. The phosphorus associated with iron(III) oxide phases was released into solution under reducing conditions when ferric iron oxide/oxyhydroxides, including amorphous and poorly crystalline Fe(III) phases, were solubilized. The residual primary and secondary mineral phases remained stable in the sediments until they were exposed to extremely acidic media analogous to strongly reducing conditions. Manganese is not involved in phosphorus retention to the same extent as iron. Aluminium phases present were released from surface complexes with relative ease and also from mineral structures under the prevailing conditions. The results show a strong agreement between aluminium and phosphorus suggesting it is associated with various aluminium phases to some extent. The sediments of Lake Rotorua are rich in organic-bound P which is released when organic material is oxidized under conditions analogous to anaerobic degradation. The degradation of refractory organic material represents a significant source of phosphorus for incorporation into diagenetic minerals forming in oxic and anoxic layers of the sediment. Heavy liquid separation of the sediments concentrated the small quantities of dense minerals into a separate fraction and the presence of iron sulfides could be verified. Three density fractions obtained by this method separated the diatoms (d less than 2.6 g cm-3), the silicates (d greater than 2.6 less than 3.7 g cm-3) and the heavy minerals (d greater than 3.7 g cm-3) present in the sediment sample. In the heavy mineral phase spherulitic framboidal pyrite and rhombohedrial siderite were observed by scanning electron microscopy (SEM). Energy dispersive x-ray fluorescence (XRF) analysis of the framboidal pyrite detected significant fluorescence's for sulphur and iron. The elemental analysis of siderite characterised it as an iron-rich, non-sulfidic particle with no phosphorus fluorescence. Particles were also observed that had a variable morphology to the framboidal pyrite minerals but similar ratio of Fe to S in the XRF spectrum. It is likely they are other stable forms of iron sulfides or pyrites in various stages of diagenetic dissolution. Digestion of the three density fractions shows the heavy mineral phase is significantly enriched in sulfur and in iron confirming the presence of sulfides. The sulfide-forming trace metals are concentrating in the heavy mineral phase but a progressive enrichment of trace metals down core is not found in the results. Many of the trace elements show maximum concentrations in the Tarawera tephra. There is a good agreement between iron and phosphorus in both treatments that implies iron phases are the predominant phosphorus fixers in the sediments of Lake Rotorua. However the identity of the phosphorus sink could not be confirmed by SEM or XRF analysis of the heavy minerals. The most likely explanations for the observed concentrations of iron and phosphorus and enrichment in the heavy mineral fraction are the persistence of the highly insoluble crystalline iron oxyhydroxides (goethite) in reducing sediments or the formation of the reduced iron mineral vivianite. Considering the density of vivianite it would have being taken into the heavy fraction by default which would account for the enrichment demonstrated by the solution analysis.

This research was aimed to investigate the enhancement of electrokinetic (EK) remediation arsenate-contaminated soil by permeable reaction barrier (PRB). All experiments, which experimental parameters included the position, materials, and quantity of PRB, processing fluid types, potential gradients, and treatment time, were conducted in two types of EK systems. One was Pyrex glass cylindrical cells with dimension of 4.2 cm (£r) ¡Ñ 12 cm (L) and the other was a small pilot-scale modulus with dimension of 36cm (L) ¡Ñ18cm (W) ¡Ñ18cm cm (H). The PRBs were composed of four kinds of reaction materials, which included commercial zero valent iron (Fe(0)C), manufactured zero valent iron (Fe(0)M), commercial hydrous ferric oxide (FeOOHC), and manufactured hydrous ferric oxide (FeOOHM), mixed with ottawa sand in a ratio of 1:2,respectively, and installed in the anode, middle, and cathode side of the EK systems. For 5-day EK cylindrical cell tests, the results showed that the PRB installation would result in a lower electroosmosis permeability (Ke) and a higher removal efficiency of arsenate. The arsenate removal efficiency of EK system with PRB was in the range of 43.89-70.25%, which was 1.5~2.6 times greater than that without PRB, and the value of Ke was in the range of 4.30-12.61¡Ñ10-6 cm2/V-s. The soil pH after EK/PRB treatment was much closer to natural and more arsenate was collected in the anode reservoir. Moreover, the remediation performance of FeOOHC as PRB materials was much better than other materials. For EK pilot-scale modulus tests, it was shown that the removal efficiency of arsenate was effectively enhanced as improved experimental parameters and, however, led to increase the treatment cost. In EK modulus without PRB, the removal efficiency of arsenate, elctroosmosis permeability, and energy consumption were 27.76%, 3.30-5.39¡Ñ10-6 cm2/V-s, and 1724.81 kWh/m3, respectively. Furthermore, the treatment cost was NT 9583/m3. As increasing treatment time, graphite electrode, potential gradient, and quantity of PRB materials, the removal efficiency of arsenate increased to as high as 45.11-71.22% and the treatment cost also increased up to NT 24,800-57,730/m3. As investigated the binding form of arsenate with soil after EK/PRB treatment, it was found that the arsenate ¡Vsoil binding forms of Fe-Mn oxide bound, organically bound, and residual in the soil section behind the PRB were much easier transformed to the forms of exchangeable and carbonate bound. The transformation rate reached as high as 72.5% and it increased with treatment time. However, the Fe-Mn oxide bound was still the main binding form, 61.6-81.6%, in the soil section prior to the PRB. The removal mechanism of arsenate contaminated soil remediation was dominated by electromigration, electrolysis, and electroosmosis in EK system without PRB. And, in EK/PRB system, the removal of arsenate from soil was mainly resulted from adsorption rather than redox reaction by PRB. To sum up, the PRB can effectively enhance the electrokinetic remediation of arsenate contaminated soil by choosing the right PRB materials and operation parameters.

A seven-step sequential extraction scheme was used to track changes in operationally defined copper speciation during the composting of a mixture of grass clippings and sawdust originating from tanalised timber. Starting materials were either unamended or treated with differing amounts of soluble copper, using a copper acetate solution, and then composted in the laboratory. Results showed that at the start of the experiment over 80% of the copper present in the unamended materials occurred in forms not immediately available for plant uptake. However, composting processes enabled the release of this copper which then, over time, became more bioavailable. Large amounts of copper in the copper amended materials were initially detectable in all fractions except the residual one, but over time it was seen to move from all fractions to the EDTA extractable fraction, thought to determine organically complexed / chelatable metals (Amir, 2005). This continued until an equilibrium was reached and then the water and calcium nitrate extractable forms appeared to hold the excess. Copper as determined by these extracts would be available for plant uptake. In the second experiment, three different organic wastes (grass/sawdust, pig slurry/sawdust and sewage sludge cake/sawdust) to which copper had been added as copper acetate, sulphate or EDTA, were composted in the laboratory. Samples were taken at 0, 105 and 318 days and subjected to a range of analyses: copper by sequential extraction using two different extraction schemes, a chelating resin membrane (CRM) procedure and by XRF spectrometry; FTIR analysis for functional groups; total carbon, nitrogen and sulphur; pH, EC, NH4+ and NO3- nitrogen, COD, germination indices and optical properties of water extracts. Sequential extractions demonstrated clear changes in copper distribution amongst various fractions within the materials, with copper originally present in the materials being transferred from the oxidisable fractions to easily extractable (and hence potentially phytoavailable) fractions. Transfer of copper from available to less available fractions in copper amended materials was also seen with movement of copper within copper EDTA treated materials being the slowest of all. Initial amounts of copper in fraction 1 extracted from all samples determined the rate at which copper was transformed. CRM determined copper correlated strongly with copper from fraction 1 of the Tessier scheme, although changes over time did not correspond well. Other parameters measured indicated that that the material was maturing (decreases in C/N and polysaccharide functional groups). However, other results demonstrated that the composts were still immature and unstable. Such slow decomposition was attributed to the high lignin content of the materials. Nevertheless, immobilisation of potentially phytotoxic level of copper was still demonstrated. The usefulness of chelating resin membrane as a predictor of phytoavailable copper is also discussed.

O Sistema Cananéia-Iguape sofreu importantes alterações ambientais devido à abertura do canal do Valo Grande que o conectou ao rio Ribeira de Iguape. Com a intensa atividade de mineração ocorrida no Vale do Ribeira, a bacia do rio Ribeira foi afetada, atingindo o Sistema através desse canal. Diante desse cenário, o principal objetivo deste estudo foi avaliar a disponibilidade de Cu, Pb e Zn no Sistema Cananéia-Iguape, a partir do teor associado aos principais componentes dos sedimentos. Para estimar a contaminação química, o teor desses elementos foi comparado aos limites canadenses (ISQG e PEL), ao teor na região em período que antecedeu à intensa atividade de mineração e a valores de background (composição média dos folhelhos). Considerando-se os resultados de Cu e Zn, estima-se que em caso de remobilização, possivelmente, não representariam perigo às comunidades bióticas. Entretanto, o teor disponível de Pb excedeu os valores de comparação em várias estações, sugerindo atenção quanto à sua biodisponibilidade. Em geral, a região que mais favoreceu o acúmulo de metais foi o Mar Pequeno, provavelmente, devido às condições oceanográficas. Dados de geoquímica e de geocronologia de testemunhos possibilitaram reconhecer a inserção antrópica do Pb no Sistema durante o período de mineração. / The Cananéia-Iguape System suffered important changes due to the opening of Valo Grande Channel, which connect this System to the Ribeira de Iguape River. The mining activities in the Ribeira Valley affected the river basin, reaching this System through Valo Grande. The main goal of this study was to evaluate the availability of Cu, Pb and Zn in the Cananéia-Iguape System, based on the content associated with the main components of the sediments. In order to estimate chemical contamination, the content of these elements was compared to Canadians limits (ISQG and PEL), to the content of these metals in the region in period preceding to the intense mining activity and to the background values (shale average composition). The results for Cu and Zn indicated that in case of remobilization, they possibly would not represent a hazard to the biotic communities. However, the available content for Pb exceeded the comparative values at various stations, suggesting attention regarding its bioavailability. In general, the region that favored the most the accumulation of metals was Mar Pequeno, possibly due to oceanographic conditions. Data regarding geochemistry and geochronology of cores enable the observation of the insertion the Pb anthropogenic in the System during the mining period.