The contamination of groundwater by arsenic is currently a major concern in Bangladesh. Arsenic in groundwater was first detected in 1993 following reports of many people suffering from arsenical diseases. Further investigations showed the extent of the problem with large areas of the country's water supply being affected and millions of people at serious risk of arsenic poisoning. Technology for arsenic removal from water already exists. However, the socioeconomic conditions which prevail in Bangladesh, do not permit implementation of this type of technology on grounds of cost. The main objective of this study was to develop a low cost technique for the removal of arsenic from contaminated groundwater using the naturally occurring iron, which is another water quality constraint in Bangladesh. The approach was to form arsenic-iron complexes by coprecipitation and adsorption of arsenic on iron. It has been demonstrated that provided the iron levels are sufficiently high (say >_ 1.2 mg/1), simple shaking of a container and allowing the arsenic-iron complex to settle out for 3 days could reduce the concentration of arsenic from 0.10 mg/l to Bangladesh standard (0.05 mg/1). In experimental program, As(III) form of arsenic was used as this form is more likely to be present in groundwater. From laboratory studies, it was shown that the removal rate was largely controlled by the Fe/As ratio, pH and the As concentration. Arsenic removal increases with increasing Fe/As ratio and is favoured by increasing pH in the range of 5 to 8. Separation of the precipitates was achieved by settlement. Following prolonged settlement, it was found that arsenic removal could exceed the removal achieved by filtration through a 0.45 μm filter paper. The experiments demonstrated that about 77% arsenic removal could be achieved from water containing 0.2 mg/l As(III), 4.0 mg/1 Fe at pH 7.5 by manual flocculation (1 min manual mixing) and 3 days settlement. The use of ordinary charcoal, which is cheap and easily available, was investigated for removal of arsenic and was found to be ineffective. From maps of the known distributions of As, Fe and pH, it was evident that 63% of the area in Bangladesh complied with the Bangladesh standard for arsenic. By interpreting the maps and applying the potential removal by coprecipitation-adsorption and settlement technique, it was estimated that a further 8% of area would comply with the Bangladesh standard freeing an additional 7 million people from arsenic contamination.

This thesis studies the Shubnikov-de Haas effect in arsenic.

The focus of this research was on the xylem sap of cucumber plants during arsenic stress. A better understanding of the uptake and translocation mechanisms within the plant is crucial for the assessment of arsenic impact on fruits and cereals of the human diet. The impact of four different arsenic species (As(III), As(V), DMA(V) and MMA(V)) on the xylem sap production and their respective concentration in the xylem was studied. Cucumbers behave similar under arsenic stress as other non-tolerant plant species regarding uptake and translocation; high inorganic uptake into the roots but higher translocation of methylated arsenic into shoots and leafs. In plant physiology spectroscopic techniques coupled to separation techniques are usually deployed for metal(loid) studies. These techniques are well known and used. However, their robustness might be a disadvantage when it comes to biological dynamic systems. To overcome this, voltammetry was used as a new technique for xylem sap and hydroponic nutrient solution analysis. Voltammetry was used to analyse the nutrient solution of hydroponically grown cucumbers and their xylem sap during arsenate treatment in order to detect weak arsenite complexes. Furthermore, assessment of complexation capacities and ligand concentrations were performed. In order to identify possible arsenite ligands, xylem sap was analyzed by metabolomics, a recently developed tool for analyzing biological samples. Here, xylem sap samples of arsenate stressed plants were compared with control plants to identify organic compounds which are up- or down-regulated due to arsenate stress. Nine m/z values were identified to be up- or down-regulated under arsenate stress of which five were used for identification. LC-MS spectra obtained by high-resolution LC-MS were used for identification of organic compounds regulated due to arsenate stress. Isoleucine was found to be down-regulated under arsenate stress.

Thesis advisor: Rudolph Hon / A groundwater plume beneath a capped landfill in north-central Massachusetts contains dissolved arsenic concentrations exceeding 10,000 ppb at several locations. The landfill closed in the early 1990's and contains minimally documented solid waste materials deposited over the course of nearly a century. The source(s), fate, and transport of arsenic in the landfill aquifer have been studied extensively over the past decade; however, the source and pathways of arsenic are not yet fully defined. The primary source of arsenic likely involves a combination of the landfill waste material, the peat, the underlying overburden sequence, and/or bedrock minerals. Arsenic mobilization is most likely assisted by reducing conditions created by the decomposition of organic materials within the landfill and underlying peat present prior to the initiation of waste disposal. Another possibility is an arsenic-bearing groundwater discharging from the underlying bedrock from the oxidation of naturally occurring sulfides. Aqueous arsenic species, including inorganic arsenite [As(III), As(OH)3] and arsenate [As(V), AsO(OH)3], and organic monomethylarsonic acid [MMA(V), CH3AsO(OH)2] and dimethylarsinic acid [DMA(V), (CH3)2AsO(OH)], provide information as to where the arsenic is primarily originating from and how it is transported through the aquifer. Furthermore, the analysis of major ions, metals, and groundwater parameters from different zones of the landfill with varying arsenic concentrations will aid in the delineation of probable arsenic sources, the mobilization processes, and arsenic transport modes within the aquifer. A more complete conceptual site model with respect to arsenic speciation and groundwater chemistry will lead to a better understanding of geochemical processes within and beneath the landfill waste pile and also assist with future remediation of the aquifer. Using arsenic speciation and groundwater chemistry data, it was determined that although all four potential arsenic sources likely contribute to the total arsenic concentrations, the overall contribution from the landfill material, peat layer, and bedrock is minimal relative to the iron-oxyhydroxides coated on the sands particles throughout the aquifer which acts as the primary arsenic source. Oxidation-reduction potential and dissolved oxygen are the controlling factors in relation to mobilization and transport of arsenic species from aquifer features and an understanding of these processes at the local level can be further applied to global-scale arsenic contamination. / Thesis (MS) — Boston College, 2013. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Geology and Geophysics.

Arsenic is commonly known as poison and contaminant from both natural and anthropogenic sources. However, it is mostly unknown to the general public that there is a wide variety of arsenic species, which can either be toxic or benign. Currently, public interest and legislation focuses on inorganic species of arsenic. However, there is increasing evidence for the toxic capabilities of organic arsenic containing compounds, especially arsenolipids. These compounds are commonly found in oils derived from marine animals, such as fish oil or krill oil, which are increasingly popular as food supplements due to their high omega-3 fatty acid content. Other samples of (mostly) marine origin have also been shown to contain arsenolipids. In this thesis, organ samples from a stranded pod of long-finned pilot whales (Globicephala melas) were investigated for their arsenolipid content. This was achieved by coupling reversed phase high performance liquid chromatography (RP-HPLC) with a combination of inductively coupled plasma mass spectrometry (ICP-MS) and electrospray ionisation mass spectrometry (ESI-MS). Using these techniques, it is shown that arsenic can accumulate with age in mammalian brains in the form of arsenic containing phospholipids (AsPL). In contrast to inorganic arsenic and due to their lipophilic nature, lipophilic arsenic containing compounds are thus able to pass the blood-brain barrier. In a second part of the thesis, a previously unknown type of lipophilic arsenic containing compounds has been identified in strains of Streptomyces bacteria. This compound was shown to feature a non-methylated arsenic moiety, which is a structural feature that has not been reported for any of the previously known arsenolipids.

Arsenic trioxide is a clinically effective treatment for the disease acute promyelocytic leukaemia (APL) which is caused by the chromosomal translocation t(15;17) which fuses the promyelocytic leukaemia (PML) protein to the retinoic receptor alpha (RARa). The PML-RARa oncoprotein disrupts normal retinoic acid signalling and the function of PML nuclear bodies (PML-NBs), subnuclear protein complexes with roles in control of apoptosis and cellular senescence. Treatment with arsenic induces rapid post translational modification of PML and with the small ubiquitin like modifier (SUMO). SUMO modification of PML recruits the SUMO targeted ubiquitin E3 ligase RNF4 via four SUMO interaction motifs within the N-terminal region of RNF4. PML is then ubiquitylated and targeted for proteasomal degradation. In APL, these events trigger degradation of PML-RARa, curing the disease. To further investigate the process of arsenic induced degradation of PML, a high content siRNA screen was designed to monitor the fate of a YFP linked version of PML after siRNA mediated knockdown of components of the ubiquitin system and arsenic treatment. RNF4 depletion prior to arsenic treatment prevented PML degradation and resulted in accumulation of PML in large, bright PML-NBs. This was used as a positive control. A library of siRNAs targeting 1067 gene products were screened to identify those which perturbed the process of arsenic mediated degradation of PML, and those which affected the stability of PML in untreated cells. A number of putative hits were identified. Depletion of the cullin RING ligase scaffold CUL3, and the NEDD8 E3 ligase DCUN1D1 resulted in striking accumulation of PML, suggesting PML may be a substrate of a CUL3 RING ligase complex. Further experiments using the inhibitor of neddylation, MLN4924 support this hypothesis. PML is expressed as a various isoforms which encode a unique C-terminal region, due to alternative splicing. The second part of this study investigated the role of this variable C-terminal region in the response of the six major PML isoforms to arsenic treatment. Using a system in which only a single eYFP-linked PML isoform is expressed, differences in the localisation of PML isoforms following arsenic treatment were identified, with PML I, II and VI found to accumulate in the cytoplasm following arsenic treatment, whereas PML III, IV and V did not. A high content imaging assay identified PML V as the isoform most readily degraded following arsenic treatment, and PML IV as relatively resistant to degradation. Using siRNA it was demonstrated that arsenic induced degradation of all PML isoforms is dependent on the ubiquitin E3 ligase RNF4. Intriguingly, depletion of RNF4 resulted in marked accumulation of PML V, suggesting this isoform is an optimal substrate for RNF4. Thus the variable C-terminal domain influences the rate and location of degradation of PML isoforms following arsenic treatment.

This dissertation combines field data, laboratory experiments, and mathematic models to (1) predict the probability of groundwater arsenic (As) contamination caused by geogenic sources and processes in shallow aquifers of the Mississippi Delta in southern Louisiana, (2) study the role microbes play in controlling As mobilization from sediments to groundwaters, and (3) simulate As mobilization and transport caused by changing redox conditions and groundwater geochemistry along a flow path within the southeastern Chicot aquifer in southern Louisiana. A model based on surface hydrology, soil properties, geology, and sedimentary deposition environments predicts that the Holocene shallow aquifers in southern Louisiana are at high risk of As contamination. Sediment incubation and pore-water chemistry suggest that microbes play a key role in mobilizing As from sediments by reductive dissolution of As-bearing Fe(III) oxides/oxyhydroxides. Finally, groundwater samples were collected along a 10 km flow path in the southeastern Chicot aquifer to determine groundwater geochemical parameters and to simulate reactive transport of Fe and As species along the studied flow path. The model well captures the general trends of Fe(II) and As(III) concentrations along the studied flow path and the close correspondence between Fe(II) and As(III) of the both measured and model predicted As(III) and Fe(II) concentrations support the hypothesis that microbially mediated reductive dissolution of As-bearing Fe(III) oxides/oxyhydroxides is the primary mechanism causing As mobilization from sediments to the shallow reducing groundwaters of the Mississippi Delta in southern Louisiana. / 1 / NINGFANG YANG

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Two related techniques, based upon ion-exchange solid phase extraction, have been developed for the determination of arsenic speciation. The inorganic arsenic species arsenite (As(III)) and arsenate (As(V)) are separated by anion-exchange and detected with graphite furnace atomic absorption spectrophotometry (GFAAS) with a nickel matrix modifier. The first separation technique, which is based on a published method, utilizes a strong anion-exchange resin in a column format. The method was refined to achieve a cleaner and more rapid separation of the As species. In the second separation technique, the recently available Empore[superscript TM] anion-extraction disks are used. In both cases, rapid separations of several samples are achieved with the use of a vacuum manifold. The simplicity of the separation techniques allows them to be applied in the field which eliminates potential problems due to sample storage. In the pH range of most natural water samples (5-9), As(III) exists as a neutral species which is not retained by the resin, while As(V) exists as a monovalent or divalent species which are subsequently retained by the resin. The two arsenic species are collected in 3 to 4 fractions with As(III) appearing in the first two fractions. The As(V) species is eluted from the resin with 0.1 M HCl and collected in the last one or two fractions. Percent recoveries for each species range from 94 to 99%. The detection limit for each species with GFAAS is 2 ��g/L. The speciation techniques were used successfully in several applications. First, the resin technique was used to monitor the oxidation of As(III) by 0���, H���0���, and ��-Mn0���. The technique was also used to monitor the reduction of As(V) by Fe(II) and in solutions containing combinations of Fe(II), Fe(III), and a scorbic acid. Second, the resin technique was used to monitor the redox behavior of arsenic in soil slurries in bio-reactor systems. Upon spiking the soil slurry to a level of 500 ��g/L As(V), 80 to 90% of the As(V) was immediately adsorbed, presumably to hydrous Fe(III) oxides. In general, as conditions became more reducing, total soluble arsenic increased as a result of either abiotic or biotic reduction of the As(V) to the more soluble As(III). Third, the disk technique was applied in the field to determine arsenic speciation in creek water at Sutter Creek, Ca., where homes are built upon a large pile of mine tailings containing arsenic. In the creek water, no As(III) was detected but As(V) was detected at a level of 8 ��g/L. Fourth and finally, the resin technique was used to determine arsenic speciation when a sample of the mine tailings was placed in a reactor and combined with a soil slurry thus simulating a flooded condition. As conditions became more reducing, up to 800 ��g/L As was detected in solution with As(III) accounting for almost 90% of total soluble species. Also presented here is an investigation of zinc amalgam as a reducing agent for Cr(III) and selected redox indicators. Zinc amalgam, in a column format, also known as the classic Jones Reductor, provides an efficient means for production of Crap and reduced forms of various redox indicators. Finally, the reduction capabilities of Ti(III) citrate and zinc amalgam were compared. / Graduation date: 1996

Arsenic is a widespread environmental contaminant whose toxicity depends on its valence and its chemical form. Arsenic species have been typically determined using high pressure liquid chromatography coupled to inductively coupled plasma mass spectrometry (HPLC-ICPMS), however ICPMS cannot differentiate the co-eluting arsenic species. This thesis explores the use of electrospray mass spectrometry (ESI-MS) with HPLC separation for arsenic speciation and demonstrates applications of various HPLC-ESI-MS methods for the determination of toxicologically and environmentally relevant arsenic compounds. The trivalent arsenicals, such as arsenite (AsIII) and its metabolites monomethylarsonous acid (MMAIII) and dimethylarsinous acid (DMAIII) are not easily detected using ESI-MS due to their poor ionizability, but they are known to have high affinity for thiols. Thus, the easily ionizable dithiol dimercaptosuccinic acid (DMSA) was used to derivatize the trivalent arsenicals prior to ESI-MS. Selection of the derivatizing reaction was based on studies of arsenic-thiol interactions. An HPLC-ESI-MS/MS method was developed for the detection of derivatized AsIII, DMAIII and MMAIII and underivatized arsenate (AsV), monomethylarsonic acid (MMAV) and dimethylarsinic acid (DMAV), and was used to analyze multiple types of samples including urine, plasma and water. One set of groundwater samples from the site of a former pesticide manufacturing plant contained concentrations of MMAIII as high as 3.9-274 mg/L, the highest ever observed in the environment. Another HPLC-ESI-MS/MS method, without the need of derivatization, was developed for the detection of the toxic thio-arsenicals dimethylmonothioarsinic acid (DMMTAV) and monomethylmonothioarsonic acid (MMMTAV). DMMTAV was present in rat plasma and human urine and both DMMTAV and MMMTAV were detected in rat urine. The method of derivatization and ESI-MS/MS detection was extended to the speciation of inorganic SbIII and SbV. The use of the HPLC-ESI-MS/MS method using DMPS derivatization enabled the speciation of SbIII and SbV in water samples from mine waste.