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Ecotoxicology and Environmental Safety Apr 2024Thiosulfate influences the bioreduction and migration transformation of arsenic (As) and iron (Fe) in groundwater environments. The aim of this study was to investigate...
Thiosulfate influences the bioreduction and migration transformation of arsenic (As) and iron (Fe) in groundwater environments. The aim of this study was to investigate the impact of microbially-mediated sulfur cycling on the bioreduction and interaction of As and Fe. Microcosm experiments were conducted, including bioreduction of thiosulfate, As(V), and Fe(III) by Citrobacter sp. JH012-1, as well as the influence of thiosulfate input at different initial arsenate concentrations on the bioreduction of As(V) and Fe(III). The results demonstrate that Citrobacter sp. JH012-1 exhibited strong reduction capabilities for thiosulfate, As(V), and Fe(III). Improving thiosulfate level promoted the bioreduction of Fe(III) and As(V). When 0, 0.1, 0.5, and 1 mM thiosulfate were added, Fe(III) was completely reduced within 9 days, 3 days, 1 day, and 0.5 days, simultaneously, 72.8%, 82.2%, 85.5%, and 90.0% of As(V) were reduced, respectively. The products of As(III) binding with sulfide are controlled by the ratio of As-S. When the initial arsenate concentration was 0.025 mM, the addition of thiosulfate resulted in the accumulation of soluble thioarsenite. However, when the initial arsenate level increased to 1 mM, precipitates of orpiment or realgar were formed. In the presence of both arsenic and iron, As(V) significantly inhibits the bioreduction of Fe(III). Under the concentrations of 0, 0.025, and 1 mM As(V), the reduction rates of Fe(III) were 100%, 91%, and 83%, respectively. In this scenario, the sulfide produced by thiosulfate reduction tends to bind with Fe(II) rather than As(III). Therefore, the competition of arsenic-iron and thiosulfate concentration should be considered to study the impact of thiosulfate on arsenic and iron migration and transformation in groundwater.
Topics: Iron; Arsenic; Arsenates; Thiosulfates; Oxidation-Reduction; Groundwater; Sulfides; Ferric Compounds
PubMed: 38479311
DOI: 10.1016/j.ecoenv.2024.116210 -
International Journal of Environmental... Feb 2023The emission and accumulation of toxic elements such as arsenic in various environmental compartments have become increasingly frequent primarily due to anthropogenic...
The emission and accumulation of toxic elements such as arsenic in various environmental compartments have become increasingly frequent primarily due to anthropogenic actions such as those observed in agricultural, industrial, and mining activities. An example of environmental arsenic contamination in Brazil exists in the city of Paracatu, MG, due to the operation of a gold mine. The aim of this work is to evaluate the routes and effects of arsenic contamination in environmental compartments (air, water, and soil) and environmental organisms (fish and vegetables) from mining regions as well as the trophic transfer of the element for a risk assessment of the population. In this study, high levels of arsenic were found in the waters of the Rico stream ranging from 4.05 µg/L during the summer season to 72.4 µg/L during the winter season. Moreover, the highest As concentration was 1.668 mg kg in soil samples, which are influenced by seasonal variation and by proximity to the gold mine. Inorganic and organic arsenic species were found above the allowed limit in biological samples, indicating the transfer of arsenic found in the environment and demonstrating a great risk to the population exposed to this area. This study demonstrates the importance of environmental monitoring to diagnose contamination and encourage the search for new interventions and risk assessments for the population.
Topics: Arsenic; Arsenicals; Mining; Environmental Monitoring; Soil; Gold; Soil Pollutants
PubMed: 36901297
DOI: 10.3390/ijerph20054291 -
The Science of the Total Environment Jun 2022Arsenic is common toxic contaminant, but tracking its mobility through submerged soils is difficult because microscale processes dictate its speciation and affinity to...
Arsenic is common toxic contaminant, but tracking its mobility through submerged soils is difficult because microscale processes dictate its speciation and affinity to minerals. Analyses on environmental dissolved arsenic (As) species such as arsenate and arsenite currently require highly specialized equipment and large sample volumes. In an effort to unravel arsenic dynamics in sedimentary porewater, a novel, highly sensitive, and field-usable colorimetric assay requiring 100 μL of sample was developed. Two complementary protocols are presented, suitable for sub-micromolar and micromolar ranges. Phosphate is a main interfering substance, but can be separated by measuring phosphate and arsenate under two different acidities. Arsenite is assessed by oxidation of arsenite to arsenate in the low-acidity reagent. Optimization of the protocol and spectral analyses resulted in elimination of various interferences (silicate, iron, sulfide, sulfate), and the assay is applicable across a wide range of salinities and porewater compositions. The new assay was used to study As mobilization processes through the soil of a contaminated brook. Water column sources of arsenic were limited to a modest input by a groundwater source along the flow path. In one of the sites, the arsenite and arsenate porewater profiles showed active iron-driven As redox cycling in the soil, which may play a role in arsenic mobilization and releases arsenite and arsenate into the brook water column. Low arsenic concentrations downstream from the source sites indicated arsenic retention by soil and dilution with additional sources of water. Arsenic is thus retained by the Bossegraben before it merges with larger rivers.
Topics: Arsenates; Arsenic; Arsenites; Colorimetry; Iron; Phosphates; Soil; Water
PubMed: 35231514
DOI: 10.1016/j.scitotenv.2022.154155 -
Archives of Toxicology Aug 2010Arsenic has been a recognized contaminant and toxicant, as well as a medicinal compound throughout human history. Populations throughout the world are exposed to arsenic... (Review)
Review
Arsenic has been a recognized contaminant and toxicant, as well as a medicinal compound throughout human history. Populations throughout the world are exposed to arsenic and these exposures have been associated with a number of human cancers. Not much is known about the role of arsenic as a human carcinogen and more recently its role in non-cancerous diseases, such as cardiovascular disease, hypertension and diabetes mellitus have been uncovered. The health effects associated with arsenic are numerous and the association between arsenic exposure and human disease has intensified the search for molecular mechanisms that describe the biological activity of arsenic in humans and leads to the aforementioned disease states. Arsenic poses a human health risk due in part to the regulation of cellular signal transduction pathways and over the last few decades, some cellular mechanisms that account for arsenic toxicity, as well as, signal transduction pathways have been discovered. However, given the ubiquitous nature of arsenic in the environment, making sense of all the data remains a challenge. This review will focus on our knowledge of signal transduction pathways that are regulated by arsenic.
Topics: Arsenates; Arsenic Poisoning; Arsenites; Carcinogens, Environmental; Diabetes Mellitus; Environmental Exposure; Environmental Pollution; Genetic Predisposition to Disease; Humans; Reactive Oxygen Species; Signal Transduction
PubMed: 20502880
DOI: 10.1007/s00204-010-0554-4 -
Environmental Microbiology Apr 2020Mining operations produce large quantities of wastewater. At a mine site in Northern Finland, two natural peatlands are used for the treatment of mining-influenced...
Mining operations produce large quantities of wastewater. At a mine site in Northern Finland, two natural peatlands are used for the treatment of mining-influenced waters with high concentrations of sulphate and potentially toxic arsenic (As). In the present study, As removal and the involved microbial processes in those treatment peatlands (TPs) were assessed. Arsenic-metabolizing microorganisms were abundant in peat soil from both TPs (up to 10 cells g ), with arsenate respirers being about 100 times more abundant than arsenite oxidizers. In uninhibited microcosm incubations, supplemented arsenite was oxidized under oxic conditions and supplemented arsenate was reduced under anoxic conditions, while little to no oxidation/reduction was observed in NaN -inhibited microcosms, indicating high As-turnover potential of peat microbes. Formation of thioarsenates was observed in anoxic microcosms. Sequencing of the functional genemarkers aioA (arsenite oxidizers), arrA (arsenate respirers) and arsC (detoxifying arsenate reducers) demonstrated high diversity of the As-metabolizing microbial community. The microbial community composition differed between the two TPs, which may have affected As removal efficiencies. In the present situation, arsenate reduction is likely the dominant net process and contributes substantially to As removal. Changes in TP usage (e.g. mine closure) with lowered water tables and heightened oxygen availability in peat might lead to re-oxidation and re-mobilization of bound arsenite.
Topics: Arsenates; Arsenic; Arsenites; Biodegradation, Environmental; Groundwater; Microbiota; Mining; Oxidation-Reduction; Oxygen; Soil; Soil Microbiology; Wastewater; Water Pollutants, Chemical
PubMed: 31984582
DOI: 10.1111/1462-2920.14922 -
Journal of Pharmaceutical and... Oct 2023Arsenic-containing lipids, also named arsenolipids (AsLs), are a group of organic compounds usually found in a variety of marine organisms such as fish, algae,... (Review)
Review
Arsenic-containing lipids, also named arsenolipids (AsLs), are a group of organic compounds usually found in a variety of marine organisms such as fish, algae, shellfish, marine oils, and microorganisms. Numerous AsLs have been recognised so far, from simple compounds such as arsenic fatty acids (AsFAs), arsenic hydrocarbons (AsHCs), and trimethylarsenio fatty alcohols (TMAsFOHs) to more complex arsenic-containing species, of which arsenophospholipids (AsPLs) are a case in point. Mass spectrometry, both as inductively coupled plasma (ICP-MS) and liquid chromatography coupled by an electrospray source (LC-ESI-MS), was applied to organic arsenicals playing a key role in extending and refining the characterisation of arsenic-containing lipids in marine organisms. Herein, upon the introduction of a systematic notation for AsLs and a brief examination of their toxicity and biological role, the most relevant literature concerning the characterisation of AsLs in marine organisms, including edible ones, is reviewed. The use of both ICP-MS and ESI-MS coupled with reversed-phase liquid chromatography (RPLC) has brought significant advancements in the field. In the case of ESI-MS, the employment of negative polarity and tandem MS analyses has further enhanced these advancements. One notable development is the identification of the m/z 389.0 ion ([AsCHOP]) as a diagnostic product ion of AsPLs, which is obtained from the fragmentation of the deprotonated forms of AsPLs ([M - H]). The pinpointing product ions offer the possibility of determining the identity and regiochemistry of AsPL side chains. Advanced MS-based analytical methods may contribute remarkably to the understanding of the chemical diversity characterising the metalloid As in natural organic compounds of marine organisms.
Topics: Animals; Arsenic; Chromatography, High Pressure Liquid; Arsenicals; Mass Spectrometry; Fatty Acids
PubMed: 37579719
DOI: 10.1016/j.jpba.2023.115628 -
MBio Nov 2017Long-term exposure to trace levels of arsenic (As) in shallow groundwater used for drinking and irrigation puts millions of people at risk of chronic disease. Although...
Long-term exposure to trace levels of arsenic (As) in shallow groundwater used for drinking and irrigation puts millions of people at risk of chronic disease. Although microbial processes are implicated in mobilizing arsenic from aquifer sediments into groundwater, the precise mechanism remains ambiguous. The goal of this work was to target, for the first time, a comprehensive suite of state-of-the-art molecular techniques in order to better constrain the relationship between indigenous microbial communities and the iron and arsenic mineral phases present in sediments at two well-characterized arsenic-impacted aquifers in Bangladesh. At both sites, arsenate [As(V)] was the major species of As present in sediments at depths with low aqueous As concentrations, while most sediment As was arsenite [As(III)] at depths with elevated aqueous As concentrations. This is consistent with a role for the microbial As(V) reduction in mobilizing arsenic. 16S rRNA gene analysis indicates that the arsenic-rich sediments were colonized by diverse bacterial communities implicated in both dissimilatory Fe(III) and As(V) reduction, while the correlation analyses involved phylogenetic groups not normally associated with As mobilization. Findings suggest that direct As redox transformations are central to arsenic fate and transport and that there is a residual reactive pool of both As(V) and Fe(III) in deeper sediments that could be released by microbial respiration in response to hydrologic perturbation, such as increased groundwater pumping that introduces reactive organic carbon to depth. The consumption of arsenic in waters collected from tube wells threatens the lives of millions worldwide and is particularly acute in the floodplains and deltas of southern Asia. The cause of arsenic mobilization from natural sediments within these aquifers to groundwater is complex, with recent studies suggesting that sediment-dwelling microorganisms may be the cause. In the absence of oxygen at depth, specialist bacteria are thought able to use metals within the sediments to support their metabolism. Via these processes, arsenic-contaminated iron minerals are transformed, resulting in the release of arsenic into the aquifer waters. Focusing on a field site in Bangladesh, a comprehensive, multidisciplinary study using state-of-the-art geological and microbiological techniques has helped better understand the microbes that are present naturally in a high-arsenic aquifer and how they may transform the chemistry of the sediment to potentially lethal effect.
Topics: Arsenates; Arsenic; Arsenites; Bacteria; Bangladesh; Biota; Cluster Analysis; DNA, Ribosomal; Geologic Sediments; Groundwater; Iron; Phylogeny; RNA, Ribosomal, 16S; Sequence Analysis, DNA
PubMed: 29184025
DOI: 10.1128/mBio.01326-17 -
Epigenomics Feb 2010Arsenic is a nonmutagenic human carcinogen that induces tumors through unknown mechanisms. A growing body of evidence suggests that its carcinogenicity results from... (Review)
Review
Arsenic is a nonmutagenic human carcinogen that induces tumors through unknown mechanisms. A growing body of evidence suggests that its carcinogenicity results from epigenetic changes, particularly in DNA methylation. Changes in gene methylation status, mediated by arsenic, have been proposed to activate oncogene expression or silence tumor suppressor genes, leading to long-term changes in the activity of genes controlling cell transformation. Mostly descriptive, and often contradictory, studies have demonstrated that arsenic exposure is associated with both hypo- and hyper-methylation at various genetic loci in vivo or in vitro. This ambiguity has made it difficult to assess whether the changes induced by arsenic are causally involved in the transformation process or are simply a reflection of the altered physiology of rapidly dividing cancer cells. Here, we discuss the evidence supporting changes in DNA methylation as a cause of arsenic carcinogenesis and highlight the strengths and limitations of these studies, as well as areas where consistencies and inconsistencies exist.
Topics: Animals; Arsenates; Arsenic; DNA Methylation; Epigenesis, Genetic; Female; Humans; Methyltransferases; Mice; Neoplasms; Nutritional Physiological Phenomena; Oxidation-Reduction; Oxidative Stress; Pregnancy; Prenatal Exposure Delayed Effects
PubMed: 20514360
DOI: 10.2217/epi.09.45 -
Applied and Environmental Microbiology Jul 2019The reduction of arsenate [As(V)] to arsenite [As(III)] by dissimilatory As(V)-reducing bacteria, such as spp., may play a significant role in arsenic release from...
The reduction of arsenate [As(V)] to arsenite [As(III)] by dissimilatory As(V)-reducing bacteria, such as spp., may play a significant role in arsenic release from anaerobic sediments into groundwater. The biochemical and molecular mechanisms by which these bacteria cope with this toxic element remain unclear. In this study, the expression of several genes involved in arsenic respiration () and resistance () was determined using sp. strain OR-1, the only cultured strain capable of As(V) respiration. In addition, proteins expressed differentially under As(V)-respiring conditions were identified by semiquantitative proteomic analysis. Dissimilatory As(V) reductase (Arr) of strain OR-1 was localized predominantly in the periplasmic space, and the transcription of its gene () was upregulated under As(V)-respiring conditions. The transcription of the detoxifying As(V) reductase gene () was also upregulated, but its induction required 500 times higher concentration of As(III) (500 μM) than did the gene. Comparative proteomic analysis revealed that in addition to the Arr and Ars proteins, proteins involved in the following processes were upregulated under As(V)-respiring conditions: (i) protein folding and assembly for rescue of proteins with oxidative damage, (ii) DNA replication and repair for restoration of DNA breaks, (iii) anaplerosis and gluconeogenesis for sustainable energy production and biomass formation, and (iv) protein and nucleotide synthesis for the replacement of damaged proteins and nucleotides. These results suggest that strain OR-1 copes with arsenic stress by orchestrating pleiotropic processes that enable this bacterium to resist and actively metabolize arsenic. Dissimilatory As(V)-reducing bacteria, such as spp., play significant roles in arsenic release and contamination in groundwater and threaten the health of people worldwide. However, the biochemical and molecular mechanisms by which these bacteria cope with arsenic toxicity remain unclear. In this study, it was found that both respiratory and detoxifying As(V) reductases of a dissimilatory As(V)-reducing bacterium, sp. strain OR-1, were upregulated under As(V)-respiring conditions. In addition, various proteins expressed specifically or more abundantly in strain OR-1 under arsenic stress were identified. Strain OR-1 actively metabolizes arsenic while orchestrating various metabolic processes that repair oxidative damage caused by arsenic. Such information is useful in assessing and identifying possible countermeasures for the prevention of microbial arsenic release in nature.
Topics: Arsenates; Arsenic; Arsenites; Bacterial Proteins; Gene Expression Regulation, Bacterial; Genes, Bacterial; Geobacter; Geologic Sediments; Oxidation-Reduction
PubMed: 31101608
DOI: 10.1128/AEM.00763-19 -
Environmental Toxicology and Chemistry Jun 2022Historical use of lead arsenate as a pesticide in former orchards of eastern Washington State (USA) has resulted in legacy lead (Pb) and arsenic (As) soil contamination....
Historical use of lead arsenate as a pesticide in former orchards of eastern Washington State (USA) has resulted in legacy lead (Pb) and arsenic (As) soil contamination. However, the impacts on plant growth in soils with residual Pb and As contamination have not yet been quantified. To this end, a comparative study of plant growth impacts was performed for native bluegrass (Poa secunda), invasive cheatgrass (Bromus tectorum), and buttercrunch lettuce (Lactuca sativa). Using standard plant growth protocols, germination frequency and biomass growth were measured over a wide range of Pb and arsenate concentrations, with maximum concentrations of 3400 and 790 mg kg for Pb and As, respectively. Results indicated that only the biomass growth for all species decreased in soils with the highest concentrations of Pb and As in the soil, with no impacts on soils with lower residual Pb and arsenate concentrations. No impact on percentage of germination was observed at any soil concentration. These results can be used to determine site-specific soil screening levels for use in ecological risk assessments for Pb and arsenate in soils. Environ Toxicol Chem 2022;41:1459-1465. © 2022 Battelle Memorial Institute. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.
Topics: Arsenates; Arsenic; Lead; Soil; Soil Pollutants
PubMed: 35262236
DOI: 10.1002/etc.5325