ORCID Profile
0000-0002-7484-6696
Current Organisation
University of Manchester
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Publisher: Elsevier BV
Date: 10-2014
Publisher: Springer Science and Business Media LLC
Date: 10-07-2023
DOI: 10.1007/S12403-023-00581-W
Abstract: Although there are an increasing number of artificial intelligence/machine learning models of various hazardous chemicals (e.g. As, F, U, NO 3 − , radon) in environmental media (e.g. groundwater, soil), these most commonly use arbitrarily selected cutoff criteria to balance model specificity and sensitivity. This results in models of hazard distribution that, whilst often of considerable interest and utility, are not designed to optimize cost benefits of the mitigation of those hazards. In this case study, building upon recent machine learning modelling of the geographical distribution of groundwater arsenic in India, we show that the use of objective cost-informed criteria not only results in (i) different cutoff values for the classification of areas as of high or low groundwater arsenic hazard but also, more importantly, (ii) a reduction of overall potential (mitigation + testing + health impacts) costs. Further, we show that the change in optimal cutoff values and the reduction in overall costs vary from state to state depending upon locally specific classification-dependent costs, the prevalence of high arsenic groundwaters, the heterogeneity of the distribution of those high arsenic groundwaters, and the extent to which inhabitants are exposed to the hazard. It follows more generally that using cost-optimized criteria will result in different, more objective, and more cost-relevant appropriate balances being made between specificity and sensitivity in modelling environmental hazard distribution in different regions. This indicates also the utility of developing machine learning models at an appropriate local (e.g. country, state, district) scale rather than more global scales in order to better inform local-scale mitigation strategies.
Publisher: Mineralogical Society
Date: 02-2008
DOI: 10.1180/MINMAG.2008.072.1.441
Abstract: In many areas of south and south-eastern Asia, concentrations of As in ground water have been found to exceed the WHO maximum concentration limit of 10 μg/l. This is adversely affecting the health of millions of people and has grave current and future health implications. It has recently been suggested that extensive abstraction of ground water in these areas may accelerate the release of As to ground water. This study uses geochemical and isotopic data to assess this hypothesis. The area investigated in this study is in the Chakdaha block of the Nadia District, West Bengal. The ground water is predominantly of the Ca-Mg-HCO 3 type, although some s les were found to contain elevated concentrations of Na, Cl and SO 4 . This is thought to reflect a greater degree of water-rock interaction at the locations of these particular s les. Arsenic concentrations exceeded the national limit of 50 μg/l in 13 of the 22 s les collected. Four of the 13 s les with high As were recovered from tubewells with depths of 60 m or more. Shallow ground water s les were found to have a stable isotopic composition which falls subparallel to the Global Meteoric Water Line. This probably represents a contribution of evaporated surface water to the ground water, possibly from surface ponds or re-infiltrating irrigation water. Deep ground water, conversely, was shown to have a composition that closely reflects that of meteoric water. The data presented in this study suggest that, whilst the drawdown of surface waters may drive As release in shallow ground waters, it is not responsible for driving As release in deep ground water. However, local abstraction may have resulted in changes in the ground water flow regime of the area, with contaminated shallow ground waters being drawn into previously uncontaminated deep aquifers.
Publisher: Springer Science and Business Media LLC
Date: 19-11-2004
DOI: 10.1007/S00216-004-2861-1
Abstract: Despite the importance of accurately determining inorganic arsenic speciation in natural waters to predicting bioavailability and environmental and health impacts, there remains considerable debate about the most appropriate species preservation strategies to adopt. In particular, the high-iron, low-Eh (redox potential) shallow groundwaters in West Bengal, Bangladesh and SE Asia, the use of which for drinking and irrigation purposes has led to massive international concerns for human health, are particularly prone to changes in arsenic speciation after s ling. The effectiveness of HCl and EDTA preservation strategies has been compared and used on variably arsenic-rich West Bengali groundwater s les, analysed by ion chromatography-inductively coupled plasma-mass spectrometry (IC-ICP-MS). Immediate filtration and acidification with HCl followed by refrigerated storage was found to be the most effective strategy for minimizing the oxidation of inorganic As(III) during storage. The use of a PRP-X100 (Hamilton) column with a 20 mmol L(-1) NH4H2PO4 as mobile phase enabled the separation of Cl- from As(III), monomethylarsonic acid, dimethylarsinic acid and As(V), thereby eliminating any isobaric interference between 40Ar35Cl+ and 75As+. The use of EDTA as a preservative, whose action is impaired by the high calcium concentrations typical of these types of groundwater, resulted in marked oxidation during storage. The use of HCl is therefore indicated for analytical methods in which chloride-rich matrices are not problematical. The groundwaters analysed by IC-ICP-MS were found to contain between 5 and 770 ng As mL(-1) exclusively as inorganic arsenic species. As(III)/total-As varied between 0 and 0.94.
Publisher: Springer Science and Business Media LLC
Date: 09-07-2021
DOI: 10.1007/S10653-020-00653-9
Abstract: DNA strand breaks are a common form of DNA damage that can contribute to chromosomal instability or gene mutations. Such strand breaks may be caused by exposure to heavy metals. The aim of this study was to assess the level of DNA strand breaks caused by µm-scale solid particles of known chemical composition with elevated heavy metals/metalloids, notably arsenic, using an in vitro cell-free DNA plasmid scission assay. These s les were incubated with and without H 2 O 2 to see whether damage occurs directly or indirectly through the Fenton reaction. Levels of DNA damage in the absence of H 2 O 2 were 10%, but in the presence of H 2 O 2 , all s les showed higher levels of damage ranging from 10 to 100% suggesting that damage was being incurred through the Fenton reaction. Using bivariate correlation analysis and multiple linear regression, manganese oxide (MnO), sulphur (S), copper (Cu), and zinc (Zn) concentrations in the particulates were found to be the most significant predictors of DNA damage. The mechanism of this DNA damage formation has yet to be thoroughly investigated but is hypothesised to be due to reactive oxygen species formation. Further work is required to assess the extent of contribution of reactive oxygen species to this DNA damage, but this study highlights the potential role of chemistry and/or mineralogy to the extent and/or nature of DNA damage caused by particulates.
Publisher: Springer Science and Business Media LLC
Date: 11-07-2021
DOI: 10.1007/S10653-020-00655-7
Abstract: Geogenic arsenic contamination in groundwaters poses a severe health risk to hundreds of millions of people globally. Notwithstanding the particular risks to exposed populations in the Indian sub-continent, at the time of writing, there was a paucity of geostatistically based models of the spatial distribution of groundwater hazard in India. In this study, we used logistic regression models of secondary groundwater arsenic data with research-informed secondary soil, climate and topographic variables as principal predictors generate hazard and risk maps of groundwater arsenic at a resolution of 1 km across Gujarat State. By combining models based on different arsenic concentrations, we have generated a pseudo-contour map of groundwater arsenic concentrations, which indicates greater arsenic hazard ( 10 μg/L) in the northwest, northeast and south-east parts of Kachchh District as well as northwest and southwest Banas Kantha District. The total number of people living in areas in Gujarat with groundwater arsenic concentration exceeding 10 μg/L is estimated to be around 122,000, of which we estimate approximately 49,000 people consume groundwater exceeding 10 µg/L. Using simple previously published dose–response relationships, this is estimated to have given rise to 700 (prevalence) cases of skin cancer and around 10 cases of premature avoidable mortality/annum from internal (lung, liver, bladder) cancers—that latter value is on the order of just 0.001% of internal cancers in Gujarat, reflecting the relative low groundwater arsenic hazard in Gujarat State.
Publisher: MDPI AG
Date: 29-04-2014
DOI: 10.3390/W6051100
Publisher: Elsevier BV
Date: 11-2008
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C7EM00463J
Abstract: Dust elemental levels can be expressed as concentrations (bulk s les) or surface loadings (wipe s les).
Publisher: Springer Science and Business Media LLC
Date: 17-04-2015
DOI: 10.1007/S10653-015-9696-X
Abstract: This study comprises a market-based survey to assess the arsenic (As) hazard of Cambodian rice, encompassing rice from seven Cambodian provinces, comparisons with rice imported from China, Vietnam and Thailand, and assessments of 15 rice varieties. Rice s les (n = 157) were collected from four large markets in Kandal Province and analysed for As using inductively coupled mass spectrometry. The mean As concentration for Cambodian rice (0.185 µg g(-1), range 0.047-0.771 µg g(-1)) was higher than that for imported rice from Vietnam and Thailand (0.162 and 0.157 µg g(-1), respectively) with mean As concentrations highest in rice from Prey Veng Province resulting in a daily dose of 1.77 µg kg(-1) b.w. (body weight) d(-1). Between unmilled rice varieties, Cambodian-grown White Sticky Rice had the highest mean As concentration (0.234 µg g(-1)), whilst White Sticky Rice produced in Thailand had the lowest (0.125 µg g(-1)), suggesting that localised conditions have greater bearing over rice As concentrations than differences in As uptake between in idual varieties themselves. A rice and water consumption survey for 15 respondents in the village of Preak Russey revealed mean consumption rates of 522 g d(-1) of rice and 1.9 L d(-1) of water. At water As concentrations >1000 µg L(-1), the relative contribution to the daily dose from rice is low. When water As concentrations are lowered to 50 µg L(-1), daily doses from rice and water are both generally below the 3.0 µg kg(-1) b.w. d(-1) benchmark daily limit for a 0.5% increase in lung cancer, yet when combined they exceeded this value in all but three respondents.
Publisher: Elsevier BV
Date: 12-2014
Publisher: American Society for Microbiology
Date: 15-07-2013
DOI: 10.1128/AEM.00683-13
Abstract: Microcosms containing sediment from an aquifer in Cambodia with naturally elevated levels of arsenic in the associated groundwater were used to evaluate the effectiveness of microbially mediated production of iron minerals for in situ As remediation. The microcosms were first incubated without amendments for 28 days, and the release of As and other geogenic chemicals from the sediments into the aqueous phase was monitored. Nitrate or a mixture of sulfate and lactate was then added to stimulate biological Fe(II) oxidation or sulfate reduction, respectively. Without treatment, soluble As concentrations reached 3.9 � 0.9 μM at the end of the 143-day experiment. However, in the nitrate- and sulfate-plus-lactate-amended microcosms, soluble As levels decreased to 0.01 and 0.41 � 0.13 μM, respectively, by the end of the experiment. Analyses using a range of biogeochemical and mineralogical tools indicated that sorption onto freshly formed hydrous ferric oxide (HFO) and iron sulfide mineral phases are the likely mechanisms for As removal in the respective treatments. Incorporation of the experimental results into a one-dimensional transport-reaction model suggests that, under conditions representative of the Cambodian aquifer, the in situ precipitation of HFO would be effective in bringing groundwater into compliance with the World Health Organization (WHO) provisional guideline value for As (10 ppb or 0.13 μM), although soluble Mn release accompanying microbial Fe(II) oxidation presents a potential health concern. In contrast, production of biogenic iron sulfide minerals would not remediate the groundwater As concentration below the recommended WHO limit.
Publisher: MDPI AG
Date: 11-10-2023
DOI: 10.3390/W15203539
Publisher: Springer Science and Business Media LLC
Date: 09-05-2015
Publisher: MDPI AG
Date: 18-02-2021
DOI: 10.3390/W13040527
Abstract: Groundwater arsenic in Uruguay is an important environmental hazard, hence, predicting its distribution is important to inform stakeholders. Furthermore, occurrences in Uruguay are known to variably show dependence on depth and geology, arguably reflecting different processes controlling groundwater arsenic concentrations. Here, we present the distribution of groundwater arsenic in Uruguay modelled by a variety of machine learning, basic expert systems, and hybrid approaches. A pure random forest approach, using 26 potential predictor variables, gave rise to a groundwater arsenic distribution model with a very high degree of accuracy (AUC = 0.92), which is consistent with known high groundwater arsenic hazard areas. These areas are mainly in southwest Uruguay, including the Paysandú, Río Negro, Soriano, Colonia, Flores, San José, Florida, Montevideo, and Canelones departments, where the Mercedes, Cuaternario Oeste, Raigón, and Cretácico main aquifers occur. A hybrid approach separating the country into sedimentary and crystalline aquifer domains resulted in slight material improvement in a high arsenic hazard distribution. However, a further hybrid approach separately modelling shallow ( m) and deep aquifers ( m) resulted in the identification of more high hazard areas in Flores, Durazno, and the northwest corner of Florida departments in shallow aquifers than the pure model. Both hybrid models considering depth (AUC = 0.95) and geology (AUC = 0.97) produced improved accuracy. Hybrid machine learning models with expert selection of important environmental parameters may sometimes be a better choice than pure machine learning models, particularly where there are incomplete datasets, but perhaps, counterintuitively, this is not always the case.
Publisher: American Association of Petroleum Geologists AAPG/Datapages
Date: 03-2014
DOI: 10.1306/08201311176
Publisher: MDPI AG
Date: 19-06-2015
DOI: 10.3390/W7063057
Publisher: Elsevier BV
Date: 02-2007
DOI: 10.1016/J.SAA.2006.02.053
Abstract: The FTIR spectra of pure magnesium-rich (Mg-rich) and magnesium-poor (Mg-poor) palygorskites, before and after short-term (<7 h) and long-term (360 h) acid leaching are presented here. Comparison of decomposition spectra of Mg-rich and Mg-poor palygorskites clearly shows that the absorption peaks related to pairs of octahedral cation differ depending on the octahedral site occupancy. Short-term acid leaching of palygorskites results in significant changes to FTIR absorption bands near 1200 and 790 cm-1. As the acid attack progresses, the band at 1200 cm-1 shifts to lower wavenumbers, whilst the band at 790 cm-1, which here is assigned to SiU-O-SiD symmetrical stretching vibration, shifts to higher wavelengths. Longer-term leaching of palygorskites results in the disappearance of 900-1200 cm-1 absorption bands, showing that the palygorskite has largely decomposed to amorphous silica. Assignments of several other bands have been made as follows: several vibrations relate to OH, i.e. 847 cm-1, hygroscopic water (1635 cm-1), Si-O vibrations 1100, 611-621, 470-481 cm-1, etc. appear in the FTIR spectra of 360 h acid leached palygorskite. Three bands near 1100, 611-621 and 470-481 cm-1 relate to Si-O vibration of an ideal hexagonal (Si2O5)n sheet.
Publisher: Elsevier BV
Date: 06-2005
DOI: 10.1016/J.SCITOTENV.2004.10.030
Abstract: There is a dearth of research concerning the geochemistry of arsenic in acid mine drainage (AMD) in western Tasmania. To help address this, the controls on the mobility and fate of arsenic in AMD and its associated sediment at the Mount Bischoff mine site in western Tasmania were investigated. AMD issuing from the adit mouth contained dissolved arsenic and iron concentrations of 2.5 and 800 mg L(-1), respectively. The aqueous concentration of both arsenic and iron decreased markedly over a 150-m stretch from the adit mouth due to precipitation of hydrous ferric oxides (HFO) and jarosite, both of which are effective scavengers of arsenic. Microwave-assisted digestion of the sediment collected at the adit mouth revealed that the arsenic concentration exceeded 1%. Sequential extraction of this sediment showed that the bulk of arsenic was associated with amorphous and crystalline hydrous oxides of Al and/or Fe. Extended X-ray absorption fine structure (EXAFS) analysis indicated that the solid phase arsenic exists as As(V). EXAFS data were consistent with arsenate tetrahedra substituting for sulphate in jarosite and with corner-sharing complexes adsorbed on ferric oxyhydroxide octahedra. Erosional transport of AMD sediment downstream to higher pH waters may increase the mobility (and hence bioavailablity) of arsenic through dissolution of As-rich jarosite.
Publisher: Wiley
Date: 08-02-2010
DOI: 10.1111/J.1472-4669.2010.00233.X
Abstract: High arsenic concentrations in groundwater are causing a humanitarian disaster in Southeast Asia. It is generally accepted that microbial activities play a critical role in the mobilization of arsenic from the sediments, with metal-reducing bacteria stimulated by organic carbon implicated. However, the detailed mechanisms underpinning these processes remain poorly understood. Of particular importance is the nature of the organic carbon driving the reduction of sorbed As(V) to the more mobile As(III), and the interplay between iron and sulphide minerals that can potentially immobilize both oxidation states of arsenic. Using a multidisciplinary approach, we identified the critical factors leading to arsenic release from West Bengal sediments. The results show that a cascade of redox processes was supported in the absence of high loadings of labile organic matter. Arsenic release was associated with As(V) and Fe(III) reduction, while the removal of arsenic was concomitant with sulphate reduction. The microbial populations potentially catalysing arsenic and sulphate reduction were identified by targeting the genes arrA and dsrB, and the total bacterial and archaeal communities by 16S rRNA gene analysis. Results suggest that very low concentrations of organic matter are able to support microbial arsenic mobilization via metal reduction, and subsequent arsenic mitigation through sulphate reduction. It may therefore be possible to enhance sulphate reduction through subtle manipulations to the carbon loading in such aquifers, to minimize the concentrations of arsenic in groundwaters.
Publisher: Elsevier BV
Date: 06-2011
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C8EM00437D
Abstract: First use of drinking water compliance s les for hydrochemistry. Distinct groundwater–surface water split. S les show water provenance.
Publisher: Elsevier BV
Date: 09-2003
Publisher: American Chemical Society (ACS)
Date: 20-06-2013
DOI: 10.1021/ES400114Q
Abstract: Microbially mediated reductive processes involving the oxidation of labile organic carbon are widely considered to be critical to the release of arsenic into shallow groundwaters in South and Southeast Asia. In areas where there is significant pumping of groundwater for irrigation the involvement of surface-derived organic carbon drawn down from ponds into the underlying aquifers has been proposed but remains highly controversial. Here we present isotopic data from two sites with contrasting groundwater pumping histories that unequivocally demonstrate the ingress of surface pond-derived organic carbon into arsenic-containing groundwaters. We show that pond-derived organic carbon is transported to depths of up to 50 m even in an arsenic-contaminated aquifer in Cambodia thought to be minimally disturbed by groundwater pumping. In contrast, in the extensively exploited groundwaters of West Bengal, we show that pond-derived organic carbon is transported in shallow groundwater to greater depths, in excess of 100 m in the aquifer. Intensive pumping of groundwaters may potentially drive secular increases in the groundwater arsenic hazard in this region by increasing the contribution of bioavailable pond-derived dissolved organic carbon drawn into these aquifer systems and transporting it to greater depths than would operate under natural flow conditions.
Publisher: Informa UK Limited
Date: 16-10-2007
DOI: 10.1080/10934520701567205
Abstract: It has been increasingly recognised that calculation of the disease burden due to populations, such as in Bangladesh, extensively using hazardous arsenic bearing well waters, must explicitly account for the trade-off between diarrhoeal disease incidence and that of arsenic-related diseases. This is because it is likely that moves to alternative drinking water sources, be they surface waters or even more distant groundwaters, without further mitigation would result in a concurrent increase in diarrhoeal disease. In this paper, we update the model of Lokuge of the effects of such arsenic mitigation on disease burden in Bangladesh, using updated population data and background disease estimates. We run a critical pathway analysis on the model using Standardised Mortality Ratios (SMRs) for diabetes mellitus and ischemic heart disease from different epidemiological studies recently reviewed by Navas-Acien. Our analysis agrees with that of Lokuge that mitigation simply involving the substitution of a range of surface waters for well water sources with As > 50 microg/L would have a net positive impact on disease burden, as determined by deaths and Disability Life Adjusted Years (DALYs). In contrast, however, there is considerable ambiguity in the analogous results for mitigation for all the population exposed to well water with As > 10 microg/L. Depending upon the data source chosen for diabetes mellitus and ischaemic heart disease SMRs, such mitigation is modelled to have either a positive or a negative net impact on overall disease burden. The modelled negative impacts are entirely commensurate with the rationale for seeking groundwater as an alternative to surface waters as a drinking water supply, and highlight the practical requirement for multiple mitigation strategies, including those directed at ensuring the microbiological safety and continued protection of any alternative water supplies. Our study highlights the need for (i) adequate epidemiological studies involving multiple exposure categories, ideally resulting in an accurate dose-response relationship for arsenic uptake and the non-malignant high incidence conditions diabetes mellitus and ischemic heart disease for in iduals with the socioeconomic and nutritional status of the Bangladeshi populations, and (ii) refined estimates of the diarrhoel disease burden arising from usage of surface waters.
Publisher: Springer Science and Business Media LLC
Date: 2003
Abstract: Seasonal differences in the dissolved arsenic concentration and speciation in a contaminated urban waterway in northwest England have been determined using a coupled ion chromatography-inductively coupled plasma-mass spectrometry (IC-ICP-MS) technique. Waters s led in the vicinity of an industrial works during relatively dry conditions in April 2000 were found to contain total arsenic concentrations (sigma As) of up to 132 micrograms L-1, more than an order magnitude greater than the 4 micrograms L-1 maximum found in December 2000. The difference in sigma As between the April and December s ling periods is speculated to be largely due to the irregular anthropogenic supply of arsenic to the watercourse. For both s ling periods, the dissolved arsenic was exclusively inorganic in nature and had an As(V)/sigma As ratio of between 0.6 and 0.8. Analysis of s les taken downstream of the industrial site, after the confluence with a relatively As-poor stream, revealed that As(III), As(V) and sigma As concentrations were lower than would be expected from conservative mixing. The As(V)/sigma As ratio was also observed to decrease markedly. The loss of arsenic from solution is thought to be due to adsorption on the iron oxyhydroxide-rich sediment observed to coat the riverbed downstream of the confluence. The reduction in the As(V)/sigma As ratio is believed to be due to the more rapid adsorption of As(V) compared to that of As(III). Deviations from conservative behaviour were more marked during the relatively dry April 2000 s ling period and suggest the increased importance of adsorption processes controlling arsenic availability during this time.
Publisher: MDPI AG
Date: 28-09-2020
Abstract: Groundwater is a critical resource in India for the supply of drinking water and for irrigation. Its usage is limited not only by its quantity but also by its quality. Among the most important contaminants of groundwater in India is arsenic, which naturally accumulates in some aquifers. In this study we create a random forest model with over 145,000 arsenic concentration measurements and over two dozen predictor variables of surface environmental parameters to produce hazard and exposure maps of the areas and populations potentially exposed to high arsenic concentrations ( µg/L) in groundwater. Statistical relationships found between the predictor variables and arsenic measurements are broadly consistent with major geochemical processes known to mobilize arsenic in aquifers. In addition to known high arsenic areas, such as along the Ganges and Brahmaputra rivers, we have identified several other areas around the country that have hitherto not been identified as potential arsenic hotspots. Based on recent reported rates of household groundwater use for rural and urban areas, we estimate that between about 18–30 million people in India are currently at risk of high exposure to arsenic through their drinking water supply. The hazard models here can be used to inform prioritization of groundwater quality testing and environmental public health tracking programs.
Publisher: MDPI AG
Date: 17-08-2021
DOI: 10.3390/W13162232
Abstract: Cardiovascular diseases (CVDs) have been recognized as the most serious non-carcinogenic detrimental health outcome arising from chronic exposure to arsenic. Drinking arsenic contaminated groundwaters is a critical and common exposure pathway for arsenic, notably in India and other countries in the circum-Himalayan region. Notwithstanding this, there has hitherto been a dearth of data on the likely impacts of this exposure on CVD in India. In this study, CVD mortality risks arising from drinking groundwater with high arsenic ( μg/L) in India and its constituent states, territories, and districts were quantified using the population-attributable fraction (PAF) approach. Using a novel pseudo-contouring approach, we estimate that between 58 and 64 million people are exposed to arsenic exceeding 10 μg/L in groundwater-derived drinking water in India. On an all-India basis, we estimate that 0.3–0.6% of CVD mortality is attributable to exposure to high arsenic groundwaters, corresponding to annual avoidable premature CVD-related deaths attributable to chronic exposure to groundwater arsenic in India of between around 6500 and 13,000. Based on the reported reduction in life of 12 to 28 years per death due to heart disease, we calculate value of statistical life (VSL) based annual costs to India of arsenic-attributable CVD mortality of between USD 750 million and USD 3400 million.
Publisher: BMJ
Date: 26-03-2022
DOI: 10.1136/EMERMED-2020-210256
Abstract: To compare the efficacy of continuous positive airway pressure (CPAP) versus usual care for prehospital patients with severe respiratory distress. We conducted a parallel group, in idual patient, non-blinded randomised controlled trial in Western Australia between March 2016 and December 2018. Eligible patients were aged ≥40 years with acute severe respiratory distress of non-traumatic origin and unresponsive to initial treatments by emergency medical service (EMS) paramedics. Patients were randomised (1:1) to usual care or usual care plus CPAP. The primary outcomes were change in dyspnoea score and change in RR at ED arrival, and hospital length of stay. 708 patients were randomly assigned (opaque sealed envelope) to usual care (n=346) or CPAP (n=362). Compared with usual care, patients randomised to CPAP had a greater reduction in dyspnoea scores (usual care −1.0, IQR −3.0 to 0.0 vs CPAP −3.5, IQR −5.2 to −2.0), median difference −2.0 (95% CI −2.5 to −1.6) and RR (usual care −4.0, IQR −9.0 to 0.0 min -1 vs CPAP −8.0, IQR −14.0 to −4.0 min -1 ), median difference −4.0 (95% CI −5.0 to −4.0) min -1 . There was no difference in hospital length of stay (usual care 4.2, IQR 2.1 to 7.8 days vs CPAP 4.8, IQR 2.5 to 7.9 days) for the n=624 cases admitted to hospital, median difference 0.36 (95% CI −0.17 to 0.90). The use of prehospital CPAP by EMS paramedics reduced dyspnoea and tachypnoea in patients with acute respiratory distress but did not impact hospital length of stay. ACTRN12615001180505.
Publisher: Springer Science and Business Media LLC
Date: 22-07-2013
DOI: 10.1038/SREP02195
Abstract: Arsenic in drinking water may cause major deleterious health impacts including death. Although arsenic in rice has recently been demonstrated to be a potential exposure route for humans, there has been to date no direct evidence for the impact of such exposure on human health. Here we show for the first time, through a cohort study in West Bengal, India, involving over 400 human subjects not otherwise significantly exposed to arsenic through drinking water, elevated genotoxic effects, as measured by micronuclei (MN) in urothelial cells, associated with the staple consumption of cooked rice with μg/kg arsenic. Further work is required to determine the applicability to populations with different dietary and genetic characteristics, but with over 3 billion people in the world consuming rice as a staple food and several percent of this rice containing such elevated arsenic concentrations, this study raises considerable concerns over the threat to human health.
Publisher: American Society for Microbiology
Date: 12-2005
DOI: 10.1128/AEM.71.12.8642-8648.2005
Abstract: Previous work has shown that microbial communities in As-mobilizing sediments from West Bengal were dominated by Geobacter species. Thus, the potential of Geobacter sulfurreducens to mobilize arsenic via direct enzymatic reduction and indirect mechanisms linked to Fe(III) reduction was analyzed. G. sulfurreducens was unable to conserve energy for growth via the dissimilatory reduction of As(V), although it was able to grow in medium containing fumarate as the terminal electron acceptor in the presence of 500 μM As(V). There was also no evidence of As(III) in culture supernatants, suggesting that resistance to 500 μM As(V) was not mediated by a classical arsenic resistance operon, which would rely on the intracellular reduction of As(V) and the efflux of As(III). When the cells were grown using soluble Fe(III) as an electron acceptor in the presence of As(V), the Fe(II)-bearing mineral vivianite was formed. This was accompanied by the removal of As, predominantly as As(V), from solution. Biogenic siderite (ferrous carbonate) was also able to remove As from solution. When the organism was grown using insoluble ferrihydrite as an electron acceptor, Fe(III) reduction resulted in the formation of magnetite, again accompanied by the nearly quantitative sorption of As(V). These results demonstrate that G. sulfurreducens , a model Fe(III)-reducing bacterium, did not reduce As(V) enzymatically, despite the apparent genetic potential to mediate this transformation. However, the reduction of Fe(III) led to the formation of Fe(II)-bearing phases that are able to capture arsenic species and could act as sinks for arsenic in sediments.
Publisher: MDPI AG
Date: 07-04-2020
Abstract: To the best of our knowledge, a dose-response meta-analysis of the relationship between cardiovascular disease (CVD) and arsenic (As) exposure at drinking water As concentrations lower than the WHO provisional guideline value (10 µg/L) has not been published yet. We conducted a systematic review and meta-analyses to estimate the pooled association between the relative risk of each CVD endpoint and low-level As concentration in drinking water both linearly and non-linearly using a random effects dose-response model. In this study, a significant positive association was found between the risks of most CVD outcomes and drinking water As concentration for both linear and non-linear models (p-value for trend 0.05). Using the preferred linear model, we found significant increased risks of coronary heart disease (CHD) mortality and CVD mortality as well as combined fatal and non-fatal CHD, CVD, carotid atherosclerosis disease and hypertension in those exposed to drinking water with an As concentration of 10 µg/L compared to the referent (drinking water As concentration of 1 µg/L) population. Notwithstanding limitations included, the observed significant increased risks of CVD endpoints arising from As concentrations in drinking water between 1 µg/L and the 10 µg/L suggests further lowering of this guideline value should be considered.
Publisher: Mineralogical Society
Date: 02-2008
DOI: 10.1180/MINMAG.2008.072.1.437
Abstract: We combined statistical analyses and GIS capabilities within the statistical environment R to create a semi-automated method for the assessment of As hazard risk in shallow groundwater in Cambodia. Arsenic concentration data for groundwaters of between 16 and 100 m depth were obtained from 1437 geo-referenced wells. We created a binary logistic regression model with these As measurements as the dependent variable and a number of raster maps (DEM-parameters, remote sensing images and geomorphology) as explanatory variables, and considering an As threshold of 10 ppb. This allowed us to make an As hazard map for groundwaters between 16—100 m depth: this can be used to help to identify populations vulnerable to exposure. The logistic regression analysis indicates a good correlation between topographic and geomorphologic environmental variables and the As hazard risk in groundwater. Ease of implementation, and the ability to update, along with objectivity and reproducibility are the main advantages related to this method of analysis.
Publisher: Elsevier BV
Date: 09-2006
Publisher: Elsevier BV
Date: 10-2006
DOI: 10.1016/J.TAAP.2006.04.004
Abstract: Very little is known about arsenic (As) metabolism in healthy populations that are not exposed to high concentrations of As in their food or water. Here we present a study with healthy volunteers from three different ethnic groups, residing in Leicester, UK, which reveals statistically significant differences in the levels of total As in urine and fingernail s les. Urine (n = 63), hair (n = 36) and fingernail (n = 36) s les from Asians, Somali Black-Africans and Whites were analysed using inductively coupled plasma mass spectrometry (ICP-MS) and graphite furnace atomic absorption spectroscopy (GF-AAS). The results clearly show that the total concentrations of As in urine and fingernail s les of a Somali Black-African population (urine 7.2 microg/g creatinine fingernails 723.1 microg/kg) are significantly (P 0.05) in the level of As in the hair s les from these three groups Somali Black-Africans (116.0 microg/kg), Asians (117.4 microg/kg) and Whites (141.2 microg/kg). Significantly different levels of total As in fingernail and urine and a higher percentage of urinary DMA in the Somali Black-Africans are suggestive of a different pattern of As metabolism in this ethnic group.
Publisher: Elsevier BV
Date: 11-2008
Publisher: Elsevier BV
Date: 11-2020
Publisher: Wiley
Date: 07-2009
DOI: 10.2134/JEQ2008.0223
Abstract: High levels of naturally occurring arsenic are found in the shallow reducing aquifers of West Bengal, Bangladesh, and other areas of Southeast Asia. These aquifers are used extensively for drinking water and irrigation by the local population. Mechanisms for its release are unclear, although increasing evidence points to a microbial control. The type of organic matter present is of vital importance because it has a direct impact on the rate of microbial activity and on the amount of arsenic released into the ground water. The discovery of naturally occurring hydrocarbons in an arsenic-rich aquifer from West Bengal provides a source of potential electron donors for this process. Using microcosm-based techniques, seven sediments from a site containing naturally occurring hydrocarbons in West Bengal were incubated with synthetic ground water for 28 d under anaerobic conditions without the addition of an external electron donor. Arsenic release and Fe(III) reduction appeared to be microbially mediated, with variable rates of arsenic mobilization in comparison to Fe(III) reduction, suggesting that multiple processes are involved. All sediments showed a preferential loss of petroleum-sourced n-alkanes over terrestrially sourced sedimentary hydrocarbons n-alkanes during the incubation, implying that the use of petroleum-sourced n-alkanes could support, directly or indirectly, microbial Fe(III) reduction. S les undergoing maximal release of As(III) contained a significant population of Sulfurospirillum sp., a known As(V)-reducing bacterium, providing the first evidence that such organisms may mediate arsenic release from West Bengali aquifers.
Publisher: Elsevier BV
Date: 02-2013
Publisher: Mineralogical Society
Date: 10-2005
Abstract: Arsenic-rich scales are widely associated with geothermal fields and constitute a potential hazard to human health. Such arsenic has hitherto been reported to be almost exclusively hosted by sulphide or oxide phases or occurring as surface species. We report here, however, the occurrence of an arsenic-rich (1500 to 4000 mg kg —1 As) smectite from geothermal precipitates from a geothermal field in northwestern Japan and present evidence that the arsenic is predominantly hosted within this silicate mineral. Consistently ∼80% of the total arsenic determined in these geothermal precipitates was found by selective chemical extractions to be associated with an operationally defined clay mineral fraction, with lesser proportions being associated with operationally defined amorphous silica, Fe oxide and sulphide fractions. Analysis by XRD, ATR IR and XRF showed the clay fraction to be dominated by Mg-rich trioctahedral smectite. Arsenic K-edge XAS spectra of the smectite suggested the dominance of As(III)-O coordinated species with significant contributions from As(V)-O coordinated species. Both XPS and a magnesium chloride chemical extraction indicated minimal adsorption of arsenic on smectite surfaces suggesting that the arsenic was predominantly either dissolved within the smectite or occurred within mineral occlusions. No such occlusions greater than 1 μm in size were observed in the As-rich smectites. The potential occurrence of arsenic-bearing clays should be considered when determining remediation strategies for geothermal environments or evaluating risks associated with the industrial usage of geothermal precipitates.
Publisher: Elsevier BV
Date: 11-2008
Publisher: Elsevier BV
Date: 08-2004
Publisher: Elsevier BV
Date: 07-2008
DOI: 10.1016/J.SCITOTENV.2008.02.023
Abstract: An impacted soil located near an industrial waste site in the Massif Central near Auzon, France, where arsenical pesticides were manufactured, has been studied in order to determine the speciation (chemical forms) of arsenic as a function of soil depth. Bulk As concentrations range from 8780 mg kg(-1) in the topsoil horizon to 150 mg kg(-1) at 60 cm depth. As ores (orpiment As2S3, realgar AsS, arsenopyrite FeAsS) and former Pb- and Al-arsenate pesticides have been identified by XRD at the site and are suspected to be the sources of As contamination for this soil. As speciation was found to vary with depth, based on XRD, SEM-EDS, EPMA measurements and selective chemical extractions. Based on oxalate extraction, As is mainly associated with amorphous Fe oxides through the soil profile, except in the topsoil horizons where As is hosted by another phase. SEM-EDS and EPMA analyses led to the identification of arseniosiderite (Ca2Fe3+3(AsVO4)3O2.3H2O), a secondary mineral that forms upon oxidation of primary As-bearing minerals like arsenopyrite, in these topsoil horizons. These mineralogical and chemical results were confirmed by synchrotron-based X-ray absorption spectroscopy. XANES spectra of soil s les indicate that As occurs exclusively as As(V), and EXAFS results yield direct evidence of changes in As speciation with depth. Linear combination fits of EXAFS spectra of soil s les with those of various model compounds indicate that As occurs mainly As-bearing Fe(III)-(hydr)oxides (65%) and arseniosiderite (35%) in the topsoil horizon (0-5 cm depth). Similar analyses also revealed that there is very little arseniosiderite below 15 cm depth and that As(V) is associated primarily with amorphous Fe oxides below this depth. This vertical change of As speciation likely reflects a series of chemical reactions downward in the soil profile. Arseniosiderite, formed most likely by oxidation of arsenopyrite, is progressively dissolved and replaced by less soluble As-bearing poorly ordered Fe oxides, which are the main hosts for As in well aerated soils.
Publisher: Elsevier BV
Date: 11-2008
Publisher: Mineralogical Society
Date: 02-2008
DOI: 10.1180/MINMAG.2008.072.1.461
Abstract: Soluble inorganic As is toxic with both cancer and non-cancer endpoints. Of the 80 million people in West Bengal, 50 million are living in the nine As-affected districts with millions at risk from using water for drinking, cooking or irrigation (Chakraborti et al ., 2004). An environmental tragedy is developing in West Bengal with an alarming number of cases of skin lesions (Guha Mazumder et al ., 1998 Mukherjee et al ., 2005), respiratory symptoms (von Ehrenstein et al ., 2005), adverse pregnancy outcomes and infant mortality (von Ehrenstein et al ., 2006) and neurological complications (Mukherjee et al ., 2005) associated with ingestion of As-contaminated water.
Publisher: Mineralogical Society of America
Date: 04-2006
Publisher: Elsevier BV
Date: 04-2004
Publisher: Springer Science and Business Media LLC
Date: 06-2009
DOI: 10.1038/NGEO537
Publisher: Mineralogical Society
Date: 10-2005
Abstract: Arsenic mobilization and Fe(III) reduction in acetate-amended sediments collected from a range of depths from an aquifer with elevated groundwater arsenic concentrations in West Bengal were monitored over a 1 month period. Significant arsenic release was noted in sediment collected from 24 m and 45 m depth, with some Fe(III) reduction also observed in the 24 m s le. The structure of the microbial communities present in the sediments prior to incubation showed marked differences down the sediment column. Profiling of the microbial community in the 24 m and 45 m s les revealed a relatively complex make-up, with Acinetobacter species comprising the bulk of the 24 m sedimentary bacterial population, but no previously characterized As(V)-reducers were detected in either s le.
Publisher: Elsevier BV
Date: 08-2014
Publisher: Mineralogical Society
Date: 10-2005
Abstract: Previous studies from our laboratory have suggested a role for indigenous metal-reducing bacteria in the reduction of sediment-bound As(V), and have also shown that a stable enrichment culture of Fe(III)-reducing bacteria was able to mobilize arsenic (as As(III)) from sediments collected from West Bengal (Islam et al ., 2004). To identify the Fe(III)-reducing bacteria that may play a role in the reduction of As(V) and mobilization of As(III), we made a detailed molecular analysis of this enrichment culture. It was dominated by a close relative of Geothrix fermentans , but the type strain of this organism was unable to conserve energy for growth via the dissimilatory reduction of As(V), or reduce As(V) present in a defined medium containing fumarate as the electron acceptor. Furthermore, when the cells were grown using soluble Fe(III)-citrate as an electron acceptor in the presence of As(V), bacterial Fe(III) reduction resulted in the precipitation of the Fe(II)-bearing mineral vivianite in 2 weeks. This was accompanied by the efficient removal of As from solution. These results demonstrate that Geothrix fermentans , in common with other key Fe(III)-reducing bacteria such as Geobacter sulfurreducens , does not reduce As(V) enzymatically, but can capture arsenic in Fe(II) minerals formed during respiration using Fe(III) as an electron acceptor. Thus, the reduction of arsenic-bearing Fe(III) oxide minerals is not sufficient to mobilize arsenic, but may result in the formation of Fe(II) biominerals that could potentially act as sinks for arsenic in sediments. Additional mechanisms, including dissimilatory As(V) reduction by other specialist anaerobic bacteria, are implicated in the mobilization of arsenic from sediments.
Publisher: Mineralogical Society
Date: 10-2005
Abstract: Determination of the solid-phase arsenic speciation in sediments hosting high-arsenic groundwaters, utilized for drinking and irrigation in Bengal, SE Asia and elsewhere is important in order to understand the biogeochemistry of arsenic. Despite this, there is a relative paucity of speciation data for solid-phase arsenic in such systems, due to preservation difficulties, low arsenic concentrations in the sediments, multiple coordination environments and s le heterogeneity. In this study, X-ray absorption near edge structure spectroscopy was used in conjunction with linear least-squares fitting of model compounds to determine the oxidation state of arsenic in sediments from West Bengal and Cambodia. Whatever the collection and storage method used, substantial oxidation of arsenic was commonly observed over periods of weeks to several months. Sands were particularly susceptible to changes in arsenic oxidation state during storage. Analysis within two or three weeks of collection is therefore recommended, whilst on-site storage under a nitrogen atmosphere immediately after collection is particularly recommended for the preservation of sandy s les. Both muds and sands from West Bengal and Cambodia were dominated by arsenite (As(III)) with ±10% arsenate (As(V)). Complete oxidation to arsenate was never observed suggesting that a significant proportion of the sedimentary arsenic is inaccessible within crystalline phases. Centrifuging under anaerobic conditions enabled more detailed information about a variety of arsenic coordination environments to be determined.
Publisher: Elsevier BV
Date: 11-2013
DOI: 10.1016/J.JHAZMAT.2012.08.007
Abstract: Arsenic (As) in groundwaters extensively used by people across the world constitutes a serious public health threat. The importance of organic matter (OM) as an electron donor in microbially-mediated reduction of As(V) or Fe(III)-bearing As-host minerals leading to mobilisation of solid-phase arsenic is widely recognised. Notwithstanding this, there are few studies characterising OM in such aquifers and, in particular, there is a dearth of data from the classic arsenic bearing aquifers in southwestern Taiwan. Organic geochemical analyses of sediments from a known groundwater arsenic hot-spot in southwestern Taiwan revealed contributions of thermally mature and plant derived origin, consistent with OM sources in all other Asian groundwater aquifer sediments analysed to date, indicating comparable sources and routes of OM transfer. The combined results of amended As(V) reduction assays with the organic geochemical analysis revealed that the microbiological process of dissimilatory As(V) reduction is active in this aquifer, but it is not controlled by a specific source of analysed OM. These indicate that (i) part of the OM that was considered to be less bio-available could still be used as an electron donor or (ii) other electron donors, not analysed in present study, could be controlling the rate of As release.
Publisher: Elsevier BV
Date: 04-2008
DOI: 10.1016/J.SCITOTENV.2007.12.028
Abstract: The health implications of the consumption of high arsenic groundwater in Bangladesh and West Bengal are well-documented, however, little is known about the level of arsenic exposure elsewhere in Southeast Asia, where widespread exploitation of groundwater resources is less well established. We measured the arsenic concentrations of nail and hair s les collected from residents of Kandal province, Cambodia, an area recently identified to host arsenic-rich groundwaters, in order to evaluate the extent of arsenic exposure. Nail and hair arsenic concentrations ranged from 0.20 to 6.50 microg g(-1) (n=70) and 0.10 to 7.95 microg g(-1) (n=40), respectively, in many cases exceeding typical baseline levels. The arsenic content of the groundwater used for drinking water purposes (0.21-943 microg L(-1) (n=31)) was positively correlated with both nail (r=0.74, p<0.0001) and hair (r=0.86, p<0.0001) arsenic concentrations. In addition, the nail and hair s les collected from inhabitants using groundwater that exceeded the Cambodian drinking water legal limit of 50 microg L(-1) arsenic contained significantly more arsenic than those of in iduals using groundwater containing <50 microg L(-1) arsenic. X-ray absorption near edge structure (XANES) spectroscopy suggested that sulfur-coordinated arsenic was the dominant species in the bulk of the s les analysed, with additional varying degrees of As(III)-O character. Tentative linear least squares fitting of the XANES data pointed towards differences in the pattern of arsenic speciation between the nail and hair s les analysed, however, mismatches in s le and standard absorption peak intensity prevented us from unambiguously determining the arsenic species distribution. The good correlation with the groundwater arsenic concentration, allied with the relative ease of s ling such tissues, indicate that the arsenic content of hair and nail s les may be used as an effective biomarker of arsenic intake in this relatively recently exposed population.
Publisher: Wiley
Date: 05-03-2014
Abstract: Microbially mediated arsenic release from Holocene and Pleistocene Cambodian aquifer sediments was investigated using microcosm experiments and substrate amendments. In the Holocene sediment, the metabolically active bacteria, including arsenate-respiring bacteria, were determined by DNA stable-isotope probing. After incubation with (13) C-acetate and (13) C-lactate, active bacterial community in the Holocene sediment was dominated by different Geobacter spp.-related 16S rRNA sequences. Substrate addition also resulted in the enrichment of sequences related to the arsenate-respiring Sulfurospirillum spp. (13) C-acetate selected for ArrA related to Geobacter spp. whereas (13) C-lactate selected for ArrA which were not closely related to any cultivated organism. Incubation of the Pleistocene sediment with lactate favoured a 16S rRNA-phylotype related to the sulphate-reducing Desulfovibrio oxamicus DSM1925, whereas the ArrA sequences clustered with environmental sequences distinct from those identified in the Holocene sediment. Whereas limited As(III) release was observed in Pleistocene sediment after lactate addition, no arsenic mobilization occurred from Holocene sediments, probably because of the initial reduced state of As, as determined by X-ray Absorption Near Edge Structure. Our findings demonstrate that in the presence of reactive organic carbon, As(III) mobilization can occur in Pleistocene sediments, having implications for future strategies that aim to reduce arsenic contamination in drinking waters by using aquifers containing Pleistocene sediments.
Publisher: American Society for Microbiology
Date: 15-02-2007
DOI: 10.1128/AEM.01654-06
Abstract: The health of millions is threatened by the use of groundwater contaminated with sediment-derived arsenic for drinking water and irrigation purposes in Southeast Asia. The microbial reduction of sorbed As(V) to the potentially more mobile As(III) has been implicated in release of arsenic into groundwater, but to date there have been few studies of the microorganisms that can mediate this transformation in aquifers. With the use of stable isotope probing of nucleic acids, we present evidence that the introduction of a proxy for organic matter ( 13 C-labeled acetate) stimulated As(V) reduction in sediments collected from a Cambodian aquifer that hosts arsenic-rich groundwater. This was accompanied by an increase in the proportion of prokaryotes closely related to the dissimilatory As(V)-reducing bacteria Sulfurospirillum strain NP-4 and Desulfotomaculum auripigmentum . As(V) respiratory reductase genes ( arrA ) closely associated with those found in Sulfurospirillum barnesii and Geobacter uraniumreducens were also detected in active bacterial communities utilizing 13 C-labeled acetate in microcosms. This study suggests a direct link between inputs of organic matter and the increased prevalence and activity of organisms which transform As(V) to the potentially more mobile and thus hazardous As(III) via dissimilatory As(V) reduction.
Publisher: Mineralogical Society
Date: 10-2005
Abstract: Our recent discovery of hazardous concentrations of arsenic in shallow sedimentary aquifers in Cambodia raises the spectre of future deleterious health impacts on a population that, particularly in non-urban areas, extensively use untreated groundwater as a source of drinking water and, in some instances, as irrigation water. We present here small-scale hazard maps for arsenic in shallow Cambodian groundwaters based on groundwater s les analysed in the Manchester Analytical Geochemistry Unit and elsewhere. Key indicators for hazardous concentrations of arsenic in Cambodian groundwaters include: (1) well depths greater than 16 m (2) Holocene host sediments and (3) proximity to major modern channels of the Mekong (and its distributary the Bassac). However, high-arsenic well waters are also commonly found in wells not exhibiting these key characteristics, notably in some shallower Holocene wells, and in wells drilled into older Quaternary and Neogene sediments. It is emphasized that the maps and tables presented are most useful for identifying current regional trends in groundwater arsenic hazard and that their use for predicting arsenic concentrations in in idual wells, for ex le for the purposes of well switching, is not recommended, particularly because of the lack of sufficient data (especially at depths m) and because, as in Bangladesh and West Bengal, there is considerable heterogeneity of groundwater arsenic concentrations on a scale of metres to hundreds of metres. We have insufficient data at this time to determine unequivocally whether or not arsenic concentrations are increasing in shallow Cambodian groundwaters as a result of groundwater-abstraction activities.
Publisher: Informa UK Limited
Date: 16-10-2007
DOI: 10.1080/10934520701564269
Abstract: Many millions of people worldwide are at risk of severe poisoning through exposure to groundwater contaminated with sediment-derived arsenic. An ever-increasing body of work is reinforcing the link between microbially-mediated redox cycling in aquifer sediments and the mobilisation of sorbed As(V) into groundwaters as the potentially more mobile and toxic As(III) anion. However, to date, few studies have examined the biogeochemical cycling of Fe and As species by microbes indigenous to Cambodian sediments. In this study two contrasting sediments, taken from a shallow As-rich reducing aquifer in the Kien Svay district of Cambodia, were used in a laboratory microcosm study. We present evidence to show that microbes present in these sediments are able to reduce Fe(III) and As(V) when provided with an electron donor, and that the two sediments respond differently to stimulation with Fe(III) and As(V). Shifts in the community composition of the two sediments after stimulation with As(V) suggest a potential role for members of the beta-Proteobacteria in As(V) reduction, a phylogenetic grouping known to contain microorganisms capable of As(III) oxidation, but not previously implicated in As(V) reduction. PCR-based analysis of the sediment microbial DNA using primers specific to the arrA gene, (a gene essential for microbial As(V) respiration), indicates the presence of microorganisms capable of dissimilatory As(V) reduction.
Publisher: Elsevier BV
Date: 06-2001
DOI: 10.1016/S0021-9673(01)00553-2
Abstract: A method for the quantitative determination of the major anionic constituents of fountain solutions, typically mono-, di- and hydroxycarboxylates, alkylbenzenesulfonates, and inorganic anions, including orthophosphate and polyphosphates, is presented here for the first time. The analytical problems arising from extensive co-elution of many of these analytes on an ion-exchange column have been resolved through a combination of (i) careful selection of the concentration gradient of the sodium hydroxide eluent (ii) parallel analysis by ion-exclusion chromatography and (iii) determination of total phosphorus by inductively coupled plasma atomic emission spectrometry.
Publisher: American Chemical Society (ACS)
Date: 07-11-2006
DOI: 10.1021/ES060990+
Abstract: Poorly crystalline Fe(III) oxyhydroxides, ubiquitously distributed as mineral coatings and discrete particles in aquifer sediments, are well-known hosts of sedimentary As. Microbial reduction of these phases is widely thought to be responsible for the genesis of As-rich reducing groundwaters found in many parts of the world, most notably in Bangladesh and West Bengal, India. As such, it is important to understand the behavior of As associated with ferric oxyhydroxides during the early stages of Fe(lll) reduction. We have used X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) to elucidate the changes in the bonding mechanism of As(III) and As(V) as their host Fe(III) oxyhydroxide undergoes bacterially induced reductive transformation to magnetite. Two-line ferrihydrite, with adsorbed As(III) or As(V), was incubated under anaerobic conditions in the presence of acetate as an electron donor, and Geobacter sulfurreducens, a subsurface bacterium capable of respiring on Fe(lll), but not As(V). In both experiments, no increase in dissolved As was observed during reduction to magnetite (complete upon 5 days incubation), consistent with our earlier observation of As sequestration by the formation of biogenic Fe(III)-bearing minerals. XAS data suggested that the As bonding environment of the As(III)-magnetite product is indistinguishable from that obtained from simple adsorption of As(lll) on the surface of biogenic magnetite. In contrast, reduction of As(V)-sorbed ferrihydrite to magnetite caused incorporation of As5+ within the magnetite structure. XMCD analysis provided further evidence of structural partitioning of As5+ as the small size of the As5+ cation caused a distortion of the spinel structure compared to standard biogenic magnetite. These results may have implications regarding the species-dependent mobility of As undergoing anoxic biogeochemical transformations, e.g., during early sedimentary diagenesis.
Publisher: Mineralogical Society
Date: 04-2003
Abstract: The dispersion and sediment-water partitioning of Pb and Zn have been studied in the Conwy River, North Wales. Analysis included major and trace element water chemistry and concentrations of sediment-hosted Pb and Zn. In situ solution pH, Eh, temperature and conductivity were also measured. Sediments were characterized via SEM, XRD, nitric acid leaching and sequential chemical extraction to quantify metal distribution and sediment phase associations. Dissolved and sediment-bound Pb and Zn within river and estuary waters and sediments have been used to calculate whole sediment- and phase-specific apparent partition coefficients. Weathering of galena and sphalerite, associated with the Llanrwst Mining Field, provide point sources of elevated dissolved and sedimentary Pb and Zn in the upper catchment. Dissolved Pb is actively adsorbed onto sedimentary surface coatings of Fe-Mn (hydr)oxides and organics whilst Fe-Mn (hydr)oxides, organics and carbonates were the main hosts for Zn. Systematic changes in metal sorption are evident between the estuary and the upper catchment, with organic matter becoming progressively more important upstream. This change is ascribed to the sorptive properties of sedimentary organic material. Solution pH, [Cl] and aqueous metal speciation are the dominant solution controls on metal partitioning. Laboratory sorption experiments parallel Pb sorption behaviour in the natural system.
Publisher: Mineralogical Society of America
Date: 11-2007
DOI: 10.2138/AM.2007.2541
Publisher: Elsevier BV
Date: 12-2015
Publisher: Elsevier BV
Date: 11-2008
Publisher: Mineralogical Society
Date: 12-2003
Abstract: Knowledge of the solid-phase speciation of As in Bengali sediments associated with hazardous As-rich groundwaters is crucial to understanding the processes controlling As release. The local coordination environment of As in such a sediment has been probed using K-edge As EXAFS. This revealed that As exists predominantly in its oxidized form, As(V), probably adsorbed as bidentate arsenate tetrahedra on metal (Fe and/or Al) oxide/hydroxide surfaces, although incorporation of As into a metal oxide structure cannot be ruled out. Arsenic was found to occur in several different coordination environments and this, together with the low concentration ( μg g –1 ) of As in the sediment prevented the unambiguous assignment of the second coordination sphere. The EXAFS analysis of the sediment after incubation under anaerobic conditions in the presence of added electron donor for metal reduction indicated changes in the relative concentrations of different solid-phase As species, providing circumstantial evidence for differential susceptibility to microbial action.
Publisher: Elsevier BV
Date: 11-2008
Publisher: Springer Science and Business Media LLC
Date: 27-05-2010
DOI: 10.1007/S10653-010-9319-5
Abstract: Remediation aimed at reducing human exposure to groundwater arsenic in West Bengal, one of the regions most impacted by this environmental hazard, are currently largely focussed on reducing arsenic in drinking water. Rice and cooking of rice, however, have also been identified as important or potentially important exposure routes. Quantifying the relative importance of these exposure routes is critically required to inform the prioritisation and selection of remediation strategies. The aim of our study, therefore, was to determine the relative contributions of drinking water, rice and cooking of rice to human exposure in three contrasting areas of West Bengal with different overall levels of exposure to arsenic, viz. high (Bhawangola-I Block, Murshidibad District), moderate (Chakdha Block, Nadia District) and low (Khejuri-I Block, Midnapur District). Arsenic exposure from water was highly variable, median exposures being 0.02 μg/kg/d (Midnapur), 0.77 μg/kg/d (Nadia) and 2.03 μg/kg/d (Murshidabad). In contrast arsenic exposure from cooked rice was relatively uniform, with median exposures being 0.30 μg/kg/d (Midnapur), 0.50 μg/kg/d (Nadia) and 0.84 μg/kg/d (Murshidabad). Cooking rice typically resulted in arsenic exposures of lower magnitude, indeed in Midnapur, median exposure from cooking was slightly negative. Water was the dominant route of exposure in Murshidabad, both water and rice were major exposure routes in Nadia, whereas rice was the dominant exposure route in Midnapur. Notwithstanding the differences in balance of exposure routes, median excess lifetime cancer risk for all the blocks were found to exceed the USEPA regulatory threshold target cancer risk level of 10(-4)-10(-6). The difference in balance of exposure routes indicate a difference in balance of remediation approaches in the three districts.
Publisher: Royal Society of Chemistry (RSC)
Date: 2007
DOI: 10.1039/B613340A
Abstract: Millions of people in some of the poorest regions of the world are exposed to high levels of arsenic through drinking contaminated water. It has been reported that development of cancer caused by arsenic exposure in such populations is dependent on dietary and nutritional factors which can modulate arsenic metabolism. Many people in arsenic exposed regions of Bangladesh and India practice fasting for at least one month every year when they refrain from consumption of food and fluid during daylight hours. How such practices may modulate arsenic metabolism has not been previously investigated. This study investigated this issue by determining total arsenic and its species in urine s les from a group of 29 unexposed volunteers at the beginning of the fasting and at the end of approximately 12 h of fasting period. Inductively coupled plasma mass spectrometry (ICP-MS) and high performance liquid chromatography (HPLC) coupled with ICP-MS was used to measure the total arsenic and arsenic speciation in the urine s les, respectively. The mean total levels of arsenic at the beginning of fasting (18.3 microg g(-1) creatinine) and at the end of approximately 12 h of fasting (17.7 microg g(-1) creatinine) did not differ significantly (p > 0.05). However, the percentages of urinary arsenic as the methylated arsenic species methylarsonate (MA) were found to be significantly different (p 0.05) in both the concentrations and percentages of other urinary arsenic species detected, namely arsenobetaine (AB) and dimethylarsinate (DMA). Arsenite (As(III)) and arsenate (As(V)) were also analyzed, but were not detected. We conclude that fasting for a period of 12 h results in a significant increase in the percentage of urinary arsenic as MA, and its frequency of detection in the volunteers at the end of the fasting period is almost nine fold higher. This suggests that metabolism of arsenic is altered by fasting.
Publisher: MDPI AG
Date: 02-12-2020
Abstract: In our recently published meta-analysis, due to an oversight, we treated urinary As concentration data reported by Tsinovoi et al [...]
Publisher: CSIRO Publishing
Date: 2014
DOI: 10.1071/EN14006
Abstract: Environmental context Groundwater arsenic is a major environmental risk to human health in many regions of the world, including Cambodia where groundwater is often used for drinking water. We present data for hitherto poorly s led regions in Cambodia, notably around Tonle Sap and in the coastal provinces, and provide a geo-statistical model of arsenic in shallow groundwater for the whole country. Abstract Arsenic is a known environmental chemical hazard in shallow groundwaters of Cambodia and is increasingly recognised as a major problem for public health. Notwithstanding this, accurate arsenic data are not available for many wells in potentially arsenic-prone areas, particularly around the Tonle Sap Great Lake (TSL) and in the coastal provinces (CP). We present here new data for shallow groundwater (16–120-m depth) arsenic in the TSL and CP regions as well as an improved regression-kriging (RK) based groundwater arsenic hazard map for the whole country. High arsenic levels (up to 100μgL–1) were found in shallow groundwaters from the TSL and CP regions of Cambodia, but despite strong compositional similarities (near neutral, reducing, Na-Mg-Ca-HCO3 dominated) with high arsenic level groundwaters near the Mekong and Bassac rivers, groundwater arsenic levels in both the TSL and CP regions were most commonly low (interquartile range 0.09–1.2μgL–1). The RK geostatistical model was highly successful, accounting for over 50% of the observed variation in arsenic concentrations countrywide and represents a potentially useful tool for policymakers and those responsible and with the interest and authority to prepare arsenic mitigation and safe water supply plans.
Publisher: Elsevier BV
Date: 11-2008
Publisher: Society of Economic Geologists
Date: 08-1989
Publisher: Elsevier BV
Date: 08-2000
Publisher: Wiley
Date: 23-03-2007
Publisher: Elsevier BV
Date: 11-2008
Publisher: Elsevier BV
Date: 02-2001
Publisher: Elsevier BV
Date: 10-2000
Publisher: AIP
Date: 2007
DOI: 10.1063/1.2644477
Publisher: Springer Science and Business Media LLC
Date: 07-2004
DOI: 10.1038/NATURE02638
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for David Polya.