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In this study, we evaluated the cumulative effects of arsenic (III) oxide on the number of mouse offspring over three consecutive generations and monitored changes in levels of the reproductive hormones, oestradiol and progesterone in female mice during the dioestrus phase of the cycle. The control group received water from the mains. In two experimental groups, mice were given drinking water containing dissolved arsenic (III) oxide at concentrations of 10.6 mg L−1 and 106 mg L−1, respectively. These concentrations represent the values converted from a human model to an animal model (mice) thus correspond to the arsenic content of the groundwater in the southern part of the Pannonian Basin, in the province of Vojvodina, in the Banat region, in particular in the town of Zrenjanin. The average number of newborn mice in both experimental groups decreased for three consecutive generations. The total arsenic content of day-old mice did not show significant differences between the experimental groups. Arsenic (III) oxide affected the reproductive hormone levels of female mice at both concentrations. [ABSTRACT FROM AUTHOR]

The present study introduces a monitoring initiative focused on the quality of groundwater in the Piatra locality, situated in the North-West region of Romania. This paper employs an evaluation of 21 physico-chemical parameters, encompassing factors such as electrical conductivity, pH, chemical oxygen demand, turbidity, total hardness, NH4+, NO3−, Cl−, PO43−, Li, Na, K, Ca, Mg, Ba, Sr, Al, Fe, Mn, Sn, and Ti. Additionally, it examines five heavy metals (Cr, Cu, Ni, Pb, and Zn) and arsenic in water sourced from six distinct private wells. Each well, with its characteristics, serves as a unique drinking water source. The assessment encompassed the evaluation of pollution levels, quality status, and risk factors for all drinking water sources, utilizing pollution, quality, and risk indices. The aim of this study was to establish the level of toxicity in water, assess its impact on human health, and disseminate information to the public about the appropriate utilization of individual water sources. The results indicated a general contamination with chloride, ammonium, manganese, chromium, and iron. Human health risk assessment indices revealed that the consumption of studied waters presented non-carcinogenic risks associated with Cr for adults and with Cr, As, Pb, and Cu for children for some of the groundwater sources. The water quality index (WQI) categorizes the samples as possessing excellent and good quality. This research represents one of the initial endeavors to assess the groundwater source quality in connection with the potential human health risks posed by the metals studied within the protected area of the Tisa River Basin. [ABSTRACT FROM AUTHOR]

Due to groundwater contamination and runoff from certain mining operations, populations are exposed to detrimental levels of arsenic daily. The effects of arsenic exposure on the human epigenome are extensive, and some are still unknown. It can alter DNA methylation, inhibiting specific tumor suppressor genes and increasing the risk of neoplasia. This can be drawn back to certain crucial factors of DNA methylation, such as CpG Binding Proteins or DNA Methyl-transferases, all of which have shown linkage to carcinogenesis. Arsenic can also cause an overproduction of free radicals and a reduction of antioxidant production, causing oxidative stress. Lastly, it has also been associated with specific chromosomal abnormalities. All of these factors, which will be discussed in further detail, have been shown to contribute to the progression of cancer. [ABSTRACT FROM AUTHOR]

Special attention has been paid in recent years to the social and environmental implications of municipal solid waste. There are potential social and environmental issues associated with storing any waste in landfill. Soil, groundwater, and surface water contamination are issues related to landfill and the migration of contaminants by leaching to adjacent areas. The current research attempts to simulate the penetration of landfill contaminants through groundwater leaching, using PART modeling approaches. Multiple social factors, taken from five years of data from 20 counties and cities in Taiwan were used as predictors of groundwater arsenic content. The results indicate that the proposed model attains a precision rate of 87%. The findings suggest that county and city demographics and the volume of waste removed are two major factors in determining the arsenic content of groundwater. The proposed predictive model can be adopted by agencies as an effective early warning tool for groundwater arsenic levels. [ABSTRACT FROM AUTHOR]

Arsenic, a known carcinogen, naturally occurs in the groundwater in large parts of West Bengal, a state in eastern India. Communities that depend on groundwater face twice the lifetime mortality risk for cancers, cardiovascular diseases, and developmental disorders. This study, focused on arsenic-affected communities in the state of West Bengal, offers an initial exploration of how local stakeholders construct groundwater arsenic as a health problem. Arsenic remediation interventions involve a host of international, regional, and local stakeholders (public health departments, government engineers, community health workers, consultants, hydrologists, etc.). How an environmental health problem is constructed has implications for who is considered responsible, what causes it, and pertinently, how/whether affected communities participate in addressing the problem. Drawing from a culture-centered approach, this fieldwork-based study offers three distinct yet related problem construction discourses, viz. social/political, technical and personal, in how the problem of arsenic is construed locally, and how such discourses are related to a particular conceptualization of community participation in environmental health. [ABSTRACT FROM AUTHOR]

BACKGROUND: Arsenic content in shallow groundwater of the Yellow River alluvial fan plain exceeds the standard. A comprehensive understanding of the arsenic enrichment mode driven by the nitrogen cycle of shallow groundwater in the northern Henan Plain is essential for the sustainable use of groundwater resources and the health of residents. The main area of the North Henan plain is the Yellow River alluvial fan plain. The sedimentary environment in the northern Henan plain is complex, and is influenced by the Yellow River breach, diversion and oscillation, as well as alluvial diluvial in the mountainous area around the basin. The distribution, migration and release mechanism of As, NH+4 and NO-3 are quite different under different sedimentary environment conditions. The joint enrichment mechanism of the three is still unclear, which is worth further study. OBJECTIVES: To investigate the effect of nitrogen cycling on arsenic migration and enrichment in groundwater in the Northern Henan Plain. METHODS: 513 shallow groundwater samples were collected from the northern Henan Plain. Atomic fluorescence spectroscopy was used to determine the arsenic content, atomic absorption spectroscopy and ion chromatography, and other methods for major and trace element analysis. The correlation between nitrate, ammonia nitrogen and arsenic was investigated, and the influence of nitrogen cycle on the migration and enrichment of arsenic in groundwater was studied. RESULTS: The over-standard rate of arsenic concentration in shallow groundwater in the study area was 17.3%. The occurrence and transformation modes of nitrogen under different depositional environmental conditions were important driving factors for arsenic enrichment. A large amount of NO-3 was produced by nitrification in the groundwater of the alluvial fan in the piedmont alluvial fan, which had the average concentration of 9.3 mg/L and was the highest in the district. At the same time, the concentration of arsenic was the lowest in the district, with the average of 1.3μg/L. The good negative correlation between NO-3 and As concentration indicated that nitrification produced a large amount of NO-3, which was not conducive to the dissolution of arsenic-containing iron oxide. The depressions in front of the alluvial fan and the Yellow River crater fan with higher NH+4 content were the gathering places of high-arsenic groundwater. The average concentration of arsenic in groundwater from these two areas was 49.7μg/L and 18.9μg/L, respectively, and the exceeding rate reached 87.5% and 71.4%. The good positive correlation between arsenic content and NH+4 in groundwater indicated that the process of denitrification and dissimilative reduction of nitric acid to ammonium (DNRA) consumed NO-3 in groundwater and generated a large amount of NH+4, which promoted the reduction and dissolution of iron oxides that adsorbed arsenic, forming an environment rich in arsenic. CONCLUSIONS: The nitrogen cycle plays an important role in the migration and enrichment of arsenic. The migration and enrichment mode of arsenic driven by the nitrogen cycle provides a scientific basis for the treatment and supervision of groundwater with high arsenic content. [ABSTRACT FROM AUTHOR]

BACKGROUND: Arsenic pollution is a senous problem in shallow groundwater in the Hetao Basin, and has seriously affected the health of residents. The research on the distribution of high arsenic shallow groundwater in the Hetao Basin is limited by the sampling time and sample number. OBJECTIVES: To obtain a comprehensive understanding of the risk distribution characteristics and important influencing factors of high arsenic groundwater in different seasons in the region. METHODS: Based on 506 shallow groundwater samples and 9 surface environmental parameters as prediction variables, a random forest model was established to evaluate the importance of prediction variables and the impact of important variables on high arsenic groundwater. Taking the climate factors as the dynamic prediction variables, the probability distribution of high arsenic groundwater in different seasons was identified and thematic maps of risk areas were made. RESULTS: The results showed that the arsenic content of 506 groundwater samples ranged from 0. 05 to 916.7 µg/L with an overshoot rate ( > 10 µg/L) of 50% . Groundwater arsenic risk areas were mainly distributed in the depositional center of the Hetao Basin, but the area of groundwater arsenic risk areas decreased by 1907km² in winter, accounting for 14.14% of the total area. Precipitation and drought index, influence of drainage and irrigation channels, potential evapotranspiration and temperature were the most important indexes affecting the high arsenic groundwater in this area. CONCLUSIONS: In the Hetao Basin, climate variables ( precipitation and drought index) are significantly correlated with arsenic accumulation in the aquifer, which controls the seasonal variation of groundwater with high arsenic content in the depositional center of the Hetao Basin. [ABSTRACT FROM AUTHOR]

BACKGROUND: A typical irrigation area of the downstream Yellow River ( Henan) is an important agricultural planting area in the northern Henan Plain. The shallow water quality in this area is generally poor, which is often used for crop irrigation or livestock drinking, posing a risk to human health. Therefore, the study on the variation characteristics and mechanism of arsenic and fluorine content in groundwater in this area will help to improve the level of understanding of pollution in this area. OBJECTIVES: To investigate the spatial variation characteristics and mechanism of arsemc and fluorine concentration. METHODS: Based on 327 groups of shallow groundwater samples collected in 2010 and 2020 in the irrigated area, the distribution of arsenic and fluorine in the groundwater of the irrigated area was analyzed, and compared to the evolution characteristics of arsenic and fluorine in the shallow groundwater of the irrigated area in the last ten years. RESULTS: In 2020, the number of samples with high arsenic concentration (> 10 µg/L) and high fluorine concentration (> 1mg/L) in shallow groundwater accounted for 26.1% and 26.06%, respectively. The high - arsenic groundwater was distributed in the sedimentary environments with interbedding structure of sediment, such as the Taihang Mountain depression and the Yellow River alluvial plain, with strong reducibility, poor groundwater runoff and strong cation exchange, resulting in high concentration of Ca2+ in the environment. Arsenic concentration increased in 31.8% of water samples and decreased in 36.7% of water samples in the last ten years. The increase of arsenic content was caused by the dissolution and release of manganese oxide due to the enhanced reducibility of groundwater. The variation of water level caused by agricultural irrigation and water replacement in different areas during the last ten years was a potential factor of arsenic concentration change. The high - fluorine groundwater was mainly distributed along the Yellow River in Xinxiang and Puyang, Henan Province. The concentration of fluorine ion was affected by the dissolution of calcareous minerals such as fluorite in the sediments, which made the high - fluorine groundwater appear in the low - calcium environment. In the last ten years, the study area with decreased fluorine ion concentration accounted for 60.2%, whereas areas with increased fluorine ion concentration accounted for 32.1% . The overall change trend was good, but the fluorine ion concentration m the high fluorine area continued to increase. Changes in fluorine concentration were also affected by changes m Ca2+, with further increases ( decreases) as Ca2+ concentration decreased ( increased). Elevated fluorine m groundwater was distributed along the Yellow River, affected greatly by the Yellow River water supply. So, the groundwater flow condition was good and the cation exchange was weakened, reducing the Ca2+ content. At this time, the arsenic content in the groundwater was less affected by the environment, so the study area with fluorine increase showed an inverse relationship between arsenic and fluorine in terms of regional distribution and evolution. CONCLUSIONS: This study will provide support for rational utilization of groundwater in the study area. [ABSTRACT FROM AUTHOR]

The geochemical analysis of the shallow aquifer sediments of the area of investigation reveals that they are acidic in nature. The mean electrical conductivity of the deposits is 1.16 dS/m that indicates very low or negligible effects of salinity of the sediments of the Rangpur division. The median values of the concentrations of total organic carbon, total nitrogen and sulphur are 0.20%, 0.02% and 58.68 mg/kg, respectively. The trend of the average heavy metal concentrations of the investigated area can be shown as Fe > As > Cu > Zn. The average concentrations of arsenic of the sediments of the study area are 3.52 mg/kg. Sulphur is significantly, positively correlated with copper and zinc (p < 0.05) and insignificantly and positively correlated with arsenic content of the sediments that indicates that the copper and zinc occur as sulphide minerals. The mean concentrations of arsenic in the groundwater are 1.1793 μg/L. The concentration of all the water samples is below the permissible limit of World Health Organization (10 μg/L). The arsenic content of groundwater shows the positive correlations with the arsenic, iron and copper concentrations of the sediments. This implies that the arsenic of groundwater derived from the geogenic source, like the dissolution of arsenic bearing minerals of the aquifer sediments—pyrite and arsenopyrite. The acidic nature, texture and minor quantities of total organic carbon are the factors that also influence the low arsenic enrichment in the investigated sediments and its release to the groundwater. The contemporary arsenic specification research works showed that As(III) the most common species in natural water and foodstuffs and the arsenic is inorganic from source in Bangladesh. [ABSTRACT FROM AUTHOR]

Human biomarkers were used to evaluate the lead (Pb) and arsenic (As) exposure of local people who lived in an agricultural area with intense agrochemical usage and who consumed groundwater. Although the heavy metals/metalloids in the groundwater were at low concentrations, they could cause adverse effects due to a high daily water intake rate over the long term. Biomarkers (hair, fingernails and urine) were collected from 100 subjects along with the local shallow groundwater and tap water, which is the treated deep groundwater, and investigated for the concentrations of As and Pb. Shallow groundwater had an average pH of 5.21 ± 1.90, ranging from 3.77 to 8.34, with average concentrations of As and Pb of 1.311 µg/L and 6.882 µg/L, respectively. Tap water had an average pH of 5.24 ± 1.63, ranging from 3.86 to 8.89, with the average concentrations of As and Pb of 0.77 µg/L and 0.004 µg/L, respectively. The levels of both As and Pb in the hair, fingernails and urine of shallow groundwater-consuming residents were greater than those in the hair, fingernails and urine of tap water-consuming residents. Interestingly, the As level in urine showed a linear relationship with the As concentration in groundwater (R2 = 0.91). The average water consumption rate was approximately two-fold higher than the standard; thus, its consumption posed a health risk even at the low As and Pb levels in the groundwater. The hazard index (HI) ranged from 0.01 to 16.34 (average of 1.20 ± 2.50), which was higher than the acceptable level. Finally, the concomitant factors for As and Pb in the urine, hair and nails from both binary logistic regression and odds ratio (OR) analysis indicated that groundwater consumption was the major concomitant risk factor. This study suggested that direct consumption of this groundwater should be avoided and that the groundwater should be treated, especially before consumption. In conclusion, urine is suggested to be a biomarker of daily exposure to As and Pb, while for long-term exposure to these metals, fingernails are suggested as a better biomarker than hair. [ABSTRACT FROM AUTHOR]

Naturally occurring arsenic in groundwater affects millions of people worldwide. We created a global prediction map of groundwater arsenic exceeding 10 micrograms per liter using a random forest machine-learning model based on 11 geospatial environmental parameters and more than 50,000 aggregated data points of measured groundwater arsenic concentration. Our global prediction map includes known arsenic-affected areas and previously undocumented areas of concern. By combining the global arsenic prediction model with household groundwater-usage statistics, we estimate that 94 million to 220 million people are potentially exposed to high arsenic concentrations in groundwater, the vast majority (94%) being in Asia. Because groundwater is increasingly used to support growing populations and buffer against water scarcity due to changing climate, this work is important to raise awareness, identify areas for safe wells, and help prioritize testing. [ABSTRACT FROM AUTHOR]

Groundwater through hand-operated tubewell (a type of water well) tapping is the main source of drinking water in Bangladesh. This study investigated iron and manganese concentration in groundwater across Jashore district–one of the worst arsenic contaminated area in Bangladesh. One working tubewell that had been tested previously for arsenic and marked safe (green) was selected from each unions of the district. Results revealed that approximately 73% and 87% of groundwater samples exceeded the limits for iron and manganese in Bangladesh drinking water, respectively. Additionally, spatial distribution of iron and manganese indicate that only 5% of the total surface area of groundwater is covered by safe level of iron and manganese. Human health risk due to ingestion of iron and manganese through drinking water was evaluated using hazard quotients (HQ) for adults and children. The result of the health risk assessment revealed that the non-carcinogenic health risks due to ingestion of iron (HQ up to 1.446 for adults and 0.590 for children) and manganese (HQ up to 2.459 for adults and 1.004 for children) contaminated groundwater are much higher among adults than children. On the basis of occurrences, spatial distribution and health risk assessment results, the area can be categorized as a high-risk zone for iron and manganese-related problems and needs special attention in order to protect public health of local residents. [ABSTRACT FROM AUTHOR]

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The influence of aquifer sediments provenance and geochemical processes on groundwater solute chemistry, including the fate of groundwater arsenic (As) in aquifers for three distinct tectono-morphic zones (north-western, northern, and southern [NW, N, and S] in the basin of Himalayan Mega Rivers, i.e., Brahmaputra river basin (BRB), and adjoining the Himalayas and Indo-Burmese ranges, have been delineated. The presence of fluvial re-worked quartz, feldspar, and mica along with orogeny-sourced ferromagnesian minerals contained aquifers sediments in the NW and N regions are hypothesized to be derived from the Himalayan system. The S-aquifers mineralogy differs from northern aquifers by a higher proportion of Fe/Mg aluminosilicates, phyllosilicates/clay minerals, derived from the Indo-Burmese ranges. The dissolved As distribution is highly variable among the different alluvial aquifers. The S-region is highly enriched in groundwater As (bdl to 5.53 μM or 415 μg/L, mean 1.77 μM) compared to NW and N regions (bdl to 1.8 μM or 134 μg/L, mean 0.28 μM [60% As-contaminated samples]; bdl to 2.45 μM or 184 μg/L, mean 0.68 μM [65% As-contaminated samples] respectively). More than 92% of groundwater samples in the S-region are enriched with As (>50 μg/L), which draws a distinct difference from the NW and N regions of BRB aquifers. Reaction-path models suggest intense chemical weathering of S-aquifer matrix due to the higher equilibrium (more stable) of secondary mineral phases with the solution (groundwater), as compared to NW and N regions. The present study proposes a model for the geological control and effect of weathering/water–sediment reaction on As-fate and mobilization mechanism in the groundwater system of the barely studied Brahmaputra river basin aquifers. Image 1 • Water-sediment interaction dominates groundwater evolution. • A model of arsenic (As) influx and mobilization in study area is proposed. • Geology is hypothesized to be a major influencing factor for hydrogeochemistry • Tectonics influence the sediment provenance for groundwater arsenic content. [ABSTRACT FROM AUTHOR]

Numerous studies have shown that groundwater is naturally contaminated with arsenic exceeding 10 µg/l in the western and central area of Romania. Arsenic contaminated drinking water is a health hazard; therefore, the purpose of this study was to evaluate the exposure to arsenic in drinking water within a population group. In 2014 we recruited 25 subjects from Covasna County, Romania. Participants completed a questionnaire and we collected water samples from drinking water sources (springs and tap) and nail samples. Arsenic concentrations were determined by hydride generation atomic absorption spectrometry. Exposure doses and cancer risk were calculated individually for each subject, following a methodology developed by the US Agency for Toxic Substances and Disease Registry. Arsenic concentrations ranged from 0.5 to 91.8 µg/l, with mean 22.16±37.44 µg/l (mean±SD), in drinking water; and ranged from 0.04 to 100.30 µg/g, with mean 16.90±20.97 µg/g (mean±SD) in nail samples. Exposure doses were above MRL (minimal risk level) for chronic exposure for 3 subjects. Risk estimations predicted a theoretical risk of 5 excess cancer cases in a population of 10,000. Groundwater sources are a potential health hazard for the population in the area, thus due to the limitations of the present study, further studies are needed with extended no of participants and additional individual data. [ABSTRACT FROM AUTHOR]

Elevated inorganic arsenic concentrations in groundwater has become a major public and environmental health concern in different parts of the world. Currently, As-contaminated groundwater issue in many countries and regions is a major topic for publications at global level. However, there are many regions worldwide where the problem has still not been resolved or fully understood due to inadequate hydrogeochemical investigations. Hence, this study evaluates for the first time the hydrogeochemical behavior of the arid and previously unexplored inland basin of Sirjan Plain, south east (SE) Iran, in order to assess the controlling factors which influence arsenic (As) mobility and its distribution through groundwater resources. Total inorganic arsenic concentration was measured using inductive-coupled plasma optical emission spectrometry (ICP-OES). Arsenic content in groundwater of this region ranged between 2.4 and 545.8 μg/L (mean value: 86.6 μg/L) and 50% of the samples exceeded the World Health Organization (WHO) guideline value of 10 μg/L in drinking water. Groundwater was mainly of Na-Cl type and alkaline due to silicate weathering, ion exchange and evaporation in arid conditions. Elevated As concentrations were generally observed under weakly alkaline to alkaline conditions (pH > 7.4). Multivariate statistical analysis including cluster analysis and bi-plot grouped As with pH and HCO 3 and demonstrated that the secondary minerals including oxyhydroxides of Fe are the main source of As in groundwater in this region. The desorption of As from these mineral phases occurs under alkaline conditions in oxidizing arid environments thereby leading to high levels of As in groundwater. Moreover, evaporation, ion exchange and saltwater intrusion were the secondary processes accelerating As release and its mobility in groundwater. Based on the results of this study, desorption of As from metal oxy-hydroxides surfaces under alkaline conditions, evaporation and intrusion of As-rich saline water are considered to be the major factors causing As enrichment in arid inland basins such as those in southeast Iran. This study proposes the regular monitoring and proper groundwater management practices to mitigate high levels of arsenic in groundwater and related drinking water wells of Sirjan Plain. Image 1 • This study reveals geogenic As of groundwater in previously unexplored Sirjan plain, Iran. • 50% of groundwater samples exceed the drinking water guideline value for As. • Groundwater is predominantly of Na-Cl type and alkaline nature. • Oxyhydroxides of Fe are the main sources of As in groundwater. • Evaporation, ion exchange and saltwater intrusion processes enhance As mobility. [ABSTRACT FROM AUTHOR]

The present paper starts by presenting an overview of the arsenic contamination in the groundwater in different parts of India. The paper goes on to present standards regarding arsenic in drinking water and then proceeds to give a statewise status of Arsenic contamination. Adverse effects of arsenic on the health of human beings, accumulation of arsenic in the food chain and ill-effects of using arsenicladen water for irrigation are elaborated upon in the paper. The paper proceeds to explore technological options to deliver arsenic-free water by various ways and means. Providing medical relief to affected people is also included. Methods for safe disposal of arsenic-laden sludge from arsenic filters and various issues related to the same are also key aspects of the paper. [ABSTRACT FROM AUTHOR]

Abstract Low-arsenic (As) groundwater from Pleistocene aquifers is vulnerable to future geogenic and allogenic arsenic pollution in South and Southeast Asia, threatening the millions who use it as a "safe source" of drinking and irrigation water. The abundance and chemical reactivity of iron and manganese oxides within these aquifer sediments control the occurrence and mobility of arsenic. In the present study, sediment samples varying in As, Fe, and Mn content were obtained from a Pleistocene aquifer in the Kandal Province of Cambodia. Laboratory and spectroscopic characterization of the sediment combined with groundwater analyses revealed that the availability and abundance of sedimentary As varied across a Pleistocene aquifer from the pore to field scales. Concentrations of sediment As (0.47–7 μg/g) correlated more strongly with Fe (R2 > 0.66) than with Mn (R2 > 0.35) concentrations in sediment well cuttings and tended to peak between 10 and 15 m. Chemical extractions and X-ray adsorption spectroscopy indicated the majority of As was strongly adsorbed to aquifer sediments or coprecipitated in oxides in the form of As(V) but that As(III) could be found in sediment microenvironments across the aquifer. Groundwater chemistry and Mn mineralogy indicated that the Pleistocene aquifer was suboxic, with average dissolved oxygen of 1.9 mg/L (±0.9 mg/L), redox potential of 0.155 V (±0.097 V), and abundant Mn(III/IV) oxide minerals. According to our results, allogenic As transport and geogenic As release will likely be dictated by localized geochemical processes that vary over a range of scales. Collectively, the specific Fe and Mn mineralogy and content within aquifers will ultimately govern As pollution potential, so understanding their multi-scale distributions and variability is essential for better predicting future risks to well-water quality in currently low-As aquifers. [ABSTRACT FROM AUTHOR]

High arsenic groundwater contamination causes serious health risks in many developing countries, particularly in India and Bangladesh. The arsenic fluxes in aquifers are primarily controlled by bacterial populations through biogeochemical cycle. In this present study, two gram-positive rod-shaped bacteria were isolated from shallow aquifers of Bhojpur district in Bihar during the early winter season, able to withstand arsenite (As3+) concentration upto 70 mM and 1000 mM of arsenate (As5+) concentration. They showed high resistance to heavy metals up to 30 mM and utilized some complex sugars along with different carbon sources. Growth at wide range of temperature, pH and salinity were observed. Both these isolates showed high efficiency in converting As3+ into less toxic concentrations of As5+ respectively from arsenic enriched culture media. Along with superior arsenic transformation and arsenic resistance abilities, the isolates showed a wide variety of metabolic capacity in terms of utilizing a variety of carbon sources under aerobic conditions, respectively. This study reports the potential As3+-oxidizing bacteria that can play an important role in subsurface arsenic transformation that will aid in designing future bioremediation strategy for the arsenic affected areas. [ABSTRACT FROM AUTHOR]

In this work, feasibility of electrocoagulation (EC) process with Al and Fe scrap anodes for treatment of groundwater contaminated with arsenic (As) was examined as a cheaper treatment alternative for affected remote communities. EC experiments were carried out in a batch packed-bed EC reactor and the effect of applied current (0.010–0.100 A), type of scrap electrode (Fe and Al), packed-bed density (0.1–0.4 kg/m³ for Fe and 0.02–0.08 kg/m³ for Al) and EC time were investigated. Optimum operating conditions to obtain maximum contaminant level (MCL) of 10 μg /L for total As (>93% removal) in groundwater samples were determined as 8 min and 0.05 A for Fe scrap anodes. Whereas for Al scrap anode, 30 min and 0.10 A were the optimums. The operating cost, energy and electrode consumptions at these optimums were calculated as 0.017 US $/m³, 0.070 kW h/m³ and 0.052 kg/m³ for Fe anodes and 0.181 US $/m³, 0.876 kW h/m³ and 0.067 kg/m³ for AL anodes respectively. The As removal slightly decreased with decrease in anode bed density. Moreover, Fe scrap anodes exhibited better As removal than the Al scrap anodes at all tested conditions. The scanning electron microscopy (SEM) of the electro-coagulated sludge revealed irregular and porous particles with amorphous structure. The Fourier-transform infrared spectroscopy (FTIR) showed bonding between Fe(III) - As(V), and As—O bond, confirming As removal by co-precipitation and adsorption, respectively in the EC process. [ABSTRACT FROM AUTHOR]

Inorganic arsenic species determination is important to measure health hazards and to interpret in the best possible way clinical signs within populations drinking exposed water. This study was performed on groundwater samples from northern Burkina Faso using a portable electroanalytical apparatus in order to assess the proportion of As (III) versus As (V) when analyzed on site and during conservation. Two different treatment methods of water samples were performed and analyzed for their ability to maintain the initial As species content. The samples conserved with HCl and EDTA in white non opaque bottles were subsequently analyzed at days 7 and 21 post sampling. The investigations showed that arsenic (V) species were the most predominant form in the twenty-one studied samples. In general, regardless of their treatment, arsenic (III) species were spontaneously converted into the arsenic (V) during conservation. The arsenic (III) form, however, was kept for three samples until day 7 and for two of them until day 21. [ABSTRACT FROM AUTHOR]

Abstract Contamination of groundwater with toxic arsenic (As) has become an emerging health and environmental problem around the world, which has seen significant attention amongst the scientists for development of new sorbents to remediate As-contaminated water. Here, we explored the arsenate (As(V)) and arsenite (As(III)) sorption to natural water melon rind (WMR), xanthated WMR and citric acid-modified WMR in aqueous solutions, and determined potential of the most potent sorbent for As removal in groundwater. Xanthated WMR (X-WMR) showed relatively higher As(V) and As(III) removal than the citric acid modified WMR (CA-WMR) and natural WMR. The maximum As(III) (99%) and As(V) (98%) removal was obtained at pH 8.2 and 4.6, respectively, by X-WMR at 4 mg L−1 initial As(V) and As(III) concentrations and sorbent dose of 1 g L−1. Langmuir isotherm model best fitted (R 2 of up to 0.96) the data both for As(III) and As(V) sorption to X-WMR. Sorption kinetics of As(V) and As(III) was well described (R 2 of up to 0.99) by the pseudo second-order model on surface of the X-WMR. Thermodynamic investigations revealed that As(V) and As(III) sorption was endothermic and spontaneous. The FTIR spectroscopy depicted the presence of different surface function groups (OH, COOH, S-bearing (C=S, S=O and S–S)) which were involved in As(V) and As(III) sequestration on the sorbents examined here. Significantly, X-WMR showed (up to 49%) greater As(III) and As(V) sorption than that of natural WMR. Our results demonstrated that X-WMR efficiently removed 94%–100% (n = 16) of As from As-contaminated drinking well water which possessed detectable concentrations of some anions (e.g., SO 4 , CO 3 , HCO 3). This study highlights that the X-WMR has potential to remove As, notably As(III), from solutions and drinking water, and might be utilized as a reactive medium for the treatment of As-contaminated water. Graphical abstract Unlabelled Image Highlights • Water melon rind (WMR) was tested for arsenic removal potential from water. • Xanthated WMR removed up to 99% of As(III)/As(V) in solutions. • Langmuir and pseudo second-order models provided the best fits for As(III) and As(V). • FTIR spectra showed arsenic sequestration with surface functional groups of sorbents. • Xanthated WMR successfully removed 94–100% arsenic from drinking well water. [ABSTRACT FROM AUTHOR]

Abstract The role of post harvesting procedures for producing parboiled rice grain using arsenic (As) contaminated groundwater in rural Bengal was investigated. Considerable high concentrations of As (mean: 186 μg/kg) were found in about 82% of parboiled rice grain samples compared to raw or non-parboiled rice grain samples (66 μg/kg in 75% samples) obtained from Deganga, a highly As affected zone located in West Bengal, India. This observation instigated to study the additional entry of As at various stages of parboiling. A maximum increase of 205% of As content in parboiled rice grain was observed. Significant increase in parboiled whole grain As concentration was dependent upon the large difference between As concentrations of the water and the raw whole grain used for parboiling. Arsenic concentrations of water samples collected at raw, half boiled and full boiled stages of parboiling increased, irrespective of their initial concentration due to reduction in final volume during parboiling process. Principle component analysis shows a positive correlation of As concentration of rice grain to that in the groundwater being used in post harvesting procedure. Moreover, partitioning studies of As in whole grain indicated higher accumulation of As content in individual rice grain than that in their respective husks implying higher risk of exposure on ingestion of these contaminated rice grains. It is therefore, suggested to employ novel methods such as rain water harvesting or surface water channelling to make As free water available for parboiling process to curtail the entry of additional As in parboiled rice. Graphical abstract Image 1 Highlights • Parboiled rice and its by-products accumulate arsenic (As) more than raw rice. • Parboiling with As contaminated water contributes As to parboiled rice grain. • Arsenic content in rice grain is comparatively higher than the outer husk. • Use of As free water during parboiling is vital to minimise additional As exposure. [ABSTRACT FROM AUTHOR]

High arsenic (As) groundwater has been found in Pliocene confined aquifers at depths from 100 to 300 m of the Guide basin, but little is known on the main hydrogeochemical processes leading to its elevated concentrations. Ninety-seven water samples and fifty-three sediment samples were collected for chemical and/or isotopic analysis. Concentrations of As in groundwater of confined aquifer range from 9.9 to 377 μg/L (average 109 μg/L), which generally show a sharply increasing trend along with NH 4 + , HCO 3 − , CO 3 2− and TOC along the inferred flow path, while NO 3 − , SO 4 2− /Cl − and redox potential (Eh) have decreasing trends. Results of sequential extraction show that As bound to amorphous and crystalline Fe oxide minerals are the main As forms, accounting for around 50% of total As in sediments. Reductive dissolution of As-bearing Fe(III) oxide minerals under reducing conditions in confined aquifers lead to the mobilization of As in groundwater. In addition, alkaline environment and high concentrations of HCO 3 − and CO 3 2− may make contributions to As enrichment in groundwater. High As groundwater in confined aquifer continuously flows out on the ground surface through tens of artesian wells, which may potentially contaminate low As groundwater in unconfined aquifer. Thus, further investigation is needed to evaluate long-term variations of water chemistry of low As groundwater and assess vulnerability of unconfined aquifer to As contamination. [ABSTRACT FROM AUTHOR]

Abstract As widely known, in several countries in South East Asia, arsenic concentrations in ground water extracted from Quaternary alluvial sediments frequently exceed the World Health Organization (WHO) drinking water guideline of 10 μg/L. The broadly accepted hypothesis states that reductive dissolution of Fe-bearing minerals releases As-oxyanions contained within these minerals. According to the results presented in this article, As and Fe concentrations in ground water in the lowlands (Terai) of Nepal are highly variable as a function of location and there is a de-coupling of As and Fe concentrations resulting in a loss of correlation between these two elements. The mean concentrations of As and of Fe in 35 wells were slightly higher in the post-monsoon than in the pre-monsoon season. Even though As is mainly associated with iron(hydr)oxides, a substantial portion of As and Fe can be retained by clay minerals (including micas). During pre-monsoon (dry season) clayey sediments are chemically weathered losing Na and K thus remaining relatively enriched in less mobile elements such as Fe and Al. As long as reducing conditions persist, As remains relatively mobile. This article includes a detailed discussion referring to the very weak correlation or decoupling between aqueous As and Fe in the ground water and addresses possible consequences for water treatment. It sheds light on the original reservoir of arsenic being incorporated and released from clay minerals as well as from iron(hydr)oxides. Highlights • Climatic variations influence arsenic and iron concentrations in contaminated ground water. • The concentration of arsenic in ground water is decoupled from iron. • Concentrations of As correlate positively with Li, B, Na, and Mo, and negatively with Ca and Mn. • In addition to Fe(hyr)oxides, clay minerals are carriers of arsenic. [ABSTRACT FROM AUTHOR]

To understand occurrence, distribution and source of arsenic, 175 groundwater samples from coastal aquifers of the Puducherry region were collected and analyzed for major ions and trace metals. The concentration of As in groundwater of study area ranges from not detectable — 28.88 μg/L during the post-monsoon and not detectable — 36.88 μg/L in the pre-monsoon. The desirable limit for As in groundwater is 10 μg/L as per World Health Organization and Bureau of Indian standard. About 13.64 and 11.50% of groundwater samples shows arsenic concentration higher than recommended limit. Hydrochemical facies which dominate during pre and post monsoon are Na-K-Cl-SO 4 , Ca-Cl and Ca-Mg-Cl-SO 4 type and Na-K-Cl-SO 4 , mixedCa-Na-HCO 3 , Ca-HCO 3 and mixed Ca-Mg-Cl type respectively. The Gibbs diagram suggested that rock-water interaction is major process controlling hydrochemistry of groundwater. From the Pourbaix diagram, it is inferred that H3AsO3 is the principal As species in groundwater. The PHREEQC modelling indicates supersaturation of ferric oxides and hydroxide mineral phases in aquifer system which on reductive dissolution releases arsenic into groundwater. Statistical analysis (Spearman Correlation and Principal Component Analysis) showed that reductive dissolution of As-bearing minerals and Fe-oxyhydroxides in the presence of organic matter is the major process contributing arsenic into groundwater. The relationship between As, K + and HCO − 3 indicates agricultural and competitive exchange process which is an additional contributor of arsenic in groundwater. The sources which act as a sink and responsible for the release of As into the groundwater are marine sediments enriched in As and Fe-bearing minerals and organic matter. [ABSTRACT FROM AUTHOR]

Groundwater arsenic contamination is a common environmental problem that threatens the health of over 100 million people globally. Apparent seasonal fluctuations in groundwater arsenic concentrations have been reported in various locations worldwide, including the Jianghan Plain, central China. This phenomenon has been attributed to shifts in redox conditions induced by seasonal incursions of surface water. However, it is not clear what processes during the incursion lead to changes in the redox conditions and what is the source of the organic carbon driving these processes. Therefore, we conducted a long-term investigation of stable carbon isotopic compositions in surface water and groundwater, as well as long-term monitoring of hydraulic gradients and geochemical compositions at the Jianghan Plain. Results indicated that a series of biogeochemical processes occurred during surface water incursion, including aerobic microbial respiration, nitrate and sulfate reduction. Groundwater arsenic was removed by adsorption on iron oxyhydroxides produced during oxidation of ferrous iron, resulting in dramatic decreases in arsenic concentrations during surface water recharge seasons. These processes were likely driven by organic carbon vertically transported from surface water and released from the surficial aquitard above 15 m. Groundwater pumping may accelerate the vertical infiltration of oxidizing recharge water and drive exogenous organic carbon to depth. Findings of this study advance the understandings of the mechanisms that cause temporal variations in groundwater As and the importance of exogenous organic carbon that may influence the temporal behavior of arsenic in groundwater. [ABSTRACT FROM AUTHOR]

The paddy soils in some areas in Jianghan Plain were severely contaminated by arsenic. However, little is known about the activity and diversity of the dissimilatory arsenate-respiring prokaryotes (DARPs) in the paddy soils, and the effects of sulfate on the microbial mobilization and release of arsenic from soils into solution. To address this issue, we collected arsenic-rich soils from the depths of 1.6 and 4.6 m in a paddy region in the Xiantao city, Hubei Province, China. Microcosm assays indicated that all of the soils have significant arsenate-respiring activities using lactate, pyruvate or acetate as the sole electron donor. Functional gene cloning and analysis suggest that there are diverse DARPs in the indigenous microbial communities of the soils. They efficiently promoted the mobilization, reduction and release of arsenic and iron from soils under anaerobic conditions. Remarkably, when sulfate was amended into the microcosms, the microorganisms-catalyzed reduction and release of arsenic and iron were significantly increased. We further found that sulfate significantly enhanced the arsenate-respiring reductase gene abundances in the soils. Taken together, a diversity of DARPs in the paddy soils significantly catalyzed the dissolution, reduction and release of arsenic and iron from insoluble phase into solution, and the presence of sulfate significantly increased the microbial reactions. [ABSTRACT FROM AUTHOR]

Arsenic methylation is regarded as an effective way of arsenic detoxification. Current knowledge about arsenic biomethylation in high arsenic groundwater remains limited. In the present study, 16 high arsenic groundwater samples from deep wells of the Hetao Plain were investigated using clone library and quantitative polymerase chain reaction (qPCR) analyses of arsM genes as well as geochemical analysis. The concentrations of methylated arsenic (including monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA)) varied from 2.40 to 16.85 μg/L. Both bacterial and archaeal arsenic methylating populations were detected in the high arsenic aquifer. They were dominated by Proteobacteria, Firmicutes, Gemmatimonadetes, Nitrospirae, Methanomicrobia and a large unidentified group. The abundances of predominant populations were correlated positively to either total organic carbon or total arsenic and arsenite concentrations. The arsM gene abundances in high arsenic groundwater ranged from below detection to 5.71 × 106 copies/L and accounted for 0-3.32‰ of total bacterial and archaeal 16S rRNA genes. The arsM gene copies in high arsenic groundwater showed closely positive correlations with methylated arsenic concentrations. The overall results implied that arsenic methylating microorganisms were abundant and diverse in high arsenic groundwater. This was the first study of arsenic methylating microbial communities in high arsenic groundwater aquifers and might provide useful information for arsenic bioremediation in groundwater systems. [ABSTRACT FROM AUTHOR]

Despite increasing mining activities, and fertilizer and pesticide use in agriculture, little information is available on the status of metal(loid) contamination in rivers in West Africa. Sixty water samples were collected from three significant rivers (the Bandama, Comoé, and Bia Rivers) in Côte d’Ivoire, the world’s top cocoa producer, to examine As, Pb, Cu, Fe, Cd, and Zn concentrations, partitioning, and distribution in suspended particle-size fractions. The results showed higher total metal(loid) concentrations during the dry and flood seasons than during the rainy season. Significant As and Pb concentrations, moderate Cu and Fe concentrations, and low Zn concentrations were observed during the flood season. The metal(loid) concentrations decreased upstream to downstream primarily due to increased deposition through flocculation. Inverse or no obvious spatial trends often were observed, indicative of local contamination from anthropogenic activities. The suspended solid phase and the strength of metal affinity to the particles controlled the metal(loid) concentrations. Furthermore, total metal(loid) concentrations increased significantly with decreasing suspended particle-size fractions. The results underline that As and Pb contents in the Comoé and Bia Rivers threaten the health of at least 3 million people in southeastern Côte d’Ivoire. Filtering river waters before use will significantly reduce human health risks. [ABSTRACT FROM AUTHOR]

Molecular and eco-physiological characterization of arsenic (As)-transforming and hydrocarbon-utilizing Achromobacter type strain KAs 3-5T has been investigated in order to gain an insight into As-geomicrobiology in the contaminated groundwater. The bacterium is isolated from As-rich groundwater of West Bengal, India. Comparative 16S rRNA gene sequence phylogenetic analysis confirmed that the strain KAs 3-5T is closely related to Achromobacter mucicolens LMG 26685T (99.17%) and Achromobacter animicus LMG 26690T (99.17%), thus affiliated to the genus Achromobacter. Strain KAs 3-5T is nonflagellated, mesophilic, facultative anaerobe, having a broad metabolic repertoire of using various sugars, sugar-/fatty acids, hydrocarbons as principal carbon substrates, and O2, NO3−, NO2−, and Fe3+ as terminal electron acceptors. Growth with hydrocarbons led to cellular aggregation and adherence of the cells to the hydrocarbon particles confirmed through electron microscopic observations. The strain KAs 3-5T showed high As resistance (MIC of 5 mM for As3+, 25 mM for As5+) and reductive transformation of As5+ under aerobic conditions while utilizing both sugars and hydrocarbons. Molecular taxonomy specified a high genomic GC content (65.5 mol %), ubiquinone 8 (UQ-8) as respiratory quinone, spermidine as predominant polyamine in the bacterium. The differential presence of C12:0, C14:0 2-OH, C18:1 ω7c, and C 14:0 iso 3-OH/ C16:1 iso fatty acids, phosphatidylglycerol (PG), phosphatidylcholine (PC), two unknown phospholipid (PL1, PL2) as polar lipids, low DNA-DNA relatedness (33.0-41.0%) with the Achromobacter members, and unique metabolic capacities clearly indicated the distinct genomic and physiological properties of strain KAs 3-5T among known species of the genus Achromobacter. These findings lead to improve our understanding on metabolic flexibility of bacteria residing in As-contaminated groundwater and As-bacteria interactions within oligotrophic aquifer system. [ABSTRACT FROM AUTHOR]

Pyrite (FeS 2 ) is the most common sulfide mineral in the Earth's crust, and it commonly contains minor amounts of arsenic. Here we show that authigenic pyrite can remove arsenic from contaminated groundwater and this can be used as a new and relatively inexpensive remediation process. Laboratory batch experiments presented show that fine-grain natural pyrite is an effective sorber of dissolved arsenic. Arsenic sorption onto pyrite is shown to increase with increasing pH, particularly at pH > 5 and at elevated dissolved arsenic concentration. We also present results from a field experiment at an arsenic-contaminated industrial site, which demonstrates the results of stimulation of natural sulfate-reducing bacteria in groundwater by injection of a labile organic carbon source, iron, and sulfate. Within a week, bacterial sulfate reduction triggered the formation of biogenic pyrite nanoparticles, which sequestered arsenic by adsorption and co-precipitation. Microscopic and X-ray diffraction analyses confirmed that pyrite was the only iron-sulfide formed, and that no arsenic-only sulfide phase precipitated (e.g. orpiment or realgar). Pyrite occurs as either 1–10 μm euhedral crystals or similar-sized framboids both of which contain 500–4000 mg/kg arsenic. As a result, dissolved arsenic decreased from its initial concentration of 0.3–0.5 mg/L to below the regulatory clean-up standard for the site of 0.05 mg/L in a matter of weeks. In addition to the potential of this technique to remediate anthropogenic arsenic contamination, it is possible that it can be modified to inexpensively treat individual small drinking-water wells contaminated by natural sources of arsenic in many developing nations. [ABSTRACT FROM AUTHOR]

Arsenic concentrations above 10 μg L −1 were previously found in 89% of ground water sources in six villages of Pakistan. The present study has ascertained the health risks associated with exposure to total arsenic (tAs) and its species in most frequently consumed foods. Inorganic arsenic (iAs) concentrations were found to be 92.5 ± 41.88 μg kg −1 , 79.21 ± 76.42 μg kg −1 , and 116.38 ± 51.38 μg kg −1 for raw rice, cooked rice and wheat respectively. The mean tAs concentrations were 47.47 ± 30.72 μg kg −1 , 71.65 ± 74.7 μg kg −1 , 105 ± 61.47 μg kg −1 . Wheat is therefore demonstrated to be a significant source of arsenic exposure. Dimethylarsinic acid was the main organic species detected in rice, whilst monomethylarsonic acid was only found at trace levels. Total daily intake of iAs exceeded the provisional tolerable daily intake of 2.1 μg kg −1 day −1 body weight in 74% of study participants due to concurrent intake from water (94%), wheat (5%) and raw rice (1%). A significant association between tAs in cooked rice and cooking water resulted in tAs intake 43% higher in cooked rice compared to raw rice. The study suggests that arsenic intake from food, particularly from wheat consumption, holds particular significance where iAs is relatively low in water. Chronic health risks were found to be significantly higher from wheat intake than rice, whilst the risk in terms of acute effects was below the USEPA's limit of 1.0. Children were at significantly higher health risk than adults due to iAs exposure from rice and/or wheat. The dietary exposure of participants to tAs was attributable to staple food intake with ground water iAs <10 μg L −1 , however the preliminary advisory level (200 μg kg −1 ) was achievable with rice consumption of ≤200 g day −1 and compliance with ≤10 μg L −1 iAs in drinking water. Although the daily iAs intake from food was lower than total water intake, the potential health risk from exposure to arsenic and its species still exists and requires exposure control measures. [ABSTRACT FROM AUTHOR]

Abstract: Arsenic in groundwater is a serious problem in New England, particularly for domestic well owners drawing water from bedrock aquifers. The overlying glacial aquifer generally has waters with low arsenic concentrations but is less used because of frequent loss of well water during dry periods and the vulnerability to surface‐sourced bacterial contamination. An alternative, novel design for shallow wells in glacial aquifers is intended to draw water primarily from unconsolidated glacial deposits, while being resistant to drought conditions and surface contamination. Its use could greatly reduce exposure to arsenic through drinking water for domestic use. Hypothetical numerical models were used to investigate the potential hydraulic performance of the new well design in reducing arsenic exposure. The aquifer system was divided into two parts, an upper section representing the glacial sediments and a lower section representing the bedrock. The location of the well, recharge conditions, and hydraulic properties were systematically varied in a series of simulations and the potential for arsenic contamination was quantified by analyzing groundwater flow paths to the well. The greatest risk of arsenic contamination occurred when the hydraulic conductivity of the bedrock aquifer was high, or where there was upward flow from the bedrock aquifer because of the position of the well in the flow system. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Groundwater arsenic contamination has become a serious global concern due to its adverse effects on human health. Arsenic-induced reactive oxygen species trigger oxidative stress inside mitochondria, which initiate a cascade of events including altered mitochondrial (mt) membrane potential, uncoupling of electron transport chain, and mtDNA damage. A case-control study was conducted to examine the association between arsenic exposure and differences in mtDNA methylation and to assess the downstream consequences. We recruited 221 arsenic-exposed individuals, including 106 individuals with skin lesions (WSL) and 115 subjects without any skin lesions (WOSL) from the Murshidabad district, West Bengal, India. The unexposed group included 101 individuals from the arsenic unexposed area in East Midnapore. We analyzed the status of mtDNA methylation in D-loop region and ND6 gene by methylation-specific PCR. Gene expression was studied by quantitative real-time PCR. Significant hypomethylation in both D-loop and ND6 was observed with a consequent increase in their target gene expression and higher mtDNA copy number in arsenic-exposed populations compared to controls. Further mechanistic insights regarding mitochondrial epigenetic alteration in arsenic exposure will be of critical importance for the prevention of adverse health effects. [ABSTRACT FROM AUTHOR]

Groundwater monitoring relies on the acquisition of ‘representative’ groundwater samples, which should reflect the ambient water quality at a given location. However, drilling of a monitoring well for sample acquisition has the potential to perturb groundwater conditions to a point that may prove to be detrimental to the monitoring objective. Following installation of 20 monitoring wells in close geographic proximity in central Florida, opposing concentration trends for As and Mo were observed. In the first year after well installation As and Mo concentrations increased in some wells by a factor of 2, while in others As and Mo concentrations decreased by a factor of up to 100. Given this relatively short period of time, a natural change in groundwater composition of such magnitude is not expected, leaving well installation itself as the likely cause for the observed concentration changes. Hence, initial concentrations were identified as ‘false negatives’ if concentrations increased with time or as ‘false positives’ if concentrations decreased. False negatives were observed if concentrations were already high, i.e., the As or Mo were present at the time of drilling. False positives were observed if concentrations were relatively lower, i.e., As or Mo were present at low concentrations of approximately 1 to 2 μg/L before drilling, but then released from the aquifer matrix as a result of drilling. Generally, As and Mo were present in the aquifer matrix in either pyrite or organic matter, both of which are susceptible to dissolution if redox conditions change due to the addition of oxygen. Thus, introduction of an oxidant into an anoxic aquifer through use of an oxygen saturated drilling fluid served as the conceptual model for the trends where concentrations decreased with time. Mixing between drilling fluid and groundwater (i.e., dilution) was used as the conceptual model for scenarios where increasing trends were observed. Conceptual models were successfully tested through formulation and application of data-driven reactive transport models, using the USGS code MODFLOW in conjunction with the reactive multicomponent transport code PHT3D. [ABSTRACT FROM AUTHOR]

Groundwater contamination with high arsenic (As) levels has caused serious health problem in Jianghan Plain. This study presents a framework to evaluate the results and their probable influencing factors of non-carcinogenic risk and carcinogenic risk in Shahu Village. An appropriate health risk assessment for residents exposing to As through ingestion and dermal contact pathways is also discussed in the paper. Hazard quotient (HQ) and target cancer risk (TR) are adopted to compute the non-carcinogenic and carcinogenic effects for residents, respectively. Monte Carlo simulation technique is used to quantify the uncertainty of the risk assessment. The assessment results show that the HQs and TRs of 10-m-deep and 25-m-deep wells exhibit seasonal variations with higher values in rainy season and lower values in dry season. The HQ values exceeding 1 at the depths of 10 (from 0.09 to 23.21 m) and 25 m (from 0.29 to 130.55 m) account for 61 and 94%, respectively, which associate with the As contents distribution in the aquifer sediments. The estimated TR values at the depths of 10 (from 3.86E−05 to 1.04E−02) and 25 m (from 1.32E−04 to 5.87E−02) exceeding the highest acceptable standard (10−4) account for 95 and 100%, respectively. Comparison of the two exposure pathways, the ingestion exposure contributes much more than the dermal contact exposure for both non-carcinogenic risk and carcinogenic risk. The results of sensitivity analysis indicate that a more accurate measurement and better definition of probability distributions for As concentration in the groundwater can increase the accuracy of health risk assessment in Jianghan Plain. The findings demonstrate the importance of the drinking water safety, and the government should take measures to ensure the drinking water safety. [ABSTRACT FROM AUTHOR]

Exposure to naturally occurring arsenic in groundwater is a public health concern, particularly for households served by unregulated private wells. At present, one of the greatest barriers to exposure reduction is a lack of private well testing due to difficulties in motivating individual private well owners to take protective actions. Policy and regulations requiring testing could make a significant contribution towards universal screening of private well water and arsenic exposure reduction. New Jersey's Private Well Testing Act (PWTA) requires tests for arsenic during real estate transactions; however, the regulations do not require remedial action when maximum contaminant levels (MCLs) are exceeded. A follow-up survey sent to residents of homes where arsenic was measured above the state MCL in PWTA-required tests reveals a range of mitigation behavior among respondents (n = 486), from taking no action to reduce exposure (28%), to reporting both treatment use and appropriate maintenance and monitoring behavior (15%). Although 86% of respondents recall their well was tested during their real estate transaction, only 60% report their test showed an arsenic problem. Treatment systems are used by 63% of households, although half were installed by a previous owner. Among those treating their water (n = 308), 57% report that maintenance is being performed as recommended, although only 31% have tested the treated water within the past year. Perceived susceptibility and perceived barriers are strong predictors of mitigation action. Among those treating for arsenic, perceived severity is associated with recent monitoring, and level of commitment is associated with proper maintenance. Mention of a treatment service agreement is a strong predictor of appropriate monitoring and maintenance behavior, while treatment installed by a previous owner is less likely to be maintained. Though the PWTA requires that wells be tested, this study finds that not all current well owners are aware the test occurred or understood the implications of their arsenic results. Among those that have treatment installed to remove arsenic, poor monitoring and maintenance behaviors threaten to undermine intentions to reduce exposure. Findings suggest that additional effort, resources, and support to ensure home buyers pay attention to, understand, and act on test results at the time they are performed may help improve management of arsenic water problems over the long term and thus the PWTA's public health impact. [ABSTRACT FROM AUTHOR]

High As concentration in groundwater of Datong Basin has emerged as an issue of great concern in the past decade because of its serious impact on the health of many people. The present study is to our knowledge the first attempt model the transport of arsenic in this system using a 1D reactive transport model (PHREEQC). Based on published field data from Shanyin Field Site (Datong Basin), the importance of the (bio)geochemical processes for arsenic mobility is evaluated quantitatively using geochemical models of growing complexity. Arsenic mobility during the surface water and groundwater interactions can be explained by the reductive dissolution of iron oxyhydroxides, sulfate, nitrate and arsenate, and by surface sorption/de-sorption occurring in response to changes in geochemical conditions. Both the Fe(III) surface complexation model and the 1D reactive transport model were employed to depict the arsenic transport in shallow groundwater system during the surface water-groundwater interactions. The surface complexation model results showed that a total of 0.34 mmol and 0.56 mmol arsenic were sorbed onto Fe(III) oxyhydroxides for Well 1-2S and Well 2-2S, respectively, reflecting the important role of surface sorption process on arsenic transport. The 1D model results revealed that redox processes were also critical. The improved calibration of model simulations involving both of these components indicates that the combination of processes is critical to understanding and characterising the transport of arsenic in groundwater during groundwater surface water interaction, especially close to the surface water body. [ABSTRACT FROM AUTHOR]

Arsenic is a widespread contaminant of drinking and groundwaters in the world. Even if these contaminations have a geogenic origin, they often are exacerbated by anthropogenic activities. This is particularly true for the Bengal delta. Millions of people in Bangladesh are consuming drinking water with arsenic concentrations ≥ 50 µg/L. Their drinking water supply is based on groundwaters extracted by pumping wells, which were part of a well-drilling program by the United Nations. The intention was to provide the people with groundwater instead of surface water due to its critical hygienic conditions. Unfortunately, many wells extract the groundwater at depths where arsenic concentrations are highest. Arsenic is being dissolved from the aquifer by biogeochemical processes that are fueled by the presence of high amounts of organics in the Bengal delta sediments. This problem was not encountered at the time due to a lack of chemical analyses of the waters. [ABSTRACT FROM AUTHOR]

In this study, a wave rectified alternating current (RAC) electrocoagulation process was developed for the oxidative sequestration of As(III) via simultaneous generating Fe(II) and O2 in the synthesized anoxic groundwater. The optimal TFe-anode/TMMO-anode:Tpower-off ratio (T is the time-taken in corresponding stage) and reaction period for As(III) sequestration were 1:2:1 and 24 s, respectively. Elevating electric current applied on the alternate iron/MMO anodes (30–50 mA) and solution pH (6.0–9.0) promoted As(III) sequestration, whereas the presence of HCO3– and PO43– deteriorated As(III) sequestration. The intermediate Fe(IV) primarily accounted for the oxidation of As(III) to As(V), which can be readily sequestrated by the freshly generated Fe(III) (oxyhydr)oxides. The energy required for As(III) sequestration in the RAC electrocoagulation process was only 0.11 kW·h m–3, which is much less than those in the traditional DC/AC electrocoagulation processes. Generally, this study offers an energy-efficient strategy to improve access to safe groundwater for millions of people. [ABSTRACT FROM AUTHOR]

High spatial variability of arsenic (As) concentration in geogenic As-contaminated groundwater has been commonly observed worldwide, but the underlying reasons remain not well understood. Selecting a sulfate-containing, As-affected aquifer at the Datong Basin, northern China as the study area and combining hydrogeochemical investigation and sediment extraction with reactive transport modeling, this work elucidated the roles of Fe-S-As interactions in regulating the vertical variation of As concentration in the groundwater. Dissolved As concentration varied between 0.05 and 18 μmol/L, but generally increased in the depth of 20–25 m and then decreased in 25–30 m. The high-As groundwater contained low Fe(II) (<0.007 mmol/L) and up to 15 μmol/L sulfide, in contrary to the S/SE Asian deltas/floodplains where high Fe(II) and As jointly occur in the groundwater devoid of sulfate reduction. The reductive dissolution of As-bearing Fe(III) oxides coupled to the degradation of organic matter with an estimated maximum rate of 0.22 mmol C/L/yr, mainly accounted for the depth-dependent increase of As concentration in the upper part of the shallow aquifer (<25 m deep). However, the decreasing reactivity of Fe(III) oxides together with the increase of pH over depth rendered the majority of electrons being transferred to sulfate reduction. The Fe(II) sulfides formed as a consequence not only helped to restrict the build-up of Fe(II) in the groundwater but also probably co-precipitated As to prompt As decrease in the depth of 25–30 m. Arsenite adsorbed on remaining Fe(III) oxides and newly-formed Fe(II) sulfides is another important pool of As in the aquifer, which varies in response to the extents of Fe(III)-oxide and sulfate reduction and consequently alters As distribution coefficient between the solid and the aqueous phases. This study highlights the importance of coupled geochemical cycling of Fe, S and As for As mobilization and reveals how it regulates As partitioning between groundwater and sediments. [ABSTRACT FROM AUTHOR]

Geochemical investigation was carried out for delineating factors responsible for the mobilization of arsenic (As) from aquifer material into the groundwater. Four sites along Ravi River, ( Samada, Sarai Chimba, Kot Maiga and Chah Fatehwala) , were selected based on the blanket survey. Groundwater-rock interaction and evaporation were the key phenomena controlling groundwater chemistry, as shown by the hydrogeochemical data. Groundwater was predominantly Na-Cl type, with other principle facies being Na-HCO 3 , Na-Ca-HCO 3 and Ca-Mg-Cl. The groundwater As concentration ranged between below detection level (2 μg/L) to 548 μg/L with 59% samples exceeding the World Health Organization (WHO) guidelines for As in drinking water (10 μg/L) and 31% having higher concentrations than the National Environmental Quality Standard (NEQS, 50 μg/L). Moderate to high concentrations of SO 4 −2 averaged at 244 mg/L and moderate NO 3 − concentrations averaged at 8 mg/L, together with alkaline pH (7.3–8.8) and high Eh values (113–402 mV) suggest partial oxidizing nature of the aquifers. The values for δ 18 O and δ 2 H in groundwater varied between −9.14 and −5.51‰, and −56.57 to −39.5‰ respectively, and suggests meteoric origin of the groundwater with some evaporative loss. This effect could be partly responsible for elevated levels of pH and salinity in groundwater. Based on geochemical and isotopic composition of groundwater, desorption of As from metal surfaces under alkaline environment might be the factor causing As enrichment in study area. [ABSTRACT FROM AUTHOR]

In this study, we tested 123 groundwater wells from five different areas of Punjab, Pakistan for arsenic (As) contamination level and species, as well as delineated hydrogeochemical behaviour of As in aquifers. Results revealed that 75% and 41% of the groundwater wells exceeded the safe As limit of World Health Organisation (WHO, 10 μg L −1 ) and Pakistan-EPA (50 μg L −1 ), respectively. Arsenite (As(III)) and arsenate (As(V)) spanned 0–80% and 20–100% of total As (1.2–206 μg L −1 ), respectively. The mean As content (5.2 μg L −1 ) of shallow wells at 9–40 m depth did not exceed the WHO safe limit, representing a safe aquifer zone for pumping of groundwater compared to deeper wells at 41–90 m (51 μg L −1 ) and >90 m (23 μg L −1 ) depths. Piper-plot elucidated that the aqueous chemistry was dominated with Na-SO 4 , Na-Ca-SO 4 , Na-Mg-SO 4 type saline water. Principal component analysis grouped As concentration with well depth, pH, salinity, Fe and CO 3 , exhibiting that these hydrogeochemical factors could have potential role in controlling As release/sequestration into the aquifers of study area. Geochemical modeling showed positive saturation indices only for iron (Fe) oxide-phases, indicating Fe oxides as the major carriers of As. Overall, this study provides insights to tackle emerging As threat to the communities in Punjab, Pakistan, as well as help develop suitable management/mitigation strategies – based on the baseline knowledge of As levels/species and factors governing As contamination in the study area. [ABSTRACT FROM AUTHOR]

Arsenic (As)-contaminated groundwater is a global concern with potential detrimental effects on the health of hundreds of millions of people worldwide. However, the extent of this problem may be more severe than anticipated, as many wells have not been tested and may contain unsafe-level of As. An optimized statistical regression model was developed to predict the probability of geogenic high As groundwater (As > 10 μg/L) in this study. Easily obtained hydrogeochemical and geological parameters that are significantly related to As geochemical behaviors were selected as explanatory variables in the model. The results indicate that pH, Cl − , HCO 3 − , SO 4 2− , and NO 3 − concentrations, stratigraphic information, and well depth are excellent predictors of As exposure in the Datong Basin, China. Predicted unsafe wells correspond well with the known distribution of high As groundwater in the Datong Basin. The successful application of a data set from Bangladesh also demonstrated the applicability and credibility of this proposed method. [ABSTRACT FROM AUTHOR]

Regularmonitoring of arsenic (As) in groundwater is crucial frompublic health perspectives as millions of people are suffering due to use of contaminated aquifer water for drinking purposes. The routine analyses, especially in developing nations, are mostly done in localised government/non-government laboratories with limited resources, having the target of analysing large number of samples in each run. Thus apart from analytical sensitivity, cost-effectiveness of the method and eco-friendliness of the experimental operation are key surreptitious factors. This demands optimisation of total As measurement methods and finding a method that gives 'optimumbenefit' considering all these factors together. The present study therefore evaluates four common As (total) measurement methods [iodometric-colorimetric method, silver diethyl dithiocarbamate method, molybdenum blue method and hydride generation atomic absorption spectrophotometric (HG-AAS) method] practised in the Bengal Delta Plain, in view of their analytical sensitivity, related environmental hazard and experimental costs. It was found that the HG-AAS method is analytically more sensitive, whereas the iodometric-colorimetricmethod and the molybdenum blue method are better choices in terms of eco-friendliness and cost-effectiveness, respectively. However, when all three factors (analytical reliability, environmental hazard and cost) are considered simultaneously, themolybdenumbluemethodwas found to be placed first in the 'optimum performance rank' list. It was also found that both environmental hazard and cost play a more crucial role than analytical reliability, although this is case specific andwould differ from place to place around the globe. Finally based on the results, we have hypothesised a water testing strategy for developing countries such as India where the molybdenum blue method can be adapted as a screening method and later the HG-AASmethod can be used to precisely identify the groundwater samples with As concentration below the WHO drinking water guideline value of 10 μg/L. [ABSTRACT FROM AUTHOR]

Drinking water contaminated with arsenic poses serious threat to the human health. The present study was aimed for quality assessment of the groundwater of Khairpur Mir's in respect with arsenic and other elemental contamination like Fe, Cu, Co, and Ni. The presence of the trace elements in groundwater from different sources in the study area was measured by using atomic absorption spectroscopy. For arsenic analysis hydride generation technique (MHS-15) was used with detection limit of 0.02 µg l−1. Elevated level of arsenic was observed in most of the samples as compared to recommended value of World Health Organization (WHO) guidelines (10 µg l−1). However, levels of Fe, Cu, Co, and Ni in hand pump (HP) water samples was found in the range of 4-1610 µg l−1, 0-556 µg l−1, 0-230 µg l−1, and 0-700 µg l−1, respectively. Whereas in tube well (TW) water samples the observed values are 5-1620 µg l−1, 0-50 µg l−1, 4-110 µg l−1, and 0-360 µg l−1 for Fe, Cu, Co, and Ni, respectively. Significant difference was observed between TW and HP water samples. It was concluded that the level of arsenic found was very high up to 13 fold more than the WHO recommended limit in study area. While the levels of other elements was noted within the safe limit. [ABSTRACT FROM AUTHOR]

Abstract: Groundwater beneath the alluvial plain of the Indus River, Pakistan, is reported to be widely polluted by arsenic (As) and to adversely affect human health. In 79 groundwaters reported here from the lower Indus River plain in southern Sindh Province, concentrations of As exceeded the WHO guideline value for drinking water of 10 μg/L in 38%, with 22% exceeding 50 μg/L, Pakistan's guideline value. The As pollution is caused by microbially‐mediated reductive dissolution of sedimentary iron oxyhydroxides in anoxic groundwaters; oxic groundwaters contain <10 μg/L of As. In the upper Indus River plain, in Punjab Province, localized As pollution of groundwater occurs by alkali desorption as a consequence of ion exchange in groundwater, possibly supplemented by the use for irrigation of groundwater that has suffered ion exchange in the aquifer and so has values >0 for residual sodium carbonate. In the field area in southern Sindh, concentrations of Mn in groundwater exceed 0.4 mg/L in 11% of groundwaters, with a maximum of 0.7 mg/L, as a result of reduction of sedimentary manganese oxides. Other trace elements pose little or no threat to human health. Salinities in groundwaters range from fresh to saline (electrical conductivity up to 6 mS/cm). High salinities result from local inputs of waste water from unsewered sanitation but mainly from evaporation/evapotranspiration of canal water and groundwater used for irrigation. The process does not concentrate As in the groundwater owing to sorption of As to soils. Ion exchange exerts a control on concentrations of Na, Ca, and B but not directly on As. High values of Cl/Br mass ratios (most ≫288, the marine value) reflect the pervasive influence on groundwater of sewage‐contaminated water from irrigation canals through seepage loss and deep percolation of irrigation water, with additional, well‐specific, contributions from unsewered sanitation. [ABSTRACT FROM AUTHOR]

Water from La Pampa, Argentina, was used for washing and cooking rice to examine the in-situ impact of using naturally-contaminated water for food preparation on the elemental dietary intake. Whilst washing with the control tap water (28 μg/L As) reduced the concentration of As in rice by 23%, the use of different well waters (281–1144 μg/L) increased As levels significantly (48–227%) in comparison with the original concentration in the rice (0.056 µg/g). Cooking the rice at a low water-to-rice ratio (2:1) using modern methods increased the levels of As in the cooked samples by 2–3 orders of magnitude for both pre-washed and un-washed rice. Similar trends were observed for vanadium. Although the levels of manganese, iron, copper, zinc and molybdenum in rice were reduced during washing and cooking for most water samples, the molybdenum concentration in the cooked rice doubled (2.2–2.9 µg/g) when using water containing >1 mg/L Mo. [ABSTRACT FROM AUTHOR]

In this study, we examined the sorption of arsenite (As(III)) and arsenate (As(V)) to Japanese oak wood-derived biochar (OW-BC) in aqueous solutions, and determined its efficiency to remove As from As-contaminated well water. Results revealed that, among the four sorption isotherm models, Langmuir model showed the best fit to describe As(III) and As(V) sorption on OW-BC, with slightly greater sorption affinity for As(V) compared to As(III) ( Q L = 3.89 and 3.16 mg g − 1 ; R 2 = 0.91 and 0.85, respectively). Sorption edge experiments indicated that the maximum As removal was 81% and 84% for As(III)- and As(V)-OW-BC systems at pH 7 and 6, respectively, which decreased above these pH values (76–69% and 80–58%). Surface functional groups, notably OH, COOH, C O, CH 3 , were involved in As sequestration by OW-BC, suggesting the surface complexation/precipitation and/or electrostatic interaction of As on OW-BC surface. Arsenic K-edge X-ray absorption near edge structure (XANES) spectroscopy indicated that 36% of the added As(III) was partially oxidized to As(V) in the As(III) sorption experiment, and in As(V) sorption experiment, 48% of As(V) was, albeit incompletely, reduced to As(III) on OW-BC surface. Application of OW-BC to As-contaminated well water (As: 27–144 μg L − 1 ; n = 10) displayed that 92 to 100% of As was depleted despite in the presence of co-occurring competing anions (e.g., SO 4 2 − , CO 3 2 − , PO 4 3 − ). This study shows that OW-BC has a great potential to remove As from solution and drinking (well) water. Overall, the combination of macroscopic sorption data and integrated spectroscopic and microscopic techniques highlight that the fate of As on biochar involves complex redox transformation and association with surface functional moieties in aquatic systems, thereby providing crucial information required for implication of biochar in environmental remediation programs. [ABSTRACT FROM AUTHOR]