Arsenic contamination of groundwater:A global synopsis with focus on the Indian Peninsula

More than 2.5 billion people on the globe rely on groundwater for drinking and providing high-quality drinking water has become one of the major challenges of human society.Although groundwater is considered as safe,high concentrations of heavy metals like arsenic(As)can pose potential human health concerns and hazards.In this paper,we present an overview of the current scenario of arsenic contamination of groundwater in various countries across the globe with an emphasis on the Indian Peninsula.With several newly affected regions reported during the last decade,a significant increase has been observed in the global scenario of arsenic contamination.It is estimated that nearly 108 countries are affected by arsenic contamination in groundwater with concentration beyond maximum permissible limit of 10 ppb recommended by the World Health Organization.The highest among these are from Asia(32)and Europe(31),followed by regions like Africa(20),North America(11),South America(9)and Australia(4).More than 230 million people worldwide,which include 180 million from Asia,are at risk of arsenic poisoning.Southeast Asian countries,Bangladesh,India,Pakistan,China,Nepal,Vietnam,Burma,Thailand and Cambodia,are the most affected.In India,20 states and 4 Union Territories have so far been affected by arsenic contamination in groundwater.An attempt to evaluate the correlation between arsenic poisoning and aquifer type shows that the groundwater extracted from unconsolidated sedimentary aquifers,particularly those which are located within the younger orogenic belts of the world,are the worst affected.More than 90%of arsenic pollution is inferred to be geogenic.We infer that alluvial sediments are the major source for arsenic contamination in groundwater and we postulate a strong relation with plate tectonic processes,mountain building,erosion and sedimentation.Prolonged consumption of arsenic-contaminated groundwater results in severe health issues like skin,lung,kidney and bladder cancer;coronary heart disease;bronchiectasis;hyperkeratosis and arsenicosis.Since the major source of arsenic in groundwater is of geogenic origin,the extend of pollution is complexly linked with aquifer geometry and aquifer properties of a region.Therefore,remedial measures are to be designed based on the source mineral,climatological and hydrogeological scenario of the affected region.The corrective measures available include removing arsenic from groundwater using filters,exploring deeper or alternative aquifers,treatment of the aquifer itself,dilution method by artificial recharge to groundwater,conjunctive use,and installation of nano-filter,among other procedures.The vast majority of people affected by arsenic contamination in the Asian countries are the poor who live in rural areas and are not aware of the arsenic poisoning and treatment protocols.Therefore,creating awareness and providing proper medical care to these people remain as a great challenge.Very few policy actions have been taken at international level over the past decade to reduce arsenic contamination in drinking water,with the goal of preventing toxic impacts on human health.We recommend that that United Nations Environment Programme(UNEP)and WHO should take stock of the global arsenic poisoning situation and launch a global drive to create awareness among people/medical professionals/health workers/administrators on this global concern.

Groundwater Quality and Arsenic Contamination in Amphoe Khemmarat, Ubon Ratchathani, Thailand

Arsenic （As） is one of the most important elemental pollutants in groundwater and drinking water because it causes health problem of arsenicosis after consumption of drinking arsenic-rich water more than 5-10 years. Arsenic contamination of groundwater is an emerging issue in Mekong Basin including Cambodia, Vietnam, and Thailand. In Thailand, information about arsenic contamination in drinking water resources are quite rare due to that arsenic is not the main element in water qualification assay. The objective of this study is to determine groundwater quality and arsenic contamination in rural Mekong Basin, Ubon Ratchathani. Groundwater samples were collected from 20 different sampling points, between August 2009 and February 2010 in Amphoe Khemmarat, Ubon Ratchathani, Thailand. Physical and chemical characteristics of groundwater were determined. It was observed that the groundwater was 27.9-30.3 ~C, pH 5.7-6.9. The conductivity was 707-767 p.S.cm＂. Dissolved oxygen was 2.04-5.12 mg.L-1 and TDS was 352-384 mg.L~. The samples showed soft- to very hardness-water properties. In some area, few parameters like CI, Fe, Mn, and As exceeded the WHO guideline limits. This result represents basic information for quality of groundwater and the arsenic contamination in rural Mekong Basin, Ubon Ratchathani. Thus, it is probably useful for arsenic standard level assignment and public health authorities. Moreover, it also leads to establish research activity in treatment of arsenic-contaminated groundwater for different purposes

Characterization of acylated homoserine lactone derivatives and their influence on biofilms of Acidithiobacillus ferrooxidans BY-3 under arsenic stress

Quorum sensing is one kind of cell-to-cell signalling system among microorganisms that works in response to their population density via autoinducers exemplified by AHL and oligopeptides. In this study, fourteen AHL derivatives were synthesised by a chemical synthesis method, and two types of AHL derivatives were measured and screened by crystal violet staining assay, which have more obvious inhibitory effects on A. ferrooxidans biofilms under arsenic environment. Their structures were verified through IR and NMR identification. The morphological changes of A. ferrooxidans under the influence of the AHL derivatives were compared. In addition, the effects of AHL derivatives(0.1 μg/mL and 1 μg/mL) on membrane formation of A. ferrooxidans under high concentration of arsenic resistance(1,600 mg/L) were explored. Solid experimental data firstly showed that a portion of logarithmic microorganisms were ruptured under the effect of high arsenic concentration. Secondly, the volume of the cell shrank and the number of extracellular polymeric substances decreased after the addition of the AHL derivatives at high concentrations. Therefore, we found here that two derivatives used at concentrations of 0.1 μg/mL and 1 μg/m L accompanied with high concentration of arsenic can both effectively restrict biofilms formation by A. ferrooxidans.

Factors Influencing on Drinking Water Source Selection in Rural Areas of the Bengal Region

The arsenic contamination of underground water is a serious problem in rural areas of the Bengal region, where the water pipeline supply is not equipped. Those, who suffer from the contamination are mainly in the poorest sector. In the region, the selection of drinking water sources is done by women. The local traditional custom of Parda may restrict women＇s behavior. In this paper, a quantitative way of evaluating women＇s psychological stress is proposed, and mechanisms of women＇s water selection are analyzed using behavioral model. Ultimately, the more acceptable ways of installing water facilities to local people in each village are discussed.

Biochar potentially enhances maize tolerance to arsenic toxicity by improving physiological and biochemical responses to excessive arsenate

Metalloid pollution,including arsenic poisoning,is a serious environmental issue,plaguing plant productivity and quality of life worldwide.Biochar,a carbon-rich material,has been known to alleviate the negative effects of environmental pollutants on plants.However,the specific role of biochar in mitigating arsenic stress in maize remains relatively unexplored.Here,we elucidated the functions of biochar in improving maize growth under the elevated level of sodium arsenate(Na_(2)AsO_(4),AsV).Maize plants were grown in pot-soils amended with two doses of biochar(2.5%(B1)and 5.0%(B2)biochar Kg^(−1) of soil)for 5 days,followed by exposure to Na_(2)AsO_(4)(’B1+AsV’and’B2+AsV’)for 9 days.Maize plants exposed to AsV only accumulated substantial amount of arsenic in both roots and leaves,triggering severe phytotoxic effects,including stunted growth,leaf-yellowing,chlorosis,reduced photosynthesis,and nutritional imbalance,when compared with control plants.Contrariwise,biochar addition improved the phenotype and growth of AsV-stressed maize plants by reducing root-to-leaf AsV translocation(by 46.56 and 57.46%in‘B1+AsV’and‘B2+AsV’plants),improving gas-exchange attributes,and elevating chlorophylls and mineral levels beyond AsV-stressed plants.Biochar pretreatment also substantially counteracted AsV-induced oxidative stress by lowering reactive oxygen species accumulation,lipoxygenase activity,malondialdehyde level,and electrolyte leakage.Less oxidative stress in‘B1+AsV’and‘B2+AsV’plants likely supported by a strong antioxidant system powered by biochar-mediated increased activities of superoxide dismutase(by 25.12 and 46.55%),catalase(51.78 and 82.82%),and glutathione S-transferase(61.48 and 153.83%),and improved flavonoid levels(41.48 and 75.37%,respectively).Furthermore,increased levels of soluble sugars and free amino acids also correlated with improved leaf relative water content,suggesting a better osmotic acclimatization mechanism in biochar-pretreated AsV-exposed plants.Overall,our findings provided mechanistic insight into how biochar facilitates maize’s active recovery from AsV-stress,implying that biochar application may be a viable technique for mitigating negative effects of arsenic in maize,and perhaps,in other important cereal crops.

Arsenic fractionation and contamination assessment in sediments of thirteen lakes from the East Plain and Yungui Plateau Ecoregions, China

Arsenic（As） fractions in the sediments of seven lakes from East Plain Ecoregion and six lakes from Yungui Plateau Ecoregion, China, were investigated. Results indicated that the total As concentrations in sediment samples of lakes of the East Plain Lake Ecoregion are higher than those of Yungui Plateau Lake Ecoregion. Residual As is the main fraction in sediment samples of lakes from both ecoregions, followed by reducible As and soluble or oxidizable As. The total As is correlated to oxidizable As and residual As in sediment samples from both lake ecoregions. As distribution in sediment samples of lakes of the East Plain Ecoregion appears to be affected by human activity, while the As origin mainly comes from natural sources in sediment samples of lakes in the Yungui Plateau Ecoregion. The potential ecological risk index and geoaccumulation index values suggest ＂low to moderate＂ risk degree and ＂unpolluted to moderately polluted＂ for As in the studied lake sediments.

Rice:Reducing arsenic content by controlling water irrigation

Arsenic has long been recognized as a poison.Arsenic in water supplies that are used for both drinking and crop irrigation can expose many people chronically to elevated levels of arsenic.

Rhizophagus irregularis influences As and P uptake by alfafa and the neighboring non-host pepperweed growing in an As-contaminated soil

It was documented that arbuscular mycorrhiza fungi（AMF） play an important role in protecting host plants against arsenic（As） contamination. However, most terrestrial ecosystems contain a considerable number of nonmycorrhizal plants. So far little information is available for the interaction of such non-host plants with AMF under As contaminations. By using a dual compartment cultivation system with a plastic board or a nylon mesh separating roots of non-host pepperweed from roots of the AM-host alfafa plants, avoiding direct root competition, the two plant species were grown separately or partially separated（with rhizosphere effects） in the presence or absence of the AMF Rhizophagus irregularis in As-contaminated soil. The results indicated that mycorrhiza caused phosphorus（P） concentration decrease in the non-host pepperweed, but promoted the P concentration of the AM host alfafa. Mycorrhiza is potentially helpful for non-host pepperweed to adapt to As contamination by decreasing root As concentration and showing no suppressing effect on biomass production. The study provides further evidence for the protective effects of AMF on non-host plants against As contamination, and improved our understanding of the potential role of AMF for non-host plant adaptation to As contaminated soils.

Determining the influence of the physicochemical parameters of urban soils on As availability using chemometric methods：A preliminary study

An initial exploration was conducted using mathematical and statistical methods to obtain relevant information about the determination of the physicochemical parameters capable of controlling As uptake by ryegrass grown on contaminated topsoils.Concentrations of As in the soils were from 10 to 47 mg/kg,mainly in the As（V） form（57%–73%）.Concentrations of As in water extracts were very low（61–700 μg/kg）.It was suggested that As（Ⅲ） was mainly in the uncharged species and As（V） in the charged species.Chemometric methods revealed that the values of the ratio As（Ⅲ）/As（V） depended on the assimilated-phosphorus,the pseudo-total and water-extractable Fe contents and the soil p H.Arsenic concentrations measured in ryegrass shoots ranged from 119 to 1602 μg/kg.Positive linear correlations were obtained between As in ryegrass shoots and water extractable-As.The transfer coefficient of As correlated well with the ratio assimilated-phosphorus/Fe-oxides.As（Ⅲ）uptake by the shoot of ryegrass was controlled by the organic matter and Fe-oxide contents.