Arsenic Contamination in Groundwater of Bangladesh: Perspectives on Geochemical, Microbial and Anthropogenic Issues

Abstract

A groundwater, sediment and soil chemistry and mineralogical study has been performed to investigate the sources and mobilization process of Arsenic (As) in shallow aquifers of Bangladesh. The groundwater from the shallow aquifers is characterized by high concentrations of Arsenic (47.5-216.8 µg/L), iron (0.85-5.83 mg/L), and phosphate, along with high electrical conductivity (EC). The groundwater has both very low oxidation-reduction potential (Eh) and dissolved oxygen (DO) values indicating reducing conditions. By contrast, the deep aquifers and surface waters (pond, canal) have very low concentrations of Arsenic (<6 µg/L), iron (0.12-0.39 mg/L), and phosphate along with a relatively low EC. Furthermore, the values of Eh and DO are high, indicating oxic to suboxic conditions. Arsenic is inversely correlated with Eh values in the upper aquifer, whereas no relationship in the deeper aquifer is observed. These results suggest that As mobilization is clearly linked to the development of reducing conditions. The clayey silt, OPEN ACCESSWater 2011, 3 1051 enriched in Fe, Mn, Al oxides and organic matter, and deposited in the middle unit of shallow aquifers, contains moderately high concentrations of As, whereas the sediments of deep aquifers and silty mud surface soils from paddy fields and ponds contain a low content of As (Daudkandi area). Arsenic is strongly correlated with the concentrations of Fe, Mn and Al oxides in the core samples from the Daudkandi and Marua areas. Arsenic is present in the oxide phase of Fe and Mn, phyllosilicate minerals and in organic matter in sediments. This study suggests that adsorption or precipitation of As-rich Fe oxyhydroxide on the surface or inner sites of biotite might be responsible for As concentrations found in altered biotite minerals by Seddique et al. Microbially or geochemically mediated reductive dissolution of Fe oxyhydroxides is the main mechanism for As release. The reducing conditions are caused by respiratory decomposition of organic matter, either sedimentary or labile organic C. The process can be accelerated by agricultural activity and domestic organic wastes. An agricultural fertilizer can directly contribute As to groundwater as well as promote As mobilization by ion-exchange with phosphorus.

Arsenic Adsorption onto Minerals: Connecting Experimental Observations with Density Functional Theory Calculations

“…In addition to iAs, methylated As ) occur both naturally and due to anthropogenic sources [12,13]. Arsenic toxicity depends on the species present; a general trend of decreasing toxicity is: R 3 As > H 3 AsO 3 > H 3 AsO 4 > R 4 As + > As 0 , where R is an alkyl group or a proton [12,16].…”

“…Arsenic is found in a variety of geochemical environments at aqueous concentrations varying from <0.5 to >5000 μg/L, and is found in a variety of geochemical environments [1,2]. Natural and anthropogenically-mediated biogeochemical interactions among arsenic species, biota, and minerals can affect the distribution, mobility, and toxicity of As in the environment [2][3][4][5][6][7][8]. Although recent work has posited that arsenic could be a potential biochemical and astrobiological proxy for phosphorus during biological evolution [9], this hypothesis is controversial [10].…”

“…Groundwater that contains As concentrations >10 μg/L limit set by the World Health Organization (WHO) places more than ten million people at risk from arsenicosis. Locales ranging from Southern Bangladesh, India, Argentina, Chile, and Vietnam have groundwater sources with As concentrations >10 μg/L [2,3,6,25,26,[28][29][30][31][32][33].…”

Vertical distribution of bacterial communities in high arsenic sediments of Hetao Plain, Inner Mongolia

“…Arsenic (As) as a toxic metalloid element and also a serious carcinogen has been observed from aquifers of many parts of the world including Bangladesh, India, Vietnam, China, USA, Chile, Japan and Argentina (Guo et al 2008;Chauhan et al 2009;Anawar et al 2011;Ferreccio and Sancha 2011). Long term ingestion of As can result in serious disease, such as skin and bladder cancer, cardiovascular and heart diseases, as well as respiratory problems (Brammer and Ravenscroft 2009;Khan et al 2009;Winkel et al 2011).…”

Reactive Transport Modeling for Mobilization of Arsenic in a Sediment Downgradient from an Iron Permeable Reactive Barrier

“…Arsenic contamination of groundwater water is identified in many countries, such as Bangladesh [5,6], China [7], and Nepal [8]. Acute and chronic effects from arsenic exposure include several cancers (e.g., skin, lung, liver, bladder, etc.…”