Geochemical study of arsenic release mechanisms in the Bengal Basin groundwater

Abstract

[1] To investigate arsenic mobility in the Bengal Basin groundwater, we sampled water wells and sediments throughout the region. There are strong correlations among high levels of dissolved arsenic and iron, ammonia, and methane, especially in samples from a single site (Laxmipur). No linkage is seen between As and agricultural tracers such as phosphate. The association of As and Fe occurs because arsenic strongly adsorbs onto FeOOH particles in river water. They flocculate with other fine-grained particles at the freshwater/saltwater transition zone. Subsequent bacterially mediated reduction of FeOOH in the clay releases the adsorbed arsenic. Weathering of As-bearing mica plays a significant role in the As budget. The ''correlated'' presence of As, CH 4 , and NH 4 in water supply wells is the result of diffusion out of organic-rich clay into the more permeable zones. Arsenic is mainly released from recent sediments at <50 m depth deposited in the GBR floodplain as sea level rose throughout the Holocene.

Leaching behavior of arsenic from various rocks by controlling geochemical conditions

“…On the other hand, the As concentration in the leachate did not correlate well with the Fe concentration in the leachate of sedimentary rock samples, since the Fe concentration was nearly at the detection limit. The correlation between the As concentration and Fe concentration has been reported by many researchers (Ahmed et al, 2003;Dowling et al, 2002;Kim et al, 2000;Nickson et al, 2000; Shreiber et al, 2000).The relationship between the solid-phase and liquid-phase concentrations was examined based on the chemistry of the leachate and the chemical composition of the rock samples. The As concentration in leachate versus the As content of rock is presented in Fig.…”

“…There are also reports of As pollution of groundwater, sediments, soils, and/or rocks in Japan (Shimada, 1996;Masuda et al, 1999). The origin of the As has been reported to be As-containing minerals in sediments (Akai et al, 2004;Dowling et al, 2002;Kim et al, 2000;Peters et al, 1999;Shimada, 1996). There has been exhaustive research into the behavior of As leaching and migration in subsurface environments (Livesey and Huang, 1981; Manning and Goldberg, 1997;Nickson et al, 2000;Yoshimura and Akai, 2003) and to remediate polluted groundwater (Welch and Stollenwerk, 2003).…”

“…The extensive As pollution of groundwater as in the cases of Bangladesh (Acharyya et al, 2000; Ahmed et al, 2003;Akai et al, 2004;Anawar et al, 2003;Nickson et al,1998;Nickson et al, 2000; Stollenwerk, 2003), West Bengal (Acharyya et al, 2000;Das et al, 1996;Dowling et al, 2002;Nickson et al, 2000), and other locations (Chen et al, 1994;Kim et al, 2000; Kelley et al, 2005;Nimick, 1998;Peters et al, 1999;Robertson, 1989;Schreiber et al, 2000;Smedley and Kinniburgh, 2002;Yoshimura and Akai, 2003;Welch et al, 1988;Welch and Stollenwerk, 2003;Williams et al, 2005) is a well known concern worldwide. There are also reports of As pollution of groundwater, sediments, soils, and/or rocks in Japan (Shimada, 1996;Masuda et al, 1999).…”

The roles of pyrite and calcite in the mobilization of arsenic and lead from hydrothermally altered rocks excavated in Hokkaido, Japan

“…Arsenic-contaminated groundwater used for drinking and cooking is the cause of health problems such as keratosis and cancers reported in Bangladesh and the West Bengal area of India (Acharyya et al, 2000;Akai et al, 2004;Burgess et al, 2010;Das et al, 1996;Dowling et al, 2002;Nickson et al, 2000). Although the source of contamination is believed to be natural, cases elsewhere such as those reported in Thailand, Ghana and some areas of the United States were due to the improper disposal of contaminated soil or rock from mining activities (Bowell, 1993;Choprapawon and Rodcline, 1997;Welch et al, 1999;Williams, 1997).…”

Mobilization and speciation of arsenic from hydrothermally altered rock containing calcite and pyrite under anoxic conditions

“…Arsenic (As) contamination of soil and groundwater from natural or anthropogenic sources is a serious problem encountered in many countries around the world that is affecting millions of people (Acharyya et al 2000;Akai et al, 2004;Das et al, 1996;Dowling et al, 2002;Nickson et al, 2000). Arsenic is a toxic trace element that is ubiquitous in nature, and is usually concentrated in mineral sulfide ore bodies (Fleet et al, 1989;Huston et al, 1995;Smedley and Kinniburgh, 2002).…”