Geochemistry of tungsten and arsenic in aquifer systems: A comparative study of groundwaters from West Bengal, India, and Nevada, USA
Authors: Mohajerin, TJ; Neal, AW; Telfeyan, K; Sasihharan, SM; Ford, S; Yang, N; Chevis, DA; Grimm, DA; Datta, S; White, CD; Johannesson, KH
Water, Air, and Soil Pollution 225.
HERO ID: 2278459
Tungsten (W) concentrations were measured along with arsenic (As) in groundwaters from the Murshidabad . . .
Tungsten (W) concentrations were measured along with arsenic (As) in groundwaters from the Murshidabad district of West Bengal, India. Tungsten concentrations range from 0.8 to similar to 8 nmol kg(-1) (0.15-1.5 mu g kg(-1)) in the circumneutral pH (average pH similar to 7.3) Murshidabad groundwaters, and attain concentrations as high as 14 nmol kg(-1) (2.5 mu g kg(-1)) in local ponds (n=2). Total dissolved As concentrations (As-T) range from 0.013 to 53.9 mu mol kg(-1) (<1 to 4,032 mu g kg(-1)), and As(III) predominates in Murshidabad groundwaters accounting for 70 %, on average, of As in solution. Tungsten concentrations in Murshidabad groundwaters are low compared to alkaline groundwaters (pH>8) from the Carson Desert in Western Nevada, USA, where W concentrations are reported to reach as high as 4,036 nmol kg(-1) (742 mu g kg-1). Although W is positively correlated with As in groundwaters from the Carson Desert, it is not correlated with As-T or As(III) in Murshidabad groundwaters, but does exhibit a weak relationship with As(V) in these groundwaters. Surface complexation modeling indicates that pH related adsorption/desorption can explain the geochemical behavior of W in Murshidabad groundwaters. However, the model does not predict the high As concentrations observed in Murshidabad groundwaters. The high As and low W concentrations measured in Murshidabad groundwaters indicate that either As and W originate from different sources or are mobilized by different biogeochemical processes within the Murshidabad aquifers. Mobilization of As in Murshidabad groundwaters is presumed to reflect reductive dissolution of Fe(III) oxides/oxyhydroxides and release of sorbed and/or coprecipitated As to the groundwaters. Multivariate statistical analysis of groundwater composition data indicate that W is associated with Mn and Cl-, which may point to a Mn oxide/oxyhydroxide, clay mineral, and/or apatite source for Win the Murshidabad sediments.