Speciation of arsenic in groundwater, sediment and plant leaves in North-western Bangladesh: Implications for arsenic mobilization

Arsenic (As) contamination in groundwater of Chapai-Nawabganj district, Bangladesh is of increasing environmental concern to the local community. In this study, the current As contamination status in groundwater, sediment, and plant leaves was investigated. High-performance liquid chromatography (HPLC) coupled with inductively coupled plasma mass spectrometry (ICP–MS) and hydride generation atomic fluorescence spectrometry (HG-AFS) was applied to the speciation of As in groundwater, sediment and plant leaves samples collected from As contaminated area, Chapai-Nawabganj, Bangladesh. Elevated levels of As in the groundwater of up to 1492 µg/L and high concentrations of arsenite As (III) (1009 µg/L) were detected in groundwater. Speciation of As in groundwater samples (n = 20) showed the presence of inorganic As only; arsenite (As(III)) contained 55%–100% of total As and arsenate (As(V)) ranged from 0% to 45%. The relationship between δD and δ¹⁸O of the groundwater samples indicates that the groundwater originate from meteoric water. A sediment profile of As from the study area showed higher As concentrations at depth of 65 ft compared with data from deeper and shallower depth of the same core at Chougachi. An extraction procedure revealed that As could be found in all four phases (weak acid soluble, reducible, oxizable and aqua regia soluble As). The bioavailable As in the sediment was in the range of 25 to 7448 µg/kg. There was a significant correlation between As in groundwater and As in plants. The buildup of As in plants was directly related to the As concentration of tube well waters. Accumulation of As was observed in plant leaves collected from plants in this area. Arsenic concentrations in plant leaves samples ranged from 96 to 589 µg/L. Only a small part of the As (25%) in the plant leaves was extractable with ethanol-water (1:3), and most of this As (95%) was inorganic As (arsenite 5–80 µg/L and arsenate 10 –69 µg/L). Organic As compound like dimethylarsenic acid was detected at trace levels in plant leaves.