Arsenic Concentrations in Groundwater, Soils, and Irrigated Rice in Southwestern Bangladesh

Abstract

Arsenic (As) poisoning of groundwater in Bangladesh has become a major environmental and health issue. The extensive use of groundwater in irrigation of rice has resulted in elevated As in soils and crops. A study was undertaken to determine As concentrations in groundwater, soils, and crops in 16 districts of southwestern Bangladesh. Groundwater samples were collected from shallow-tube and hand-tube wells (STW and HTW) used for irrigation and drinking water. Soil and rice plants were sampled from the command area of the tube wells. Arsenic concentrations were determined using an atomic absorption spectrometer equipped with flow injection hydride generator. Groundwater samples contained <10 to 552 μg As L−1. Arsenic concentrations in 59% of STW samples exceeded 50 μg As L−1, the national standard for As in drinking water. Unlike groundwater, most of the surface water samples contained <10 μg As L−1. Concentrations of As in the soils from the command area of the tube wells ranged from 4.5 to 68 mg kg−1. More than 85% of the soils contained <20 mg As kg−1. The mean As concentration in the rice grain samples was 0.23 mg kg−1, which is much less than the maximum food hygiene standard. A positive relationship was observed between groundwater and soil As, implying that soil As level increases as a result of irrigation with contaminated water. However, irrigation water As did not show any relation with rice grain As. The findings suggest that surface water bodies are a safe source of irrigation water in the As-contaminated areas.