Arsenic in freshwater ecosystems of the Bengal delta: status, sources and seasonal variability

Abstract

The study aimed to examine the contamination status of arsenic (As) in excavated small water bodies, commonly known as ponds – the integral part of daily life in the arsenic-affected rural areas of West Bengal, India in comparison to the unaffected areas. The ponds of the contaminated area had higher levels of As: water 2–174 µg L−1 (mean 31 ± 2 µg L−1) and sediment 1.3–37.3 mg kg−1 (mean 10.3 ± 0.4 mg kg−1), than those from the unaffected area: water 1–8 µg L−1 (mean 4 ± 0 µg L−1) and sediment 1.4–5.3 mg kg−1 (mean 3.0 ± 0.1 mg kg−1). A moderate positive correlation was observed between the water and sediment arsenic content of the ponds of the arsenic-affected region (r = 0.688, n = 277, p < 0.0001). Contaminated ground water, either as direct input or through agricultural washings, was found to be the major contributor of arsenic pollution to these ecosystems. Seasonal variations were not prominent. This study emphasized the beneficial role of using the studied ecosystems over the highly contaminated ground water for various livelihood activities in the Gangetic delta region.