39-Distribution of Arsenic in Groundwater of Tamil Nadu and Pondicherry

Abstract

Chemical analysis of 405 water samples collected from selected dug wells, bore/tube wells and Noyyil river in Tamil Nadu and Pondicherry revealed that the level of arsenic in the formation water is much below the permissible limit (50 µg/L). The concentration of arsenic varied from 0.002 to 24.589 1.1g/L in phreatic aquifers, whereas in semi-confined/confined aquifers, it ranged from 1.25 to 20.15 p.g/L. The pH of the water samples varied from 5.30 to 8.66. It was observed that low concentrations of arsenic in ground water is independent of pH (r2 = 0.0389). The presence of arsenic is more in phreatic aquifer when compared to semiconfined/confined aquifer in urban/industrial areas, which may be due to urbanisation and industrialization. Comparatively higher levels, though within the permissible limits were observed in the samples collected from bore/tube wells tapping sedimentary aquifers in Mettupalayam industrial area of Pondicherry, which may be due to the leaching of dyes used in the industry for colouring of paper. Appreciable amount of arsenic is observed in ground water in the vicinity of a few drainage channels as well, possibly due to agricultural/unplanned urban and industrial activities. Thus it is opined that uncontrolled anthropogenic activities such as rapid industrialisation, urbanisation and agricultural practice may increase the arsenic content in ground water in course of time.