GEOCHEMICAL CHARACTERISTICS OF THE ARSENIC-ENRICHED GROUNDWATER FROM INDIA, BANGLADESH AND TAIWAN

Major ion and trace element analyses have been performed on the groundwater samples collected from India (Chakdaha municipality, West Bengal), Bangladesh (Manikgonj town) and Taiwan (Chianan plain) to compare geochemical characteristics. Such geochemical differences might linked with the endemic Blackfoot disease (BFD) observed only in southwestern Taiwan during 1960s. The result shows that the concentrations of Na, K, Mg, Cl, and SO₄ were generally higher in Taiwanese groundwaters, while high Ca have been observed in both Indian and Bangladeshi groundwater. The measured As concentrations in Indian, Bangladeshi and Taiwanese groundwaters showed large variations, with mean As concentrations of 191 µg/L (7.0 to 417 µg/L), 84 µg/L (1.2 to 202 µg/L), and 208 µg/L (1.3 to 575 µg/L), respectively. The mean relative fluorescent intensity of humic substances is 62 and 71 for Indian and Bangladeshi groundwater, while 393 for Taiwanese groundwater. The Fe-reduction mechanism was supposedly the dominant geochemical processes in Indian and Bangladeshi groundwater, while seawater intrusion, mineral precipitation and dissolution reactions might have controlled the release of As in Taiwanese groundwater. The FT-IR spectra shows COO-, C=O, OH, and C=C (aromatic ring) functional groups in Taiwanese aquifer, which might have acted as a chelating agents bounded with the trace elements (especially arsenic). The observed geochemical differences might have played critical role in the clinical manifestation of BFD in Taiwan, which however not observed either in India and or in Bangladesh.