Heavy metals and trace elements in hot spring water and biomats in southeastern Bangladesh

The existence of Hot spring at Kumira in Sitakund Upazila, Bangladesh has been known for a long time. About 100 years ago, underground hydrocarbons were explored in this region. However, no systematic studies of trace element and heavy metal in hot spring were carried out. To the best of our knowledge, trace elements and heavy metal levels in hot spring water, sediments are lacking in literature. Now a day, hot springs are also used for geothermal energy or hot spring bath which can play an important role in the tourism in Bangladesh. The current study aims at understanding the trace elements distribution in the hot spring water in southeastern region of Bangladesh. Hot spring water and different kinds of biomats proliferated near the hot spring were collected for trace element and heavy metal analysis. The hot spring water was observed to be clear and transparent. The samples had odor characteristic of sulfur containing compounds. Samples had odor where high concentrations of Na (43.4%) and Cl (40.2%) have been detected. Concentration of Ca (3.5%) and Mg (2.9%) are notable with traces of Al, Si, P, S, Ti, Cr, Fe, Zn, Ga, As, Br, Sr, and Cd. Furthermore, concentration of Si, P, K, Ca, Ti, V, Mn, Fe, Zn, As, Br and Sr in biomats were measured. The levels are indicative of accumulation of trace elements into the cell surface of biomats from the hot spring water. Although As in all biomats including hot spring water are common, but individual differences in trace element levels have been observed in white (Si, Fe and S rich), black (Si, Fe, K and Mn rich) and brown (Fe, K and Ca rich) biomats for the characteristics of the associated microorganisms in biomats. In the light of present study, it appears that a detailed study is needed for further understanding of the biogeochemistry of hot springs in Bangladesh which lies much closed to the Indian and Burmese plate, as well as the active Andaman -Nicobar fault system.

Key words: Hot spring, biomat, trace elements.