Abstract:
Behaviour of Cd, Cu, Fe, Mn, Ni, Pb and Zn in the Bangpakong River was studied in the dry season (March, 2000) and wet season (July, 2000). All of the heavy metals showed non-conservative behavior in both seasons. In the dry season, salinity in the river varied from 8 psu at upstream the river to 32.5 psu at the river mouth. Dissolved Cd and Cu correlatively increased with salinity. This may result from desorption of heavy metals from sediment and suspended solid and bacterial decomposition of organic bound heavey metals. Fe, Mn, Ni and Zn moved from dissolved phase to suspended solid phase between 8 and 27 psu. Behaviour of Pb was more complicated and showed no clear trend. In the wet season, salinity in the river varied from 0 psu at upstream the river to 0.5 psu at the river mouth and river water composition showed a strong impact from terrestrial erosion. Dissolved heavy metal showed an increasing trend from upstream the river to station 6 then decreased toward the river mouth, which may caused by seawater dilution. Dissolved heavy metal concentration in the wet season (except Cd) were higher than the dry season, while particulater heavy metal concentration in the dry season (except Cd) were clearly higher than the wet season. In both seasons, Cd was found more in dissolved phase whereas up to 70% of the other heavy metals were found more in suspended solid phase. Cd, Cu, Ni, Pb and Zn in suspended solid phase strongly correlated with Fe and Mn, especially in the dry season.