Seasonal variation of Zn, Cu and Pb in the estuarine stretch of West Bengal
Zn, Cu and Pb levels in the aquatic phase and underlying surface sediment from three stations (viz. Shankarpur, Canning and Bali Islands) of the coastal zone of West Bengal during different seasons in 2002 were recorded. The order of the heavy metal level in the ambient media of the selected stations is Zn> Cu> Pb. Highest concentrations of heavy metals were recorded in the surface water during monsoon, the period characterized by lowest salinity and pH of the ambient aquatic phase. During premonsoon season all the dissolved heavy metals exhibited minimum values. The biologically available heavy metals from surface sediment of the selected stations showed highest values during premonsoon and lowest during monsoon. Significant negative correlations between the concentrations of dissolved heavy metals and biologically available heavy metals from surface sediments elucidates a sharp exchange of selected metals between the aquatic phase and sediment in the study area.