Particulate trace metals in Cochin backwaters: Distribution of seasonal indices

Abstract

A seasonal analysis of particulate trace metals, viz. iron, manganese, zinc, copper, cobalt and nickel collected from 4 stations in Cochin backwaters are presented. The spatial trend for cobalt, iron and nickel was stationary at surface whereas the metals copper, zinc and manganese showed spatial variations. At subsurface all the trace metals showed relatively an increasing trend at station 4, but for zinc and nickel, station 2 also showed higher values during the period of study. This indicated that surface distribution pattern of the trace metal concentration of cobalt, nickel and iron was almost similar at the four stations thereby stressing the fact that seasonal fluctuations contributed a major part in the surface distribution of these metals while in the case of other metals at surface and all the trace metals at subsurface, concentration varied both spatially and seasonally. Seasonal variations were maximum during August to December which remained almost uniform for all the metals. The rate of increase in the concentration during this period was less than the rate of decrease during the remaining period. Possible causes for this short term fluctuations are discussed. Deseasonalised effects were the least for iron, copper and nickel at subsurface but significant adverse effects were observed for copper and cobalt at surface