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Bioaccumulation of metals in the East Calcutta wetland ecosystem

This study was initiated to examine the extent of toxic metal contamination of the east Calcutta wetland ecosystem. Biological oxygen demand, chemical oxygen demand, total dissolved solids, conductivity, total suspended solids, total hardness, and pH were recorded from six different locations on the sewage carrying canals including an industrial effluent-fed fish pond in the eastern Calcutta (lat. 22°33´-22°40´ N;long. 88°25´-88°35´E). Concentrations of metals such as Pb, Cu, Cr, Zn, Fe, Mg, and Mn in wastewater, and water of adjacent sewage-fed fish tank were also determined. Concentrations of these metals in soil/sludge and accumulation of these metals in plant and fish tissues were also studied. The concentrations of heavy metals in wastewater, namely Pb, Zn, Cu, Mn, and Fe, were reduced by 25 to 45% and total Cr was reduced by 95%, on the course of the 40 km long journey of the composite wastewater from the sources to river mouth via the wastewater carrying canal and the stabilization pond. Reductions of 65% Zn and 99% Cr in soil/sediment were recorded between sources and final discharge sites.