Introduction For the past century, both wastewater and solid wastes have been deposited in the vast wetland areas located at the eastern fringe of Calcutta in India. The east Calcutta wetland is the largest urban wetland eco- system in India covering 12,500 ha, which includes 286 wastewater-fed fishponds spread over 3,832.27 ha (over 30% of the total wetland area), producing 10,915 metric tonnes of fish annually (Statesman News Service, 1998). In the Dhapa area of the east Calcutta wetland, solid municipal garbage and sludge filled soils are used for agriculture. Between 2,000 and 3,000 metric tonnes of solid wastes, in differ- ent forms, are being deposited daily in the wetland areas. Garbage farming yields nearly 370,650 kg ha –1 y –1 vegetables, which amounts to 150 metric tonnes of vegetables daily. Huge composite efflu- ent mixed city sewage (around 50,000 m 3 d –1 ) from Calcutta is discharged in the raw state, without any pre-treatment, to a number of canals via nine impor- tant drainage pumping stations (DPS). Besides large volume of municipal wastewater, these canals also carry effluents from at least 538 tanneries in three prominent agglomerates and approximately 5,500 other small-scale industrial establishments such as rubber industries, electroplating industries, pigment manufacturing units, potteries, and battery manufac- turing plants. Composite industrial effluent together with municipal wastewater flows down through a web Bioaccumulation of metals in the East Calcutta wetland ecosystem Buddhadeb Chattopadhyay 1* , A. Chatterjee 2 , S. K. Mukhopadhyay 2 1 College of Leather Technology, LB Block, Sector III, Salt Lake, Calcutta 700 098, India; 2 Hooghly Mohsin Govt.College, Chinsurah, Hooghly 712 101, West Bengal, India. Corresponding author: E-mail: cbuddha@hotmail.co m 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 sus- pended 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 sew- age-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. Keywords: Wastewater, solid wastes, heavy metals, fish, plant, EIA 191 Aquatic Ecosystem Health & Management, 5(2) 191–203, 2002 © 2002 AEHMS 1463-4988/02 $12.00 + .00 DOI: 10.1080 /14634980290031848