Abstract
Heavy metals viz., Pb, Cd, Cu, Cr, Zn and Ni in particular of water, soil and available fish species from these two rivers are examined. The higher amount of heavy metals found in soils viz., Pb varied between 29.04 mg/kg and 64.78; Cd varied between 0.31 mg/kg and 5.01 mg/kg; Cu varied between 40.13 mg/kg and 111.10 mg/kg; Zn varied between 75.19 mg/kg and 333.76mg/kg ; Cr varied between 51.51 mg/kg and 118.14 mg/kg and Ni varied between 35.81 and 44.41 mg/kg over the whole year. A remarkable amount of Pb, Zn, Cr was recorded in the whole fish species collected from both rivers. In Buriganga, Pb varied between 4.32 mg/kg and 31.51 mg/kg and in Shitalakhya 11.44 mg/kg and 17.03 mg/kg. Zn values ranged 3.95 mg/kg to 51.50 mg/kg in Buriganga and 6.29 mg/kg to 62.02 mg/kg in Shitalakhya. The similar trend of Cr was recorded at Buriganga and Shitalakhya and it’s ranged 7.83 mg/kg to 21.72 mg/kg. Cu and Ni were found under acceptable level. This finding indicates a major threat to human health in regard to consumption of fishes of those rivers. Dissolved oxygen (DO) content of the river Buriganga was found only 1.1 mg/l and 4.6 mg/l in Shitalakhya during winter. NH3, BOD, COD and conductivity were recorded very higher values both in winter and summer period. The lower survival rate of fishes in these rivers may directly related to the lower level of oxygen content. In addition, the study made observation that the water of these two rivers inhabitable for aquatic organisms during winter and summer periods. While during monsoon period water of these rivers were found fairly unpolluted and which may allow aquatic organisms to live it in that period.