ABSTRACT
Impact of effluents discharged in Ganga through various sources on chemical composition, energy transformation rate and level of heavy metals was studied at Kanpur and Varanasi. The effluents were found to be nil in oxygen with acidic in oxygen with acidic to neutral pH (6.8-7.0) and having very high values of free CO2 (40-68 mg l-1), alkalinity (300.0-412.0 mg l-1), conductance (1082.0-1824.0 μmhos), total dissolved solids (542.0-912.0 mg l-1), hardness (228.0-330.0 mg l-1), chloride (42.0-60.0 mg l-1), organic matter (8.4-18.2 mg l-1) and BOD load (98.0-248.0 mg l-1). The heavy metals Cu, Cr, Cd, Pb and Zn were also quite high in the effluents (48.6-78.4, 54.0-84.6, 9.8-12.4, 72.4-84.0 and 148.6-284.0 μg l-1 respectively). The discharged effluents induced severe reduction in oxygen (av. 0.82-3.4 mg l-1) and sharp increase in the level of free CO2 (av. 10.8-24.8 mg l-1), alkalinity (182.4-288.4 mg l-1), conductance (480.0- 628.0 mmhos), total dissolved solids (254.0-315.0 mg l-1), hardness (170.0-259.0 mg l-1), chloride (36.0-52.0 mg l-1), organic matter (4.8-6.8 mg l-1) and BOD load (36.4- 58.4 mg l-1) at the discharge point (OF zones) from their comparatively much lower values before discharge (AOF zone). The rate of energy transformation and photosynthetic efficiency also reduced considerably at the discharge point (av. 1060-2101 calm-2day-1 and 0.09-0.18%) from high values before discharged point (av. 4045-4733 calm-2day-1 and 0.34-0.42%). The level of Cu, Cr, Cd, Pb and Zn also showed higher values at the discharged point (20.4-38.0, 22.4-54.8, 5.2-7.8, 30.8-72.0 and 64.8-120.8 μg l-1 respectively). Considerable improvement was observed below the discharge (BOF zone). Comparison with earlier observation revealed that the magnitude of impact has reduced considerably after the regulation in the discharge both in he respect of chemical composition and energy transformation rates.