Assessment of Heavy metals in water, sediment, macro vegetation and fish of Lake Nainital
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Date
2017-06
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Assessment of heavy metals concentration in water, sediment, macro vegetation and fish of Lake Nainital was made from September 2016 to February 2017 with the help of Atomic Absorption Spectrophotometer (AAS) in the present investigation to evaluate pollution status of the lake. Three sites viz., S1 (Aeration centre at thandi sadak), S2 (platform near the Naina Devi Temple in Mallital) and S3 (boat stand in Tallital near bus stand) were selected based on pollution level and fortnightly sampling was done. The important physico-chemical parameters such as temperature, electrical conductivity, TDS, transparency, pH, DO, free CO2, alkalinity and hardness of the lake were also analyzed which varied from 13.8-250C, 139-190 µS cm-1, 161-218 mg L-1, 176-292 cm, 7.3-8.3, 5.27.8 mg L-1, 3.5-7.3 mg L-1, 161-220 mg L-1 and 110-205 mg L-1 respectively. The average concentration of heavy metals in water and soil of Lake Nainital during investigation period were observed as Zn(0.029 mg L-1), Pb(0.346 mg L-1), Cu(0.113 mg L-1), Mn(0.361 mg L-1), Cd(0.007 mg L-1), As(0.001 mg L-1) and Zn(0.871 mg L-1), Pb(1.150 mg L-1), Cu(0.156 mg L-1), Mn(1.778 mg L-1), Cd(0.132 mg L-1), As(0.003 mg L-1) respectively. The mean concentration of heavy metals in leaves and roots of studied macrophyte were Zn(0.004 mg L-1), Pb(0.019 mg L-1), Cu(0.012 mg L-1), Mn(0.075 mg L-1), Cd(0.0004 mg L-1), As(0.0009 mg L-1) and Zn(0.004 mg L-1), Pb(0.014 mg L-1), Cu(0.005 mg L-1), Mn(0.044 mg L-1), Cd(0.0001 mg L-1), As(0.0007 mg L-1) respectively. The observed concentration of heavy metals in fish gills and muscles were Zn(2.233 mg L-1), Pb(0.851 mg L-1), Cu(0.051 mg L-1), Mn(0.840 mg L-1), Cd(0.074 mg L-1) and Zn(0.247 mg L-1), Pb(0.150 mg L-1), Cu(0.013 mg L-1), Mn(0.423 mg L-1), Cd(0.00 mg L-1) respectively. The values of heavy metal pollution index shows that the water of Lake Nainital is slightly affected with Mn and seriously affected with Pb. Values of Bio-concentration Factor reflected that gills of selected fish serve as hyper-accumulator for Zn, Mn and Cd whereas muscles were hyper-accumulator for Zn and Mn. No hyper-accumulation was recorded in leaves or roots of macrophyte. The study concludes that the presence of elevated levels of Pb and Mn in lake water poses threat to human population as the lake water is used for domestic water supply. Also the increased level of Zn, Mn and Cd in fish is a matter of concern as it can result in imbalance of food web in the lake.
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