IMPACT OF COPPER AND LEAD ON THE WATER QUALITY AND GROWTH OF LEMNA MINOR L. IN MACRO PHYTE PONDSN.C. THARAVATHY, K.K. SRAVYA RAVEENDRAN AND SHOBITH
Aquatic plants are known to accumulate heavy metals. Duckweed plants (Lemna minor L.) were exposed to different concentrations of copper and lead. Various physico-chemical parameters like temperature, electrical conductivity, total dissolved solids (TDS) and pH, impact of Cu and Pb on the growth of Lemna minor and its phyto remediation potential were studied. Temperature recorded was low in Cu treated and high in Pb treated freshwater ponds than control. pH recorded was high in both Cu and Pb treated ponds than control. Electrical conductivity recorded was high in Cutreated ponds than the control and in Pb treated ponds, it was lower than the control in 0.5 mg/L Pb treated pond and higher than the control in 1.0 mg/L Pb treated pond. TDS in Cu treated ponds recorded was 265Â±0.00 mg/L in control which was significantly increased to 277Â±1.00 mg/L and 296Â±1.00 mg/L in 0.5 mg/L and 1.0 mg/L of Cu treated ponds respectively. In Pb treated ponds, it was 267Â±2.00 mg/L in control which was non-significantly decreased to 256Â±2.00 mg/L in 0.5 mg/L Pb treated ponds and increased to 271Â±2.00 mg/L in 1.0 mg/L Pb treated pond. Percentage mortality ofL. minorL. on day 15, 20, 25 and 30 showed that the toxic effect by Pb exposure was more than that of Cu. The LC50 values reported for Cu and Pb were 0.50 mg/L and 0.37 mg/L respectively. The significant increase in uptake of Cu than Pb showed that L. minor L. is more suitable to remediatesites contaminated with Cu than Pb.
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