Effect of Seasonal Variation on Metal Speciation in Leachate from a Thermal Power Plant Ash Pond: Impact on Ground Waters

The concentration and extent of speciation of three environmentally important heavy metals, viz., Cd, Cu and Zn in the form of free ions and labile complex (C+F), slowly labile complex (CS1) and stable complex (CS) has been investigated in terms of percentage (%) in the Leachates from an ash pond of a 720mw thermal power plant in Delhi. The seasonal variations also have great influence on the total concentrations and speciation of these heavy metals in the ground water as well as in the leachates. The total concentration and speciation of these heavy metals is influenced by the physico-chemical parameters of the water column and also on the seasonal variations. For seasonal variation, the study has been carried out on the monsoon(MON) period (June, July and August), pre-monsoon(PRE) period (March, April and May), Post monsoon(POS) period (September, October and November) and the winter (WIN) season (December, January and February). Leachates containing different species of these heavy metals and other contaminants may have a deleterious effect on the receiving waters of the river Yamuna. Lysimeter studies simulating the generation of ash pond leachates have been conducted to ascertain the seasonal variation on leachability of different metal species. This may impart metal toxicity to the water body. Estimation of the speciation of these three heavy metals in the leachates and ground water, a picture of heavy metal distribution and the nature or extent of the speciation may be obtained.