RETENTION OF FLY ASH-DERIVED COPPER IN SEDIMENTS OF THE PANDU RIVER NEAR KANPUR, INDIA

A coal-based thermal power plant is situated on the bank of the Pandu River, which is a tributary to the Ganges near Kanpur. River sediments downstream from the ash pond outfall are contaminated by fly ash. In order to establish the role of soils and sediments in retaining fly as h-derived heavy metals, copper was investigated as a model metal. A ma ximum concentration of 70 ppm Cu could be leached from the fly ash, co nfirming that it is a major source of this metal. Soil samples and riv er sediments were examined for Cu adsorption in the natural state as w ell as after treatment with H2O2, EDTA, and H2O2 followed by EDTA. The organic fraction of the samples was determined, and it had a major co ntrol on removal of Cu from a solution with 10(-4) M initial concentra tion. Further characterization of organic matter indicated that with r eference to natural samples, the humic acid fraction had a copper enri chment factor in the range 9.1-15.1. The factor for fulvic acids, in c ontrast, was between 3.5 and 5.5. This leads to the conclusion that ri ver deposits rich in humic acids would withstand relatively high metal loads. Only when the metal input exceeds the maximum retention potent ial, would the metal be fractionated into the aqueous phase and act as a potential biocide.