METAL SPECIATION STUDIES: EVALUATION OF AN . ALTERNATIVE EXTRACTION SCHEME

Abstract

The application of digested waste water sludge to agricultural land has been recognized as an environment-ally desirable means of sludge disposal. However due to the presence of heavy metals in high concentration in .certain sludges soil may be enriched with the metals app-lied 'along with the sludge and it may create potential hazards to agronomic plants and the food chain. Therefore it is necessary to determine the consequences of repeated sludge application to crop land. An appreciation of the effect of heavy metals in sludge on crops can only be attained from a precise know-ledge of heavy metals speciation. In order to gain an insight in the metal pollution caused by land application of sludges it is necessary to know the form of the metal present. Metal species in sludges have generally been investigated by selective; sequential extraction technique. A survey of literature reveals that several such scheme are in use but the extraction sequence proposed by Stover et al. (1976) is more frequently' used. Stover scheme consist of set of extractant used in particular sequence. Here extraction is carried out by breaking the sequence and applying the stover's reagents discretely. Variation in metals extractibility studied with respect attempt to unit wt. of sludge to reagent volume ratio and an/has'been made to correlate aspect of additive extractions by discrete extractions at additive w/v ratio.