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OVERVIEW OF LEACHING CHEMISTRY AND TESTING RESEARCH IN ORD/EPA
Citation:
AlAbed*, S R. OVERVIEW OF LEACHING CHEMISTRY AND TESTING RESEARCH IN ORD/EPA. Presented at Vanderbilt Workshop on Leaching Evaluation, Nashville, TN, July 09, 2004.
Impact/Purpose:
To inform the public.
Description:
Various anthropogenic activities generate hazardous solid wastes that are affluent in heavy metals and organics, which can cause significant damage to the environment and human health. Heavy metals can exist in multiple oxidation states, and can undergo oxidation or reduction when they interact with mineral surfaces or organic compounds. In natural environments, the mobility of these toxic metals is largely controlled by their interactions in their disposal environment. One of the major problems with solid wastes is the generation of large quantities of heavily contaminated leachate, which can cause extensive pollution of ground and surface aquatic bodies.
The U.S. EPA Toxicity Characteristic Leaching Procedure (TCLP) is the most common test used by regulatory agencies for classifying and comparing the leaching characteristics of different waste matrices. However, the test has several practical limitations and it stimulates only one set of landfill disposal conditions. As a regulatory screening test, TCLP was not designed to account for several important parameters that significantly affect the kinetics of the reactions occurring at the solid-water interface including pH, reactant concentrations, reprecipitation reactions and secondary phase formations, physical characteristics of the solid wastes, residence time and temperature. The need for more tailored and reliable assessment and prediction of leaching behavior of waste materials has evoked a need to incorporate these factors in evaluating the leaching behavior of waste materials generated anthropogenically or naturally. The Office of Research and Development in EPA represented by the National Risk Management Research Laboratory in Cincinnati is leading the research effort to develop consistent predictive methods, for short- and long-term risk assessment of waste materials containing environmentally toxic metals and organics, which would integrate the contributions of critical geochemical factors in addition to pH. Development and application of such predictive methods will aid in improving the current EPA approach of assessing metal leaching from anthropogenic and natural solid wastes.