Toxicity characteristic leaching procedure fails to extract oxoanion-forming elements that are extracted by municipal solid waste leachates

U.S. EPA and state regulatory agencies rely on standard extraction tests to identify wastes that have the potential to contaminate surface water or groundwater. To evaluate the predictive abilities of these extraction tests, the Toxicity Characteristic Leaching Procedure (TCLP), the Waste Extraction Test (WET), and the Synthetic Precipitation Leaching Procedure (SPLP) were compared with actual municipal solid waste leachates (MSWLs) for their ability to extract regulated elements from a variety of industrial solid wastes in short- and long-term extractions. Shortterm (18 and 48 h) extractions used MSWLs from a variety of California landfills. Long-term sequential extractions (48-84 days) simulated longer term leaching, as might occur in MSW landfills. For most regulated elements, the TCLP roughly predicted the maximum concentrations extracted : by the MSWLs. For regulated elements that form oxoanions (e.g., Sb, As, Mo, Se, V), however the TCLP underpredicted the levels extracted by the MSWL. None of the standard tests adequately predicted these levels. The results emphasize the need for better standardized techniques to identify wastes that have the potential to contaminate groundwater with oxoanion-forming elements, particularly arsenic.