No abstract

The Toxicity Characteristic Leaching Procedure (TCLP) is used by the United States Environmental Protection Agency to determine if wastes contain extractable components subject to hazardous waste regulations. This paper examines the limitations of the TCLP and the way it is used by studying a particular example. Waste casting sand from brass foundries to which iron metal has been added passes the TCLP test but when placed in a landfill for several years may start to leach lead, copper, and zinc. Results of TCLP tests of waste sand alone and with the additives iron metal, zinc metal, hydrous ferric oxide, and hematite are reported. Three processes were studied: reduction by metallic iron, sorption by hydrous ferric oxide, and precipitation of hydroxides. Lead, copper, and zinc behave differently with respect to these three processes, and their measurement allows some deductions as to what is occurring in a TCLP test or a landfill. Iron addition does not result in long-term stabilization of a waste placed in the ground. The chemistry of a laboratory extraction can be very different from the chemistry of a waste placed in the environment. Wastes that are treated to pass the TCLP test, but are not permanently stabilized, are a threat to the environment.

Groundwater at or near Superfund sites often contains much organic matter, as indicated by total organic carbon (TOC) measurements. Analyses by standard GC and GC/MS methodology often miss the more polar or nonvolatile of these organic compounds. The identification of the highly polar or ionic compounds may be needed to assess toxicity more reliably, to plan remediation, and to establish the possible source of a waste and the responsible party. This study characterized water samples from two Superfund sites for organic components where routine methods had failed to account for a majority of the TOC. Carboxylic acids, alcohols, and ketones were detected by GC/MS using a new capillary column designed for polar organic compounds. Particle beam LC/MS allowed for identifying several additional compounds. Finally, thermospray LC/MS was shown to be an excellent means of detecting ionic constituents, such as aromatic sulfonic acids, in the water samples.