| Research was performed to evaluate methodologies currently used to assess risk to human health and the environment through groundwater contamination from the leaching of inorganic contaminants from land-applied industrial waste. This was accomplished through the detailed characterization of one particular type of solid waste (wood and tire (WT) ash), followed by a critical evaluation of the results with respect to current methodologies for assessing risk from the leaching of contaminants to groundwater. The toxicity characteristic leaching procedure (TCLP), synthetic precipitation leaching procedure (SPLP) and deionized (DI) water extracted statistically similar concentrations of inorganic constituents. When compared to California's waste extraction test (WET), the TCLP extracted statistically lower concentrations of most inorganic constituents but statistically similar concentrations of barium, calcium and lead. Of the three factors that impact inorganic contaminant leachability examined, extraction pH was found to control metal leachability to the greatest extent.; Lysimeter leaching tests were conducted to better simulate actual environmental conditions. Statistically, the depth of the ash layer did not have an impact on the leachate quality generated by the lysimeters. Except for chromium, statistically similar concentrations of other metals were extracted by lysimeter and batch leaching tests. The lysimeter leachate extracted lower concentrations of ions at equivalent liquid-to-solid ratio than batch leaching tests, but based on the total mass extracted both methods extracted similar concentrations.; Comparing total metal content to theoretical back calculated risk-based standards for leaching found that arsenic, chromium and zinc posed an unacceptable groundwater contamination risk. The risk assessment using the SPLP, however, found aluminum, manganese, sulfate, total dissolved solids and pH to exceed their secondary drinking water standards (DWS). Lead exceeded its risk-based primary DWS in the SPLP leachate. Lysimeter results indicated that aluminum, pH, total dissolved solids (TDS), chlorides and sulfate exceeded their respective secondary DWS and lead exceeded its primary DWS.; The lysimeter leachate concentrations were used to examine a hypothetical land application scenario using the computer program MYGRT. The model indicated that under conditions of sufficient dilution, the land application of WT does not pose an unacceptable risk via groundwater. As a result with limitations with the existing approaches, an alternative approach for assessing risk from land-applied waste was presented. The approach relies on estimating the pore water concentration of the solid waste, and utilizes results from the SPLP and batch leaching test conducted at a much lower liquid-to-solid ratio to approximate the pore water concentrations. |
