Effect of soil type on tungsten leachability.

Abstract

In order to evaluate the potential loss of tungsten associated with small-arms ammunition from range soils into leachate and runoff water, preand post-firing soils were subjected to three leaching/ extraction techniques: the distilled, deionized water suspend and settle (DDI SS the toxicity characteristic leaching procedure (TCLP); and the sequential extraction (SE) procedure. The SE, and, to a lesser extent, the TCLP extraction, were not effective for evaluating tungsten mobility, because of the inverse relationship between acidity and the solubility of tungsten species. However, results from DDI S&S tests and the exchangeable SE fraction do provide some information about the potential for migration of tungsten from soil. The concentration of tungsten obtained using the DDI S&S procedure was highest in leachates from Sand and Glacial Till and lowest in leachate from Muck. The two soil types (Sand and Glacial Till) that exhibited high leachability in the DDI S&S leaching procedure also produced SE-exchangeable extraction solutions that contained the highest tungsten concentrations. Because of the unique properties of elemental tungsten with regard to oxidation and dissolution in aqueous solutions, TCLP and the acid-derived SE procedure are less useful for predicting the long-term leachability of tungsten than the DDI S&S procedure.