Effect of legacy lead on leachability of tungsten and lead from differing soil types.

Abstract

Tungsten–nylon ammunition has been fired on ranges that are currently firing, or will fire in the future, lead-containing rounds, i.e. legacy lead (LL). In order to evaluate potential losses of the lead (Pb) and tungsten (W) from range soils into leachate, 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 effectiveness of the acidic solutions was compromised, due to pH effects on W solubility, and possible reactions of Pb and W producing forms of Pb that are not amenable to acidic extractions. However, the neutral solutions used for the DDI S&S tests and the initial SE exchangeable fraction (pH 7) were found to be better alternatives for concurrently evaluating lead and tungsten. Comparing leachability from LL-amended soils, with and without tungsten residues, showed, first, that the presence of tungsten residues did not necessarily result in increased Pb leachability, and may result in decreased soluble lead concentrations. Second, lead residues exhibited a variable influence on tungsten leachability. The effect of lead on tungsten leachability was, therefore, determined to be soil type-dependent for the six soils evaluated.