Legacy Lead Research Articles

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

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.

The potential for bioaccumulation of tungsten in earthworms - the effect of legacy lead on biouptake

Studies have shown that the metal components in a soil influence the geochemical processes that occur in that soil (McGregor and Blowes 2002; Dermatas 2004; Petrunic and Al 2005). Since tungsten–nylon rounds have been fired on ranges that have historically been used for training using lead rounds, questions have been raised as to the effect that tungsten has on weathered lead and the other constituents in soils. Possible interactions with the various metals in the soil may affect tungsten’s solubility or sorption properties, which may in turn influence its bioavailability. In order to determine the effect of weathered lead on tungsten biouptake, a bioavailability study was conducted using earthworms (Eisenia fetida). This study allowed direct comparison of lead and tungsten biouptake in a variety of soils amended with weathered lead and fired on with tungsten–nylon bullets. The effects of soil aging on biouptake were also studied. Results indicate that changes in earthworm biouptake of lead and tungsten, which resulted from the presence of legacy lead (LL) material in soils, varied and were soil-type dependent. Soil aging generally did not affect the biouptake of lead or tungsten by earthworms.