LEAD BEHAVIOR AT NATIONAL FOREST SHOOTING RANGES

One of the many uses of National Forest lands is recreational shooting. Although the many users of shooting ranges enthusiastically support this activity, others citizens are concerned about the very large amounts of metallic lead that accumulate in relatively small areas.

Soil sampling at our study site on the National Forest shooting range near Blacksburg, Virginia documented that more than 11 metric tons of metallic lead accumulated on the shotgun range between 1993 and 2003 with an estimated equivalent amount accumulated on the adjacent rifle range during the same time. X-ray diffraction analysis of the coatings on the bullets and shot indicates that they are corroding to form predominately hydrocerrussite. This result is consistent with the mineralogy predicted by Eh-pH diagrams. Hydrolysis diagrams predict that hydrocerrusite is only slightly soluble in rainwater and we found that ponded rainwater on the range contains up to 473 ppb of dissolved lead. Extraction studies of soil samples show that the top few centimeters of the soil profile on the shotgun range contain an average of 340 ppm of extractable lead (off site average=12 ppm) that was presumably released from the corroding metallic lead. Lead concentrations in soil samples from deeper horizons were at or near background values. The lead is mostly bound to iron and manganese oxides, carbonates, and organic matter. In addition to metallic lead accumulation in the soils, significant amounts lead shot and bullets have accumulated in nearby trees leading to concerns about their possible classification as hazardous waste.

The study provides information that can guide the development of best management practices for this and similar sites. Because geochemical conditions vary from place to place, we expect that shooting ranges in different settings will exhibit different lead corrosion and mobility patterns. We recommend that each of these sites be investigated using a protocol similar to the one described here.