Contribution of soil properties of shooting fields to lead biovailability and toxicity to Enchytraeus crypticus

Variation in soil properties may cause substantial differences in metal bioavailability and toxicity to soil organisms. In this study, lead bioavailability and toxicity to Enchytraeus crypticus was assessed after 21 days exposure to soils from different landscapes of a shooting range containing 47-2398 mg Pb/kg dry weight (dw). Soils had different pHCaCl2 (3.2-6.8) and organic matter contents (3.8-13% OM), therefore artificial soils with different pH and OM contents and two natural reference soils were included as controls. Effects on survival and reproduction and the uptake of Pb in E. crypticus were related to soil properties and total, water- and CaCl2-extractable and porewater Pb concentrations in the soils. Forest soils with pHCaCl2 < 3.5 and total Pb concentrations ≥2153 mg/kg dw had the highest bioavailability and toxicity of Pb to E. crypticus. At pHCaCl2 3.2 adult survival was inhibited and no juveniles were produced, while at pHCaCl2 3.8 reproduction was also reduced. Bioaccumulation of Pb linearly increased with increasing total soil Pb concentrations. The grassland soils with pHCaCl2 > 6.5 and total Pb concentrations 355-656 mg/kg dw were least toxic. This study shows that E. crypticus was very sensitive to acidic soils with pHCaCl2 ≤ 3.8, suggesting that the toxic effects in the most contaminated forest soils may have been due to the low soil pH rather than the high Pb concentrations.