Transformations of organic carbon and its impact on lead weathering in shooting range soils

Five soil samples collected from shooting ranges in 1998 were stored under a closed condition for 5 years. In addition to SEM and XRD investigations, the total organic carbon content (TOC), inorganic carbon content (TIC), δ13C and δ18O of carbonates and δ13C of plant remains were analyzed. The concentrations of total carbon contents, the sum of TOC and TIC, remained the same within the 5 years storage, whereas the TOC and TIC contents decreased and increased, respectively. The TIC increase is associated with a decreased TOC, suggesting a conversion of organic carbon into inorganic carbon. Such a conversion is evidenced by the presence of primary lead carbonates and carbon isotopic composition of lead carbonates. It can be concluded that soil organic matters play an important role in the process of bullets weathering and controls migration of the elevated lead in the soil.