Lead transformation in the environment of small-arms firing ranges

Toxic levels of lead (Pb) are often found in soils of army training facilities. This is a result of bullet build-up in and around impact areas. This study was performed in order to assess Pb contamination in the soils of six firing ranges located in California and New Jersey. The soils tested have differences in pH and they range from acidic (pH~4.5) to alkaline (pH~8.75). In some samples, total Pb values were as high as 49,228 mg/kg. Toxicity characterization leaching procedure (TCLP) experiments were conducted to examine Pb mobility. The results from these experiments showed that the soil leached more Pb than acceptable under EPA regulations. TCLPPb in surface samples was as high as 594 mg/L. The metallic Pb present could have been transformed into different weathering products, which would determine Pb solubility and bioavailability. Sequential extractions of the different berm soils will determine the amount of readily available Pb as well as the amount of potentially available Pb and Pb that has been transformed to non-labile forms. The following phases were identified: exchangeable, carbonate, iron and manganese oxides, organic matter and sulfides and residual bound- Pb. The majority of Pb in most locations was found in the carbonate phase of the soils. Soils with a high buffering capacity did not follow this pattern and released the majority of Pb with the Fe-Mn oxides phase of soils. In two of the ranges tested up to 20% of the leached Pb was associated with the exchangeable phase, which indicates that Pb is highly bioavailable in the soils. Remediation techniques such as phytoremediation and chemical washing are recommended for some of the ranges based on the results of this study.

• INTRODUCTION

• SAMPLING AND METHODS

• RESULTS AND DISCUSSION

• CONCLUSIONS

• REFERENCES

• ACKNOWLEDGEMENTS