Fate and behavior of metal(loid) contaminants in an organic matter-rich shooting range soil: Implications for remediation |
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Authors: | Dimitris Dermatas Xinde Cao Valentina Tsaneva Gang Shen Dennis G Grubb |
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Institution: | (1) W.M. Keck Geoenvironmental Laboratory, Center for Environmental Systems, Stevens Institute of Technology, Hoboken, NJ 07030, USA |
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Abstract: | This study investigates the fate and behavior of lead (Pb), copper (Cu), antimony (Sb), and arsenic (As) in a shooting range
soil. The soil samples were collected from the surface (0–15 cm) and the subsurface (15–40 cm and 40–55 cm) of a grassy and
wood chip covered impact area behind a firing position. Optical microscopy images indicate significant amounts of corroded
bullet fragments and organic wood chips in the surface soil. Analysis by X-ray powder diffraction (XRPD) and scanning electron
microscopy electron dispersive X-ray spectroscopy (SEM-EDS) showed that metallic Pb was transformed into lead oxides (litharge
PbO and massicot PbO) and lead carbonates (hydrocerussite Pb3(CO3)2(OH)2, cerussite PbCO3, and plumbonacrite Pb5(CO3)3O(OH)2). Rietveld quantification indicated the surface soil contained 14.1% metallic Pb, 17.9% hydrocerussite, 5.2% plumbonacrite,
5.9% litharge, and 3.9% massicot on a dry weight basis, or a total of 39.7% Pb, far in excess of lead concentrations typically
found in US shooting range soils. Metallic Cu (bullet jacket material) appeared stable as no secondary minerals were detected
in the surface soil. As and Sb concentrations were on the order of 1,057 mg/kg and 845 mg/kg respectively. The elevated soil
pH coupled with high organic carbon content is thought to have caused downward migration of metals, especially for Pb, since
4,153 mg Pb/kg was observed at a depth of 55 cm. More than 60% of Pb was concentrated in the coarse soil (> 0.425 mm) fraction,
suggesting soil clean-up possible by physical soil washing may be viable. The concentrations of Pb, As, and Sb in the toxicity
characteristic leaching procedure (TCLP) extracts were 8,869 mg/L, 6.72 mg/L, and 6.42 mg/L respectively, were above the USEPA
non-hazardous regulatory limit (As and Pb) of 5 mg/L. The elevated Sb and As concentrations draw concern because there is
historically limited information concerning these metals at firing ranges and several values exceeded local soil cleanup criteria.
As the high Pb concentrations appeared to be linked to the presence of organic-rich berm cover materials, the use of wood
chips as berm cover to prevent soil erosion requires reconsideration as a shooting range management practice. |
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Keywords: | Lead arsenic copper antimony soil contamination shooting range soils |
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