Fate and behavior of metal(loid) contaminants in an organic matter-rich shooting range soil: Implications for remediation

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 indicated 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-EDX) showed that metallic Pb was transformed into lead oxides (litharge PbO and massicot PbO) and lead carbonates (hydrocerussite Pb 3 (CO 3 ) 2 (OH) 2 , cerussite PbCO 3 , and plumbonacrite Pb 5 (CO 3 ) 3 O(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 the 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 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, and were above the USEPA nonhazardous 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.

Chemical and physical characterization of lead in three shooting range soils in Florida

“…Untypical of contaminated soils, however, Pb concentrations were the highest in the very coarse sand fraction in all three range soils, which were 5 -10 times of those in the silt þ clay fraction (Figure 2). Our results were consistent with findings of Dermatas et al (2006a) who reported * 60% of Pb in the coarse fraction (40.425 mm) in shooting range soils. In those soils, there is a lot of fragmentation taking place due to bullets hitting bullets on a continuous basis, resulting in bullet fragments in the coarse fraction.…”

Effects of Biochar on Soil Quality and Heavy Metal Availability in a Military Shooting Range Soil in Korea

“…However, shooting activities produce the soil contaminated with heavy metals such as Pb from the used bullets (Dermatas et al, 2006). Nowadays, a huge amount of Pb is being deposited in the shooting range soil worldwide at an annual deposition rate of 200 to 60,000 tons (Craig, 1999;Mellor and McCartney, 1994).…”

“…Shooting ranges are commonly considered as the second largest source of soil Pb after development of the battery industry (Cao et al, 2008). The contamination of shooting range soil with Pb is well documented (Cao et al, 2008;Dermatas et al, 2006;Grubb et al, 2009;Hashimoto et al, 2009a). Most of the studies indicated that Pb levels in the shooting range soils exceed 1% (Chen and Daroub, 2002;Hashimoto et al, 2010) resulting in degrading soil quality, decreasing soil microbial activities and threating to living organisms (Belyaeva et al, 2005;Lee et al, 2002).…”

Lead contamination of an agricultural soil in the vicinity of a shooting range

“…The transformation of metallic Pb from pellets in soils can be described as: Pb → PbO → PbCO 3 /Pb 3 (CO 3 ) 2 (OH) 2 (Ma et al 2007); the formed Pb carbonates create a protective layer preventing further weathering of the pellets. The weathering rate of Pb is higher in organic soils compared to soils with low organic C contents (even calcite-rich soils) (Dermatas et al 2006) and the transformation of Pb into oxidized species is associated with an increase of soil pH. This is mainly attributed to (1) the consumption of H + ions during Pb corrosion (Pb 0 → Pb 2+ ), (2) the production of OH − ions during Pb carbonate formation, and (3) the subsequent H + consumption during the dissolution of Pb carbonates (Ma et al 2007;Rooney et al 2007).…”

“…Lead concentrations in shooting range soils often exceed 1,000 mg kg −1 (Lin et al 1995;Cao et al 2003a). There have even been evidences of concentrations well above 20,000 mg kg −1 (Lin 1996;Stansley and Roscoe 1996;Dermatas et al 2006). Therefore, the contamination of soils from the close vicinity of shooting ranges presents a serious environmental concern due to the risks associated with groundwater and surface water pollution (Craig et al 1999;Knechtenhofer et al 2003) and contamination of plants growing in the vicinity (Cao et al 2003b;Robinson et al 2008).…”