Lead particle size and its association with firing conditions and range maintenance: implications for treatment

Abstract

Six firing range soils were analyzed, representing different environments, firing conditions, and maintenance practices. The particle size distribution and lead (Pb) concentration in each soil fraction were determined for samples obtained from the backstop berms. The main factors that were found to influence Pb fragment size were the type of soil used to construct the berms and the type of weapon fired. The firing of high velocity weapons, i.e., rifles, onto highly angular soils induced significant fragmentation of the bullets and/or pulverization of the soil itself. This resulted in the accumulation of Pb in the finer soil fractions and the spread of Pb contamination beyond the vicinity of the backstop berm. Conversely, the use of clay as backstop and the use of low velocity pistols proved to be favorable for soil clean-up and range maintenance, since Pb was mainly present as large metallic fragments that can be recovered by a simple screening process. Other factors that played important roles in Pb particle size distribution were soil chemistry, firing distance, and maintenance practices, such as the use of water spray for dust suppression and deflectors prior to impact. Overall, coarse Pb particles provide much easier and more cost-effective maintenance, soil clean-up, and remediation via physical separation. Fine Pb particles release Pb more easily, pose an airborne Pb hazard, and require the application of stabilization/solidification treatment methods. Thus, to ensure sustainable firing range operations by means of cost-effective design, maintenance, and clean-up, especially when high velocity weapons are used, the above mentioned factors should be carefully considered.

Lead pollution of shooting range soils

“…The other seven shooting ranges had a mixture of both cerussite and hydrocerussite. A study by Dermatas et al (2007) was able to show that the carbonates are some of the dominant weathering products of Pb bullets and shots in shooting range soils. 36 …”

Phosphate application to firing range soils for Pb immobilization: The unclear role of phosphate

“…The most common Pb species in firing range soils are metallic Pb fragments, carbonates, anglesite, and litharge, depending on the pH and the presence of sulfate [4][5][6][7][8][9][75][76][77][78]. Pb may also be encountered sorbed on iron and aluminum oxyhydroxides and on soil organic matter.…”

“…The rate of metallic Pb weathering varies greatly, and values differing up to four orders of magnitude have been reported in the literature [75]. The particle size of the bullet fragment plays a major role in the rate of Pb weathering and is a function of the firing conditions and management practices at the range [9]. For example, the use of high-velocity weapons (rifles) leads to a higher degree of bullet fragmentation (generation of Pb fines) compared to low-velocity weapons (pistols) [9].…”

“…Furthermore, the mechanisms and kinetics of contaminant removal/immobilization need to be established to reliably predict treatment in the short-and long-term under different conditions. The authors of this paper participated in an extensive investigation on metal contamination in firing ranges operated by the U.S. Department of Defense (U.S. DoD); the results on Pb speciation and leaching behavior for several ranges are presented in Dermatas et al [4][5][6][7][8] and Dermatas and Chrysochoou [9]. The characteristics of the examined sites varied greatly with respect to such factors as the magnitude of Pb concentration, Pb fragment particle size distribution, soil pH, particle size and the mineralogy of the soils.…”

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

“…Between 45 and 69% of the total Pb were extracted by TCLP in this study, which are comparable with Cao et al (2003b) who did the same analyses in five shooting ranges in Florida (41 -80%). However, the ratios in four range soils are different in the study of Dermatas et al (2007). The range soils have much lower total Pb concentrations (1.0 -49 mg g À 1 ) and much larger range of TCLP-Pb to total Pb ratio (0.4 to 98%).…”