Spatial Distribution and Speciation of Lead around Corroding Bullets in a Shooting Range Soil Studied by Micro-X-ray Fluorescence and Absorption Spectroscopy

Abstract

We investigated the spatial distribution and speciation of Pb in the weathering crust and soil surrounding corroding metallic Pb bullets in a shooting range soil. The soil had a neutral pH, loamy texture, and was highly contaminated with Pb, with total Pb concentrations in the surface soil up to 68 000 mg kg(-1). Undisturbed soil samples containing corroding bullets were collected and embedded in resin, and polished sections were prepared for micro-X-ray fluorescence (micro-XRF) elemental mapping and micro-X-ray absorption near edge structure (micro-XANES) spectroscopy. Bullet weathering crust material was separated from the metallic Pb cores and analyzed by powder X-ray diffraction analysis. Our results show a steep decrease in total Pb concentrations from the bullet weathering crust into the surrounding soil matrix. The weathering crust consisted of a mixture of litharge [alpha-PbO], hydrocerussite [Pb3(CO3)2-(OH)2], and cerussite [PbCO3], with litharge dominating near the metallic Pb core and cerussite dominating in the outer crust, which is in contact with the soil matrix. On the basis of these results and thermodynamic considerations, we propose that the transition of Pb species after oxidation of Pb(O) to Pb(II) follows the sequence litharge --> hydrocerussite --> cerussite. Consequently, the solubility of cerussite limits the activity of Pb2+ in the soil solution in contact with weathering bullets to < or =1.28 x 10(-6) at pH 7, assuming that the CO2 partial pressure (PCO2) in the soil is equal or larger than in the atmosphere (PCO2 > or = 0.000 35 atm).

Speciation Of Pb In Industrially Polluted Soils

“…X-Ray Powder Diffraction (Ettler et al, 2005), X-Ray Absorption Fine Structure (Ostergren et al, 1999) and more (Jorgensen and Willems, 1987;Vantelon et al, 2005;Ostergren et al, 1999;Manceau et al, 1996). Transformation of metallic Pb into hydrocerussite (Pb 3 (CO 3 ) 2 (OH) 2 ), cerrusite (PbCO 3 ) and (less commonly) anglesite (PbSO 4 ) in shotgun pellets was observed in several studies (Jorgensen and Willems, 1987;Lin et al, 1995;Vantelon et al, 2005). The transition sequence was suggested to be litharge (α-PbO) → hydrocerrucite → cerrucite (Vantelon et al, 2005).…”

Leaching Behavior of Copper, Zinc and Lead from Contaminated Soil with Citric Acid

“…The different location and the different weathering conditions under which samples A and B were exposed, could be accounted as the probable main reason of the differences in the amount extracted for each fraction of soil samples A and B. Vantelon et al summarized studies about soil contaminated with Pb, and reported that the outer part of Pb bullet, which penetrated soil, is slowly oxidized and weathered into hydrocerussite [Pb 3 (CO 3 ) 2 (OH) 2 ], cerussite (PbCO 3 ), massicot (¢-PbO), litharge (¡-PbO) according to chemical conditions. 17) Therefore, metal components, which belong to "bound to carbonate" and "bound to FeMn oxide" categories, would resulted from the oxidation of metal bullet according to chemical conditions around the bullet. Figures 11 to 13 show the comparison between the summation of "exchangeable", "bound to carbonate" and "bound to FeMn oxide" fractions and the amount leached with 2 kmol·m ¹3 citric acid solution for 2 h, respectively, for Cu, Zn and Pb.…”

Preparing Adherent Cells for X-ray Fluorescence Imaging by Chemical Fixation

“…X-ray fluorescence imaging is useful in many fields, including geosciences, materials science, and chemical biology [26][27][28][29][30][31][32][33][34] . Advances in synchrotron X-rays, and their focusing, have produced very high-intensity beams.…”