## 3 Results and Discussion
### Geochemical Properties of Soil
The Pb concentrations of soils in Cho-do and We-rye, Korea, exceeded 18,609 \(\pm\) 1202 and 3918 \(\pm\) 127 ppm, respectively [3]. Similar results were obtained for an outdoor shooting range in Michigan, which was also contaminated with heavy metals [24]. [PERSON] et al. [24] reported that the Pb, Cu, Ni, Cd, and Zn concentrations are 10 to 100 times higher than those of the background soil. The Pb concentration in soils from shooting ranges worldwide ranges from ~10,000-70,000 mg/kg [2]. This heavy metal enrichment can also be observed in the element maps obtained by EPMA analysis. Heavy metals, such as Pb, As, Cd, Ni, and Zn, are distributed in certain  
Figure 2: The Zn, Pb, Cd, As, Ni, and Cu concentration (ppm) of soils from (**a**,**c**,**e**) 3 rd and (**b**,**d**,**f**) 6 th shooting lane with (**g**) background and (**h**) drain ditch for each transect. The blue, green, red bars are indicative of vertical soil profiles of surface (0–10 cm), subsurface (10–30 cm), and the deeper soil (30–50 cm). minerals (Figure 3). Based on the XRD analysis, the predominant minerals are quartz, albite, microcline, muscovite/illite, kaolinite, chlorite, and calcite (Figure 4). Note that Pb minerals were not detected in this study. It can be assumed that the heavy metals from bullets are adsorbed at the mineral surfaces. The pH values of the soils from the third and sixth shooting lanes and drainage ditch (pH = 7.50-8.94) are higher than that of the background soil (pH = \(\sim\)6.00) at most targets in all transects, except for the 250 m transect in the third shooting lane (Figure 5, Table 1). This agrees with the results of a previous study [6] based on which the pH values of contaminated soils in shooting ranges in the Czech Republic (average pH = 5.9) are higher than those of the control sample (average pH = 4.6). The higher pH of the contaminated  
Figure 4: Representative mineralological composition of soils from the shooting range determined using X-ray diffraction (XRD). Figure 3: Element maps for (**a**) BSE image, (**b**) Pb, (**c**) As, (**d**) Cd, (**e**) Ni, and (**f**) Zn in soils from the shooting range obtained from EPMA analysis. soil leads to the weathering of Pb bullets and transformation of metallic Pb into oxidized species [5]. During these processes, the consumption of H\({}^{+}\) ions within soil leads to an increase in the soil pH [6]. These pH-dependent processes control the dissolution of Pb from bullets [6]. Lead has four isotopes (\({}^{204}\)Pb, \({}^{206}\)Pb, \({}^{207}\)Pb, and \({}^{208}\)Pb) and the \({}^{206}\)Pb/\({}^{207}\)Pb and \({}^{208}\)Pb/\({}^{207}\)Pb ratios can be used as indicators of different sources [33]. The \({}^{206}\)Pb/\({}^{207}\)Pb ratio is used as an indicator of anthropogenic Pb sources [6]. The Pb isotopic signatures are commonly used in environmental studies [10; 11; 34; 35; 36; 37; 38]. However, they have been rarely applied for the analysis of heavy metal contamination in soils from shooting ranges [6]. The Pb isotopes of soils from the sixth shooting lane (B, D, and F in Figure 1) were analyzed and compared with those of drainage ditch and background samples. The \({}^{206}\)Pb/\({}^{207}\)Pb and \({}^{208}\)Pb/\({}^{207}\)Pb ratios of the soils from the sixth shooting lane range from 1.171 to 1.199 and from 2.381 to 2.490, respectively. The \({}^{206}\)Pb/\({}^{207}\)Pb ratios of the drainage ditch and background sample are 1.014-1.018 and 1.163-1.171, respectively (Table 2). [PERSON] et al. [35] investigated the Pb isotopes of urban soils in Athens. The \({}^{208}\)Pb/\({}^{206}\)Pb and \({}^{206}\)Pb/\({}^{207}\)Pb ratios displayed linear trends and plotted between the two endmembers of natural (high \({}^{206}\)Pb/\({}^{207}\)Pb) and anthropogenic (low \({}^{206}\)Pb/\({}^{207}\)Pb) sources [35]. This is consistent with our results. The \({}^{208}\)Pb/\({}^{206}\)Pb and \({}^{206}\)Pb/\({}^{207}\)Pb ratios of the soils analyzed in this study exhibit a negative correlation and plot between the two endmembers (Figure 6a).