## 3 Results and Discussion  
### Spatial Distribution Characteristics of PTEs  
The statistical analysis of PTEs in atmospheric deposition is summarized in Table 4. All skewness coefficients for PTEs exceed 1, indicating a right-skewed distribution, where median concentrations are lower than mean concentrations. Due to the presence of concentrations skewed towards lower values, the median provides a more reliable measure than the mean for PTEs in atmospheric deposition in and around IAREEM areas [35; 36]. The median concentrations of PTEs followed the order of Pb > Cu > Cr > Ni > As > Mo > Cd. It is clear that spatial variability in PTE concentrations for atmospheric deposition near IAREEM areas is minimal (shown in Table 5). This is probably because elements dominated by natural sources typically exhibit low coefficients of variation, while those influenced by anthropogenic sources have higher coefficients [37; 38]. In this study area, most atmospherically deposited PTEs show low spatial variability. Notably, the coefficients of variation \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Parameters**} & \multirow{2}{*}{**Description**} & \multirow{2}{*}{**Units**} & \multicolumn{4}{c}{**Values**} \\ \cline{3-6}  & & & **Adult** & **Child** & **Reference** \\  & & & **O-18 Years Old)** & & **(1–6 Years Old)** & \\ \hline C\({}_{i}\) & Concentration of PTE & mg/kg & & & & Site-specific \\ IR & Intake ratio & mg/day & 100 & 200 & USDOE (2011) \\ EF & Exposure frequency & day/year & 180 & 180 & [33] \\ ED & Exposure duration & year & 24 & 6 & [31] \\ BW & Body weight & kg & 70 & 15 & [31] \\ AT & Average time & day & 365 \(\times\) ED (non-carcinogen) & \(//\) 365 \(\times\) 70 (carcinogen) & [31] \\ InhR & Inhalation rate & m\({}^{3}\)/day & 20 & 7.5 & [29] \\ PM\({}_{10}\) & Inhalable particulate matter & kg/m\({}^{5}\) & 3.525 \(\times\) 10\({}^{-8}\) & 3.525 \(\times\) 10\({}^{-8}\) & [34] \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Variables with their descriptions and reference values used for health risk assessment of PTEs in atmospheric deposition. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multicolumn{1}{c}{**Element**} & **As** & **Cd** & **Cr** & **Cu** & **Mo** & **Ni** & **Pb** & **Reference** \\ \hline Relative bioavailability factor (RBA) (unitless) & 0.6 & 1 & 1 & 1 & 1 & 1 & [31] \\ \hline Oral reference dose (RID\({}_{\text{o}}\)) (mg kg\({}^{-1}\) day\({}^{-1}\)) & 0.0003 & 0.001 & 0.003 & 0.04 & 0.005 & 0.02 & 0.0014 & [32] \\ \hline Inhalation reference concentration (RFC) (mg m\({}^{-3}\)) & 0.000015 & 0.00001 & 0.0001 & 0.04 & 0.002 & 0.00009 & 0.035 & [32] \\ \hline Oral slope factor (CSF\({}_{\text{o}}\)) (mg kg\({}^{-1}\) day\({}^{-1}\))\({}^{-1}\) & 1.5 & & 0.5 & & & & 0.0085 & [32] \\ \hline Inhalation unit risk (IUR) (ug m\({}^{-3}\))\({}^{-1}\) & 0.0043 & 0.0018 & 0.084 & & & 0.0003 & & [32] \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Relative bioavailability factor, oral reference dose, oral slope factor, inhalation reference concentration, and inhalation unit risk values for each potential toxic element. for As and Pb are greater than 1, with higher concentrations at mining regions containing heavy rare earth elements in Longnan county (Figure 2), suggesting mining influences concentration of these elements. Compared to open-pit coal mining areas [40], atmospheric deposition of PTE concentrations of As are significantly higher in IAREEM areas. However, compared to the average level of PTEs in urban areas in China and the world [41; 42], the concentration of PTEs in IAREEM areas is at a relatively low level. In addition, the PTE concentrations of Pb, Cr, Cd, Ni, Cu, and As in the IAREEM areas are slightly lower compared to those in the rural areas of Shanghai and the Taihu Lake forest region in the Yangtze River Delta Economic Zone [14; 43].