## 3 Results and Discussion
### Distribution Characteristics of Heavy Metals
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Sampling Area** & **Cd** & **Co** & **Cr** & **Cu** & **Mn** & **Ni** & **V** & **Pb** & **Zn** \\ \hline \multirow{5}{*}{EDZ} & Mean & 1.91 & 12.09 & 195.47 & 122.39 & 595.53 & 27.54 & 85.41 & 49.04 & 182.01 \\  & Max & 11.11 & 15.63 & 462.23 & 478.51 & 879.44 & 55.51 & 126.83 & 77.69 & 308.77 \\  & Min & 0.05 & 8.97 & 53.59 & 32.09 & 350.42 & 13.82 & 42.56 & 13.72 & 66.87 \\  & SD & 2.59 & 1.93 & 116.18 & 140.64 & 138.46 & 10.74 & 20.57 & 19.84 & 80.68 \\  & CV & 136 & 16 & 59 & 115 & 23 & 39 & 24 & 40 & 44 \\ \hline \multirow{5}{*}{OT} & Mean & 1.30 & 11.88 & 161.36 & 122.13 & 549.70 & 34.51 & 85.29 & 57.17 & 230.71 \\  & Max & 8.71 & 28.69 & 262.27 & 381.47 & 1214.71 & 75.92 & 124.29 & 204.11 & 429.98 \\  & Min & 0.01 & 8.24 & 63.85 & 53.10 & 354.93 & 18.60 & 66.14 & 17.09 & 92.20 \\  & SD & 2.00 & 4.80 & 58.54 & 97.04 & 186.99 & 14.66 & 14.76 & 40.28 & 80.23 \\  & CV & 154 & 40 & 36 & 79 & 34 & 42 & 17 & 70 & 35 \\ \hline \multirow{5}{*}{CND} & Mean & 1.24 & 14.27 & 200.85 & 124.83 & 618.09 & 42.22 & 92.71 & 38.69 & 202.98 \\  & Max & 11.25 & 46.06 & 559.05 & 832.94 & 966.42 & 222.54 & 142.11 & 169.96 & 511.56 \\  & Min & 0.06 & 8.32 & 71.42 & 18.99 & 419.12 & 13.08 & 71.10 & 11.94 & 55.26 \\  & SD & 2.61 & 8.54 & 126.90 & 188.61 & 133.39 & 50.19 & 15.08 & 34.98 & 101.19 \\  & CV & 209 & 60 & 63 & 151 & 22 & 119 & 16 & 90 & 50 \\ \hline \multirow{5}{*}{SUN} & Mean & 1.48 & 12.75 & 185.89 & 123.11 & 587.78 & 34.75 & 87.80 & 48.30 & 205.23 \\  & Max & 11.25 & 46.06 & 559.05 & 832.94 & 1214.71 & 222.54 & 142.11 & 204.11 & 511.56 \\ \cline{1-1}  & Min & 0.01 & 8.24 & 53.59 & 18.99 & 350.42 & 13.08 & 42.56 & 11.94 & 55.26 \\ \cline{1-1}  & SD & 2.44 & 5.87 & 106.37 & 146.94 & 157.43 & 31.40 & 17.36 & 33.72 & 90.15 \\ \cline{1-1}  & CV & 164 & 46 & 57 & 119 & 27 & 90 & 20 & 70 & 44 \\ \hline \multicolumn{2}{l}{Background value of soil} & 0.17 & 15.40 & 86.00 & 30.70 & 712.00 & 37.30 & 110.20 & 26.70 & 83.60 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Heavy metals contents in road dust in Yangxin County, mg\(\cdot\)kg\({}^{-1}\). CV was Cd (164%) > Cu (119%) > Ni (90%) > Pb (70%) > Cr (57%) > Co (46%) > Zn (44%) > Mn (27%) > V (20%). The CV of Cd, Cr, Cu, Ni, and Pb exceeded 50%, indicating that these elements were unevenly distributed in different pavement areas of Yangxin County, and they were considered as local pollution sources or artificial non-point pollution sources. The CV of Mn and V were 27% and 20%, and it was considered that the two metals were homogeneously distributed. The statistical analysis of heavy metal content in road dust samples in Yangxin County was carried out, and the analysis results were shown in Figure 2. Research showed that the sources of heavy metals in road dust were affected by human factors [27,41]. The spatial distribution patterns were obviously different in the study area. Generally, the high contents of Pb, Zn, and Ni coincided with metal smelling, auto parts, machinery manufacturing, and other leading industries [42]. The relatively high Cu content may be related to the development of the modern logistics industry in the region because the wear of automobile brake pads will lead to the input of copper in dust [43,44]. The copper mine in Yangxin County accounted for 25.23% of the identified reserves in Hubei Province. Therefore, the influence of natural factors, such as wind, was also one of the reasons for the enrichment of copper [45]. The high content of Cd and Cr in OT was mainly due to the impact of traffic activities. The OT was the main living area of residents [46,47]. There were many public places, such as shops, schools, and hospitals, as well as crowded people and high traffic flow, so car braking frequency was high, and car brakes, brake pads, tire wear, and other human activities will cause Cd, Cr, and Cu to fall on the ground [48,49].