Distribution of Heavy Metals in Agricultural Soils Near Major Roads in Medium-Sized Cities

Abstract

Due to rapid urbanization, urban lands have been expanded into existing agricultural areas. With such spatial changes, agricultural lands in the expanding cities or peri-urban areas are easily exposed to contaminants generated by anthropogenic activities such as traffic. Therefore, this study aimed to investigate heavy metal concentrations in major roadside agricultural soils by distance in medium-sized cities, Jinju and Changwon, and to identify the influence of roadside dust on metal contamination. The roadside arable soils of paddy and upland, roadside tree soil, and roadside dust were sampled. In paddy, the heavy metal concentration changes by the distance from the road were not observed because of soil puddling and waterlogging. However, in upland, Cu and Zn concentrations gradually decreased with the increased distance from the road. In roadside dust, Cu and Zn concentrations were very high, exceeding Korean guidelines, which indicates roadside dust could be a primary source of Cu and Zn contamination in agricultural soils. Moreover, the roadside tree soil, which is not disturbed by agricultural activities, showed higher heavy metal concentrations in topsoil rather than subsoil, even though the soil was newly introduced for tree planting. This implies that road dust containing the metal contaminants may accumulate in the nearby soils. Many scientists have thought that eco-friendly compost is the main reason for increasing Cu and Zn in urban agricultural soils. However, roadside dust needs to be more focused on as a principal source of contamination.