Spatial distribution characteristic, source apportionment, and risk assessment of heavy metals in the soil of an urban riparian zone

The environmental quality of urban riparian soil has an impact on the riparian ecosystem and human health. The riparian zone of the Fen River plays an important ecological function in Taiyuan city and many residents and tourists enjoy recreational activities in Fen River Park. Therefore, environmental quality of the riparian zone is closely related to the health of residents. However, the concentrations and ecological risk of heavy metals in soils of the Fen River riparian zone is not well understood, and it is also uncertain whether heavy metals pose a potential risk to human health. So we estimated the ecological and health risks of six heavy metals to determine the status of soil quality in the riparian zone of the Fen River. The mean concentrations of cadmium (Cd), mercury (Hg), and lead (Pb) in the soil were higher than the background values in the Shanxi Province and in Chinese. For Cd and Hg, the soils were slightly to moderately polluted, but for the other heavy metals, the soils were unpolluted according to the I_geo, P_i, and E_i indexes. We therefore concluded that Cd and Hg were the priority pollutants in the study area. The top soil of the "Shrub" configuration was slightly to moderate polluted according to the P_n and RI. Transport was the main source of Pb, Hg, and zinc (Zn), while Cd mainly originated from industry, and copper (Cu) and chromium (Cr) were came from natural sources. The health risk posed by heavy metals was greater for children than for adults. The levels of Cd and Cr did not present an obvious carcinogenic risk to humans. The non-carcinogenic risk to humans was found to be negligible. The results demonstrated the need for monitoring and analysis of heavy metals in soils, and provide a scientific basis for the protection and restoration of the urban riparian ecosystems.