Ecological and Human Health Risks of Soil Heavy Metals from Qingdao: A Rapidly Developing Megacity of Eastern China

Heavy metal pollution has received increasing attention worldwide in recent decades. However, the characterization of heavy metal elements in coastal soils has been still poorly understood. In this study, eight metal elements Cd, Cr, Cu, Hg, Ni, Pb, Zn, and As were monitored in coastal soil samples, which were collected from Qingdao on the east coast of China, in 2019. The spatial distribution, pollution level, ecological, and health risks of heavy metals were then evaluated. The experimental results indicated that >50% of the sampling sites for Cd, Pb, Zn, and Hg exceeded the reference background values. In addition, the geoaccumulation index showed that 84%, 96%, and 92% of soil sample sites for Cd, Pb, and Hg were in pollution, respectively; both Cd and Hg had potential ecological risks with 50% and 22% in mild potential ecological risk, 37% (Cd) and 6% (Hg) in moderate potential ecological risk, and <10% the serious potential ecological risk, respectively. Furthermore, the averages of hazard index for all the elements were <1 indicated that the health risks for all eight heavy metals were in low level. Finally, compared with the data of 10 years ago, the concentrations, enrichments, and ecological risks of Pb increased fastest with 17%, 150%, and 17%, respectively. This indicates that with the rapid economic growth of Qingdao, the controlling of Pb in soil should be implemented with a high priority in the near future.