Heavy Metal Pollution Characteristics and Risk Assessment of Soil and Rice in Farmland around the Copper-Lead-Zinc Tailing, Western Hubei Province

The food security problem caused by heavy metal pollution in farmland soil has attracted widespread attention. Objective pollution investigation and evaluation work is of great significance for the later pollution prevention and safe utilization of soil.

To fully understand the heavy metal contamination condition, ecological risk and human health risk of soil and rice in the farmland around the copper-lead-zinc tailing pond in Western Hubei Province.

50 sites of topsoil and rice were investigated systematically. ICP-MS, ICP-OES and AFS were used to determine the contents of eight heavy metals (As, Cd, Cu, Pb, Zn, Hg, Ni, Cr), as well as the pH value of the soil. The potential ecological risk index method and human health risk assessment model were used to evaluate the potential ecological risk and health risk of soil and rice.

The results indicate that: (1) The contents of As, Cd, Cu, Pb and Zn in the soil exceed the standard, with the maximum exceedance rate of Cd being 20%. Only Cd in rice exceeds the standard with the exceedance rate of 14%. (2) Correlation analysis shows that soil heavy metals have the same pollution source, and leachate leakage is a possible source of pollution. There is a positive correlation between the heavy metals in rice and the surface soil, with the strongest correlation for Cd, which may be related to the strong absorption capacity of rice for soil Cd. (3) The evaluation results of potential ecological risk index show that Cd, Pb, Zn and Cu are significantly enriched in the soil, with the Cd enrichment coefficient of 4.41. The overall ecological risk is moderate, with 6% of the sites having very strong potential ecological risk. (4) The results of the health risk assessment indicate that the total and non-total carcinogenic risks are greater than the acceptable level at almost all sites. There is an overall risk of heavy metal carcinogenicity in the soil, with As and Cd being the major contributors. The total non-carcinogenic risk for rice at almost all sites in the study area is greater than the acceptable level, with Cd being the largest contributor. The total non-carcinogenic risk for rice at all sites is within the acceptable level.

The soil and rice in the vicinity of the tailings pond have been contaminated by heavy metals, posing a certain ecological risk, and the risks to the health of the local population should be taken into account.