Accumulation and Health Risks of Heavy Metals in the Surface Soil of Cultivated Land

Soil heavy metal pollution, especially compound pollution, has been widely concerned and studied at home and abroad. However, the analysis of heavy metal accumulation levels and their health risks in soils that have not yet reached the polluted level is relatively lacking. Nearly 20 years ago, an incident of human lead poisoning caused by heavy metals occurred in Hui County, Gansu Province, China. However, the degree of heavy metal accumulation and health risks in farmland soil in the area are still unclear. Thus, 361 surface soil samples and 86 crop samples of arable land were comprehensively and systematically collected from Hui County. The accumulation degree of heavy metals in arable land and crops was characterized by the geoaccumulation index and bioconcentration factor, respectively. The carcinogenicity and non-carcinogenicity risk were analyzed with the human health risk model put forward by the US EPA. The influencing factors of heavy metal accumulation were analyzed by the geographic detectors. The results showed that the geoaccumulation index of heavy metals in the soil of the study area was in the order of Hg>Cd>Pb>As>Cr, among which As and Cr did not accumulate, and one-third of the sampling sites had a moderate accumulation of Hg and Cd; Meanwhile, Cd and Hg were highly enriched in crops. Local residents do not have a non-carcinogenic risk when consuming a single heavy metal element through crops, but there is a non-carcinogenic risk when consuming multiple heavy metal elements. At the same time, the intake of Cd, Cr, and As had significant carcinogenic risks, as order of Cd>Cr>As, and higher in children than in adults. The spatial differentiation of heavy metal accumulation in the study area was significantly affected by factors such as DEM, average temperature and average precipitation during the sampling season, and distance from the railway. Furthermore, the interaction of topography, climate, and anthropogenic factors had a more significant effect on the spatial differentiation of heavy metal accumulation in the study area. This research could provide a scientific basis for precise prevention and control of soil heavy metal pollution and human health protection in the study area and the same situation.