Spatial characteristics analysis of the human health risk posed by heavy metals in cultivated soils is of great significance, with the potential to prevent and control soil pollution, protect human health, provide a basis for risk management, etc. In this paper, a methodological system, including a USEPA health risk assessment model, differentiation and factor detector within a geographical detector, and optimized initial model of rank-size theory, was constructed from a geographical perspective. Taking a city in Jiangsu province as the research object, we obtained the spatial differentiation and relative level of human health risk of Cr, Pb, Hg, and Cd in cultivated land by using the methodological system constructed and SPSS and ArcGIS software. The average concentrations of heavy metals (mg·kg-1) in the research area were Cr (65.207 mg·kg-1), Pb (25.486 mg·kg-1), Cd (0.238 mg·kg-1), and Hg (0.045 mg·kg-1), which were lower than the risk control standards for soil contamination of agricultural land in China. The children's non-cancer risk of Cr and Pb and the cancer risk to children and adults of Cr were 2.914385, 1.337503, 4.312679×10-6, and 8.137130×10-6, respectively, all of which exceeded the maximum acceptable limit in the research. Meanwhile, the spatial differentiation (q) of heavy metal health risk was between 0.005523 and 0.204238, which indicated that the high health risk posed by heavy metals should be paid attention to. The health risk rankings (R) of the children's non-cancer risk of Cr and Pb and the cancer risk of Cr in subregions 1, 2, 3, and 4 approached or exceeded 1, and were higher than in subregions 5, 6, and 7, for which R was lower than 0.1. The R values indicated than the high health risk is concentrated in the research region. This research has great significance in measuring the health risk of heavy metals in cultivated soil at different scales, and in forming control strategies with local conditions.
Keywords: cultivated land; geographical detector; human health risk; rank-size theory; soil heavy metals.