The aim of this study was to quantitatively assess the human health risks derived from different exposure paths of heavy metals in the soil. Zhangqiu county was selected as the study area, and 425 soil samples were collected to measure the As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn contents. A descriptive statistical method was used to assess the heavy metal pollution status of the soils, and the quantitative sources for human health were then determined based on positive matrix factorization (PMF) and geo-statistical techniques. The results show that the contents of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn in the soils exceed background values, but do not exceed the risk screening values, indicating that there is slight heavy metals pollution in the soil. The sources of heavy metals in the soil can be divided into three categories. The spatial distribution of Cr and Ni is approximately the same, is similar to the spatial distribution trend of parent materials, and belongs to natural sources. Cd, Cu, and Zn are controlled by transportation. The spatial distribution is significantly affected by the location of road lines. The hot spot areas of Hg, Pb, and As correspond to the locations of the industrial park and the urban area. Industrial emissions and coal combustion increase the accumulation of Hg in the soil, and As, Pb, and Hg are classified as industrial sources. The contribution rate of industrial source is 41.85%, with transportation sources and natural sources being 33.79% and 24.36%, respectively. The non-carcinogenic and carcinogenic risks under the exposure paths of hand, breathing, and skin are within the acceptable level. For children, the sources of heavy metals with the largest carcinogenic (36.53%) and non-carcinogenic (36.01%) risks are industrial sources. However, transportation is the largest source of carcinogenic (34.98%) and non-carcinogenic (37.06%) risk for adults. Differential avoidance of heavy metal sources and exposure pathways is vital to reducing human health risks.
Keywords: geo-statistics; health risk assessment; heavy metals; positive matrix factorization (PMF); soil.