Source spatial distribution and risk assessment of heavy metals in Yiyuan county of Shandong province

Abstract: Mountainous and hilly regions are important part of agricultural production regions, where massive heavy metals continuously accumulate in soils due to anthropogenic inputs. Soil contamination will threaten human health when it is brought into agricultural production, so accurate assessment of soil heavy metal contamination is crucial for building high standard arable land and ensuring food safety. In this paper, Yiyuan County, Shandong Province was selected as the study area about typical mountain county. The contents of heavy metals of As, Cd, Co, Cr, Cu, Ni, Pb, Hg, Zn and Mn were determined from 427 surface soil samples (0-20 cm). The multivariate statistical analysis, including principal component analysis and one-way analysis of variance (ANOVA) analysis, and geostatistical analysis were used to evaluate the pollution characteristics on the heavy metals in soils that were affected by the natural parent materials and human activities. The results show: 1) The average contents of As, Cd, Co, Cr, Cu, Hg, Ni, Pb, Zn and Mn were 9.08, 0.15, 15.32, 73.54, 33.84, 0.04, 33.64, 34.92, 84.72 and 668.17 mg/kg, respectively, and these values were slightly higher than natural background values, but did not exceed the values of national secondary soil standard, which revealed the slight level of heavy metals enrichment that would not endanger the human health. 2) The sources of heavy metals were mainly classified into 3 categories through principal component analysis: As, Co, Cu and Mn, which belonged to PC1, originated from natural parent material and belonging to natural source; Hg, Cd, Zn and Pb, classified into PC2, mainly controlled by soil parent material and industrial and agricultural pollution; Cr and Ni were regarded as natural factor under the influence of natural parent materials. The one-way ANOVA analysis further validated the source of hazardous elements in soils. Heavy metal content was significantly different among different types of land use in this region, especially Hg, Pb and Zn values had the most obvious difference in urban construction land, and their accumulation rates were 141.3%, 74.1% and 69.4% higher than natural background values, respectively, suggesting that the land had been affected by industrial production activities. The other elements mainly belonged to natural sources and they were not significantly different among land use types. 3) The high-value areas of heavy metals with natural sources were mainly consistent with the parental material of limestone. The high-value areas of heavy metals with anthropogenic input were basically the same as the distribution of industrial areas. 4) Through the evaluation of potential ecological risk index in the study area, the index values of As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Zn were 14.42, 40.92, 6.96, 2.62, 8.63, 60.88, 1.21, 7.16, 6.87 and 1.51, respectively. The values of these elements suggested only a slight ecological risk in Yiyuan County, except Hg and Cd with moderate potential ecological risk level. risk index (RI) in Yiyuan County was 151.8, which was currently at a moderate ecological potential risk level. The multivariate statistics - geostatistical simulation analysis method established in the research effectively reveals the characteristics of the source-sink of heavy metal contamination in soils, which can be used as an important basis for assessing the status of soil pollution and is vital in controlling heavy metal pollution in soil for the mountainous and hilly areas.