Source apportionment and spatial and quantitative ecological risk assessment of heavy metals in soils from a typical Chinese agricultural county

•It was the first time to investigate sources and risks of soil heavy metals completely in the study area.•Four sources of soil heavy metals in a typical agricultural county were identified mainly by PMF model.•Agricultural activities were subdivided into two types of sources for research.•The impacts of each pollution source and each metal on ecological risks were quantitatively and spatially analyzed. This study collected topsoil samples from 330 sites of Shan County, a typical Chinese agricultural county, to analyze the causes and effects of heavy metal pollution. It was found that the average contents of all heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) were lower than their screening values in China. However, average contents of As, Cd, Hg, Ni, and Zn exceeded their local background level. The enrichment factors suggested the moderate pollution of Cd and slight pollution of Hg, and they were also the two of the most toxic elements. Most importantly, a new combination of spatial analysis, ecological risk assessment and positive matrix factorization model was used to identify the sources and ecological risks of heavy metals from different sources quantitatively and spatially. The results showed that the risk contribution rates of the natural source, sewage irrigation and animal husbandry, atmospheric deposition and industrial emissions, and agricultural materials were 20.0%, 35.1%, 22.0% and 22.9%, respectively. It was worth noting that agricultural activities contributed nearly 60% of the risk. In general, a large part of the area was in moderate risk. Therefore, it was necessary to promote long-term control of major sources and take precautions.