Criterion selection in assessment of soil heavy metal pollution in farmland on county scale

To improve the scientific validity and accuracy of regional risk assessment of soil heavy metal pollution, a county with high grain yield along Taihu Lake was chosen as a research site to assess the risks of pollution associated with five heavy metals: As, Hg, Cr, Cd, and Pb. Pollution risks were assessed according to two sets of criteria as stipulated by a national regulation (GB15618-2018) and Regional Soil Environment Load Capacity, respectively. Results show that while the two sets of criteria produce converging assessments for the region as a whole, there were considerable differences across different types of heavy metals. In contrast to the One Size Fits All model that relied exclusively on concentration criteria, the Soil Environment Load Capacity's approach, which relied on dual interface criteria to control the total stock of pollution, could more accurately capture changes in the accumulation of external-source pollution within certain ranges of temporal and spatial dimensions. To improve the accuracy of regional farmland soil heavy metal pollution assessment, it is recommended that Soil Environment Load Capacity assessment be introduced as a valuable complement to assessment based on general national criteria. This would provide a source of reference for determining soil pollution responsible parties and for drawing risk control zones at the county and township levels. © 2019, Editorial Board of China Environmental Science. All right reserved.