4 Conclusion
We systematically examined the accumulation, risk, source, and the relationship between available concentration and planting year of 8 HMs in typical PC soils from 16 cities of 8 provinces, China. In the current PC soils, HMs showed different degrees of accumulation characteristics, especially Cu, Zn, Pb, Cd, As exceeding rate reached 15.2, 4.5, 3.0, 27.3, and 2.3%, respectively. The SFPI of Cd suggested slight Cd contamination in the whole area, while Cu reached the slightly contaminated level only in Yunnan Province. Both the NCPI and IICQ indicated that PC soil was slightly contaminated in the whole area, while Yunnan and Henan provinces were severely affected. Cu and Zn accumulation was mainly related to frequent anthropogenic agricultural activities and showed a strong correlation with SOM. Also, available Cu and Zn showed a significant linear correlation with the planting years in PC. However, Pb and Cd were only significantly related to soil texture that could be the main source of soil-forming parent material, while their available state did not correlate with the planting years. We suggest that reasonable selection of agricultural materials and scientific planting systems in PC can be effective strategies to avoid the risk of excessive soil HMs accumulation, delay soil quality degradation, and reduce agricultural non-point source pollution to ensure healthy and efficient PC for sustained development.