Mass balance-based inventory of heavy metals inputs to and outputs from agricultural soils in Zhejiang Province, China

It is important to understand the status and extent of soil contamination with heavy metals to make sustainable management strategies for agricultural soils. Input and output inventory of heavy metals in agricultural soil of Zhejiang Province was systematically studied. The results showed that atmospheric deposition was responsible for 47.88% and 76.87% of the total Cr and Pb inputs, respectively. Livestock manures accounted for approximately 54–85% of the total As, Cu, and Zn inputs. Livestock manure and irrigation were the main sources of Hg, contributed 50.25% and 38.63% of the total inputs, respectively. Ni was derived mainly from atmospheric deposition (57.86%), followed by irrigation (22.69%). As for Cd, the relative contributions of atmospheric deposition, irrigation, and livestock manure were similar. Crop harvesting and leaching were found to be the dominant output pathways of the soil elements Cd, Cu, Hg, and Zn, being responsible for 74.43–83.62% of the total outputs. Surface runoff was the dominant output pathway for As, Cr, Ni, and Pb, accounting for approximately 73.36%, 46.32%, 54.16%, and 48.11% of the total outputs, respectively. According to prediction and early warning, Cd is the priority control pollutant in agricultural soil. This work will assist in developing strategies for reducing heavy metal inputs to agricultural soil and effectively targeting policies to protect soil environment from long-term heavy metal accumulation.