where Q (mg kg1 year1) is the net flux through the topsoil in one year; Qatmos, Qirrig, and Qferti (mg kg1 year1) are the inflow fluxes via atmospheric precipitation, irrigation water, and fertilization,respectively; Qharv and Qleac are the outflow fluxes via harvesting and water leaching, respectively; qferti (kg m2 year1) is the usage amount per unit area of all fertilizers, and Cferti (mg kg1) is the heavy metal concentration in fertilizer; Yj (kg m2 year1
) is the yield per unit area of grains and rape seeds (j); Csoil (mg kg1) is the heavy metal concentration in the topsoil, and the BCFj (dimensionless unit) is the bioconcentration factor of the heavy metal in grains and rape seeds; r (kg m3) is the soil bulk density and L (m) is
the depth of topsoil; Qleac and Qleac,per (mg kg1 year1) are the outflow flux of heavy metal via leaching in this study and previous study, respectively; the Ctotal and Ctotal,per (mg kg1) are the total concentration of heavy metal in the soil in this study and previous study,respectively; the b1 and b2 is the Freundlich parameter derived from pH in this study and previous study. The values of these parameters, formulas and leaching flux calculation are detailed in the SI