Risk assessment and accumulation prediction of heavy metal pollution in arable soils of the Jianghan-Dongting interconnected river-lake plain

The soil environmental pollution of cultivated land is mainly manifested as heavy metal pollution． In this paper, Cd, Hg, As, Pb, Cr, Cu, Ni and Zn were used as evaluation factors, and the soil environmental capacity theory was used to evaluate the pollution risk of heavy metals in regional cultivated soil． By calculating the amount of heavy metals input by atmospheric deposition, chemical fertilizer application, irrigation water, livestock and poultry manure returning to the field and compound feed in the region, the accumulation prediction was carried out by using the accumulation law of dynamic environmental capacity． The results showed that the environmental risk of heavy metal compound pollution in cultivated soil in the study area was low, and the environmental capacity was sufficient． Except for a few points in the middle and high environmental risk, the overall environment was relatively safe． In terms of individual heavy metals, As and Cd have the greatest risk of pollution, and some points have environmental pollution． The risks of Hg, Pb, Cu and Zn are generally controllable, and only a few points are at medium and high risks． The risk levels of Cr and Ni are the lowest, all of which are risk-free or low risk． The annual input of heavy metals in cultivated soil in the study area was Cd 3.12g·hm⁻² Hg 0.56g·hm⁻², As 66.33g·hm⁻², Pb 254.76g·hm⁻², Cr 53.23g·hm⁻², Cu 134.17g·hm⁻², Ni 31.81g·hm⁻², and Zn 524.14g·hm⁻²． In the next 5, 10, 20, 30, 5 a and 100 a, the accumulation of heavy metals is lower than the risk base value, and the overall risk is low． The results of the cumulative spatial distribution of As and Cd in the next 5, 10, 20, 30, 50 and 100 years showed that the cumulative pollution risk of As and Cd gradually increased with the increase of years, and atmospheric deposition, irrigation water, livestock and poultry manure returning and compound feed were the main input channels．