In recent years, heavy metal pollution in farmlands has become increasingly serious because of human activities such as metal smelting, sewage irrigation, and road traffic in China. A field survey was conducted to investigate characteristics of Cd, As, and Pb in soil and wheat grains and assess the health risk of grain-Cd/As/Pb to humans on the fields scale. The farmland was influenced by smelter and sewage irrigation in the attitude and by road traffic in the horizon. The results showed that in farmland soil with moderate pollution levels, Cd, As, and Pb concentrations in soil samples all exceeded the risk screening values of farmland soil (GB 15618-2018), and the exceeding rates were 100%, 100%, and 36.7% respectively; the exceeding rates of Cd and Pb concentrations in wheat grains were 76.7% and 13.3%, respectively (GB 2762-2017). Distance from smelter, river of sewage irrigation, and road had no significant effect on Cd, As, and Pb concentrations in soil but had a significant effect on Cd and As concentrations in wheat grains, with the median Cd and As concentrations of the closest group being 14.9% and 41.8%, respectively, higher than the highest group (P<0.05). The Pb concentrations in soil and wheat grains were influenced by road traffic; the median Pb concentrations of the closest group were 78.9% and 471%, respectively, higher than the highest group (P<0.05). Cd and As in wheat grains have carcinogenic risks (Ri>1×10-4), RCd > RAs, Rchildren > Radult, while Pb poses no health risks in this farmland.
Keywords: compound pollution farmland; field-scale; health risk; heavy metals; pollution characteristics; wheat.