Effects of Atmospheric Precipitation on Heavy Metal Accumulation and Deactivation Amendment in Wheat Around a Lead Smelter

The effects of atmospheric precipitation on heavy metal accumulation and deactivation amendment in wheat surrounding a lead smelter were studied. The total precipitation amounts of Cd, Pb, and As in an in situ test were noticeably more than their amounts in an off-site test over the entire growing period of wheat. In the same soil-wheat system, the heavy metal concentrations of wheat leaves in the off-site test were significantly lower than those in the in situ test near the lead smelter. Specifically, Cd, Pb, and As were 53.1%, 89.2%, and 85.7% less, without the amendment of the heavy metal deactivator (HMD). Meanwhile, the deactivation effect improved in the off-site test, resulting in the respective Cd, Pb, and As decreases of 6.0%, 46.3%, and 22.1% more, compared with it in the in situ test. The changes in heavy metal concentrations of wheat grains were consistent with those of wheat leaves. The concentrations of Cd and Pb in the off-site test were 10.7% and 91.0% lower than the in situ values, without the amendment of the HMD, and deactivation effect also had enhanced, with Cd and Pb decreasing by 1.3% and 9.6% more. The heavy metal concentrations of wheat leaves in the indoor pot test were significantly lower than those in the in situ test, with Cd, Pb, and As 74.4%–87.3%, 95.6%–97.0%, and 86.2%–87.4% less, respectively. After repeated leaf-washing treatment, the effect of HMD amendment was further enhanced, with Cd, Pb, and As decreasing by 30.8%, 33.6%, and 34.7%, respectively. All tests conducted indicate atmospheric precipitation is the controlling pollution source. Deactivation amendment can reduce the heavy metal concentrations of wheat leaves and grains, even in the presence of precipitation contamination, although the presence of precipitation reduces the effect of HMD amendment. Repeated leaf-washing can enhance the effect of HMD amendment and decrease the accumulation of heavy metals from atmospheric precipitation in wheat.