Distribution characteristics and risk analysis of heavy metals in pesticides

In order to find out the distribution characteristics of heavy metals in pesticides and the cumulative risk of heavy metals in soil and vegetables after pesticide application, 54 commonly used pesticide formulations were collected from the market, and the field experiments were conducted to investigate the contents of heavy metals in different pesticide formulations and their safety risks after application. The results showed that heavy metal was common in pesticide formulations, and the average contents of Cr, As, Cd, Hg and Pb were 21.2, 3.23, 0.78, 0.85 and 3.43 mg/kg, respectively. The average contents of Cu and Zn in non Cu/Zn pesticides were 9.22 and 18.1 mg/kg, respectively. Three to seven heavy metals were detected in each pesticide. Relatively high content of Zn was detected in pesticide formulations containing Cu, while high contents of Cu and Cd were detected in Zn-containing pesticides. The results of correlation analysis showed that the contents of Zn-Cd, Cr-Pb-As and Hg-As in pesticide formulations were significantly correlated and their sources were homologous. In the year of pesticide use, the contents of heavy metals in soil increased by 5.74 × 10⁻⁸ mg/kg to 5.46 × 10⁻⁵ mg/kg. Compared to the application of other types of pesticides, the increment of Cr, As and Hg in soil was significantly higher after the application of insecticides, and the increment of Cu, Zn and Cd in soil was significantly higher after the application of fungicides. Nevertheless, according to the soil environmental quality standard in the National Standard of China (GB15618—2018), the annual accumulation of heavy metals in soil caused by pesticides application was negligible. In comparison with the blank control that no pesticide was sprayed, the application of thiosen copper for 5 times significantly increased the content of Pb in cabbage, and the application of propineb for 3 and 5 times significantly increased the content of Cd in cabbage, but neither Cd nor Pb exceeded the national limit. The maximum contents of Cd and Pb in cabbage were about 20% and 10% of the national limit value, respectively, suggesting that the risk was low.