Preliminary Evidence that Copper and Zinc Inhibits the Dissipation of Synthetic Pyrethroid in Red Soil

Abstract

Extensive use of synthetic pyrethroids has resulted in concerns regarding their potential effects on human health and ecosystems. In the present study, we evaluated the influence of coexisting Cu2+, Zn2+, soil water contents (15%, 25%, 40% by weight and waterlogged) and temperature levels (15°C, 25°C, 35°C, and 45°C) on the dissipation of cypermethrin, fenvalerate and deltamethrin in red soil. To further clarify the influence of Cu2+ and Zn2+ on biological and chemical dissipation processes, serial concentrations of the synthetic pyrethroids containing Cu2+ (21.3, 50, 100, and 400 mg kg−1) and Zn2+ (35.8, 100, 250, and 500 mg kg−1) were used to spike the soil and then incubated at 25°C in the dark at 25% moisture. The results revealed a very severe inhibitory effect on the dissipation rates with increasing Cu2+ and Zn2+ levels. Conversely, there were no significant decreases in dissipation rates in response to exposure to 50 mg kg−1 Cu2+ or 100 mg kg−1 Zn2+, and the dissipation rates decreased significantly (p < 0.05) when the Cu2+ and Zn2+ concentration increased to 100 and 250 mg kg−1, respectively, which were the respective maximum field recommended rates. When compared with unsterilized batch treatments, the t 1/2 in sterilized (chemical dissipation) batch treatments increased by 1.0–4.8-fold. Additionally, there was a highly significant difference in the dissipation of pyrethroids in the 15% water content treatments and waterlogged treatments (p < 0.05). Finally, the difference in the dissipation rates at 15°C and 25°C was significant (p < 0.05).