Preliminary Evidence that Copper and Zinc Inhibits the Dissipation of Synthetic Pyrethroid in Red Soil
2010
Gu, Xiao-zhi | Zhang, Lei | Zhang, Gang-ya | Fan, Cheng-xin | Chen, Li
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).
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