The dissipation rates of trichlorfon and its degradation product dichlorvos in cabbage and soil
2011
Li, Wei | Ma, Yan | Li, Li | Qin, Dong-Mei | Wu, Yi-Jun
The residual levels and dissipation rate of trichlorfon, and its degradation product, dichlorvos, in cabbage crops and the soil in which these were grown, were determined by gas chromatography at two geographically distant experimental sites, one in Kunming and one in Beijing, China. Trichlorfon was applied at two dosages (900gaiha⁻¹ and 1350gaiha⁻¹). Maximum final residues of trichlorfon in soil and cabbage were 1.23mgkg⁻¹ and 1.81mgkg⁻¹ respectively at Kunming, and 0.35mgkg⁻¹ and 0.70mgkg⁻¹ respectively at Beijing. However, the final residues of dichlorvos in both cabbage and soil was only 0.04mgkg⁻¹ at Kunming, and only 0.03mgkg⁻¹, or “not detectable”, at Beijing. The mean half-life of trichlorfon in cabbage was 1.80d with a dissipation rate of 90% over 5d, while that in soil was 3.05d with a dissipation rate of 90% over 14d at one experimental site. The dissipation rates of trichlorfon and its degradation product dichlorvos at the two experimental sites were different, suggesting that degradation of these pesticides was affected by local soil characteristics and climate. When applied at both the recommended dosage and at 1.5 times this, no detectable residues of either trichlorfon or dichlorvos were found in soil or cabbage at harvest. Although trichlorfon can easily degrade into dichlorvos, which is highly toxic to humans and other animals, the observed low residual levels of dichlorvos suggest that trichlorfon is safe when applied at the recommended dosage.
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