Abstract
The dissipation of deltamethrin in silt clay under subtropical climate conditions was studied. 14 C- Deltamethrin labeled at gem–dimethyl groups of cyclopropane ring was used alone in one sets of columns and in presence of chloropyrifos in the other sets and kept under field conditions for eleven months. Radioactivity was concentrated in the upper zone of the columns 0-10 cm. The total dissipation of the insecticide amounted to 31%; 52% of the applied dose in silt clay soil in absence and presence of chlorpyrifos, respectively. The soil binding capacity increased with time whereby the extractable 14 C-residues simultaneously decreased. The nature of methanolic extract of soils was determined by chromatographic analysis. Deltamethrin was the main degradation product of the extractable residues in addition to 3-phenoxybenzaldehyde, 3-phenoxybenzoic acid and 3-phenoxybenzyl alcohol.
Highlights
The persistence of pesticides in soil has both economic and environmental significance and is often used as a key parameter in pesticide risk assessment
Each column was spiked at the top of the soil column using a micro pipette with 10 mg of the diluted preparations /kg soil (1.0 μCi) of the radiochemical dissolved in 100 μl of water or acetone and two sets of columns received the above dose of 14C-deltamethrin in addition to 50 mg of pure chloropyrifos
The amount of extractable 14C-deltamethrin residues in the upper 0-5cm zone decreased from 98.5% at zero time to 94.5, 86.7 and52% after 3, 6 and 11 months, respectively
Summary
The persistence of pesticides in soil has both economic and environmental significance and is often used as a key parameter in pesticide risk assessment. Malathion, pirimifosmethyl (organophosphorus compounds), deltamethrin (a synthetic pyrethroid), diatomaceous earth (DE), had proven effective against grain insects when used alone and in combination [13,14,15] Deltamethrin[(S)α-cyano-3-phenoxybenzyl-(1R,3R)-3-(2,2-dibromo-vinyl)-2,2dimethylcyclopropane-1-carboxylate] is a synthetic α-cyano pyrethroid insecticide. This insecticide is considered to be useful insecticide due to its high insecticidal activity with low mammalian toxicity and limited soil persistence [16,17,18]. It is registered for the control of soil insects and some foliar insects on a wide range of economic crops, as well as for house hold use [23]
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