title: Impact of repeated pesticide applications on the binding and release of methyl 14C-monocrotophos and U-ring labelled 14C-carbaryl to soil matrices under field conditions.
abstract: The dissipation of (O-methyl-14C) monocrotophos and U-ring labelled 14C-carbaryl was monitored for over two years in absence and presence of other insecticides using in situ soil columns. The dissipation of 14C-monocrotophos from soil treated with methomyl and carbaryl showed a faster rate of downward movement than in a control column tagged with the labelled insecticide alone. The same trend was observed in experiments with 14C-carbaryl that dissipated more readily in soil treated with non-labelled monocrotophos and methomyl. In the presence of other insecticides the percentage of bound residues was generally lower than in control experiments. The bound residues at the top of the column are released at a low rate under conditions prevailing in the field. The overall time required for dissipation of 50% of monocrotophos and carbaryl (t50) as estimated from control experiment was approximately 20 and 24 weeks, respectively. The data indicate that repeated applications of pesticides might enhance the release of 14C-bound residues.
authors.affiliation: Department of Applied Organic Chemistry, National Research Centre, Dokki, Cairo, Egypt.
authors.forename: S M A D
authors.initials: SM
authors.lastname: Zayed
authors.forename: M
authors.initials: M
authors.lastname: Farghaly
authors.forename: F
authors.initials: F
authors.lastname: Mahdy
authors.forename: S M
authors.initials: SM
authors.lastname: Soliman
mesh_terms: D012721:Carbaryl / Q000737:chemistry* / Q000378:metabolism*; D002247:Carbon Isotopes / Q000032:analysis; D008999:Monocrotophos / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism*; D010575:Pesticides; D012987:Soil / Q000032:analysis*; D012989:Soil Pollutants / Q000737:chemistry* / Q000378:metabolism*; D013997:Time Factors
chemical_list: D002247:Carbon Isotopes; D010575:Pesticides; D012987:Soil; D012989:Soil Pollutants; D008999:Monocrotophos; D012721:Carbaryl