Organophosphate insecticide disappearance from leaf surfaces: an alternative to first-order kinetics

Abstract

hydroxide form in water. Therefore, the following ion exchange mechanism may also be conceivable: However, this ion exchange mechanism appears to be unfavorable because the capacity of the copolymer for phenol adsorption was scarcely affected by the presence of acid, similarly to the case of adsorption of phenols on activated carbon and contrary to the cases with anion exchange resins (4).Polymeric adsorbents with no ion exchange functional group such as Amberlite XAD resins may adsorb phenol by physical adsorption. However, such a mechanism would not wholly explain the adsorption of phenol by the vinylpyridine-divinylbenzene copolymer, because the copolymer showed a remarkably higher breakthrough capacity than those observed with the nonionic resins, in spite of the fact that the vinylpyridine-divinylbenzene copolymer was in the pulverized form and the XAD resins were in the macroporous form.Further research is required to determine the mechanism of the interaction of phenol with polyvinylpyridine.

A simulation model of population dynamics of the codling moth, Cydia pomonella

“…A model of pesticide degradation which requires inputs of weather factors beyond temperature would not have been useful, because such data were not generally available for the sites where model evaluation was to be done. A practical problem with fitting the model of Stamper et al (1979) is that all measurement times are scaled by the interval from application until the first measurement was taken; this time is often expressed as "immediately after the deposit had dried" (Gratwick et aI., 1965), which is not usable in fitting the loglog model. For these reasons the simple first-order, exponential decay model was used; this model does explain most of the variation in deposit over time (Stamper et al, 1979).…”

“…A practical problem with fitting the model of Stamper et al (1979) is that all measurement times are scaled by the interval from application until the first measurement was taken; this time is often expressed as "immediately after the deposit had dried" (Gratwick et aI., 1965), which is not usable in fitting the loglog model. For these reasons the simple first-order, exponential decay model was used; this model does explain most of the variation in deposit over time (Stamper et al, 1979). Data sources and decay rate estimates for pesticides applied in the orchards used for model evaluation are given in Appendix B.…”

Estimating the Exposure of Birds and Mammals to Pesticides in Long-term Risk Assessments

“…Although many researchers assume that this disappearance is exponential and well-modelled by first order kinetics, Willis and McDowell point out that residues often decline very rapidly to begin with but that the rate of loss slows down ''so that many residues ultimately persist for longer than predicted by first order kinetics''. We should consider what effect might follow from other models of pesticide residue decline (Hamaker, 1972;Willis et al, 1985, Stamper et al, 1979.…”

Reviews of Environmental Contamination and Toxicology

“…In the foliar dissipation of pesticides, the decline curve sometimes follows a two-or three-phase kinetics, each of which consists of a single exponential decline (first order). By considering a weight of vaporization loss from plant surfaces in the early stage after application, Stamper et al (1979) analyzed crop residue data by In-In plots and statistically obtained the better relationship; R = a*(312 (R, residue; t, days after application; a, constant). Gunther (1969) demonstrated the involvement of two dissipation processes for pesticides applied to citrus fruit and found that the first faster dissipation stems from surface deposits in epicuticular waxes and the slower process from metabolism in the rind.…”