Evaluation of methods to derive pesticide degradation parameters for regulatory modelling

Beulke, Sabine; Brown, Colin D.

doi:10.1007/s003740100364

Cited by 127 publications

(75 citation statements)

References 5 publications

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“…Since the determination coefficient R 2 has a limited value when comparing the fits of two models with different numbers of parameters, the chi-square (χ 2 ) error value test recommended by the FOCUS degradation kinetics guidance was used for model comparison (FOCUS, 2006). Only for soil 1, the two-compartment model resulted in smaller χ 2 minimum error value (at which the test is passed at the 5% significance level) than the single first-order model for both enantiomers (Table 3) The superior fitting of metalaxyl dissipation data to the two-compartment model for the clay soil (soil 1) suggests that a fraction of the added pesticide in this soil could have displayed reduced bioavailability, thus dissipating at a relatively slower degradation rate, than the more available fraction typically present in the accessible soil solution phase (Beulke and Brown, 2001). This behavior would also explain the reduced enantioselectivity of metalaxyl degradation in soil 1, because the protected, less bioavailable fraction is expected to be more racemic than the fraction readily available to enantioselective biodegradation, since it is supposed to have undergone less microbial attack (Ulrich et al, 2009;Wong et al, 2012).…”

Section: Accordingly Ef Values Ef= [S]/([s]+[r])mentioning

confidence: 99%

Environmental behavior of the enantiomers of the chiral fungicide metalaxyl in Mediterranean agricultural soils

Celis

Gámiz

Adelino

et al. 2013

Science of The Total Environment

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Improving the existing knowledge on the enantioselectivity of processes affecting chiral pesticide enantiomers in the environment is necessary to maximize the efficacy and minimize the environmental impact caused by the use of pesticides with chiral properties. In this work, the enantioselectivity of the sorption, degradation, and leaching processes of the chiral fungicide metalaxyl in three slightly alkaline, agricultural soils from southern Spain was studied. Batch sorption experiments indicated that the sorption of racemic-metalaxyl on soils, their clay (< 2 µm) fractions, and a number of model sorbents simulating naturally-occurring soil colloidal particles was non-enantioselective; the S-enantiomer was sorbed to the same extent as the R-enantiomer on all soil materials. Soil incubation experiments revealed that the R-enantiomer of metalaxyl was degraded faster than the S-enantiomer in all three soils, but the extent and enantioselectivity of metalaxyl degradation was soil-dependent, occurring more slowly and with less enantioselectivity in the fine-textured soil (soil 1) than in the coarsetextured soils (soils 2 and 3). For soils 2 and 3, S-and R-metalaxyl dissipation data were very well described by single first-order kinetics, whereas for soil 1 dissipation data were better fitted by two coupled first-order equations. It is suggested that sorption and entrapment of metalaxyl enantiomers in the abundant small-size pores of soil 1 (i.e., pore radius < 100 nm) could have resulted in a fraction of the fungicide of reduced bioavailability, and consequently, protected from enantioselective degradation. Metalaxyl leaching through soil columns was also enantioselective; the concentration of S-metalaxyl in all leachates collected was greater than that of R-metalaxyl. Despite being non-enantioselective, sorption influenced the enantioselectivity of metalaxyl leaching, as it determined the residence time of the fungicide within the soil column, and consequently, the extent and enantioselectivity of its degradation during leaching.

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Section: Accordingly Ef Values Ef= [S]/([s]+[r])mentioning

confidence: 99%

Environmental behavior of the enantiomers of the chiral fungicide metalaxyl in Mediterranean agricultural soils

Celis

Gámiz

Adelino

et al. 2013

Science of The Total Environment

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“…The first-order model however, commonly underestimates the initial rate and over-estimates the final rate 7 . This failure has been accounted for by assuming two first-order processes which appear to fit the data but have no theoretical basis 8,9 . Several hypotheses to explain these phenomena have been offered and included: reaction kinetics of an order higher than one; processes in addition to decomposition affecting the catabolism of the pesticide; sorption processes influencing the availability of the substrate for decomposition; the heterogeneity or spatial variability of the soils; the multiphase solution of herbicide formulation.…”

Section: Resultsmentioning

confidence: 99%

The effect of Atpolan 80 EC on atrazine residues in the soil

Swarcewicz

Skórska

Paździoch

2007

Polish Journal of Chemical Technology

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The persistence of atrazine residues in soils may have an effect on the contamination of the ground water or surface water. Besides the active ingredients, pesticide formulations contain many other compounds called adjuvants. One of them is the Atpolan 80 EC which belongs to the group of oil mineral adjuvants used as tank-mix. The utilization of a fraction of paraffin oil 1113 is one of the examples of utilising waste as the component of Atpolan 80 EC in agriculture. When the Atpolan concentration comprised 1.25% (v/v), the atrazine degradation rate decreased in the sandy loam and muck soil. The half-life of atrazine increased over a period of 40 or 57 days, depending on the type of the soil. The least significant effect was caused by Atpolan concentration at 0.25 and 0.75%. This result points at the capability of limiting atrazine run-off and leaching down the soil profile. Each ingredient of the pesticide, besides having the overall ability to distribute between different phases, also demonstrates some single compound behaviour. This paper shows our current understanding of the factors that influence the adjuvant performance and their potentially complex interactions with the pesticide.

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“…Typically, a fast initial degradation is followed by a gradual decrease in the degradation rate and eventually a very slow degradation. The gradual change in degradation rate may be better described by using two rate constants instead of one (Beulke & Brown, 2001;Henriksen et al, 2004;Ma et al, 2004;Sanchez et al, 2003 The fast degradation in the first compartment occurs when the pesticide is in the soil-water phase and readily available for microorganisms. In the second compartment the pesticide is sorbed to soil particles.…”

Section: Degradation Processesmentioning

confidence: 99%

“…These characteristics suggest that a single DT 50 may not be sufficient as an index of persistence. Beulke & Brown (2001) recomended using DT 90 as a risk index to indicate the persistence, where the DT 90 represents the time for 90% of the initial residues to dissipate; whereas Grover et al (1997) and Wolt (1997) used both DT 50 and DT 90 as indices of persistence.…”

Section: Degradation Processesmentioning

confidence: 99%

Behavior and Fate of Imidacloprid in Croatian Olive Orchard Soils Under Laboratory Conditions

Broznić¹,

Marinić²,

Mili³

2011

Pesticides in the Modern World - Risks and Benefits

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Evaluation of methods to derive pesticide degradation parameters for regulatory modelling

Cited by 127 publications

References 5 publications

Environmental behavior of the enantiomers of the chiral fungicide metalaxyl in Mediterranean agricultural soils

Environmental behavior of the enantiomers of the chiral fungicide metalaxyl in Mediterranean agricultural soils

The effect of Atpolan 80 EC on atrazine residues in the soil

Behavior and Fate of Imidacloprid in Croatian Olive Orchard Soils Under Laboratory Conditions

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