Quantifying soil surface photolysis under conditions simulating water movement in the field: a new laboratory test design

Hand, Laurence H.; Nichols, Carol Mancuso; Kuet, Sui F.; Oliver, Robin G.; Harbourt, Christopher M.; El-Naggar, E.

doi:10.1002/etc.3074

Cited by 5 publications

(6 citation statements)

References 19 publications

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“…Soil moisture was maintained at 38% VWC by incubation with a hydraulically fed on demand watering system, using capillary action to replace water lost through evaporation. Full details of the experimental design are given in the study of Hand et al 25 In addition, the soil core surfaces were sprayed daily with water (approximately 0.5 mL) to simulate morning dew.…”

Section: Laboratory Soil Column/ Soil Core Studies (Tests 2-4)mentioning

confidence: 99%

The route and rate of thiamethoxam soil degradation in laboratory and outdoor incubated tests, and field studies following seed treatments or spray application

Hilton¹,

Emburey

Edwards

et al. 2018

Pest Management Science

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Soil DT values decreased with increasingly realistic tests (laboratory OECD307 to soil cores to soil cores with a light/dark cycle to field trials). The majority of the differences were associated with the soil treatment in OECD307 studies which destroys soil structure and retards the degradation rate; and from the impact on soil pore water movement in light/dark conditions. Degradation rates in the field were comparable between spray application and seed treatments. Maximum clothianidin concentrations were four-fold lower for seed treatments than for spray application in field studies. © 2018 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

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Section: Laboratory Soil Column/ Soil Core Studies (Tests 2-4)mentioning

confidence: 99%

The route and rate of thiamethoxam soil degradation in laboratory and outdoor incubated tests, and field studies following seed treatments or spray application

Hilton¹,

Emburey

Edwards

et al. 2018

Pest Management Science

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“…In the initial experiment, degradation rates were investigated in sample set 1, undisturbed soil cores in continuous darkness, at constant moisture of approximately pF 2.0; sample set 2, undisturbed soil cores in continuous darkness with a variable moisture regime to mimic rainfall and evaporation; and sample set 3, sieved soil in continuous darkness, at constant moisture of approximately pF 2.0. For sets 1 and 2 the system used was the same as detailed by Hand et al (2015). In brief, sintered glass filter funnels (Pyrex TM no.…”

Section: Methodsmentioning

confidence: 99%

The Impact of Disturbed Soil Structure on the Degradation of 2 Fungicides Under Constant and Variable Moisture

Hand

Marshall

Dougan

et al. 2021

Enviro Toxic and Chemistry

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Degradation of agrochemicals in soil is frequently faster under field conditions than in laboratory studies. Field studies are carried out on relatively undisturbed soil, whereas laboratory studies typically use sieved soil, which can have a significant impact on the physical and microbial nature of the soil and may contribute to differences in degradation between laboratory and field studies. A laboratory study was therefore conducted to determine the importance of soil structure and variable soil moisture on the degradation of 2 fungicides (azoxystrobin and paclobutrazol) that show significant differences between laboratory and field degradation rates in regulatory studies. Degradation rates were measured in undisturbed cores of a sandy clay loam soil (under constant or variable moisture contents) and in sieved soil. For azoxystrobin, degradation rates under all conditions were similar (median degradation time [DegT50] 34-37 d). However, for paclobutrazol, degradation was significantly faster in undisturbed cores (DegT50 255 d in sieved soil and 63 d in undisturbed cores). Varying the moisture content did not further enhance degradation of either fungicide. Further examination into the impact of soil structure on paclobutrazol degradation, comparing undisturbed and sieved/repacked cores, revealed that the impact of sieving could not be mitigated by repacking the soil to a realistic bulk density. Examination of fungal and bacterial community structure using automated ribosomal spacer analysis showed significant initial differences between sieved/repacked and intact soil cores, although such differences were reduced at the end of the study (70 d). The present study demonstrates that disruption of soil structure significantly impacts microbial community structure, and for some compounds this may explain the differences between laboratory and field degradation rates.

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“…The test system used for our study was as described by Hand et al (2015). In brief, undisturbed soil cores were positioned firmly into sintered glass filter funnels (Pyrex TM No 36060 coarse grade; Sigma-Aldrich) containing a 2-cm-thick layer of dry silica flour.…”

Section: Intact Soil Core Study Designmentioning

confidence: 99%

Building a Conceptual Model for the Environmental Fate of the Fungicide Benzovindiflupyr

Hand

Marshall

Kuet

2023

Enviro Toxic and Chemistry

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Degradation of the fungicide benzovindiflupyr was slow in standard regulatory laboratory studies in soil and aquatic systems, suggesting it is a persistent molecule. However, the conditions in these studies differed significantly from actual environmental conditions, particularly the exclusion of light, which prevents potential contributions from the phototrophic microorganisms that are ubiquitous in both aquatic and terrestrial environments. Higher tier laboratory studies that include a more comprehensive range of degradation processes can more accurately describe environmental fate under field conditions. Indirect aqueous photolysis studies with benzovindiflupyr showed that the photolytic half-life in natural surface water can be as short as 10 days, compared with 94 days in pure buffered water. Inclusion of a light-dark cycle in higher tier aquatic metabolism studies, to include the contribution of phototrophic organisms, reduced the total system half-life from >1 year in dark test systems to as little as 23 days. The relevance of these additional processes was confirmed in an outdoor aquatic microcosm study in which the half-life of benzovindiflupyr was 13-58 days. In laboratory soil degradation studies, the degradation rate of benzovindiflupyr was significantly faster in cores with an undisturbed surface microbiotic crust, incubated in a light-dark cycle (half-life of 35 days), than in regulatory studies with sieved soil in the dark (half-life >1 year). A radiolabeled field study validated these observations, showing residue decline with a half-life of approximately 25 days over the initial 4 weeks. Conceptual models of environmental fate based on standard regulatory studies may be incomplete, and additional higher tier laboratory studies can be valuable in elucidating degradation processes and improving the prediction of persistence under actual use conditions.

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Quantifying soil surface photolysis under conditions simulating water movement in the field: a new laboratory test design

Cited by 5 publications

References 19 publications

The route and rate of thiamethoxam soil degradation in laboratory and outdoor incubated tests, and field studies following seed treatments or spray application

The route and rate of thiamethoxam soil degradation in laboratory and outdoor incubated tests, and field studies following seed treatments or spray application

The Impact of Disturbed Soil Structure on the Degradation of 2 Fungicides Under Constant and Variable Moisture

Building a Conceptual Model for the Environmental Fate of the Fungicide Benzovindiflupyr

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