Scientific guidance on soil phototransformation products in groundwater – consideration, parameterisation and simulation in the exposure assessment of plant protection products

Egsmose, Mark; Fait, Gabriella; Janzen, Wolfgang; Jentzsch, Franziska; Lava, Roberto; Lythgo, Christopher; Padovani, Laura; Pickl, Christina; Priegnitz, Jan

doi:10.2903/j.efsa.2022.7119

Cited by 4 publications

(1 citation statement)

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“…This is even more important considering EFSA's new guidance on soil phototransformation products in groundwater [17], relating to photo transformation products observed in a laboratory soil photolyis in relevant amounts and which have to be considered in the lower tier approach of the groundwater exposure assessment. Currently, laboratory soil photolysis studies are designed as route studies in order to get information about the transformation process and products.…”

Section: Discussionmentioning

confidence: 99%

Development of a new test design to investigate the degradation of pesticides in soil under sunlight conditions

Hassink,

Buda,

Nellen

et al. 2023

Preprint

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Pesticides applied to soil surface are subject to photodegradation if the parent molecule is sensitive to UV-light absorption. Photodegradation studies are therefore mandatory for the registration of plant protection products to provide data on the degradation rate and on the nature of photo-products formed. In general, sunlight is simulated in these studies with xenon lamps, e.g. a Suntest® device. Surface application on very thin soil layers followed by direct irradiation is common practice, but the control of the boundary conditions, i.e. soil temperature and humidity, to maintain the structure and viability of the soil is challenging. A homogeneous and stable soil microclimate is crucial to compare the degradation data of the test item from the irradiated soil samples to the dark controls as well as to the results from the aerobic soil metabolism study. After trying different scale-up test systems with the herbicide Imazamox as comparative test item, a new soil photolysis test system was developed which is managable in the laboratory and enables a more favourable management of the boundary conditions, especially with regard to the soil water and temperature. For this, the solar simulator SolarConstant® 1200, equipped with metal halide lamps Radium HRI-TS 1000W/D/S/PRO, was installed by Atlas Ametek (Germany) in a temperature controllable walk-in incubation chamber with aluminium racks and reflectors to minimize diffuse light and to maintain a homogenous temperature of 22(± 1)°C within the irradiated soil. Borosilicate glass vessels with an inner diameter of 10 cm and a max. height of 9 cm were used. Each vessel has two adapters flanged in opposite direction for incoming air and as output for trapping volatile degradation products. Soil with a soil humidity corresponding to pF 2.0-2.5 was filled into each vessel to a height of 4 cm and a surface area to 78 cm2. Each vessel was covered by a quartz glass cover. Only negligible adjustments of the soil water content were needed, if any, compared to daily water adjustments for thin soil layers incubated under a Suntest®. Since the horizontal and vertical capillarity of the soil water is more realistic than in the thin soil layers used in the Suntest® and drying-wetting cycles are eliminated, the soil structure and microbial-induced soil processes are maintained.

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Section: Discussionmentioning

confidence: 99%