A review of pesticide phototransformation on the leaf surface: Models, mechanism, and influencing factors

The Chemical Landscape of Leaf Surfaces and Its Interaction with the Atmosphere

“…To the best of our knowledge, leafsurface photodegradation of pesticides is the only process that has been investigated in detail (reviewed by Sleiman et al 275 and others 29,264 )�although primarily in laboratory settings using model surfaces or reconstructed cuticles. 29,275,276 Some work has also been performed on the photodegradation of PAHs and their oxidation products on and within leaf cuticles, 277−279 while other studies investigated HNO 3 /nitrate photolysis on leaves of various plants. 280,281 On the contrary, the reactivity of anthropogenic SVOCs adsorbed on leaves with other gasphase oxidants has received considerably less attention.…”

“…29,264,277−280 Formulation ingredients (e.g., surfactants) and co-occurring volatile and semivolatile metabolites can further influence surface photolysis by acting as photosensitizers or quenchers of reactive species, stabilizing radical intermediates, screening light, or a combination of these processes. 29,121,264,289 By modifying the leaf's wettability, surfactants can also influence shape, density, and crystallinity of the active ingredient's residue, with impacts on its photochemical stability. 29,288 Variation in epicuticular wax chemistry, thickness, and morphology impact photodegradation in a similar manner.…”

“…29,121,264,289 By modifying the leaf's wettability, surfactants can also influence shape, density, and crystallinity of the active ingredient's residue, with impacts on its photochemical stability. 29,288 Variation in epicuticular wax chemistry, thickness, and morphology impact photodegradation in a similar manner. 275 Wax components may act as photosensitizers or quenchers of reactive species and actively participate in reactions to form "bond residues", whereas the presence of specific microstructures modifies light transmission and water spreading.…”

“…275 Wax components may act as photosensitizers or quenchers of reactive species and actively participate in reactions to form "bond residues", whereas the presence of specific microstructures modifies light transmission and water spreading. 29,264,275 SVOC solubility in epicuticular waxes can also impact half-lives, as compounds buried within the cuticle are less susceptible to photodegradation than less lipophilic molecules sitting on its surface. 278 Despite this comprehensive set of empirical observations, the mechanistic understanding of leaf surface photolysis is still largely speculative.…”

“…Given the high number of variables, we use the term “chemical landscape” to indicate the ensemble of chemicals (molecules and particles) present on the surface of a given leaf in a specific moment of time. The complex relationships between surface properties, multiphase chemistry, and surface–air exchange are more established for urban grime − and pesticide loss on leaf and soil surfaces − but have yet to be thoroughly explored in terms of plant surfaces.…”