title: The impact of soil organic matter and soil sterilisation on the bioaccessibility of 14C-azoxystrobin determined by desorption kinetics.
abstract: As soils represent a major sink for most pesticides, factors influencing pesticide degradation are essential in identifying their potential environmental risk. Desorption of (14)C-azoxystrobin was investigated over time in two soils under sterile and non-sterile conditions using exhaustive (solvent) and non-exhaustive (aqueous) methods. Desorption data were fitted to a two-compartment model, differentiating between fast and slow desorbing fractions. With increased ageing, rapid desorption (Frap) (bioaccessibility) decreased with corresponding increases in slowly desorbing fractions (F(slow)). The rapid desorption rate constant (k(fast)) was not affected by ageing, sterility or extraction solvent. The non-exhaustive extractions had similar desorption profiles; whereas exhaustive extractions in aged soils had the highest F(rap). In non-sterile soil, F(rap) was lower resulting in higher F(slow), while desorption rates remained unaffected. Organic matter (OM) reduces F(rap); but not desorption rates. Microorganisms and OM enhanced ageing effects, reducing the fraction of fast desorbing chemicals and potentially the bioaccessibility of pesticides in soil.
authors.affiliation: Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK.
authors.forename: Helen
authors.initials: H
authors.lastname: Clegg
authors.affiliation: Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Riding
authors.affiliation: Syngenta, Jealotts Hill Research Station, Bracknell RG42 6ET, UK.
authors.forename: Robin
authors.initials: R
authors.lastname: Oliver
authors.affiliation: Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK.
authors.forename: Kevin C
authors.initials: KC
authors.lastname: Jones
authors.affiliation: Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK. Electronic address: k.semple@lancaster.ac.uk.
authors.forename: Kirk T
authors.initials: KT
authors.lastname: Semple
mesh_terms: D000327:Adsorption; D001673:Biodegradation, Environmental; D005659:Fungicides, Industrial / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D008689:Methacrylates / Q000737:chemistry* / Q000378:metabolism; D011743:Pyrimidines / Q000737:chemistry* / Q000378:metabolism; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000737:chemistry* / Q000378:metabolism; D013242:Sterilization; D000073739:Strobilurins
chemical_list: D005659:Fungicides, Industrial; D008689:Methacrylates; D011743:Pyrimidines; D012987:Soil; D012989:Soil Pollutants; D000073739:Strobilurins; C087670:azoxystrobin
keywords: Azoxystrobin; Bioaccessibility; Desorption kinetics; Organic matter; Soil