title: Remediation of fungicide residues on fresh produce by use of gaseous ozone.
abstract: Ozone fumigation was explored as a means for degrading organic fungicide residues on fresh produce. Fungicides sorbed onto model abiotic glass surfaces or onto grape berries were fumigated separately in a flow-through chamber. Gaseous ozone at a constant concentration of 150 ± 10 ppmv (μL·L(-1)) selectively oxidized fungicides sorbed to model surfaces. Over 140 min, boscalid and iprodione levels did not change significantly based on a single-factor analysis of variance (ANOVA) at the 95% level of confidence (p = 0.05); however, pseudo-first-order losses resulted in observable rate constants of ozonolysis, k(ozonolysis) (min(-1)), of 0.0233 ± 0.0029 (t(1/2) ≈ 29.7 min), 0.0168 ± 0.0028 (t(1/2) ≈ 41.3 min), and 0.0127 ± 0.0010 (t(1/2) ≈ 54.6 min) for fenhexamid, cyprodinil, and pyrimethanil, respectively. The relative degradation of fungicides on berries at gaseous ozone concentrations of 900 ± 12 ppmv (μL·L(-1)) over 2 h was similar to that on glass; decreases in residue concentration were observed for only fenhexamid (∼ 64%), cyprodinil (∼ 38%), and pyrimethanil (∼ 35%) with corresponding k(ozonolysis) (min(-1)) of 0.0085 ± 0.0021 (t(1/2) ≈ 81.5 min), 0.0039 ± 0.0008 (t(1/2) ≈ 177.7 min), and 0.0036 ± 0.0007 (t(1/2) ≈ 192.5 min). Heterogeneous rate constants of gaseous ozone reacting with a sorbed fungicide, k(O(3)) (M(-1)·min(-1)), were calculated for both surfaces and indicate losses proceed ∼ 15-fold slower on grapes. The kinetics and mechanism of fungicide removal, supported by gas chromatography- and liquid chromatography-mass spectrometry product analyses, is discussed in the context of facilitating compliance with maximum residue level (MRL) tolerances for fresh produce.
authors.affiliation: Agricultural Research Service, United States Department of Agriculture, 9611 South Riverbend Avenue, Parlier, California 93648, USA. spencer.walse@ars.usda.gov
authors.forename: Spencer S
authors.initials: SS
authors.lastname: Walse
authors.forename: Hakan
authors.initials: H
authors.lastname: Karaca
mesh_terms: D002140:California; D052918:Environmental Restoration and Remediation; D005651:Fumigation; D005659:Fungicides, Industrial / Q000737:chemistry / Q000302:isolation & purification*; D008401:Gas Chromatography-Mass Spectrometry; D005898:Glass / Q000737:chemistry; D007700:Kinetics; D008970:Molecular Weight; D016877:Oxidants / Q000737:chemistry; D010126:Ozone / Q000737:chemistry*; D010573:Pesticide Residues / Q000737:chemistry / Q000302:isolation & purification*; D011743:Pyrimidines / Q000737:chemistry / Q000302:isolation & purification; D027843:Vitis / Q000737:chemistry*
chemical_list: D005659:Fungicides, Industrial; D016877:Oxidants; D010573:Pesticide Residues; D011743:Pyrimidines; C108338:cyprodinil; D010126:Ozone; C108337:pyrimethanil