title: Effect of olive-mill waste addition to agricultural soil on the enantioselective behavior of the chiral fungicide metalaxyl.
abstract: Certain soil management practices can affect the enantioselective behavior of chiral pesticide enantiomers in agricultural soils. In this work, laboratory experiments were conducted to study the effects of olive-mill waste (OMW) addition to a Mediterranean agricultural soil on the enantioselectivity of sorption, degradation, and leaching processes of the chiral fungicide metalaxyl. Sorption-desorption isotherms indicated that the sorption of metalaxyl enantiomers by unamended and OMW-amended soil (2% w/w) was non-enantioselective and that OMW addition had little effect on the extent of sorption of metalaxyl enantiomers by the soil. Soil incubation experiments revealed that the degradation of metalaxyl in unamended soil was highly enantioselective, with R-metalaxyl being degraded faster (t1/2 = 12 days) than S-metalaxyl (t1/2 = 39 days). OMW addition to the soil increased the half-life of the biologically-active R-metalaxyl enantiomer from 12 to 28 days, and decreased the half-life of the non-active S-metalaxyl enantiomer from 39 to 33 days. Consequently, the enantioselectivity of metalaxyl degradation in the soil was greatly reduced upon OMW addition. Column leaching data were consistent with batch sorption and incubation results, showing similar retardation of S- and R-metalaxyl in unamended and OMW-amended soil and enantioselective leaching of the fungicide only in unamended soil. The results have important implications regarding the biological efficacy and environmental impact of the fungicide when applied as a mixture of enantiomers or racemate to OMW-treated soils.
authors.affiliation: Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS), CSIC, Avenida Reina Mercedes 10, P.O. Box 1052, 41080 Sevilla, Spain. bgamiz@irnase.csic.es
authors.forename: Beatriz
authors.initials: B
authors.lastname: Gámiz
authors.forename: Rafael
authors.initials: R
authors.lastname: Celis
authors.forename: M Carmen
authors.initials: MC
authors.lastname: Hermosín
authors.forename: Juan
authors.initials: J
authors.lastname: Cornejo
mesh_terms: D000042:Absorption; D000383:Agriculture; D000409:Alanine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D001673:Biodegradation, Environmental; D004777:Environment; D005308:Fertilizers; D005659:Fungicides, Industrial / Q000737:chemistry / Q000378:metabolism; D006207:Half-Life; D007220:Industrial Waste; D031658:Olea; D012987:Soil; D012989:Soil Pollutants / Q000737:chemistry / Q000378:metabolism; D013030:Spain; D013237:Stereoisomerism
chemical_list: D005308:Fertilizers; D005659:Fungicides, Industrial; D007220:Industrial Waste; D012987:Soil; D012989:Soil Pollutants; C028175:metalaxyl; D000409:Alanine
keywords: Chiral pesticides; Degradation; Environment; Leaching; Organic amendments; Sorption