title: Degradation and enantiomeric fractionation of mecoprop in soil previously exposed to phenoxy acid herbicides - New insights for bioremediation.
abstract: Phenoxy acid-contaminated subsoils are common as a result of irregular disposal of residues and production wastes in the past. For enhancing in situ biodegradation at reducing conditions, biostimulation may be an effective option. Some phenoxy acids were marketed in racemic mixtures, and biodegradation rates may differ between enantiomers. Therefore, enantio-preferred degradation of mecoprop (MCPP) in soil was measured to get in-depth information on whether amendment with glucose (BOD equivalents as substrate for microbial growth) and nitrate (redox equivalents for oxidation) can stimulate bioremediation. The degradation processes were studied in soil sampled at different depths (3, 4.5 and 6m) at a Danish urban site with a history of phenoxy acid contamination. We observed preferential degradation of the R-enantiomer only under aerobic conditions in the soil samples from 3- and 6-m depth at environmentally relevant (nM) MCPP concentrations: enantiomer fraction (EF)<0.5. On the other hand, we observed preferential degradation of the S-enantiomer in all samples and treatments at elevated (μM) MCPP concentrations: EF>0.5. Three different microbial communities were discriminated by enantioselective degradation of MCPP: 1) aerobic microorganisms with little enantioselectivity, 2) aerobic microorganisms with R-selectivity and 3) anaerobic denitrifying organisms with S-selectivity. Glucose-amendment did not enhance MCPP degradation, while nitrate amendment enhanced the degradation of high concentrations of the herbicide.
authors.affiliation: Department of Environmental Science, Aarhus University, Frederiksborgvej 399, 4000 Roskilde, Denmark; Biology Centre, Czech Academy of Sciences, Branišovská 31, 37005, České Budějovice, Czech Republic.
authors.forename: Zuzana
authors.initials: Z
authors.lastname: Frková
authors.affiliation: Department of Environmental Science, Aarhus University, Frederiksborgvej 399, 4000 Roskilde, Denmark.
authors.forename: Anders
authors.initials: A
authors.lastname: Johansen
authors.affiliation: Department of Agroecology, Aarhus University, Blichers Allé 20, 8830 Tjele, Denmark.
authors.forename: Lis Wollesen
authors.initials: LW
authors.lastname: de Jonge
authors.affiliation: Department of Agroecology, Aarhus University, Blichers Allé 20, 8830 Tjele, Denmark.
authors.forename: Preben
authors.initials: P
authors.lastname: Olsen
authors.affiliation: Department of Environmental Science, Aarhus University, Frederiksborgvej 399, 4000 Roskilde, Denmark.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Gosewinkel
authors.affiliation: Department of Environmental Science, Aarhus University, Frederiksborgvej 399, 4000 Roskilde, Denmark. Electronic address: kb@envs.au.dk.
authors.forename: Kai
authors.initials: K
authors.lastname: Bester
mesh_terms: D008456:2-Methyl-4-chlorophenoxyacetic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D000693:Anaerobiosis; D001673:Biodegradation, Environmental; D002244:Carbon / Q000378:metabolism*; D052918:Environmental Restoration and Remediation / Q000379:methods*; D006540:Herbicides / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism*; D010084:Oxidation-Reduction; D012989:Soil Pollutants / Q000378:metabolism*
chemical_list: D006540:Herbicides; D009566:Nitrates; D012989:Soil Pollutants; D002244:Carbon; C008340:mecoprop; D008456:2-Methyl-4-chlorophenoxyacetic Acid
keywords: Biostimulation; Enantioselectivity; Herbicide biodegradation; Nitrate-reducing conditions; Phenoxy acids