Microbial degradation pathways of the herbicide dichlobenil in soils with different history of dichlobenil-exposure.
This is the first detailed study of metabolite production during degradation of the herbicide 2,6-dichlorobenzonitrile (dichlobenil). Degradation of dichlobenil and three potential metabolites: 2,6-dichlorobenzamide (BAM), 2,6-dichlorobenzoic acid (2,6-DCBA) and ortho-chlorobenzamide (OBAM) was studied in soils either previously exposed or not exposed to dichlobenil using a newly developed HPLC method. Dichlobenil was degraded in all four soils; BAM and 2,6-DCBA were only degraded in soils previously exposed to dichlobenil (100% within 35-56 days and 85-100% in 56 days, respectively), and OBAM in all four soils (25-33% removal in 48 days). BAM produced from dichlobenil was either hydrolyzed to 2,6-DCBA or dechlorinated to OBAM, which was further hydrolyzed to ortho-chlorobenzoic acid. BAM was rapidly mineralized in previously exposed soils only. All potential metabolites and the finding that BAM was a dead-end metabolite of dichlobenil in soils not previously exposed to dichlobenil needs to be included in risk assessments of the use of dichlobenil.
Holtze
Maria S
MS
Department of Natural Sciences, Soil and Environmental Chemistry, Royal Veterinary and Agricultural University, Thorvaldsensvej 40, Frederiksberg C, Denmark. msh@geus.dk
Hansen
Hans Christian B
HC
Juhler
René K
RK
Sørensen
Jan
J
Aamand
Jens
J
D016573:Agrochemicals; D001673:Biodegradation, Environmental; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D006540:Herbicides / Q000737:chemistry*; D009570:Nitriles / Q000737:chemistry*; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000032:analysis* / Q000737:chemistry
D016573:Agrochemicals; D006540:Herbicides; D009570:Nitriles; D012989:Soil Pollutants; C055869:dichlobanil