title: Transformation of metamitron in water-sediment systems: Detailed insight into the biodegradation processes.
abstract: Metamitron and its main metabolite desamino-metamitron are frequently detected in surface waters. To date, there are no studies targeting metamitron degradation in water-sediment systems. Therefore, the aim of this study was to trace the fate of metamitron in a water-sediment system using13C-isotope labeling. Mineralization of metamitron was high and accounted for 49% of13C6-metamitron equivalents at the end. In contrast, only 8.7% of13C6-metamitron equivalents were mineralized in the water only system demonstrating the key role of sediment for biodegradation. Metamitron disappeared from the water on day 40 and was completely removed from the sediment on day 80. This agrochemical was utilized as carbon source by microorganisms as shown by the incorporation of the13C label into microbial amino acids and finally into biogenic residues. The latter amounted to 24% of13C6-metamitron equivalents at the end. However, 17% of13C6-metamitron equivalents were detected in xenobiotic non-extractable residues (NER) with a release potential and delayed risk for the environment. Metamitron was degraded via two pathways, initially via 4-(dimethylimino)-3-methyl-6-phenyl-1,2,4-triazin-5(4H)-one, which might be related to growth, and later via desamino-metamitron, which can be attributed to starvation.
authors.affiliation: Helmholtz-Centre for Environmental Research - UFZ, Department of Environmental Biotechnology, Permoserstr, 15, 04318 Leipzig, Germany; School of Water Resources and Environment, China University of Geosciences, Beijing, Beijing 100083, PR China.
authors.forename: Shizong
authors.initials: S
authors.lastname: Wang
authors.affiliation: Helmholtz-Centre for Environmental Research - UFZ, Department of Environmental Biotechnology, Permoserstr, 15, 04318 Leipzig, Germany.
authors.forename: Anja
authors.initials: A
authors.lastname: Miltner
authors.affiliation: Helmholtz-Centre for Environmental Research - UFZ, Department of Environmental Biotechnology, Permoserstr, 15, 04318 Leipzig, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Kästner
authors.affiliation: RWTH Aachen University, Institute for Environmental Research, Worringerweg 1, 52074 Aachen, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Schäffer
authors.affiliation: Helmholtz-Centre for Environmental Research - UFZ, Department of Environmental Biotechnology, Permoserstr, 15, 04318 Leipzig, Germany; RWTH Aachen University, Institute for Environmental Research, Worringerweg 1, 52074 Aachen, Germany. Electronic address: karolina.nowak@ufz.de.
authors.forename: Karolina M
authors.initials: KM
authors.lastname: Nowak
mesh_terms: D001673:Biodegradation, Environmental; D002247:Carbon Isotopes / Q000032:analysis; D019015:Geologic Sediments / Q000737:chemistry*; D006540:Herbicides / Q000032:analysis*; D014227:Triazines / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D002247:Carbon Isotopes; D006540:Herbicides; D014227:Triazines; D014874:Water Pollutants, Chemical; C047758:metamitron
keywords: (13)C(6)-metamitron; Biodegradation pathways; Biogenic residues; Mass balance; Metabolites; Water-sediment