title: Mineralization of soil-aged isoproturon and isoproturon metabolites by Sphingomonas sp. strain SRS2.
abstract: The aim of the study was to determine the effect of aging of the herbicide isoproturon and its metabolites monodesmethyl-isoproturon and 4-isopropyl-aniline in agricultural soil on their availability to the degrading bacterium Sphingomonas sp. strain SRS2. The 14C-ring-labeled isoproturon, monodesmethyl-isoproturon, and 4-isopropyl-aniline were added to sterilized soil and stored for 1, 49, 71, or 131 d before inoculation with strain SRS2. The availability of the compounds was estimated from the initial mineralization and the amount of 14CO2 recovered after 120 d of incubation. Aging in soil for 131 d reduced the initial mineralization of isoproturon and monodesmethyl-isoproturon and, in the case of isoproturon, also reduced the recovery of 14CO2. Initial mineralization and recovery of 14CO2 from aged 4-isopropyl-aniline were slightly reduced, but less 14CO2 was generally produced than with isoproturon or monodesmethyl-isoproturon. Thus, recovery of 14CO2 from 14C-isoproturon and 14C-monodesmethyl-isoproturon was 50.7 to 64.4% of the initially added 14C, while recovery from 14C-4-isopropyl-aniline was only 11.7 to 17.0%. Sorption measurements revealed similar Freundlich constants (K(f)) for isoproturon and monodesmethyl-isoproturon, whereas K(f) for 4-isopropyl-aniline was more than fivefold greater. The findings imply that in soil, partial degradation of isoproturon to 4-isopropyl-aniline may lead to reduced mineralization of the herbicide due to sorption of the aniline moiety.
authors.affiliation: Geological Survey of Denmark and Greenland (GEUS), Dep. of Geochemistry, Oster Voldgade 10, DK-1350 Copenhagen, Denmark.
authors.forename: Helle
authors.initials: H
authors.lastname: Johannesen
authors.forename: Sebastian R
authors.initials: SR
authors.lastname: Sørensen
authors.forename: Jens
authors.initials: J
authors.lastname: Aamand
mesh_terms: D002250:Carbon Radioisotopes; D006540:Herbicides / Q000378:metabolism*; D008782:Methylurea Compounds / Q000378:metabolism*; D010671:Phenylurea Compounds; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000378:metabolism*; D020578:Sphingomonas / Q000502:physiology*
chemical_list: D002250:Carbon Radioisotopes; D006540:Herbicides; D008782:Methylurea Compounds; D010671:Phenylurea Compounds; D012989:Soil Pollutants; C028904:isoproturon