title: Effects of carbon amendment on in situ atrazine degradation and total microbial biomass.
abstract: This study elucidates the effects of carbon amendment on metabolic degradation of atrazine (6-chloro-N(2)-ethyl-N(4)-isopropyl-1,3,5-triazine-2,4-diamine) and total microbial biomass in soil. Degradation of (14)C-ring-labelled atrazine was monitored in laboratory incubations of soils supplemented with 0, 10, 100 and 1000 μg g(-1) sucrose concentrations. An experiment to determine the effect of carbon amendment on total microbial biomass and soil respiration was carried out with different concentrations of sucrose and non-labelled atrazine. The soils were incubated at a constant temperature and constant soil moisture at water potential of -15 kPa and a soil density of 1.3 g cm(-3). Mineralization of (14)C-ring-labelled atrazine was monitored continuously over a period of 59 d in the first experiment. The CO(2) production was monitored for 62 d in the second experiment and microbial biomass determined at the end of the incubation period. The addition of 1000 μg g(-1) sucrose reduced atrazine mineralization to 43.5% compared to 51.7% of the applied amount for the treatment without sucrose. The addition of 1000 μg g(-1) sucrose modified the transformation products to 1.08 μg g(-1) deisopropylatrazine (DIA), 0.32 μg g(-1) desethylatrazine (DEA) and 0.18 μg g(-1) deisopropyl-2-hydroxyatrazine (OH-DIA). Treatment without sucrose resulted in formation of 0.64 μg g(-1) hydroxyatrazine (HA), 0.28 μg g(-1) DIA and 0.20 μg g(-1) OH-DIA. Atrazine dealkylation was enhanced in treatments with 100 and 1000 μg g(-1) of sucrose added. HA metabolite was formed in the control (no sucrose) and in the presence of 10 μg g(-1) of sucrose, whereas DEA was only detected in treatment with 1000 μg g(-1) sucrose. Results indicate that total microbial biomass increased significantly (P < 0.001) with the addition of 1000 μg g(-1) sucrose.
authors.affiliation: Department of Pure and Applied Chemistry, Masinde Muliro University of Science and Technology, Kakamega, Kenya. anjokingugi@yahoo.com
authors.forename: Anastasiah N
authors.initials: AN
authors.lastname: Ngigi
authors.forename: Zachary M
authors.initials: ZM
authors.lastname: Getenga
authors.forename: Ulrike
authors.initials: U
authors.lastname: Dörfler
authors.forename: Hamadi I
authors.initials: HI
authors.lastname: Boga
authors.forename: Benson
authors.initials: B
authors.lastname: Kuria
authors.forename: Paul
authors.initials: P
authors.lastname: Ndalut
authors.forename: Reiner
authors.initials: R
authors.lastname: Schroll
mesh_terms: D001280:Atrazine / Q000737:chemistry* / Q000494:pharmacology; D001419:Bacteria / Q000187:drug effects* / Q000254:growth & development; D018533:Biomass; D052918:Environmental Restoration and Remediation / Q000379:methods*; D007700:Kinetics; D010575:Pesticides / Q000737:chemistry* / Q000494:pharmacology; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000737:chemistry* / Q000494:pharmacology; D013395:Sucrose / Q000032:analysis*
chemical_list: D010575:Pesticides; D012987:Soil; D012989:Soil Pollutants; D013395:Sucrose; D001280:Atrazine