title: Bioremediation strategies for removal of residual atrazine in the boreal groundwater zone.
abstract: Strategies for bioremediation of atrazine, a pesticide commonly polluting groundwater in low concentrations, were studied in two boreal nonagricultural soils. Atrazine was not mineralized in soil without bioremediation treatments. In biostimulation treatment with molasses, up to 52% of atrazine was mineralized at 10 °C, even though the degradation gene copy numbers did not increase. Incubations with radioactively labeled atrazine followed by microautoradiographic analysis revealed that bioremediation strategies increased the relative proportion of active degraders from 0.3 up to 1.9% of the total bacterial count. These results indicate that atrazine degradation might not solely be facilitated by atzA/trzN-atzB genes. In combined biostimulation treatment using citrate or molasses and augmentation with Pseudomonas citronellolis ADP or Arthrobacter aurescens strain TC1, up to 76% of atrazine was mineralized at 30 °C, and the atrazine degradation gene numbers increased up to 10(7) copies g(-1) soil. Clone libraries from passive samplers in groundwater monitoring wells revealed the presence of phylogenetic groups formerly shown to include atrazine degraders, and the presence of atrazine degradation genes atzA and atzB. These results show that the mineralization of low concentrations of atrazine in the groundwater zone at low temperatures is possible by bioremediation treatments.
authors.affiliation: Finnish Environment Institute, P.O. Box 140, FI-00251, Helsinki, Finland. aura.nousiainen@ymparisto.fi.
authors.forename: Aura O
authors.initials: AO
authors.lastname: Nousiainen
authors.affiliation: Finnish Environment Institute, P.O. Box 140, FI-00251, Helsinki, Finland.
authors.forename: Katarina
authors.initials: K
authors.lastname: Björklöf
authors.affiliation: Environmental Genomics Division, National Environmental Engineering Research Institute, Nehru Marg, Nagpur, 440 020, India.
authors.forename: Sneha
authors.initials: S
authors.lastname: Sagarkar
authors.affiliation: Department of Chemistry and Bioscience, Aalborg University, Fredrik Bajers Vej 7H, 9220, Aalborg East, Denmark.
authors.forename: Jeppe Lund
authors.initials: JL
authors.lastname: Nielsen
authors.affiliation: Environmental Genomics Division, National Environmental Engineering Research Institute, Nehru Marg, Nagpur, 440 020, India.
authors.forename: Atya
authors.initials: A
authors.lastname: Kapley
authors.affiliation: Finnish Environment Institute, P.O. Box 140, FI-00251, Helsinki, Finland.
authors.forename: Kirsten S
authors.initials: KS
authors.lastname: Jørgensen
mesh_terms: D001280:Atrazine / Q000378:metabolism*; D001673:Biodegradation, Environmental; D001711:Biotransformation; D060587:Groundwater / Q000737:chemistry*; D008835:Micrococcaceae / Q000378:metabolism; D010575:Pesticides / Q000378:metabolism*; D011549:Pseudomonas / Q000378:metabolism; D012988:Soil Microbiology; D013696:Temperature; D014873:Water Pollutants / Q000378:metabolism*
chemical_list: D010575:Pesticides; D014873:Water Pollutants; D001280:Atrazine
keywords: 14C-mineralization; Atrazine degradation; Bioremediation; Microautoradiography; Quantitative PCR