title: Effects of carbon nanotubes on atrazine biodegradation by Arthrobacter sp.
abstract: The environmental risks of engineered nanoparticles have attracted attention. However, little is known regarding the effects of carbon nanotubes (CNTs) on the biodegradation and persistence of organic contaminants in water. We investigated the impacts of pristine and oxidized multiwalled CNTs on the atrazine biodegradation rate and efficiency using Arthrobacter sp. At a concentration of 25mg/L, the CNTs enhanced the biodegradation rate by up to 20%; however, at a concentration of 100mg/L, the CNTs decreased the biodegradation rate by up to 50%. The stimulation effects resulted from enhanced bacterial growth and the overexpression of degradation genes. The inhibitory effects resulted from the toxicity of the CNTs at high concentrations. The differences between the two CNTs at tested concentrations were not significant. The biodegradation efficiency was not impacted by adsorption, and the pre-adsorbed atrazine on the CNTs was fully biodegraded when the CNT concentration was ≤25mg/L. This finding was consistent with the lack of observable desorption hysteresis for atrazine on the tested CNTs. Our results indicate that CNTs can enhance or inhibit biodegradation through a balance of two effects: the toxic effects on microbial activity and the effects of the changing bioavailability that result from adsorption and desorption.
authors.affiliation: College of Environmental Science and Engineering, Ministry of Education Key Laboratory of Pollution Processes and Environmental Criteria, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, Nankai University, Tianjin 300071, China. Electronic address: zhangchengdong@nankai.edu.cn.
authors.forename: Chengdong
authors.initials: C
authors.lastname: Zhang
authors.affiliation: College of Environmental Science and Engineering, Ministry of Education Key Laboratory of Pollution Processes and Environmental Criteria, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, Nankai University, Tianjin 300071, China.
authors.forename: Mingzhu
authors.initials: M
authors.lastname: Li
authors.affiliation: Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun 130021, China.
authors.forename: Xu
authors.initials: X
authors.lastname: Xu
authors.affiliation: Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun 130021, China. Electronic address: liuna@jlu.edu.cn.
authors.forename: Na
authors.initials: N
authors.lastname: Liu
mesh_terms: D000327:Adsorption; D001173:Arthrobacter / Q000187:drug effects / Q000378:metabolism*; D001280:Atrazine / Q000378:metabolism*; D001673:Biodegradation, Environmental / Q000187:drug effects; D037742:Nanotubes, Carbon / Q000633:toxicity*; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D037742:Nanotubes, Carbon; D014874:Water Pollutants, Chemical; D001280:Atrazine
keywords: Adsorption; Atrazine; Biodegradation; Carbon nanotubes