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Ecotoxicology and Human Environmental Health
Toxicity of three crystalline TiO2 nanoparticles in activated sludge: Bacterial cell death modes differentially weaken sludge dewaterability Kun Li, Jin Qian, Peifang Wang, Chao Wang, Xiulei Fan, Bianhe Lu, Xin Tian, Wen Jin, Xixian He, and Wenzhou Guo Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.8b04991 • Publication Date (Web): 19 Mar 2019 Downloaded from http://pubs.acs.org on March 21, 2019
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Environmental Science & Technology
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Toxicity of three crystalline TiO 2 nanoparticles in activated sludge: Bacterial
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cell death modes differentially weaken sludge dewaterability
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Kun Lia,b, Jin Qiana,b* , Peifang Wanga,b* , Chao Wanga,b, Xiulei Fana,b, Bianhe Lua,b, Xin Tiana,b,
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Wen Jina,b, Xixian Hea,b, Wenzhou Guoc
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a
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Ministry of Education, Hohai University, Nanjing, People’s Republic of China, 210098
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b
College of Environment, Hohai University, Nanjing, People’s Republic of China, 210098
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c
College of Science, Hohai University, Nanjing, People’s Republic of China, 210098
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*Corresponding authors:
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Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes,
Jin Qian, phone: 86-25-8378-7332; fax: 86-25-8378-7332; E-mail:
[email protected] Peifang Wang, phone: 86-25-8378-7930; fax: 86-25-8378-7930; E-mail:
[email protected] 14 15
KEYWORDS: bacterial apoptosis, crystalline phase, extracellular polymeric substance, flow
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cytometry, sludge dewatering, TiO 2 nanoparticles
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ACS Paragon Plus Environment
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Environmental Science & Technology
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ABSTRACT: The eco-toxicities of different crystalline phases of TiO 2 -NPs are controversial
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and the effects and mechanisms on activated sludge are unclear. Therefore, w e assessed the
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acute-toxicities (8-h exposure) of P25, anatase, and rutile TiO 2 -NPs in activated sludge using
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flow cytometry under simulated sunlight (hereafter-sun) and evaluated the relationship between
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sludge dewatering and bacterial cell death modes using Pearson’s correlation coefficients (r).
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Additionally, response of microbial community structure was examined by high throughput
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sequencing. Bacterial survival and death were observed by confocal laser scanning microscopy.
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Toxicity indicators (e.g. lactate dehydrogenase (LDH) and reactive oxygen species (ROS)) were
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determined. Overall, TiO 2 -NPs toxicity was concentration-dependent and crystalline-phase-
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dependent. The responses of bacterial communities to crystalline phases were more obvious than
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that of dosage. P25-sun and anatase-sun caused necrosis-like cell death via strong photo-
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oxidation confirmed by 131%/123% (1mg/L) and 301%/254% (50mg/L) LDH released by
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control, while rutile-sun induced apoptosis- like death via intracellular ROS production increased
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to 165% (1mg/L) and 420% (50mg/L) of control. P25 and anatase NPs had higher protein and
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polysaccharide affinities, while rutile NPs exhibited stronger attachment onto phospholipids.
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TiO2 -NPs-sun reduced activated sludge dewaterability. Specific resistance to filtration (SRF)
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showed the strongest positive correlation with tightly bound extracellular-polymeric-substances
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(EPS) and total soluble microbial by-products (r=0.974, p
