title: Mechanistic model for interpreting the toxic effects of sulfonamides on nitrification.
abstract: Antibiotics are categorized as pseudopersistent compounds because of their widespread use and continuous emission into the environment. Biological systems such as active sludge and biofilms are still the principal tools used to remove antibiotics in wastewater treatment plants (WWTPs). Consequently, it is important to determine the relationship between toxic effects in biological WWTPs and the structural characteristics of antibiotics. In the present study, toxic effects of 10 sulfonamides (SAs) on nitrification in an active sludge system were studied. The toxicity results (half-effective concentrations, EC50) indicated that the toxicity of sulfadimethoxine (SDM) is approximately 4 times as large as that of sulfadiazine (SD). Based on the toxicity mechanism and the partial least squares regression (PLS) method, an optimum quantitative structure-activity relationship (QSAR) model was developed for the test system. The mechanistic model showed that the pKa, the binding energies between SAs with dihydropteroate synthetase ( [Formula: see text] ) and the binding energies between SAs with ammonia monooxygenase ( [Formula: see text] ) are the key factors affecting the toxic effects of SAs on nitration process in active sludge system, following an order of importance of [Formula: see text] > [Formula: see text] >pKa.
authors.affiliation: College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
authors.forename: Xiangfeng
authors.initials: X
authors.lastname: Huang
authors.affiliation: College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Feng
authors.affiliation: College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China; School of Life Science, Jinggangshan University, Ji'an 343009, China.
authors.forename: Cui
authors.initials: C
authors.lastname: Hu
authors.affiliation: School of Life Science, Jinggangshan University, Ji'an 343009, China.
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Xiao
authors.affiliation: School of Life Science, Jinggangshan University, Ji'an 343009, China.
authors.forename: Daliang
authors.initials: D
authors.lastname: Yu
authors.affiliation: School of Life Science, Jinggangshan University, Ji'an 343009, China. Electronic address: zouxming_80@hotmail.com.
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Zou
mesh_terms: D000900:Anti-Bacterial Agents / Q000633:toxicity*; D008962:Models, Theoretical; D058465:Nitrification / Q000187:drug effects*; D021281:Quantitative Structure-Activity Relationship; D012722:Sewage; D013449:Sulfonamides / Q000633:toxicity*; D014865:Waste Disposal, Fluid; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D000900:Anti-Bacterial Agents; D012722:Sewage; D013449:Sulfonamides; D014874:Water Pollutants, Chemical
keywords: Active sludge; Nitrification; QSAR model; Sulfonamides; Toxicity mechanism