title: Dissimilatory nitrate reduction processes in sediments of urban river networks: Spatiotemporal variations and environmental implications.
abstract: Urbanizations have increased the loadings of reactive nitrogen in urban riverine environments. However, limited information about dissimilatory nitrate reduction processes and associated contributions to nitrogen removal is available for urban riverine environments. In this study, sediment slurry experiments were conducted with nitrogen isotope-tracing technique to investigate the potential rates of denitrification, anaerobic ammonium oxidation (anammox) and dissimilatory nitrate reduction to ammonium (DNRA) and their contributions to nitrate reduction in sediments of urban river networks, Shanghai. The potential rates of denitrification, anammox and DNRA measured in the study area ranged from 0.193 to 98.7 nmol N g-1h-1dry weight (dw), 0.0387-23.7 nmol N g-1h-1dw and 0-10.3 nmol N g-1h-1dw, respectively. Denitrification and DNRA rates were higher in summer than in winter, while anammox rates were greater in winter than in summer for most sites. Dissolved oxygen, total organic carbon, nitrate, ammonium, sulfide, Fe(II) and Fe(III) were found to have significant influence on these nitrate reduction processes. Denitrification contributed 11.5-99.5%% to total nitrate reduction, as compared to 0.343-81.6% for anammox and 0-52.3% for DNRA. It is estimated that nitrogen loss of approximately 1.33 × 105t N year-1was linked to both denitrification and anammox processes, which accounted for about 20.1% of total inorganic nitrogen transported annually into the urban river networks of Shanghai. Overall, these results show the potential importance of denitrification and anammox in nitrogen removal and provide new insight into the mechanisms of nitrogen cycles in urban riverine environments.
authors.affiliation: Key Laboratory of Geographic Information Science of the Ministry of Education, School of Geographical Sciences, East China Normal University, 500 Dongchuan Road, Shanghai, 200241, China.
authors.forename: Lv
authors.initials: L
authors.lastname: Cheng
authors.affiliation: Key Laboratory of Geographic Information Science of the Ministry of Education, School of Geographical Sciences, East China Normal University, 500 Dongchuan Road, Shanghai, 200241, China.
authors.forename: Xiaofei
authors.initials: X
authors.lastname: Li
authors.affiliation: Key Laboratory of Geographic Information Science of the Ministry of Education, School of Geographical Sciences, East China Normal University, 500 Dongchuan Road, Shanghai, 200241, China.
authors.forename: Xianbiao
authors.initials: X
authors.lastname: Lin
authors.affiliation: State Key Laboratory of Estuarine and Coastal Research, East China Normal University, 3663 North Zhongshan Road, Shanghai, 200062, China. Electronic address: ljhou@sklec.ecnu.edu.cn.
authors.forename: Lijun
authors.initials: L
authors.lastname: Hou
authors.affiliation: Key Laboratory of Geographic Information Science of the Ministry of Education, School of Geographical Sciences, East China Normal University, 500 Dongchuan Road, Shanghai, 200241, China. Electronic address: mliu@geo.ecnu.edu.cn.
authors.forename: Min
authors.initials: M
authors.lastname: Liu
authors.affiliation: Key Laboratory of Geographic Information Science of the Ministry of Education, School of Geographical Sciences, East China Normal University, 500 Dongchuan Road, Shanghai, 200241, China.
authors.forename: Ye
authors.initials: Y
authors.lastname: Li
authors.affiliation: Key Laboratory of Geographic Information Science of the Ministry of Education, School of Geographical Sciences, East China Normal University, 500 Dongchuan Road, Shanghai, 200241, China.
authors.forename: Sai
authors.initials: S
authors.lastname: Liu
authors.affiliation: Key Laboratory of Geographic Information Science of the Ministry of Education, School of Geographical Sciences, East China Normal University, 500 Dongchuan Road, Shanghai, 200241, China.
authors.forename: Xiaoting
authors.initials: X
authors.lastname: Hu
mesh_terms: D064751:Ammonium Compounds / Q000737:chemistry; D002681:China; D002947:Cities; D058440:Denitrification; D005290:Ferric Compounds; D019015:Geologic Sediments / Q000737:chemistry*; D009566:Nitrates / Q000032:analysis / Q000737:chemistry* / Q000302:isolation & purification*; D009584:Nitrogen / Q000737:chemistry / Q000302:isolation & purification; D045483:Rivers / Q000737:chemistry*
chemical_list: D064751:Ammonium Compounds; D005290:Ferric Compounds; D009566:Nitrates; D009584:Nitrogen
keywords: Anammox; DNRA; Denitrification; Environmental implications; Nitrogen pollution; River networks; Urbanization