title: Gross Nitrogen Mineralization in Surface Sediments of the Yangtze Estuary.
abstract: Nitrogen mineralization is a key biogeochemical process transforming organic nitrogen to inorganic nitrogen in estuarine and coastal sediments. Although sedimentary nitrogen mineralization is an important internal driver for aquatic eutrophication, few studies have investigated sedimentary nitrogen mineralization in these environments. Sediment-slurry incubation experiments combined with 15N isotope dilution technique were conducted to quantify the potential rates of nitrogen mineralization in surface sediments of the Yangtze Estuary. The gross nitrogen mineralization (GNM) rates ranged from 0.02 to 5.13 mg N kg(-1) d(-1) in surface sediments of the study area. The GNM rates were generally higher in summer than in winter, and the relative high rates were detected mainly at sites near the north branch and frontal edge of this estuary. The spatial and temporal distributions of GNM rates were observed to depend largely on temperature, salinity, sedimentary organic carbon and nitrogen contents, and extracellular enzyme (urease and L-glutaminase) activities. The total mineralized nitrogen in the sediments of the Yangtze Estuary was estimated to be about 6.17 × 10(5) t N yr(-1), and approximately 37% of it was retained in the estuary. Assuming the retained mineralized nitrogen is totally released from the sediments into the water column, which contributed 12-15% of total dissolved inorganic nitrogen (DIN) sources in this study area. This result indicated that the mineralization process is a significant internal nitrogen source for the overlying water of the Yangtze Estuary, and thus may contribute to the estuarine and coastal eutrophication.
authors.affiliation: College of Geographical Sciences, East China Normal University, 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, Shanghai 200062, China.
authors.forename: Lijun
authors.initials: L
authors.lastname: Hou
authors.affiliation: College of Geographical Sciences, East China Normal University, Shanghai 200241, China.
authors.forename: Min
authors.initials: M
authors.lastname: Liu
authors.affiliation: College of Geographical Sciences, East China Normal University, Shanghai 200241, China.
authors.forename: Xiaofei
authors.initials: X
authors.lastname: Li
authors.affiliation: College of Geographical Sciences, East China Normal University, Shanghai 200241, China.
authors.forename: Guoyu
authors.initials: G
authors.lastname: Yin
authors.affiliation: College of Geographical Sciences, East China Normal University, Shanghai 200241, China.
authors.forename: Yanling
authors.initials: Y
authors.lastname: Zheng
authors.affiliation: State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, China.
authors.forename: Fengyu
authors.initials: F
authors.lastname: Deng
mesh_terms: D002681:China; D004784:Environmental Monitoring; D063366:Estuaries; D005308:Fertilizers; D019015:Geologic Sediments / Q000737:chemistry*; D009584:Nitrogen / Q000032:analysis* / Q000737:chemistry; D045483:Rivers / Q000737:chemistry*; D014873:Water Pollutants / Q000032:analysis / Q000737:chemistry
chemical_list: D005308:Fertilizers; D014873:Water Pollutants; D009584:Nitrogen