title: [Preliminary results concerning summer-time denitrification in the Jiulong River Estuary].
abstract: Denitrification is an important process mitigating nitrogen (N) pollution in aquatic systems. Water samples in 13 sites throughout the Jiulong River Estuary were collected in July, 2010 in a preliminary investigation of the denitrification rate in this area. As end-products of denitrification, dissolved N2 was measured by determining N2 : Ar ratios using MIMS (HPR-40), while the concentration of nitrous oxide (N2O) dissolved in water was determined by Purge and Trap-Gas Chromatography. The results showed significant spatial variance of net increase of dissolved N2 (ranging between - 9.9 and 66.8 micromol x L(-1)) and N2O (ranging between 4.3 and 31.5 nmol x L(-1)) in the Jiulong River Estuary. The net increase of dissolved N2 and N2O declined gradually from river sites to sea sites. Dissolved N2O was supersaturated by 170%-562%. The air-water fluxes of N2 ranged between -2.9 and 53.2 mmol x (m2 x d) (-1), and N2O between 5.2 and 23.9 micromol x (m2 x d)(-1). The N2O yield shared only 0.03% - 1.2% (average 0.25%) of total N air-water flux. The results suggested that water temperature and nutrient (N and P) were the key factors influencing denitrification. The denitrification rate is controlled by nitrate level at fresh-water sites with salinity < 0.5%. However, in salty waters, net increase in N2 and N2O mainly originated from denitrification occurring upstream of the estuary, and was dominated by the salinity gradient due to tidal mixing.
authors.affiliation: Fujian Key Joint Laboratory of Coastal Ecology and Environmental Studies, Coastal and Ocean Management Institute, Xiamen University, Xiamen 361005, China. nwchen@xmu.edu.cn
authors.forename: Neng-Wang
authors.initials: NW
authors.lastname: Chen
authors.forename: Jie-Zhong
authors.initials: JZ
authors.lastname: Wu
authors.forename: Hua-Sheng
authors.initials: HS
authors.lastname: Hong
mesh_terms: D002681:China; D058440:Denitrification; D063366:Estuaries; D005618:Fresh Water / Q000032:analysis; D009584:Nitrogen / Q000032:analysis / Q000737:chemistry*; D009609:Nitrous Oxide / Q000032:analysis; D045483:Rivers; D012621:Seasons; D012623:Seawater / Q000032:analysis; D014873:Water Pollutants / Q000032:analysis*; D014876:Water Pollution / Q000517:prevention & control*
chemical_list: D014873:Water Pollutants; D009609:Nitrous Oxide; D009584:Nitrogen