title: Interpretation of anthropogenic impacts (agriculture and urbanization) on tropical deltaic river network through the spatio-temporal variation of stable (N, O) isotopes of NO(-)3.
abstract: For the first time, the dual isotope approach was applied to trace the sources of impacts and to identify the governing biogeochemical processes in a river network in the tropical deltaic region of the Red River (Vietnam). Our long term surveys concluded that water in this river network was severely impacted by anthropogenic activities. Analysis has shown strong spatio-temporal variation of nitrate isotopes; ranges of δ(15)N-[Formula: see text] and δ(18)O-[Formula: see text] were from -5 to 15 ‰ and from -10 to 10 ‰, respectively. Average values of δ(15)N-[Formula: see text] and δ(18)O-[Formula: see text] in the dry season, when fertilizer is applied, were 3.54 and 3.15 ‰, respectively. In the rainy season, the values changed to 6.41 and -2.23 ‰, respectively. Denitrification and biological assimilation were active throughout the year, but were especially enhanced during fertilization time. Mineralization of domestic organic matter and consequent nitrification of mineralized [Formula: see text] were the dominant processes, particularly during the rainy period.
authors.affiliation: a Faculty of Chemistry , VNU University of Science, Vietnam National University , Hanoi , Vietnam.
authors.forename: Thi Thao
authors.initials: TT
authors.lastname: Ta
authors.affiliation: a Faculty of Chemistry , VNU University of Science, Vietnam National University , Hanoi , Vietnam.
authors.forename: Si Hung
authors.initials: SH
authors.lastname: Le
authors.affiliation: b Department of analytical chemistry , Institute of Chemistry, Vietnam Academy of Science and Technology , Hanoi , Vietnam.
authors.forename: Hong Quan
authors.initials: HQ
authors.lastname: Trinh
authors.affiliation: b Department of analytical chemistry , Institute of Chemistry, Vietnam Academy of Science and Technology , Hanoi , Vietnam.
authors.forename: Thi Nguyet Minh
authors.initials: TN
authors.lastname: Luu
authors.affiliation: b Department of analytical chemistry , Institute of Chemistry, Vietnam Academy of Science and Technology , Hanoi , Vietnam.
authors.forename: Anh Duc
authors.initials: AD
authors.lastname: Trinh
mesh_terms: D000383:Agriculture; D004784:Environmental Monitoring; D005308:Fertilizers / Q000032:analysis; D009566:Nitrates / Q000032:analysis* / Q000737:chemistry; D009587:Nitrogen Isotopes / Q000032:analysis; D010103:Oxygen Isotopes / Q000032:analysis; D045483:Rivers; D012621:Seasons; D014507:Urbanization; D014744:Vietnam; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry
chemical_list: D005308:Fertilizers; D009566:Nitrates; D009587:Nitrogen Isotopes; D010103:Oxygen Isotopes; D014874:Water Pollutants, Chemical
keywords: Biological assimilation; Vietnam; denitrification; dual isotope approach; isotope fractionation; isotope hydrology; nitrification; nitrogen-15; oxygen-18