title: Development of a combined isotopic and mass-balance approach to determine dissolved organic carbon sources in eutrophic reservoirs.
abstract: A combined mass-balance and stable isotope approach was set up to identify and quantify dissolved organic carbon (DOC) sources in a DOC-rich (9mgL(-1)) eutrophic reservoir located in Western France and used for drinking water supply (so-called Rophemel reservoir). The mass-balance approach consisted in measuring the flux of allochthonous DOC on a daily basis, and in comparing it with the effective (measured) DOC concentration of the reservoir. The isotopic approach consisted, for its part, in measuring the carbon isotope ratios (δ(13)C values) of both allochthonous and autochthonous DOC sources, and comparing these values with the δ(13)C values of the reservoir DOC. Results from both approaches were consistent pointing out for a DOC of 100% allochthonous origin. In particular, the δ(13)C values of the DOC recovered in the reservoir (-28.5±0.2‰; n=22) during the algal bloom season (May-September) showed no trace of an autochthonous contribution (δ(13)C in algae=-30.1±0.3‰; n=2) being indistinguishable from the δ(13)C values of allochthonous DOC from inflowing rivers (-28.6±0.1‰; n=8). These results demonstrate that eutrophication is not responsible for the high DOC concentrations observed in the Rophemel reservoir and that limiting eutrophication of this reservoir will not reduce the potential formation of disinfection by-products during water treatment. The methodology developed in this study based on a complementary isotopic and mass-balance approach provides a powerful tool, suitable to identify and quantify DOC sources in eutrophic, DOC-contaminated reservoirs.
authors.affiliation: Centre Armoricain de Recherches en Environnement, UMR CNRS 6118 - Université de Rennes I Géosciences Rennes, Campus de Beaulieu, 35042 Rennes Cedex, France. anne-catherine.pierson-wickmann@univ-rennes1.fr
authors.forename: Anne-Catherine
authors.initials: AC
authors.lastname: Pierson-Wickmann
authors.forename: Gérard
authors.initials: G
authors.lastname: Gruau
authors.forename: Emilie
authors.initials: E
authors.lastname: Jardé
authors.forename: Nicolas
authors.initials: N
authors.lastname: Gaury
authors.forename: Luc
authors.initials: L
authors.lastname: Brient
authors.forename: Marion
authors.initials: M
authors.lastname: Lengronne
authors.forename: André
authors.initials: A
authors.lastname: Crocq
authors.forename: Daniel
authors.initials: D
authors.lastname: Helle
authors.forename: Thibault
authors.initials: T
authors.lastname: Lambert
mesh_terms: D002244:Carbon / Q000032:analysis* / Q000737:chemistry; D002734:Chlorophyll / Q000032:analysis; D000077194:Chlorophyll A; D004784:Environmental Monitoring / Q000379:methods*; D005068:Eutrophication; D007554:Isotopes / Q000737:chemistry; D008970:Molecular Weight; D010839:Phytoplankton / Q000254:growth & development / Q000302:isolation & purification; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014881:Water Supply / Q000032:analysis
chemical_list: D007554:Isotopes; D014874:Water Pollutants, Chemical; D002734:Chlorophyll; D002244:Carbon; D000077194:Chlorophyll A