title: Hydrological conditions control in situ DOM retention and release along a Mediterranean river.
abstract: Uncertainties exist regarding the magnitude of in situ dissolved organic matter (DOM) processing in lotic systems. In addition, little is known about the effects of extreme hydrological events on in-stream DOM retention or release during downriver transport. This study quantified the net in-stream retention/release efficiencies (η) of dissolved organic carbon (DOC) and its humic and protein-like fluorescent fractions along a Mediterranean river during drought, baseflow and flood conditions. High performance size exclusion chromatography was used to describe the apparent size distributions of the humic and protein-like DOM moieties. A snapshot mass balance allowed estimating the η values of DOC and humic and protein-like fractions. Significant DOM net retention (η < 0) was detected during the drought condition and the protein-like fraction was more retained than the humic-like fraction and bulk DOC. In addition, small substances were more efficiently retained than larger substances. DOC retention decreased under baseflow conditions, but it remained significant. The humic and protein-like net efficiencies exhibited high variability, but the net retention were not significant. From a longitudinal perspective, the entire fluvial corridor contributed net retention of DOC and humic and protein-like moieties net retention during drought condition. In contrast, net retention/release efficiencies exhibited spatial variability during baseflow condition. The flood preferentially mobilized large size DOM molecules and the fluvial corridor behaved as a homogeneous passive DOM (η = 0) conduit. This research highlights the relevance of hydrological extreme events on the magnitude of DOM retention/release mass balance and emphasizes the need to perform measurements during these conditions to quantify the impact of fluvial corridors on DOM fate and transport.
authors.affiliation: Departament d'Ecologia, Universitat de Barcelona, Barcelona, Spain. Electronic address: abutturini@ub.edu.
authors.forename: A
authors.initials: A
authors.lastname: Butturini
authors.affiliation: Departament d'Ecologia, Universitat de Barcelona, Barcelona, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Guarch
authors.affiliation: Institute of Aquatic Ecology, Department of Environmental Sciences, University of Girona, Girona, Spain.
authors.forename: A M
authors.initials: AM
authors.lastname: Romaní
authors.affiliation: Institute of Aquatic Ecology, Department of Environmental Sciences, University of Girona, Girona, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Freixa
authors.affiliation: Water Research Institute, National Research Council of Italy (IRSA-CNR), Monterotondo, Roma, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Amalfitano
authors.affiliation: Water Research Institute, National Research Council of Italy (IRSA-CNR), Monterotondo, Roma, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Fazi
authors.affiliation: WasserCluster Lunz, Biologische Station GmbH, Lunz am See, Austria; Department of Limnology and Bio-Oceanography, University of Vienna, Austria.
authors.forename: E
authors.initials: E
authors.lastname: Ejarque
mesh_terms: D006812:Humic Substances; D062070:Hydrology; D045483:Rivers / Q000737:chemistry*
chemical_list: D006812:Humic Substances
keywords: Dissolved organic matter; Floods and droughts; Humic and protein-like moieties; Hydrological extremes; Mass balance; Mediterranean rivers; Molecular size distribution