Hydrological conditions control in situ DOM retention and release along a Mediterranean river. (1st August 2016)

• Record Type: Journal Article
• Authors: Butturini, A.; Guarch, A.; Romaní, A.M.; Freixa, A.; Amalfitano, S.; Fazi, S.; Ejarque, E.
• Is Part Of: Water research. Volume 99(2016)
• Page Start: 33
• Page End: 45
• Publication Date: 2016-08-01
• Subjects: Mediterranean rivers -- Floods and droughts -- Hydrological extremes -- Dissolved organic matter -- Mass balance -- Humic and protein-like moieties -- Molecular size distribution; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2016.04.036
• Languages: English
• ISSNs: 0043-1354

Abstract

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. Graphical abstract: Highlights: DOM in-stream mass balances were calculated along a Mediterranean fluvial continuum. DOM mass balances were performed during drought, baseflow and flood conditions. The river significantly retained DOM under drought conditions only. Protein-like substances were more retained than humic ones. Small protein-like molecules (<1 KDa), were more retained than the larger ones.