title: Natural organic matter quantification in the waters of a semiarid freshwater wetland (Tablas de Daimiel, Spain).
abstract: Dissolved organic matter (DOM) concentrations have been measured in the waters of a semiarid freshwater wetland, the Tablas de Daimiel, Spain, when the system-characterised by variable hydroperiodicity conditions, was completely flooded (February 2011). Fluxes of DOM from the wetland soils to the overlying waters were measured by using a passive diffusion sampler (peeper). Not only dissolved organic carbon (DOC) concentrations were measured but refractory organic matter (ROM, usually known as humic substances) was also quantified using a novel voltammetric method. Fluorescence spectra were recorded to help in selecting the appropriate standard for ROM quantification, test the homogeneity of DOM in the waters and get an indication of their source. The results obtained show a 7-fold increase in measured ROM concentrations from the Gigüela River to the outlet, which points to a net exportation of ROM from the wetland and to the existence of an internal source of ROM in the system, probably diffusion from the wetland soils. This hypothesis is confirmed by the flux of ROM from the soils to the water column measured with the peeper and by the common fluorescence characteristics of column and interstitial waters. The smaller increase in DOC concentrations along the wetland, in spite of the higher DOC fluxes from soils, suggests that there is significant turnover of organic carbon (OC) in the water column. The system acts as a major carbon sink but, when flooded, exports OC as DOM.
authors.affiliation: Institute E-A. Forel, University of Geneva, 10 route de Suisse, CH-1290 Versoix, Switzerland. montserrat.filella@unige.ch
authors.forename: Montserrat
authors.initials: M
authors.lastname: Filella
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Rodríguez-Murillo
authors.forename: François
authors.initials: F
authors.lastname: Quentel
mesh_terms: D002244:Carbon / Q000032:analysis; D004784:Environmental Monitoring; D005618:Fresh Water / Q000737:chemistry*; D009930:Organic Chemicals / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis*; D053833:Wetlands
chemical_list: D009930:Organic Chemicals; D014874:Water Pollutants, Chemical; D002244:Carbon