CONICET | Buscador de Institutos y Recursos Humanos

Dissolved organic matter (DOM) is the major source of carbon in aquatic environments and may be derivedfrom allochthonous or autochthonous sources. This study presents the first DOM characterisation in streams from twocontrasting Argentinean regions (the Pampas and Patagonia). We found that dissolved organic carbon (DOC) concentrationsand absorption coefficients at 254 and 350 nm (a254 and a350) were higher in Pampean than in Patagonian streams.DOMfrom streams in both regions contained compounds with high molecular weight and highly variable a350 per DOC; ithas been suggested that this could be an indicator of lignin content. The characterisation of DOM reflects the agriculturalsignal and the effect of autochthonous sources in Pampean streams, whereas a more pristine condition with high input fromterrestrial environments was recorded in Patagonian streams. No sign of DOM photodegradation was observed in eitherregion. Fluorescence-based indices suggest a more recent input of DOM in Pampean streams, whereas a highly humifiedcomponent was recorded in Patagonian streams. The combined use of absorbance and fluorescence-based techniques wasuseful for understanding the quantity and quality of DOM in these contrasting regions in Argentina.