Dynamics of the dissolved organicmatter in a stream-lake systemwithin an extremely acid to neutral pH range: Agrio-Caviahue watershed

CABRERA, JUAN MANUEL; GARCIA, PATRICIA ELIZABETH; PEDROZO, FERNANDO; QUEIMALIÑOS, CLAUDIA

SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY.

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2020 vol. 234

1386-1425

The Agrio-Caviahue is a natural stream-lakesystem composed of the Upper Agrio River (UAR) -Lake Caviahue- Lower AgrioRiver (LAR). The system has a broad pH gradient from extremely acid in the hotspring to almost neutral pH only 60 km downstream the source, and varies as afunction of the distance. The aim of this study was to analyze the dynamics ofthe dissolved organic matter (DOM) of this extreme system. For that matter, anabsorbance and fluorescence-based characterization was performed on naturalwater samples and hydrophobic resin DOM extracts during different seasons innine sampling stations. Between August and December, the hydrologicalconnectivity is maximum due to precipitation and snowmelt, respectively. Duringthese months, the stream that exits the lake governs the chemicalcharacteristics downstream mainly in the period of high connectivity. Incontrast, in the dry season when the flow of LAR is minimum, the two major affluentsof this river influence its pH and DOM features, and deliver inputs of humifiedDOM from the wetlands where the tributaries are born. DOM was characterized byhaving low absorbance. The PARAFAC analysis of the fluorescent DOM (FDOM)validated three fluorescent components in the natural samples (with humic andnon humic features), two of which were also recorded in the extracts, meaningthat no additional hydrophobic components were missed under the limit ofdetection of the fluorometer. The unique features of Agrio- Caviahue DOMresemble those found in DOM from Yellowstone hot springs, both acid andalkaline.