INVESTIGADORES
SOTO CARDENAS Estela carolina
congresos y reuniones científicas
Título:
Mercury in a pristine Andean Patagonian catchment (Southern Volcanic Zone, Argentina): species occurrence and interaction with dissolved organic matter within a fluvial network
Autor/es:
SOTO CÁRDENAS, CAROLINA; DIEGUEZ, MARÍA DEL CARMEN; CLAUDIA, QUEIMALIÑOS; RIZZO, ANDREA; FAJON, VESNA, ; KOTNIK, JOSEN ; HORVAT, MILENA; RIBEIRO GUEVARA SERGIO
Lugar:
Rodhe Island
Reunión:
Conferencia; 13th International Conference on Mercury as a Global Pollutant; 2017
Institución organizadora:
ICMGP Executive Committee
Resumen:
The mercury (Hg) transport within watersheds is regulated by water flux and hydrological paths, and coupled with the movement of dissolved organic matter (DOM) and particulate material. In Brazo Rincón (BR), a branch of Lake Nahuel Huapi (Northwestern Patagonia, Argentina), lake biota bear high Hg levels after the precipitation season, which is apparently related to volcanic activity in combination with high seasonal precipitation in the area (3500 mm y-1). We propose that these factors together with low DOM concentrations favor high Hg levels in the aquatic biota. We examined the occurrence of different Hg species (Total Hg, THg; Methyl Hg, MeHg and dissolved gaseous Hg, DGM) in the freshwater network draining to BR, applying Cold Vapor Atomic Fluorescence Spectroscopy (CVAFS). We analyzed the effect of DOM (concentration and quality), and suspended load (SL) as factors potentially influencing Hg speciation and partitioning. DOM concentration was estimated by dissolved organic carbon [DOC] and its quality through absorbance and fluorescence parameters. Chlorophyll a (Chla) was determined in the depth profile of BR. Overall, THg ranged between 41-363 ng L-1 in streams while in BR was higher in upper (114-268 ng L-1) than in deeper (16-36 ng L-1) strata. Particulate-THg and Filtered-THg ranged between 7-67 ng L-1and 15-304 ng L-1 in streams and 0.3-77 ng L-1 and 17-202 ng L-1 in BR. Estimated Hg2+ was higher in streams (40-362 ng L-1) compared to BR (17-263 ng L-1) in which upper layers showed higher concentrations. MeHg ranged between 0.01-0.3 ng L-1 in streams, and varied between 0.01-0.16 ng L-1 in BR, with higher concentrations in the upper strata. DGM was lower in streams (0.12-1.8 ng L-1) than in the water column of BR (0.1-7 ng L-1), with higher values up to 60 m, decreasing sharply towards the bottom. In general, our results suggest that the high but variable levels of different Hg species in streams and their positive relationship with terrestrial signatures of the DOM, reflect coupled inputs from the catchment and low effect of internal processing. Conversely, in the lake, different conditions are observed in the depth profile, indicating that internal processing (autochthonous production, photo- and biodegradation) operate concomitantly on DOM and Hg species to favor the production of DGM in the illuminated upper layers and binding of Hg to biological particles (phytoplankton), as suggested by the positive relationship Hg-Chla. Interestingly, in the streams Hg was mostly bound to inorganic particles.