Record of historical mercury trends in sediments from the Laguna del Plata, Córdoba, Argentina

STUPAR, Y.; SCHÄFER, J; GARCIA M.G.; SCHMIDT S; PIOVANO E; BLANC G; HUNEAU F.; LE COUSTUMER PH

Florence

Congreso; Goldschimidt2013; 2013

Geochemical Society

Mercury concentrations and main carrier phases were determined in sediments of a 120 cm core from Laguna del Plata (LP). This lake is a part of the Laguna Mar Chiquita (LMC) system as it is connected to LMC itself during water highstands. LMC is one of the largest saline lakes in the world representing a sensitive climatic indicator due to its frequent lake level variations at millennial and interdecadal scales [1], with the most recent major variations during the early 1970s and after 2004. Total mercury (HgTP) concentrations analyzed by Atomic Absorption spectrometry after sample calciantin in an O2 stream (DMA 80) varied between ~13 and ~131 µg kg-1 and reflected changes.in water and sediment supply to the LP. Selective extractions performed on the sediments using ascorbate, HCl and H2O2 revealed that in the base of the core corresponding to a low water level period, Hg is mainly associated to reactive sulfides. In contrast, in the middle and upper part of the core Hg is rather associated with sedimentary organic matter and was interpreted as reflecting Hg deposition at the watershed scale. Core dating, performed with 210Pb and 137Cs, allowed to determine that the highest Hg peak corresponds to the years 1990-1993. This was attributed to the eruption of Hudson volcano in 1991 in the southern part of the Andes Cordillera rather than anthropogenic  pollution sources