In South America and especially in Argentina, the behaviour of mercury (Hg) and arsenic (As) mainly in sediments remains poorly understood. The Mar Chiquita system and more particularly the Laguna del Plata with its associated Suquía River basin is used here as a case study to identify the dynamic of these two trace elements. Their distribution in space and time are studied in relation with the anthropic presence and the hydrological conditions that importantly changed in the last century.The methodology consisted first to study the spatial distribution of mercury and arsenic thanks to the analysis of water and sediments taken all along the Suquía River and Laguna del Plata. Secondly, the sampling and study of a sediment core taken in Laguna del Plata allowed to evaluate variations of Hg and As with time.The implementation of selective extractions allowed to better identify Hg and As bearing phases. The global interpretation of the results and the support of satellites images revealed the important role played by climate changes and hydrological variations in the control of mercury and arsenic behaviour within the Mar Chiquita system. The combination of these different approaches revealed that the dynamic of mercury and arsenic shows contrast behaviour. Hg concentrations are low when the climate conditions are dry and lake-level is low. They are mainly associated to sulphurs carried by the Suquía River. The augmentation in regional precipitations produced higher runoff, rise in the lake-level and an increment in Hg accumulations. In this period Hg is mainly associated to the organic matter. As instead is contributed to the lake in solution and by the influence of winds from the loessic Chaco Pampean Plain in drier periods. As is associated to reactive Fe and Mn oxyhydroxides throughout the core. High concentrations in the bottom of the core are also associated to sulphides while in the middle and upper part As concentrations are as well associated with carbonates.
| Identifer | oai:union.ndltd.org:CCSD/oai:tel.archives-ouvertes.fr:tel-00920306 |
| Date | 06 December 2013 |
| Creators | Stupar, Yohana Vanesa |
| Publisher | Université Sciences et Technologies - Bordeaux I |
| Source Sets | CCSD theses-EN-ligne, France |
| Language | English |
| Detected Language | English |
| Type | PhD thesis |
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