Ecodynamics of metals and metalloids in Pyrenean lakes in relation to climate change and anthropogenic pressure.

Abstract

The Pyrenean high mountain lakes are iconic elements of the landscape and the history ofthe territory. Their management and conservation, within the current context of climatechange and increasing anthropogenic pressure, requires detailed knowledge of the bioticand abiotic processes running on them. This work has been carried out in the framework ofa European project (REPLIM) that aims to investigate the past, present and future of lakesand peatbogs in the Pyrenees in a general context of global change. The thesis is the resultof a collaboration between the UPV/EHU and the UPPA through a joint call to finance PhDThesis in co-tutelage. Five sampling campaigns were carried out in 2017-2019 in more than20 alpine lakes located in the Central Pyrenees. The collection and analysis of sub-surfaceand deep-water samples allowed us to study the occurrence, geographical distribution,depth profiles and seasonal trends of a large array of chemical and physical parameters.Specifically, the fate of Potentially Harmful Trace Elements, the biogeochemistry of mercuryspecies and the cycle of inorganic carbon were investigated in detail. In addition, a newanalytical procedure based on the use of graphene nanoparticles for the measurement ofmercury in natural waters was also proposed. Finally, two sediment cores from thePyrenean lakes Marboré and Estanya were analysed to investigate mercury cyclingprocesses in them using Hg stable isotopic signature as a tracer.