Resumen de Remobilització dels contaminants orgànics persistents en els ecosistemes polars costaners
Persistent organic pollutants (POPs) constitute an heterogeneous group of chemical substances of great environmental relevance. Its persistence, bioaccumulation, long-range transport potential and negative effects on health and the environment have led to its study and international regulation. As a consequence, there has been a decrease in the primary sources of some of these substances, especially the "legacy" POPs. However, the consequent decrease in its concentrations in the atmospheric compartment favors the re-emission of POPs from soils, ice, snow and water.
The Arctic and the Antarctic are remote regions, however they are contaminated by POPs. In the polar regions, persistence is increased due to low temperatures. Atmospheric deposition is also enhanced at low temperatures thanks to the scavenging of chemical compounds present in the atmosphere by the snow deposition and the low air-water and air-soil partition coefficients (a process known as "cold trapping").
In addition, biogeochemical controls such as change in vegetation cover, degradation or biological pump, influence the capture of POPs. All these processes promote the accumulation of POPs in soils, seawater and ice / snow in the polar regions, converting these matrices into reservoirs of "legacy" and emerging POPs in the polar ecosystem. However, the decrease in atmospheric concentrations, together with the increase in temperatures induced by climate change, can reverse the role of these compartments that previously acted as sinks. Furthermore, the glaciers retreat acts as a POPs source from an environmental compartment that is reducing its size on a global scale. This process, known as remobilization, has received increasing attention in the scientific community, as it has an impact on the environmental fate of POPs. Although previous observations confirm the occurrence of this process under certain circumstances, cascading changes in the different environmental compartments and their effects on other processes, on local biota and on human health, remain poorly understood.
In this thesis, the processes of remobilization from an Arctic and Antarctic coastal zones were studied, for compounds with a wide range of physical-chemical properties.
In the Arctic sampling area (Tromsø, Norway), the soil / snow-air exchange of PCBs, PAHs and OCPs was evaluated over a sampling period of 14 months. In general, atmospheric concentrations and soil / snow diffusive exchange followed a seasonality closely related to air temperature, and volatilization was observed during the warmer months.
On the coast of Livingston Island (Antarctica), the remobilization of PFASs, PAHs, OCPs and PCBs was evaluated from sampling carried out during a 3-month campaign, which included, for the first time, the simultaneous sampling of plankton, sea water, snow (including snowmelt and snow depositon), air and the determination of various fugacities, diffusive exchange fluxes and mass balances, among other analysis. Snow deposition and seasonal melting were established as key factors for all the compounds studied in POPs cycling in coastal polar ecosystems. The melting of ice and snow, linked to changes in temperature, influenced POPs concentrations in coastal waters, and as a result induced the remission of the most volatile POPs into the atmosphere. The resulting concentrations of plankton in the Antarctic coastal environment were determined for all target families, as it is a key element in the biological pump and the first step in the bioaccumulation and transfer in marine food webs.
