Project

Discipline

ice flow modeling; temperate glaciers; persistent organic pollutants; multimedia model; ice core; secondary source; lake sediments; transport processes; glacier; glaciology; climate change; environmental chemistry; environmental fate; persistent organic polluntants; modeling; sedimentology; mountains; Alps; ice

Lead
Lay summary
LeadMelting Alpine glaciers represent a secondary source of persistent organic pollutants. In this interdisciplinary project, including the fields of glaciology, analytical chemistry, sedimentology, and environmental fate modeling, processes affecting these hazardous chemicals in temperate glaciers are investigated.BackgroundRecent studies revealed that melting Alpine glaciers represent a secondary source of persistent organic pollutants (POPs), that were previously deposited to and incorporated into glaciers are now released back to the environment due to the rapid melting induced by climate warming. POPs represent environmental contaminants of particular concern because they are recalcitrant to degradation, accumulate in human and animal tissue, undergo long-range atmospheric transport, and can seriously threaten human health. Many complex processes occurring in glaciers, such as transport and transformation fluxes of chemicals, are largely unknown and represent great challenges, particularly for temperate Alpine glaciers containing appreciable amounts of liquid water within the glacier body. The water content of temperate Alpine glaciers in itself is poorly known and even less information exists about the flow rate of percolating meltwater. For chemicals that distribute among different environmental compartments, such as POPs, the transport mechanisms within temperate glaciers are particularly complex. GoalsThe fate of POPs in temperate glaciers, including deposition on, incorporation into, transport within, and release from ice, is investigated based on field experiments, laboratory analyses and computer modeling. The goal consists in understanding these environmental processes to quantify the flow of water and chemicals within glaciers. This interdisciplinary project is carried out by a unique consortium of glaciologists, chemists, and geologists from ETH Zurich, PSI, EMPA, and EAWAG.RelevanceThe alliance of research groups that are well experienced in complementary scientific disciplines represents a major opportunity of this interdisciplinary project. The developed models enable to estimate the amount of pollutants still stored in Alpine glaciers and the load released at present and in the future. Regarding the negative experience in the past with harmful effects from hazardous POPs in the environment, a re-emergence of such pollutants stored in remaining glaciers calls for serious investigations. Further, in the field of glaciology this project is of high importance for the fundamental understanding of water content and transport within temperate glacier ice.

Direct link to Lay Summary

Last update: 21.02.2013

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As a consequence of global warming, which is acknowledged as a major scientific and societal issue today, rapid melting of glaciers has already been observed worldwide and is expected to amplify in the near future. Recently, we have shown that melting Alpine glaciers represent an important secondary source of legacy pollutants that were previously deposited to and incorporated into glaciers and are now released at historically high rates to the environment due to the rapid melting of glaciers. In a series of preliminary studies we could confirm this “glacier hypothesis” for several persistent organic pollutants (POPs), including polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), as well as dichlorodiphenyl trichloroethane (DDT). Theses compounds are particularly hazardous environmental contaminants distinguished by their persistent, bioaccumulative, and toxic properties. Next to the confirmation of the “glacier hypothesis”, our previous studies highlighted the complexity of the underlying processes, particularly for Alpine glaciers and for the target pollutants. Firstly, most Alpine glaciers are temperate glaciers, embodying percolating meltwater next to the solid ice matrix, which significantly complicates the transport of chemical species within glaciers. Secondly, POPs have the extraordinary ability to partition between liquid percolating meltwater and solid glacial microparticles, which adds a further dimension to the transport processes within glaciers.In this project we propose to investigate the complete chain of processes affecting POPs in temperate Alpine glaciers, including their deposition, incorporation, possible transformation, transport, and release. To meet this objective, the project will include three closely linked work packages, representing each the topic of a doctoral thesis. In the first package, we will perform field measurements as well as tracer diffusion experiments to examine the distribution and temporal variation of percolating meltwater within temperate glaciers. These data will serve to develop a transient flow line model of temperate glaciers, including the percolation of meltwater as well as the motion of solid ice. In the second work package, we will establish a comprehensive inventory of chemical species in glaciers and proglacial lakes. To assess the initial incorporation of the target POPs into Alpine glaciers, a dated ice core from a cold glacier not affected by percolating meltwater will be analyzed. To examine the redistribution of POPs with percolating meltwater, we will analyze isotope tracers for water, tracers for solid glacial microparticles, and the target POPs in ice cores from temperate accumulation and ablation areas, in surface ice samples, and in glacier meltwater. Additionally, to establish the history of POPs release by temperate Alpine glaciers, we will analyze annually-layered sediment cores from proglacial lakes. Finally, the third work package will provide the complete picture of the transport chain of POPs in temperate glaciers. A dynamic multicompartmental model will be developed for ecosystems of temperate glaciers to examine the fate of POPs. All the findings from the two previous work packages, including the characterization of the percolation of meltwater and flow of ice in temperate glaciers, as well as the description of the transport mechanisms affecting POPs within glaciers, will be integrated in this multimedia fate model.For this interdisciplinary project, a research consortium of research groups in the fields of glaciology, analytical chemistry, sedimentology, as well as environmental fate modeling is formed. The close collaboration between highly experienced experts in their respective disciplines is a distinctive constellation and represents one of the major chances of this project. The characterization of the processes affecting chemical species within temperate Alpine glaciers is a unique research issue that has, so far, never been considered in such an explicitly designed approach as we suggest here and would largely contribute to an improved understanding of the fate of chemicals in the environment. Finally, the hazardous nature of the considered POPs and the dramatic receding of glaciers worldwide, suggest the relevance of this project, particularly for countries largely relying on glacial resources, such as Switzerland.