Towards an interdisciplinary characterization of the Rutor glacier (Aosta Valley)

The Rutor Glacier is located in the upper part of La Thuile valley, Italy (46.637° N, 7.016° E, area 7.5 km2, length 3.8 km, elevation between 2600-3420 m). It is one of the ten biggest glaciers in Italian Alps. Its basin is bound to the south-west by French/Italian border and the accumulation area is open to the western (Atlantic) fluxes. Three shallow firn cores (3-4 m long), representative of the previous winter season, were collected in June 2015, 2016, and 2017 on the top of the glacier. Samples were divided into two aliquots for physical analyses at the EuroCold laboratory of the University of Milano-Bicocca and for chemical analyses at the Institute of Polar Sciences and Ca’ Foscari University of Venice. The optical characterization has been carried out at EuroCold with the SPES method, which provides the extinction cross-section and optical thickness of single particles, as well as the relative concentration of particles in each sample. These physical quantities were related to the stratigraphic data and compared to the chemical analyses. The particle-by-particle approach and the simultaneous measurement of two optical parameters allow sample characterization beyond the measurement of their particle size distribution. Moreover, from the two-dimensional distribution, absorbing particles can be isolated in each sample; samples exhibiting contamination or melting and refreezing are easily recognized. The chemical analyses were devoted to the quantification of inorganic and organic species. We focused on the high-temporal resolution quantification of heavy metals, crustal elements, and Levoglucosan as biomass burning tracer, and on the year-averaged quantification of a set of organic contaminants (PFASs and their precursors, PAHs, PBDEs, PCBs, PCDD/Fs), providing the first comprehensive environmental quality study of the Rutor Glacier. The integration of the chemical results with the physical properties of the particles and future back-trajectory studies will be introductory for the determination of the contamination sources that affect the Rutor Glacier during winters. Moreover, the quantification of the organic pollutants in the ice will provide preliminary indications on their potential release in the environment under a global warming scenario.