Characterization of atmospheric carbon at a remote high-alpine site

Abstract. Carbon closure and volatility studies are needed to better constrain atmospheric carbon, but are especially lacking in high altitude sites, as these environments can be challenging to access. During a measurement campaign from 16 August to 20 September 2022 at Jungfraujoch (3580 m.asl, Switzerland), gas- and particle phase carbon was characterized using a broad suite of instruments, including a thermo-denuder upstream of a time-of-flight aerosol chemical speciation monitor to investigate particulate organic carbon (pOC) volatility. As expected in summer, the Jungfraujoch was mainly under planetary boundary layer influence (PBLi), with some periods in the free troposphere (FT). Moreover, a Saharan dust event and two wildfire plumes were identified.

The composition of fine particles was dominated by organic aerosol mass for all conditions, and particulate carbon measurements by different techniques captured similar temporal variability but showed systematic differences in absolute concentrations, especially at low concentrations. pOC was dominated by semi-volatile organic carbon, and a substantial part of OC could partition between gas and particle phase depending on pOC concentration and ambient conditions. PBLi conditions, compared to FT, showed higher concentrations of both gas and particle phase compounds, higher contribution of short-lived VOCs and higher pOC volatility. In addition, the wildfires affected OC concentrations and composition and exhibited higher pOC oxidation state and lower inferred pOC volatility, coinciding with high m/z organic fragment signals. These findings contribute to a better understanding of the impacts of local and regional sources, and long-range transported plumes on free tropospheric carbonaceous compounds’ concentrations and properties.