Sequential sampling of Volatile Organic Compounds (VOCs) and atmospheric oxidation products in the Sør Rondane Mountains, East-Antarctica.

Antarctica is considered the most pristine environment on Earth. However, a detailed understanding of present-day atmospheric transport pathways of particles and volatile organic compounds (VOC) from source to deposition in Antarctica and the atmospheric reactions they undergo is essential to document biogeochemical cycles. Atmospheric composition plays an important role in present and near-future climate change. Airborne particles can serve as cloud condensation and ice nuclei and have therefore a strong influence on cloud formation and thus also on precipitation. This is of interest in Antarctica, since precipitation is the only source of mass gain to the Antarctic ice sheet which is expected to become the dominant contributor to global sea level rise in the 21st century. VOCs and their atmospheric oxidation products, secondary organic aerosols (SOA’s) can play an important role in this cloud formation process. However, current knowledge on VOCs and on the interaction between clouds, precipitation and aerosols in the Antarctic is still limited, both from direct observations and from regional climate models.

VOCs are traditionally sampled using axial thermal desorption sampling tubes containing a sorbent such as Tenax TA in a passive or active (pumped) fashion. While with passive sampling it is possible to sample over longer periods of time, up to a year in clean air conditions, the temporal information is lost. Because of uncertainties on the sample rate, which is driven by diffusion, obtaining precise air concentrations with passive sampling can be difficult. To sample VOC’s and oxidations products unsupervised and in a remote environment such as Antarctica a new active sequential sorbent tube autosampler was developed and deployed at the atmospheric observatory of the Princess Elisabeth Antarctic research station (71.95° S, 23.35° E, 1390 m asl). The autosampler collected samples from December 2019 to October 2020 and from January 2021 to June 2021. The obtained data is also used to complement and interpret atmospheric aerosol in-situ measurements conducted at the same location. Furthermore, to identify potential source regions, backward trajectory and dispersion modelling using FLEXTRA and FLEXPART will be applied.