CHASE is coordinated by the Royal Meteorological Institute of Belgium with partners Ghent University (research group EnVOC, Profs Van Langenhove, Demeestere, Walgraeve), Université Libre de Bruxelles (ULB; Prof Mattielli) and Vrije Universiteit Brussel (VUB; Prof Claeys). CHASE is financed by the Belgian Science Policy Office (BELSPO) BRAIN-be programme.

Atmospheric composition change is a main driver of present and near-future climate change with airborne particles playing a major role therein. But the aerosol fluxes and sources in Antarctica and its closely associated Southern Ocean are poorly constrained, in particular the particle chemistry. Antarctica is considered the best preserved region on Earth from anthropogenic emissions. However, the impact of anthropogenic airborne particles and pollutants could be significantly larger than expected. Furthermore, a detailed understanding of present-day atmospheric transport pathways of particles and of volatile organic compounds (VOC) from source to deposition in Antarctica remains essential to document biogeochemical cycles and the relative importance of natural and anthropogenic compounds, which are not well constrained at the moment. This information is relevant to interpret climatic data extracted from ice cores and the transport and deposition of not only mineral nutrients, but also and essentially of organic micro-pollutants in polar regions. CHASE will provide detailed physical-chemical analyses of both atmospheric and surface snow particles as well as of VOCs and thoroughly investigates their atmospheric transport pathways. Samples will be taken both near the Belgian research station Princess Elisabeth (active sampling with pumps, passive samplers and surface snow samples) and on a transect to the coast as well as near the coast (only passive samplers and surface snow samples).

• The amount of polycyclic aromatic hydrocarbons (PAHs) and oxygenated PAHs in the particle phase were found to be negligible. Very likely this was due to the very low atmospheric particle number concentration measured at Princess Elisabeth station. Fluorene, phenanthrene, fluoranthene and pyrene were the most ubiquitous PAH compounds found in the samples with concentrations ranging between 1 and over 100 pg/m³. No significant inter-annual differences were found for these compounds.
• 158 samples for the analysis of volatile organic compounds (VOCs) were collected in which around 65 compounds were identified and if possible quantified. This resulted in a dataset of over 10000 data points making it the largest dataset on VOCs and oxygenated VOCs in Antarctica. It can be concluded that oxygenated aromatic compounds are by far the most important group by concentration. Acetophenone, phenol, benzaldehyde and benzoic acid are known oxidation products of primary aromatic compounds and are present in concentrations up to 2 µg/m³. Further, dimethylsulfone (DMSO₂), an oxidation product of dimethylsulfide (DMS), clearly showed a decreasing trend in function of the distance of the sample site to the ocean.
• For the first time, carbon isotope ratios of particulate organic carbon (POC) and dissolved organic carbon (DOC) were determined in surface snow samples in the region of PEA. The linear correlation between the DOC-flux and ssNa+-flux indicated that sea spray was the main source of DOC. This was confirmed by the carbon isotopic ratio of the DOC.
• The inorganic chemical analyses showed that the large majority, up to 89 %, of the sampled particles were below 2 μm and up to 50 % of particles are of submicron size. Practically no particles with a size > 5 μm were detected. This particle size pattern showed no significant distinction along the 250 km measurement transect from coast to the plateau, neither when comparing air to surface snow samples.
• For the first time, samples were collected for the analysis on the concentration of ice nucleating particles (INP) for the region of Dronning Maud Land. Compared to studies in other regions of Antarctica, the INP numbers for PEA are at the lower limit. This is an important finding, particularly for modelling studies on the aerosol influence on cloud formation and precipitation.
• The entire sample set presented a comparable mineralogical composition dominated by aluminosilicate, silica and Mg-Fe silicates closely followed by Fe-bearing aluminosilicates and iron or titanium oxides. In a much lesser proportion and non-systematically, metal-bearing particles composed of Cr, Ni, Zn, Cu, Sb, Sn, Tl, Ta were present, indicating anthropogenic sources. Special attention was given to particles containing iron (Fe), as Fe is a key micronutrient, essential for the primary productivity in the austral ocean. The occurrence of Fe-bearing particles was found to be widespread in East Antarctica.
• From chemical and isotopic analyses of particles deposited in surface snow, a novel statistical model based on the found patterns of rare earth elements (REE) has been developed. An additional major potential source area (PSA) for dust particles in East Antarctica could be identified. Besides confirming that Southern South America is the best candidate to explain the dust signature recorded during cold and warm geological periods, this study proposes for warm periods a scheme with also Southern Africa as PSA.
• A climatology of backward air mass trajectories has been established for the first time for the region of East Antarctica around PEA, covering a period of 11 years (2010-2020). A k-means cluster analysis has been performed and four clusters of air mass origin were found. Source regions from South America, Southern Africa and Australia were found to be very limited. The Southern Ocean was a main source region, as was the Antarctic continent itself. For the most important air mass cluster, the source region is mostly restricted to the region above the Antarctic continent and the average altitude along the trajectories in this cluster indicated that this cluster corresponded mainly to air subsiding from the upper troposphere.

Methodology
The starting point consists of the particle and air sampling followed by a thorough physical-chemical analysis with state-of-the art and innovative analytical instruments. Sampling of atmospheric particles for organic composition analyses will be done by active High-Volume sampling on quartz fibre filters in the first place and by exploring the possibilities of passive sampling, using e.g., polyurethane foam plugs (PUF). Molecular chemical analyses will be carried out by liquid or gas chromatography coupled to high resolution mass spectrometry (HRMS). Also, the occurrence and concentration levels of atmospheric VOCs will be investigated by means of  passive sampling followed by TD-GC-MS analysis. The determination of the inorganic composition of AP will be done by both passive and active sampling. In addition, surface snow will be collected for inorganic particle composition analysis. Single particle morphological and chemical analyses will be done by automated-FEG-SEM-EDS analyses and both geochemical and isotopic analyses by HR-ICP-MS and MC-ICP-MS, respectively. Isotope Ratio Mass Spectrometry (IRMS) will determine the stable isotopic signature (C, N) of the different types of organic material recovered. Air mass tracing will be carried out by dispersion analysis of atmospheric transport, using the atmospheric dispersion model FLEXPART.

Interdisciplinarity
The Royal Meteorological Institute of Belgium (RMI) brings in its expertise on atmospheric composition modelling, validation of satellite observations, aerosol studies, atmospheric dispersion modelling and carrying out research campaigns to Princess Elisabeth station.

The EnVOC research group of Ghent University focuses since more than 30 years on the occurrence, fate and behaviour of organic micropollutants in the environment, with particular attention to the compartments particulate matter, air and water. It has built up considerable expertise in the sampling, sample preparation and analysis of VOCs, PM, and emerging organic micropollutants, using state-of-the art analytical instruments.

The research unit of Prof. Nadine Matielli of Université Libre de Bruxelles (Laboratoire G-Time) hosts state-of-art analytical facilities, which are almost unique in Belgium (HR-MC-ICP-MS-Nu instrument, necessary for isotopic analyses of radiogenic isotopes like Pb, Nd and of heavy stable isotops like Zn). At Vrije Universiteit Brussel, Belgium, Philippe Claeys heads the interdisciplinary research unit Earth System Sciences and within it he heads the research unit Analytical, Environmental and Geo – Chemistry. The groups of Prof. Matielli and of Prof. Claeys have built a shared analytical platform, facilitating the access to the HR-ICP-MS required for the trace element analyses.

Further expertise and in-kind contributions will come from Profs. Karine Deboudt and Pascal Flament from the Laboratory of Physics and Chemistry of the Atmosphere, Université du Littoral – Côte d’Opale, Dunkerque, France ( aerosol characterisation by applying single-particle analysis; SEM-EDX), Prof. Reto Gieré, Department of Earth and Environmental Science, University of Pennsylvania, USA (translating the SEM-EDX chemical data into mineralogical data) and from Dr. Volker Dietze, German Meteorological Service, Germany (passive sampler equipment and related expertise).

1 January 2017 - April 2021. Prolonged to April 2022.

Project PIs at RMI: Dr. Alexander Mangold and Dr. Andy Delcloo

Contact:
Royal Meteorological Institute of Belgium
Ringlaan 3, Avenue Circulaire
BE-1180 Brussels, Belgium
Tel: 0032-23730593