The Grand Est region of France experiences autumnal radiation fog that plays an important role in local atmospheric chemistry and the production of aerosols. Fog and particulate matter studies have been conducted in this region, but the study of the effect of fog on the concentration and composition of particulate matter through tandem sampling of these phases has yet to be deeply explored. Moreover, the analysis of temporal changes in the stable carbon isotopic composition (δ13C) of these phases could provide information on the sources, droplet activation, and reactivity of carbonaceous particulate matter. Samples of particulate matter and fog were collected in the city of Strasbourg and a nearby suburb, Geispolsheim, in the fall of 2016 and were characterized for their stable carbon isotopic compositions. In the presence of fog, PM2.5 was depleted in δ13C by up to 0.7‰ in Strasbourg, and PM10 was depleted by 1.1‰ in Geispolsheim. This type of isotopic depletion may be due to source-specific particle activation in which larger particles originating primarily from biogenic sources are preferentially scavenged as condensation nuclei relative to smaller, anthropogenically-derived particles. Additionally, fog samples collected in Geispolsheim were enriched relative to interstitial PM10 by up to 1.7‰. This enrichment may also be attributed to the preferential activation of larger biogenic particles during fog formation, leaving smaller anthropogenic particles in the solid phase. Fog samples were also collected in the suburban town of Erstein. In both Geispolsheim and Erstein, fog samples were enriched in δ13C compared to fog collected in Strasbourg by up to 1.2‰, which may be due to the presence of a higher fraction of biogenic emissions relative to anthropogenic emissions in these areas. Similarly, fog samples collected in Geispolsheim in 2015 were enriched in δ13C relative to those collected in the city of Metz in the same season.

Aerosol interactions with fog in urban and suburban sites in northeastern France: Applications of carbon isotopic analysis

254th National Meeting (2017)

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