Crop harvest in Central Europe causes episodes of high airborne Alternaria spore concentrations in Copenhagen
1Department of Environmental Science, Aarhus University, Frederiksborgvej 399, 4000, Roskilde, Denmark
2Department of Earth and Ecosystem Sciences, Sölvegatan 12, Lund University, 223 62, Lund, Sweden
3Astma-Allergy Denmark, Universitetsparken 4, 4000, Roskilde, Denmark
Abstract. This study tests the hypothesis that Danish agricultural areas are the main source to airborne Alternaria spores in Copenhagen, Denmark. We suggest that the source to the overall load is mainly local, but with intermittent Long Distance Transport (LDT) from more remote agricultural areas. This hypothesis is supported by investigating a 10 yr bi-hourly record of Alternaria spores in the air from Copenhagen. This record shows 232 clinically relevant episodes with a distinct daily profile. The data analysis also revealed potential LDT episodes almost every year. A source map and analysis of atmospheric transport suggest that LDT always originates from the main agricultural areas in Central Europe. A dedicated emission study in cereal crops under harvest during 2010 also supports our hypothesis. The emission study showed that although the fields had been treated against fungal infections, harvesting still produced large amounts of airborne fungal spores. It is likely that such harvesting periods can cause clinically relevant levels of fungal spores in the atmosphere. Our findings suggest that crop harvest in Central Europe causes episodes of high airborne Alternaria spore concentrations in Copenhagen as well as other urban areas in this region. It is likely that such episodes could be simulated using atmospheric transport models.