Modelling of atmospheric concentrations of fungal spores: a two-year simulation over France using CHIMERE

Fungal spore organic aerosol emissions have been recognised as a significant source of particulate matter as PM ₁₀; however, they are not widely considered in current air quality models. In this work, we have implemented the parametrisation of fungal spore organic aerosol (OA) emissions introduced by Heald and Spracklen (2009) (H&S) and further modified by Hoose et al. (2010) in the CHIMERE regional chemistry-transport model. This simple parametrisation is based on two variables which are leaf area index (LAI) and specific humidity. We have validated the geographical and temporal representativeness of this parametrisation on a large scale by using yearly polyol observations and primary biogenic organic aerosol factors from PMF analysis at 11 French measurement sites. For a group of sites in northern and eastern France, the seasonal variation of fungal spore emissions, displaying large summer and small winter values, is correctly depicted. However, the H&S parametrisation fails to capture fungal spore concentrations for a smaller group of Mediterranean sites with less data availability both in terms of absolute values as well as seasonal variability, leading to strong negative biases especially during the autumn and winter seasons occur. Two years of CHIMERE simulations with the H&S parametrisation have shown a significant contribution of fungal spore OA to PM ₁₀ mass, lower than 10 % during winter, and reaching up to 20 % during summer in high emission zones, especially over large forested areas. In terms of contribution to organic matter (OM) concentrations, the simulated fungal spore contribution in autumn is as high as 40 % and reaches at most 30 % of OM for other seasons. As a conclusion, the fungal spore OA contribution to total OM concentrations is shown to be substantial enough to be considered as a major PM ₁₀ fraction and shall then be included in state-of-the-art chemistry transport models. The H&S parametrisation shows satisfactory results over northern and eastern France, but may underestimate concentrations for Mediterranean areas that may indicate missing factors influencing emissions or a missing source of spores.