Regional-scale simulations of fungal spore aerosols using an emission parameterization adapted to local measurements of fluorescent biological aerosol particles

摘要

Fungal spores as a prominent type of primary biological aerosol particles(PBAP) have been incorporated into the COSMO-ART (Consortium for Small-scale Modelling-Aerosols and ReactiveTrace gases) regional atmospheric model.Two literature-based emission rates for fungal spores derived from fungalspore colony counts and chemical tracer measurements were used as aparameterization baseline for this study. A third, new emissionparameterization for fluorescent biological aerosol particles (FBAP) wasadapted to field measurements from four locations across Europe. FBAPconcentrations can be regarded as a lower estimate of total PBAPconcentrations. Size distributions of FBAP often show a distinct mode atapprox. 3 μm, corresponding to a diameter range characteristic formany fungal spores. Previous studies for several locations have suggestedthat FBAP are in many cases dominated by fungal spores. Thus, we suggest thatsimulated FBAP and fungal spore concentrations obtained from the threedifferent emission parameterizations can be compared to FBAP measurements.The comparison reveals that simulated fungal spore concentrations based onliterature emission parameterizations are lower than measured FBAPconcentrations. In agreement with the measurements, the model results show adiurnal cycle in simulated fungal spore concentrations, which may developpartially as a consequence of a varying boundary layer height between day andnight. Temperature and specific humidity, together with leaf area index (LAI), werechosen to drive the new emission parameterization which is fitted to the FBAPobservations. The new parameterization results in similar root mean squareerrors (RMSEs) and correlation coefficients compared to the FBAP observations as thepreviously existing fungal spore emission parameterizations, with someimprovements in the bias. Using the new emission parameterization on a modeldomain covering western Europe, FBAP in the lowest model layer comprise afraction of 15% of the total aerosol mass over land and reach averagenumber concentrations of 26 L?1. The results confirm that fungal sporesand biological particles may account for a major fraction of supermicronaerosol particle number and mass concentration over vegetated continentalregions and should thus be explicitly considered in air quality and climatestudies.