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

M Hummel,D A Healy,J R Sodeau,H Vogel,C Hoose,M Schnaiter,N H Robinson,D O'Connor,C Pöhlker,J A Huffman,M Stengel,M Gallagher,U Pöschl,E Toprak

doi:10.5194/acp-15-6127-2015

Abstract

Abstract. 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 Reactive Trace gases) regional atmospheric model. Two literature-based emission rates for fungal spores derived from fungal spore colony counts and chemical tracer measurements were used as a parameterization baseline for this study. A third, new emission parameterization for fluorescent biological aerosol particles (FBAP) was adapted to field measurements from four locations across Europe. FBAP concentrations can be regarded as a lower estimate of total PBAP concentrations. Size distributions of FBAP often show a distinct mode at approx. 3 μm, corresponding to a diameter range characteristic for many fungal spores. Previous studies for several locations have suggested that FBAP are in many cases dominated by fungal spores. Thus, we suggest that simulated FBAP and fungal spore concentrations obtained from the three different emission parameterizations can be compared to FBAP measurements. The comparison reveals that simulated fungal spore concentrations based on literature emission parameterizations are lower than measured FBAP concentrations. In agreement with the measurements, the model results show a diurnal cycle in simulated fungal spore concentrations, which may develop partially as a consequence of a varying boundary layer height between day and night. Temperature and specific humidity, together with leaf area index (LAI), were chosen to drive the new emission parameterization which is fitted to the FBAP observations. The new parameterization results in similar root mean square errors (RMSEs) and correlation coefficients compared to the FBAP observations as the previously existing fungal spore emission parameterizations, with some improvements in the bias. Using the new emission parameterization on a model domain covering western Europe, FBAP in the lowest model layer comprise a fraction of 15% of the total aerosol mass over land and reach average number concentrations of 26 L−1. The results confirm that fungal spores and biological particles may account for a major fraction of supermicron aerosol particle number and mass concentration over vegetated continental regions and should thus be explicitly considered in air quality and climate studies.

Highlights

Particles emitted from biological sources are a miscellaneous and omnipresent group of the Earth’s atmospheric aerosols (Elbert et al, 2007; Després et al, 2012)
Fungal spore concentrations simulated using the emission fluxes given in Eqs. (5) and (6) according to Sesartic and Dallafior (2011) and Heald and Spracklen (2009) were first compared to fluorescent biological aerosol particles (FBAP) measurements without further adjustment
The results indicate that the bias improves by the newly introduced emission function FFBAP, but not the correlation R between simulated FBAP and observed FBAP concentrations which remains at the value of approximately 0.43 for the overall data set, whereas for the different time periods and stations, it varies between −0.17 and 0.66

Summary

Introduction

Particles emitted from biological sources are a miscellaneous and omnipresent group of the Earth’s atmospheric aerosols (Elbert et al, 2007; Després et al, 2012). These primary biological aerosol particles (PBAP) can be transported over large distances and their impacts are studied by various fields of research, such as atmospheric science, agricultural research, biogeography, and public health (Burrows et al, 2009). Measurements of continental boundary layer air in remote vegetated regions indicate that the mass fraction of PBAP in the coarse particle size range can be as high as ∼ 30 % (> 0.2 μm, Siberia; Matthias-Maser et al, 2000) or 65–85 % (> 1 μm, Amazonia; Martin et al, 2010; Pöschl et al, 2010; Huffman et al, 2012)

Methods

Results

Conclusion