Experimental evidence for direct sesquiterpene emission from soils

Abstract

The biogenic organic precursors which are of relevance in secondary organic aerosol formation are primarily isoprene, monoterpenes, sesquiterpenes (SQTs) and their derivatives. Atmospheric volatile organic compound inventories consider plant emissions as the exclusive sources of natural secondary organic aerosol precursors. Very recently we have shown in pure culture experiments that abundant soil fungal strains are capable of producing significant emission fluxes of SQTs and have implied that soils might be globally important SQT emission sources. In the present follow‐up study we determined sesquiterpene emission fluxes in the laboratory directly from unperturbed soil samples and from selected soil samples with the top litter layer removed. We also characterized basic soil parameters and native fungal strains in the samples, and quantified ergosterol as a proxy of bulk fungal biomass. The measured SQT emission fluxes (6–1980 ng m−2 h−1; median 109 ng m−2 h−1) were of the same magnitude as inferred from culture experiments confirming that soil biota can be an important sesquiterpene emission source that has to be included in future VOC inventories.