Dryland soil rewetting induces strong VOC emissions with potential to form ozone and aerosol

Biogenic volatile organic compounds (VOCs) significantly influence atmospheric chemistry, yet the importance of microbial VOC emissions remains understudied. We investigate petrichor VOC emissions, the characteristic scent following rainfall after prolonged drought, across Israel’s aridity gradient, by simulating soil rewetting events. Rewetting triggered strong VOC fluxes (1-3.5 nmol m^-2 s^-1 ground area) dominated by sesquiterpenes and benzenoids, with emission patterns linked to climate-regions, soil aridity, and microbial community composition. Petrichor was composed of a complex bouquet of 58 VOCs, and the initial VOC burst resembled the CO₂ pulse of the Birch effect. Petrichor emissions showed ozone and secondary organic aerosol formation potentials comparable to anthropogenic VOC sources in Israel. Despite compositional differences, emission magnitudes were of similar order across the aridity gradient. Given that drylands cover nearly half of Earth's land and are expanding, these episodic microbial VOC emissions may represent a significant, previously overlooked source of reactive carbon with potential implications for regional and global atmospheric chemistry.