Dryland Soil Rewetting Induces Strong Volatile Organic Compound Emissions With Potential to Form Ozone and Aerosols.

Drylands cover nearly half of Earth's terrestrial surface and are expanding under climate change. Biogenic volatile organic compounds (VOCs) significantly influence atmospheric chemistry, yet microbial VOC emissions from dryland soils remain poorly understood. Here, we investigate VOC emissions associated with petrichor-the characteristic scent following rainfall after prolonged drought-across a steep aridity gradient extending into the Negev Desert. Soil rewetting triggered strong VOC fluxes (1-3.5 nmol m-2 s-1 ground area) dominated by sesquiterpenes and benzenoids, with emission patterns and rates linked to climatic regions, soil aridity, and microbial community composition. Petrichor consisted of a complex bouquet of 58 VOCs, and emission fluxes showed a pronounced initial burst. We upscaled the results to Israel and show that petrichor emissions contribute significantly to ozone and secondary organic aerosol formation potentials, comparable in magnitude to those estimated for anthropogenic VOC sources. Soil aridity shaped VOC chemical composition and emission dynamics, indicating strong microbial and environmental controls on the fluxes. As climate change alters precipitation regimes and promotes dryland expansion, these rainfall-driven bursts of microbial VOCs may represent an overlooked climate-microbe feedback influencing atmospheric chemistry and radiative forcing at regional and global scales.