Unaccounted impacts of diterpene emissions on atmospheric aerosol loadings

Diterpenes, found in trees, have been overlooked in atmospheric chemistry due to their low volatility and presumed negligible emissions. However, advances in sampling and analytical methods now allow for their detection in the gas phase. Here we quantify diterpene emission factors and evaluate their role in secondary organic aerosol formation. By incorporating all available emission data and laboratory-derived aerosol yields into the MONARCH chemistry transport model, we assessed their atmospheric contribution. Chamber experiments revealed kaurene yields of 1.8–17%, indicating efficient gas-to-particle conversion. Global emissions were estimated at 11.5 (0.1–94.3) Tg yr⁻¹, contributing 0.63 (0.005–5.19) Tg yr⁻¹ to secondary organic aerosol production and a burden of 0.008 (0.00007–0.07) Tg. This corresponds to 13%, 6.4%, and 19% of the aerosol burden from isoprene, monoterpenes, and sesquiterpenes, respectively. These results demonstrate that diterpenes are a previously underestimated, but potentially important, source of secondary organic aerosol, with implications for biosphere-atmosphere interactions.