Reconciling observed and modeled estimates of urban terpenoid emissions

Extensive observations highlight the significance of terpenoids in urban air quality. However, emission frameworks fail to capture their magnitude and spatial variability, limiting air quality management and atmospheric modeling. Here we reconcile observed and modeled urban terpenoid emissions and uncover intense, underrepresented anthropogenic sources in Greater Los Angeles by combining improved emission inventories, airborne flux measurements, and ground-based mobile measurements. We demonstrate that an enhanced biogenic inventory significantly reduces the discrepancy between modeled and observed isoprene fluxes, and the remaining gap in monoterpenoids is explained predominantly by anthropogenic sectors. We identify that these emissions originate from previously overlooked food industry and commercial businesses, which exhibit a biogenic-like temperature dependence. These anthropogenic sources account for 44% of the top 10% observed monoterpenoid flux hotspots and contribute 17% of the total flux. Given their ubiquity in urban and industrialized regions worldwide, these poorly characterized sources may influence air quality beyond Los Angeles.