Transportation-Related Sources of Nitrous Oxide

Nitrous oxide (N2O) is a potent greenhouse gas and the most abundant stratospheric ozone-depleting substance. Atmospheric mixing ratios of N2O have rapidly increased in recent years, and quantifying sources of N2O emissions is critical for climate change mitigation. We quantified and characterized N2O emission sources at street level using mobile laboratory measurements in New York City taken over 10 days in January and June 2025. N2O plume enhancements were strongly correlated with carbon monoxide (CO) and carbon dioxide (CO2). We identified city buses using clean air technology as the source of these enhancements. Using estimates of bus-related CO2 emissions, we estimated annual N2O emissions from buses in New York City of 31 (±14) tonne-N2O yr–1. With increased deployment of clean air technologies to reduce NOx pollution from diesel vehicles globally, N2O emissions from transportation are likely under-reported and should be accounted for in emissions inventories.