Urban Air Quality in New York City in the 21st Century: Observations Across Multiple Sites and Field Campaigns

Ambient air quality in New York City and other U.S. urban areas has seen reduced emissions from traditional sources (e.g., motor vehicles), as well as changes in climate, which have influenced the pollutants, sources, and chemistry driving urban air quality. Recent measurement campaigns have contributed valuable observations to explore trends in primary and secondary pollutants (e.g., particulate matter, ozone, and hazardous air pollutants) and reactive precursors to those secondary pollutants. They have included the NYC-METS (New York City metropolitan Measurements of Emissions and TransformationS) campaign in summer 2022 and 2023, as part of the broader AGES+ project, as well as the continuous ASCENT (Atmospheric Science and Chemistry mEasurement NeTwork) observational network site starting in summer 2022. These field sites have brought extensive measurements of speciated gases and particulate matter to New York City (Manhattan and Queens) and downwind Connecticut. These chemically-detailed observations are used to examine the roles of local, regional, and long-distance sources and chemical processes in New York City’s air quality and changes during the 21^st century, including the effects of regional meteorology, transport, and climate change (e.g., elevated summertime temperatures, wildfire smoke transport), which together outline the current challenges for urban air quality, for New York City and beyond.