Spatial and Temporal Variation in PM 2.5 Enhancements in New York City

Policy targeting PM 2.5 pollution in New York City benefits from understanding local and regional contributions to total PM 2.5 in the city. Studies from over ten years ago have shown how transported pollution can make up over half of all PM 2.5 in NYC, while studies from about five years ago have shown dramatic decreases in transported PM 2.5. This study seeks to investigate local PM 2.5 enhancements in New York City, or the percent increase of PM 2.5 levels in NYC compared to regional PM 2.5 levels. Investigation into a suitable background site using conditions laid out in Thunis’s (2018) discussion of incremental source apportionment studies is conducted, comparing Cornwall-Mohawk Mountain, Pinnacle State Park, and Whiteface Lodge and determining that the Cornwall site is best suited to measure background pollution for NYC. Diurnal and seasonal variations in PM 2.5 enhancements are conducted for four sites around NYC, finding that winter, spring, and fall months have greater enhancements by about 40% than summer months. This is likely caused by secondary organic aerosol production reaching a height in the summer months because of increased heat and daylight, so anthropogenic and biogenic sources of background PM 2.5 dominate PM 2.5 levels around NYC. Diurnal variations seem to follow trends associated with rush hours and the rise and fall of the planetary boundary layer for winter, spring, and fall, but only correlate with the rise and fall of the planetary boundary layer in the summer. Spatial variations were also tested for the four NYC sites, ultimately finding that Brooklyn generally has higher PM 2.5 levels in the winter, spring, and fall than Queens and the Bronx, while Queens and the Bronx have higher PM 2.5 levels in the summer. Enhancement values in this study represent a lower bound due to wind patterns potentially blowing PM 2.5 from NYC to Cornwall, which would make measurements of background pollution higher, and potential interference from Hartford, another urban area half the distance from Cornwall as NYC.