Long-term trends reflecting regulatory impacts on VOCs sources in the New York City metropolitan area

Over the past two decades, shifts in energy use and regulatory policies in New York State have shaped emissions and air quality in the New York City (NYC) metropolitan area, a densely populated and VOC-limited nonattainment region for ozone (O₃). This study analyzed 24-h canister measurements from six sites, Queens, Bronx, Kings, Richmond, Elizabeth, and Chester, spanning the period of 2000–2021. Dispersion-Normalized Positive Matrix Factorization apportioned VOCs sources while accounting for atmospheric dilution, resolving twelve distinct sources dominated by aldehyde-rich factors, vehicle emissions, and industrial activities. Long-term trends from seasonal-trend decomposition and piecewise regression highlighted regulatory- and economy-driven shifts in source contributions. Significant declines in vehicle emissions, MTBE- and MEK-rich factors, and aldehydes aligned with Tier 2 and 3 fuel standards, MTBE phase-out, and MACT regulations. In contrast, natural gas, evaporative, biogenic, and background sources remained stable or increased, reflecting persistent and seasonally modulated emissions. Distinct site- and source-specific patterns in weekday/weekend and seasonal variability were also observed. These results show that while regulations have effectively reduced many anthropogenic VOCs sources, persistent emissions underscore the need for continued monitoring and adaptive control strategies in O₃ nonattainment regions like NYC.