Trends and Transport of Tropospheric Ozone From New York City to Connecticut in the Summer of 2023

Tropospheric Ozone, or O3, is a criteria pollutant contributing to most of Connecticut and New York City’s poor air quality days. It has adverse effects on human health, particularly for high-risk individuals. Ozone is produced by nitrogen oxides and volatile organic compounds from fuel combustion reacting with sunlight. The Ozone Transport Region (OTR) is a collection of states in the Northeast and Mid-Atlantic United States that experience cross-state pollution of O3. Connecticut has multiple days a year where O3 values exceed the National Ambient Air Quality Standards, requiring additional monitoring and standards because it falls in the OTR— partially due to upstream transport from New York City, Connecticut experiences increased O3 concentrations in the summer months. Connecticut has seen declines in poor air quality days from O3 every year due to the regulations on ozone and its precursors. We use ground-based Lidar, Air Quality System data, and a back-trajectory model to examine a case of ozone enhancement in Connecticut caused by air pollutants from New York City between June and August 2023. During this time, Connecticut's ozone enhancement was caused by air pollutants from New York City. As a result, New York City and Connecticut saw similar O3 spikes and decline trends. High-temperature days increase O3 in both locations and wind out of the southwest may transport O3 to Connecticut. Production and transport of O3 from New York City contribute to Connecticut’s poor air quality days, resulting in the need for interstate agreements on pollution management.