Mobile Laboratory Measurements of High Surface Ozone Levels and Spatial Heterogeneity During LISTOS 2018: Evidence for Sea Breeze Influence

The Long Island Sound Tropospheric Ozone Study (LISTOS) was organized to investigate ozone formation and transport in the New York City metropolitan area and locations downwind. During LISTOS, the University at Albany Atmospheric Sciences Research Center (ASRC) mobile laboratory was used for measuring surface O-3, NO2, and aerosol number and mass concentration. Sharp O-3 concentration gradients, with Delta O-3 Delta y(-1) over 15 ppb km(-1), were measured both at and near the land-water interface and on the highway on days characterized by high regional O-3 concentrations. These large O-3 gradients at or near the land-water interface, and in air masses relatively low in NO2, are shown to be influenced in part by the transport of highly oxidized air masses via sea breeze circulation and convergence with gradient flow. On the highway under regionally high O-3 concentrations, strong anticorrelation (R-2 = 0.78, p < 0.05) between O-3 and NO2 and an absolute slope less than 1 suggested that O-x concentrations (O-3 + NO2) increased with increasing NO2. Overall, the on-road measurements made during LISTOS help to better characterize the interaction between the emitted pollution and the meteorological conditions on Long Island, thereby having potential policy implications. Plain Language Summary Ozone pollution is a significant problem for the New York City (NYC) Metropolitan Area, which has been classified by the U.S. Environmental Protection Agency as being in noncompliance with the National Ambient Air Quality Standard for ozone. The southern coast of Connecticut is the most severely affected by ozone pollution, which is produced in the atmosphere as it travels downwind from emission sources of precursor gases like oxides of nitrogen and volatile organic compounds. The impact of ozone on a given location involves a complex interplay of emissions, meteorology, and chemistry. Our study explored aspects of this interplay on several polluted days in summer 2018 using a Dodge Sprinter van mobile laboratory equipped with instrumentation to measure ozone, one of the critical oxides of nitrogen, and other parameters. Some of the analysis days yielded significant and rapid changes in ozone concentration near the south or north shore of Long Island. Our results suggest that sea breeze winds can greatly influence ozone concentrations near the coast in some cases. Understanding when and how the sea breeze affects air quality in regions downwind of NYC and other coastal metropolitan areas will help efforts to improve air quality in these locations.