Understudied High-Pollution Band along Long Island’s South Coastline Caused by the Interaction of New York City Urban Plumes and a Stagnant Sea Breeze Front

Recent observations have highlighted extreme ozone exceedances (exceeding 100 ppb) and significant surface ozone variability along Long Island’s south shore, driven by the interaction between New York City urban plumes and a stagnant sea breeze front. Despite this, detailed spatial distribution data and associated aerosol processing information have been lacking, reducing attention to this high-pollution phenomenon. In this study, mobile lab measurements captured three extreme high ozone events on August 21, September 4, and September 6, 2023. These events confirmed the presence of a high ozone band, extending from Jones Beach to Ponquogue Beach (80–90 km). High-resolution rapid refresh (HRRR) simulations indicate that the extreme ozone concentrations (near or exceeding 100 ppb) were confined to the shallow marine boundary layer with a height of about 20–40 m along the coastline, with notable increases in particle NH4NO3 levels. The three year temporary Heckscher State Park monitor site measurements on the south shore further suggest a possible increasing trend in high ozone conditions for the Long Island south shore. This polluted band poses significant health risks to local communities as well as beachgoers on hot, sunny days and presents an opportunity for research on marine-related aerosol processing. Our study underscores the need for expanded air quality monitoring and alert systems for Long Island’s south shore as well as further studies on the marine–urban interface based on this highly polluted band.