Controls on surface ozone concentrations and local production in the North American pollution outflow region of Nova Scotia

Abstract

High concentrations of tropospheric ozone are a concern due to its detrimental effects on human and plant health. As the world population expands and ozone precursor emissions become more challenging to limit, understanding the drivers of ozone production is necessary to minimize ozone concentrations. This research analyzed the relationship between ozone concentrations and precursor emissions in Nova Scotia to explain long term decreasing ozone concentrations (99th percentile and median total ozone) alongside very recent rising ozone concentrations at stations across the province. This project calculated long-term trends of ozone, its precursors and transported pollution frequency, and examined variables leading to elevated ozone concentrations in Halifax where production was found to be limited by volatile organics. A novel method for diagnosing pollution transport days was developed and applied to estimate the frequency of transboundary air pollution in the province as 45-63% of elevated ozone days in Halifax, increasing over the study period.