Ozone precursor relationships in the ambient atmosphere

TLDR

The study analyzes and compares near‑surface concentrations of ozone, nitrogen oxides, and non‑methane hydrocarbons across urban, suburban, rural, and remote sites to elucidate their relationships and precursor sources. Measurements were conducted at diverse locations to assess these concentrations. The analysis revealed a large gradient in nitrogen oxide concentrations from remote to urban/suburban sites, comparable total hydrocarbon reactivity across all continental locations, underestimated mobile emissions in U.S.

Abstract

The concentrations of ozone, nitrogen oxides, and nonmethane hydrocarbons measured near the surface in a variety of urban, suburban, rural, and remote locations are analyzed and compared in order to elucidate the relationships between ozone, its photochemical precursors, and the sources of these precursors. While a large gradient is found among remote, rural, and urban/suburban nitrogen oxide concentrations, the total hydrocarbon reactivity in all continental locations is found to be comparable. Apportionment of the observed hydrocarbon species to mobile and stationary anthropogenic sources and biogenic sources suggests that present‐day emission inventories for the United States underestimate the size of mobile emissions. The analysis also suggests a significant role for biogenic hydrocarbon emissions in many urban/suburban locations and a dominant role for these sources in rural areas of the eastern United States. As one moves from remote locations to rural locations and then from rural to urban/suburban locations, ozone and nitrogen oxide concentrations tend to increase in a consistent manner while total hydrocarbon reactivity does not.