We utilize traffic density and Convolvulus arvensis leaf chemistry to understand spatial patterns linking atmospheric pollution and household income in the Salt Lake City metropolitan area, USA. We hypothesize that traffic density will explain variation in atmospheric NO_x and O₃ concentrations. In addition, we expect foliar %N and nitrogen isotope ratios (δ¹⁵N) to be elevated and carbon isotope ratios (δ¹³C) to be depleted on high traffic density roads. These hypotheses were supported: we found the highest NO_x and lowest O₃ concentrations on high-traffic density roads. Also, NO_x concentrations were higher in low-income neighborhoods. Low-income neighborhoods contained a greater density of high-traffic roads than high-income neighborhoods. Foliar %N was highest in low-income neighborhoods and was correlated with NO_x and O₃, while δ¹⁵N was more depleted with increasing O₃. These findings indicate that the distribution of high-traffic density roads plays a significant role in inequities in pollution exposure between high- and low-income neighborhoods, which is reflected in leaf chemistry.

Details on the methodology can be found in the "Metadata" tab in the attached excel file and in Cobley et al. 2021.