No abstract

While human activities have altered the urban nitrogen (N) and carbon (C) cycles, the relationships between social and biophysical processes in cities are not well understood. Here we evaluated relationships between sociodemographic variables (median household income and housing age) and N and C contents and stable isotope ratios of vegetation in the Los Angeles Metropolitan Area (LA), California, and the Salt Lake Valley, Utah. We hypothesized that (1) N content and stable isotope ratios would be negatively related to income via increased N deposition in lower-income areas; (2) N and C content and N stable isotope ratios would have a positive relationship with age due to soil organic matter accumulation and increased exposure to N losses over time, respectively; and (3) δ 13 C would increase with income as a result of increased fossil fuel-derived CO 2 concentrations in lower-income areas. We found that δ 15 N values decreased with median household income in both cities and N content decreased with income in LA. In addition, atmospheric NO 2 concentrations decreased with income in LA. Soil N and C content increased with housing age. However, δ 15 N had opposing relationships with age in the two cities. Finally, foliar δ 13 C values were more isotopically depleted with both increasing household income and increasing NO 2 concentrations in LA. These results show that urban foliar and soil isotopic composition are associated with sociodemographic variables and that affluence, as well as housing age, influences urban plant and soil function.Urban areas also have highly altered carbon (C) cycles that are affected by a myriad of ecological and sociological factors. For example, urbanized areas have elevated CO 2 concentrations that may exceed 500 ppm

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 NOx 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 NOx and lowest O3 concentrations on high‐traffic density roads. Also, NOx 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 NOx 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.