OOS 7-6 - The influence of household income and traffic density on foliar chemistry and atmospheric pollution in Salt Lake Valley, UT

Tuesday, August 13, 2019: 9:50 AM
M104, Kentucky International Convention Center
La'Shaye A.E. Cobley1, Diane Pataki1 and Frederick Adler2, (1)School of Biological Sciences, University of Utah, Salt Lake City, UT, (2)School of Biological Sciences and Department of Mathematics, University of Utah, Salt Lake City, UT
Background/Question/Methods

Vehicle emissions greatly alter the nitrogen cycle in urban ecosystems, but their local causes and effects remain poorly understood. Here, we collected Convolvulus arvensis (bindweed) leaves and measured concentrations of NOx and O3 along road transects of varying neighborhood income and traffic density. We sampled 3 high income (< $80,000) and 3 low income (> $40,000) neighborhoods as determined by the US census. We also sampled high (20,000 vehicles/day annually) and low traffic density roads (10,000 vehicles/day annually) in each neighborhood as established by the Department of Transportation. We measured atmospheric pollutant concentrations during three daily time intervals (morning, afternoon and evening) for 9 days. We tested three hypotheses: 1) Bindweed foliar chemistry will reflect NOx concentrations, with the highest foliar %N, most enriched δ15N and most depleted δ13C on high traffic density roads in low income areas; 2) NOx concentrations and foliar chemistry will be correlated with traffic density and neighborhood income; 3) O3 concentrations will show opposing patterns in foliar chemistry variables, traffic density and neighborhood income compared to NOx. We assessed these relationships with mixed effect models, Wilcoxon rank sum test, and two-way ANOVAs.

Results/Conclusions

Foliar δ15N significantly decreased with increasing atmospheric O3 concentrations and marginally increased with increasing NOx concentrations. We also found neighborhood differences in foliar chemistry that were not explained by income or traffic alone. One low income neighborhood had lower foliar %N than all of the high income neighborhoods. One high income neighborhood had the most depleted δ15N and another had more enriched δ13C than three other neighborhoods. Our second and third hypotheses were supported in that NOx concentrations were highest on high traffic density roads in low income areas throughout the day. In addition, O3 was lowest on low traffic density roads in low income areas in the afternoon, but did not vary with income or traffic density in the morning or evening. Because high trafficked roads have large spatial footprints and low income neighborhoods in the Salt Lake Valley contain more high traffic density roads, low income areas appear to be experiencing higher levels of pollution than high income areas as a consequence of the many surrounding high trafficked roads.