posted on 2021-02-10, 20:38authored byBrett Gantt, R. Chris Owen, Nealson Watkins
As
part of the United States Environmental Protection Agency’s
2010 Nitrogen Dioxide (NO2) National Ambient Air Quality
Standards (NAAQS) review, a national network of near-road sites was
established to characterize pollutant behavior, interaction, and dispersion
in the ambient near-road environment. Using spatial interpolation
to estimate the near-road concentration increments of NO2 and particulate matter with an aerodynamic diameter of 2.5 μm
and less (PM2.5) relative to nearby non-near-road monitors,
we found that the 2013–2018 national average increment is 6.9
ppb and 1.0 μg m–3 for NO2 and
PM2.5, respectively. Analyses of the hourly near-road NO2, nitric oxide (NO), and PM2.5 increments showed
distinct diurnal cycles; the NO2 increment peaks at ∼9
ppb during the early afternoon (2–4 pm local time) while the
NO and PM2.5 increments peak during the morning rush hour
(5–8 am local time) at 25 ppb and 1.8 μg m–3 for NO and PM2.5, respectively. Although long-term trends
are not yet available for this network of sites, a similar analysis
of the NO2 and PM2.5 increment at a quasi-near-road
site outside of the official network in Elizabeth, NJ showed gradual
decreases in the increment over time since the mid-2000s.