We performed more
than a year of mobile, 1 Hz measurements
of lung-deposited
surface area (LDSA, the surface area of 20–400 nm diameter
particles, deposited in alveolar regions of lungs) and optically assessed
fine particulate matter (PM2.5), black carbon (BC), and
nitrogen dioxide (NO2) in central London. We spatially
correlated these pollutants to two urban emission sources: major roadways
and restaurants. We show that optical PM2.5 is an ineffective
indicator of tailpipe emissions on major roadways, where we do observe
statistically higher LDSA, BC, and NO2. Additionally, we
find pollutant hot spots in commercial neighborhoods with more restaurants.
A low LDSA (15 μm2 cm–3) occurs
in areas with fewer major roadways and restaurants, while the highest
LDSA (25 μm2 cm–3) occurs in areas
with more of both sources. By isolating areas that are higher in one
source than the other, we demonstrate the comparable impacts of traffic
and restaurants on LDSA. Ratios of hyperlocal enhancements (ΔLDSA:ΔBC
and ΔLDSA:ΔNO2) are higher in commercial neighborhoods
than on major roadways, further demonstrating the influence of restaurant
emissions on LDSA. We demonstrate the added value of using particle
surface in identifying hyperlocal patterns of health-relevant PM components,
especially in areas with strong vehicular emissions where the high
LDSA does not translate to high PM2.5.
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