Abstracts: ISEE 22nd Annual Conference, Seoul, Korea, 28 August–1 September 2010: Air Quality and Exposures in Transportation Environments (ISIAQ Symposium)
Because on-freeway concentrations of ultrafine particles (UFP; diameter <100 nm) are relatively high, time spent on freeways can be a significant fraction of total daily UFP exposure. Here, we model size-resolved concentrations of UFP and some accumulation-mode particles (size: 100–600 nm) in freeway air.
Our approach is analogous to land-use regression, but using real-time meteorological data (temperature, wind speed, humidity) and traffic data (traffic speed and volume, derived from in-roadway loop detectors). Size-resolved particle concentrations (size: 5.5–600 nm) were measured on Minnesota freeways during the summers of 2006 and 2007. The modeling involves 2-way stratified multi-regressions.
Meteorological parameters play only a minor role in predicting real-time UFP concentrations on freeways; traffic speed and volume play a major role. Our regression model for particle number concentration has an adjusted R 2 of 0.77. Model performance is better for UFP (size: 10–100 nm; adjusted R 2: 0.79–0.89, average R 2: 0.85) than for the accumulation-mode particles studied here (size: 100–600 nm; adjusted R 2: 0.41–0.83, average R 2: 0.65).
Our model estimates real-time, size-resolved concentrations of particles (size: 5.5–600 nm) on freeways. The approach developed here is useful for identifying hotspots and as an important step toward modeling population exposure to UFP.