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Chemical and physical characterization of non-tailpipe and tailpipe emissions at 100 locations near major roads in the greater Boston Area

Principal Investigator: 

The investigators are characterizing contributions to ambient particles released directly (tailpipe and non-tailpipe emissions) and indirectly (resuspended road dust). They will identify variables that may influence the emissions, using a mobile sampling platform to collect particle samples in the Greater Boston area.

Funded under

Abstract for the 2017 HEI Annual Conference

Chemical and Physical Characterization of Non-Tailpipe and Tailpipe Emissions at 100 Locations near Major Roads in the Greater Boston Area
Petros Koutrakis, Brent Coull, Joy Lawrence, Marco Martins, Stephen Ferguson, and Jack M. Wolfson
Harvard TH Chan School of Public Health, Boston, MA, USA
Background The purpose of the proposed research is to develop sampling and statistical analysis methods to improve assessment of exposure to traffic particles and pollutants for health effects studies, characterize direct (tailpipe and non-tailpipe) and indirect contributions, and identify parameters which influence them.
Methods Using a mobile sampling platform equipped with coarse and fine particulate matter (PM) concentrators we will collect ambient ultrafine, fine minus ultrafine (accumulation mode), and coarse particle samples near roads in the Greater Boston. In addition, we will collect PM2.5 and PM10 samples of aerosolized surface road dust in situ, using our Road Dust Aerosolization (RDA) sampler developed as part of this study. We will collect these road dust and ambient PM samples at three distance ranges (including background) from each of the 100 major (A1, A2, and busy A3) road sites to be included in this study. Each day of sampling, we will also collect continuous particle count, particle mass, traffic, and weather data at all 3 locations simultaneously, to assess temporal variability at sites. Potential sites are identified using Google Earth/Google Maps and evaluated during a site visit. To address temporal variability, a subset of sites will be visited multiple times in different seasons.
Results We performed a small scale pilot study, using the RDA sampler and continuous and integrated sampling methods along a busy A2 road, a background location, and an intermediate distance from the main road. Results from pilot work show distinct differences in PM composition and concentration among the different distances. PM concentrations were highest at the roadside site, but the differences were small. Consistent concentrations over multiple days between sampling locations indicates that background concentrations represent a large fraction of the total PM. Trace elemental analyses indicate relative enrichment of elements related to vehicular emissions (such as Ca, Zn, Cu, Mn, Mg, and Ba) at the main road site compared to background and intermediate sites in both coarse and fine fractions.

Ten sites have been identified for 3 repeated visits each: 3 at A1 roads, 3 at A2 roads, and 4 at A3 roads. Roadside locations were evaluated for ease of access, presence of suitable intermediate and background sites, absence of nearby construction and other identifiable point sources. Owners of privately held properties were identified from public record (e.g., assessor databases) to seek permission to locate continuous monitors 6-8 hours on 3 days during a one year period.

Conclusions Pilot test findings are supportive of vehicular sources for elements such as Ca, Zn, Cu, Mn, Mg, and Ba, and also of our expectation that we will be able to differentiate crustal material from re-suspended road dust in short duration ambient samples at different distances from the main road.