11 research outputs found
Long-term trends in submicron particle concentrations in a metropolitan area of the northeastern United States
Significant changes in emission sources have occurred in the northeastern United States over the past decade, due in part to the implementation of emissions standards, the introduction and addition of abatement technologies for road transport, changes in fuel sulfur content for road and non-road transport, as well as economic impacts of a major recession and differential fuel prices. These changes in emission scenarios likely affected the concentrations of airborne submicron particles. This study investigated the characteristics of 11–500 nm particle number concentrations and their size spectra in Rochester, NY during the past 15 years (2002 to 2016). The modal structure, diurnal, weekly and monthly patterns of particle number concentrations are analyzed. Long-term trends are quantified using seasonal-trend decomposition procedures based on “Loess”, Mann-Kendall regression with Theil-Sen slope and piecewise regression. Particle concentrations underwent significant (p < 0.05) downward trends. An annual decrease of −323 particles/cm3/y (−4.6%/y) was estimated for the total particle number concentration using Theil-Sen analysis. The trends were driven mainly by the decrease in particles in the 11–50 nm range (−181 particles/cm3/y; −4.7%/y). Slope changes were investigated annually and seasonally. Piecewise regression found different slopes for different portions of the overall period with the strongest declines between 2005 and 2011/2013, followed by small upward trends between 2013 and 2016 for most size bins, possibly representing increased vehicular traffic after the recovery from the 2008 recession
Toronto Residents' Exposure to Ultrafine Particles
In urban areas, ultrafine particles (UFP: defined as particulate matter with diameters less than 100nm) are emitted in significant quantities from vehicles and form through a complex series of secondary reactions in the atmosphere. Large uncertainties surrounding the long-term behaviour and spatial distribution of UFP in urban areas have been a significant obstacle for exposure assessment. This research examined one of the longest existing urban UFP data sets, collected at a roadside location in downtown Toronto. Between 2006 and 2011, the concentration of particles with diametersPh.D
Development of a land-use regression model for ultrafine particles in Toronto, Canada
This study applies land-use regression (LUR) to characterize the spatial distribution of ultrafine particles
(UFP) in a large city. Particle number (PN) concentrations were measured in residential areas around
Toronto, Canada, between June and August 2008. A combination of fixed and mobile monitoring was
used to assess spatial gradients between and within communities. The fixed monitoring locations
included a central site, two downtown sites, and four residential sites located 6e15 km from the
downtown core. The mobile data included average PN concentrations collected on 112 road segments
from 10 study routes that were repeated on three separate days. The mobile data was used to create the
land-use regression model while the fixed sites were used for validation purposes. The predictor variables
that best described the spatial variation of PN concentration (R2 ¼ 0.72, validated R2 ¼ 0.68)
included population density within 300 m, total resource and industrial area within 1000 m, total residential
area within 3000 m, and major roadway and highway length within 3000 m. The LUR model
successfully predicted the afternoon peak PN concentration (slope ¼ 0.96, R2 ¼ 0.86) but over-predicted
the 24-h average PN concentration (slope ¼ 1.28, R2 ¼ 0.72) measured at seven fixed monitoring sites.Funding for SOCAAR was provided by the Canada Foundation for
Innovation, the Ontario Innovation Trust, and the Ontario Research
Fund. This work was supported by the Ontario Ministry of the
Environment's Best in Science Research Program. Student stipends
were provided by the Ontario Graduate Scholarships in Science and
Technology. Special thanks to Matt Roorda for providing access to
the micro-trip simulation traffic model and the study participants
that volunteered to host the particle counting equipment in their
backyards
Metro Commuter Exposures to Particulate Air Pollution and PM2.5-Associated Elements in Three Canadian Cities: The Urban Transportation Exposure Study
System-representative commuter air pollution exposure data were collected for the metro systems of Toronto, Montreal, and Vancouver, Canada. Pollutants measured included PM2.5 (PM = particulate matter), PM10, ultrafine particles, black carbon, and the elemental composition of PM2.5. Sampling over three weeks was conducted in summer and winter for each city and covered each system on a daily basis. Mixed-effect linear regression models were used to identify system features related to particulate exposures. Ambient levels of PM2.5 and its elemental components were compared to those of the metro in each city. A microenvironmental exposure model was used to estimate the contribution of a 70 min metro commute to daily mean exposure to PM2.5 elemental and mass concentrations. Time spent in the metro was estimated to contribute the majority of daily exposure to several metallic elements of PM2.5 and 21.2%, 11.3% and 11.5% of daily PM2.5 exposure in Toronto, Montreal, and Vancouver, respectively. Findings suggest that particle air pollutant levels in Canadian metros are substantially impacted by the systems themselves, are highly enriched in steel-based elements, and can contribute a large portion of PM2.5 and its elemental components to a metro commuter's daily exposure.The authors thank the Toronto Transit Commission, la Societé ́
de transport de Montreal, and Vancouver ́ ’s Translink for their
support. We would also like to thank the field technicians from
Carleton and McGill University and the universities of British
Columbia, Toronto, and Montreal for their diligent work. We
thank Dr. Carlyn J. Matz, Hongyu You, and Marika Egyed for
their contribution to this study. We thank Dr. Phil Hopke and
the journal reviewers for their insightful comments. This study
was funded by Health Canada
Field Measurements of Gasoline Direct Injection Emission Factors: Spatial and Seasonal Variability
Four
field campaigns were conducted between February 2014 and January
2015 to measure emissions from light-duty gasoline direct injection
(GDI) vehicles (2013 Ford Focus) in an urban near-road environment
in Toronto, Canada. Measurements of CO<sub>2</sub>, CO, NO<sub><i>x</i></sub>, black carbon (BC), benzene, toluene, ethylbenzene-xylenes
(BTEX), and size-resolved particle number (PN) were recorded 15 m
from the roadway and converted to fuel-based emission factors (EFs).
Other than for NO<sub><i>x</i></sub> and CO, the GDI engine
had elevated emissions compared to the Toronto fleet, with BC EFs
in the 73rd percentile, BTEX EFs in the 80–90th percentile,
and PN EFs in the 75th percentile during wintertime measurements.
Additionally, for three campaigns, a second platform for measuring
PN and CO<sub>2</sub> was placed 1.5–3 m from the roadway to
quantify changes in PN with distance from point of emission. GDI vehicle
PN EFs were found to increase by up to 240% with increasing distance
from the roadway, predominantly due to an increasing fraction of sub-40
nm particles. PN and BC EFs from the same engine technology were also
measured in the laboratory. BC EFs agreed within 20% between the laboratory
and real-world measurements; however, laboratory PN EFs were an order
of magnitude lower due to exhaust conditioning