Air pollution in Ontario, Canada during the COVID-19 State of Emergency.

Temporal and spatial variability of traffic-related PM2.5 sources: Comparison of exhaust and non-exhaust emissions

Characteristics and source apportionment of black carbon in the Helsinki metropolitan area, Finland

Black carbon over an urban atmosphere in northern peninsular Southeast Asia: Characteristics, source apportionment, and associated health risks.

Assessment of biomass burning and fossil fuel contribution to black carbon concentrations in Delhi during winter

Ambient measurements and source apportionment of fossil fuel and biomass burning black carbon in Ontario

A daily integrated emission factor (EF) method was applied to data from three near-road monitoring sites to identify variables that impact traffic related pollutant concentrations in the near-road environment. The sites were operated for 20 months in 2015–2017, with each site differing in terms of design, local meteorology, and fleet compositions. Measurement distance from the roadway and local meteorology were found to affect pollutant concentrations irrespective of background subtraction. However, using emission factors mostly accounted for the effects of dilution and dispersion, allowing intersite differences in emissions to be resolved. A multiple linear regression model that included predictor variables such as fraction of larger vehicles (>7.6 m in length; i.e., heavy-duty vehicles), vehicle speed, and ambient temperature accounted for intersite variability of the fleet average NO, NOx, and particle number EFs (R2:0.50–0.75), with lower model performance for CO and black carbon (BC) EFs (R2:0.28–0.4...

Near-Road Air Pollutant Measurements: Accounting for Inter-Site Variability Using Emission Factors.

. Adverse health outcomes related to exposure to air
pollution have gained much attention in recent years, with a particular
emphasis on traffic-related pollutants near roadways, where concentrations
tend to be most severe. As such, many projects around the world are being
initiated to routinely monitor pollution near major roads. Understanding the
extent to which local on-road traffic directly affects these measurements,
however, is a challenging problem, and a more thorough comprehension of it
is necessary to properly assess its impact on near-road air quality. In this
study, a set of commonly measured air pollutants (black carbon; carbon
dioxide; carbon monoxide; fine particulate matter, PM 2.5 ; nitrogen
oxides; ozone; and ultrafine particle concentrations) were monitored
continuously between 1 June 2015 and 31 March 2017 at six
stations in Canada: two near-road and two urban background stations in
Toronto, Ontario, and one near-road and one urban background station in
Vancouver, British Columbia. Three methods of differentiating between local
and background concentrations at near-road locations were tested: (1) differences in average pollutant concentrations between near-road and urban
background station pairs, (2) differences in downwind and upwind pollutant
averages, and (3) interpolation of rolling minima to infer background
concentrations. The last two methods use near-road data only, and were
compared with method 1, where an explicit difference was measured, to assess
accuracy and robustness. It was found that method 2 produced average local
concentrations that were biased high by a factor of between 1.4 and 1.7 when
compared with method 1 and was not universally feasible, whereas method 3
produced concentrations that were in good agreement with method 1 for all
pollutants except ozone and PM 2.5 , which are generally secondary and
regional in nature. The results of this comparison are intended to aid
researchers in the analysis of data procured in future near-road monitoring
studies. Lastly, upon determining these local pollutant concentrations as a
function of time, their variability with respect to wind speed (WS) and wind
direction (WD) was assessed relative to the mean values measured at the
specific sites. This normalization allowed generalization across the
pollutants and made the values from different sites more comparable. With
the exception of ozone and PM 2.5 , local pollutant concentrations at
these near-road locations were enhanced by a factor of 2 relative to their
mean in the case of stagnant winds and were shown to be proportional to
WS −0.6 . Downwind conditions enhanced local concentrations by a factor
of ∼2 relative to their mean, while upwind conditions
suppressed them by a factor of ∼4 . Site-specific factors such
as distance from roadway and local meteorology should be taken into
consideration when generalizing these factors. The methods used to determine
these local concentrations, however, have been shown to be applicable across
pollutants and different near-road monitoring environments.

/pdf/traffic-related-air-pollution-near-roadways-discerning-local-34ykmu4xty.pdf

Geoff Doerksen

Papers

Ambient measurements and source apportionment of fossil fuel and biomass burning black carbon in Ontario

Near-Road Air Pollutant Measurements: Accounting for Inter-Site Variability Using Emission Factors.

Traffic-related air pollution near roadways: discerning local impacts from background

Black carbon in the Lower Fraser Valley, British Columbia: Impact of 2017 wildfires on local air quality and aerosol optical properties