Intra-Urban Variability of Air Pollution: Monitoring and Modelling of PM2.5, PM2.5-10, and NO2

Abstract

WM3-PD-02 This research was undertaken as part of the Border Air Quality Strategy (BAQS), an international agreement between the governments of Canada and the United States. Concerns about air quality in the Windsor–Detroit region have led to a number of air health effects studies being undertaken by Health Canada. The use of central site monitoring stations for assigning exposure has been cited as a potential source of exposure misclassification. Several of the health studies being undertaken for BAQS by Health Canada are investigating the chronic exposure of children to air pollution, which has required the development of local exposure studies. One of which is the development of an intra-urban monitoring network to measure a variety of ambient air pollutants. This monitoring data are being used for the development of models to predict exposure to outdoor air pollution at an intra-urban scale. There have been several intra-urban monitoring and modelling studies undertaken in Europe and North America. Land-use regression (LUR) models that have been developed using similar monitoring data have been used with success in improving exposure estimates. However, most intra-urban monitoring studies have frequently measured only NO2. Therefore, less data are available for particulate matter on such a scale. This is mainly due to the difficulty of measuring particulates at many locations, which this type of modelling requires. In Windsor, LUR models have so far been developed for NO2 using data collected with Maxxam Analytic passive samplers. NO2 concentrations ranged from 6.9 to 20.2 ppb, with a median of 12.0 ppb and were significantly correlated with distance to the Ambassador Bridge (P < 0.0001), length of expressways and highways within 50 m (P < 0.0001) and length of major roads within 100 m (P = 0.0475) in simple regression analyses. A multiple regression model including proximity to the Ambassador Bridge and proximity to highways and major roads predicted NO2 concentrations with an R2 = 0.77 on an annual basis. Measurements of NO2, PM2.5, as well PM2.5-10, were conducted throughout 4 seasons over a 2-week period in 2005 using low-flow particulate monitors located in the backyards of 50 Windsor residences. The range of PM2.5 over the 4 seasons was 6.4 to 29.3 μg/m3, initial Kriging suggests the border crossing heavily influences the higher concentrations. The LUR model is under development and results will be used to compare the relationships between NO2, PM2.5, and PM2.5-10.