A Spatial Model of Urban Winter Woodsmoke Concentrations

In many urban areas, residential wood burning is a significant wintertime source of PM2.5. In this study, we used a combination of fixed and mobile monitoring along with a novel spatial buffering procedure to estimate the spatial patterns of woodsmoke. Two-week average PM2.5 and levoglucosan (a marker for wood smoke) concentrations were concurrently measured at up to seven sites in the study region. In addition, pre-selected routes spanning the major population areas in and around Vancouver, B.C. were traversed during 19 cold, clear winter evenings from November, 2004 to March, 2005 by a vehicle equipped with GPS receiver and a nephelometer. Fifteen-second-average values of light scattering coefficient (b sp) were adjusted for variations between evenings and then combined into a single, highly resolved map of nighttime winter b sp levels. A relatively simple but robust (R 2 = 0.64) land use regression model was developed using selected spatial co-variates to predict these temporally adjusted b sp values. The b sp values predicted by this model were also correlated with the measured average levoglucosan concentrations at our fixed site locations (R 2 = 0.66). This model, the first application of land use regression for woodsmoke, enabled the identification and prediction of previously unrecognized high woodsmoke regions within an urban airshed.