Fig. 1

Location of particle sampling sites (W1, industrial; W2, traffic; W3; urban background) in Windsor, Ontario, and wind roses for a subset of sampling periods. Wind roses are labelled according to sampling period (e.g. W1S1 indicates sample 1 collected at site W1). Vectors represent the proportion of a collection period that the wind was coming from a given direction. Wind speed is displayed in m/s (dark blue, 1–3 m/s; light blue, 4–6 m/s; green, 7–10 m/s). The complete set of wind roses is presented in Additional file 1: Figure S1