Downwind O₃ and PM_2.5 speciation during the wildfires in 2002 and 2010

A series of wildfires in northern Quebec, early July 2002, and in southern Quebec, late May 2010, resulted in severe air pollution downwind. Downwind exposures were investigated to estimate the impact on outdoor and indoor environments. The plumes derived from the wildfires resulted in an increase of over 10 ppbv ozone (O₃) concentrations in both major cities and rural areas, while O₃ enhancement was not observed at locations adjacent to wildfire burning areas. Temporal trend in PM_2.5 concentration showed a peak of 105.5 μg/m³ on July 7, 2002, while on May 31, 2010 the peak was 151.1 μg/m³ in Boston downwind. PM_2.5 speciation showed similar trends between the episodes, along with spikes in the PM_2.5/PM₁₀ ratio, and in the concentrations of Black Carbon, ΔC (i.e., UV absorbing compounds minus Black Carbon), Organic Carbon (OC), potassium, and chlorine. OC was the most dominant constituent of the PM_2.5 mass in the wildfires. The dominant specific carbon fractions include OC fraction 3, pyrolysis carbon, and EC fraction 1, likely due to pyrolysis of structural components of wood. Indoor PM_2.5 peaks at two houses corresponded well with the ambient PM_2.5 peak, along with the elemental composition, which could indicate an impact of wildfires on indoor air pollution exposure.