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Seasonal and Annual Source Appointment of Carbonaceous Ultrafine Particulate Matter (PM₀.₁) in Polluted California Cities

Xue, Jian, Xue, Wei, Sowlat, Mohammad H., Sioutas, Constantinos, Lolinco, Annabelle, Hasson, Alam, Kleeman, Michael J.
Environmental science & technology 2018 v.53 no.1 pp. 39-49
aerosols, air pollution, burning, cities, cooking, diesel fuel, emissions, fuel combustion, gasoline, genetic markers, meat, oils, organic carbon, particulates, smoke, winter, wood, California
Samples of ultrafine particle matter mass (PM₀.₁) were collected over 12 months at three cities in California: Los Angeles, East Oakland, San Pablo, and over six months at Fresno. Molecular markers adjusted for volatility and reactivity were used to calculate PM₀.₁ source contributions. Wood burning was a significant source of PM₀.₁ organic carbon (OC) during the winter months in northern California (17–47%) but made smaller contributions in other months (0–8%) and was minor in all seasons in Los Angeles (0–5%), except December (17%) during holiday celebrations. Meat cooking was the largest source of PM₀.₁ OC across all sites (13–29%), followed by gasoline combustion (7–21%). Motor oil and diesel fuel combustion made smaller contributions to PM₀.₁ OC (3–10% and 3–7%, respectively). Unresolved sources accounted for 22–56% of the PM₀.₁ OC. The lack of a clear seasonal profile for this unresolved OC suggests that it may be a primary source rather than secondary organic aerosol (SOA). PM₀.₁ elemental carbon (EC) was dominated by diesel fuel combustion with less than 15% contribution from other sources. All sources besides wood smoke exhibited relatively constant seasonal source contributions to PM₀.₁ OC reflecting approximately constant emissions over the annual cycle. Annual-average source contributions to PM₀.₁ OC calculated with traditional molecular markers were similar to the source contributions calculated with the modified molecular markers that account for volatility and reactivity.