Secondary Organic Aerosols alive and well in fossil-fuel-combusted engine exhaust

In the Nov. 15, 2012 Pacific Northwest National Laboratory’s “Airborne particles smuggle pollutants to far reaches of globe” news release, Mary Beckman wrote: “Floating in the air and invisible to the eye, airborne particles known as secondary organic aerosols live and die. Born from carbon-based molecules given off by trees, vegetation, and fossil fuel burning, these airborne SOA particles travel the currents and contribute to cloud formation.”

Knowing that these SOAs get around is one thing. Understanding the air and human-health impacts is quite another.

In “Air pollution study clears the air on diesel versus gas emissions,” meanwhile, author Sarah Yang, right up front asks: “Are gasoline-fueled cars or large diesel trucks the bigger source of secondary organic aerosol (SOA), a major component of smog?” Yang in answering, explains: “UC Berkeley researchers have stepped into this debate with a new study that says diesel exhaust contributes 15 times more than gas emissions per liter of fuel burned.”

Moreover, additional study findings should be of particular importance; in particular, to anyone residing in areas where a relative high concentration of diesel combustion takes place and where the emissions of such adds in a significant way to a region’s air pollution. Why? If for no other reason than due to the SOAs negative impact on human health is why.

“SOA contributes to respiratory problems and poor air quality,” Yang insists, “so pinpointing the major sources of the pollutant is important in evaluating current and future policies to reduce smog in [California]. …The study, published [on Oct. 22, 2012] in the Proceedings of the National Academy of Sciences, elucidates the contributions to air pollution from the two types of fuel emissions. The authors estimate that diesel exhaust is responsible for 65-90 percent of a region’s vehicular-derived SOA, depending upon the relative amounts of gasoline and diesel used in the area.”

And as it relates, there is this from an earlier post: “The Public Policy Institute of California in its report: ‘Planning for a Better Future: California 2025: 2010 Update (Transportation),’ revealed based on California Environmental Protection Agency Air Resources Board data, in California in 1975, and within the transportation sector, smog-forming emissions generated via passenger vehicles accounted for a full percent 70 percent with the remainder being released from heavy duty vehicles, off-road vehicles and other mobile sources. By 2006 it was an altogether different story as the lion’s share of state transportation-sector-released smog-forming emissions – 75 percent – were coming from the latter group – heavy-duty vehicles, off-road vehicles and that contributed from other mobile sources.

“In 2006, whereas passenger vehicles accounted for roughly 25 percent of all smog-forming pollution contributed from state transportation modes, and about 40 percent was the off-road and other mobile sources category share, approximately 35 percent was released from the heavy-duty on-road modes – mostly buses and trucks.”

The significance of the UC Berkeley study in question goes without saying.

Hydrogen vehicle
Hydrogen vehicle

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