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Smoke Smudges a Megacity's Air

Sulfate Lens Enhances Climate Warming Properities of Atmospheric Soot

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Working with Thiemens, Dominguez developed a chemical fingerprinting technique that allowed the scientists to distinguish primary sulfate from ship smoke from the tailpipe emissions of trucks, cars and other sources. This was done using an oxygen-isotope technique developed by Thiemens that allows scientists to determine the signature of sulfate molecules made in the atmosphere. The researchers discovered that primary sulfates from ship engines incorporated molecular oxygen (the type we breathe in to live) and are easily distinguished from primary sulfates from car and truck diesel emissions.

Sampling air at the end of the pier at the UC San Diego's Scripps Institution of Oceanography in La Jolla, the scientists found that the smoke from ships contributed as much as 44 percent of the sulfate found in fine particulate matter in the atmosphere of coastal California. On the days when the proportion of ship sulfate approached one-half of the fine particulate matter, the scientists determined from wind direction and speed calculations that ships burning high sulfur fuel in the Los Angeles, Long Beach and San Diego ports were a major influence.

"We found that in San Diego, the Port of Los Angeles can be a significant influence on air quality because these fine particulates can travel so far," Dominguez said.

The researchers said the chemical fingerprinting techniques they developed in their study for ship primary sulfur emissions should assist the California Air Resources Board as well as regulators in other states and countries monitor the impacts of ships off their coasts as new restrictions on bunker oil burning by ships are implemented.

"This will tell us whether California's new regulation requiring cleaner burning fuel 24 miles off the coast is having the effect it's intended to have," Thiemens said. "And because a large part of the world's population live in major cities with shipping ports such as New York City, San Francisco, Hong Kong, Houston, and Singapore, and global shipping is expected to increase in the decades to come, this should help policy makers around the world make more informed decisions about improving the health of their citizens."

Other UCSD researchers involved in the study were chemist Terri Jackson, graduate student Lauren Brothers and undergraduate students Burton Barnett and Bryan Nguyen. The research project was financed by grants from the California Air Resources Board, the Camille and Henry Dreyfus Foundation, and the UC Office of the President.

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