http://blogs.wsj.com/chinarealtime/2010/12/01/california-pollution-made-in-china/
Scientists have long known that pollution and dust from China travels over the Pacific to the western United States. What they haven’t been able to figure out is how much. Until now.
In a paper published in the latest issue of the scholarly journal Environmental Science and Technology and picked up by Chemical & Engineering News, a team of geochemists announced that they have developed a method for tracing fine airborne particulate pollution (also known as PM2.5 because the particles are less than 2.5 microns wide) with origins in East Asia by testing for a specific lead isotope, 208Pb, found in greater concentrations in coal and metal ores from the region.
Led by University of California, Berkeley, postdoctoral researcher Stephanie Ewing, the team applied the isotope filter to samples from the San Francisco Bay Area, curious to see how much of northern California’s pollution came from East Asia.
The answer? A lot.
From the Chemical & Engineering News report:
From December 2007 through May 2008, the researchers collected particulate pollution samples from two sites in the San Francisco Bay Area: an urban location, Chabot Observatory, as well as a coastal location, Mt. Tamalpais, where city pollution would be limited. They filtered out the PM2.5 from the samples and measured its lead isotope abundances with multiple-collector inductively coupled plasma mass spectrometry (MC-ICPMS).
At both sites, levels of 208Pb jumped at the same time between March and May. This isotope spike coincided with the spring, when Asian dust storms are most intense, so the researchers concluded that 208Pb isotopes are a marker for PM2.5 from eastern Asia. When they analyzed data from the entire six-month survey, Ewing and her team found that the median proportion of Asian lead in the PM2.5 was 29%.
Scientists have long known that pollution and dust from China travels over the Pacific to the western United States. What they haven’t been able to figure out is how much. Until now.
In a paper published in the latest issue of the scholarly journal Environmental Science and Technology and picked up by Chemical & Engineering News, a team of geochemists announced that they have developed a method for tracing fine airborne particulate pollution (also known as PM2.5 because the particles are less than 2.5 microns wide) with origins in East Asia by testing for a specific lead isotope, 208Pb, found in greater concentrations in coal and metal ores from the region.
Led by University of California, Berkeley, postdoctoral researcher Stephanie Ewing, the team applied the isotope filter to samples from the San Francisco Bay Area, curious to see how much of northern California’s pollution came from East Asia.
The answer? A lot.
From the Chemical & Engineering News report:
From December 2007 through May 2008, the researchers collected particulate pollution samples from two sites in the San Francisco Bay Area: an urban location, Chabot Observatory, as well as a coastal location, Mt. Tamalpais, where city pollution would be limited. They filtered out the PM2.5 from the samples and measured its lead isotope abundances with multiple-collector inductively coupled plasma mass spectrometry (MC-ICPMS).
At both sites, levels of 208Pb jumped at the same time between March and May. This isotope spike coincided with the spring, when Asian dust storms are most intense, so the researchers concluded that 208Pb isotopes are a marker for PM2.5 from eastern Asia. When they analyzed data from the entire six-month survey, Ewing and her team found that the median proportion of Asian lead in the PM2.5 was 29%.