101 lines
4.4 KiB
Markdown
101 lines
4.4 KiB
Markdown
---
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created_at: '2013-08-21T05:27:42.000Z'
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title: 29% of Bay Area's particulate air pollution comes from across the Pacific (2010)
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url: http://pubs.acs.org/cen/news/88/i46/8846news3.html?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed:+EnvironmentalScienceTechnologyOnlineNews+ES%26T+Online+News
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author: balsam
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points: 74
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story_text: ''
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comment_text:
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num_comments: 65
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story_id:
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story_title:
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story_url:
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parent_id:
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created_at_i: 1377062862
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_tags:
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- story
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- author_balsam
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- story_6248383
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objectID: '6248383'
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year: 2010
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---
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NASA/Jeff Schmaltz, MODIS Rapid Response team.
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TRANS-PACIFIC PLUME
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In March 2008, a typical "yellow dust" plume from the Gobi Desert blew
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eastward over the Beijing region.
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#### Text Size [A]()[A]()
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The Clean Air Act sets air quality standards that municipalities in the
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United States must meet. But some pollution travels from thousands of
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miles away. Now researchers have developed a method to more precisely
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identify the origins of small particulate pollutants ([Environ. Sci.
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Technol., DOI:
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10.1021/es101450t](http://pubs.acs.org/cgi-bin/cen/trustedproxy.cgi?redirect=http://pubs.acs.org/doi/abs/10.1021/es101450t "Pb Isotopes as an Indicator of the Asian Contribution to Particulate Air Pollution in Urban California")).
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With it, they determined that 29% of the San Francisco area's
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particulate pollution comes from eastern Asia.
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Fine airborne particulate pollution—called PM2.5, because the particles
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measure less than 2.5 µm in diameter—can cause health problems such as
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asthma and lung damage, and exacerbate heart disease, according to the
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Environmental Protection Agency. Combustion as well as smelting and
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processing metals produces the particles. Major combustion sources
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include emissions from coal-fired power plants and automobile exhaust.
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These sources can leave a chemical signature of their origins in the
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particles that they emit.
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One such signature is the abundance of various lead isotopes. The coal
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and metal ores mined in China and eastern Asia have a significantly
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higher proportion of 208Pb, which forms from radioactive decay of
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thorium, than do coal and ores used in America .
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China generates about 70% of its electricity with coal-fired power
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plants, creating large amounts of particulate pollution. Dust storms
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crossing China pick up these particles and carry them across the Pacific
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to the U.S.
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[Stephanie
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Ewing](http://landresources.montana.edu/Department/Ewing.html), then a
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postdoctoral scholar in isotope geochemistry at the [University of
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California, Berkeley](http://berkeley.edu/), and her colleagues wondered
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whether the ratios of lead isotopes in PM2.5 could quantify how much of
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the local pollution originated from Asia.
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From December 2007 through May 2008, the researchers collected
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particulate pollution samples from two sites in the San Francisco Bay
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Area: an urban location, Chabot Observatory, as well as a coastal
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location, Mt. Tamalpais, where city pollution would be limited. They
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filtered out the PM2.5 from the samples and measured its lead isotope
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abundances with multiple-collector inductively coupled plasma mass
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spectrometry (MC-ICPMS).
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At both sites, levels of 208Pb jumped at the same time between March and
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May. This isotope spike coincided with the spring, when Asian dust
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storms are most intense, so the researchers concluded that 208Pb
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isotopes are a marker for PM2.5 from eastern Asia. When they analyzed
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data from the entire six-month survey, Ewing and her team found that the
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median proportion of Asian lead in the PM2.5 was 29%.
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Ewing, now an assistant professor of land resources and environmental
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science at [Montana State University](http://www.montana.edu/), thinks
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that the isotopic identification method also may help scientists
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understand the movements of pollutants throughout the atmosphere.
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[Julian Marshall](http://personal.ce.umn.edu/~marshall/), an assistant
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professor of environmental engineering at the [University of
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Minnesota](http://www1.umn.edu/twincities/index.php), Minneapolis, says
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that Ewing and her team have presented an "interesting new method and
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new results." He suggests that in addition to further dissecting the
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origins of PM2.5, high-resolution isotopic identification also could
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help test the accuracy of global atmospheric circulation models.
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- Chemical & Engineering News
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ISSN 0009-2347
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Copyright © 2011 American Chemical Society
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