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6 March 2014 1:04 pm ,
Vol. 343 ,
Antiretroviral drugs can protect people from becoming infected by HIV. But so-called pre-exposure prophylaxis, or PrEP...
Two studies show that eating a diet low in protein and high in carbohydrates is linked to a longer, healthier life, and...
Considered an icon of conservation science, researchers at World Wildlife Fund (WWF) headquarters in Washington, D.C.,...
The new atlas, which shows the distribution of important trace metals and other substances, is the first product of...
Early in April, the first of a fleet of environmental monitoring satellites will lift off from Europe's spaceport in...
Since 2000, U.S. government health research agencies have spent almost $1 billion on an effort to churn out thousands...
Magdalena Koziol, a former postdoc at Yale University, was the victim of scientific sabotage. Now, she is suing the...
- 6 March 2014 1:04 pm , Vol. 343 , #6175
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ScienceShot: There's Cow in Your Smog
1 May 2012 5:06 pm
While people typically blame Southern California's smog on automobiles, a new study suggests that cows may be just as responsible, if not more so. A large fraction of the region's smog, especially the particles smaller than 2.5 micrometers in diameter, is ammonium nitrate. Those particles form in the atmosphere when ammonia, which is generated by cars with certain types of catalytic converters and by bacteria that consume cattle waste, reacts with nitrogen oxides that are produced in large quantities in automobile emissions. Data gathered during low-altitude flights in and around the Los Angeles basin in May 2010 suggest that the region's 9.9 million autos generate about 62 metric tons of ammonia each day. However, ammonia emissions from dairy farms in the eastern portion of the basin—home to about 298,000 cattle—range between 33 and 176 metric tons per day, researchers report in Geophysical Research Letters. Ammonia emissions from the dairy farms are concentrated, boosting atmospheric levels of the gas to more than 100 times background levels, so efforts to curb the farms' emissions (perhaps by feeding the animals different diets) might reduce smog more than those targeting cars.
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