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17 April 2014 12:48 pm ,
Vol. 344 ,
Officials last week revealed that the U.S. contribution to ITER could cost $3.9 billion by 2034—roughly four times the...
An experimental hepatitis B drug that looked safe in animal trials tragically killed five of 15 patients in 1993. Now,...
Using the two high-quality genomes that exist for Neandertals and Denisovans, researchers find clues to gene activity...
A new report from the Intergovernmental Panel on Climate Change (IPCC) concludes that humanity has done little to slow...
Astronomers have discovered an Earth-sized planet in the habitable zone of a red dwarf—a star cooler than the sun—500...
Three years ago, Jennifer Francis of Rutgers University proposed that a warming Arctic was altering the behavior of the...
- 17 April 2014 12:48 pm , Vol. 344 , #6181
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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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