Monday, November 15, 2010

Atmospheric Chemistry Processes in Smog Formation

Predicting Smoggiest Days: Experiments Improve Accuracy of Ozone Predictions in Air-Quality Models (Science Daily, Oct. 28, 2010)

Also discussed here: Rate of Gas Phase Association of Hydroxyl Radical and Nitrogen Dioxide (Abstract, Science, Vol. 330. no. 6004, pp. 646 – 649, Oct. 29, 2010)

Key Quotes:

“The reaction of OH and NO2 to form gaseous nitric acid (HONO2) is among the most influential in atmospheric chemistry….We demonstrate the impact of the revised value on photochemical model predictions of ozone concentrations in the Los Angeles airshed.”

“The key reaction in question in this research is between nitrogen dioxide and the hydroxyl radical.. Until about the last decade, scientists thought these two compounds only combined to form nitric acid, a fairly stable molecule with a long atmospheric life that slows ozone formation”

“researchers found the loss of hydroxyl radical and nitrogen dioxide is slower than previously thought-although the reactions are fast, fewer of the radicals are ending up as nitric acid than had been supposed, and more of them are ending up as peroxynitrous acid.”

"a small but significant impact on the predictions of computer models used to assess air quality, regulate emissions and estimate the health impact of air pollution,"

“the laboratory results suggest that, on the most polluted days and in the most polluted parts of L.A., current models are underestimating ozone levels by 5 to 10 percent”

“a 10 part-per-billion increase in ozone concentration may lead to a four percent increase in deaths from respiratory causes-any increase in expected ozone levels will be important to people who regulate emissions and evaluate health risks”

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