New study could improve forecasting of haze in atmosphere

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Researchers have discovered a previously unlooked-for factor in the formation of air particles that they say could make forecasting of haze more accurate.

The research team led by University of Pennsylvania scientists studied a band of particles known as PM10 and PM2.5, their names referring to their dimension in micrometers.

These particles can contribute to haze, clouds and fog and also pose a health risk if inhaled. The researchers found that the formation of PM10s and PM2.5s can be reduced by alcohols in the atmosphere.

Previously alcohols were overlooked as a factor because they are known to interact weakly with other compounds. But according to the research team alcohols such as methanol can reduce particle formation by consuming one of the process’s main ingredients, sulfur trioxide (SO3 ).

The team found that alcohols consume or compete for SO3 , meaning that less of it is available to form sulfuric acid, a key factor in particle formation. The researchers found that the impact of alcohols in driving down the rate of particle formation may be especially strong in dry and polluted conditions.

However, they noted that the bi-product of the methanol-SO3 reaction, methyl hydrogen sulfate (MHS), has also been linked to negative health effects. According to co-lead author Jie Zhong, the new insight could help improve the accuracy of models for forecasting air pollution.

“These models haven’t been very accurate, and now we know they were not incorporating this mechanism that wasn’t recognized previously,” Zhong told Science Daily.

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