Air pollution in China

‘More dust actually means cleaner air’

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Interactions between weather, sandstorm dust and aerosol pollution in eastern China have been analysed in study that could have implications globally.

Levels of naturally occurring dust can play a key role in dampening down toxic man-made air pollution, the results of a study published in the journal Nature Communications suggest.

The somewhat counterintuitive finding – counterintuitive because air pollution is sometimes referred to simply as ‘dust’ – comes from a team led by post-doctoral researcher Yang Yang from the Pacific Northwest National Laboratory (PNNL) in the United States.

He has been investigating interactions between natural dust, weather and man-made pollution in Chinese cities which have been hit by severe and persistent winter haze episodes in recent years owing to intensification in aerosol pollution.

When significantly less Gobi Desert sand was blown by winds into cities like Beijing, Yang found, other harmful types of particles released by motor vehicles hung in the air in a more concentrated form, “stagnating” by more than 13 per cent during some months.

Yang, who worked with a team of seven other researchers based at the US government-backed PNNL as well as at Scripps Institution of Oceanography at the University of California, said: This is one of the first times we've really looked at the interactions between natural dust, wind, and anthropogenic pollution.

“It turns out that dust plays an important role in determining the quality of the air for many people in eastern China.”

The findings could have implications globally amid anxiety in urban areas about levels of air pollution and the consequences for people’s health.

Levels of pollutants like nitrogen dioxide have been illegally breaching EU limits in several UK cities, resulting in thousands of early deaths in Britain alone each year. Cancers and heart defects are among the medical consequences for which air pollution is thought to be a significant contributor.

In computer models together with historical data, Yang and his team found that reduced natural dust transported from the Gobi Desert in central and northern China translated into increased man-made air pollution in densely populated eastern China.

The reason is that natural dust particles in the air help deflect sunlight. Fewer dust particles translates to a warmer-than-usual land surface and cooler-than-usual water.

This in turn reduces the temperature differential in winter between sea and land, resulting in weaker winds and increased air stagnation.

According to a press release about the study: “It's nothing a person would notice – a reduction barely more than one-tenth of one mile per hour – but on a large scale over an entire region, such a seemingly minor change has a profound effect on climate and air quality.”

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