JULY’S clear blue sky is not a mirage. The city’s air quality lately has been better than even last August, when the city government implemented emission restrictions for the Universiade.
Since July 1, Shenzhen’s average daily level of PM2.5 — or fine particulate matter — has been less than 20mg per cubic meter, the average level during the Universiade, according to the Shenzhen Environmental Monitoring Center. The average PM2.5 levels at some air quality monitoring stations are less than 10mg per cubic meter, within the air quality standards of the World Health Organization.
Experts attribute the improved air quality to seasonal trends and a favorable climate. Huang Yuanfeng, director of the Automatic Monitoring Information Office at the monitoring center, said southeasterly winds predominate in the city during summer, bringing clean air from the South China Sea.
Tropical Storm Doksuri, for example, arrived in Shenzhen on June 29. The city’s PM2.5 and PM10 levels that morning were both around 100mg per cubic meter. The levels gradually dropped as the storm approached. The average PM2.5 level later that day was 38mg per cubic meter, and it fell to 19mg per cubic meter by June 30.
The low PM2.5 levels have continued through July so far.
Huang said fine particles in the air are quicker to disperse in the windy summer. He Lingyan, an air quality and environmental professor at Shenzhen Graduate School of Beijing University, agreed and said favorable climate conditions and the city’s efforts to cut emissions are contributing to the better air quality.
Some netizens worried, though, that clean air could indicate a worsening economy. Many said the sky becomes bluer and air clearer when factories reduce their outputs or close altogether.
Professor He said those statements are “specious and groundless” because factory clusters are located in Dongguan and Huizhou, two cities north of Shenzhen.
“But summer wind is from the south, where the sea is located,” she said.
Huang said residents could continue enjoying such nice air and beautiful skies until late August. But he said summer air conditions are not a proper indicator of the city’s overall air quality, which can only be best evaluated by including the fall, as well.
That’s because the city’s air quality is usually worst in fall and winter. Only if it improves during those two seasons would it be fair to say the city’s overall air quality is getting better, Huang said.
By Anne Zhang, Shenzhen Daily.