Pudong, Chongming boast best air quality

The Pudong New Area and Chongming District, with their proximity to the sea, enjoyed the best air quality in Shanghai as recorded in the last two years.  

The Pudong New Area and Chongming District record the lowest density of PM2.5 particle in 2016 and 2017.

The Pudong New Area and Chongming District enjoyed the best air quality in the past two years, while Jiading and Qingpu districts recorded the highest average level of the dangerous pollutant PM2.5 particle due to their geographic location.

According to statistics made available by the Shanghai Environmental Monitoring Center, the Pudong New Area reported the lowest average density for PM2.5 compared with other districts in 22 out of the 24 months in 2016 and 2017. It was followed by Chongming District, which reported the lowest or second-lowest density of PM2.5 in 13 months in the past two years.

Qingpu and Jiading districts had the worst figures. Qingpu’s average density of PM2.5 was the highest in Shanghai in 17 months. It was followed by Jiading, which reported the highest or second-highest density of PM2.5 in 21 months in the past two years.

According to experts from Shanghai Environmental Monitoring Center, the geographic location of Qingpu and Jiading, located in the northwest part of Shanghai, played a crucial role in the situation.

Pollutants carried into Shanghai from neighboring provinces by the northwesterly wind have often been the cause of air pollution. Qingpu and Jiading, including Songjiang and Baoshan districts, are the “frontier” provinces when the pollutants enter Shanghai.

Also, when the east wind brings cleaner air from the sea into Shanghai, it takes even longer for the pollutants to disperse from the northwestern districts. Pudong and Chongming, which are closer to the sea, enjoy comparatively less pollution because of their location.

Qingpu District boasts 57 square kilometers of lake — about 78.6 percent of Shanghai’s total amount. The humidity of the area also created difficulty in the dispersion of pollutants.

However, there was some exception last summer, as Chongming reported the highest average density of PM2.5 in July and August 2017. In July, the average density was 41 micrograms per cubic meter, 8 micrograms higher than the city’s average of 33. In August, the figure was 36 micrograms per cubic meter, higher than the city’s average of 31.

According to experts, heat can often become the catalyst in the forming of air pollutant.

“Nitrogen oxide, hydrocarbon and volatile organic compounds created by local dischargers can form pollutants and raise the density of PM2.5 more quickly under the help of heat in summer,” said Duan Yusen, an engineer of Shanghai Environmental Monitoring Center.

But Duan said it didn’t seem to be the cause of the air pollution in Chongming, which doesn’t own a large amount of polluting industry or sources.

The center’s expert team considered regional transport of air pollutants the major cause of the fluctuation of Chongming’s air quality last summer.

The center recorded at least two rounds of air pollution last summer at the north part of the Yangtze River Delta region, which affected neighboring Jiangsu Province and Chongming, but did not affect the rest part of Shanghai.

Air pollutants from overseas can also “hide” in air mass covered by heavy clouds over the sea, which might affect the air quality in Chongming and the eastern part of the city when the clouds reach the shore. But generally, the coastal areas still enjoy better air quality through the year.