Nocturnal pollution is a rising public health threat in China

According to a new study led by an international team of scientists, China is currently a nighttime “hotspot” for the production of nitrate radicals (PNO₃) that may have a significant impact on health-threatening levels of ozone and fine particulates (PM_2.5) in the atmosphere.

While the United States and Europe experienced a decline in nocturnal production of NO₃, China has recently experienced a rapid increase in these pollutants. The experts believe that this may have serious implications not only for China, but also for other developing countries such as India.

“Nitrogen oxides derived from combustion and natural sources are reactive gases that regulate the formation of key air pollutants including both ozone (O₃) and PM_2.5. Nocturnal oxidation driven by nitrate radicals is an important, but poorly understood, process in atmospheric chemistry – we must understand this better, if we are to formulate effective global pollution mitigation strategies and understand the influence of nitrogen oxides on air quality and climate,” said study co-author Zongbo Shi, an expert in Aerosol Chemistry and Physics at the University of Birmingham.

The analysis revealed that the current production of NO₃ radicals increased significantly in three megacity clusters (the North China Plain, the Yangtze River Delta, and the Pearl River Delta), while in eight major Chinese cities – Beijing, Shanghai, Guangzhou, Chengdu, Xi’an, Jinan, Zhengzhou and Shijiazhuang – it is currently comparable to that in Los Angeles in the 1990s, and keeps increasing. Moreover, if ozone pollution keeps rising, nighttime oxidation in China will most likely increase further, even if NO₃ emissions are curbed.

Considering the fact that much lower levels of NO₃ radicals in both U.S. and Europe have been shown to exert significant impacts on particulate nitrate and organic aerosol formation in those regions, the scientists believe that NO₃ radical chemistry may play a more critical role in atmospheric oxidation and thus aggravate both O₃ and PM_2.5 pollution in China very soon, posing public health problems in this country, as well as abroad.

The study is published in the journal Nature Geoscience.

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By Andrei Ionescu, Earth.com Staff Writer

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