PM2.5 Falls While Ozone Rises Say Harvard & NUIST

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A recent study published in conjunction with the Nanjing University of Information Science and Technology (NUIST) has found that, despite the fact PM2.5 is falling, surface ozone pollution is on the rise.

The study, that appears in “Proceedings of the National Academy of Sciences” (PNAS), was contributed to by NUIST and Harvard’s John A. Paulson School of Engineering and Applied Sciences (SEAS).

Over the last 5 years, 1,000 air-quality monitoring stations have been collecting much-needed environmental data from across China. Since the government launched its war on air pollution 5 years ago, the country’s worrying PM2.5 (Particulate Matter 2.5) is said to have dropped by 40 percent. Yet, researchers now say ground-level ozone pollution is worsening.

The oxidation of Volatile Organic Compounds (VOCs) forms radicals, which, in turn, ignites a reaction between oxides and nitrogen, producing ozone when in sunlight. Both are the product of fossil fuel combustion and industrial sources.

Speaking exclusively with The Nanjinger, Dr. Li Ke, a researcher from Harvard University, commented, “To reduce PM2.5 is the first thing we should do, since PM2.5 is more harmful than surface ozone… But in consideration of the increasing ozone trend reported by our study, a joint action should be taken to reduce public exposure”.

The finding to which Dr. Li is referring is the discovery that particulate matter actually acts like a sponge for the free radicals needed to produce ozone. Particulate Matter essentially sucks the free radicals up, preventing ozone from forming.

“The most important cause of the increasing ozone in [the] NCP [North China Plain] appears to be the decrease in PM2.5, slowing down the sink of hydroperoxy radicals and thus speeding up ozone production”, research published by the PNAS reveals. “Drastic air pollution control in China since 2013 has achieved sharp decreases in fine particulate matter (PM2.5), but ozone pollution has not improved”.

“This study highlights the importance of reducing ozone precursors, while the priority of air quality improvement is to control particulate pollution”, Dr. Li said. “I think it [the finding] will help the government to better understand current air-pollution issues. I am sure they will [provide funding support], because air pollution issues in China still have a long way to go”.

Dr. Li finished his PhD at the Chinese Academy of Sciences where he was working on air pollution. “I started with this project because we have observed an increasing trend of surface ozone in recent years in China, which is a bad sign for the public. Then we tried to do something”, said Li.

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Renée Gray Beaumont
As an Australian journalist living in Nanjing for many years, Renée Gray Beaumont has a background in research, print and online publishing, taking great pleasure in discovering more about Nanjing with every article. 作为在南京居住多年的澳大利亚新闻工作者,Renee Gray Beaumont 有着调研以及印刷品和线上出版物的工作背景。她总是乐于在每篇文章里发现关于南京的内容。