China’s war on particulate air pollution is causing more severe ozone pollution

From Eurekalert!

Public Release: 2-Jan-2019

PM 2.5 pollution is falling but ground-level ozone pollution is on the rise

Harvard John A. Paulson School of Engineering and Applied Sciences

In early 2013, the Chinese government declared a war on air pollution and began instituting stringent policies to regulate the emissions of fine particulate matter, a pollutant known as PM 2.5. Cities restricted the number of cars on the road, coal-fired power plants reduced emissions or were shuttered and replaced with natural gas. Over the course of five years, PM 2.5 concentrations in eastern China have fallen nearly 40 percent.

The number of air quality monitoring stations across the country has grown to over 1,000, collecting unprecedented amounts of environmental data. Sifting through that data, researchers from the John A. Paulson School of Engineering and Applied Sciences (SEAS) and the Nanjing University of Information Science & Technology (NUIST), found something surprising: While PM 2.5 pollution is falling, harmful ground-level ozone pollution is on the rise, especially in large cities.

As it turns out, when it comes to the war on air pollution, chemistry is a formidable foe.

Ozone is the main ingredient in smog and has been studied since it began choking cities in the U.S. in the early 1950s. “Ozone is formed through a series of chemical reactions, starting with the oxidation of volatile organic compounds (VOCs). This reaction forms chemical radicals, which drives reactions among oxides of nitrogen (NOx) and VOCs to produce ozone in the presence of sunlight. Both NOx and VOCs are emitted from fossil fuel combustion, and VOCs can also be emitted from industrial sources.

The researchers from SEAS and NUIST found that particulate matter acts like a sponge for the radicals needed to generate ozone pollution, sucking them up and preventing them from producing ozone.

“There was so much particulate matter in Chinese cities that it stunted the ozone production,” said Daniel Jacob, the Vasco McCoy Family Professor of Atmospheric Chemistry and Environmental Engineering, and co-corresponding author of the study.

But the rapid reduction of PM 2.5 dramatically altered the chemistry of the atmosphere, leaving more radicals available to produce ozone.

“We haven’t observed this happening anywhere else because no other country has moved this quickly to reduce particulate matter emissions,” said Jacob. “It took China four years to do what took 30 years in the U.S.”

Despite this rapid reduction, China still has a long way to go to meet its air quality goals.

“As PM 2.5 levels continue to fall, ozone is going to keep getting worse,” said Ke Li, a postdoctoral fellow at SEAS and first author of the study.

“Results from this study suggest that extra efforts are needed to reduce NOx and VOC emissions in order to stem the tide of ozone pollution”, said Professor Hong Liao at NUIST who is the co-corresponding author of this work.

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This research was also co-authored by Lu Shen, Qiang Zhang, and Kelvin H. Bates.

It was supported by NUIST through the Harvard-NUIST Joint Laboratory for Air Quality and Climate (JLAQC).

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57 thoughts on “China’s war on particulate air pollution is causing more severe ozone pollution

  1. I was in Beijing, Chengdu and Shanghai on a series of trips during 2011 -2013 and the air was brutally thick. Chengdu is in a topographic “bowl” and during the course of the day it simmply filled up with brown smog. Poor quality fuel for the smoky mopeds and I suppose cars burned the same stuff. The last time I had experienced this was in London and Los Angeles in the 1960s. The China smog seemed the worst by far (London second). I think the existence of old puffing factories made the difference in China and the horrid motorbikes.

    • You are right that all that old motorbikes was a huge problem. Most of them had two-stroke engines which are the worst concerning pollution.

      The good news is that it has all changed, at least in the big cities you mention. Almost all motorbikes are now electric. They are noiseless and pollution free.

        • Or nuclear, hydro, wind and solar perhaps.
          Gas is also virtually pollution free.

          Well, surely most of China’s power comes from coal so some pollution comes from that, but that is well cleansed and emitted from tall chimneys outside the cities. For the city air, the pollution from power plants is negligible compared to the pollution emitted by vehicles directly in the city streets

    • Sao Palo and Rio are particularly bad, or were when I was there, as they used high ethanol gasoline without emission controls. The acetaldehyde smell was all around those areas.

      In China, air pollution outside of the major cities (of course a village there might be 2 million people) is actually not that bad. Flying over, it is generally easy to see all of the power plants on a “clear” day because of their water vapor, NOx and SOx emissions.

  2. “Ozone is formed through a series of chemical reactions, starting with the oxidation of volatile organic compounds (VOCs). This reaction forms chemical radicals, which drives reactions among oxides of nitrogen (NOx) and VOCs to produce ozone in the presence of sunlight.

    Anthropogenic drivers of 2013–2017 trends in summer surface ozone in China

    Paradoxical? Because CFCs are VOCs. According to regulatory theory, free radicals from the action of sunlight on CFCs destroy ozone; causing the hole in the ozone. China is the largest CFC emitter. Killing ozone was the excuse they used to ban CFCs. The ozone ban was to save us all from skin cancer. Now radicals are doing the opposite.

    The mechanism described is:

    Drastic air pollution control in China since 2013 has achieved sharp decreases in fine particulate matter (PM2.5), but ozone pollution has not improved. After removing the effect of meteorological variability, we find that surface ozone has increased in megacity clusters of China, notably Beijing and Shanghai. The increasing trend cannot be simply explained by changes in anthropogenic precursor [NOx and volatile organic compound(VOC)] emissions, particularly in North China Plain (NCP). The most important cause of the increasing ozone in NCP appears to be the decrease in PM2.5, slowing down the sink of hydroperoxy radicals and thus speeding up ozone production. Decreasing ozone in the future will require a combination of NOx and VOC emission controls to overcome the effect of decreasing PM2.5.

    The tiny wikipedia article on hydroperoxy (aka superoxide) says it destroys ozone. But wait a minute!, isn’t this hydroperoxy radical also a pollutant? Indeed it must be because it is a free radical, and all such free radicals in surface air are pollutants.

    • Did the USA not figure out the problem, the solution, develop the systems, and provide the money to clean up the air?

      Then what happened?

    • Take note!

      Ignorant & also insulting to the people that did the work — the US & Europe had to develop the technology from scratch. China has the developed technology already at hand.

    • Some things move quickly there because the opposition can be executed rather quickly, at least the government’s opposition.

      Their prosecutors are much better than we have here too as evidenced by their 99.9% conviction rate. And unlike here, prisoner’s organs are not wasted.

    • griff January 5, 2019 at 8:12 am
      Hello griff, re-read the article. They have made progress but have not achieved what the United States accomplished.
      And as noted we boot strapped ourselves up without help and created the tech used.
      China still has a long, long way to go.
      “PM 2.5 concentrations in eastern China have fallen nearly 40 percent.”

      The world really should thank us, for as always leading the way when something needs to be done.

      michael

    • And China continued unabated for those 30 years after the pollution was identified until they used available technology developed by the West to stop the pollution. Is that what you mean?

    • Which is WHY the US and other developed countries do not “owe” the developing world ANYTHING for their fossil fuel emissions of the past. It is the developed nations that, in creating the modern world, provide the pathways and technology for the ROW at negligible cost of discovery, invention, development, engineering, testing, maintaining, etc. 90% of the ROW has no capability to improve their own lot without the developed world’s technology.

      Saying “It took China four years to do what took 30 years in the U.S.” is no different than comparing today’s computing capabilities with what was available 30 years ago. Not close. China (and the ROW) didn’t contribute diddly-squat to any of that development yet for a pittance gets the modern capability of powerful computing platforms. In nearly every possible sector of the modern world the situation is the same. We owe the rest of the world NOTHING for our past emissions. Perhaps the opposite.

  3. It may be time for a better understanding of smog. Most of the information coming up on internet searches is short of specifics beyond smog is comprised of a number of chemicals including ozone, which affects breathing of some more than others and which is desirable for the upper atmosphere.

  4. I do struggle with the chemistry of this, not similar to (haha conventional) ‘ozone hole’ chemistry

    I cannot see how VOCs would produce ozone – ozone being very angry sort of stuff, desperate to oxidise anything it comes near and VOCs being equally desperate to *be* oxidised.
    They should neutralise each other to CO2 and water.

    The main example being a forest of conifer trees. They produce vast amounts of VOC, hence why they smell ‘nice’.
    But why? Those VOCs took a lot of energy & resource to produce yet the trees simply seem to throw the stuff away. Madness and then, according to the chemistry of photochemical smog, conifer forests *should* be constantly engulfed by photochemical smog – but they aren’t. are they????

    Is it possible the conifers release their VOCs in order to ‘mop up’ any ozone there is floating around.
    It is VERY damaging stuff and any time that sunlight containing any UV component meets diatomic oxygen, ozone is the result.

    Nitrogen oxide – comes from burning anything in an oxygen/nitrogen gas mixture but the amount produced depends on the flame temperature – high temperatures produce more, much more.

    Certainly with any UV around, these NOx might/will create ozone.
    How does it then average out?
    ….We now have high efficiency car engines running higher compression ratios and high flame temperatures (= lots of NOx) but also a lot less escaped & unburnt fuel (= a lot less VOC – is gasoline not a VOC?)
    Thus and without an attempt to control the NOx, there will be a lot more ozone around – more created and less VOC to soak it up, as the forest does with its VOC emissions.

    Not easy is it?
    Something does seem really rather wrong with their chemistry – and the resultant fix they’ll come up with.
    (It’ll be a new tax of course, no need to stress about that bit)

    What got me going was how an extremely polluted East End of London, 150 years ago, was cleaned up and made liveable (again) by the simple measure of creating a sizeable park right in the centre of the polluted zone. Name of Victoria Park, east of Hackney. Still there and very much alive.

    How did the park clean up the area? If not by releasing plant derived VOCs and pulling the highly oxidising and irritant species (O3 and NOx) out of the local air?

    Would that be their solution, allow or put *more* VOC into the city-centre air – not less as current thinking suggests (because they have the chemistry back-to-front)

    • PoN, you asked: “Madness and then, according to the chemistry of photochemical smog, conifer forests *should* be constantly engulfed by photochemical smog – but they aren’t. are they????

      It is reported that the Smoky Mountains got their name, long before the industrial revolution in the US, from the photochemical smog that for a very long time blanketed this region. The Cherokee called them shaconage, (shah-con-ah-jey) or “place of the blue smoke” (http://www.gsmnp.com/great-smoky-mountains-national-park/history/ )

    • You Peta, Dr. Bob, Dresler, Springer are offering ideas about the formation of ozone at ground level.
      This was explained and published quite a while ago by Haagen-Smit, a professor at Cal Tech.
      https://en.wikipedia.org/wiki/Arie_Jan_Haagen-Smit
      Many articles were then published about how the photo-chemical smog and ozone formation came about in Los Angeles.
      Yes three things are needed: unsaturated short hydrocarbons (i.e. butadiene etc, volatile hydrocarbons (VOCs)), nitrogen dioxide (NO2) and energy supplied by the sun to make the reactions going and form ozone.
      What is happening in China is clearly a reduction of particulate pollution, not only PM 2.5. This will let more sunlight in, perfect. Then we have more cars: more VOCs, more NO2, perfect. More ozone produced. We have seen the same in several cities in the USA. Ozone has become a problem.

  5. Not mentioned in the article is the natural sources of hydrocarbons from plant life. Many of these are reactive terpenes which have unsaturated carbon bonds (double bonds) that are the initiator of free radical reactions. Saturated hydrocarbons (Methane, Ethane, Propane, etc) have bond dissociation energies in the 105 to 95 kcal/mol range whereas propylene (with one double bond) has a C-H dissociation energy of 87 kcal/mol. This makes olefins far more reactive in free radical propagation reactions and therefore more likely to produce NOx.
    In SoCal, a natural bowl, fully 50% of the hydrocarbon in the air were from plant life in the 1970’s, so it is impossible to completely remove smog from this area. Other natural bowl will behave similarly. Thus the blue haze over the “Smoky Mountains”, and other site with high natural sources of hydrocarbons, especially unsaturated ones like terpenes.

  6. Still, it would not matter much, this site of skeptics here is in full denial, as far as I can tell…
    The best ever and most lush ever denial, happens to be that of skeptics, in me book…
    please keep bitching around in the crossroads, of denial prostitution…skeptics!

    Harsh, yes, maybe yes, but who ever jumps for self castration must know that it is what it is, a castration…
    Please do wake up, fully castrated ones…

    With all the beauty and all beauty offered,this site of skeptics here happens to be in full denial, as far as I can tell…please do try and keep it up fellas. You all too clever for your on good.

    cheerio.

    cheers

  7. Nothing new under the sun… Chinese environment management, in 1958, Mao decided to eradicate sparrows blamed by concerned scientists to excessively feed on rice crops.

    Sparrows were driven to near extinction.

    Rather than being increased, rice yields after the campaign were substantially decreased since bugs destroyed crops as a result of the absence of natural predators.

    Another example, modern aircraft air conditioning is an incredible maze of recycling filters and catalytic ozone converters.

    It might save fuel, however, back then when smoking was allowed, cabin pressurization air was renewed and not vastly recycled.

    Cabins are now the sickest place to be. For real.

    Some experts blame the reduction of ozone by the ozone converters. Ozone is about the only fast reacting bactericide we had for free and at will when cabin air was massively renewed at high altitudes.

  8. As regards the above article’s statement: “. . . something surprising: While PM 2.5 pollution is falling, harmful ground-level ozone pollution is on the rise, especially in large cities.” Well, I would say the only identified part of the cause.

    What they missed is that PM 2.5 particulates are a major source of cloud condensation nuclei, and that “thick” clouds are a major absorber of solar UV radiation, the major driver of photochemical smog production. For example, clouds with optical thickness of 0.80 to 0.85 absorb 80-90% of incoming solar UV radiation (ref: https://www.researchgate.net/figure/Calculated-UV-reduction-functions-due-to-clouds-C-T-as-a-function-of-the-cloud-optical_fig1_240487654 ).

    Make the clouds disappear and you automatically increase solar-driven smog production. I can’t explain why the researchers from SEAS and NUIST overlooked this effect . . . it does not appear that they corrected their data for changes in percentage of thick cloud cover during the study period.

  9. Illusions about China should now end with the arrest and detention of 12 Canadians.

    This is state initiated terrorism, plain and simple. It is hostage taking to try and force Canada to release a Chinese executive well connected to the communist party.

    China has made very serious threats against Canada over thus matter. Threats that they have now shown they are perfectly willing to put into action.

    Meanwhile the TrueDope government continues to try and appease China which simply encourages them to further bully Canada into submission.

    Anyone that thinks Climate Change is the number 1 problem they face should think long and hard about the men and women that have died over the centuries to win you the right to freedom.

    The biggest danger is not climate change. It is the loss of your right to freedom.

    • “China has made very serious threats against Canada over thus matter. Threats that they have now shown they are perfectly willing to put into action.”

      This is serious business for the Chinese leadership. They are about to be exposed for spying on nations around the world through the use of Chinese Telecom giants who install telecommunications hardware in various countries but don’t tell the countries that the Chinese hardware has the capability of listening in on the communications of the whole nation and everybody in it.

      That’s why they want Meng Wanzhou, Huawei CFO, released. She knows all their secrets.

      Yes, the Chinese leadership is showing its true face in this incident. They are predators who are not to be trusted.

  10. You Peta, Dr. Bob, Dresler, Springer are offering ideas about the formation of ozone at ground level.
    This was explained and published quite a while ago by Haagen-Smit, a professor at Cal Tech.
    https://en.wikipedia.org/wiki/Arie_Jan_Haagen-Smit
    Many articles were then published about how the photo-chemical smog and ozone formation came about in Los Angeles.
    Yes three things are needed: unsaturated short hydrocarbons (i.e. butadiene etc, volatile hydrocarbons (VOCs)), nitrogen dioxide (NO2) and energy supplied by the sun to make the reactions going and form ozone.
    What is happening in China is clearly a reduction of particulate pollution, not only PM 2.5. This will let more sunlight in, perfect. Then we have more cars: more VOCs, more NO2, perfect. More ozone produced. We have seen the same in several cities in the USA. Ozone has become a problem.

  11. Propaganda and nothing more. The article basically says China caught up with the rest of the world for particle emissions, finally.

  12. About 70 million years ago the Indo-Austrialian plate began subducting beneath the Eurasian plate closing the eastern Tethys ocean (and subducting it into the mantle) about 50 million years ago. This closure rose the Himalya-Karakoram, Pamir-Alay and the Kunlun Mountains with the Plateau causing a global shifting of air circulation both near-surface up to the steering-currents at the Tropo-Stratosphere Boundary by the high elevations. With an average elevation of about 4.5 kilometers the Plateau and its even higher fronting mountain ranges effectively block circulation associated with the modern monsoonal patterns of the Arabian Sea and Bay of Bengal. Therefore, there is absolutely nothing that the “Genius” Ecosystem “Experts” can do about this except cry for more Federal Funding !

    Ha ha

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