A talk by Herman Pontzer that complements The Exercise Paradox in the current issue of Scientific American on human energy expenditure. We're very odd as apes go. Among other things exercise is very poorly coupled with weight loss unless you do enormous amounts. Of course exercise is very important, but for a multitude of other reasons.
Public opinion in China was choked with depression, fear and anger, as large swaths of the country remained shrouded in dangerously high levels of smog and the Beijing government prolonged its yellow alert till Saturday.
Wednesday was the fifth day since the environmental department issued an orange alert for smog in Beijing. Highways have been shut down, flights canceled, and construction work and some vehicles are restricted in order to ease pollution.
However, economic losses are meager compared with torrential waves of complaints by disgruntled city dwellers.
The blurred skyline and "disappeared buildings" used to be butt of jokes for people previously, and mocking pictures and bitter banter was popular online. The sentiment changed noticeably during this round of smog. Having experienced repeated hits of the smog, a lot of people know it's not a laughing matter and wonder if there is a cure to this problem or if they will have to live with it for the rest of their lives.
Somehow, sulfur dioxide, a common byproduct of coal-burning, was getting turned into sulfate, very quickly.
"I was doing some work in my lab to see if I can reproduce some of the things my colleagues see in China," Zhang explains. "What we found out is that the traditional ways that people make sulfate didn't work," or worked too slowly.
They had another way to try to recreate the haze — combining nitrogen dioxide and sulfur dioxide in a humid environment, which could produce sulfates. Both chemicals are produced by burning coal, so it seemed like "a very natural candidate" to explain what was happening in China.
But the result was extremely acidic. And as soon as the particles got too acidic, the reaction stopped: "The product would basically drive the reaction backward," Zhang explains.
Here, there were two separate breakthroughs. One explained the situation in China: The team found that ammonia, present in the atmosphere because of agricultural activity, could neutralize the acidity without stopping the creation of sulfates.
Persistent sulfate formation from London Fog to Chinese haze
Gehui Wanga,b,c,d,e,1, Renyi Zhangc,d,f,2, Mario E. Gomezc,d,g, Lingxiao Yangc,h, Misti Levy Zamorac, Min Huf, Yun Linc, Jianfei Pengc,f, Song Guoc,f, Jingjing Menga,b,i, Jianjun Lia,b, Chunlei Chenga,b,i, Tafeng Hua,b, Yanqin Rena,b,i, Yuesi Wangj, Jian Gaok, Junji Caoa,b, Zhisheng Ana,b,l, Weijian Zhoua,b,m, Guohui Lia,b, Jiayuan Wanga,b,i, Pengfei Tianc,n, Wilmarie Marrero-Ortizc,d, Jeremiah Secrestc,d, Zhuofei Duf, Jing Zhengf, Dongjie Shangf, Limin Zengf, Min Shaof, Weigang Wangc,o,p, Yao Huanga,b,i, Yuan Wangq, Yujiao Zhuc,r, Yixin Lic, Jiaxi Huc, Bowen Panc, Li Caic,s, Yuting Chenga,b,i, Yuemeng Jic,t, Fang Zhangc,l, Daniel Rosenfeldc,u, Peter S. Lissc,v, Robert A. Ducec, Charles E. Kolbc,w, and Mario J. Molinax,2 aState Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China; bKey Laboratory of Aerosol Chemistry and Physics, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China; cDepartment of Atmospheric Sciences, Texas A&M University, College Station, TX 77843; dDepartment of Chemistry, Texas A&M University, College Station, TX 77840; eSchool of Geographic Sciences, East China Normal University, Shanghai 200062, China; fState Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China; gDepartment of Chemistry and Biochemistry, Florida International University, Miami, FL 33199; hSchool of Environmental Science and Engineering, Shandong University, Jinan 250100, China; iUniversity of Chinese Academy of Sciences, Beijing 100049, China; jInstitute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China; kChinese Research Academy of Environmental Sciences, Beijing 100000, China; lBeijing Normal University, Beijing 100875, China; mXi’an Jiaotong University, Xi'an 710049, China; nKey Laboratory for Semi-Arid Climate Change of the Ministry of Education, College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China; oState Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China; pBeijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China; qJet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91125; rKey Laboratory of Marine Environmental Science and Ecology, Ministry of Education, Ocean University of China, Qingdao 266100, China; sSchool of Electrical Engineering, Wuhan University, Wuhan 430072, China; tSchool of Environmental Science and Engineering, Institute of Environmental Health and Pollution Control, Guangdong University of Technology, Guangzhou 510006, China; uProgram of Atmospheric Sciences, Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel; vSchool of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, United Kingdom; wAerodyne Research, Inc., Billerica, MA 01821-3976; xDepartment of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093 Contributed by Mario J. Molina, October 9, 2016 (sent for review July 8, 2016; reviewed by Zhanqing Li and Sasha Madronich)
Significance Exceedingly high levels of fine particulate matter (PM) occur frequently in China, but the mechanism of severe haze formation remains unclear. From atmospheric measurements in two Chinese megacities and laboratory experiments, we show that the oxidation of SO2 by NO2 occurs efficiently in aqueous media under two polluted conditions: first, during the formation of the 1952 London Fog via in-cloud oxidation; and second, on fine PM with NH3 neutralization during severe haze in China. We suggest that effective haze mitigation is achievable by intervening in the sulfate formation process with NH3 and NO2 emission control measures. Hence, our results explain the outstanding sulfur problem during the historic London Fog formation and elucidate the chemical mechanism of severe haze in China.
Abstract Sulfate aerosols exert profound impacts on human and ecosystem health, weather, and climate, but their formation mechanism remains uncertain. Atmospheric models consistently underpredict sulfate levels under diverse environmental conditions. From atmospheric measurements in two Chinese megacities and complementary laboratory experiments, we show that the aqueous oxidation of SO2 by NO2 is key to efficient sulfate formation but is only feasible under two atmospheric conditions: on fine aerosols with high relative humidity and NH3 neutralization or under cloud conditions. Under polluted environments, this SO2 oxidation process leads to large sulfate production rates and promotes formation of nitrate and organic matter on aqueous particles, exacerbating severe haze development. Effective haze mitigation is achievable by intervening in the sulfate formation process with enforced NH3 and NO2 control measures. In addition to explaining the polluted episodes currently occurring in China and during the 1952 London Fog, this sulfate production mechanism is widespread, and our results suggest a way to tackle this growing problem in China and much of the developing world.