Atmospheric Measurements

In November 2004, a team led by J. William MUNGER (Harvard School of Engineering and Applied Sciences), Michael McELROY and Chris P. NIELSEN (Harvard-China Project), and HAO Jiming (Tsinghua University School of Environment) deployed a permanent observational station for use in atmospheric research, including the China Project's GEOS-CHEM modeling. WANG Yuxuan (Tsinghua University Center for Earth System Science and University of Houston) and WANG Shuxiao (Tsinghua University School of Environment), both alumna of the Harvard China Project, later took over lead responsibilities on the Tsinghua side of the partnership.

The station has made continuous observations of key trace gases, including CO, CO2, O3, SO2, NO/NOy, and black carbon, as well as local meteorological conditions. The station is sited in Miyun, a rural area north of Beijing, to distance it from the influence of individual sources and to measure a variety of conditions as local meteorology shifts, from relatively clean background air to polluted urban plumes. A methane analyzer will soon be added to the station.
 
Researchers have compared or incorporated the measurements of atmospheric species at the Miyun station with emissions estimates and GEOS-Chem modeling, and have conducted research on levels and trends in concentrations of O3, NOX, and BC, CO2:CO ratios, and the effects of control policies on diverse atmospheric pollutants and GHGs.

 

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The China Project's atmospheric research is committed to building observationally validated, fundamental research on the physical and chemical dimensions of China’s atmospheric environment and the emissions that influence it, at local, regional, and global scales. In addition to the observational research described below, it includes modeling research described here and bottom-up emissions research described here.

In November 2004, a team led by J. William MUNGER (Harvard School of Engineering and Applied Sciences, SEAS), Michael McELROY (SEAS and Harvard Department of Earth and Planetary Sciences), and HAO Jiming (Tsinghua University School of Environment) deployed a permanent observational station for use in atmospheric research, including the China Project's GEOS-CHEM modeling activities. Since that time, the station has made continuous observations of key trace gases and local meteorological conditions. Measured species include CO, CO2, O3, SO2, NO/NOy, and black carbon. The station is sited in Miyun, a rural area north of Beijing, to distance it from the influence of individual sources and to measure a variety of conditions as local meteorology shifts, from relatively clean background air to polluted urban plumes. In 2008, WANG Yuxuan (Tsinghua Center for Earth System Science) took over lead responsibilities on the Tsinghua side of the partnership, joined by WANG Shuxiao (School of Environment, Tsinghua University) in 2013. As of 2016, Harvard-Tsinghua measurements at the Miyun station have been sponsored by the Harvard Global Institute, including upcoming addition of a methane (CH4) analyzer. 

A 2008 paper in Atmospheric Chemistry and Physics (ACP) (Wang et al. 2008) used station data and GEOS-Chem to investigate variations of ozone and carbon monoxide in summertime in the Beijing area, contrasting the impacts of monsoonal meteorology in early versus late summer on photochemistry and ozone formation. Wang et al. (2009), in ACP, uses the data record to differentiate how much of reduced ozone levels observed at the station during the Beijing Olympics can be attributed to policy-driven restrictions of emissions, and how much to natural meteorological conditions. Wang et al. (2010a), inTellus B, examines seasonal variations of CO and O3 over 2005-2007.

A number of subsequent papers analyze the observational records of other important species observed at Miyun.

A study led by Wang and Munger (Wang et al. 2010b) in ACP analyzes the rising observed CO2:CO ratio at Miyun, indicating increasing combustion efficiency in China over time that is consistent with the energy efficiency policies of the 11th Five Year Plan. Given the policy relevance, a summary for non-scientists is available at this link hosted by the ChinaFAQs initiative of the World Resources Institute in Washington, DC. 

Following addition of an analyzer of black carbon (BC) with support of Yutaka Kondo of the University of Tokyo, a 2011 paper in the Journal for Geophysical Research (JGR) led by Wang and Kondo (Wang et al. 2011) takes a first look at the record of BC observations at Miyun, comparing it to bottom-up emission estimates of this critical short-lived climate forcing agent, and identifying possible inventory refinements. Another paper in JGRmakes top-down estimates of BC using surface observations, and evaluates the sensitivity to observation representativeness and transport model error (Wang et al. 2013)

A paper in Atmospheric Chemistry and Physics examines the change of sulfate-nitrate-ammonium (SNA) aerosols over China due to anthropogenic emission changes of their precursors (SO2, NOX and NH3) from 2000 to 2015 (Wang et al. 2013).

Acknowledgment: Some of the material summarized here is based on work supported in part by the National Science Foundation under Grants No. ATM-1019134 or ATM-0635548 (indicated by acknowledgments in the papers). Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.

 

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To evaluate the effectiveness of national air pollution control policies, the emissions of SO2, NOX, CO and CO2 in China are estimated using bottom-up methods for the most recent 15-year period (2000–2014). Vertical column densities (VCDs) from satellite observations are used to test the temporal and spatial patterns of emissions and to explore the ambient levels of gaseous pollutants across the country. The inter-annual trends in emissions and VCDs match well except for SO2. Such comparison is improved with an optimistic assumption in emission estimation that the emission standards for given industrial sources issued after 2010 have been fully enforced. Underestimation of emission abatement and enhanced atmospheric oxidization likely contribute to the discrepancy between SO2 emissions and VCDs. As suggested by VCDs and emissions estimated under the assumption of full implementation of emission standards, the control of SO2 in the 12th Five-Year Plan period (12th FYP, 2011–2015) is estimated to be more effective than that in the 11th FYP period (2006–2010), attributed to improved use of flue gas desulfurization in the power sector and implementation of new emission standards in key industrial sources. The opposite was true for CO, as energy efficiency improved more significantly from 2005 to 2010 due to closures of small industrial plants. Iron & steel production is estimated to have had particularly strong influence on temporal and spatial patterns of CO. In contrast to fast growth before 2011 driven by increased coal consumption and limited controls, NOX emissions decreased from 2011 to 2014 due to the penetration of selective catalytic/non-catalytic reduction systems in the power sector. This led to reduced NO2 VCDs, particularly in relatively highly polluted areas such as the eastern China and Pearl River Delta regions. In developed areas, transportation is playing an increasingly important role in air pollution, as suggested by the increased ratio of NO2 to SO2 VCDs. For air quality in mega cities, the inter-annual trends in emissions and VCDs indicate that surrounding areas are more influential in NO2 level for Beijing than those for Shanghai.

Rong Xie, Clive E. Sabel, Xi Lu, Weimo Zhu, Haidong Kan, Chris P. Nielsen, and Haikun Wang. 2016. “Long-term trend and spatial pattern of PM2.5-induced premature mortality in China.” Environment International, 97: 180-186. Publisher's Version Abstract

With rapid economic growth, China has witnessed increasingly frequent and severe haze and smog episodes over the past decade, posing serious health impacts to the Chinese population, especially those in densely populated city clusters. Quantification of the spatial and temporal variation of health impacts attributable to ambient fine particulate matter (PM2.5) has important implications for China's policies on air pollution control. In this study, we evaluated the spatial distribution of premature deaths in China between 2000 and 2010 attributable to ambient PM2.5 in accord with the Global Burden of Disease based on a high resolution population density map of China, satellite retrieved PM2.5 concentrations, and provincial health data. Our results suggest that China's anthropogenic ambient PM2.5 led to 1,255,400 premature deaths in 2010, 42% higher than the level in 2000. Besides increased PM2.5 concentration, rapid urbanization has attracted large population migration into the more developed eastern coastal urban areas, intensifying the overall health impact. In addition, our analysis implies that health burdens were exacerbated in some developing inner provinces with high population density (e.g. Henan, Anhui, Sichuan) because of the relocation of more polluting and resource-intensive industries into these regions. In order to avoid such national level environmental inequities, China's regulations on PM2.5 should not be loosened in inner provinces. Furthermore policies should create incentive mechanisms that can promote transfer of advanced production and emissions control technologies from the coastal regions to the interior regions.

Yu Zhao, Hui Zhong, Jie Zhang, and Chris P Nielsen. 2015. “Evaluating the effects of China's pollution control on inter-annual trends and uncertainties of atmospheric mercury emissions.” Atmospheric Chemistry and Physics, 15: 4317–4337. Publisher's Version Abstract
China's atmospheric mercury (Hg) emissions of anthropogenic origin have been effectively restrained through the national policy of air pollution control. Improved methods based on available field measurements are developed to quantify the benefits of Hg abatement through various emission control measures. Those measures include increased use of flue gas desulfurization (FGD) and selective catalyst reduction (SCR) systems for power sector, precalciners with fabric filter (FF) for cement production, machinery coking with electrostatic precipitator (ESP) for iron and steel production, and advanced manufacturing technologies for nonferrous metal smelting. Declining trends in emissions factors for those sources are revealed, leading to a much slower growth of national total Hg emissions than that of energy and economy, from 679 in 2005 to 750 metric tons (t) in 2012. In particular, nearly half of emissions from the above-mentioned four types of sources are expected to be reduced in 2012, attributed to expansion of technologies with high energy efficiencies and air pollutant removal rates after 2005. The speciation of Hg emissions keeps stable for recent years, with the mass fractions of around 55, 39 and 6% for Hg0, Hg2+ and Hgp, respectively. The lower estimate of Hg emissions than previous inventories is supported by limited chemistry simulation work, but middle-to-long term observation on ambient Hg levels is further needed to justify the inter-annual trends of estimated Hg emissions. With improved implementation of emission controls and energy saving, 23% reduction in annual Hg emissions for the most optimistic case in 2030 is expected compared to 2012, with total emissions below 600 t. While Hg emissions are evaluated to be gradually constrained, increased uncertainties are quantified with Monte-Carlo simulation for recent years, particularly for power and certain industrial sources. The uncertainty of Hg emissions from coal-fired power plants, as an example, increased from −48 ~ +73% in 2005 to −50 ~ +89% in 2012 (expressed as 95% confidence interval). This is attributed mainly to swiftly increased penetration of advanced manufacturing and pollutant control technologies. The unclear operation status or relatively small sample size of field measurements on those technologies results in lower but highly varied emission factors. To further confirm the benefits of pollution control polices with reduced uncertainty, therefore, systematic investigations are recommended specific for Hg pollution sources, and the variability of temporal trends and spatial distributions of Hg emissions need to be better tracked for the country under dramatic changes in economy, energy and air pollution status.
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