Atmospheric Emissions

Emission inventories are a fundamental input into air quality modeling and analyses. The Harvard-China Project recruited postdocs from Tsinghua University to develop comprehensive bottom-up emission inventories for its interdisciplinary initiatives and to apply them in analyses of emission trends, uncertainties, and control policies. It now collaborates with some of these research alumni back in China, led by ZHAO Yu and WANG Haikun of the Nanjing University School of Environment, to improve and apply emission inventories from urban to national scales for a variety of research objectives.

Click "More Publications" below to see a full list of publications supported by the Harvard-China Project in this research area. 
 
Without accurate emission profiles of relevant chemical species located in a sufficiently fine spatial distribution, it is impossible to simulate atmospheric concentrations and fluxes accurately. This is an essential ingredient to conduct simulations that can be confirmed by observations and used for analysis of pollution control options. In general, the emissions of each species by sector and region are calculated based on activity levels (energy consumption or industrial production level), unabated emission factors, and the removal efficiencies of applicable emission control technologies. The unabated emission factors are expressed as the mass of emitted pollutant per unit fuel combusted, or per unit industrial production, prior to any emission control.
 
Also contributing to emissions research as recent visiting scholars at the Project have been WANG Shuxiao (Tsinghua University) and YANG Qing (Huazhong University of Science and Technology). The emissions research, complemented by other Project research on atmospheric transport and chemistry and atmospheric field observation, also serve as a central element of China Project’s integrated cost-and-benefit assessments of emission control and energy policies in China.

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Acknowledgment: Some of the papers cited here are based on work supported 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 (NSF).

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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.

Yanyang Mei, Qingfeng Che, Qing Yang, Christopher Draper, Haiping Yang, Shihong Zhang, and Hanping Chen. 2016. “Torrefaction of different parts from a corn stalk and its effect on the characterization of products.” Industrial Crops and Products, 15 December, 92: 26-33. Publisher's Version Abstract

Torrefaction of biomass can reduce its undesirable properties for the subsequent thermochemical application. After separating a Chinese corn stalk into four parts (leaf, stem, root, and cob), torrefaction was performed at temperatures of 200, 250, and 300 °C respectively. The structural and components differences of various parts were analyzed, along with the solid, gas, and liquid products. The study showed that the root was the most sensitive to heat and the cob showed the biggest increase in CO2 and CO yields with the increase temperature, due to their different content of hemicellulose and cellulose. The torrefaction temperature of 250 °C was especially significant for the formation of acids. Liquid product from the leaf was simpler in composition and lower in yield due to higher content of organic extractives and ash. Generally, various parts have different torrefaction properties due to the differences in chemical composition and cellular structure. And with the thermochemical application of biomass were more widely used in the chemical industry especially fine chemical industry, screening and classification may be necessary.

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