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空气污染、温室气体与气候

Jin-Tai Lin, Daeok Youn, Xin-Zhong Liang, and Donald J. Wuebbles. 2008. “Global model simulation of summertime U.S. ozone diurnal cycle and its sensitivity to PBL mixing, spatial resolution, and emissions.” Atmospheric Environment, 41, 36, Pp. 8470-8483. Publisher's VersionAbstract
Simulation of summertime U.S. surface ozone diurnal cycle is influenced by the model representation of planetary boundary layer (PBL) mixing, spatial resolution, and precursor emissions. These factors are investigated here for five major regions (Northeast, Midwest, Southeast, California, and Southwest) by using the Model for Ozone And Related chemical Tracers version 2.4 (MOZART-2.4), with important modifications, to conduct sensitivity experiments for summer 1999 with three PBL mixing schemes, two horizontal resolutions and two emissions datasets. Among these factors, the PBL mixing is dominant. The default non-local scheme well reproduces the observed ozone diurnal variation, where the timing for the afternoon maximum and the morning minimum is within 1 h of the observed; biases for the minimum are less than 5 ppb except over the Southeast; and the ozone maximum–minimum contrast (OMMC) is within 10 ppb of observations except for the overprediction by 18.9 ppb over the Northeast. In contrast, the local scheme significantly overestimates the OMMC by 10–34 ppb over all regions as ozone and precursors are trapped too close to the ground. On the other hand, the full-mixing assumption underestimates the OMMC by 0–25 ppb, except over the Northeast, as the nighttime ozone decline is greatly underpredicted. As compared to PBL mixing, the effects of horizontal resolutions and precursor emissions being used are smaller but non-negligible. Overall, with the non-local mixing scheme, relatively high horizontal resolution (∼1.1°) and updated emissions data, the modified MOZART is capable of simulating the main features of the observed ozone diurnal cycle.

This paper identifies improvements in representation of the boundary layer applicable to the Project's atmospheric model of China.

Yu Zhao, Jie Zhang, and Chris P Nielsen. 2013. “The effects of recent control policies on trends in emissions of anthropogenic atmospheric pollutants and CO2 in China.” Atmospheric Chemistry and Physics, 13, Pp. 487-508. Publisher's VersionAbstract

To examine the effects of China’s national policies of energy conservation and emission control during 2005–2010, inter-annual emission trends of gaseous pollutants, primary aerosols, and CO2 are estimated with a bottom-up framework. The control measures led to improved energy efficiency and/or increased penetration of emission control devices at power plants and other important industrial sources, yielding reduced emission factors for all evaluated species except NOx. The national emissions of anthropogenic SO2, CO, and total primary PM (particulate matter) in 2010 are estimated to have been 89%, 108%, and 87% of those in 2005, respectively, suggesting successful emission control of those species despite fast growth of the economy and energy consumption during the period. The emissions of NOx and CO2, however, are estimated to have increased by 47% and 43%, respectively, indicating that they remain largely determined by the growth of energy use, industrial production, and vehicle populations. Based on application of a Monte-Carlo framework, estimated uncertainties of SO2 and PM emissions increased from 2005 to 2010, resulting mainly from poorly understood average SO2 removal efficiency in flue gas desulfurization (FGD) systems in the power sector, and unclear changes in the penetration levels of dust collectors at industrial sources, respectively. While emission trends determined by bottom-up methods can be generally verified by observations from both ground stations and satellites, clear discrepancies exist for given regions and seasons, indicating a need for more accurate spatial and time distributions of emissions. Limitations of current emission control polices are analyzed based on the estimated emission trends. Compared with control of total PM, there are fewer gains in control of fine particles and carbonaceous aerosols, the PM components most responsible for damages to public health and effects on radiative forcing. A much faster decrease of alkaline base cations in primary PM than that of SO2 may have raised the acidification risks to ecosystems, indicating further control of acid precursors is required. Moreover, with relatively strict controls in developed urban areas, air pollution challenges have been expanding to less-developed neighboring regions. There is a great need in the future for multipollutant control strategies that combine recognition of diverse environmental impacts both in urban and rural areas with emission abatement of multiple species in concert. To examine the effects of China’s national policies of energy conservation and emission control during 2005–2010, inter-annual emission trends of gaseous pollutants, primary aerosols, and CO2 are estimated with a bottom-up framework. The control measures led to improved energy efficiency and/or increased penetration of emission control devices at power plants and other important industrial sources, yielding reduced emission factors for all evaluated species except NOx. The national emissions of anthropogenic SO2, CO, and total primary PM (particulate matter) in 2010 are estimated to have been 89%, 108%, and 87% of those in 2005, respectively, suggesting successful emission control of those species despite fast growth of the economy and energy consumption during the period. The emissions of NOx and CO2, however, are estimated to have increased by 47% and 43%, respectively, indicating that they remain largely determined by the growth of energy use, industrial production, and vehicle populations. Based on application of a Monte-Carlo framework, estimated uncertainties of SO2 and PM emissions increased from 2005 to 2010, resulting mainly from poorly understood average SO2 removal efficiency in flue gas desulfurization (FGD) systems in the power sector, and unclear changes in the penetration levels of dust collectors at industrial sources, respectively. While emission trends determined by bottom-up methods can be generally verified by observations from both ground stations and satellites, clear discrepancies exist for given regions and seasons, indicating a need for more accurate spatial and time distributions of emissions. Limitations of current emission control polices are analyzed based on the estimated emission trends. Compared with control of total PM, there are fewer gains in control of fine particles and carbonaceous aerosols, the PM components most responsible for damages to public health and effects on radiative forcing. A much faster decrease of alkaline base cations in primary PM than that of SO2 may have raised the acidification risks to ecosystems, indicating further control of acid precursors is required. Moreover, with relatively strict controls in developed urban areas, air pollution challenges have been expanding to less-developed neighboring regions. There is a great need in the future for multipollutant control strategies that combine recognition of diverse environmental impacts both in urban and rural areas with emission abatement of multiple species in concert.

Final Manuscript in DASH
Yuxuan Wang, J. William Munger, Shicheng Xu, Michael B. McElroy, Jiming Hao, Chris P Nielsen, and Hong Ma. 2010. “CO2 and its correlation with CO at a rural site near Beijing: Implications for combustion efficiency in China.” Atmospheric Chemistry and Physics, 10, Pp. 8881-8897. Publisher's VersionAbstract
Although China has surpassed the United States as the world’s largest carbon dioxide emitter, in situ measurements of atmospheric CO2 have been sparse in China.
This paper analyzes hourly CO2 and its correlation with CO at Miyun, a rural site near Beijing, over a period of 51 months (Dec 2004 through Feb 2009). The CO2-CO correlation analysis evaluated separately for each hour of the day provides useful information with statistical significance even in the growing season. We found that the intercept, representing the initial condition imposed by global distribution of CO2 with influence of photosynthesis and respiration, exhibits diurnal cycles differing by season. The background CO2 (CO2,b) derived from Miyun observations is comparable to CO2 observed at a Mongolian background station to the northwest.  Annual growth of overall mean CO2 at Miyun is estimated at 2.7 ppm yr−1 while that of CO2,b is only 1.7 ppm yr−1 similar to the mean growth rate at northern mid-latitude background stations. This suggests a relatively faster increase in the regional CO2 sources in China than the global average, consistent with bottom-up studies of CO2 emissions. For air masses with trajectories through the northern China boundary layer, mean winter CO2/CO correlation slopes (dCO2/dCO) increased by 2.8±0.9 ppmv/ppmv or 11% from 2005–2006 to 2007–2008, with CO2 increasing by 1.8 ppmv. The increase in dCO2/dCO indicates improvement in overall combustion efficiency over northern China after winter 2007, attributed to pollution reduction measures associated with the 2008 Beijing Olympics. The observed CO2/CO ratio at Miyun is
25% higher than the bottom-up CO2/CO emission ratio, suggesting a contribution of respired CO2 from urban residents as well as agricultural soils and livestock in the observations and uncertainty in the emission estimates. 
Final Manuscript in DASH
Yu Zhao, Chris P Nielsen, Yu Lei, Michael B. McElroy, and Jiming Hao. 2011. “Quantifying the uncertainties of a bottom-up emission inventory of anthropogenic atmospheric pollutants in China.” Atmospheric Chemistry and Physics, 11, Pp. 2295-2308. Publisher's VersionAbstract
The uncertainties of a national, bottom-up inventory
of Chinese emissions of anthropogenic SO2, NOx, and
particulate matter (PM) of different size classes and carbonaceous
species are comprehensively quantified, for the first
time, using Monte Carlo simulation. The inventory is structured
by seven dominant sectors: coal-fired electric power,
cement, iron and steel, other industry (boiler combustion),
other industry (non-combustion processes), transportation,
and residential. For each parameter related to emission factors
or activity-level calculations, the uncertainties, represented
as probability distributions, are either statistically fitted
using results of domestic field tests or, when these are
lacking, estimated based on foreign or other domestic data.
The uncertainties (i.e., 95% confidence intervals around the
central estimates) of Chinese emissions of SO2, NOx, total
PM, PM10, PM2.5, black carbon (BC), and organic carbon
(OC) in 2005 are estimated to be −14%13%, −13%37%,
−11%38%, −14%45%, −17%54%, −25%136%,
and −40%121%, respectively. Variations at activity levels
(e.g., energy consumption or industrial production) are
not the main source of emission uncertainties. Due to narrow
classification of source types, large sample sizes, and
relatively high data quality, the coal-fired power sector is estimated
to have the smallest emission uncertainties for all
species except BC and OC. Due to poorer source classifications
and a wider range of estimated emission factors,
considerable uncertainties of NOx and PM emissions from
cement production and boiler combustion in other industries
are found. The probability distributions of emission
factors for biomass burning, the largest source of BC and
OC, are fitted based on very limited domestic field measurements,
and special caution should thus be taken interpreting
these emission uncertainties. Although Monte Carlo simulation
yields narrowed estimates of uncertainties compared
to previous bottom-up emission studies, the results are not
always consistent with those derived from satellite observations.
The results thus represent an incremental research
advance; while the analysis provides current estimates of
uncertainty to researchers investigating Chinese and global
atmospheric transport and chemistry, it also identifies specific
needs in data collection and analysis to improve on
them. Strengthened quantification of emissions of the included
species and other, closely associated ones – notably
CO2, generated largely by the same processes and thus subject
to many of the same parameter uncertainties – is essential
not only for science but for the design of policies to redress
critical atmospheric environmental hazards at local, regional,
and global scales.
Final Manuscript in DASH
Xi Lu, Jackson Salovaara, and Michael B. McElroy. 2012. “Implications of the recent reductions in natural gas prices for emissions of CO2 from the US power sector.” Environmental Science & Technology, 46, 5, Pp. 3014–3021. Publisher's VersionAbstract
CO2 emissions from the US power sector decreased by 8.76% in 2009 relative to 2008 contributing to a decrease over this period of 6.59% in overall US emissions of greenhouse gases. An econometric model, tuned to data reported for regional generation of US electricity, is used to diagnose factors responsible for the 2009 decrease. More than half of the reduction is attributed to a shift from generation of power using coal to gas driven by a recent decrease in gas prices in response to the increase in production from shale. An important result of the model is that, when the cost differential for generation using gas rather than coal falls below 2–3 cents/kWh, less efficient coal fired plants are displaced by more efficient natural gas combined cycle (NGCC) generation alternatives. Costs for generation using NGCC decreased by close to 4 cents/kWh in 2009 relative to 2008 ensuring that generation of electricity using gas was competitive with coal in 2009 in contrast to the situation in 2008 when gas prices were much higher. A modest price on carbon could contribute to additional switching from coal to gas with further savings in CO2 emissions.

Final Manuscript in DASH
This paper is from a series investigating and comparing the prospects for low- and non-carbon power generation in China and the U.S.; click here (http://news.harvard.edu/gazette/story/2012/02/model-situation/) to see coverage in the Harvard Gazette.

Jing Cao, Richard Garbaccio, and Mun S Ho. 2009. “China's 11th Five-Year Plan and the environment: Reducing SO2 emissions.” Review of Environmental Economics and Policy, 3, 2, Pp. 189-208. Publisher's VersionAbstract
China's rapid economic growth has been accompanied by a high level of environmental degradation. One of the major sources of health and ecosystem damages is sulfur dioxide (SO2). Reducing SO2 emissions is a priority of China's environmental authorities, and the 11th Five-Year Plan (2006–2010) includes the target of reducing total SO2 emissions by 10 percent from the 2005 level. Given the rapid increase in SO2 emissions that is expected to occur in absence of intervention, attaining this target will require a significant effort. This article examines the two major policy measures the government is taking to achieve the SO2 target: a shutdown of many small, inefficient power plants and the installation of desulfurization equipment on existing and new coal-fired plants. We present results from a joint U.S.–China study that we participated in, which estimated the costs and benefits of these policies. We then estimate the economy-wide impacts of the two policies using a multisector model of the Chinese economy. We find that in the aggregate, the economic benefits of the shutdown of the small power plants are large enough to offset the costs of the desulfurization equipment, even without considering the substantial environmental benefits from the reduction of emissions of SO2 and other pollutants.
Yu Zhao, Michael B. McElroy, Jia Xing, Lei Duan, Chris P Nielsen, Yu Lei, and Jiming Hao. 2011. “Multiple effects and uncertainties of emission control policies in China: Public health, soil acidification, and global temperature.” Science of the Total Environment , 409, 24, Pp. 5177-5187. Publisher's VersionAbstract
Policies to control emissions of criteria pollutants in China may have conflicting impacts on public health, soil acidification, and climate. Two scenarios for 2020, a base case without anticipated control measures and a more realistic case including such controls, are evaluated to quantify the effects of the policies on emissions and resulting environmental outcomes. Large benefits to public health can be expected from the controls, attributed mainly to reduced emissions of primary PM and gaseous PM precursors, and thus lower ambient concentrations of PM2.5. Approximately 4% of all-cause mortality in the country can be avoided (95% confidence interval: 1–7%), particularly in eastern and north-central China, regions with large population densities and high levels of PM2.5. Surface ozone levels, however, are estimated to increase in parts of those regions, despite NOX reductions. This implies VOC-limited conditions. Even with significant reduction of SO2 and NOX emissions, the controls will not significantly mitigate risks of soil acidification, judged by the exceedance levels of critical load (CL). This is due to the decrease in primary PM emissions, with the consequent reduction in deposition of alkaline base cations. Compared to 2005, even larger CL exceedances are found for both scenarios in 2020, implying that PM control may negate any recovery from soil acidification due to SO2 reductions. Noting large uncertainties, current polices to control emissions of criteria pollutants in China will not reduce climate warming, since controlling SO2 emissions also reduces reflective secondary aerosols. Black carbon emission is an important source of uncertainty concerning the effects of Chinese control policies on global temperature change. Given these conflicts, greater consideration should be paid to reconciling varied environmental objectives, and emission control strategies should target not only criteria pollutants but also species such as VOCs and CO2.
Final Manuscript in DASH
Yu Zhao, Chris P Nielsen, Michael B. McElroy, Lin Zhang, and Jie Zhang. 2012. “CO emissions in China: Uncertainties and implications of improved energy efficiency and emission control.” Atmospheric Environment, 49, Pp. 103-113. Publisher's VersionAbstract
A bottom-up methodology and an improved database of emission factors combining the latest domestic field measurements are developed to estimate the emissions of anthropogenic CO from China at national and provincial levels. The CO emission factors for major economic sectors declined to varying degrees from 2005 to 2009, attributed to improved energy efficiency and/or emission control regulations. Total national CO emissions are estimated at 173 Tg for 2005 and have been relatively stable for subsequent years, despite fast growth of energy consumption and industrial production. While industry and transportation sources dominated CO emissions in developed eastern and north-central China, residential combustion played a much greater role in the less developed western provinces. The uncertainties of national Chinese CO emissions are quantified using Monte Carlo simulation at −20% to +45% (95% confidence interval). Due to poor understanding of emission factors and activity levels for combustion of solid fuels, the largest uncertainties are found for emissions from the residential sector. The trends of bottom-up emissions compare reasonably to satellite observation of CO columns and to ground observations of CO2–CO correlation slopes. The increase in the ratio for emissions of CO2 relative to CO suggests that China has successfully improved combustion efficiencies across its economy in recent years, consistent with national policies to improve energy efficiency and to control criteria air pollutants.
Final Manuscript in DASH
Yuxuan Wang, Jiming Hao, Michael B. McElroy, J. William Munger, Hong Ma, Dan Chen, and Chris P Nielsen. 2009. “Ozone air quality during the 2008 Beijing Olympics: Effectiveness of emission restrictions.” Atmospheric Chemistry and Physics, 9, 14, Pp. 5237-5251. Publisher's VersionAbstract
A series of aggressive measures was launched by
the Chinese government to reduce pollutant emissions from
Beijing and surrounding areas during the Olympic Games.
Observations at Miyun, a rural site 100 km downwind of the
Beijing urban center, show significant decreases in concentrations
of O3, CO, NOy, and SO2 during August 2008, relative
to August 2006–2007. The mean daytime mixing ratio
of O3 was lower by about 15 ppbv, reduced to 50 ppbv, in
August 2008. The relative reductions in daytime SO2, CO,
and NOy were 61%, 25%, and 21%, respectively. Changes in
SO2 and in species correlations from 2007 to 2008 indicate
that emissions of SO2, CO, and NOx were reduced at least
by 60%, 32%, and 36%, respectively, during the Olympics.
Analysis of meteorological conditions and interpretation of
observations using a chemical transport model suggest that
although the day-to-day variability in ozone is driven mostly
by meteorology, the reduction in emissions of ozone precursors
associated with the Olympic Games had a significant
contribution to the observed decrease in O3 during August
2008, accounting for 80% of the O3 reduction for the
month as a whole and 45% during the Olympics Period (8–
24 August). The model predicts that emission restrictions
such as those implemented during the Olympics can affect
O3 far beyond the Beijing urban area, resulting in reductions
in boundary layer O3 of 2–10 ppbv over a large region of the
North China Plain and Northeastern China.
Final Manuscript in DASH
Chris P Nielsen and Mun S Ho. 2007. “Summary for policy.” In Clearing the air: The health and economic damages of air pollution in China, edited by Mun S Ho and Chris P Nielsen. Cambridge, MA: MIT Press. Publisher's VersionAbstract
An interdisciplinary, quantitative assessment of the health and economic costs of air pollution in China, and of market-based policies to build environmental protection into economic development.
Michael B. McElroy and Yuxuan Wang. 2005. “Human and animal wastes: Implications for atmospheric N2O and NOX.” Global Biogeochemical Cycles, 19, 2. Publisher's VersionAbstract
More than 220 Tg N are processed annually through the global agriculture/animal/human food chain. It is suggested that aerobic denitrification, reduction of nitrite formed in the first stage of nitrification, is an important source not only of global N2O but also of NOx. A simple top‐down method indicates a globally averaged yield of 2% for N2O emitted as a consequence of human disturbances to the global nitrogen cycle. This yield can account not only for the contemporary budget of atmospheric N2O but also for trends observed over the past 1000 years. The associated microbial source of NOx is estimated assuming a NOx/N2O ratio of 3, consistent with results from a variety of laboratory and field studies. This source is significant, particularly for large developing countries such as China and India for which its contribution is comparable to that from fossil fuel.
Final Manuscript in DASH
Sue J. Lin, I.J. Lu, and Charles Lewis. 2006. “Identifying key factors and strategies for reducing industrial CO2 emissions from a non-Kyoto protocol member’s (Taiwan) perspective.” Energy Policy, 34, Pp. 1499-1507. Publisher's VersionAbstract
In this study we use Divisia index approach to identify key factors affecting CO2 emission changes of industrial sectors in Taiwan. The changes of CO2 emission are decomposed into emission coefficient, energy intensity, industrial structure and economic growth. Furthermore, comparisons with USA, Japan, Germany, the Netherlands and South Korea are made to have a better understanding of emission tendency in these countries and to help formulate our CO2 reduction strategies for responding to the international calls for CO2 cuts. The results show that economic growth and high energy intensity were two key factors for the rapid increase of industrial CO2 emission in Taiwan, while adjustment of industrial structure was the main component for the decrease. Although economic development is important, Taiwan must keep pace with the international trends for CO2 reduction. Among the most important strategies are continuous efforts to improve energy intensity, fuel mix toward lower carbon, setting targets for industrial CO2 cuts, and advancing green technology through technology transfer. Also, the clean development mechanism (CDM) is expected to play an important role in the future.
Shuxiao Wang, Jiming Hao, Yongqi Lu, and Ji Li. 2007. “Local population exposure to pollutants from the major industrial sectors.” In Clearing the air: The health and economic damages of air pollution in China, edited by Mun S Ho and Chris P Nielsen. Cambridge, MA: MIT Press. Publisher's VersionAbstract
An interdisciplinary, quantitative assessment of the health and economic costs of air pollution in China, and of market-based policies to build environmental protection into economic development.
Ying Zhou, Jonathan I Levy, John S Evans, and James K Hammitt. 2006. “The influence of geographic location on population exposure to emissions from power plants throughout China.” Environment International, 32, 3, Pp. 365-373. Publisher's VersionAbstract
This analysis seeks to evaluate the influence of emission source location on population exposure in China to fine particles and sulfur dioxide. We use the concept of intake fraction, defined as the fraction of material or its precursor released from a source that is eventually inhaled or ingested by a population. We select 29 power-plant sites throughout China and estimate annual average intake fractions at each site, using identical source characteristics to isolate the influence of geographic location. In addition, we develop regression models to interpret the intake fraction values and allow for extrapolation to other sites. To model the concentration increase due to emissions from selected power plants, we used a detailed long-range atmospheric dispersion model, CALPUFF. Primary fine particles have the highest average intake fraction (1 × 10− 5), followed by sulfur dioxide (5 × 10− 6), sulfate from sulfur dioxide (4 × 10− 6), and nitrate from nitrogen oxides (4 × 10− 6). For all pollutants, the intake fractions span approximately an order of magnitude across sites. In the regression analysis, the independent variables are meteorological proxies (such as climate region and precipitation) and population at various distances from the source. We find that population terms can explain a substantial percentage of variability in the intake fraction for all pollutants (R2 between 0.86 and 0.95 across pollutants), with a significant modifying influence of meteorological regime. Near-source population is more important for primary coarse particles while population at medium to long distance is more important for primary fine particles and secondary particles. A significant portion of intake fraction (especially for secondary particles and primary fine particles) occurs beyond 500 km of the source, emphasizing the need for detailed long-range dispersion modeling. These findings demonstrate that intake fractions for power plants in China can be estimated with reasonable precision and summarized using simple regression models. The results should be useful for informing future decisions about power-plant locations and controls.
Yuxuan Wang, Michael B. McElroy, K. Folkert Boersma, Henk J Eskes, and Pepijn J Veefkind. 2007. “Traffic restrictions associated with the Sino-African Summit: Reductions of NOX detected from space.” Geophysical Research Letters, 34, L08814. Publisher's VersionAbstract
Aggressive measures were instituted by the Beijing municipal authorities to restrict vehicular traffic in the Chinese capital during the recent Sino-African Summit. We show that reductions in associated emissions of NOx were detected by the Dutch-Finnish Ozone Monitoring Instrument (OMI) aboard the Aura satellite. Interpretation of these data using a 3-dimensional chemical transport model indicates that emissions of NOx were reduced by 40% over the period of November 4 to 6, 2006, for which the restrictions were in place.
Final Manuscript in DASH

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