# Atmospheric Emissions

Yu Zhao, Lei Duan, Jia Xing, Thorjorn Larssen, Chris P Nielsen, and Jiming Hao. 2009. “Soil acidification in China: Is controlling SO2 emissions enough?” Environmental Science and Technology, 43, 21, Pp. 8021-8026. Publisher's VersionAbstract
Facing challenges of increased energy consumption and related regional air pollution, China has been aggressively implementing flue gas desulfurization (FGD) and phasing out small inefficient units in the power sector in order to achieve the national goal of 10% reduction in sulfur dioxide (SO2) emissions from 2005 to 2010. In this paper, the effect of these measures on soil acidification is explored. An integrated methodology is used, combining emission inventory data, emission forecasts, air quality modeling, and ecological sensitivities indicated by critical load. National emissions of SO2, oxides of nitrogen (NOX), particulate matter (PM), and ammonia (NH3) in 2005 were estimated to be 30.7, 19.6, 31.3, and 16.6 Mt, respectively. Implementation of existing policy will lead to reductions in SO2 and PM emissions, while those of NOX and NH3 will continue to rise, even under tentatively proposed control measures. In 2005, the critical load for soil acidification caused by sulfur (S) deposition was exceeded in 28% of the country’s territory, mainly in eastern and south-central China. The area in exceedance will decrease to 26% and 20% in 2010 and 2020, respectively, given implementation of current plans for emission reductions. However, the exceedance of the critical load for nitrogen (N, combining effects of eutrophication and acidification) will double from 2005 to 2020 due to increased NOX and NH3 emissions. Combining the acidification effects of S and N, the benefits of SO2 reductions during 2005−2010 will almost be negated by increased N emissions. Therefore abatement of N emissions (NOX and NH3) and deposition will be a major challenge to China, requiring policy development and technology investments. To mitigate acidification in the future, China needs a multipollutant control strategy that integrates measures to reduce S, N, and PM.
Xi Lu, Michael B. McElroy, and Nora Sluzas. 2011. “Costs for integrating wind into the future ERCOT system with related costs for savings in CO2 emissions.” Environmental Science and Technology, 45, 7, Pp. 3160-3166. Publisher's VersionAbstract
Wind power can make an important contribution to the goal of reducing emissions of CO2. The major problem relates to the intrinsic variability of the source and the difficulty of reconciling the supply of electricity with demand particularly at high levels of wind penetration. This challenge is explored for the case of the ERCOT system in Texas. Demand for electricity in Texas is projected to increase by approximately 60% by 2030. Considering hourly load data reported for 2006, assuming that the pattern of demand in 2030 should be similar to 2006, and adopting as a business as usual (BAU) reference an assumption that the anticipated additional electricity should be supplied by a combination of coal and gas with prices, discounted to 2007 dollars of $2 and$6 per MMBTU respectively, we conclude that the bus-bar price for electricity would increase by about 1.1¢/kWh at a wind penetration level of 30%, by about 3.4 ¢/kWh at a penetration level of 80%. Corresponding costs for reductions in CO2 range from $20/ton to$60/ton. A number of possibilities are discussed that could contribute to a reduction in these costs including the impact of an expanded future fleet of electrically driven vehicles.

Final Manuscript in DASH
This is from a series of papers investigating and comparing the prospects for low- and non-carbon power generation in China and the U.S.

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.

Yu Zhao, Lei Duan, Yu Lei, Jia Xing, Chris P Nielsen, and Jiming Hao. 2011. “Will PM control undermine China's efforts to reduce soil acidification?” Environmental Pollution, 159, 10, Pp. 2726-2732. Publisher's VersionAbstract
China’s strategies to control acidifying pollutants and particulate matter (PM) may be in conflict for soil acidification abatement. Acidifying pollutant emissions are estimated for 2005 and 2020 with anticipated control policies. PM emissions including base cations (BCs) are evaluated with two scenarios, a base case applying existing policy to 2020, and a control case including anticipated tightened measures. Depositions of sulfur (S), nitrogen (N) and BCs are simulated and their acidification risks are evaluated with critical load (CL). In 2005, the area exceeding CL covered 15.6% of mainland China, with total exceedance of 2.2 Mt S. These values decrease in the base scenario 2020, implying partial recovery from acidification. Under more realistic PM control, the respective estimates are 17.9% and 2.4 Mt S, indicating increased acidification risks due to abatement of acid-neutralizing BCs. China’s anthropogenic PM abatement will have potentially stronger chemical implications for acidification than developed countries.
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.

Jin-Tai Lin, Michael B. McElroy, and K. Folkert Boersma. 2010. “Constraint of anthropogenic NOx emissions in China from different sectors: A new methodology using separate satellite retrievals.” Atmospheric Chemistry and Physics, 10, 1, Pp. 63-78. Publisher's VersionAbstract
A new methodology is developed to constrain
Chinese anthropogenic emissions of nitrogen oxides (NOx)
from four major sectors (industry, power plants, mobile and
residential) in July 2008. It combines tropospheric NO2 column
retrievals from GOME-2 and OMI, taking advantage
of their different passing time over China (10:00 a.m. LT
(local time) versus 02:00 p.m.) and consistent retrieval algorithms.
The approach is based on the difference of NOx
columns at the overpass times of the two instruments; it thus
is less susceptible to the likely systematic errors embedded
in individual retrievals that are consistent with each other.
Also, it explicitly accounts for diurnal variations and uncertainties
of NOx emissions for individual sources. Our best
top-down estimate suggests a national budget of 6.8 TgN/yr
(5.5 TgN/yr for East China), close to the a priori bottom-up
emission estimate from the INTEX-B mission for the year of
2006. The top-down emissions are lower than the a priori
near Beijing, in the northeastern provinces and along the east
coast; yet they exceed the a priori over many inland regions.
Systematic errors in satellite retrievals are estimated to lead
to underestimation of top-down emissions by at most 17%
(most likely 10%). Effects of other factors on the top-down
estimate are typically less than 15% each, including lightning,
soil emissions, mixing in planetary boundary layer, anthropogenic
emissions of carbon monoxide and volatile organic
compounds, magnitude of a priori emissions, assumptions
on emission diurnal variations, and uncertainties in the
four sectors. The a posteriori emission budget is 5.7 TgN/yr
for East China.
Yuxuan Wang, Michael B. McElroy, Randall V Martin, David G Streets, Qiang Zhang, and Tung-May Fu. 2007. “Seasonal variability of NOx emissions over east China constrained by satellite observations: Implications for combustion and microbial sources.” Journal of Geophysical Research, 112, D06301. Publisher's VersionAbstract
Observations of tropospheric column densities of NO2 obtained from the Global Ozone Monitoring Experiment (GOME) for a 3‐year period (1997, 1998, and 2000) are used to derive average seasonal variations in surface emissions of NOx from east China (100–123°E, 20–42°N). The retrieval allows for zonal variations in the contribution of the stratosphere to the NO2 column and removes a bias of ±10% on the seasonality of retrieved columns introduced by cloud screening. The top‐down inventory is constructed using an inversion approach with a global 3‐D chemical transport model (GEOS‐Chem) and combined subsequently with the a priori inventory to develop an a posteriori inventory. The contribution of background NO2 arising from nonsurface sources (lightning) and long‐range transport of emissions originating outside of east China is accounted for in the inversion. The a posteriori estimate of overall emissions for east China, 4.66 Tg N/yr (±30% uncertainty), is 33% higher than the a priori value and is shown to improve agreement with surface measurements of nitrate wet deposition and concentrations of NOy observed in China. On the basis of multiple constraints on the spatial and seasonal variations of combustion and microbial processes, the a posteriori inventory is partitioned among emissions from biomass burning, fuel combustion, and microbial activity (or soil emissions). Emission of NOx from biomass burning in east China is estimated as 0.08 TgN/yr ± 50% in the a posteriori inventory, increased by about a factor of 2 from the a priori estimate. The resulting a posteriori inventory for fuel combustion (3.72 TgN/yr ± 32%) is about 15% higher than the a priori and exhibits a distinct maximum in winter, in contrast to the weak seasonality indicated in the a priori inventory. The a posteriori value for the microbial source of NOx (0.85 TgN/yr ± 40%) is about a factor of 3 higher than the a priori value, amounting to 23% of combustion sources for east China and significantly higher than a priori value of 7%. The microbial source is unimportant in winter. It peaks in summer, accounting for as much as 43% of the combustion source for that season, and is significant also in spring and fall. This seasonality is attributed to the timing of fertilizer application and to the influence of seasonally variable environmental factors including temperature and precipitation.
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.
Ying Zhou, Jonathan I Levy, James K Hammitt, and John S Evans. 2007. “Population exposure to pollutants from the electric power sector using CALPUFF.” 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.
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.
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.
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.
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.