出版文献

Emissions of sulfur dioxide (SO₂) from the U.S. power sector decreased by 24% in 2009 relative to 2008. The Logarithmic Mean Divisia Index (LMDI) approach was applied to isolate the factors responsible for this decrease. It is concluded that 15% of the decrease can be attributed to the drop in demand for electricity triggered by the economic recession, and 28% can be attributed to switching of fuel from coal to gas responding to the decrease in prices for the latter. The largest factor in the decrease, close to 57%, resulted from an overall decline in emissions per unit of power generated from coal. This is attributed in part to selective idling of older, less efficient coal plants that generally do not incorporate technology for sulfur removal, and in part to continued investments by the power sector in removal equipment in response to the requirements limiting emissions imposed by the U.S. Environmental Protection Agency (U.S. EPA). The paper argues further that imposition of a modest tax on emissions of carbon would have ancillary benefits in terms of emissions of SO₂.

China's emissions of anthropogenic CO₂ are estimated using a bottom-up emission inventory framework based on a detailed categorization of economic sectors and provincial economic and energy data. It includes a newly compiled database of CO₂ emission factors employing the latest field study results from China. Total annual emissions are estimated to have risen from 7126 to 9370 Mt CO₂ from 2005 to 2009. Recent policies to conserve energy and reduce emissions have been effective in limiting CO₂ emissions from power and iron & steel plants, but have had little effect on those from cement production. The uncertainties of China's CO₂ emissions are quantified for the first time using Monte-Carlo simulation, producing a 95% confidence interval (CI) of −9% to +11% for total emissions in 2005. The largest contributors to sector-level emission uncertainty are emission factors for most industrial sources and activity levels for power plants, transportation, and residential & commercial sources. Application of province-level energy consumption and China-specific emission factors in some sectors results in higher annual emission estimates for 2005-2008 as compared with other studies, although most of those are within the 95% CIs of this study.

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.

Observations of CO₂ and O₂ are interpreted to develop an understanding of the changes in the abundance of atmospheric CO₂ that have arisen over the period 1995–2007. Fossil fuels accounted for an addition of 89.3 Gt of carbon to the atmosphere over this time period, 29% of which was transferred to the ocean, 15% to the global biosphere, with the balance (57%) retained by the atmosphere. Analysis of historical data for CO₂ derived from studies of gases trapped in ice at Law Dome in Antarctica indicate that the biosphere represented a net source of atmospheric CO₂ prior to 1940, switching subsequently to a net sink.

To protect the security of energy supply, China is building national strategic petroleum reserve (SPR). We present a dynamic programming model to determine the optimal stockpiling and drawdown strategies for China's SPR under various scenarios, focusing on minimizing the total cost of reserves. In contrast to previous research, the oil price given in our model is exogenous on a monthly instead of annual basis, with a view to more realistic simulation of optimal strategies each year. Our model results show that in the case where stockpiling affects oil prices, a given SPR size will be achieved earlier than when stockpiling does not affect oil prices. In different emergency conditions, the optimal stockpiling and drawdown strategies of China's SPR are very different. When an emergency occurs, the shock of stockpiling on the oil price per barrel could range $0.49–$6.35, while the impact of drawdown on the oil price per barrel could range −$6.22 to −$0.48.

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.

This study compares the full costs of seven passenger modes in the large Chinese cities facing the difficult yet crucial choice among alternative passenger transportation systems. The seven modes are evaluated at varied traffic volumes in hypothetical radial and circumferential commuting corridors. Using detailed estimates of private and social costs, the full cost of each mode is minimized by optimizing infrastructure investment and operation plans. On all corridors and across different scenarios, commuting by one or more forms of bus transit or bicycle costs less than automobile or rail. Nonetheless, in circumferential corridors, rail can be almost as cost-effective as bus under certain conditions, and bicycle can be less cost-effective than bus in some cases. Unlike results from similar studies conducted in the US, automobile commuting does not cost less than bus transportation at low traffic volumes.

The mass concentrations of black carbon (BC) were measured continuously at Miyun, a rural site near Beijing, concurrently with some trace gases (CO, CO₂, NO_y, SO₂) during the nonheating seasons of 2010 (April to October). The average concentration of BC was 2.26 ± 2.33 μg m⁻³. About 70%–100% of the air masses arriving at the site from June to September were from the source region of Beijing and the North China Plain (NCP), while in the spring, 40% were of continental background origin. BC had moderate to strong positive correlations with CO (R² = 0.51), NO_y (R² = 0.58), and CO₂ (nonsummer, R² = 0.54), but not with SO₂ (R² < 0.1). The observed ΔBC/ΔCO ratio was 0.0050 ± 0.0001 μg m⁻³/ppbv for the regional air masses (excluding the influence of biomass burning). This ratio increased by 68% to 0.0084 ± 0.0004 μg m⁻³/ppbv after excluding the influence of wet deposition. Accounting further for the impact of atmospheric processes on the observation, we derived an average top‐down BC/CO emission ratio of 0.0095 ± 0.002 μg m⁻³/ppbv for the source region of Beijing and NCP that is 18%–21% lower than the average emission ratio from the bottom‐up inventory of Zhang et al. (2009), whereas the difference is substantially lower than the uncertainty of emissions for either species. The difference between the mean bottom‐up and top‐down emission ratios is most likely to be attributed to the residential sector, which needs to have a lower share in the total emissions of BC or a much lower BC/CO emission ratio. The industry and transportation sectors are found to be dominant sources of BC from Beijing and the NCP rather than from the residential sector as suggested by the bottom‐up inventory.

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.

Rapid economic and industrial development in
China and relatively weak emission controls have resulted in
significant increases in emissions of nitrogen oxides (NOx)
in recent years, with the exception of late 2008 to mid 2009
when the economic downturn led to emission reductions detectable
from space. Here vertical column densities (VCDs)
of tropospheric NO2 retrieved from satellite observations by
SCIAMACHY, GOME-2 and OMI (both by KNMI and by
NASA) are used to evaluate changes in emissions of NOx
from October 2004 to February 2010 identifying impacts of
the economic downturn. Data over polluted regions of Northern
East China suggest an increase of 27–33% in 12-month
mean VCD of NO2 prior to the downturn, consistent with an
increase of 49% in thermal power generation (TPG) reflecting
the economic growth. More detailed analysis is used to
quantify changes in emissions of NOx in January over the
period 2005–2010 when the effect of the downturn was most
evident. The GEOS-Chem model is employed to evaluate
the effect of changes in chemistry and meteorology on VCD
of NO2. This analysis indicates that emissions decreased by
20% from January 2008 to January 2009, close to the reduction
of 18% in TPG that occurred over the same interval. A
combination of three independent approaches indicates that
the economic downturn was responsible for a reduction in
emissions by 9–11% in January 2009 with an additional decrease
of 10%attributed to the slow-down in industrial activity
associated with the coincident celebration of the Chinese
New Year; errors in the estimate are most likely less than
3.4 %.

A spatial financial model using wind data derived from assimilated meteorological condition was developed to investigate the profitability and competitiveness of onshore wind power in the contiguous U.S. It considers not only the resulting estimated capacity factors for hypothetical wind farms but also the geographically differentiated costs of local grid connection. The levelized cost of wind-generated electricity for the contiguous U.S. is evaluated assuming subsidy levels from the Production Tax Credit (PTC) varying from 0 to 4 ¢/kWh under three cost scenarios: a reference case, a high cost case, and a low cost case. The analysis indicates that in the reference scenario, current PTC subsidies of 2.1 ¢/kWh are at a critical level in determining the competitiveness of wind-generated electricity compared to conventional power generation in local power market. Results from this study suggest that the potential for profitable wind power with the current PTC subsidy amounts to more than seven times existing demand for electricity in the entire U.S. Understanding the challenges involved in scaling up wind energy requires further study of the external costs associated with improvement of the backbone transmission network and integration into the power grid of the variable electricity generated from wind.

Direct emissions of air pollutants from the cement industry in China were estimated by developing a technology-based methodology using information on the proportion of cement produced from different types of kilns and the emission standards for the Chinese cement industry. Historical emissions of sulfur dioxide (SO₂), nitrogen oxides (NO_X), carbon monoxide (CO), particulate matter (PM) and carbon dioxide (CO₂) were estimated for the years 1990–2008, and future emissions were projected up to 2020 based on current energy-related and emission control policies. Compared with the historical high (4.36 Tg of PM_2.5, 7.16 Tg of PM₁₀ and 10.44 Tg of TSP in 1997), PM emissions are predicted to drop substantially by 2020, despite the expected tripling of cement production. Certain other air pollutant emissions, such as CO and SO₂, are also predicted to decrease with the progressive closure of shaft kilns. NO_X emissions, however, could increase because of the promotion of precalciner kilns and the rapid increase of cement production. CO₂ emissions from the cement industry account for approximately one eighth of China’s national CO₂ emissions. Our analysis indicates that it is possible to reduce CO₂ emissions from this industry by approximately 12.8% if advanced energy-related technologies are implemented. These technologies will bring co-benefits in reducing other air pollutants as well.

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 PM_2.5. 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 PM_2.5. Surface ozone levels, however, are estimated to increase in parts of those regions, despite NO_X reductions. This implies VOC-limited conditions. Even with significant reduction of SO₂ and NO_X 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.

An inventory of anthropogenic primary aerosol
emissions in China was developed for 1990–2005 using a
technology-based approach. Taking into account changes
in the technology penetration within industry sectors and
improvements in emission controls driven by stricter emission
standards, a dynamic methodology was derived and implemented
to estimate inter-annual emission factors. Emission
factors of PM2.5 decreased by 7%–69% from 1990 to
2005 in different industry sectors of China, and emission factors
of TSP decreased by 18%–80% as well, with the measures
of controlling PM emissions implemented. As a result,
emissions of PM2.5 and TSP in 2005 were 11.0 Tg and
29.7 Tg, respectively, less than what they would have been
without the adoption of these measures. Emissions of PM2.5,
PM10 and TSP presented similar trends: they increased in
the first six years of 1990s and decreased until 2000, then
increased again in the following years. Emissions of TSP
peaked (35.5 Tg) in 1996, while the peak of PM10 (18.8 Tg)
and PM2.5 (12.7 Tg) emissions occurred in 2005. Although
various emission trends were identified across sectors, the cement
industry and biofuel combustion in the residential sector
were consistently the largest sources of PM2.5 emissions,
accounting for 53%–62% of emissions over the study period.
The non-metallic mineral product industry, including the cement,
lime and brick industries, accounted for 54%–63% of
national TSP emissions. There were no significant trends of
BC and OC emissions until 2000, but the increase after 2000
Correspondence to: K. B. He
(hekb@tsinghua.edu.cn)
brought the peaks of BC (1.51 Tg) and OC (3.19 Tg) emissions
in 2005. Although significant improvements in the estimation
of primary aerosols are presented here, there still
exist large uncertainties. More accurate and detailed activity
information and emission factors based on local tests are essential
to further improve emission estimates, this especially
being so for the brick and coke industries, as well as for coalburning
stoves and biofuel usage in the residential sector.

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.

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.