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Aunan K.,CICERO Center for International Climate and Environmental Research | Aunan K.,University of Oslo | Wang S.,Tsinghua University | Wang S.,State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex
Science of the Total Environment | Year: 2014

Exposure to fine particles ≤2.5μm in aerodynamic diameter (PM2.5) from incomplete combustion of solid fuels in household stoves, denoted household air pollution (HAP), is a major contributor to ill health in China and globally. Chinese households are, however, undergoing a massive transition to cleaner household fuels. The objective of the present study is to establish the importance of internal migration when it comes to the changing household fuel use pattern and the associated exposure to PM2.5 for the period 2000 to 2010. We also estimate health benefits of the fuel transition in terms of avoided premature deaths. Using China Census data on population, migration, and household fuel use for 2000 and 2010 we identify the size, place of residence, and main cooking fuel of sub-populations in 2000 and 2010, respectively. We combine these data with estimated exposure levels for the sub-populations and estimate changes in population exposure over the decade. We find that the population weighted exposure (PWE) for the Chinese population as a whole was reduced by 52 (36-70) μg/m3 PM2.5 over the decade, and that about 60% of the reduction can be linked to internal migration. During the same period the migrant population, in total 261million people, was subject to a reduced population weighted exposure (δPWE) of 123 (87-165) μg/m3 PM2.5. The corresponding figure for non-migrants is 34 (23-47) μg/m3. The largest δPWE was estimated for rural-to-urban migrants (138million people), 214 (154-283) μg/m3. The estimated annual health benefit associated with the reduced exposure in the total population is 31 (26-37) billion USD, corresponding to 0.4% of the Chinese GDP. © 2014 Elsevier B.V.

Zheng B.,Tsinghua University | Zhang Q.,Tsinghua University | Zhang Q.,Collaborative Innovation Center for Regional Environmental Quality | Zhang Y.,Tsinghua University | And 10 more authors.
Atmospheric Chemistry and Physics | Year: 2015

Severe regional haze pollution events occurred in eastern and central China in January 2013, which had adverse effects on the environment and public health. Extremely high levels of particulate matter with aerodynamic diameter of 2.5 μm or less (PM2.5) with dominant components of sulfate and nitrate are responsible for the haze pollution. Although heterogeneous chemistry is thought to play an important role in the production of sulfate and nitrate during haze episodes, few studies have comprehensively evaluated the effect of heterogeneous chemistry on haze formation in China by using the 3-D models due to of a lack of treatments for heterogeneous reactions in most climate and chemical transport models. In this work, the WRF-CMAQ model with newly added heterogeneous reactions is applied to East Asia to evaluate the impacts of heterogeneous chemistry and the meteorological anomaly during January 2013 on regional haze formation. As the parameterization of heterogeneous reactions on different types of particles is not well established yet, we arbitrarily selected the uptake coefficients from reactions on dust particles and then conducted several sensitivity runs to find the value that can best match observations. The revised CMAQ with heterogeneous chemistry not only captures the magnitude and temporal variation of sulfate and nitrate, but also reproduces the enhancement of relative contribution of sulfate and nitrate to PM2.5 mass from clean days to polluted haze days. These results indicate the significant role of heterogeneous chemistry in regional haze formation and improve the understanding of the haze formation mechanisms during the January 2013 episode. © Author(s) 2015.

Zhang S.,Tsinghua University | Wu Y.,Tsinghua University | Wu Y.,State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex | Liu H.,Tsinghua University | And 8 more authors.
Applied Energy | Year: 2014

Seventy-five heavy-duty public transit buses, including different fuel systems (conventional diesel, natural gas and diesel hybrid), were tested on-road in Beijing using portable emission measurement systems. Second-by-second driving condition data were collected on typical urban bus routes including freeways, arterial roads and residential roads. The average values of distance-specific fuel consumption for diesel buses is 32.6L 100km-1 under a typical bus driving cycle in Beijing (BJBC). Natural gas buses have comparable CO2 emission factors but higher fuel consumption relative to diesel buses. Hybrid diesel buses are capable of reducing CO2 emissions and fuel consumption by 18-29% compared to the Euro IV and Euro V diesel buses over the BJBC. This study quantified the impacts on fuel consumption from other conditions including road type, average speed, load mass, and air conditioning. Average speed is the leading indicator of traffic conditions which affects the on-road fuel use most significantly. If the average bus speed decreases from 25kmh-1 to 15kmh-1, fuel consumption is estimated to increase by ~20-30% for diesel buses, ~30-45% for natural gas buses, and most significantly (~50%) for hybrid diesel buses. In addition, real-world fuel consumption of hybrid diesel buses is observed to be particularly sensitive to operating conditions - when their on-board air conditioning systems are functioning, fuel consumption can be increased by up to 50%. © 2013 Elsevier Ltd.

Wang L.T.,Hebei University of Engineering | Wang L.T.,State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex | Wang L.T.,North Carolina State University | Wei Z.,Hebei University of Engineering | And 11 more authors.
Atmospheric Chemistry and Physics | Year: 2014

Extremely severe and persistent haze occurred in January 2013 over eastern and northern China. The record-breaking high concentrations of fine particulate matter (PM2.5) of more than 700 μgm-3 on hourly average and the persistence of the episodes have raised widespread, considerable public concerns. During that period, 7 of the top 10 polluted cities in China were within the Hebei Province. The three cities in southern Hebei (Shijiazhuang, Xingtai, and Handan) have been listed as the top three polluted cities according to the statistics for the first half of the year 2013. In this study, the Mesoscale Modeling System Generation 5 (MM5) and the Models-3/Community Multiscale Air Quality (CMAQ) modeling system are applied to simulate the 2013 severe winter regional hazes in East Asia and northern China at horizontal grid resolutions of 36 and 12 km, respectively, using the Multi-resolution Emission Inventory for China (MEIC). The source contributions of major source regions and sectors to PM2.5 concentrations in the three most polluted cities in southern Hebei are quantified by aiming at the understanding of the sources of the severe haze pollution in this region, and the results are compared with December 2007, the haziest month in the period 2001-2010. Model evaluation against meteorological and air quality observations indicates an overall acceptable performance and the model tends to underpredict PM2.5 and coarse particulate matter (PM10) concentrations during the extremely polluted episodes. The MEIC inventory is proven to be a good estimation in terms of total emissions of cities but uncertainties exist in the spatial allocations of emissions into fine grid resolutions within cities. The source apportionment shows that emissions from northern Hebei and the Beijing-Tianjin city cluster are two major regional contributors to the pollution in January 2013 in Shijiazhuang, compared with those from Shanxi and northern Hebei for December 2007. For Xingtai and Handan, the emissions from northern Hebei and Henan are important. The industrial and domestic sources are the most significant local contributors, and the domestic and agricultural emissions from Shandong and Henan are non-negligible regional sources, especially for Xingtai and Handan. Even in the top two haziest months (i.e., January 2013 and December 2007), a large fraction of PM2.5 in the three cities may originate from quite different regional sources. These results indicate the importance of establishing a regional joint framework of policymaking and action system to effectively mitigate air pollution in this area, not only over the Beijing-Tianjin-Hebei area, but also surrounding provinces such as Henan, Shandong, and Shanxi. © 2014 Author(s).

Cheng Z.,Tsinghua University | Wang S.,Tsinghua University | Wang S.,State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex | Fu X.,Tsinghua University | And 12 more authors.
Atmospheric Chemistry and Physics | Year: 2014

Open biomass burning is an important source of air pollution in China and globally. Joint observations of air pollution were conducted in five cities (Shanghai, Hangzhou, Ningbo, Suzhou and Nanjing) of the Yangtze River delta, and a heavy haze episode with visibility 2.9-9.8 km was observed from 28 May to 6 June 2011. The contribution of biomass burning was quantified using both ambient monitoring data and the WRF/CMAQ (Weather Research and Forecasting (WRF) and Community Multiscale Air Quality (CMAQ)) model simulation. It was found that the average and maximum daily PM2.5 concentrations during the episode were 82 and 144 μgm-3, respectively. Weather pattern analysis indicated that stagnation enhanced the accumulation of air pollutants, while the following precipitation event scavenged the pollution. Mixing depth during the stagnant period was 240-399 m. Estimation based on observation data and CMAQ model simulation indicated that biomass open burning contributed 37% of PM 2.5, 70% of organic carbon and 61% of elemental carbon. Satellite-detected fire spots, back-trajectory analysis and air quality model simulation were integrated to identify the locations where the biomass was burned and the pollutants transport. The results suggested that the impact of biomass open burning is regional, due to the substantial inter-province transport of air pollutants. PM2.5 exposure level could be reduced 47% for the YRD region if complete biomass burning is forbidden and significant health benefit is expected. These findings could improve the understanding of heavy haze pollution, and suggest the need to ban open biomass burning during post-harvest seasons. © Author(s) 2014. CC Attribution 3.0 License.

Bai B.,Tsinghua University | Li J.,Tsinghua University | Li J.,State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex
ACS Catalysis | Year: 2014

Three-dimensional (3D) ordered mesoporous Ag/Co3O4 and K-Ag/Co3O4 catalysts were successfully prepared on the basis of 3D-Co3O4. All catalysts possess 3D mesoporous structures, which are not affected due to Ag and K addition. Ag nanoparticles, uniformly dispersed and supported on the polycrystalline wall of K-Ag/Co 3O4, provide sufficient active sites for HCHO oxidation reaction. 1.7% K-Ag/Co3O4 has turnover frequencies (TOFs) of 0.22 s-1 at 60 °C and 2.62 s-1 at 100 °C, and its HCHO conversion at room temperature is 55% (HCHO 100 ppm and GHSV 30000 h-1). The addition of K+ ions obviously promotes the catalytic performance for HCHO oxidation due to surface OH- species provided by K+ ions and more abundant Ag(111) active faces, Co 3+ cations and surface lattice oxygen (O2-) species generated by stronger interaction between Ag and Co and anion lattice defects. Ag(111) faces, Co3+ ions, and O2- are active species. Combined with TOFs, at low temperature (<80 °C), the HCHO catalytic activity on K-Ag/Co3O4 catalyst largely depends on the surface OH- species at the perimeter of the Ag(111) facets; at relatively high temperature (>80 °C), the surface OH- species are consumed and replaced quickly, and their supplement relies on the migration of O2- species from 3D-Co3O4 support. The pathway of reaction for HCHO oxidation on the K-Ag/Co3O4 follows the HCHO → CHOO- + OH- → CO2 + H2O route. © 2014 American Chemical Society.

Zhao B.,Tsinghua University | Wang S.,Tsinghua University | Wang S.,State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex | Wang J.,Tsinghua University | And 7 more authors.
Atmospheric Environment | Year: 2013

China's air pollution control policies during the 12th Five Year Plan (2011-2015) are characterized by the targets of 10% nitrogen oxides (NOx) reduction and 8% sulfur dioxide (SO2) reduction from the 2010 levels. In this study, the Community Multi-scale Air Quality (CMAQ) modeling system was used to evaluate the impact of only SO2, only NOx, and joint SO2/NOx control measures on particulate matter pollution, the greatest concern for urban air quality in China. Four emission scenarios were developed for 2015, including a business-as-usual scenario, a reference NOx control scenario based on the governmental plan, an accelerated NOx control technology scenario, and a scenario assuming joint controls of NOx and SO2 based on the governmental plan. Under the planned NOx control measures, the annual mean concentrations of particulate matter less than or equal to 2.5μm (PM2.5) decline by 1.5-6μgm-3, i.e. 1.6%-8.5%, in the majority of eastern China. The largest reduction occurs in the middle reach of the Yangtze River. Under accelerated NOx control measures, the annual average PM2.5 concentration reductions (compared with the business-as-usual scenario) in eastern China are 65% higher than the reductions under planned control measures. The unusual increase of PM2.5 concentrations in the North China Plain and the Yangtze River Delta during January after the reductions of NOx emissions was an integrated effect of excessive NOx, the ammonia-rich inorganic aerosol chemistry, and the non-methane volatile organic compounds (NMVOC) sensitive photochemical regime. Under the joint controls of NOx and SO2, the annual mean PM2.5 concentrations decline over 3μgm-3, i.e. 3.2%-13%, in the majority of eastern China, and some areas in the middle reach of the Yangtze River have reductions as large as 6-8.3μgm-3, i.e. 5.0%-13%. The average PM2.5 concentration reductions in eastern China are 1.20μgm-3, 3.14μgm-3, 3.57μgm-3, 4.22μgm-3 in January, May, August, and November, respectively. The corresponding declining rates are 2.3%, 12.2%, 14.3%, and 8.1%, respectively. More stringent policies should be implemented in winter to reduce the heavy pollution periods. The annual average PM2.5 concentration reductions in three major city clusters are comparable with the average reductions of eastern China. Stringent regional control policies are required for the significant improvement of particulate air quality in major city clusters. © 2013.

Wang L.,Tsinghua University | Wang S.,Tsinghua University | Wang S.,State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex | Zhang L.,Tsinghua University | And 7 more authors.
Environmental Pollution | Year: 2014

China is the largest atmospheric mercury (Hg) emitter in the world. Its Hg emissions and environmental impacts need to be evaluated. In this study, China's Hg emission inventory is updated to 2007 and applied in the GEOS-Chem model to simulate the Hg concentrations and depositions in China. Results indicate that simulations agree well with observed background Hg concentrations. The anthropogenic sources contributed 35-50% of THg concentration and 50-70% of total deposition in polluted regions. Sensitivity analysis was performed to assess the impacts of mercury emissions from power plants, non-ferrous metal smelters and cement plants. It is found that power plants are the most important emission sources in the North China, the Yangtze River Delta (YRD) and the Pearl River Delta (PRD) while the contribution of non-ferrous metal smelters is most significant in the Southwest China. The impacts of cement plants are significant in the YRD, PRD and Central China. © 2014 Elsevier B.V. All rights reserved.

Cheng Y.,Tsinghua University | He K.-B.,Tsinghua University | He K.-B.,State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex | He K.-B.,Collaborative Innovation Center for Regional Environmental Quality
Atmospheric Measurement Techniques | Year: 2015

A common approach for measuring the mass of organic carbon (OC) and elemental carbon (EC) in airborne particulate matter involves collection on a quartz fiber filter and subsequent thermal-optical analysis. Although having been widely used in aerosol studies and in PM2.5 (fine particulate matter) chemical speciation monitoring networks in particular, this measurement approach is prone to several types of artifacts, such as the positive sampling artifact caused by the adsorption of gaseous organic compounds onto the quartz filter, the negative sampling artifact due to the evaporation of OC from the collected particles and the analytical artifact in the thermal-optical determination of OC and EC (which is strongly associated with the transformation of OC into char OC and typically results in an underestimation of EC). The presence of these artifacts introduces substantial uncertainties to observational data on OC and EC and consequently limits our ability to evaluate OC and EC estimations in air quality models. In this study, the influence of sampling frequency on the measurement of OC and EC was investigated based on PM2.5 samples collected in Beijing, China. Our results suggest that the negative sampling artifact of a bare quartz filter could be remarkably enhanced due to the uptake of water vapor by the filter medium. We also demonstrate that increasing sampling duration does not necessarily reduce the impact of positive sampling artifact, although it will enhance the analytical artifact. Due to the effect of the analytical artifact, EC concentrations of 48 h averaged samples were about 15 % lower than results from 24 h averaged ones. In addition, it was found that with the increase of sampling duration, EC results exhibited a stronger dependence on the charring correction method and, meanwhile, optical attenuation (ATN) of EC (retrieved from the carbon analyzer) was more significantly biased by the shadowing effect. Results from this study will be useful for the design of China's PM2.5 chemical speciation monitoring network, which can be expected to be inaugurated in the near future. © Author(s) 2015.

Wei W.,Beijing University of Technology | Wei W.,State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex | Cheng S.,Beijing University of Technology | Li G.,Beijing University of Technology | And 2 more authors.
Atmospheric Environment | Year: 2014

This study made a field VOCs (volatile organic compounds) measurement for a petroleum refinery in Beijing by determining 56 PAMS VOCs, which are demanded for photochemical assessment in US, and obtained the characteristics of VOCs emitted from the whole refinery and from its inner main devices. During the monitoring period, this refinery brought about an average increase of 61ppbv in the ambient TVOCs (sum of the PAMS VOCs) at the refinery surrounding area, while the background of TVOCs there was only 10-30ppbv. In chemical profile, the VOCs emitted from the whole refinery was characteristic by isobutane (8.7%), n-butane (7.9%), isopentane (6.3%), n-pentane (4.9%%), n-hexane (7.6%), C6 branched alkanes (6.0%), propene (12.7%), 1-butene (4.1%), benzene (7.8%), and toluene (5.9%). On the other hand, the measurement for the inner 5 devices, catalytic cracking units (CCU2 and CCU3), catalytic reforming unit (CRU), tank farm (TF), and wastewater treatment(WT), revealed the higher level of VOCs pollutions (about several hundred ppbv of TVOCs), and the individual differences in VOCs chemical profiles. Based on the measured speciated VOCs data at the surrounding downwind area, PMF receptor model was applied to identify the VOCs sources in the refinery. Then, coupling with the VOCs chemical profiles measured at the device areas, we concluded that CCU1/3 contributes to 25.9% of the TVOCs at the surrounding downwind area by volume, followed by CCU2 (24.7%), CRU (18.9%), TF (18.3%) and WT (12.0%), which was accordant with the research of US EPA (2008). Finally, ozone formation potentials of the 5 devices were also calculated by MIR technique, which showed that catalytic cracking units, accounting for about 55.6% to photochemical ozone formation, should be given the consideration of VOCs control firstly. © 2014 Elsevier Ltd.

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