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Cheng Y.,Tsinghua University | Engling G.,National Tsing Hua University | He K.-B.,Tsinghua University | He K.-B.,State Environmental Protection Key Laboratory of Sources | And 6 more authors.
Atmospheric Chemistry and Physics | Year: 2013

Biomass burning, the largest global source of elemental carbon (EC) and primary organic carbon (OC), is strongly associated with many subjects of great scientific concern, such as secondary organic aerosol and brown carbon which exert important effects on the environment and on climate in particular. This study investigated the relationships between levoglucosan and other biomass burning tracers (i.e., water soluble potassium and mannosan) based on both ambient samples collected in Beijing and source samples. Compared with North America and Europe, Beijing was characterized by high ambient levoglucosan concentrations and low winter to summer ratios of levoglucosan, indicating significant impact of biomass burning activities throughout the year in Beijing. Comparison of levoglucosan and water soluble potassium (K+) levels suggested that it was acceptable to use K+ as a biomass burning tracer during summer in Beijing, while the contribution of fireworks to K + could be significant during winter. Moreover, the levoglucosan to K+ ratio was found to be lower during the typical summer period (0.21 ± 0.16) compared with the typical winter period (0.51 ± 0.15). Levoglucosan correlated strongly with mannosan (R2 = 0.97) throughout the winter and the levoglucosan to mannosan ratio averaged 9.49 ± 1.63, whereas levoglucosan and mannosan exhibited relatively weak correlation (R 2 = 0.73) during the typical summer period when the levoglucosan to mannosan ratio averaged 12.65 ± 3.38. Results from positive matrix factorization (PMF) model analysis showed that about 50% of the OC and EC in Beijing were associated with biomass burning processes. In addition, a new source identification method was developed based on the comparison of the levoglucosan to K+ ratio and the levoglucosan to mannosan ratio among different types of biomass. Using this method, the major source of biomass burning aerosol in Beijing was suggested to be the combustion of crop residuals, while the contribution from softwood burning was also non-negligible, especially in winter. © 2013 Author(s).

Wang F.,Tsinghua University | Wang S.,Tsinghua University | Wang S.,State Environmental Protection Key Laboratory of Sources | Meng Y.,Tsinghua University | And 4 more authors.
Fuel | Year: 2016

Coal combustion is a predominant anthropogenic source of atmospheric mercury emissions. The oxidation and adsorption on the surface of fly ashes are crucial to mercury control. In this study, we discussed the mercury adsorption/oxidation mechanisms on the surface of fly ashes and different roles of organic and inorganic compositions based on the experimental results of a fixed-bed reactor and temperature programmed decomposition technique (TPDT). The results indicated that the fly ashes played significant roles in mercury oxidation and adsorption. The residual Cl element on the surface of fly ashes after pretreatment at 650 °C contributed to the oxidation and adsorption of mercury. The heterogeneous oxidation process in this study has been confirmed to follow an Eley-Rideal mechanism. Unburned carbon (UBC) is important for mercury oxidation and adsorption on fly ashes. O2 promoted mercury adsorption, but not oxidation. The adsorption capacity was greatly increased in a simulated flue gas, and the oxidation rate was 60%. Al2O3, Fe2O3 and TiO2 were capable of adsorbing mercury. Among these compounds, Al2O3 displayed the largest adsorption capacity. Mercury adsorption did not occur on the surface of CaO and MgO. The flue gas compositions exhibited no influences on the adsorption capacity for the above five metallic oxides. No metallic oxides catalyzed the mercury oxidation regardless of the flue gas composition. © 2015 Elsevier Ltd. All rights reserved.

Zhang L.,Tsinghua University | Wang S.X.,Tsinghua University | Wang S.X.,State Environmental Protection Key Laboratory of Sources | Wang L.,Tsinghua University | And 2 more authors.
Atmospheric Chemistry and Physics | Year: 2013

Continuous measurements of atmospheric mercury concentration and speciation play a key role in identifying mercury sources and its behavior in the atmosphere. In this study, speciated atmospheric mercury including gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and particle-bound mercury (PBM) were continuously measured at Miyun, a rural site in Beijing, China, from December 2008 to November 2009. The average GEM, RGM and PBM concentrations were found to be 3.22 ± 1.74, 10.1 ± 18.8 and 98.2 ± 112.7 pgm-3, respectively, about 2-20 times higher than the background concentration of the Northern Hemisphere. The results indicated that atmospheric mercury concentrations in northern China were highly affected by anthropogenic emissions. The atmospheric mercury showed obvious seasonal variations, with the highest seasonal average GEM concentration in summer (3.48 ng m-3) and the lowest value in winter (2.66 ng m-3). In autumn and winter a diurnal variation of GEM was observed, with peak levels in the late afternoon till midnight. Most of the high RGM concentration values occurred in the afternoon of all seasons due to the higher oxidation. The PBM concentration was higher in early morning of all seasons because of the the temperature inversion that increases in depth as the night proceeds. The ratio of GEM to CO indicates that residential boilers play an important role in the elevation of GEM in winter. The ratio of RGM to O3 could be an indicator of the contribution of local primary sources. The ratio of PBM to PM2.5 reveals that the air mass from the east and southwest of the site in spring and summer carries more atmospheric mercury. The HYSPLIT back-trajectory analysis indicated that the monitoring site is affected by local, regional and interregional sources simultaneously during heavy pollution episodes. The results from the potential source contribution function (PSCF) model indicate that the atmospheric transport predominantly from the northwest contributes to the elevated atmospheric mercury in winter and autumn, while the North China Plain (NCP) region and the northern part of the Yangtze River Delta (YRD) region are the major source areas for mercury pollution in spring and summer. © 2013 Author(s).

Zhao B.,Tsinghua University | Wang S.X.,Tsinghua University | Wang S.X.,State Environmental Protection Key Laboratory of Sources | Liu H.,Tsinghua University | And 9 more authors.
Atmospheric Chemistry and Physics | Year: 2013

Nitrogen oxides (NOx) are key pollutants for the improvement of ambient air quality. Within this study we estimated the historical NOx emissions in China for the period 1995-2010, and calculated future NOx emissions every five years until 2030 under six emission scenarios. Driven by the fast growth of energy consumption, we estimate the NOx emissions in China increased rapidly from 11.0 Mt in 1995 to 26.1 Mt in 2010. Power plants, industry and transportation were major sources of NOx emissions, accounting for 28.4%, 34.0%, and 25.4% of the total NOx emissions in 2010, respectively. Two energy scenarios, a business as usual scenario (BAU) and an alternative policy scenario (PC), were developed to project future energy consumption. In 2030, total energy consumption is projected to increase by 64% and 27% from 2010 level respectively. Three sets of end-of-pipe pollution control measures, including baseline, progressive, and stringent control case, were developed for each energy scenario, thereby constituting six emission scenarios. By 2030, the total NOx emissions are projected to increase (compared to 2010) by 36% in the baseline while policy cases result in reduction up to 61% in the most ambitious case with stringent control measures. More than a third of the reduction achieved by 2030 between least and most ambitious scenario comes from power sector, and more than half is distributed equally between industry and transportation sectors. Selective catalytic reduction dominates the NOx emission reductions in power plants, while life style changes, control measures for industrial boilers and cement production are major contributors to reductions in industry. Timely enforcement of legislation on heavy-duty vehicles would contribute significantly to NOx emission reductions. About 30% of the NOx emission reduction in 2020 and 40% of the NOx emission reduction in 2030 could be treated as the ancillary benefit of energy conservation. Sensitivity analysis was conducted to explore the impact of key factors on future emissions. © 2013 Author(s).

Fu X.,Tsinghua University | Wang S.X.,Tsinghua University | Wang S.X.,State Environmental Protection Key Laboratory of Sources | Cheng Z.,Tsinghua University | And 5 more authors.
Atmospheric Chemistry and Physics | Year: 2014

Dust invasion is an important type of particle pollution in China. During 1 to 6 May in 2011, a dust event was observed in the Yangtze River Delta region (YRD). The highest PM10 (particles up to 10 μ in diameter) concentration reached over 1000 μg m-3 and the visibility was below 3 km. In this study, the Community Multi-scale Air Quality modeling system (CMAQ5.0) coupled with an in-line windblown dust model was used to simulate the formation, spatial and temporal characteristics of this dust event, and analyze its impacts. The threshold friction velocity for loose, fine-grained soil with low surface roughness in the dust model was revised based on Chinese data to improve the model performance. This dust storm broke out in Xinjiang and Mongolia during 28 to 30 April and arrived in the YRD region on 1 May. The transported dust particles contributed to the mean surface layer concentrations of PM10 in the YRD region 78.9% during 1 to 6 May with their impact weakening from north to south due to the removal of dust particles along the path. The dry deposition, wet deposition and total deposition of PM10 in the YRD reached 184.7 kt, 172.6 kt and 357.32 kt, respectively. The dust particles also had significant impacts on optical/radiative characteristics by absorption and scattering. In Shanghai, the largest perturbations of aerosol optical depth (AOD) and irradiance were about 0.8 DU and-130 W m-2, which could obviously influence the radiation balance in this region. The decrease of actinic fluxes impacts future photochemistry. In Shanghai, the negative effects on the NO2 and O3 photolysis could be −35% when dust particles arrived. The concentrations of O3 and OH were reduced by 1.5% and 3.1% in the whole of China, and by 9.4% and 12.1% in the YRD region, respectively. Such changes in O3 and OH levels can affect the future formation of secondary aerosols in the atmosphere by directly determining the oxidation rate of their precursors. The work of this manuscript is meaningful for understanding the dust emissions in China as well as for the application of CMAQ in Asia. It is also helpful for understanding the formation mechanism and impacts of dust pollution in the YRD. © 2014 Author(s).

Ancora M.P.,Tsinghua University | Zhang L.,Tsinghua University | Wang S.,Tsinghua University | Wang S.,State Environmental Protection Key Laboratory of Sources | And 3 more authors.
Energy Policy | Year: 2016

A new international treaty, Minamata Convention, identifies mercury (Hg) as a global threat to human health and seeks to control its releases and emissions. Coal-fired power plants are a major source of mercury pollution worldwide and are expected to be the first key sector to be addressed in China under Minamata Convention. A best available technique (BAT) adoption model was developed in the form of a decision tree and cost-effectiveness for each technological option. Co-benefit control technologies and their enhancement with coal blending/switching and halogen injection (HI) can provide early measures to help China meet the Minamata Convention obligations. We project future energy and policy scenarios to simulate potential national mercury reduction goals for China and estimate costs of the control measures for each scenario. The "Minamata Medium" scenario, equivalent to the goal of the US Mercury and Air Toxics Standards (MATS) rule, requires the application of activated carbon injection (ACI) and HI on 30% and 20% of power plants, respectively. The corresponding total costs would be $2.5 billion, approximately one-fourth the costs in the US. An emission limit of 3μg/m3 in 2030 was identified as a feasible policy option for China to comply with Minamata Convention. © 2015 Elsevier Ltd.

Song S.,Tsinghua University | Song S.,Massachusetts Institute of Technology | Wu Y.,Tsinghua University | Wu Y.,State Environmental Protection Key Laboratory of Sources | And 8 more authors.
Atmospheric Environment | Year: 2013

Black carbon (BC), carbon monoxide (CO), and particle number size distribution were measured near a major urban expressway of Beijing during summer and winter field campaigns in 2009. BC was also observed at urban and rural sites. The temporal variations of BC and its relationships with CO and particle number size distribution were analyzed. The average BC concentrations at the roadside site were 12.3 and 17.9μgm-3 during the summer and winter campaigns, respectively. BC concentrations ranked in the order of roadside>urban>rural. A general diurnal pattern at all sites showed that the higher BC levels were observed at night. The diurnal pattern of summertime BC at the roadside site followed the variations of heavy-duty diesel vehicles (HDDVs). The increased proportion of HDDVs at night contributed to high δBC/δCO ratios. This study suggests that HDDVs are an important contributor to nighttime BC and particle number concentrations of both Aitken and accumulation modes near major roadways in Beijing, especially in summer. © 2013 Elsevier Ltd.

Liu J.,Tsinghua University | Liu J.,State Environmental Protection Key Laboratory of Sources | Fung D.,University of California at Los Angeles | Jiang J.,Tsinghua University | And 2 more authors.
Indoor Air | Year: 2014

Ultrafine particle (UFP) emissions from three essential-oil-based mosquito repellent products (lemon eucalyptus (LE), natural insects (NI), and bite shield (BS)) were tested in a 386 l chamber at a high air exchange rate of 24/h with filtered laboratory air. Total particle number concentration and size distribution were monitored by a condensation particle counter and a scanning mobility particle sizer, respectively. UFPs were emitted from all three products under indoor relevant ozone concentrations (~ 17 ppb). LE showed a nucleation burst followed by a relatively stable and continuous emission while the other two products (NI and BS) showed episodic emissions. The estimated maximum particle emission rate varied from 5.4 × 109 to 1.2 × 1012 particles/min and was directly related to the dose of mosquito repellent used. These rates are comparable to those due to other indoor activities such as cooking and printing. The emission duration for LE lasted for 8-78 min depending on the dose applied while the emission duration for NI and BS lasted for 2-3 h. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Zheng G.J.,Tsinghua University | Cheng Y.,Tsinghua University | He K.B.,Tsinghua University | He K.B.,State Environmental Protection Key Laboratory of Sources | And 3 more authors.
Atmospheric Measurement Techniques | Year: 2014

The Sunset semi-continuous carbon analyzer (SCCA) is an instrument widely used for carbonaceous aerosol measurement. Despite previous validation work, in this study we identified a new type of SCCA calculation discrepancy caused by the default multipoint baseline correction method. When exceeding a certain threshold carbon load, multipoint correction could cause significant total carbon (TC) underestimation. This calculation discrepancy was characterized for both sucrose and ambient samples, with two protocols based on IMPROVE (Interagency Monitoring of PROtected Visual Environments) (i.e., IMPshort and IMPlong) and one NIOSH (National Institute for Occupational Safety and Health)-like protocol (rtNIOSH). For ambient samples, the IMPshort, IMPlong and rtNIOSH protocol underestimated 22, 36 and 12% of TC, respectively, with the corresponding threshold being ∼ 0, 20 and 25 I1/4gC. For sucrose, however, such discrepancy was observed only with the IMPshort protocol, indicating the need of more refractory SCCA calibration substance. Although the calculation discrepancy could be largely reduced by the single-point baseline correction method, the instrumental blanks of single-point method were higher. The correction method proposed was to use multipoint-corrected data when below the determined threshold, and use single-point results when beyond that threshold. The effectiveness of this correction method was supported by correlation with optical data. © Author(s) 2014. CC Attribution 3.0 License.

Wang S.,Tsinghua University | Wang S.,State Environmental Protection Key Laboratory of Sources | Xing J.,U.S. Environmental Protection Agency | Zhao B.,Tsinghua University | And 2 more authors.
Journal of Environmental Sciences (China) | Year: 2014

Understanding the effectiveness of national air pollution controls is important for control policy design to improve the future air quality in China. This study evaluated the effectiveness of major national control policies implemented recently in China through a modeling analysis. The sulfur dioxide (SO2) control policy during the 11th Five Year Plan period (2006-2010) had succeeded in reducing the national SO2 emission in 2010 by 14% from its 2005 level, which correspondingly reduced ambient SO2 and sulfate (SO4 2-) concentrations by 13%-15% and 8%-10% respectively over east China. The nitrogen oxides (NOx) control policy during the 12th Five Year Plan period (2011-2015) targets the reduction of the national NOx emission in 2015 by 10% on the basis of 2010. The simulation results suggest that such a reduction in NOx emission will reduce the ambient nitrogen dioxide (NO2), nitrate (NO3 -), 1-hr maxima ozone (O3) concentrations and total nitrogen deposition by 8%, 3%-14%, 2% and 2%-4%, respectively over east China. The application of new emission standards for power plants will further reduce the NO2, NO3 - 1-hr maxima O3 concentrations and total nitrogen deposition by 2%-4%, 1%-6%, 0-2% and 1%-2%, respectively. Sensitivity analysis was conducted to evaluate the inter-provincial impacts of emission reduction in Beijing-Tianjin-Hebei and the Yangtze River Delta, which indicated the need to implement joint regional air pollution control. © 2014 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences.

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