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Li J.,CAS Institute of Atmospheric Physics | Wang Z.,CAS Institute of Atmospheric Physics | Zhuang G.,Fudan University | Luo G.,CAS Institute of Atmospheric Physics | And 2 more authors.
Atmospheric Chemistry and Physics | Year: 2012

Mixing of Asian mineral dust with anthropogenic pollutants allows pollutants (e.g. sulfate and nitrate) to be transported over longer distances (e.g. to the northern Pacific, even to North America) along with dust particles. This mixing therefore affects the atmospheric and oceanic environment at local, regional and even continental scales. In this study, we used a three-dimensional regional chemical transport model (Nested Air Quality Predicting Modeling System, NAQPMS) to examine the degree of mixing between Asian mineral dust and anthropogenic pollutants in a super-duststorm event during 19-22 March 2010. Influences of the mixing processes on regional atmospheric environmental and oceanic biogeochemical cycles were also investigated. A comparison with measurements showed that the model reproduced well the trajectory of long-range dust transport, the vertical dust profile, and the chemical evolution of dust particles. We found that along-path mixing processes during the long-range transport of Asian dust led to increasingly polluted particles. As a result, ∼60% of the sulfate and 70-95% of the nitrate in the downwind regions was derived from active mixing processes of minerals with pollutants sourced from the North China Plain and enhanced by transport over South China. This mixing had a significant impact on the regional-scale atmospheric composition and oceanic biogeochemical cycle. Surface HNO 3, SO 2 and O3 were decreased by up to 90%, 40% and 30%, respectively, due to the heterogeneous reactions on dust particles. Fe solubility rose from ∼0.5% in the Gobi region to ∼3-5% in the northwestern Pacific, resulting from oxidization of SO 2 on dust particles. Total Fe(II) deposition in the ocean region of East Asia reached 327 tons during the 4-day dust event, and created a calculated primary productivity of ∼520 mgC m -2 d -1 in the Kuril Islands, which can support almost 100% of the observed mean marine primary productivity in spring in this region (526 mgC m -2 d -1). © 2012 Author(s).

Huang K.,Fudan University | Huang K.,University of Tennessee at Knoxville | Zhuang G.,Fudan University | Lin Y.,Fudan University | And 5 more authors.
Atmospheric Chemistry and Physics | Year: 2013

Three field campaigns were conducted before, during, and after the 2010World Expo in Shanghai, aiming to understand the response of secondary aerosol components to both control measures and human activities. In spring, PM2.5 (particulate matter) averaged 34.5±20.9 μgm -3 with a severe pollution episode influenced by a floating dust originating from northwestern China on 26-28 April, right before the opening of the expo.With the approaching expo a significant increasing trend of SNA (SO4 2- , NO3 - , and NH+ 4 ) concentrations was observed from 22 April to 2 May, attributed to the enhanced human activities. Nitrate had the most significant daily increasing rate of 1.1 μgm-3d-1 due to enhanced vehicle emission. In summer, two intensive pollution episodes were found to be a mixed pollution of SNA with biomass burning due to loose control of post-harvest straw burning. In the autumn phase of the expo, before the closing of the expo (20-30 October), the air quality over Shanghai was much better than ever before. However, the air quality rapidly plummeted as soon as the expo was announced closed. SNA increased 3-6 fold to be 42.1 and 68.2 μgm-3 on 31 October and 1 November, respectively, as compared to 20-30 October. Of which, nitrate increased most ∼5-8 fold, indicating the serious impact from enhanced vehicle emission. Compared to the spring and summer of 2009, NO3 - increased 12- 15% while SO4 2- showed reductions of 15-30 %. Continuous desulfurization of SO2 emission from power plants in recent years was responsible for the lowered SO4 2- , while increased traffic emission from the tremendous number of expo visitors was the major contributor to the increased NO3 - . Compared to the autumn of 2009, all the ion components increased in 2010, owing to the lifting of emission control measures after the expo. SO4 2- was found least increased while NO3 - and Ca2+ had tremendous increases of 150 and 320 %, respectively. The anthropogenic Ca as a tracer from construction dust increased from 2.88±1.85 μgm-3 during the expo to 6.98±3.19 μgm-3 during the post-expo period, attributed to the resumption of construction works after the expo. The lack of successive control measures with the loose regulations after the expo were responsible for this jump of the bad quality. The ratio of NO3 - /SO4 2- in PM2.5 over Shanghai had a significant increasing trend from ∼0.3 in the early 2000s to more than 1.0 in 2010, indicating the increasing role of mobile sources. Reducing NOx emission will be China's priority in the future in order to improve the air quality over the megacities. In addition, lowering mineral aerosol components (e.g., Ca2+) was also demonstrated to be beneficial for alleviating air pollution in China. This study demonstrated that stringent emission control measures aiming at megaevents in China could achieve positive benefits on improving the air quality in a short term. However, persistent efforts of curbing the anthropogenic emission remain a long way to go in the future. © Author(s) 2009.

Huang K.,University of Tennessee at Knoxville | Huang K.,Fudan University | Zhang X.,National Satellite Meteorological Center | Lin Y.,Shanghai Environmental Monitoring Center
Atmospheric Research | Year: 2015

Observations from space were used to evaluate the effect of emission control measures on the changes of air pollutants in Beijing and its surroundings during the 2014 Asia-Pacific Economic Cooperation (APEC) Summit held in Beijing. Compared to the past three years (2011-2013), NO2 tropospheric vertical column densities in 2014 were found to exhibit almost across-the-board significant reductions over the North China Plain, suggesting the effectiveness of the national policy on NOx emission reduction during China's 12th "Five-Year-Plan". During the APEC period (Nov. 3-11), AOD and AAOD were found reduced the most in Beijing, followed by Hebei province. Stringent emission control measures implemented in Beijing and the regional joint control over the surroundings especially in Hebei were responsible for the good air quality and so-called "APEC Blue". However, air quality plummeted during the post-APEC period (Nov. 12-30), which was largely related to the lifting of local and regional joint emission control measures. By applying a spatial correlation analysis method, the potential emission source regions impacting air quality of Beijing included widespread areas in Hebei, Shandong, Shanxi, and Tianjin in the past three years (2011-2013). While during the study period in 2014, areas impacting Beijing evidently shrank and were limited within Hebei, suggesting evident effects of intense emission perturbations on lowering the extent of regional transport. This study indicates short-term measures did fix the air pollution problems in China but a permanent solution is still a tremendous challenge. © 2015 Elsevier B.V.

Huang K.,Fudan University | Huang K.,University of Tennessee at Knoxville | Zhuang G.,Fudan University | Lin Y.,Fudan University | And 9 more authors.
Atmospheric Chemistry and Physics | Year: 2012

An intensive aerosol and gases campaign was performed at Shanghai in the Yangtze River Delta region over Eastern China from late March to early June 2009. This study provided a complementary picture of typical haze types and the formation mechanisms in megacities over China by using a synergy of ground-based monitoring, satellite and lidar observations. During the whole study period, several extreme low visibility periods were observed with distinct characteristics, and three typical haze types were identified, i.e. secondary inorganic pollution, dust, and biomass burning. Sulfate, nitrate and ammonium accounted for a major part of PMmass during the secondary inorganic pollution, and the good correlation between SONOx/CO and PMindicated that coal burning and vehicle emission were the major sources. Large-scale regions with high AOD (aerosol optical depths) and low Ångström exponent were detected by remote-sensing observation during the dust pollution episode, and this episode corresponded to coarse particles rich in mineral components such as Al and Ca contributing 76.8% to TSP. The relatively low Ca/Al ratio of 0.75 along with the air mass backward trajectory analysis suggested the dust source was from Gobi Desert. Typical tracers for biomass burning from satellite observation (column CO and HCHO) and from ground measurement (CO, particulate K+, OC, and EC) were greatly enhanced during the biomass burning pollution episode. The exclusive linear correlation between CO and PMcorroborated that organic aerosol dominated aerosol chemistry during biomass burning, and the high concentration and enrichment degree of arsenic (As) could be also partly derived from biomass burning. Aerosol optical profile observed by lidar demonstrated that aerosol was mainly constrained below the boundary layer and comprised of spheric aerosol (depolarization ratio <5%) during the secondary inorganic and biomass burning episodes, while thick dust layer distributed at altitudes from near surface to 1.4 km (average depolarization ratio Combining double low line 0.122 ± 0.023) with dust accounting for 44-55% of the total aerosol extinction coefficient during the dust episode. This study portrayed a good picture of the typical haze types and proposed that identification of the complicated emission sources is important for the air quality improvement in megacities in China. © 2012 Author(s). CC Attribution 3.0 License.

Wang Q.,Shanghai Environmental Monitoring Center
Research of Environmental Sciences | Year: 2013

HYSPLIT4.9 as a trajectory model and Global Data Assimilation System (GDAS) meteorological data were used to compute the backward air flow trajectories from December 2010 to November 2011. This study focused on four seasons. Analysis of the effect of different seasons and trajectories on various pollutants based upon cluster analysis and corresponding pollutants concentration such as SO2, NO2 and PM10 was conducted. In addition, the potential contribution algorithm combined with weight factors (WPSCF) was utilized to study the spatial probability distribution of PM10 and NO2 area sources for four seasons. The results showed the direction of the air flow in Shanghai was associated with temporal changes, Northwestern and southwestern winds were dominant in autumn, winter and spring. There would be a significant impact on Shanghai, when a trajectory passed through major anthropogenic emission areas. This phenomenon occurred in high ρ(PM10), ρ(SO2) and ρ(NO2) values, which is 162, 74 and 53 μg/m3. During summer, ρ(PM10), ρ(SO2) and ρ(NO2) were relatively lower due to cleaner air from the ocean, which is 47, 19 and 36 μg/m3. In seasons of autumn, winter and spring, Shanghai has a similar probability distribution characteristic as in those PM10 and SO2 sources areas. High WPSCF values (0.2-0.4) were concentrated in the south of Jiangsu province. Furthermore, contribution from Inner Mongolia, Henan, and Anhui provinces could not be ignored since the study revealed that these regions are the potential sources of PM10 and NO2 in Shanghai. In summer, WPSCF value outside Shanghai was almost lower than 0.1, which demonstrates the contribution from area outside of Shanghai is insignificant.

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