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Zhao S.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | Yu Y.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | Xia D.,Lanzhou University | Yin D.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | And 3 more authors.
Environmental Pollution

The dust origins of the two events were identified using HYSPLIT trajectory model and MODIS and CALIPSO satellite data to understand the particle size distribution during two contrasting dust events originated from Taklimakan and Gobi deserts. The supermicron particles significantly increased during the dust events. The dust event from Gobi desert affected significantly on the particles larger than 2.5 μm, while that from Taklimakan desert impacted obviously on the particles in 1.0-2.5 μm. It is found that the particle size distributions and their modal parameters such as VMD (volume median diameter) have significant difference for varying dust origins. The dust from Taklimakan desert was finer than that from Gobi desert also probably due to other influencing factors such as mixing between dust and urban emissions. Our findings illustrated the capacity of combining in situ, satellite data and trajectory model to characterize large-scale dust plumes with a variety of aerosol parameters. © 2015 Elsevier Ltd. All rights reserved. Source

Zhao S.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | Yu Y.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | Yin D.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | He J.,Nankai University | And 3 more authors.
Environment International

Long-term air quality data with high temporal and spatial resolutions are needed to understand some important processes affecting the air quality and corresponding environmental and health effects. The annual and diurnal variations of each criteria pollutant including PM2.5 and PM10 (particulate matter with aerodynamic diameter less than 2.5μm and 10μm, respectively), CO (carbon monoxide), NO2 (nitrogen dioxide), SO2 (sulfur dioxide) and O3 (ozone) in 31 provincial capital cities between April 2014 and March 2015 were investigated by cluster analysis to evaluate current air pollution situations in China, and the cities were classified as severely, moderately, and slightly polluted cities according to the variations. The concentrations of air pollutants in winter months were significantly higher than those in other months with the exception of O3, and the cities with the highest CO and SO2 concentrations were located in northern China. The annual variation of PM2.5 concentrations in northern cities was bimodal with comparable peaks in October 2014 and January 2015, while that in southern China was unobvious with slightly high PM2.5 concentrations in winter months. The concentrations of particulate matter and trace gases from primary emissions (SO2 and CO) and NO2 were low in the afternoon (~16:00), while diurnal variation of O3 concentrations was opposite to that of other pollutants with the highest values in the afternoon. The most polluted cities were mainly located in North China Plain, while slightly polluted cities mostly focus on southern China and the cities with high altitude such as Lasa. This study provides a basis for the formulation of future urban air pollution control measures in China. © 2015 Elsevier Ltd. Source

Du Y.,Peking University | Zhang Q.,Peking University | Chen Y.-L.,University of Hawaii at Manoa | Zhao Y.,Peking University | Wang X.,Weather Modification Office
Journal of Climate

The detailed spatial distributions and diurnal variations of low-level jets (LLJs) during early summer (May-July) in China are documented using 2006-11 hourly model data from the Weather Research and Forecasting (WRF) Model with a 9-km horizontal resolution. It was found that LLJs frequently occur in the following regions of China: the Tarim basin, northeastern China, the Tibetan Plateau (TP), and southern China. The LLJs over China are classified into two types: boundary layer jets (BLJs, below 1 km) and synoptic-system-related LLJs (SLLJs, within 1-4 km). The LLJs in the Tarim basin and the TP are mainly BLJs. The SLLJs over southern China and northeastern China are associated with the mei-yu front and northeast cold vortex (NECV), respectively. The BLJs in all regions show pronounced diurnal variations with maximum occurrences at nighttime or in the early morning, whereas diurnal variations of SLLJs vary, depending on the location. From the analysis of model data, the diurnal variation of BLJs is mainly caused by inertial oscillation at nighttime and vertical mixing in the boundary layer during daytime. Over northeastern China, SLLJ occurrences show little diurnal variation. Over southern China, two diurnal modes of SLLJs, propagation and stationary, exist and have seasonal variations, which is generally consistent with diurnal variations of precipitation. © 2014 American Meteorological Society. Source

Li H.,Weather Modification Office | Li H.,Fudan University | Han Z.,CAS Institute of Atmospheric Physics | Cheng T.,Fudan University | And 6 more authors.
Aerosol and Air Quality Research

Agricultural fire is an important source of atmospheric carbonaceous aerosols. To better understand biomass burning emission originating from fire over Asian agriculture areas and its transport into the downwind atmosphere, aerosols and major trace gases were measured continuously from 22 May to 30 June at Shanghai during the summer harvesttime of 2009. Water-soluble K material contained in aerosols showed a clear day-to-day pattern with an average of 1.25 ± 1.48 μg/m3. K ion loading and ratio of K ion to PM 10 drastically increased during 'K event' days, accompanying with high PM10, SO2, and NO2 levels. MODIS remote sensing fire map revealed about 80% agricultural fires occurred in the agriculture areas of Anhui, Jiangsu, Shandong and Henan provinces. Four potential source areas of agricultural fires, identified as Shanghai, Zhejiang, Jiangsu and Anhui provinces, had significant contributions to worsen the air quality of Shanghai during the harvest season. © Taiwan Association for Aerosol Research. Source

Xue M.,Chinese Academy of Meteorological Sciences | Ma J.,Chinese Academy of Meteorological Sciences | Li Y.,Nanjing University of Information Science and Technology | Zhu S.,Chinese Academy of Meteorological Sciences | And 7 more authors.
Atmospheric Environment

North China, or Huabei in Chinese, is one of the most severely polluted regions in China. There are many large, complex and strong emission sources in Beijing, Tianjin and Tangshan (together called Jing-Jin-Tang in Chinese) and other urban and industrial centers in Huabei, and the chemical characteristics of air masses coming from these pollution centers are expected to be quite different. As part of the project "Influence of Pollution on Aerosols and Cloud Microphysics in North China (IPAC-NC)", surface ozone and related trace gases were measured at the Xin'an rural station (39.73°N, 117.51°E), located in the central part of larger Jing-Jin-Tang area, during 2 April-16 May 2006. Here we investigate the chemical characteristics and impact of air masses from these different pollution hotspots on the regional distributions of ozone and nitrogen oxides in Huabei, based on measurement data as well as a regional chemical transport model. Simulated reactive nitrogen compounds are attributed to the different emission sources in the Huabei region using the tracer-tagging method implemented in the model. We find that the chemical characteristics of pollution plumes from different urban and industrial centers are rather different. The OPEx, defined as ozone production efficiency of nitrogen oxides (NOx), for general pollution plumes from Beijing, Tianjin, Tangshan and Shijiazhuang are estimated to be 3.35, 2.75, 1.43 and 2.33 mol mol-1, respectively. During the IPAC-NC field campaign period, the Xin'an site was influenced alternatively by air masses from Beijing and Tianjin megacities and the Tangshan industrial area. The estimated OPEx in Beijing, Tianjin and Tangshan air masses arriving at Xin'an are comparable to those in their general pollution plumes. This indicates that air masses from different urban and industrial centers in Huabei also maintain their different chemical characteristics while being transported to the rural areas. © 2013 Elsevier Ltd. Source

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