Aerosol pollution in China： Present and future impact on environment

With its dense population, rapid economic growth and dramatic rate of urbanization, China is experiencing extreme air pollution problems. This is particularly the case in Central-Eastern China （CEC）, where the two major cities of Beijing and Tianjin are located, in the Yangtze-River Delta （YRD） with the city of Shanghai, and in the Pearl-River Delta （PRD） with the mega-city of Gnangzhou. Space observations show that the atmospheric aerosol load in these three regions is considerably higher than, for example, in the urbanized regions of Europe and North America. The high aerosol concentrations in these regions have raised many environmental problems, such as impact on human health, visibility, and climate changes. In this paper, several crucial issues regarding aerosol pollution in these highly populated regions （CEC, YRD, and PRD） are discussed, including （1） when the aerosol load starts to rapidly increase in these regions; （2） how the high aerosol concentrations affects the environment; and （3） what the potential consequences are under possible low aerosol load in these regions. Discussion on these crucial issues might lead to some insight for better understanding of the characterizations of aerosol pollution due to the rapid economical development in China.     

Modeling nitrate aerosol distributions and its direct radiative forcing in East Asia with RAMS-CMAQ

The geographical and seasonal characteristics in nitrate aerosol and its direct radiative forcing over East Asia are analyzed by using the air quality modeling system RAMS-CMAQ coupled with an aerosol optical properties/radiative transfer module. For evaluating the model performance, nitrate ion concentration in precipitation, and mixing ratios of PM₁₀, and some gas precursors of aerosol during the whole year of 2007 are compared against surface observations at 17 stations located in Japan, Korea, and China, and the satellite retrieved NO₂ columns. The comparison shows that the simulated values are generally in good agreement with the observed ones. Simulated monthly averaged values are mostly within a factor of 2 of the measurements at the observation stations. The distribution patterns of NO₂ from simulation and satellite measurement are also similar with each other. Analysis of the distribution features of monthly and yearly averaged mass concentration and direct radiative forcing (DRF) of nitrate indicates that the nitrate aerosol could reach about 25–30% of the total aerosol mass concentration and DRF in Sichuan Basin, Southeast China, and East China where the high mass burden of all major aerosols concentrated. The highest mass concentration and strongest DRF of nitrate could exceed 40 μg/m³ and ?5 W/m², respectively. It also indicates that other aerosol species, such as carbonaceous and mineral particles, could obviously influence the nitrate DRF for they are often internally mixed with each other.     

Zr-4合金在Na2SO4溶液中的微动腐蚀磨损特性

采用微动摩擦磨损试验机进行了Zr-4合金／Al2O3摩擦副在空气、纯水和Na2SO4溶液3种介质中的微动腐蚀磨损试验，采用三坐标表面粗糙度仪测量磨损体积损失，利用脉冲电位评价微动磨损所产生的新生面与磨损表面的关系．结果表明：新生面的面积小于磨痕面积而大于实际接触面积；在Na2SO4溶液中摩擦副的磨损量比窄气和纯水中高10倍，但摩擦系数比空气和纯水中小；纯水中Zr-4合金的磨损量等于电位为-2000mV时Na2SO4溶液中的磨损量；在腐蚀环境中磨损量随电位的增高而增大，Zr-4合金的微动腐蚀磨损机制为电化学作用引起的腐蚀磨损．     

铝氧比对含铝炸药性能影响的数值模拟

为了研究铝氧比对含铝炸药在混凝土介质中爆炸性能的影响,采用数值模拟与实验相结合的方法,针对铝氧比分别为0、0.257、0.632的含铝炸药,利用AUTODYN有限元程序建立计算模型,计算了柱形装药在混凝土介质中的爆炸破坏过程,并且得到了在比例距离为2.5~10的范围内,3种含铝炸药爆炸形成的冲击波压力时程曲线。计算结果表明:冲击波峰值压力的衰减指数随炸药的铝氧比增大而减小,衰减指数分别为2.1、1.71、1.60;另外,当含铝炸药的铝氧比为0.257时比冲击波能最大。     

Seasonal variations and sources of mass and chemical composition for PM10 aerosol in Hangzhou,China

Aerosol observation was conducted for four seasons from September 2001 to August 2002 at five sampling sites in Hangzhou, South China, on PM10 mass, 22 elements （Na, Mg, AI, Si, P, S, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As. Se, Br, Cd, Ba, and Pb）, 5 major ions （F^-, Cl^ , NO3^-, SO4^2- , and NH4^＋）, and organic and elemental carbon （OC and EC）, showing that PM10 mass ranged from 46.7 to 270.8 μg/m^3, with an annual average of 119.2 μg/m^3. Na, AI, Si, S, K, Ca, and Fe were the most abundant elements in PM10, most of S being in the form of SO4^2- . SO4^2-, NO3^-, and NH4^＋ were the major ions, which contributed to about 20% of the PM10 mass. The mean seasonal concentrations for SO4^2- , averaged over all sites, were found to be 18.0, 18.5, 24,Z and 21.4 μg/m^3, for spring, summer, autumn, and winter, respectively, while the corresponding loadings for NO3^- were 7.2, 4.7, 7.1, and 11.2 μg/m^3, and for NH4^＋ were 6.0, 5.9, 8.2, and 9.3 μg/m^3, in the form mostly of NH4NO3 in spring, autumn, and winter, and mostly of （NH4）2SO4 in summer. The low NO3^-/SO4^2- ratio found indicates coal combustion as the major source throughout the year. The mean annual concentrations of OC and EC in PM10 were found to be 21.4, and 4.1 μg/m^3, respectively. Material balance calculation indicated that fugitive dust, the secondary aerosol, and carbonaceous matter were the most abundant species in PM10 for the four seasons, as is characteristic for cities in South China.     

Aerosol composition,sources, and secondary processing during autumn at a regional site in the Beijing–Tianjin–Hebei region

Air pollution is serious during autumn in the Beijing–Tianjin–Hebei (BTH) region, but there are few studies that have utilized real-time observations and source apportionment of the autumn submicron aerosols in this region. In this study, a quadrupole aerosol chemical speciation monitor (Q-ACSM) was deployed for the real-time measurement of the non-refractory compositions of submicron aerosols (NR-PM₁) at a regional site (Xianghe) from October 3 to November 14, 2017. The results showed that nitrate was the largest inorganic aerosol, and the oxygenated organic aerosol (OOA) was the largest organic aerosol in Xianghe. Hydrocarbon-like OA (HOA) was the largest organic aerosol When the NR-PM₁ mass concentrations increased from the lowest to the highest bins, nitrate and biomass burning OA (BBOA) showed increasing trends in the suburban area. Enhanced nitrate formation during the pollution episodes resulted from both photochemical and aqueous processing. To reduce the particulate matter (PM_2.5) concentrations and eliminate heavy pollution episodes, control measures should focus on reducing NO_x, NH₃, and volatile organic compound (VOC_s) emissions.     

Evolution of planetary boundary layer under different weather conditions,and its impact on aerosol concentrations

A field experiment was conducted in Tianjin, China from September 9–30, 2010, focused on the evolution of Planetary Boundary Layer (PBL) and its impact on surface air pollutants. The experiment used three remote sensing instruments, wind profile radar (WPR), microwave radiometer (MWR) and micro-pulse lidar (MPL), to detect the vertical profiles of winds, temperature, and aerosol backscattering coefficient and to measure the vertical profiles of surface pollutants (aerosol, CO, SO₂, NO_x), and also collected sonic anemometers data from a 255-m meteorological tower. Based on these measurements, the evolution of the PBL was estimated. The averaged PBL height was about 1000–1300 m during noon/afternoon-time, and 200–300 m during night-time. The PBL height and the aerosol concentrations were anti-correlated during clear and haze conditions. The averaged maximum PBL heights were 1.08 and 1.70 km while the averaged aerosol concentrations were 52 and 17 μg/m³ under haze and clear sky conditions, respectively. The influence of aerosols and clouds on solar radiation was observed based on sonic anemometers data collected from the 255-m meteorological tower. The heat flux was found significantly decreased by haze (heavy pollution) or cloud, which tended to depress the development of PBL, while the repressed structure of PBL further weakened the diffusion of pollutants, leading to heavy pollution. This possible positive feedback cycle (more aerosols → lower PBL height → more aerosols) would induce an acceleration process for heavy ground pollution in megacities.     

Long-term trend in aerosol optical depth from 1980 to 2001 in north China

Using the Total Ozone Mapping Spectrometer (TOMS) monthly aerosol optical depth (AOD) at 500 nm data from 1980 to 2001 in north China, the spatial and temporal variations of AOD were examined. Seasonal AODs in Taldimakan Desert were 0.69 and 0.44 in spring and summer,respectively, which were mainly due to frequent occurrences of dust events in this region. Dust activities in spring also led to high aerosol loading in Gobi Desert and in northeast China where spring AODs were 0.33 and 0.29, respectively. Heavily impacted by events such as volcano eruption, forest fires and extraordinary dust storms, AODs showed large inter-annual variations. A decreasing tendency in AOD was observed in north China during 1980-1991, though a reverse tendency was revealed during 1997-2001, especially for spring AOD in northeast China. Further study is required to figure out how much human activities have contributed to the AOD tendency in north China.     

大型复杂松散堆积体形成机制的内外动力耦合作用初 探

在我国西部山区广泛发育和分布第四纪大型复杂松散堆积体,这是一套介于土、岩之间的过渡类型的地质体;其成因复杂,主要包括残坡积物、崩滑堆积体、冲洪积物、冰碛物和冰水沉积物等两种或多种组合混杂堆积,明显区别于东部平原区的单一成因类型。本文通过资料对比分析,对大型复杂松散堆积体的一般特征、主要类型和区域分布规律进行了系统总结,最后从"耦合"的角度来探讨其成因机制,并提出河谷型松散堆积体的内外动力耦合概念模型,研究认为大型复杂松散堆积体属于典型的内外动力耦合作用产生的多期次、成因复杂的复合地质体。     

Long-range transport of organic aerosol to Cape Hedo,Japan

An investigation at Cape Hedo, Japan, from 2005 to 2006, focused on the long-range transport of organic aerosol （OA） from the Asian continent. An Aerodyne aerosol mass spectrometer was used to investigate the OA data collected over the study. OA concentrations were low from July to September and peaked during March and April. Based on air mass origins, four OA source regions were identified： northern China, southern China, Japan, and Korea. OA concentrations measured at Cape Hedo from the four sources did not exhibit large differences. Conversely, the frequencies of the air masses reaching Cape Hedo from the different regions varied considerably. Northern China was identified as the primary source of organic aerosols at Cape Hedo. Examination of variations in the ratio of m/z 44 to OA concentrations with transport time showed that OAs were partially oxidized during transport     

Elemental compositions of PM2.5 and TSP in Lijiang,southeastern edge of Tibetan Plateau during pre-monsoon period

PM_2.5 and total suspended particulate (TSP) samples were collected at Lijiang, southeastern Tibetan Plateau, China. Sixteen elements (Al, Si, S, K, Ca, Cr, Mn, Ti, Fe, Ni, Zn, As, Br, Sb, Pb and Cu) were analyzed to investigate their elemental compositions during the pre-monsoon period. The results showed that Ca was the most abundant element in both PM_2.5 and TSP samples. The enrichment factors (EFs) of Si, Ti, Ca, Fe, K and Mn were all below 10 for both PM_2.5 and TSP, and these elements also had lower PM_2.5/TSP ratios (0.32–0.34), suggesting that they were mainly derived from crustal sources. Elements Cu, Zn, S, Br and Sb showed strong enrichment in PM_2.5 and TSP samples, with their PM_2.5/TSP ratios ranging from 0.66 to 0.97, indicating that they were enriched in the fine fractions and influenced by anthropogenic sources. Analysis of the wind field at 500 hPa and calculations of back trajectories indicated that Al, Si, Ca, Ti, Cr, Mn and Fe can be influenced by transport from northwestern China during the dust-storm season, and that S, K, Ni, Br and Pb reached high concentrations during westerly transport from south Asia. Combined with the principle component analysis and correlation analysis, elements of PM_2.5 samples were mainly from crustal sources, biomass burning emissions and regional traffic-related sources.     

Long-term trend in aerosol optical depth from 1980 to 2001 in north China

Using the Total Ozone Mapping Spectrometer （TOMS） monthly aerosol optical depth （AOD） at 500 nm data from 1980 to 2001 in north China, the spatial and temporal variations of AOD were examined. Seasonal AODs in Taklimakan Desert were 0.69 and 0.44 in spring and summer, respectively, which were mainly due to frequent occurrences of dust events in this region. Dust activities in spring also led to high aerosol loading in Gobi Desert and in northeast China where spring AODs were 0.33 and 0.29, respectively. Heavily impacted by events such as volcano eruption, forest fires and extraordinary dust storms, AODs showed large inter-annual variations. A decreasing tendency in AOD was observed in north China during 1980-1991, though a reverse tendency was revealed during 1997-2001, especially for spring AOD in northeast China. Further study is required to figure out how much human activities have contributed to the AOD tendency in north China.     

Long-range transport of organic aerosol to Cape Hedo,Japan

An investigation at Cape Hedo, Japan, from 2005 to 2006, focused on the long-range transport of organic aerosol (OA) from the Asian continent. An Aerodyne aerosol mass spectrometer was used to investigate the OA data collected over the study. OA concentrations were low from July to September and peaked during March and April. Based on air mass origins, four OA source regions were identified: northern China, southern China, Japan, and Korea. OA concentrations measured at Cape Hedo from the four sources did not exhibit large differences. Conversely, the frequencies of the air masses reaching Cape Hedo from the different regions varied considerably. Northern China was identified as the primary source of organic aerosols at Cape Hedo. Examination of variations in the ratio of m/z 44 to OA concentrations with transport time showed that OAs were partially oxidized during transport     

Impacts of biomass-burning on aerosol properties of a severe haze event over Shanghai

Anthropogenic aerosols have significant impacts on the environment and human health in the Yangtze River Delta region, one of the most densely populated regions in the world. A biomass-burning plume swept across this area (Shanghai) in May 2009, leading to changes in the physical and optical properties of aerosols, which were investigated using ground-based remote sensing and in situ measurements via comparisons with dust pollution and background conditions. Experiments show that the biomass-burning plume led to an increase in the average aerosol optical depth (AOD) at 500 nm from 0.73 to 1.00 (37% higher), an absorption Angstrom exponent (AAE) of 1.48, and an increase in the Angstrom exponent (α) up to 1.53. Furthermore, local dust aerosols derived from road dust and/or construction dust also led to higher values of AOD (2.68) and AAE (2.16), and a daily average value of α of 1.05. For the biomass-burning plume, the aerosol particles exhibited significant variations in short-wavelength spectra. The single scattering albedo at 670 nm decreased remarkably under the influence of the biomass-burning plume, indicating the significant absorptive ability of the biomass-burning pollution and higher ratio of absorption aerosols within the plume. Under the effects of the biomass-burning, the volume concentration of fine-mode aerosols increased significantly and the PM-fine/PM-coarse volume concentration ratio reached 12.33. This relatively large change in fine-mode particles indicates that biomass-burning has a greater impact on fine-mode aerosols than on coarse-mode aerosols.     

Atmospheric extinction properties in Shenyang,China

Atmospheric visibility impairment due to human activities is becoming increasingly significant in metropolitan Shenyang,China.In this study,hourly data of relevant factors throughout the year 2010 in Shenyang were used to evaluate the local atmospheric extinction properties.The results show that the average coefficient of total extinction and aerosol single-scattering albedo in 2010 were 622.72 Mm~(-1)and 0.87,respectively,values that are characteristic of the "municipal pollution type".Visibility is most impaired during winter and especially in January.The coefficient of total extinction exhibits a single daily cycle with a maximum at 5-6 am and a minimum at 3 pm.The mean extinction contributions of the constituents,from high to low,were particle scattering(87.49%),particle absorption,gas absorption,and gas scattering.The extinction contribution of gas molecules was little more than 4.5%,far smaller than that of particles.Scattering by particles was the main contributor to extinction,especially in the morning and around midnight.     

Comparison of aerosol characteristics during haze periods over two urban agglomerations in China using CALIPSO observations

Using CALIPSO (cloud-aerosol lidar and infrared pathfinder satellite observation) vertical observation data during haze periods from January 2007 to December 2008, we analyzed differences in aerosol characteristics near the surface, as well as in the middle troposphere between the Beijing–Tianjin–Hebei metropolitan region (Area A) and the Yangtze River Delta region (Area B) in China. One significant difference was that haze pollution in Area A was related to local and non-local aerosols, while in Area B it was related to local anthropogenic sources. In all seasons apart from autumn, aerosol pollution in Area A was more severe than in Area B, both near the surface and at higher altitudes. In Area A, non-spherical aerosols were dominant from 0 to 4 km in spring, summer, and winter; while in autumn, there were considerably high numbers of non-spherical aerosols below 0.5 km, and near-spherical aerosols from 0.5 to 4 km. In Area B, both near-spherical and non-spherical aerosols were common in all seasons. Moreover, aerosols with attenuated color ratios of 0–0.2 were more common in all seasons in Area A than in Area B, indicating that fine particle pollution in Area A was more serious than in Area B. Finally, relatively large aerosols linked to gravity settling appeared more frequently near the surface in Area A than in Area B.     

爆炸荷载和地应力耦合作用下煤体裂纹扩展的模型实验研究

为了研究地应力作用下煤体柱状装药预裂爆破裂纹扩展,以Froude比例法为指导,建立煤层预裂爆破的模型实验,并对地应力和爆炸荷载耦合作用下煤体中的裂纹扩展机理进行了研究。该模型描述了在爆炸荷载作用下的宏观破坏现象。研究结果表明:模型实验与现场试验结果基本一致;裂纹主要是由压缩波和卸载波共同作用形成的;地应力对裂纹的发展具有抑制作用;主应力对于拉伸裂纹的发展具有明显的导向作用。     

Atmospheric extinction properties in Shenyang,China

Atmospheric visibility impairment due to human activities is becoming increasingly significant in metropolitan Shenyang, China. In this study, hourly data of relevant factors throughout the year 2010 in Shenyang were used to evaluate the local atmospheric extinction properties. The results show that the average coefficient of total extinction and aerosol single-scattering albedo in 2010 were 622.72 Mm⁻¹ and 0.87, respectively, values that are characteristic of the “municipal pollution type”. Visibility is most impaired during winter and especially in January. The coefficient of total extinction exhibits a single daily cycle with a maximum at 5–6 am and a minimum at 3 pm. The mean extinction contributions of the constituents, from high to low, were particle scattering (87.49%), particle absorption, gas absorption, and gas scattering. The extinction contribution of gas molecules was little more than 4.5%, far smaller than that of particles. Scattering by particles was the main contributor to extinction, especially in the morning and around midnight.     

Large-scale dynamics in high Reynolds number jets and jet flames

The far-field large-scale dynamics of a momentum-driven Re = 2 × 10⁸ non-reacting jet and a Re = 3 × 10⁷ jet diffusion flame are presented and compared. The results are derived from computer graphic volume rendering of a set of sequential images of each flow. When compared to conventional display techniques, volume rendering, by allowing many frames of a movie sequence to be presented simultaneously, more clearly shows the detailed flow evolution. For the non-reacting jet we see the passage and growth of large-scale organized structures up through the jet column, the axial velocity decay of the structures, the fluid entrainment patterns, and occasional pairing events. A rendering of a non-sequential set of images shows no discernible organized component. Volume rendering of the reacting jet shows a similar pattern of burning large-scale organized structures which convert over considerable axial distances but without the corresponding velocity decay, similar to observations of laboratory flames. The images presented here are believed to be some of the most direct visual evidence to date for large-scale organized motions in the far-field of high Reynolds number, fully developed jets and jet flames. Since conditional sampling techniques are not used, we believe that the volume renderings seen here are likely to be representative of the natural development of jet flows.     

Validation of MODIS and Deep Blue aerosol optical depth retrievals in an arid/semi-arid region of northwest China

The global aerosol optical depth (AOD or τ) has been retrieved using the Dark Target algorithm (the C004 and C005 products) and the Deep Blue algorithm (DB product). Few validations have thus far been performed in arid/semi-arid regions, especially in northwest China. The ground-based remote sensing of AOD from sun photometers at four sites in Xinjiang during the years 2002–2003 is used to validate aerosol products, including C004, C005 and DB of the Moderate Resolution Imaging Spectroradiometer (MODIS). The results show substantial improvement in the C005 aerosol product over the C004 product. The average correlation coefficient of regression with ground measurements increased from 0.59 to 0.69, and the average offset decreased from 0.28 to 0.13. The slopes of the linear regressions tended to be close to unity. The percentage of AODs falling within the retrieval errors of 30% (or △τ = ±0.1 ± 0.2τ) increased from 16.1% to 45.6%. The best retrievals are obtained over an oasis region, whereas the worst are obtained over urban areas. Both the MODIS C004 and C005 products overestimate AOD, which is likely related to improper assumptions of the aerosol model and of the estimation of surface reflectance. An encouraging result has been derived with regard to validation of the DB AOD. Overall, the average offset, slope and correlation coefficient of regression with sun-photometer measurements are ?0.04, 0.88 and 0.85, respectively. Approximately 73% of the DB AOD retrievals fall within the expected error of 30%. Underestimation of the AOD by the DB products is observed. The aerosol model and estimations of surface reflectance in this region require further improvements.