SPATIAL AND SEASONAL DISTRIBUTIONS OF ATMOSPHERIC CARBONACEOUS AEROSOLS IN PEARL RIVER DELTA REGION, CHINA

Concentrations and spatial distributions of organic carbon (OC) and elemental carbon (EC) in atmospheric particles were measured at 8 sites in four cities (Hong Kong, Guangzhou, Shenzhen and Zhuhai) of Pearl River Delta Region (PRDR), China during 2001 winter period and 2002 summer period. PM2.5 (particie diameter smaller than 2.5 um) and PM10 (particie diameter smaller than 10 um) samples were collected on pre-fired quartz filters with mini-volume samplers and analyzed using thermal optical reflectance (TOR) method. The average PM2.5and PM10 Ievel were 60.1 and 93.1 μg·m-3, respectively, with PM2.5 constituting 65.3% of the PM10 mass. The average OC and EC concentrations in PM2.5 were 12.0 and 5.1 μg·m-3, respectively, while those in PM10 were 16.0 and 6.5 μg·m-3, respectively. The carbo-naceous aerosol accounted for 37.2% of the PM2.5 and 32.8% of the PM10. The highest concentrations of OC and EC were observed at Guangzhou city in both vvinter and summer seasons. The average OC/EC ratios were 2.     

Local and long-range transport influences on PM2.5 at a cities-cluster in northern China,during summer 2008

Hourly PM2.5 concentrations were observed simultaneously at a cities-cluster comprising 10 cities/towns in Hebei province in China from July 1 to 31, 2008. Among the 10 cities/towns, Baoding showed the high- est average concentration level （161.57μg/m3） and Yanjiao exhibited the lowest （99.35 μg/m3 ）. These observed data were also studied using the joint potential source contribution function with 24-h and 72-h backward trajectories, to identify more clearly the local and countrywide-scale long-range transport sources. For the local sources, three important influential areas were found, whereas five important influential areas were defined for long-range transport sources. Spatial characteristics of PM2.5 were determined by multivariate statistical analyses. Soil dust, coal combustion, and vehicle emissions might be the potential contributors in these areas. The results of a hierarchical cluster analysis for back trajectory endpoints and PM2.s concentrations datasets show that the spatial characteristics of PM2.5 in the cities-cluster were influenced not only by local sources, but also by long-range transport sources. Different cities in the cities-cluster obtained different weighted contributions from local or long-range transport sources. Cangzhou, Shijiazhuang, and Baoding are near the source areas in the south of Hebei province, whereas Zhuozhou, Yangfang, Yanjiao, Xianghe, and Langfang are close to the sources areas near Beijing and Tianjin.     

Effect of chemical composition of PM_(2.5) on visibility in Guangzhou,China,2007 spring

The object of this study was to investigate the correlation of visibility with chemical composition of PM2.5 in Guangzhou. In April 2007, 28 PM2.5 samples were collected daily at the monitoring station of the South China Institute of Environmental Sciences (SCIES), in urban Guangzhou. Water-soluble ionic species (Cl-, NO3-, SO42-, NH4+, K+, Na+, Ca2+, and Mg2+) and carbonaceous contents (OC and EC) of the PM2.5 samples were determined to characterize their impact on visibility impairment. The results showed that sulfate was the dominant species that affected both light scattering and visibility. The average percentage contributions of the visibility-degrading species to light scattering coefficient were 40% for sulfate, 16% for nitrate, 22% for organics, and 22% for elemental carbon. Because of its foremost effect on visibility, sulfate reduction in PM2.5 would effectively improve the visibility of Guangzhou.     

Spatiotemporal variations of PM_(2.5) and PM_(10) concentrations between31 Chinese cities and their relationships with SO_2,NO_2,CO and O_3

The variations of mass concentrations of PM_(2.5),PM_(10),SO_2,NO_2,CO,and O_3 in 31 Chinese provincial capital cities were analyzed based on data from 286 monitoring sites obtained between March 22,2013 and March 31,2014.By comparing the pollutant concentrations over this length of time,the characteristics of the monthly variations of mass concentrations of air pollutants were determined.We used the Pearson correlation coefficient to establish the relationship between PM_(2.5),PM_(10),and the gas pollutants.The results revealed significant differences in the concentration levels of air pollutants and in the variations between the different cities.The Pearson correlation coefficients between PMs and NO_2 and SO_2 were either high or moderate(PM_(2.5) with NO_2:r=0.256-0.688,mean r=0.498;PM_(10) with NO_2:r = 0.169-0.713,mean r = 0.493;PM2.5 with SO_2:r= 0.232-0.693,mean r=0.449;PM_(10) with SO_2:r = 0.131-0.669,mean r=0.403).The correlation between PMs and CO was diverse(PM_(2.5):r = 0.156-0.721,mean r=0.437;PM_(10):r=0.06-0.67,mean r= 0.380).The correlation between PMs and O_3 was either weak or uncorrelated(PM_(2.5):r--0.35 to 0.089,mean r=-0.164;PM_(10):r=-0.279 to 0.078,mean r=-0.127),except in Haikou(PM2.5:r=0.500;PM_(10):r-0.509).     

Particulate pollution in an underground car park in Wuhan,China

Particulate matter (PM) pollution in an underground car park in Wuhan was investigated. Mass concentrations of PM₁₀ and PM_2.5 were obtained using gravimetric method. Selected metal elements, such as Fe, Mn, Zn, Pb, and Cu in PM₁₀ samples, were determined using atomic absorption spectrometer (AAS). Beta attenuation method was applied to observe the hourly variation of PM₁₀ levels. Results show that average PM₁₀ concentrations at the entrance and at the exit were 101.3 μg/m³ and 234.4 μg/m³, respectively, and average PM_2.5 concentrations at the entrance and at the exit were 47.7 μg/m³ and 62.7 μg/m³, respectively. PM pollution was worse at the exit than at the entrance. Hourly PM₁₀ concentration was weakly correlated with traffic flow. Regarding element concentrations, the most enriched element in PM₁₀ samples was Fe. Re-suspension of soil dust at the exit is an important source of PM₁₀.     

乙醚云雾场燃爆参数实验研究

基于自行研发的20 L二次脉冲气动喷雾多相爆炸测试系统和全散射粒径测量系统,对乙醚液体燃料瞬态雾化云雾场的燃爆参数进行实验研究。通过调节气动压力、设计喷雾剂量,得到了粒径相同、质量浓度不同的乙醚云雾燃爆超压、温度及点火延迟时间等燃爆参数。结果表明,在索特平均直径为22.90 μm的条件下:乙醚云雾与空气混合物的燃爆下限为80.26 g/m3,燃爆上限为417.34 g/m3;最大超压峰值为0.78 MPa,其出现在云雾质量浓度为278.23 g/m3时;最大爆温峰值为1 260 ℃,其出现在云雾质量浓度为228.29 g/m3时;点火延迟时间在燃爆极限范围内呈U型分布。     

Light attenuation cross-section of black carbon in an urban atmosphere in northern China

Fine particulate matter (PM_2.5) samples were collected over two years in Xi’an, China to investigate the relationships between the aerosol composition and the light absorption efficiency of black carbon (BC). Real-time light attenuation of BC at 880 nm was measured with an aethalometer. The mass concentrations and elemental carbon (EC) contents of PM_2.5 were obtained, and light attenuation cross-sections (σ_ATN) of PM_2.5 BC were derived. The mass of EC contributed ∼5% to PM_2.5 on average. BC σ_ATN exhibited pronounced seasonal variability with values averaging 18.6, 24.2, 16.4, and 26.0 m²/g for the spring, summer, autumn, and winter, respectively, while averaging 23.0 m²/g overall. σ_ATN varied inversely with the ratios of EC/PM_2.5, EC/[SO₄²⁻], and EC/[NO₃⁻]. This study of the variability in σ_ATN illustrates the complexity of the interactions among the aerosol constituents in northern China and documents certain effects of the high EC, dust, sulfate and nitrate loadings on light attenuation.     

Characteristics of elemental carbon and organic carbon in PM10 during spring and autumn in Chongqing, China

PM10 （particulate matter with aerodynamic diameter less than 10 μm） samples were collected simultaneously at nine urban sites and one urban background site during two intensive observation campaigns in 2006. Concentrations of elemental carbon （EC） and organic carbon （OC） in PM10 were analyzed using an element analyzer. The characteristics regarding spatial and seasonal distribution patterns of OC and EC concentrations and their contributions to PM10 mass, as well as correlation between OC and EC, were investigated in detail. The average OC and EC concentrations for urban sites were 57.5 ± 20.8 and 8.3 ± 3.9 μg/m^3, respectively, both being around three times higher than those for urban background site. As a whole, EC concentrations did not show distinct seasonal variations, though OC concentrations were generally higher in autumn than in spring. For urban sites, total carbonaceous aerosol （TCA） accounted for 33.2% in spring and 35.0% in autumn of PM10 mass. The OC and EC concentrations were found significantly correlated to each other both in spring and in autumn, implying the existence of similar emission sources such as coal combustion. The OC/EC ratios generally exceeded 2.0, indicating the presence of secondary organic carbon （SOC）, whose estimated concentration for urban Chongqing was 26.7 and 39.4μg/m^3, accounting for 48.9 and 61.9% of the total OC observed in the samples, in spring and in autumn, respectively.     

Transport of black carbon aerosols from non-local sources: A case study in Shanghai

Black carbon (BC) aerosol mass carried by winds of varying directions from non-local sources was estimated based on hourly measured data of BC mass concentration (C_BC) and meteorological parameters from January 2008 to December 2012 in Shanghai, and the relationship between annual average C_BC and wind speed was analyzed. The results show that the annual average C_BC decreased with wind speed for speeds exceeding 0.3 m/s. The relationship between the two was determined by a linear fit with correlation coefficient 0.88. Assuming BC aerosol mass of non-local sources transported by a southeast wind was zero, annual average BC concentrations (μg/m³) carried by winds of variable direction were 1.99 (southwest), 1.95 (west), 1.15 (northwest), 0.54 (south), 0.39 (north), 0.01 (northeast), and 0.01 (east). BC aerosol mass of non-local sources transported by wind to Shanghai was about 6404.05 t per year, among which the total contribution of southwest, west, and northwest winds was nearly 84%. The aerosol mass transported to Shanghai in winter accounted for 35% that of the entire year, and was greater than that of the other seasons.     

Characteristics of black carbon aerosol in Jiaxing,China during autumn 2013

We conducted measurements of black carbon (BC) aerosol in Jiaxing, China during autumn from September 26 to November 30, 2013. We investigated temporal and diurnal variations of BC, and its correlations with meteorological parameters and other major pollutants. Results showed that hourly mass concentrations of BC ranged from 0.2 to 22.0 μg/m³, with an average of 5.1 μg/m³. The diurnal variation of BC exhibited a bimodal distribution, with peaks at 07:00 and 18:00. The morning peak was larger than the evening peak. The mass percentages of BC in PM_2.5 and PM₁₀ were 7.1% and 4.8%, respectively. The absorption coefficient of BC was calculated to be 44.4 Mm⁻¹, which accounted for 11.1% of the total aerosol extinction. BC was mainly emitted from local sources in southwestern Jiaxing where BC concentrations were generally greater than 11 μg/m³ during the measurement period. Correlation analysis indicated that the main sources of BC were motor vehicle exhaust, and domestic and industrial combustion.     

Mass and isotopic concentrations of water-insoluble refractory carbon in total suspended particulates at Mt. Waliguan Observatory (China)

Mass concentration and isotopic values δ¹³C and ¹⁴C are presented for the water-insoluble refractory carbon (WIRC) component of total suspended particulates (TSP), collected weekly during 2003, as well as from October 2005 to May 2006 at the WMO-GAW Mt. Waliguan (WLG) site. The overall average WIRC mass concentration was (1183 ± 120) ng/m³ (n = 79), while seasonal averages were 2081 ± 1707 (spring), 454 ± 205 (summer), 650 ± 411 (autumn), and 1019 ± 703 (winter) ng/m³. Seasonal variations in WIRC mass concentrations were consistent with black carbon measurements from an aethalometer, although WIRC concentrations were typically higher, especially in winter and spring. The δ¹³C PDB value (−25.3 ± 0.8)‰ determined for WIRC suggests that its sources are C₃ biomass or fossil fuel combustion. No seasonal change in δ¹³C PDB was evident. The average percent Modern Carbon (pMC) for ¹⁴C in WIRC for winter and spring was (67.2 ± 7.7)% (n = 29). Lower pMC values were associated with air masses transported from the area east of WLG, while higher pMC values were associated with air masses from the Tibetan Plateau, southwest of WLG. Elevated pMC values with abnormally high mass concentrations of TSP and WIRC were measured during a dust storm event.     

液体工质电热化学发射实验研究

介绍了小口径电热发射装置采用液体（含能或不含能）工质的电热发射实验结果及对结果的分析。对工质的种类、质量和装填方式，等离子体的破膜压力，电能与化学能匹配关系，弹重等参量进行了初步优化。结果表明，采用不含能工质可将０．５ｇ弹丸加速到１７８３ｍ／ｓ，采用含能工质可将０．５ｇ弹丸加速到２１６０ｍ／ｓ，０．３ｇ弹丸加速到２２００ｍ／ｓ以上。测得的压力曲线表明，在电能与化学能释放速率互补的条件下，可以得到明显的压力平台效应。     

PM2.5 in China： Measurements,sources, visibility and health effects,and mitigation

Concern over the health effects of fine particles in the ambient environment led the U.S. Environmental Protection Agency to develop the first standard for PM2.5 （particulate matter less than 2.5 μm） in 1997. The Particle Technology Laboratory at the University of Minnesota has helped to establish the PM2.5 standard by developing many instruments and samplers to perform atmospheric measurements. In this paper, we review various aspects of PM2.5, including its measurement, source apportionment, visibility and health effects, and mitigation. We focus on PM2.s studies in China and where appropriate, compare them with those obtained in the U.S. Based on accurate PM2.5 sampling, chemical analysis, and source apportionment models, the major PM2.5 sources in China have been identified to be coal combustion, motor vehicle emissions, and industrial sources. Atmospheric visibility has been found to correlate well with PM2.s concentration. Sulfate, ammonium, and nitrate carried by PM2.s, commonly found in coal burning and vehicle emissions, are the dominant contributors to regional haze in China. Short-term exposure to PM2.s is strongly associated with the increased risk of morbidity and mortality from cardiovascular and respiratory diseases in China. The strategy for PMzs mitigation must be based on reducing the pollutants from the two primary sources of coal-fired power plants and vehicle emissions. Although conventional Particulate Emission Control Devices （PECD） such as electrostatic precipitators in Chinese coal-fired power plants are generally effective for large particles, most of them may not have high collection efficiency of PM2.5. Baghouse filtration is gradually incorporated into the PECD to increase the PM2.5 collection efficiency. By adopting stringent vehicle emissions standard such as Euro 5 and 6, the emissions from vehicles can be gradually reduced over the years. An integrative approach, from collaboration among academia, government, and industries, can effectively manage and mitigate the PM2.s p     

PM2.5 in an industrial district of Zhengzhou,China: Chemical composition and source apportionment

Zhengzhou is a developing city in China, that is heavily polluted by high levels of particulate matter. In this study, fine particulate matter (PM_2.5) was collected and analyzed for their chemical composition (soluble ions, elements, elemental carbon (EC) and organic carbon (OC)) in an industrial district of Zhengzhou in 2010. The average concentrations of PM_2.5 were 181, 122, 186 and 211 μg/m³ for spring, summer, autumn and winter, respectively, with an annual average of 175 μg/m³, far exceeding the PM_2.5 regulation of USA National Air Quality Standards (15 μg/m³). The dominant components of PM_2.5 in Zhengzhou were secondary ions (sulphate and nitrate) and carbon fractions. Soluble ions, total carbon and elements contributed 41%, 13% and 3% of PM_2.5 mass, respectively. Soil dust, secondary aerosol and coal combustion, each contributing about 26%, 24% and 23% of total PM_2.5 mass, were the major sources of PM_2.5, according to the result of positive matrix factorization analysis. A mixed source of biomass burning, oil combustion and incineration contributed 13% of PM_2.5. Fine particulate matter arising from vehicles and industry contributed about 10% and 4% of PM_2.5, respectively.     

CHARACTERIZATION AND ADSORPTION PROPERTIES OF POROUS CARBON NANOFIBER GRANULES

The properties of the porous granules produced by agglomeration of catalytically grown carbon nanofibers were investigated in this work. The single pellet crushing strength of the granules is high, e.g., 1.6-2.5 MPa. They have high specific surface areas, averaging 72-141 m^2·g^-1, and the majority of their pores are mesopores or macropores. The adsorption at 298 K of benzene or phenol on the granules is much lower than that on activated carbon and depends not only on the specific surface area of the carbon material but also on the sewing structure of the granules and the morphology of the carbon nanofibers. Treatment in dilute nitric acid appreciably reduces such adsorption.     

SOURCE PROFILES AND FINGERPRINTS OF FINE AND COARSE SANDS RESUSPENDED FROM SOILS SAMPLED IN CENTRAL INNER MONGOLIA

Fingerprints and source profiles of fine and coarse sands that originate from Central Inner Mongolia during Asian continental sandstorms （ACS） can be used to identify the odgin of Asian sands and to trace them as they travel downwind. Soil samples collected at various land surfaces in Central Inner Mongolia were resuspended using a dry powder atomizer in an enclosure chamber. The resuspended sands were then sampled by two dichotomous samplers situated at the bottom of the enclosure chamber for fine （PM2 5） and coarse （PM2.5-10） sands, respectively. The chemical composition of sands, including water-soluble ionic species, metallic contents, and carbonaceous contents, were further analyzed. Results from resuspension tests indicated that the soils contained considerably more coarse particles than fine Moreover, Mg, K, Al, and Fe in coarse sand had strong correlations with each other. The ratio of Mg, K. Fe （or Al） to Al （or Fe） and OC/EC in the coarse sands can be used as the fingerprints of Asian sands originating from Central Inner Mongolia.     

Characteristics of organic and elemental carbon in atmospheric fine particles in Tianjin, China

PM2.5 samples were collected at urban, industrial and coastal sites in Tianjin during winter, spring and summer in 2007. Concentrations of elemental carbon （EC） and organic carbon （OC） were analyzed using the IMPROVE thermal-optical reflectance （TOR） method. Both OC and EC exhibited a clear seasonal pattern with higher concentrations observed in the winter than in the spring and summer, due to cooperative effect of changes in emission rates and seasonal meteorology. The concentrations of carbonaceous species were also influenced by the local factors at different sampling sites, ranking in the order of industrial〉 urban 〉 coastal during winter and spring. In the summer, the port emissions, enriched with EC, had a significant impact on carbonaceous aerosols at the coastal site. Total carbonaceous aerosol accounted for 40.0% in winter, 33.8% in spring and 31.4% in summer of PM2.5 mass. Good correlation （R = 0.84-0.93） between OC and EC indicated that they had common dominant sources of combustion such as coal burning and traffic emissions. The daily average OC/EC ratios ranged from 2.1 to 9.1, the elevated OC/EC ratios being found in the winter. The estimated secondary organic carbon （SOC） accounted for 46.9%, 35.3% and 40.2% of the total OC in the winter, spring and summer, respectively, indicating that SOC may be an important contributor to fine organic aerosol in Tianjin.     

Chemically modified magnetic chitosan microspheres for Cr(VI) removal from acidic aqueous solution

A bioadsorbent composed of magnetic silica nanoparticles encapsulated by chitosan microspheres was prepared by the emulsion cross-linking method, and it was then modified with quaternary ammonium groups by reaction with ethylenediamine and glycidyl trimethylammonium chloride. Characterization of the bioadsorbent indicated that it was highly acid resistant and magnetically responsive. The bioadsorbent was then used to remove Cr(VI) from acidic aqueous solution. The results of batch experiments indicated that the optimal pH value was 2.5, and the adsorbent exhibited low pH dependence. The maximum adsorption capacity was 233.1 mg/g at pH 2.5 and 25 °C, and the equilibrium time was determined to be 40–120 min depending on the initial Cr(VI) concentration. The adsorbent could be effectively regenerated using a mixture of 0.3 mol/L NaOH and 0.3 mol/L NaCl with a desorption efficiency of 95.6%, indicating high reusability. In conclusion, the bioadsorbent shows potential for Cr(VI) removal from acidic wastewater.     

Emission of organic carbon,elemental carbon and water-soluble ions from crop straw burning under flaming and smoldering conditions

Emissions from major agricultural residues were measured using a self-designed combustion system. Emission factors (EFs) of organic carbon (OC), elemental carbon (EC), and water-soluble ions (WSIs) (K⁺, NH₄⁺, Na⁺, Mg²⁺, Ca²⁺, Cl⁻, NO₃⁻, SO₄^2–) in smoke from wheat and rice straw were measured under flaming and smoldering conditions. The OC₁/TC (total carbon) was highest (45.8% flaming, 57.7% smoldering) among carbon fractions. The mean EFs for OC (EF_OC) and EC (EF_EC) were 9.2 ± 3.9 and 2.2 ± 0.7 g/kg for wheat straw and 6.4 ± 1.9 and 1.1 ± 0.3 g/kg for rice straw under flaming conditions, while they were 40.8 ± 5.6 and 5.8 ± 1.0 g/kg and 37.6 ± 6.3 and 5.0 ± 1.4 g/kg under smoldering conditions, respectively. Higher EC ratios were observed in particulate matter (PM) mass under flaming conditions. The OC and EC for the two combustion patterns were significantly correlated (p < 0.01, R = 0.95 for wheat straw; p < 0.01, R = 0.97 for rice straw), and a higher positive correlation between OC₃ and EC was observed under both combustion conditions. WSIs emitted from flaming smoke were dominated by Cl⁻ and K⁺, which contributed 3.4% and 2.4% of the PM mass for rice straw and 2.2% and 1.0% for wheat straw, respectively. The EFs of Cl⁻ and K⁺ were 0.73 ± 0.16 and 0.51 ± 0.14 g/kg for wheat straw and 0.25 ± 0.15 and 0.12 ± 0.05 g/kg for rice straw under flaming conditions, while they were 0.42 ± 0.28 and 0.12 ± 0.06 g/kg and 0.30 ± 0.27 and 0.05 ± 0.03 g/kg under smoldering conditions, respectively. Na⁺, Mg²⁺, and NH₄⁺ were vital components in PM, comprising from 0.8% (smoldering) to 3.1% (flaming) of the mass. Strong correlations of Cl⁻ with K⁺, NH₄⁺, and Na⁺ ions were observed in rice straw and the calculated diagnostic ratios of OC/EC, K⁺/Na⁺ and Cl⁻/Na⁺ could be useful to distinguishing crop straw burning from other sources of atmospheric pollution.     

开口阻塞比对粉体抑制甲烷爆炸的影响研究

为了研究开口阻塞比φ对粉体抑爆特性的影响，采用质量浓度C为0、80、160、240 g/m3的Al (OH)₃和NaHCO₃粉体，分别抑制具有不同φ（0、0.2、0.4、0.6、0.7、1.0）值的5 L管道内甲烷/空气预混气爆炸。实验结果表明:火焰的破碎度随粉体抑爆效率的增大而增大；最大超压峰值p_max、爆燃指数K_st由燃烧速率和泄爆速率共同决定。φ=0.7是每条爆炸特征参数曲线的拐点。随着φ值增加，超压峰值下降率δ先增大后减小，在0.4和0.6之间达到最大；总体上，Al (OH)₃和NaHCO₃两种粉体的抑爆效率相近。但在某些阻塞比下，阻塞比引起的低湍流影响着粉体颗粒的沉降行为，使得Al (OH)₃抑爆效率优于NaHCO₃。当粉体质量浓度从80 g/m3增加到240 g/m3时，热阻增加，火焰的热量不能扩散到粒子云的中心，不利于内部粒子的吸热分解，致使浓度效应越来越弱。