Diurnal variation of number concentration and size distribution of ultrafine particles in the urban atmosphere of Beijing in winter

Number concentration and distribution of airborne particles in the size range 5.6 to 560 um diameter were measured in Beijing for a 15-d period in winter 2005.Daily average number concentrations of nucleation mode(5.6-20 nm),Aitken mode(20-100 nm), and accumulation mode(100-560 nm)particles,and total particles were 17500,32000,4000,and 53500 cm~(-3),respectively.Average particle size distribution was monomodal with a mode diameter of about 40 um at night and bimodal with mode diameters of about 10 and about 40 nm during the daytime.New particle formation events,which were connected to diurnal variation of nucleation mode particles,were observed in more than half of the observation days.The events often started around 10:00-11:00 Chinese Standard Time (CST)and ended up after 3-4 h.Concentrations of Aitken and accumulation mode particles increased from midnight and reached their maxima at about 10:00 CST,and then decreased and became the lowest in the afternoon.Analysis of diurnal cycles in traffic volume and meteorological parameters revealed that the accumulation of the particles in Aitken and accumulation modes in the morning was influenced by formation of an inversion and increase in vehicle emission,and dispersion of such particles in the afternoon was associated with more effective vertical mixing and higher wind speed.     

南京冬夏硫酸盐和硝酸盐对黑碳混合态的影响

采用单颗粒黑碳光度计（SP2）结合MARGA在线分析仪对南京地区冬季和夏季黑碳（BC）的质量浓度,以及硫酸盐,硝酸盐对其混合状态的影响进行了研究.结果表明,冬季和夏季南京地区BC质量浓度分别在1.01~14.5μg/m³和0.20~3.81μg/m³之间,均值分别为（4.39±2.66）μg/m³和（1.67±0.76）μg/m³,均呈现早晚高值的双峰型日变化特征.运用相对包裹层厚度D_p/D_c表示BC混合状态,冬季和夏季D_p/D_c分别在1.39~2.34和1.03~1.45之间,均值分别（1.81±0.21）和（1.24±0.08）,D_p/D_c日变化特征与BC相反,冬季D_p/D_c日变化幅度较大.冬季D_p/D_c与SO₄^2-和NO₃^-的相关性较好,D_p/D_c与NO₃^-的相关性高于其与SO₄^2-的相关性,夏季则相反.冬季清洁时期BC以本地源排放为主,其混合状态受硫酸盐和硝酸盐影响较高,冬季重污染时期,受排放源以及区域传输的影响,D_p/D_c与SO₄^2-和NO₃^-的相关性较低.     

TOF–SIMS surface analysis of chemical components of size–fractioned urban aerosols in a typical heavy air pollution event in Beijing

Size–fractioned atmospheric aerosol particles were collected during a typical heavy air pollution event in Beijing. The organic and inorganic components on the surfaces of the samples were analyzed using time–of–flight secondary ion mass spectrometry(TOF–SIMS).The variation characteristics of the surface chemical composition and influencing factors were studied, and the possible sources of these chemical compositions were identified through principal component analysis. The results showed that inorganic components such as crustal elements and sulfate, and organic components such as aliphatic hydrocarbons and oxygen–containing organic groups were present. Some surface components, such as polycyclic aromatic hydrocarbons, heavy metals and fluorides may exert adverse effects on human health. The species and relative percentages of the chemical components varied with particle size, diurnal and pollution progress. During a heavy pollution event, the species and relative percentages of secondary components such as oxygen–containing organic groups and sulfurous compounds increased, indicating that particles aged during this event. The surface chemical composition of the aerosol particles was affected mainly by emissions from coal combustion and motor vehicles. In addition, air pollution, meteorological factors, and air mass transport also exerted a significant effect on the surface chemical composition of aerosol particles.     

Chemical characterization of fine and ultrafine PM, direct and indirect genotoxicity of PM and their organic extracts on pulmonary cells

Particulate matter in ambient air constitutes a complex mixture of fine and ultrafine particles composed of various chemical compounds including metals, ions, and organics. A multidisciplinary approach was developed by studying physico-chemical characteristics and mechanisms involved in the toxicity of particulate atmospheric pollution. PM_(0.3–2.5) and PM_(2.5) including ultrafine particles were sampled in Dunkerque, a French industrialized seaside city. PM samples were characterized from a chemical and toxicological point of view. Physicochemical characterization evidenced that PM_(2.5) comes from several sources: natural ones, such as soil resuspension and marine sea-salt emissions, as well as anthropogenic ones, such as shipping traffic, road traffic, and industrial activities. Human BEAS-2 B lung cells were exposed to PM_(0.3–2.5), or to the Extractable Organic Matter(EOM) of PM_(0.3–2.5) and PM_(2.5). These exposures induced several mechanisms of action implied in the genotoxicity, such as oxidative DNA adducts and DNA Damage Response. The toxicity of PM-EOM was higher for the sample including the ultrafine fraction(PM_(2.5)) containing also higher concentrations of polycyclic aromatic hydrocarbons. These results evidenced the major role of organic compounds in the toxicity of PM.     

稀土纳米抗菌材料卫生安全性的研究初探

稀土纳米材料集稀土特性和纳米特性于一体 ,大大提高了纳米材料的抗菌和空气净化效果 ,因此 ,稀土纳米材料及其应用已成为当前的一个热点 ,但其卫生安全性还未引起人们的足够重视。因此 ,笔者概要地介绍了纳米抗菌材料的基本性质 ;回顾了国内外纳米抗菌材料卫生安全性的研究现状 ;并进行了初步的动物红细胞脆性试验。试验结果发现豚鼠接触该类稀土纳米材料后 ,红细胞的脆性与对照组相比降低明显 ,提示过量的使用稀土纳米材料会对机体产生不良的影响。笔者最终提出了可能存在的作用机理 ,即纳米材料粒径很小 (0 .1～ 10 0 .0nm) ,具有独特的小尺寸效应和表面效应 ,极大的比表面积使得纳米材料吸附能力很强。稀土离子以纳米级的金属氧化物作为载体 ,更易被绑定并穿过细胞膜 ,从而对红细胞的脆性造成了很强的破坏 ,故脆性值较正常对照组显著增加。     

Agglomeration rate and action forces between atomized particles of agglomerator and inhaled-particles from coal combustion

In order to remove efficiently haled-particles emissions from coal combustions, a new way was used to put forward the process of agglomeration and the atomization was produced by the nozzle and then sprayed into the flue before precipitation devices of power station boiler in order to make inhaled-particles agglomerate into bigger particles, which can be easily removed but not change existing running conditions of boiler. According to this idea, a model is set up to study agglomeration rate and effect forces between fly ash inhaledparticles and atomized agglomerator particles. The developed agglomeration rate was expressed by relative particle number decreasing speed per unit volume. The result showed that viscosity force and flow resistance force give main influences on agglomeration effect of inhaledparticles, while springiness force and gravity have little effect on agglomeration effect of theirs. Factors influencing the agglomeration rate and effect forces are studied, including agglomerator concentration, agglomerator flux and agglomerator density, atomized-particles diameters and inhaled-particles diameter and so on.     

非均相活化剂磁性纳米CoFe2O4的制备及其活性评价

采用溶胶-凝胶法制备了磁性纳米铁酸钴（CoFe₂O₄）固体颗粒，并采用扫描电镜（SEM），X射线衍射仪（XRD），傅里叶变换红外光谱仪（FT-IR）和振动样品磁强计对样品进行表征分析.以磁性纳米CoFe₂O₄颗粒活化过硫酸盐氧化去除水中四环素为探针反应，评价CoFe₂O₄颗粒的活化性能.结果表明，600℃焙烧温度下制备出的固体颗粒，其活性较高，颗粒表面金属离子浸出率较低；优化温度下制备的CoFe₂O₄颗粒在较宽的pH值范围（4.4~9.0）内均具有较高活性；控制实验条件PDS₀ 1g/L，CoFe₂O₄ 1g/L，TCH₀ 50mg/L，20℃，pH₀ 4.4，反应4h后TCH去除率达到82.0%.CoFe₂O₄颗粒循环重复利用10次后仍保持较高的活性和结构稳定性，而且因其特殊的磁性能便于回收利用.     

Variations in surface functional groups, carbon chemical state and graphitization degree during thermal deactivation of diesel soot particles

The thermal deactivation of diesel soot particles exerts a significant influence on the control strategy for the regeneration of diesel particulate filters (DPFs). This work focused on the changes in the surface functional groups, carbon chemical state, and graphitization degree during thermal treatment in an inert gas environment at intermediate temperatures of 600°C, 800°C, and 1000°C and explore the chemical species that were desorbed from the diesel soot surface during thermal treatment using a thermogravimetric analyser coupled with a gas-chromatograph mass spectrometer (TGA-GC/MS). The surface functional groups and carbon chemical state were characterized using Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The graphitization degree was evaluated by means of Raman spectroscopy (RS). The concentrations of aliphatic C–H, C–OH, C=O, and O–C=O groups are reduced for diesel soot and carbon black when increasing the thermal treatment temperature, while the sp²/sp³ hybridized ratio and graphitization degree enhance. These results provide comprehensive evidence of the decreased reactivity of soot samples. Among oxygenated functional groups, the percentage reduction during thermal treatment is the largest for the O–C=O groups owing to its worst thermodynamic stability. TGA-GC/MS results show that the aliphatic and aromatic chains and oxygenated species would be desorbed from the soot surface during 1000°C thermal treatment of diesel soot.     

大气细粒子中阴离子表面有机活性物质分析方法的优化

为优化大气细粒子中阴离子表面有机活性物质的亚甲蓝分光光度法和乙基紫分光光度分析法,分别从样品前处理和分析测定两方面对分析方法进行优化,并采用2种优化方案对北京市大气细粒子样品进行分析测定. 结果表明:①2种优化方案的最佳超声提取频率、最佳初始水浴温度和最佳超声提取时间均分别为40 Hz、30 ℃和35 min;②亚甲蓝优化方案的最佳显色剂使用量为0.70 mg,其中中性亚甲蓝和酸性亚甲蓝使用量均为0.35 mg,最佳静置时间为30~45 min;③乙基紫优化方案的最佳显色剂使用量为0.098 mg,最佳静置时间为30 min,最佳辅助性试剂使用量分别为pH＝5的醋酸盐缓冲液0.4 mL,乙二胺四乙酸二钠10 μmol,硫酸钠0.25 mmol. 采用2个优化方案测得的北京市大气细粒子样品中ρ(MBAS)(MBAS为亚甲蓝活性物质)和ρ(EVAS)(EVAS为乙基紫活性物质)分别为0.14～0.39和0.14～0.47 μg/m3. 与亚甲蓝优化方案相比,乙基紫优化方案的试验操作更简便、标准曲线线性关系更好,更适合大气细粒子中阴离子表面有机活性物质的测定.      

纳米TiO2粉尘的采集与控制试验研究

利用硫酸-硫酸铵混合溶液作为吸收及消解液,开发了直接吸收、消解、显色分析纳米TiO2生产现场空气中的纳米TiO2粉尘的方法。并研究了各类口罩对于纳米TiO2的拦截效率。结果表明,在流速为400L/h,采集时间为2.5 h的情况下,采用两级吸收瓶形式,总采集效率可以达到94%以上。对纳米TiO2生产现场粉尘的控制研究表明,佩戴无纺布型口罩是非常有效的防护手段,单只口罩2.5 h平均截留效率大于86%,两只口罩2.5 h平均截留效率大于90%。根据口罩的拦截效果,参照NIOSH的推荐标准,建议将纳米TiO2生产现场的粉尘质量浓度定为小于1.0mg/m3。