灰霾期间大气颗粒物污染特征研究进展

近年来,随着经济的迅速发展和城市化进程的加快,灰霾天气呈现增加的趋势,引起了社会的高度关注。综述了灰霾发生时大气颗粒物污染水平、粒径分布和垂直分布特征,大气颗粒物重要化学成分(水溶性离子、有机碳和元素碳、金属元素)的浓度水平和粒径分布特征及大气颗粒物的来源解析方法,并提出灰霾主要防治措施。     

广州大气颗粒物与酸沉降的关系研究

本文研究了大气颗粒物的酸度和酸缓冲能力,实验证实广州大气颗粒物中存在着游离的硫酸,其水溶性离子中SO4^2-及NO3^-占很大的比例。颗粒物中的碱性成分含量大于酸性成分,对酸性降水有一定的缓冲能力。气溶胶中细颗粒物的酸性大于粗颗粒物,且酸缓冲能力远低于粗颗粒物。     

上海吴淞地区气溶胶粒径分布和元素浓度研究

为了有效降低颗粒物浓度和提高吴淞工业区大气环境质量,重要的任务是测定大气颗粒物的粒径分布和化学组分.本研究使用DYLEC-120型冲击式9级采样仪,选择该地区有代表性的4个采样点,在冬季(2004年1月)采集不同粒径大气颗粒物(分别为》11,11～7,7～4.7,4.7～3.3,3.3～2.1,2.1～1.1,1.1～0.65,0.65～0.43,《0.43μm).使用质子激发X荧光发射技术测定不同粒径颗粒物中S,K,Ca,Ti,Cr,Mn,Fe,Ni,Cu,Zn,Br和Pfb 12种无机元素浓度.结果发现,吴淞工业区气溶胶质量浓度呈现双峰分布,峰值分别位于1.1～2.1和4.7～7.0 μm两个粒径范围.富集因子分析结果表明,4个监测点无机元素浓度和污染状况与监测点所在地及周边工矿企业排放紧密相关.应当引起重视的是S,Cr,Ni,Cu,Zn,Br和Pb等元素已严重地受到人为污染源的影响,而且这些元素更趋于富集在直径小于2.1 μm的细颗粒物中,呈现粒径变小而污染加剧的特征.     

大气有害颗粒物室内自然沉降实验研究

大气有害颗粒物(PM)对人体有极大的危害,紧闭门窗可使颗粒物自沉降,从而实现空气洁净。为研究室内有害颗粒物自然沉降的净化效果,该研究采用激光离散式颗粒物传感器与数据采集系统,对自然条件下室内大气有害颗粒物自然沉降进行实验研究。通过实验发现:室内大气有害颗粒物在重度污染(粒径小于2.5μm的PM150μg/m~3)浓度下,有较明显的自然沉降速率,PM粒径2.5μm～10μm、1.0μm～2.5μm、0.3μm～1.0μm自然沉降速率分别为:1.76μg/(m~3·min)、0.67μg/(m~3·min)和0.51μg/(m~3·min),当颗粒物为中度与轻度污染浓度时(150μg/m~3),自然沉降速率随浓度降低逐渐放缓;当密闭室内存在人员时,会加快室内大气有害颗粒物下降速率;此外,不同粒径的大气有害颗粒在空气中的分布均匀状态不同,粒径越大在空气中分布越不均匀,粒径越小越均匀,其在空气中自然沉降的速率越低。     

北京市大气颗粒物中多环芳烃的分布特征

用撞击式分级采样器同步采集了北京市城乡结合部、郊区的2003年4个季节的不同粒径大气颗粒物样品，用气相色谱-质谱分析了其中的多环芳烃，并对两个地区大气颗粒物中的多环片烃含量、分布及季节性变化特征进行了探讨。     

高氯准东煤中典型矿物元素对颗粒物生成的影响

在高温沉降炉上,进行了高氯高碱准东煤、低氯低碱准东煤和由低氯准东煤处理制得的调质准东煤在含不同浓度HCl的模拟空气中的燃烧实验。利用DLPI进行了颗粒物的分级收集,对其质量粒径分布和矿物元素分布特性进行了讨论分析。结果表明,高氯高碱准东煤的超细模态颗粒物生成量和峰值粒径均明显大于其他两种煤,其主要成分为Na和Cl。Ca的迁移特性与其形态密切相关,原煤中的Ca主要以无机矿物形式存在,主要迁移进入粗颗粒物而对超细颗粒物生成贡献较小。气氛中加入不同浓度HCl气体后,低钠煤和调质煤产生细颗粒物中Cl含量均升高,但生成量无显著变化。表明HCl并未显著促进矿物的气化,但会促进NaCl形式矿物蒸气的形成,进而促进成核形成超细颗粒物。     

空气中可吸入颗粒物检测方法比较

大气颗粒物浓度是大气污染监测中的一项重要指标,大气中的颗粒物特别是PM10及其以下颗粒物浓度的监测一直是国内外专家关注的问题。分析了常用大气颗粒物浓度的检测方法,对各类检测方法的优缺点作了对比。     

空气中可吸入颗粒物检测方法比较

大气颗粒物浓度是大气污染监测中的一项重要指标,大气中的颗粒物特别是PM 10及其以下颗粒物浓度的监测一直是国内外专家关注的问题。分析了常用大气颗粒物浓度的检测方法,对各类检测方法的优缺点作了对比。     

上海大气纳米颗粒物粒径分布研究

为了更深入地研究上海大气气溶胶微小颗粒物的物理和化学特性,采用MSP公司生产的WPSTM Model1000XP宽范围粒径谱仪测量粒径介于10～10000 nm的气溶胶纳米颗粒物,探讨粒径在10～500 nm间的气溶胶纳米颗粒物随时间、高度和地区变化的时空分布特征.结果表明,总质量浓度随时间的变化比总粒子数浓度的变化滞后,纳米颗粒物总粒子数浓度和质量浓度随高度增加呈指数衰减.纳米颗粒物总粒子数浓度和质量浓度在工业区和商业区较高而在生活区和郊区较低.超细颗粒对粒子数浓度贡献较大而细颗粒对粒子质量浓度贡献较大.     

微波消解-原子荧光法测定颗粒物中砷、硒、铋、锑的不确定度评定

大气颗粒物的成分复杂，性状多样，容易受到各种环境因素的影响，通过分析大气颗粒物中重金属含量及变化，对评价城市环境空气污染状况及污染物的来源具有重要的意义。采用滤膜收集环境空气中的总悬浮颗粒物，利用微波消解-原子荧光法分析环境空气样品中As、Se、Bi、Sb元素，对其不确定度进行了评估，主要包括标准溶液配置、标准曲线拟合、重复测定样品、样品采集过程中4个不确定度分析，为类似的不确定度评定提供了参考依据。     

Influence of Calcareous Sorbents on Particulate Emissions from Fluidized Bed Combustion of Lignite

The composition and morphology of coarse and fine fly ashes from atmospheric fluidized bed combustion of 2 lignites without additives or with hydrated lime and limestone as sorbents for sulfur dioxide removal were investigated. The ashes were separated and size segregated by cyclone and low pressure BLPI impactor. The properties of both coarse (sizes >10 θm) and fine (sizes < 10 θm) particles were investigated using INAA, PIXE, and SEM. The application of sorbents increased the emissions of coarse particles, but reduced the emissions of fine particles. The increase was caused by additional carry over of particles of additives; the decrease of emission of fine particles probably resulted from the combined increase of scavenging of fine particles by particles of sorbents and reduction of their formation due to reduced concentrations of sulfur dioxide in flue gas. Most of the trace elements investigated in this study showed substantial enrichment in fine particles. However, due to simultaneous reduction of concentration of fine particles the emissions of most trace elements decreased.     

Author Index to Volume 38

X-ray photoelectron spectroscopy (XPS) is a powerful technique for determining the surface chemical composition of atmospheric particles. In this article, we employed XPS to study atmospheric particles collected from Guangzhou city in typical sites and seasons. The results showed that the weight percentage of carbon, oxygen, nitrogen, and sulfur were about 70.5–87.1%, and these species dominated the surface structure of the particles independent of the collection site and season. Inorganic elements including Si, Na, Ca, Cl, Fe, K, Al, and Cu were also found on the particle surfaces. The high-resolution XPS spectra revealed: (1) High aromatic and aliphatic C-H, and other oxidized carbons were found on the surface of particles. (2) The nitrogen species were characterized by pyridinic, pyrrolic/amide, quaternary type nitrogen functionalities, and nitrate groups, indicating that inorganic and organic N species are both important components of N-containing particles. (3) Sulfate and sulfone groups were also present on the surface and were important components. The oxidized groups of C, N, and S were higher in winter samples, consistent with the monsoon weather of Guangzhou in winter, which is favorable for the formation of oxidized species. A comparison between total and surface analyses showed that the surface of particles was relatively high in organic carbon, NO₃ ^?, and SO₄ ^2?, and the interior of particles was higher in NH₄ ⁺. These results provide information on the formation of aerosols, e.g., NH₄ ⁺ may act as a very important nucleus and organic carbon, NO₃ ^?, and SO₄ ^2? coat the nuclei during particle growth.     

Individual Particle Morphology and Acidity

The morphological characterization of particles during the Pittsburgh Air Quality Study (PAQS) suggests that particle shape and physical state depends on their acidity. The aerosol shape parameters measured by Computer-Controlled Scanning Electron Microscopy (CCSEM) are statistically different in periods when atmospheric particles are neutral and when they are acidic. High concentrations of particles smaller than 500 nm with high sulfur content and liquid appearance or signs of a previous liquid state before partial or total recrystallization are present on filters collected in days with high aerosol acidity. By contrast, in winter and summer periods in which the aerosol was neutral, the shape parameter values are similar and suggest that the particles have been dried out. These direct observations support the hypothesis that during summer acidic periods in the Eastern United States the particles may contain some water even at low relative humidity both in the atmosphere and on filters.     

钙基脱硫剂用于冶炼烟气脱硫的模拟与实验

提出了一种应用钙基脱硫剂脱除冶炼烟道气中高浓度SO₂并回收硫单质的方法。通过热力学模拟多种硫化物与SO₂之间的反应,筛选得出硫化钙（CaS）适合作为化学链脱硫技术的脱硫剂,它在400～650℃范围内可将SO₂还原为单质硫,生成的固相产物为CaSO₄而非CaO。通过固定床反应器内的脱硫实验,发现温度对脱硫率和硫单质回收率影响较大。在400～650℃范围内温度越高,脱硫率和硫单质回收率越大;当温度高于600℃时,脱硫率和硫单质回收率基本相等。提高空速,则会降低脱硫率和硫单质回收率,但两者的差值随空速增大逐渐减小。当烟气中SO₂浓度小于1%时,脱硫率维持在99.8%基本不变;SO₂浓度升至3.45%后,平均脱硫率急剧下降至92.1%;SO₂浓度越高,平均脱硫率越低。硫单质回收率随SO₂浓度增大存在一最佳范围。在脱硫反应后期,粒径较大的脱硫剂颗粒脱硫性能较低。SEM照片表明了脱硫剂颗粒随反应温度的升高团聚现象更为明显,XRD表征证明了反应中SO₂气体被还原为升华硫颗粒。     

淤浆反应器中SO_2的催化氧化

研究了常温常压下淤浆反应器中SO_2催化氧化反应,通过改变反应物的进口浓度和测定小颗粒床层平均氧化反应速率(此时传质阻力最小),间接验证了假定的反应机理:氧在活性炭活性位上的吸附为速率控制步骤,本征反应速率相对于颗粒表面的溶氧浓度为一级,而与此浓度范围内的SO_2浓度无关,通过改变催化剂的用量、粒径及反应温度,测定了各模型参数.     

1—苯基—5—巯基四氮唑和苯并三氮唑在胶态银和硫化银上的阳极抑制效应

为了研究抑制剂对银核和硫化银核的不同作用，本工作考察了1－苯基－5－巯基四氮唑（PMT）和苯并三氮唑（BTA)作为抑制剂在银核和硫化银核上物理显影的阳极抑制和解抑制效应。实验结果表明：1）PMT和BTA对Ag核和银离子过量时制得的硫化银核，Ag2S(Ag)，的显影催化活性都有不同程度的抑制作用，而对硫离子过量时制得的硫化银核，Ag2S(S)，无明显的抑制作用，这可能是由于过量硫离子在硫化银核上的吸附要强于这两种抑制剂；2）S2O3^2-或I^-离子的存在对BTA在Ag核上有解抑制作用，不仅可恢复甚至提高Ag核的显影催化活性，而对Ag2S核的抑制作用无明显影响；3）与BTA不同，S2O3^2-或I^-离子对PMT在Ag核上没有解抑制作用，对Ag2S(Ag)核的抑制作用还稍有增强，而对Ag2S(S)核稍有减弱；4）银溶胶中的表面增强拉曼谱（SERS）测量证实：BTA在Ag核上的吸附导致Ag核显影催化活性的下降，加入S2O3^2-或I^-离子后致使BTA的SERS信号消失则意味着BTA在银核表面的脱附。以上这些结果说明阳极抑制机理在抑制效应中有重要作用。     

微生物培养液脱H2S及副产物的性质

以氧化亚铁硫杆菌培养液和酸性Fe2（SO4）3溶液为吸收剂，采用优化的工艺条件进行了H2S的脱除实验，并对微生物培养液脱H2S后的副产物硫磺的相关性质进行了测定分析，以期为工业应用中硫磺回收工艺的设计提供参考。实验结果表明：采用微生物培养液脱H2S比单纯使用酸性Fe2（SO4）3溶液的效果好，反应进行45 min后，脱硫率仍可保持在90%以上；微生物培养液脱H2S后的副产物硫磺颗粒不溶于水，微溶于乙醇，完全溶于二硫化碳和四氯化碳，密度为1. 90 g·cm-3，熔点为121℃；该颗粒为不规则球形，在溶液中极易发生团聚现象，加入分散剂后测得平均粒径为5. 09 μm；该副产物硫磺具有亲水性，在工业应用上优于具有疏水性的升华硫和酸性Fe2（SO4）3溶液脱H2S产生的硫；该副产物硫颗粒在溶液中的沉降速度为0. 125×10-2 m·s-1。     

Urea particle coating for controlled release by using DCPD modified sulfur

The shell of sulfur coated urea was easily cracked due to sulfur being friable. Sulfur was modified with dicyclopentadiene (DCPD) to increase its strength and abrasion resistance. SEM images showed that the micro-structure of modified sulfur was denser and more uniform than pure sulfur. The strength of modified sulfur increased with the DCPD/S ratio. Experiments of urea particle coating with sulfur and modified sulfur were carried out in a fluidized bed coater. The shell of coated urea particles with modified sulfur was more compact than that with pure sulfur. The modification retarded the sulfur phase transformation from monoclinic to orthorhombic, avoiding the crack formation in the coating shell of sulfur. The modified sulfur coated urea particles can be produced with thinner shell and higher strength, and had better controlled release properties.     

Catalytic oxidative desulfurization of benzothiophene with hydrogen peroxide over Fe/AC in a biphasic model diesel-acetonitrile system

Catalytic oxidative desulfurization (Cat-ODS) of benzothiophene (BT) in n-octane has been investigated with hydrogen peroxide (H₂O₂) over catalysts of activated carbon (AC) supported iron oxide under mild conditions. The catalyst was characterized by N₂ adsorption, XRD, SEM/EDS, TPR and XPS. Under the best operating condition for the catalytic oxidative desulfurization—temperature 60 °C, atmospheric pressure, 0.15 g Fe/AC, 18 molar ratio of hydrogen peroxide to sulfur, using acetonitrile as extraction solvent for double extraction—the sulfur content in model diesel fuel (MDF) was reduced from 700 ppmw to 30 ppmw with 95.66% of total sulfur was removed.     

The effects of different manufacturing techniques on the availability of sulfate to pasture from mixtures of elemental sulfur with either triple superphosphate or partially acidulated reactive phosphate rock

Six different preparations of elemental sulfur incorporated into triple superphosphate and a single mixture of elemental sulfur with partially acidulated reactive phosphate rock were evaluated for the rate of release of sulfatesulfur to pasture at two sites.The method of preparing the mixtures affected the size of sulfur particles released on dispersion of fertilizer granules. The rates of release of sulfate from oxidation of the elemental sulfur was controlled by the fineness of the particles of elemental sulfur. For rapid release of sulfate by oxidation a mixture prepared by sintering elemental sulfur with mature triple superphosphate was the most effective. It contained sulfur particles of diameter less than 75 m. The mixtures which comprised synthetic blends of elemental sulfur of particle size less than 150 m or 150–250 m, each with mature triple superphosphate, released sulfate at a progressively slower rate than that with particles less than 75 m. However, both proved effective sulfur fertilizers releasing sulfate over a 1–2 year period. In contrast, mixtures prepared by adding molten elemental sulfur during the process of manufacturing triple superphosphate resulted in a coarser distribution of sulfur particles and a slow release of sulfate to plants.The incorporation of sulfur into a mixture with partially acidulated reactive phosphate rock was made via the dispersion of molten sulfur into phosphoric acid which was then used to partially acidulate phosphate rock. The resultant sulfur particles ranged from finely divided (e.g. 38% < 150 m) to moderately fine (81% < 500 m), and the release of sulfate was predictable based on the particle size distribution.Differences between the two experimental sites in uptake of plant sulphate reflected the different pastures grown. At the cool temperate coastal site a ryegrass/clover pasture rapidly took up sulfate as it was released into the topsoil. Inland, in the summer-dry environment, the uptake of released sulfate by the deep-rooted lucerne pasture was delayed for 12–18 months, indicating that the sulfate uptake increased after the nutrient had leached beyond the surface soil layer.