武汉市某区域大气颗粒物的测定与分析

采用电感耦合等离子体原子发射光谱法对TSP环境样品和尘源样品中的S、Si、Ti、Al、As、Ca、Pb、V等30余个元素组份进行分析并计算出各元素的含量,得到本区域大气环境TSP和污染尘源元素特征谱,并通过比较微波消解与加热消解两种方法的优劣,确定出较适应消解方法.结果表明,该区域中的A区污染源主要来自道路交通尘源和土壤尘源,B区污染源来自土壤尘源和建筑尘源.     

贵阳市PM2.5主要污染源源成分谱分析

为建立贵阳市PM_(2.5)主要污染源的源成分谱,将主要污染源划分为土壤风沙尘、城市扬尘、道路尘、建筑水泥尘、钢铁尘、燃煤尘和汽车尾气尘7类,分别采集各类污染源样品,然后进行再悬浮采样,并采用电感耦合等离子体质谱仪、离子色谱仪及热光碳分析仪分别分析样品中20种无机元素、3种水溶性离子和碳组分的质量分数。结果表明,7类污染源成分谱之间存在明显的区别,其中土壤风沙尘、建筑水泥尘、钢铁尘、汽车尾气尘、燃煤尘5类污染源谱都有明显的标识元素,分别为Si、Ca、Fe、OC、EC和Se,而道路尘和城市扬尘属混合尘源,无单一标识元素,道路尘显示出土壤风沙尘、建筑水泥尘、燃煤尘、机动车尾气和工业排放的混合污染特征,城市扬尘则主要受土壤风沙尘和建筑水泥尘的影响。     

桂林市开放扬尘源源谱构建及化学组成特征研究

为了揭示桂林市大气中开放源组分特征,本研究在桂林采集了土壤扬尘、道路扬尘、建筑扬尘、堆场扬尘样品,分析了多种无机元素和水溶性离子含量,构建了桂林市开放源源谱。结果表明:桂林市土壤扬尘、道路扬尘、建筑扬尘、堆场扬尘中主量成分主要包含Ca、Fe、Al,主要为地壳元素和建筑标志元素。所有开放扬尘源元素中Ca,道路扬尘中Cu、Zn,堆场扬尘Pb、Zn富集程度极强,这些元素受人为污染影响,主要来自建筑施工、机动车、燃煤等。桂林市开放扬尘源之间分歧系数大于0.2,各开放扬尘源之间化学组成相似度不高;建筑扬尘与道路扬尘、土壤扬尘之间的分歧系数相对较小(分别为0.37、0.39),相互影响较大。桂林市各开放扬尘源与上海市扬尘源之间的分歧系数高(分别为0.46、0.50、0.51),化学组分差异大,可能与两个城市主要产业、人为污染源的差异相关。     

基于铅同位素解析技术的土壤铅污染来源研究

通过分析耕层土壤铅污染的程度,分析耕层土壤铅污染的来源,解析各污染源对土壤铅污染的相对贡献率.以陕西某工业区为研究区域,采集大气降尘、耕层土壤(0 ～ 20 cm)和背景土壤样品,用ICP-MS测定铅元素质量比及同位素比率(206pb/207 pb和208pb/206pb),分析耕层土壤铅污染的来源,结合二元混合模型计算各污染源对耕层土壤铅的贡献率.结果表明,耕层土壤铅质量比范围为21.8 ～ 40.0mg/kg,平均值为27.1 mg/kg;背景土壤铅质量比范围为19.1 ～22.1mg/kg,平均值为21.4 mg/kg;大气降尘铅质量比范围为570.2 ～2 221.7 mg/kg,平均值为1 062.36 mg/kg.该区域铅锌冶炼活动对耕层土壤铅的贡献率约为18.43％,焦化厂燃煤对耕层土壤铅的贡献率约为9.36％,热电厂燃煤对耕层土壤铅的贡献率约为19.71％,背景土壤对耕层土壤的贡献率约为52.5％.背景土壤是耕层土壤铅污染的主要来源.     

唐山市PM2.5理化特征及来源解析

为了研究唐山市PM2.5理化特征及来源,分别于2012年7月和2013年1月对唐山市夏、冬季PM2.5样品进行了采集,应用电感耦合等离子体质谱仪(ICP-MS)、离子色谱仪(IC)和DRI碳质分析仪对PM2.5样品中化学组分元素、水溶性离子及有机碳和元素碳(OC/EC)进行了分析。应用CAMx-PSAT数值模型对采样时段PM2.5进行模拟,分析了夏、冬季PM2.5的主要来源。结果表明,唐山市PM2.5污染严重,夏、冬季质量浓度分别为国家环境II级标准的1.08倍和2.49倍。夏季PM2.5中二次组分质量浓度较高,占PM2.5总质量浓度的53.56%。SO2-4、NO-3和NH+4是PM2.5中重要的二次组分,占PM2.5质量浓度的31.49%~43.79%。一次组分中,矿物尘和POA占PM2.5质量浓度比例最高。唐山夏冬季节PM2.5未知组分比例分别为14.4%和24.86%。工业源是唐山市PM2.5污染的主要来源,夏、冬季节贡献率分别为74.1%和43.8%。由于居民燃煤采暖,冬季居民源对唐山市PM2.5贡献率增大。冬季唐山市主导风向为西北,外来源对PM2.5贡献率为31.2%;夏季主导风向为东南,外来源贡献率为15.0%。气象因素是导致外来源贡献季节变化的重要原因。     

电炉除尘技术的现状和展望

(一)电炉生产过程中产生的烟尘,是冶金工厂主要污染源之一。电炉烟尘主要成分是金属氧化物。在电炉冶炼过程中,熔化期粉尘粒度小于10微米的占80%,吹氧时粉尘粒度小于0.1微米的占90%。氧化期烟气温度高达1200～1400℃,烟气含尘浓度高达20g/m~3,粉尘比电阻为10~(12)—10~(13)Ω·cm。上述条件虽然给电炉烟尘治理带来一定的难度,     

长江口围填海土壤中PBDEs的浓度、组成及来源解析

选取上海市崇明岛为采样区域,研究1974—2010年5个年代的由长江泥沙冲刷淤积而成的长江口围填海土壤中PBDEs的质量比分布、组成特征,并对其进行来源解析。于2012年10月在选取的5个年代区域分别采用五点梅花网格布点法采集表层(0~15 cm)和深层(100 cm)土壤,样品经索氏提取和层析净化处理后,采用GC-MS定量定性方法检测。结果表明,12种PBDEs目标化合物全部被检出,表层和深层土壤中∑12PBDEs质量比范围分别为8.008~27.783 ng/g、7.032~12.506 ng/g,主要是低溴代PBDEs。此外,其污染水平随年代呈现不断上升的趋势。最后基于因子分析法解析其来源,围填海土壤样品中最主要的污染源是PBDE-17、47、66和28;而且结合土壤污染质量比及组分特征分析得到,表层土壤与下一年代的围填海深层土壤的污染水平和来源基本一致。     

基于BP模型的土壤重金属对其生物毒性的贡献分析

通过BP神经网络模型对石油开采区土壤重金属的部分缺失试验数据进行补齐,并采用主成分分析法对石油开采区土壤中重金属进行源解析。结果表明,土壤中重金属的来源包括自然来源、农业来源、交通来源和燃煤来源。以不同来源重金属作为输入条件、土壤生物毒性作为输出条件构建不同来源重金属土壤发光菌生物毒性神经网络模型,模型验证结果表明,在0.05显著性水平下,25组验证样本模拟值和试验值之间的相关系数r为0.396,满足模型验证要求。结合相对灵敏度计算,获得不同来源重金属对土壤生物毒性的贡献率分别为自然来源26.68%、农业来源52.71%、交通来源4.67%、燃煤来源15.94%,即农业来源为石油开采区土壤中发光菌生物毒性的最主要来源。     

区域污染对北京市采暖期SO2污染的影响分析

结合调查统计的2002年北京市及周边地区污染源排放资料,以GIS地理信息系统作为污染源数据库的可视化载体,利用美国EPA最新发展的区域空气质量模式Models-3/CMAQ,对2002年1月北京市SO2区域污染情况进行模拟,并在此基础上,研究区域污染对北京市采暖期SO2污染的影响.对比模拟结果和同期地面监测资料发现,两者具有较好的相关性,模式较好地反映了2002年1月北京市SO2污染的变化趋势.周边影响结果显示,2002年1月周边污染对北京市SO2月平均贡献率为9.8%,日均浓度超标(大于150 μg/m3)天数内周边贡献平均为11.0%.采暖期北京SO2浓度周边地区贡献较少,主要来源于北京本地污染源.周边省市对北京SO2的月平均贡献率存在季节差异,分别为春22.3%、夏12.9%、秋17.2%、冬9.8%.但就总体而言,周边省市对北京市SO2浓度的贡献率普遍较低,这是因为SO2在大气中的生命周期较短,在长距离传输及扩散过程中不断发生化学转化,并通过干、湿沉降过程不断被清除.但考虑到周边省市SO2排放可能造成气溶胶粒子以及酸雨等二次污染问题,对北京市空气质量存在潜在危害,因此对外地源也应给予一定重视.     

济南市东泺河底泥及其雨水汇水区地表灰尘中重金属的污染特征研究

以济南市东泺河为研究对象,采集了13个底泥样品和30个雨水汇水区地表灰尘样品,测定了Cd、Cr、Cu、Zn、Pb、As 6种重金属的质量比。分析了底泥与地表灰尘重金属的污染状况和空间分布特征,并通过统计分析对底泥与地表灰尘重金属的相关性和来源进行探讨。结果表明,底泥与地表灰尘样品中Cd、Cr、Cu、Zn、Pb质量比均不同程度地高于小清河沿岸土壤重金属背景值;采暖期与非采暖期地表灰尘重金属质量比有明显差异。底泥重金属质量比由南向北逐渐增高,北园大街以北Cu、Zn、Cd处于偏中污染水平;地表灰尘重金属质量比从大到小依次为小企业聚集区、商贸区、居住小区、混合区,且小企业聚集区、商贸区重金属综合生态风险达到中等水平。除Pb与Cr、As外,底泥重金属各元素之间相关性较强,地表灰尘重金属Cu、Zn、Cd 3种元素两两显著相关,底泥与地表灰尘重金属Cr存在极显著相关(p0.01)。源解析结果表明,人为影响对底泥和地表灰尘重金属的贡献最大,底泥重金属的人为混合源和交通源贡献率分别占79.6%和10.9%,地表灰尘重金属的人为混合源和建筑源贡献率分别占43.2%和22.9%。     

Effect of particle morphology on metal dust deflagration sensitivity and severity

Combustible dust explosions continue to present a significant threat toward industries processing, storing, or pneumatically conveying metal dust hazards. Through recent years, investigations have observed the influence of particle size, polydispersity, and chemical composition on dust explosion sensitivity and severity. However, studies characterizing the effect of particle shape (or morphology) on metal dust explosibility are limited and merit further consideration. In this work, high-purity aluminum dust samples of three unique particle morphologies were examined (spherical granular, irregular granular, and dry flake). To maintain consistency in results obtained, all samples were procured with similar particle size distribution and polydispersity, as verified by laser diffraction particle size analysis. Scanning electron microscopy (SEM) imaging and Brunauer-Emmett-Teller (BET) experiments were executed to confirm supplier claims on morphology and to quantify the effective surface area associated with each sample, respectively. Investigations performed in a Kühner MIKE3 minimum ignition energy apparatus and a Siwek 20 L sphere combustion chamber resulted in the direct characterization of explosion sensitivity and severity, respectively, as a function of suspended fuel concentration and variable particle morphology. Recommendations to standard risk/hazard analysis procedures and to existing design guidance for the mitigation of deflagrations that originate from ignition of distinctively processed metal dust fuels have been provided.     

管式电除尘器"伞形罩"结构特性研究

在高温、高湿窑炉烟气条件下,采用立式管式电除尘器“伞形罩”结构,能够解决其清灰不力、二次扬尘、除尘效率不稳定等问题。本研究了“伞形罩”结构的除尘机理及效率及清灰力度影响因素、抑制二次扬尘机制。研究结果表明,“伞形罩”结构除尘效率因集尘表面积的增加而提高;应用支铁框架式振打方式,振打强度明显加强;其分流机制能有效地抑制二次扬尘：从而为“伞形罩”结构的优化设计提供了依据。     

对喷流除尘技术在收集硫酸铵和硝酸铵粉尘中的应用研究

对喷流除尘技术利用粉尘颗粒在撞击区内来回振荡、相互碰撞并团聚的机理进行除尘.实验采用水平式对喷流除尘系统收集硫酸铵和硝酸铵的混合物粉尘,主要考察喷嘴气流速度、含尘浓度和喷雾化水润湿含尘气流对除尘效率的影响,并进行机理分析.实验表明,除尘效率随喷嘴风速的增大而升高,但喷嘴风速超过25～27 m/s后,反而下降;除尘效率随含尘浓度的增加而升高,但含尘浓度超过0 45～0.55 kg/m3后反而有所降低;喷雾化润湿含尘气流能显著提高除尘效率,最优耗水量为0.18～0.22 kg/kg粉尘,超过该值后无显著变化.实验确定的最优除尘条件为:喷嘴速度25～27 m/s、含尘浓度0.45～0.55 kg/m3、耗水量0.18～0 22 kg/kg粉尘,除尘效率最高可达96.8%.     

Scaling of dust explosion violence from laboratory scale to full industrial scale – A challenging case history from the past

The standardized K_St parameter still seems to be widely used as a universal criterion for ranking explosion violence to be expected from various dusts in given industrial situations. However, this may not be a generally valid approach. In the case of dust explosion venting, the maximum pressure P_max generated in a given vented industrial enclosure is not only influenced by inherent dust parameters (dust chemistry including moisture, and sizes and shapes of individual dust particles). Process-related parameters (degree of dust dispersion, cloud turbulence, and dust concentration) also play key roles. This view seems to be confirmed by some results from a series of large scale vented dust explosion experiments in a 500 m³ silo conducted in Norway by CMI, (now GexCon AS) during 1980–1982. Therefore, these results have been brought forward again in the present paper. The original purpose of the 500 m³ silo experiments was to obtain correlations between P_max in the vented silo and the vent area in the silo top surface, for two different dusts, viz. a wheat grain dust collected in a Norwegian grain import silo facility, and a soya meal used for production of fish farming food. Both dusts were tested in the standard 20-L-sphere in two independent laboratories, and also in the Hartmann bomb in two independent laboratories. P_max and (dP/dt)_max were significantly lower for the soya meal than for the wheat grain dust in all laboratory tests. Because the available amount of wheat grain dust was much larger than the quite limited amount of available soya meal, a complete series of 16 vented silo experiments was first performed with the wheat grain dust, starting with the largest vent area and ending with the smallest one. Then, to avoid unnecessary laborious changes of vent areas, the first experiment with soya dust was performed with the smallest area. The dust cloud in the silo was produced in exactly the same way as with the wheat grain dust. However, contrary to expectations based on the laboratory-scale tests, the soya meal exploded more violently in the large silo than the wheat grain dust, and the silo was blown apart in the very first experiment with this material. The probable reason is that the two dusts responded differently to the dust cloud formation process in the silo on the one hand and in the laboratory-scale apparatuses on the other. This re-confirms that a differentiated philosophy for design of dust explosion vents is indeed needed. Appropriate attention must be paid to the influence of the actual dust cloud generation process on the required vent area. The location and type of the ignition source also play important roles. It may seem that tailored design has to become the future solution for tackling this complex reality, not least for large storage silos. It is the view of the present author that the ongoing development of CFD-based computer codes offers the most promising line of attack. This also applies to design of systems for dust explosion isolation and suppression.     

Does your facility have a dust problem: Methods for evaluating dust explosion hazards

The hazards of dust explosions prevailing in plants are dependent on a large variety of factors that include process parameters, such as pressure, temperature and flow characteristics, as well as equipment properties, such as geometry layout, the presence of moving elements, dust explosion characteristics and mitigating measures. A good dust explosion risk assessment is a thorough method involving the identification of all hazards, their probability of occurrence and the severity of potential consequences. The consequences of dust explosions are described as consequences for personnel and equipment, taking into account consequences of both primary and secondary events.While certain standards cover all the basic elements of explosion prevention and protection, systematic risk assessments and area classifications are obligatory in Europe, as required by EU ATEX and Seveso II directives. In the United States, NFPA 654 requires that the design of the fire and explosion safety provisions shall be based on a process hazard analysis of the facility, process, and the associated fire or explosion hazards. In this paper, we will demonstrate how applying such techniques as SCRAM (short-cut risk analysis method) can help identify potentially hazardous conditions and provide valuable assistance in reducing high-risk areas. The likelihood of a dust explosion is based on the ignition probability and the probability of flammable dust clouds arising. While all possible ignition sources are reviewed, the most important ones include open flames, mechanical sparks, hot surfaces, electric equipment, smoldering combustion (self-ignition) and electrostatic sparks and discharges. The probability of dust clouds arising is closely related to both process and dust dispersion properties.Factors determining the consequences of dust explosions include how frequently personnel are present, the equipment strength, implemented consequence-reducing measures and housekeeping, as risk assessment techniques demonstrate the importance of good housekeeping especially due to the enormous consequences of secondary dust explosions (despite their relatively low probability). The ignitibility and explosibility of the potential dust clouds also play a crucial role in determining the overall risk.Classes describe both the likelihood of dust explosions and their consequences, ranging from low probabilities and limited local damage, to high probability of occurrence and catastrophic damage. Acceptance criteria are determined based on the likelihood and consequence of the events. The risk assessment techniques also allow for choosing adequate risk reducing measures: both preventive and protective. Techniques for mitigating identified explosions risks include the following: bursting disks and quenching tubes, explosion suppression systems, explosion isolating systems, inerting techniques and temperature control. Advanced CFD tools (DESC) can be used to not only assess dust explosion hazards, but also provide valuable insight into protective measures, including suppression and venting.     

湿式纤维栅振动除尘机理与效率的研究

本提出了湿式振动纤维栅除尘机制的理论模型。在风流作用下，纤维振动所产生的水膜增加了湿式振动纤维栅水的活性表面积(称为二次造膜机制)，是提高除尘效率的重要因素。提出了单层湿式振动纤维栅除尘效率的计算式；并从理论上解释了“过滤风速越大，除尘效率越高”这一现象的原因。     

敞开式TBM施工隧道粉尘扩散及除尘系统研究

TBM掘进过程中产生大量粉尘，为了掌握粉尘的分布规律并优化除尘系统，以敞开式TBM为例，采用数值计算方法研究不同除尘风管位置，不同除尘风速和不同掘进面产尘量下的洞内粉尘浓度分布规律。研究结果表明:敞开式TBM隧道施工过程中，掘进面至除尘风管区域质量粉尘浓度较高，在除尘风管口后方区域下降到 2 mg/m3以下；除尘风管布置在距掘进面30 m位置处时，洞内沿程粉尘含量相对较大，除尘风管布置在距掘进面20 m位置处时洞内沿程及TBM支护区域粉尘含量相对较小；排风风速为15 m/s时，敞开式TBM支护区域粉尘质量浓度最小，排风风速为30 m/s时，该区域粉尘质量浓度最大；掘进面产尘量越大，洞内沿程及敞开式TBM支护区域粉尘质量浓度越大，不同产尘量下洞内粉尘浓度均在除尘风管后方达到规范限值以下。     

城市植物叶面尘粒径和几种重金属(Cu、Zn、Cr、Cd、Pb、Ni)的分布特征

为研究城市植物叶面尘粒径及重金属元素(Cu、Zn、Cr、Cd、Pb、Ni)的分布规律和污染特征,以西安市不同功能区大叶女贞(Ligus-trum lucidum)和小叶女贞(Ligustrum quihoui)叶面尘为研究对象,用激光粒度分析仪测定叶面尘的粒径分布,用原子吸收分光光度计测定叶面尘重金属质量比,并探讨了叶面尘重金属的可能来源。结果表明,大叶女贞和小叶女贞叶面尘粒径小于50μm。前者叶面尘粒径累积曲线呈双峰分布,平均粒径和粒径峰值从大到小为相对清洁区、工业区、居住文教区、交通枢纽区、商业区;后者呈单峰分布,平均粒径和粒径峰值由大到小为工业区、居住文教区、交通枢纽区、商业区和相对清洁区。不同功能区叶面尘中Cu、Zn、Cr、Cd、Pb、Ni有明显的富集,其质量比分别为(325.5±72.6)mg/kg、(3 965.6±1 112.9)mg/kg、(349.2±149.3)mg/kg、(35.3±6.8)mg/kg、(1 182.0±355.1)mg/kg、(324.1±129.5)mg/kg,为陕西省土壤背景值的7.9～20.8、29.7～77.9、2.6～11.1、262.8～489.4、26.4～71.8和6.9～18.9倍。不同功能区2物种叶面尘各重金属质量比差异显著(p<0.001),物种间差异不显著(p>0.05)。叶面尘中Zn、Pb、Ni、Cr的质量比以工业区最高,Cu、Cd以交通枢纽区最高,其次为商业区,居住文教区和相对清洁区负荷最低。研究认为,叶面降尘中的重金属可能来自外源输入。     

散煤运输用膜型抑尘剂的制备及性能研究

采用水溶液聚合法,以氧化淀粉、丙烯酸(AA)、二甲基二烯丙基氯化铵(DMDAAC)为原料,通过接枝共聚制备了一种软膜型抑尘剂(抑尘剂液体干燥后形成具有一定韧性的软膜)。与聚乙烯醇类壳型抑尘剂(干燥后形成很脆的壳层)相比,软膜型抑尘剂提高了煤粉固化层的抗破裂能力。由抗震荡性试验可知,使用膜型抑尘剂后,经过18 h的震荡,煤粉的损失率仅为1.91%,而使用壳型抑尘剂后煤粉的损失率为4.85%。还测定了2种抑尘剂的保湿性和耐破度。利用红外光谱对产物的结构进行了表征,采用SEM观察了该产物在煤粉表面形成的膜层形貌。试验结果表明,散煤运输中膜型抑尘剂在减少煤粉损失和控制扬尘污染方面性能优于壳型抑尘剂。     

一种测定建筑物外墙表面黏附粉尘的方法

提出了一种测定建筑物外墙表面黏附粉尘的方法.该方法具体步骤包括1)选择建筑物外墙面污染有代表性的部位,确定建筑外墙的粉尘采样面积,通常取0 1～0 5 m2; 2)用玻璃烧杯量取适量蒸馏水,作为从外墙面采得粉尘的载体,通常一次测定使用的蒸馏水为0 1～0 5 L; 3)用干净小刷子或布片将圈定面积的外墙表面打湿,将粉尘搽洗到蒸馏水中; 4)将含有悬浮粉尘的蒸馏水用超声波振动分散,适宜时间和温度分别为2～5 min和20～35 ℃;5)测定单位面积墙面黏附粉尘质量,通过激光粒度分析仪测定溶液的粉尘浓度和分散度(如果粉尘浓度较大,可制作粉尘涂片,在显微分析系统上测定粉尘的粒径分散度).含尘溶液产生泡沫时会影响测定效果,因此测定粉尘浓度前需先加消泡剂消泡.该测定与评价方法对评价建筑物表面粉尘的污染程度和清洁剂效果等具有重要意义.