原油与柴油泄露影响海洋飞沫气溶胶中重金属与多环芳烃分布的实验室模拟研究

海洋泄漏原油中的重金属和多环芳烃等污染物会因为破碎波进入到海洋飞沫气溶胶中,造成更大范围的环境生态风险,而目前其具体机制和影响因素尚未充分探究。本研究以从长庆油田、新疆油田和渤海油田采集的原油以及中国石化的成品油为研究对象,设计了一套模拟产生海洋飞沫气溶胶的实验室装置,模拟了海洋表面浪花裹挟原油后再释放到大气的过程,并进行海洋飞沫气溶胶的粒径分布、多环芳烃和重金属的浓度及富集因子(EF)分析。研究发现,轻质油中的部分低分子量多环芳烃更易于从覆油海面迁移到海洋飞沫气溶胶中并发生富集(EF≥10);尽管油品本底值中的重金属浓度很低,但无论是柴油泄漏还是原油泄漏,重金属均会富集到在海洋飞沫气溶胶中,且浓度水平与多环芳烃相差较小,在300~1800μg/m^(3);油膜厚度对海洋飞沫气溶胶中的重金属有十分显著的影响,随着油膜厚度的降低,海洋飞沫气溶胶中的重金属呈现“减少增多减少”的变化趋势。

海洋飞沫气溶胶的实验模拟

作为大气气溶胶的重要组成,海洋飞沫气溶胶(sea spray aerosol,SSA)在全球气候变化中发挥着重要作用.SSA的产生过程同时受到海洋和大气环境的共同作用,其理化性质和全球通量存在显著的区域性差异,进而导致目前SSA对全球环境和气候变化的贡献评估存在较大不确定性.为了认识SSA的形成过程以及不同环境要素对其产生的影响机制,目前已经展开了大量的研究工作,特别是在实验室受控条件下模拟SSA产生方面获得了丰富的研究成果.本文聚焦SSA实验室模拟研究,重点围绕SSA的产生、化学组成、物质转移以及其对不同环境因素响应方面的研究进展进行了系统总结,并展望了该领域未来的重点研究方向.

会议室内飞沫气溶胶分布特征的数值模拟

目的分析会议室内不同气流组织对人持续说话产生的飞沫气溶胶运动轨迹的影响,模拟飞沫气溶胶在会议室内的分布特征,确定最佳的气流组织方式.方法采用CFD数值模拟方法,选择RNG k-ε湍流模型计算空调房间的温度场和速度场,分析飞沫气溶胶颗粒的受力情况,采用拉格朗日法建立飞沫气溶胶颗粒运动的数学模型,模拟空调房间会议室内同侧上送上回、同侧上送下回、对侧上送下回3种混合通风和置换通风对飞沫气溶胶的运动轨迹.结果飞沫气溶胶运动轨迹显示飞沫气溶胶在置换通风停留时间和运动距离最短.3种混合通风气流组织相比,同侧上送上回的气流组织中飞沫气溶胶运动时间112 s和运动路程11.1 m最短,同侧上送下回次之,对侧上送下回最长.结论 3种混合通风中,同侧上送上回更容易避免飞沫气溶胶在室内传播,是最佳的混合通风气流组织方式.置换通风相比于混合通风更易减小人员之间受感染的可能性,是最佳的气流组织方式.

飞沫气溶胶污染源特性研究现状

综述了近年来关于飞沫气溶胶污染源特性的实验研究。给出了飞沫气溶胶污染物被以如打喷嚏、咳嗽、说话和呼吸等不同方式射入室内时的速度与流量、角度与开口面积、温度、粒径分布与浓度等特性参数。分析了特性参数的影响因素,为研究气溶胶污染物在室内的传播提供参考依据。指出了目前污染源特性实验研究存在的不足。

白浪法在南海飞沫气溶胶通量计算中的应用和修正

白浪覆盖率法（白浪法）是被广泛应用的计算气溶胶粒子通量的方法,但是公式本身还存在一些问题,且其在低纬度海域的应用情况还未见报道。本文利用2012年8月25日—10月12日在中国南海走航实验观测的气溶胶粒子浓度数据,对Monahan等的白浪覆盖率-风速的公式进行了修正,并利用最小二乘法推导出单位白浪面积上次微米气溶胶产生通量与风速的关系。对半径小于0.3μm的粒子,通量的分布符合对数正态分布,通量的对数与风速呈幂函数关系。与高纬度海域的研究相比,中国南海飞沫气溶胶粒子的排放通量特征表现为较小粒子（r80〈0.2μm）较其他海域偏高,而较大粒子略偏低。当风速在7~13m·s-1时,用新的源函数计算的通量与观测值保持较高的一致性。

会议室人体飞沫气溶胶颗粒运动规律的数值分析

采用Lagrange方法建立描述气溶胶颗粒运动的离散相数学模型,通过CFD数值模拟方法,对会议室内人说话产生的飞沫气溶胶颗粒污染物的运动规律进行分析。数值模拟结果发现:当送风量保持不变时,减小送风口面积、增大送风速度,可以加速飞沫气溶胶颗粒排出房间,更容易避免飞沫气溶胶的传播,减少人员之间的交叉感染。

造纸用乳液聚合除气去沫剂的性能研究

造纸行业各工序都不同程度存在料浆中夹带的空气对造纸各工段造成许多不利影响。特别是洗浆、抄纸及污水处理等工段夹带的空气产生的泡沫更是难以除去,严重影响了各生产企业的正常生产,甚至造成严重的质量、环境事故。目前国内市售消泡剂由于乳化油滴大效果不理想,在碱性条件下的消泡抑泡效率低,在高温条件下漂油。我们针对这些情况运用纳米技术和乳液聚合的新工艺成功研制了乳液聚合型有机硅除气去沫剂(RXP系列)。该除气去沫剂是传统消泡剂的升级换代产品,在中间体制备过程加入纳米粒子提高中间体的活性,采用乳液聚合的方法得到特殊粒径的乳液微粒,乳液微粒的粒径更均匀,能有效减少物料中夹带的空气。

飞沫气溶胶颗粒狭窄空间扩散仿真模拟比较研究

通过将计算流体力学理论和仿真模拟技术运用于飞沫气溶胶可以在狭窄空间扩散仿真模拟,构建了游轮狭窄通道、陆上酒店通道这两个具有代表性、典型性的仿真模型,建立了以总释放率、断流强度、入口速度等为主要技术参数,以流动进出口、壁面边界等因素为边界条件,以成年病毒携带者打喷嚏为场景的离散格式三维模拟运算,研究计算出游轮狭窄通道内飞沫扩散距离最远可达6m,是岸上酒店通道的3倍的结果,分析提出游轮飞沫扩散风险较高的结论。

自然通风电梯内咳嗽飞沫扩散模拟研究

针对自然通风电梯轿厢内的空气流场,以及轿厢内的咳嗽飞沫气溶胶扩散过程进行数值模拟研究。结果表明,不论电梯轿厢上下行工况,空气均从顶部风口流入轿厢,由底部风口流出;咳嗽液滴进入轿厢后,液滴群迅速根据粒径分层,直径大于150μm的液滴在15 s内全部沉降至地面,其余液滴在轿厢内扩散悬浮形成飞沫气溶胶。换气次数越大,液滴数减少得越快,但也会使更多的直径大于100μm的液滴向上扩散至呼吸区,增加呼吸道传染病传播的风险。

表面活性物质对海洋飞沫气溶胶的产生和理化性质的影响

由于气候和环境效应的影响,海洋上空气溶胶受到研究者的关注。海水中气泡上升至海面破裂时,会把海洋微表层的表面活性物质富集到海洋飞沫气溶胶中,从而影响其物理和化学性质。总结了海洋表面活性物质的来源及其表征量化方法,阐述了表面活性物质对海洋飞沫气溶胶数浓度及粒径分布的影响,进而归纳了对吸湿性、云凝结核活性和冰核活性的影响机制。由于来源、类型、结构及其他环境条件的不同,表面活性物质对海洋飞沫气溶胶的产生及理化性质的影响具有显著差异,给研究海洋飞沫气溶胶的环境和气候效应造成困难,需要进一步开展表面活性物质的观测和模拟研究,为改进海洋飞沫气溶胶区域和全球建模提供科学支撑。

Preparation and characterization of aluminum foams with ZrH_2 as foaming agent

Aluminum foams were fabricated by melt-based route using ZrH2 as a foaming agent. The factors which affected the foaming of aluminum foams during casting process were investigated. The powdered zirconium hydride with content of 0.6%-1.4% （mass fraction） was added to the molten pure aluminum and the foaming condition was controlled in a temperature range from 933 to 1 013 K, Ca amount of 1.5%-3.0% （mass fraction）, stirring time of 0.5-2.5 min and holding time of 1.5-4.0 min to obtain homogeneous aluminum foams. The fabricated aluminum foams were characterized by XRD, SEM and Image-pro plus. The mechanical properties of the aluminum foams with different relative density were tested. The result indicates that the foaming agent （ZrH2） is suitable for the preparation of small aperture aluminum foams with average pore diameter of 1 mm. Inter-metallic compounds and Al2O3 have effect on the melt viscosity. The aluminum foams experience linear elastic, platforms and densification process and had a higher efficiency of energy absorption.

病毒通过气溶胶传播扩散及感染概率模拟——以地铁车厢为例

[背景]地铁作为人流密集型场所,极有可能发生病毒的气溶胶传播,但是缺乏具体的传播概率估计。[目的]模拟地铁车厢中呼吸气溶胶的传播和扩散过程,建立模型并计算人群感染概率。[方法]以上海市10号线箱型列车作为研究对象,通过湍流模型对微小颗粒物进行追踪模拟。建立基于封闭地铁车厢内的模型,通过量子发射-感染概率模型对同车厢的乘客感染概率、病毒量子剂量等进行趋势化分析。[结果]在常见的十二孔空调模式下,飞沫气溶胶在车厢内会随着气流快速扩散至同车厢的各个区域,但短时间内不会扩散到其他车厢。同时由于气流不确定性,车厢内的气流可能会在局部地区盘旋汇聚,飞沫气溶胶在进入盘旋汇聚状态后则向外扩散较慢,或很难向外扩散,乘客会加剧这些区域形成的情况。当空调系统运转正常(通风换气率为23.21 h^(-1)),地铁车厢内一名病毒携带者向同车厢其他乘客通过气溶胶传播病毒的概率约为3.8%。但是当空调系统失灵时(通风换气率为0.5 h^(-1)),这一概率将会高达30%。此外,一名超级传播者(病毒喷吐数>90%普通人),也会将感染概率提升至14.9%。由于车厢内湍流的复杂性,在1/2局部弥散的情况下,感染概率预计扩大至8.9%,或者早晚高峰人流拥挤造成气溶胶浓度上升,感染概率可能会升高至4.7%。普通新冠病毒的地铁传播概率低至0.9%。[结论]结合计算流体力学和感染概率可以看出,地铁作为交通枢纽,在现今常见十二孔空调模式下,虽然人流量大,存在严重的时空交汇问题,但是由于其极好的通风换气性能,具有一定的抵御病毒气溶胶传播的能力。不过由于湍流和乘客位置的影响,飞沫气溶胶可能会在局部地区盘旋,从而导致病毒传播风险增加;同时,存在超级传播者、空调系统的运转状态不佳、早晚人流高峰,也对病毒传播感染概率增加有深刻的影响。

抽丝剥茧 步步为营

湖北 汪洋(先胜)广东 陈富杰(2003年12月3日弈于广州)仙人指路对飞象 1.兵七进一 象3进5 2.马八进七 卒7进1 3.炮二平六 马8进7 4.马二进三 车9平8 5.相三进五 炮2平4 陈富杰大师以飞象应对仙人指路,希图较量散手棋。

Oxide film on bubble surface of aluminum foams produced by gas injection foaming process

Based on A356 aluminum alloy,aluminum foams were prepared by gas injection foaming process with pure nitrogen,air and some gas mixtures.The oxygen volume fraction of these gas mixtures varied from 0.2%to 8.0%.Optical microscopy,scanning electron microscopy（SEM） and Auger electron spectroscopy（AES） were used to analyze the influence of oxygen content on cell structure,relative density,macro and micro morphology of cell walls,coverage area fraction of oxide film,thickness of oxide film and other aspects.Results indicate that the coverage area fraction of oxide film on bubble surface increases with the increase of oxygen content when the oxygen volume is less than 1.2%.While when the oxygen volume fraction is larger than 1.6%,an oxide film covers the entire bubble surface and aluminum foams with good cell structure can be produced.The thicknesses of oxide films of aluminum foams produced by gas mixtures containing 1.6%-21%oxygen are almost the same.The reasons why the thickness of oxide film nearly does not change with the variation of oxygen content and the amount of oxygen needed to achieve 100%coverage of oxide film are both discussed.In addition,the role of oxide film on bubble surface in foam stability is also analyzed.

Oxidation kinetics of oxide film on bubble surface of aluminum foams produced by gas injection foaming process

In the range of 620？710 °C, air was blown into A356 aluminum alloy melt to produce aluminum foams. In order to study the influence of temperature on the thickness of oxide film on bubble surface, Auger electron spectroscopy （AES） was used. Based on the knowledge of corrosion science and hydrodynamics, two oxidation kinetics models of oxide film on bubble surface were established. The thicknesses of oxide films produced at different temperatures were predicted through those two models. Furthermore, the theoretical values were compared with the experimental values. The results indicate that in the range of 620？710 °C, the theoretical values of the thickness of oxide film predicted by the model including the rising process are higher than the experimental values. While, the theoretical values predicted by the model without the rising process are in good agreement with the experimental values, which shows this model objectively describes the oxidation process of oxide film on bubble surface. This work suggests that the oxidation kinetics of oxide film on bubble surface of aluminum foams produced by gas injection foaming process follows the Arrhenius equation.

Formation Mechanism and Size Prediction of Bubble in Opposite-Flowing T-Shaped Microchannel

Bubble formation in an opposite-flowing T-shaped microchannel with 40 μm in depth and 120 μm in width was real-time visualized and investigated experimentally by means of a high speed camera. N2 bubbles were generated in glycerol-water mixtures with different concentrations of surfactant sodium dodecyl sulfate (SDS). And the images were captured by the high speed camera linked to a computer. Results indicated that the bubble formation process can be distinguished into three consecutive stages, i.e., expansion, collapse and pinching off. The bubble size decreases with the increase of liquid flow rate and viscosity of liquid phase as well as the decrease of gas flow rate. The surface tension of the liquid phase has no measurable influence on the bubble size. Moreover, a new approach to predicting the size of bubbles formed in the T-shaped microchannel is proposed. And the predicted values agree well with the experimental data.

Nanobubble generation and its application in froth flotation (part I): nanobubble generation and its effects on properties of microbubble and millimeter scale bubble solutions

A special nanobubble generation system has been developed for evaluating the effect of nanobubble on froth flotation. In this study, an eight-factor five-level Central Composite Experimental Design was conducted for investigating eight important parameters governing the median size and the volume of nanobubbles. These process parameters included surfactant concentration, dissolved oxygen (O2) content, dissolved carbon dioxide gas (CO2) content, pressure drop in cavitation tube nozzle, <50 nm hydrophobic particle concentration, <50 nm hydrophilic particle concentration, slurry temperature and the time interval after nanobubble generation. The properties, stability and uniformity of nanobubbles were investigated. The study of the produced nanobubble’s effects on the characteristics of microbubble solutions and millimeter scale bubble solutions was performed in a 50.8 mm column.

Langmuir单分子膜在海洋飞沫气溶胶表面特性研究中的应用

被表面活性有机物包裹的液相气溶胶,如海洋飞沫气溶胶(SSA),通常具有反胶束的结构,它由有机分子形成的疏水表面和一个水相内核构成。SSA界面有机膜的组分和形态对其物理、化学和光学特性有重要的影响。Langmuir单分子膜是由脂肪酸、脂肪醇和磷脂等具有低挥发性的长链表面活性有机物在空气-水界面上扩散形成的单层分子薄膜。采用Langmuir槽可以测定水-气界面的单组分或复合组分单分子膜的表面压随分子面积变化的曲线(π-A曲线),从而揭示相应单分子膜的界面特性,进而预测表面活性剂在实际SSA中的命运和行为。本文综述了常用大气气溶胶界面表征技术、基于单分子膜建立的SSA模型以及有机膜对SSA大气行为的影响。虽然目前对SSA相关单分子膜的物理性质和形貌变化已有深入的研究,但是对于反应性气体、光照和生物活性物质等环境因素引起的界面变化却很少有关注,本文为未来的实验室模拟和模式研究提供了新的思路。

Clustering-driven watershed adaptive segmentation of bubble image

In order to extract froth morphological feature,a bubble image adaptive segmentation method was proposed.Considering the image's low contrast and weak froth edges,froth image was coarsely segmented by using fuzzy c means(FCM) algorithm. Through the attributes of size and shape pattern spectrum,the optimal morphological structuring element was determined.According to the optimal parameters,some image noises were removed with an improved area opening and closing by reconstruction operation,which consist of image regional markers,and the bubbles were finely separated from each other by watershed transform.The experimental results show that the structural element can be determined adaptively by shape and size pattern spectrum,and the froth image is segmented accurately.Compared with other froth image segmentation method,the proposed method achieves much high accuracy,based on which,the bubble size and shape features are extracted effectively.

新型冠状病毒疫情期间口腔诊疗中防控措施及意义

2019年12月中旬以来,武汉市暴发新型冠状病毒(2019-nCoV)感染疫情,很快扩散到全国各地,形势非常严峻。国家已将新型冠状病毒肺炎(COVID-19)列入《中华人民共和国传染病防治法》规定的乙类传染病,并采取甲类传染病的预防和控制措施进行管理。目前已发现2019-nCoV主要通过呼吸道飞沫和密切接触传播,在相对密闭的环境中长时间暴露于高浓度气溶胶情况下存在经气溶胶传播的可能[1]。