Mechanisms of Photochemical Air Pollution

Selected aspects of the chemistry of photochemical air pollution is discussed and some important, unresolved problems dilineated. The reactive species considered include NO₂, O₃, O(³P), O(¹D), O₂(¹Δ_g), OH and HO₂. Both the kinetics and mechanicsms of the reactions constituting the major tropospheric sources and sinks of these species are treated where available. The application of this information in both computer and smog chamber simulations of photochemical smog is discussed.     

荧光法测定香烟烟气中总的多环芳烃含量

有机溶剂萃取不同香烟烟气焦油中有机物 ,用荧光法分析了烟草的总体特征光谱 ,同时以多环芳烃菲作参比 ,定量分析了各种品牌香烟在去掉过滤嘴和保留过滤嘴条件下 ,烟气在溶剂中的多环芳烃含量 ,为卷烟品质、烟气中有害物质的评价提供了一种实用的测定方法     

乙苯光氧化产生二次有机气溶胶的化学成分及反应机理分析

在自制的烟雾腔内,研究羟基自由基(OH·)启动的乙苯的光氧化反应和一系列后续反应,产生了二次有机气溶胶. 采用空气动力学直径粒谱分析仪分析了气溶胶粒子的尺寸分布;并用自制的气溶胶飞行时间质谱仪快速、实时地测量了单个二次有机气溶胶粒子的分子组分. 初步探讨了这些组分的可能反应机理.     

Low‐Molecular Weight and Oligomeric Components in Secondary Organic Aerosol from the Photooxidation of p‐Xylene

A laboratory study was performed to investigate the composition of secondary organic aerosol (SOA) products from photooxidation of the aromatic hydrocarbon p‐xylene. The experiments were conducted by irradiating p‐xylene/CH₃ONO/NO/air mixtures in a home‐made smog chamber. The aerosol time‐of‐flight mass spectrometer (ATOFMS) was used to measure the size and the chemical composition of individual secondary organic aerosol particles in real‐time. According to a large number of single aerosol diameters and mass spectra, the size distribution and chemical composition of SOA were determined statistically. Experimental results showed that aerosol created by p‐xylene photooxidation is predominantly in the form of fine particles, which have diameters less than 2.5 μm (i.e. PM2.5), and aromatic aldehyde, unsaturated dicarbonys, hydroxyl dicarbonys, and organic acid are major product components in the SOA after 2 hours photooxidation. After aging for more than 8 hours, about 10% of the particle mass consists of oligomers with a molecular mass up to 600 daltons. The possible reaction mechanisms leading to these products are also proposed.     

一种用于研究光化学反应烟雾腔的结构和性能

自制一个烟雾箱,用它研究了苯在大气中的演化过程及其演化产物.在烟雾箱中,对流层太阳光用黑光灯模拟.OH自由基用亚硝酸甲脂光解产生.研究结果表明苯在大气中的演化产物主要是苯酚.     

雾霾对典型地物光谱曲线测量的影响分析

我国雾霾的发生时间成常年化趋势,且在几十年内都可能存在,雾霾对地物光谱曲线测量的影响是不可避免的,而反射率光谱是众多遥感参数反演的基础,因此定量分析雾霾对典型地物光谱曲线测量的影响是丞需解决的问题。本文以简易的雾霾模拟实验室为基础,实际测量了不同雾霾浓度(晴空,浓度分别为35,75,150)下植被、土壤和水泥地的反射率光谱,同时与室外太阳光照下同一样本进行了对比测量和分析。本文首次综合分析不同雾霾浓度对植被、土壤、水泥地等典型地物反射率光谱曲线测量的影响,对定量分析雾霾对遥感监测、应用的影响具有重要意义。主要的研究结论有：草坪、土壤、水泥地等主要地物测量的反射率光谱曲线在晴空时反射率值最高,反射率光谱曲线也最平滑,随雾霾颗粒物浓度的增加,各主要地物的反射率都呈降低趋势,但降幅都不尽相同,降幅没有明显的规律可循;雾霾对各主要地物测量的反射率的影响,在不同波段、不同含水量状况都不尽相同,因此利用统计规律消除雾霾影响有较大困难。雾霾对地物测量的光谱的影响仍需进一步深入研究。     

用于大气化学反应和二次有机气溶胶研究的实验室烟雾箱系统的搭建、测试与初步实验

为了从本质上认识和了解大气氧化反应进程以及二次有机气溶胶的形成机制,设计并搭建了一套实验室模拟烟雾箱系统．将质子转移反应质谱、同步辐射光电离质谱及气溶胶激光飞行时间质谱等特色质谱检测系统与烟雾箱结合,用于大气氧化反应气相和粒子相产物的定量与定性分析．通过一系列表征实验获得了该系统的基本参数,如烟雾箱内温度和光强特征,气体化合物和颗粒物的壁损耗速率,零空气的背景反应性及实验结果的可重复性．臭氧氧化α-蒎烯定量化实验和OH启动异戊二烯光氧化反应的定性检测结果进一步表明了该系统能够满足大气化学反应过程中气相和粒子相化学成分的定性分析及二次有机气溶胶的定量化研究的需要.     

用于研究大气氧化过程和机制的双反应器烟雾箱的评估和应用

设计并搭建了一个新的双反应器烟雾箱, 用于研究可生成臭氧或二次有机气溶胶(SOAs)的大气氧化过程. 该烟雾箱包括一个绝热的箱体及其内部两个体积为5 m³的氟化乙丙烯(FEP)薄膜反应器, 箱内的温度可以精确控制在-10到40 ℃之间. 利用该烟雾箱研究了光源对丙烯气相氧化机理的影响, 发现相对于传统的黑光灯光源, 采用的多重光源所得到的结果可以与模型更好地匹配. 进行了丙烯和间二甲苯的光氧化的初步实验, 发现该烟雾箱可用于模拟可产生臭氧或SOAs的气相氧化过程, 并可以通过不同初始浓度的对比实验找寻不同物种对反应过程的影响. 间二甲苯在不同NO_x条件下光氧化得到的SOA产率与之前的研究比较符合, 这表明该烟雾箱可以实现气-粒转化过程的模拟. 双反应器可以实现在一个关键条件的存在区别, 而其他条件完全一致的情况下的对比实验, 从而帮助我们进一步理解在大气复合污染过程中起关键作用的因素.     

用烟雾箱研究甲苯与OH自由基光化学反应

文中用自制的烟雾腔系统研究了甲苯与OH自由基的光化学反应,得到的结论是其在大气中的主要产物是苯醛、甲基苯酚和苯硝酸甲脂.甲苯在烟雾箱内的寿命约为60分钟.     

Chemical Composition and Reaction Mechanisms for Secondary Organic Aerosol from Photooxidation of Toluene

A laboratory study was carried out to investigate the secondary organic aerosol (SOA) products from photooxidation of the aromatic hydrocarbon toluene. The experiments were conducted by irradiating toluene/CH₃ONO/NO/air mixtures in a home‐made smog chamber. The aerosol time‐of‐flight mass spectrometer (ATOFMS) was used to measure the size and the chemical composition of individual secondary organic aerosol particles in real‐time. According to a large number of single aerosol diameters and mass spectra, we obtained the size distribution and chemical composition of SOA statistically. Expeperimental results showed that aerosol created by toluene photooxidation is predominantly in the form of fine particles, which have diameters less than 2.5 μm (i.e. PM2.5), and the predominant components of aerosol are furane, methyl glyoxylic acid, phenol, benzaldehyde, benzyl alcohol, cresol, 3‐hydroxy‐2,4‐dioxo‐pentanal, methyl nitrophenol, and 5‐hydroxy‐4,6‐dioxo‐2‐heptenal. The possible reaction mechanisms leading to these products were also discussed.