NOx与NMHC的变化对O3 生成量的影响

利用LLA-C光化学反应机制,在NOx体积分数φ变化范围很广（1.75～350.0,单位为10-9,以下同）的条件下,选择18种NMHC与NOx的体积分数比（2.0～200.0）模拟分析在什么条件下NMHC的改变对臭氧生成量不大敏感而主要依赖于NOx的大小,同时给出相应条件下OH模拟值的变化。结果表明,OH峰值均出现在φ(NMHC/NOx)≈8.0。所找条件是φ(NOx)≤50.0时要求φ(NMHC/NOx)≥60.0;φ(NOx)>50.0时需要8.0≤φ(NMHC/NOx)≤28.0。相应O3生成量的最大误差小于20%。该条件正适合我国典型污染城市当前φ(NOx)水平和φ(NMHC/NOx)范围,可用于我国区域尺度空气质量模拟。与实测资料的对比还有待进一步开展。     

对流层氮氧化物光化学转化特征研究

应用大气光化学模式研究了日间影响NOx光化学转化率的主要物理化学因子.探讨了在不同NMHC/NOx比值时,NOx光化学特征及其转化产物的变化规律.结果表明,影响NOx转化率的主要因子是阳光辐射强度和NMHC/NOx比值.但在NMHC/NOx比值很低时,光强的增加并不能显著提高NOx转化率.温度和初始臭氧浓度对NOx转化率的影响次之.相对湿度对NOx转化率的影响较小.在不同NMHC/NOx比值下,NOx转化特征和产物有很大区别.NMHC/NOx比值高时,产物中PAN＞HNO3.NMHC/NOx比值中(低)时,产物主要是HNO3,PAN等有机氮不到10%(1%).最后初步比较了模拟和观测的NOy组成.     

非甲烷碳氢化合物的光化学臭氧生成潜势的数值模拟研究

应用大气光学模式研究了不同ＮＭＨＣ／ＮＯｘ比值时,各ＮＭＨＣ物种的光化学臭氧生成潜势指数（Ｉｐｏｃｐ值）,探讨了在较高ＮＭＨＣ／ＮＯｘ比值时,各ＮＭＨＣ物种Ｉｐｏｃｐ值随时间的变化规律。结果表明：不同结构、种类的ＮＭＨＣ对光化学臭氧贡献有很大差异;各ＮＭＨＣ物种的Ｉｐｏｃｐ值随ＮＭＨＣ／ＮＯｘ比值、,光化学反应的时间尺度变化而系统性地变化。ＮＯｘ烯烃、芳烃和醛类的活性高寿命短,输送距离有限,主要表     

近地面O3变化化学反应机理的数值研究

利用中尺度气象模式（MM5）及区域化学模式（RADM）对中国地区近地面O3变化化学反应机理进行了数值模拟研究。主要研究了近地面O3变化与其主要前体物NMHC（非甲烷烃）、NOx、CO等之间复杂相互作用关系。主要结论为:（1） 污染地区近地面O3变化主要受光化学作用控制;而清洁地区地面O3变化主要受大气背景O3浓度影响。（2）NMHC和NOx的变化对HO2和OH自由基的影响是十分复杂的,O3的反馈作用对自由基的影响是不可忽视的。（3）在高NOx污染地区的地面上空可能出现高O3污染。（4）在O3光化学反应机理中同样存在线性相关关系。     

区域性光化学模式与LLA-C机制的模拟性能比较

以LLA-C机制为基准,在[NOx]比率分别为1.79、7.14、28.6条件下测试了区域性光化学模式（ROS）的模拟性能。结果表明ROS模式在上述三种初值条件下均能从总体趋势上给出与LLA-C机制相似的结果,但只有当非甲烷烃浓度较高（[NMHC]/[NOx]>12）时ROS模式模拟值与LLA-C机制预测值比较接近。在这种条件下,ROS模型对OH的预测值有待改进。我国大气中相当高的[NMHC]/[NOx]比率说明ROS模式用于全国范围内的空气质量趋势模拟是可行的。     

高NOx条件下非甲烷烃体积分数的变化对O3生成量的影响

利用ＬＬＡ－Ｃ光化学反应机制,在ＮＯＸ保持高值不变时,模拟分布范围很广的８种初始［ＮＭＨＣ］／［ＮＯｘ］（１０９／１０９）（１．０、３．０、７．１、１４．３、２８．６、５７．２、１００．０、２００．０）条件下臭氧体积分数的变化。模拟结果表明,当［ＮＭＨＣ］／［ＮＯｘ］≥１５．０时,臭氧生成量对ＮＭＨＣ的改变不大敏感而主要依赖于ＮＯｘ的大小。但是,当非甲烷烃与氮氧化物的比北较低（＜７．０）时,臭氧生成量紧密地依赖于非甲烷烃体积分数。进一步的验证工作还有待于加强。     

冷锋天气大气边界层内臭氧及 氮氧化物的观测研究

利用北京325 m气象塔作为高空平台,于1997年10月观测到一次冷锋过程大气边界层内O3及NOx体积分数的变化,研究了O3及NOx体积分数与气象要素之间的关系,着重讨论了冷锋过境前后O3及NOx的体积分数变化及其与输送过程的关系。研究表明:北京大气边界层中下层存在明显的O3体积分数垂直梯度,O3的垂直输送与风速及温度梯度密切相关。冷锋过程有利于高层O3向低层输送,使O3体积分数垂直梯度明显减小,并使NOx体积分数显著降低。     

临安秋季近地层臭氧的形成及其前体物特征

应用浙江临安1999年秋季观测数据,分析了臭氧及其前体物特征与气象条件的关系。结果表明,该地区臭氧前体物丰富,在合适的天气条件、充足的日照下可以生成高浓度的臭氧;CO、NOx*等一次污染物浓度与大尺度大气扩散稀释能力有关;观测期间临安CO浓度很高;NMHCs以芳香烃含量最高,烷烃、烯烃、炔烃次之,生物排放的烃最少。以观测为基础的光化学模式计算表明,临安光化学臭氧生成率比损失率大一个数量级,中午净臭氧生成率最大可达14.8×10-9h-1。     

德州市冬季大气挥发性有机物污染特征及其对臭氧和二次有机气溶胶生成的贡献

利用气相色谱-质谱仪/火焰离子检测器（Online-GC-MS/FID）对2017年冬季山东德州大气中99种挥发性有机物（VOCs）进行连续测量,研究了VOCs浓度和组分特征、日变化趋势、来源及其对臭氧（O₃）、二次有机气溶胶（SOA）生成的贡献.结果表明,德州大气VOCs平均体积分数为（47.74±33.11）×10^-9,烷烃占比最大,为40.66%.总VOCs及其组分表现出早晚体积分数高、中午体积分数低的日变化规律.德州大气中丙烷、丙烯、苯及甲苯和二氯甲烷分别受到液化石油气挥发、生物质燃烧、机动车排放和溶剂使用等人为源的影响.反向轨迹模型分析发现,北方内陆气团对德州VOCs体积分数具有一定贡献.烷烃、烯烃、芳香烃的臭氧生成潜势分别为（34.87±33.60）、（120.48±118.76）和（59.77±94.14）μg/m³,乙烯、丙烯、甲苯和间/对二甲苯的贡献较大.芳香烃氧化主导了SOA生成,其贡献率为93.7%,甲苯、间/对二甲苯、苯对SOA生成的贡献最大.为解决大气复合污染问题、实现臭氧和PM_2.5协同控制,德州应重点控制甲苯、间/对二甲苯等芳香烃的排放.     

区域化学输送模式中NO x和O3源示踪法的引入

发展了化学输送模式中氮氧化合物(NOx)和臭氧(O3)的一种源示踪方法,对这种示踪法及其应用模式作了详细介绍,并结合臭氧光化学反应机理的分析描述了NOx和O3示踪物浓度方程的推导过程。将这种示踪法引用到区域化学输送模式中,并以太原和石家庄地表NOx人为排放产生的活性氮化物和臭氧为例,演示了污染物向北京的输送过程,模拟的O3,NOx和NOz示踪物浓度时空分布与O3,NOx和NOz在大气中的衰减尺度分析一致,表明该示踪法是一种有效的研究区域氮氧化物以及臭氧来源和输送转化过程的方法。个例模拟分析结果显示:太原和石家庄的地表人为排放产生的NOx本身并不能输送到北京,但通过它们产生的O3和HNO3可以输送到北京,对北京地表附近大气污染造成影响。     

MEASUREMENTS AND MODEL SIMULATIONS OF SURFACE OZONE VARIATIONS AT DIFFERENT BACKGROUND CONCENTRATIONS OF THE PRECURSORS

Ozone photochemical production and loss in very different environments at Waliguan baselinestation and Lin'an background station were simulated by using the measurement data and photo-chemical box model.The results show that net ozone photochemical production rate is negative,about 0.5 ppb/d,at Waliguan baseline sation,because of very low precursor concentrations.Butat Lin'an background station,the net photochemical ozone production is positive,about 2—3 ppb/h.which is very closed with the measurement at Lin'an.That means ozone production was con-trolled by photochemical reactions at Lin'an background station,because of the higher precursorconcentrations.The net destruction rate,at Waliguan Mt.,is not large,so that future increase inanthropogenic emission of reactive nitrogen will lead to larger production rates of steady-state O_3concentration.     

MEASUREMENTS AND MODEL SIMULATIONS OF SURFACE OZONE VARIATIONS AT DIFFERENT BACKGROUND CONCENTRATIONS OF THE PRECURSORS*

Ozone photochemical production and loss in very different environments at Waliguan baseline station and Lin'an background station were simulated by using the measurement data and photochemical box model.The results show that net ozone photochemical production rate is negative,about 0.5 ppb/d,at Waliguan baseline sation,because of very low precursor concentrations.But at Lin'an background station,the net photochemical ozone production is positive,about 2-3 ppb/h.which is very closed with the measurement at Lin'an.That means ozone production was controlled by photochemical reactions at Lin'an background station,because of the higher precursor concentrations.The net destruction rate,at Waliguan Mt.,is not large,so that future increase in anthropogenic emission of reactive nitrogen will lead to larger production rates of steady-state O₃ concentration.     

Interpretation of Mid-Stratospheric Arctic Ozone Measurements Using a Photochemical Box-Model

In this study measurements of mid-stratospheric Arctic ozone are compared with model simulations. The measurements obtained at Spitsbergen (79°N, 12°E) by ground based millimeter-wave radiometry exhibit large day to day variabilities as well as periods with low ozone. To interpret these measurements, calculations were made using the new photochemical box-trajectory model BRAPHO, with air parcel trajectories calculated from analyzed wind fields. Using a relatively simple approach, the model reproduces the observed ozone variability well, including inter-annual variations. The explanation for the observed ozone behavior is that at these altitudes ozone is determined by what we call dynamically controlled photochemistry. This means that the photochemical evolution of the ozone volume mixing ratio is mainly controlled by the atmospheric dynamics, in particular the solar zenith angle the air parcel has experienced.     

Smog Chamber Study on the Ozone Formation Potential of Acetaldehyde

Acetaldehyde is one of the important VOC species of O3 precursors in the atmospheric environment. The influences of relative humidity (RH) and initial VOC/NOx ratio (RCN) on the formation of O3 are studied in smog chamber experiments, and the MCM v3.3.1 mechanism of acetaldehyde is modified based on the experimental results. In low-RH conditions (RH= 11.6％±1.1％), the O3 concentration at 6 h increases first and then decreases with the increase of RCN, and the RCN at the inflection point of O3 concentrations is 3.2. In high-RH experiments (RH = 78.8％±1.0％), variation of the O3 concentration at 6 h with RCN is similar to that in low-RH experiments, but the RCN at the inflection point is 2.8. RH has no significant effect on the O3 concentrations under low RCN (< 3), whereas it has a negative effect under high RCN (> 3). Compared with the experimental results, original MCM v3.3.1 greatly underestimates the O3 concentrations. Addition of both the photolysis process of peroxyacetyl nitrate and the photolysis process of HNO3 on the reactor surface into the original MCM can reduce the difference between the simulated O3 concentrations and the experimental results at 6 h from 24％-35％ and 17％-49％ to 6％-26％ and 10％-42％ under low- and high-RH conditions, respectively. The maximum incremental reactivity (MIR) of acetaldehyde simulated with the modified MCM is 4.0 ppb ppb-1 without considering the effect of other VOCs.     

Comparison of the EMEP, RADM2 and RACM Mechanisms

A comparison of the atmospheric chemistry mechanisms EMEP (Co-operative Programme for Monitoring and Evaluation of the Long-Range Transmission of Air Pollutants in Europe), RADM2 (Regional Acid Deposition Model, version 2) and RACM (Regional Atmospheric Chemistry Mechanism) has been conducted. Each mechanism was used to simulate the PLUME case of Kuhn et al. (1998) and to simulate an additional 150 and 81 scenarios with and without emissions, respectively. These simulations covered scenarios that ranged from relatively clean, through rural and polluted urban conditions. Ozone isopleths and scatter plots were generated from the simulations. The mechanisms were compared primarily on the basis of calculated ozone and ozone precursor concentrations. For the gas-phase ozone precursors the differences between the mechanisms were rather small under clean conditions and more significant under polluted conditions. The differences were especially significant for the concentrations of NO₂ and organic peroxy radicals. In general the EMEP mechanism yielded the most ozone and the RADM2 mechanism yielded the least. Furthermore the results suggest that a broad range simulation conditions should be used to compare mechanisms and not just a few selected scenarios.     

应用查表法模拟区域对流层O3、Nox分布和演化的研究

应用STEM-II气相光化学模式探讨了影响对流层O3、NOx气相光化学转化率的各物理、化学因子。表明在我国多数地区光化学污染物特征(NMHC/NOx较高)下,光辐射强度、温度、初始O3浓度和NOx浓度是影响O3、NOx气相光化学转化率的主要因子。将以上因子分档组合,计算并建立了各种情况下O3、NOx气相光化学转化率的查算表,并将之用于模拟区域O3、NOx的演化和分布。结果表明,与光化学模式直接耦合计算法相比,该方法既能显著缩短计算时间,又能基本反映大气化学反应的非线性过程,并与直接耦合法符合得较好。     

南京及周边黑碳气溶胶对臭氧影响的观测分析和数值模拟

利用南京地面站点2016—2017年黑碳气溶胶(Black Carbon, BC)和臭氧(O_3)逐小时观测资料,对比分析了不同季节BC与近地面O_3的关系。结果表明,高BC(高于平均值)影响下的O_3质量浓度值明显比低BC(低于平均值)影响下的O_3质量浓度值低,这种抑制作用在秋冬季明显高于春夏季,且BC与O_3的负相关性在秋冬季显著高于春夏季,而PM_(2.5)与O_3的负相关性不显著。利用WRF-Chem模式,对2017年12月个例开展BC反馈效应对O_3影响的数值模拟,结果再次证实BC对O_3存在负反馈影响。其影响机制是:BC可通过抑制边界层发展,使近地面NO_x积聚,从而减少臭氧的化学生成(VOCs控制区);BC可通过抑制边界层垂直湍流交换,减少边界层上部高O_3向下的湍流输送,从而减少近地面O_3;BC可通过减小近地面风速,减少O_3的平流输入,从而减少地面O_3。不同个例的主要控制因子不同。     

A Review of Atmospheric Chemistry Research in China: Photochemical Smog, Haze Pollution, and Gas-Aerosol Interactions

In this paper we present a review of atmospheric chemistry research in China over the period 2006-2010, focusing on tropospheric ozone, aerosol chemistry, and the interactions between trace gases and aerosols in the polluted areas of China. Over the past decade, China has suffered severe photochemical smog and haze pollution, especially in North China, the Yangtze River Delta, and the Pearl River Delta. Much scientific work on atmospheric chemistry and physics has been done to address this large-scale, complex environmental problem. Intensive field experiments, satellite data analyses, and model simulations have shown that air pollution is significantly changing the chemical and physical characters of the natural atmosphere over these parts of China. In addition to strong emissions of primary pollutants, photochemical and heterogeneous reactions play key roles in the formation of complex pollution. More in-depth research is recommended to reveal the formation mechanism of photochemical smog and haze pollution and their climatic effects at the urban, regional, and global scales.