关于大气臭氧问题的主要研究进展

大气臭氧是非常重要的温室气体,其在全球的分布具有不均匀性,受到人类活动的显著影响,近几十年来由于对流层臭氧增加造成正的辐射强迫会增加大气温室效应,而平流臭氧减少会使其吸收的紫外线辐射减少,为负的辐射强迫,使得平流层大气降温。因此关于大气臭氧浓度变化及其对气候的影响是非常复杂的,一直是科学界研究的热点和难点问题。自从20世纪50年代末到70年代就发现臭氧浓度有减少的趋势。1985年英国南极考察队在南纬60°地区观测发现存在大气臭氧层空洞;自此开始,大气臭氧问题引起了世界各国的极大关注,并给予很多研究。目前,平流层和对流层臭氧浓度的观测仍然是研究的重点。鉴于对流层臭氧浓度持续升高和平流层臭氧浓度的不断下降,以及他们在对流层和平流层大气温度中所起的不同作用,本文将主要针对近五年来大气臭氧相关的研究进展进行简要的综述,包括对流层和平流层臭氧浓度及其观测研究,和人类活动的影响等方面进行分述。最后给出目前研究工作的不足和未来工作展望。     

Halocarbons produced by natural oxidation processes during degradation of organic matter

Volatile halogenated organic compounds (VHOC) play an important role in atmospheric chemical processes-contributing, for example, to stratospheric ozone depletion. For anthropogenic VHOC whose sources are well known, the global atmospheric input can be estimated from industrial production data. Halogenated compounds of natural origin can also contribute significantly to the levels of VHOC in the atmosphere. The oceans have been implicated as one of the main natural sources, where organisms such as macroalgae and microalgae can release large quantities of VHOC to the atmosphere. Some terrestrial sources have also been identified, such as wood-rotting fungi, biomass burning and volcanic emissions. Here we report the identification of a different terrestrial source of naturally occurring VHOC. We find that, in soils and sediments, halide ions can be alkylated during the oxidation of organic matter by an electron acceptor such as Fe(III): sunlight or microbial mediation are not required for these reactions. When the available halide ion is chloride, the reaction products are CH3Cl, C2H5Cl, C3H7Cl and C4H9Cl. (The corresponding alkyl bromides or alkyl iodides are produced when bromide or iodide are present.) Such abiotic processes could make a significant contribution to the budget of the important atmospheric compounds CH3Cl, CH3Br and CH3I.     

冬季Hadley环流活动与大气臭氧变化的关系研究

 利用1957年9月到2002年8月,共540个月的ECMWF的经向风和臭氧质量混合比资料,分析研究了冬季Hadley环流强弱特征的变化对臭氧变化的影响.分析指出在冬季伴随Hadley环流的增强,其中心南移,高度升高,臭氧在对流层增加,平流层减少,臭氧总量呈现出减少的趋势.Hadley环流的增强,中心南移,高度升高以及臭氧在对流层的增加对全球变暖是正反馈,而平流层臭氧减少,臭氧总量减少对全球变暖是负反馈.因此Hadley环流的强弱对臭氧的影响明显.     

亚印太交汇区低纬上空不同层次大气臭氧的时空变化分析

 利用ECMWF 195709~200208共45a的多层臭氧质量混合比月平均资料,详细分析了亚印太交汇区(AIPO)低纬地带上空平流层、对流层各层次上臭氧浓度的分布特征.结果表明:①区域上空对流层、平流层及臭氧总量大尺度特征均显著,纬度带分布特征明显;②对流层和平流层臭氧各个季节变化趋势相反,平流层臭氧和臭氧总量各个季节变化趋势一致;同一层次夏季臭氧浓度变化趋势与其他3个季节变化趋势相反;③区域上空20~3hPa是臭氧浓度的高值区,50~30hPa臭氧平均变化幅度最大;④对流层臭氧距平变化在整个高度上较为一致,正、负距平随季节绕赤道做南、北半球摆动,且存在季节性突变;⑤赤道上空有明显从平流层上层随季节逐渐往较低层传播的臭氧正负距平现象.     

大气臭氧耗损的修复

评述了修复大气臭氧耗损的化学法和物理法，某些化学法如在南极旋涡中注入烃类可能由于生成另外的活性氯原子而不能有效地抑制大气臭氧耗损，某些物理法如利用大气电子电荷修复大气臭氧耗损，这是令人感兴趣的方法，它没有其他的化合物生成，但是会遇到技术和光电子材料的难题。在此，提出了另一类修复大气臭氧耗损的新方法，观测到卤代烃在细颗粒物渗溶冰晶表面的低温粘着系数比在冰晶上的粘着系数大2个数量级。因此有可能利用细颗粒物特性和低温非均相反应消除平流层的卤代烃及氯氟烃等达到阻断大气臭氧耗损的链反应。     

Correlation between the anaesthetic effect of halothane and saturable binding in brain

Two theories of the molecular mechanism of volatile anaesthetic action suggest either that anaesthetics cause a generalized perturbation of neuronal membrane structure, probably through a nonspecific interaction with membrane lipids, or that anaesthetics bind to sets of sites of appropriate molecular dimension on membrane proteins. Based on the recent finding that fluorinated anaesthetics can be observed in animal tissue by 19F nuclear magnetic resonance (19F-NMR) spectroscopy, we have used 19F-NMR to quantify the interaction between the volatile anaesthetic halothane and rat brain tissue. Steady-state brain halothane concentration was found to be a non-linear function of inspired concentration, with apparent saturation of brain occurring at inspired halothane concentrations above 2.5% by volume. Using a spin-echo pulse sequence it was found that halothane exists in two distinct chemical environments in brain, characterized by different spin-spin relaxation times (T2), chemical shifts and kinetics of occupancy. Halothane concentration in one of these environments (T2 = 3.6 ms) was saturated at approximately 2.5% inspired halothane; occupancy of this environment was found to correlate with the anaesthetic effect of the drug. In the other environment (T2 = 43 ms), brain halothane concentration was a linear function of inspired concentration. These data suggest the existence of a saturable anaesthetic site for halothane in brain and do not support the concept that anaesthetics act by nonspecific membrane perturbation.     

Atmospheric oxidation capacity sustained by a tropical forest

Terrestrial vegetation, especially tropical rain forest, releases vast quantities of volatile organic compounds (VOCs) to the atmosphere, which are removed by oxidation reactions and deposition of reaction products. The oxidation is mainly initiated by hydroxyl radicals (OH), primarily formed through the photodissociation of ozone. Previously it was thought that, in unpolluted air, biogenic VOCs deplete OH and reduce the atmospheric oxidation capacity. Conversely, in polluted air VOC oxidation leads to noxious oxidant build-up by the catalytic action of nitrogen oxides (NO(x) = NO + NO2). Here we report aircraft measurements of atmospheric trace gases performed over the pristine Amazon forest. Our data reveal unexpectedly high OH concentrations. We propose that natural VOC oxidation, notably of isoprene, recycles OH efficiently in low-NO(x) air through reactions of organic peroxy radicals. Computations with an atmospheric chemistry model and the results of laboratory experiments suggest that an OH recycling efficiency of 40-80 per cent in isoprene oxidation may be able to explain the high OH levels we observed in the field. Although further laboratory studies are necessary to explore the chemical mechanism responsible for OH recycling in more detail, our results demonstrate that the biosphere maintains a remarkable balance with the atmospheric environment.     

A kinetic study of the reaction of ozone with ethylene in a smog chamber under atmospheric conditions

Ozone is one of the key species in the processes of atmospheric chemistry, which can be taken as an indicator of oxidation capacity in the troposphere. The reaction of ozone with reactive gases is an important process in the troposphere. Experimental simulation equipment of smog chamber for atmospheric reactions is used to study the reaction of ozone with ethylene in real atmospheric environment with ozone concentrations of 100―200 ppb. The concentrations of ozone and ethylene were moni-tored during the reaction with the combination of Model 49C-O_3 Analyzer and GC-FID. A rate constant of 1.01×10~(-18) (cm~3·mol~(-1)·s-(~1)) was obtained at 286.5 K, under condition of which the half-life of ozone was 88 min. The results obtained from our experiments are in excellent agreement with those reported previously by other researchers under extremely low pressure in terms of matrixisolation technology. This demonstrates that our equipment of smog chamber for atmospheric reactions is reliable, which can be used for further research of the processes of atmospheric reactions.     

平流层极地臭氧损耗影响对流层气候的研究进展

大气平流层臭氧的严重损耗将导致到达地面的太阳紫外辐射增加已经是公共社会普遍关切的问题。最近几年,平流层臭氧损耗能否对对流层大气环流和气候产生重要影响也引起了广泛的重视,并且已成为大气科学的一个热点问题。观测研究表明近二三十年来在两极臭氧严重损耗的季节,地表气温有明显的变暖趋势,也就是欧亚大陆1—3月份和南极半岛12—5月份的地面温度呈现显著增温。这些增温趋势很可能是平流层两极的严重臭氧损耗造成的。当然,这些增温并非是由臭氧损耗的辐射效应直接造成的,而是通过波－流相互作用以及平流层－对流层相互作用等动力学过程实现的。大量的数值模拟工作也对此问题进行了研究,一些模拟结果与观测结果基本一致,另一些则发现平流层臭氧损耗的强迫作用较弱,也有模拟工作认为其他外界强迫如温室气体增加和热带海面温度升高也非常重要。作者综述了这一研究领域在近几年的最新研究进展,总结有关的观测分析和数值模拟结果,阐述平流层极地臭氧损耗可能影响地面温度的物理机制,以及澄清各种争论要点。     

Direct and indirect effects of solar variations on stratospheric ozone and temperature

We have used a fully coupled chemistry-climate model (WACCM) to investigate the relative importance of the direct and indirect effects of 11a solar variations on stratospheric temperature and ozone. Although the model does not contain a quasi-biennial oscillation (QBO) and uses fixed sea surface temperature (SST), it is able to produce a second maximum solar response in tropical lower stratospheric (TLS) temperature and ozone of approximately 0.5 K and 3%, respectively. In the TLS, the solar spectral variations in the chemistry scheme play a more important role than solar spectral variations in the radiation scheme in generating temperature and ozone responses. The chemistry effect of solar variations causes significant changes in the Brewer-Dobson (BD) circulation resulting in ozone anomalies in the TLS. The model simulations also show a negative feedback in the upper stratosphere between the temperature and ozone responses. A wavelet analysis of the modeled ozone and temperature time series reveals that the maximum solar responses in ozone and temperature caused by both chemical and radiative effects occur at different altitudes in the upper stratosphere. The analysis also confirms that both the direct radiative and indirect ozone feedback effects are important in generating a solar response in the upper stratospheric temperatures, although the solar spectral variations in the chemistry scheme give the largest solar cycle power in the upper stratospheric temperature.     

大气中氮氧化物对生态环境的影响

造成大气污染的氮氧化物主要是一氧化氮和二氧化氮,氮氧化物的危害性如下:①形成光化学烟雾.②易与动物血液中血色素结合.③破坏平流层(同温层)中的臭氧层.④可生成毒性更大的硝酸或硝酸盐气溶胶,形成酸雨.大气中氮氧化物含量的确定是评价人类生存环境质量优劣的重要指标之一,而其测定方法的准确性又是至关重要的.本文通过实验同时介绍了盐酸萘乙二胺分光光度法测定大气中氮氧化物含量方法的改进.     

卤代烷类化合物紫外光解离过程的研究

探讨了在185，253．7，337.1nm的条件下，卤代烷类化合物CH3Br,CH2Br2,CF2ClBr,CF3Br,CF2HCl,CF3Cl的光解离机理，对CH3Br O2/O3,CH2Br2 O2/O3,CF2ClBr O2/O3,CF3Br O2/O3,CF2HCl O2/O3,CF3Cl O2/O3等体系的光化学反应过程及其产物进行了分析，重点讨论了含F卤代烷光氧化的共同产物CF2O的产生机理和它的稳定性，并探讨了控制卤代烷类化合物损耗臭氧层的途径。     

Kinetic study of the reaction of chlorine atoms with 3-methyl-3-buten-1-ol

The reaction of a typical unsaturated alcohol, 3-methyl-3-buten-1-ol （MBO331）, with Cl atoms, was investigated for the first time. The reaction was investigated using discharged flow-tube coupled with electron impact mass spectrometer. The experiments were performed over the temperature range of 248 K-298 K and at pressure of 1 torr in He as the bath gas. The obtained kinetic data were used to derive the Arrhenius expression： k1 = （3.47 ± 1.21） × 10^-11 exp[（ 599 ±69）/7] cm^3 molecule^-1 s^-1. Finally, atmospheric lifetimes of the MBO331 with respect to OH radicals, NO3 radicals and CI atoms have been calculated and the atmospheric implications are considered briefly.     

基于人工神经网络模型的臭氧生成灵敏度预测

本文将臭氧生成灵敏度指标Φ=k_HC+OH［HC］/k_NOx+OH［NO_x］及其影响参数作为输入参数,建立了人工神经网络模型,预测了日本海利尻岛海洋大气边界层臭氧生成的控制因素及其灵敏度特征。预测结果与化学模式计算结果基本一致,证明文中所建立的人工神经网络模型具有较好的预测性能。研究结果表明,人工神经网络模型可以作为一个有效的工具用于对流层臭氧生成灵敏度特征的确定及相关的臭氧消除策略制定。     

Effect of CH3OOH on the atmospheric concentration of OH radicals

Methyl hydroperoxide (CH₃OOH, MHP) is known to be a significant sink and reservoir of HO_x and RO_x radicals in the atmosphere. In order to investigate the impact of MHP on the concentration of atmospheric OH radicals, two key gas-phase reactions of MHP, i.e. the reactions with OH radicals and with UV photolysis, have been simulated at temperature of 293±2 K and total pressure of 1.01×10⁵ Pa, using the long path Fourier transform infrared (LP-FTIR) spectrometry. OH radicals are generated by the photolysis of O₃ in the presence of water vapor. Combined with the relative rate method, the reaction rate constant of MHP with OH radicals is determined to be (3.99±0.15)×10^-12 cm³?molecule^-1?s^-1, and thus the atmospheric lifetime of MHP is estimated at 2.9 days. Furthermore, from detailed analysis of the UV photolysis of MHP, the yield of OH radicals is obtained to be 0.91±0.04. Based on the MHP atmospheric lifetime and the yield of OH radicals, it is concluded that MHP plays an essential role in the redistribution of OH radicals in the troposphere.     

Continuing emissions of methyl chloroform from Europe

The consumption of methyl chloroform (1,1,1-trichloroethane), an industrial solvent, has been banned by the 1987 Montreal Protocol because of its ozone-depleting potential. During the 1990s, global emissions have decreased substantially and, since 1999, near-zero emissions have been estimated for Europe and the United States. Here we present measurements of methyl chloroform that are inconsistent with the assumption of small emissions. Using a tracer transport model, we estimate that European emissions were greater than 20 Gg in 2000. Although these emissions are not significant for stratospheric ozone depletion, they have important implications for estimates of global tropospheric hydroxyl radical (OH) concentrations, deduced from measurements of methyl chloroform. Ongoing emissions therefore cast doubt upon recent reports of a strong and unexpected negative trend in OH during the 1990s and a previously calculated higher OH abundance in the Southern Hemisphere compared to the Northern Hemisphere.     

Effect of CH3OOH on the atmospheric concentration of OH radicals

Methyl hydroperoxide (CH₃OOH, MHP) is known to be a significant sink and reservoir of HO_x and RO_x radicals in the atmosphere. In order to investigate the impact of MHP on the concentration of atmospheric OH radicals, two key gas-phase reactions of MHP, i.e. the reactions with OH radicals and with UV photolysis, have been simulated at temperature of 293±2 K and total pressure of 1.01×10⁵ Pa, using the long path Fourier transform infrared (LP-FTIR) spectrometry. OH radicals are generated by the photolysis of O₃ in the presence of water vapor. Combined with the relative rate method, the reaction rate constant of MHP with OH radicals is determined to be (3.99±0.15)×10^-12 cm³?molecule^-1?s^-1, and thus the atmospheric lifetime of MHP is estimated at 2.9 days. Furthermore, from detailed analysis of the UV photolysis of MHP, the yield of OH radicals is obtained to be 0.91±0.04. Based on the MHP atmospheric lifetime and the yield of OH radicals, it is concluded that MHP plays an essential role in the redistribution of OH radicals in the troposphere.     

CMIP5模拟的平流层21世纪温度变化趋势

21世纪平流层气候变化主要由两个因素所决定,一个是臭氧层恢复造成的变暖,另一个是温室气体增加造成的变冷。针对在这两种相反的辐射效应作用下,平流层气温如何变化这一重要问题, 使用CMIP5未来情景模拟试验的结果, 对2006-2100年间的平流层温度的变化趋势进行分析。结果表明, 臭氧恢复的增温效应在平流层低层起主导作用, 而温室气体增加的冷却效应在平流层高层起主导作用, 因此, 平流层低层(70 hPa 以下)呈变暖趋势, 而平流层中高层呈变冷趋势。通过对包含完整平流层的气候模式(高顶模式)和只包含部分平流层的气候模式(低顶模式)预估的温度趋势的差异进行分析, 发现高顶模式预估的变暖趋势大于低顶模式的结果, 这意味着模式是否包含完整平流层有可能对预估的平流层和对流层未来气候变化有重要影响。     

Extremely cold and persistent stratospheric Arctic vortex in the winter of 2010-2011

Record ozone loss was observed in the stratospheric Arctic in the spring of 2011. In the present work, we show observational evidence that the record loss of Arctic ozone is due to the extremely cold and persistent stratospheric polar vortex in the winter of 2010-2011. The polar vortex was as usual in early winter, but was intensified twice in middle January and middle February, respectively, and remained anomalously strong and stable until early April, 2011. Record low polar temperatures and record high subpolar zonal winds occurred in February and March. Stratospheric wave activity was anomalously weak because waves were refracted equatorward by the anomalously strong polar night jet. With such an extremely cold and isolated environment, Arctic stratospheric ozone was largely depleted in March and early April, 2011. Corresponding to Arctic ozone depletion, the stratospheric Northern-Hemisphere Annular Mode (NAM) displayed anomalously strong high-polarity, and the positive stratospheric NAM propagated downward and led to anomalously strong positive NAM in the troposphere and near the surface.     

Natural methyl bromide and methyl chloride emissions from coastal salt marshes

Atmospheric methyl bromide (CH3Br) and methyl chloride (CH3Cl), compounds that are involved in stratospheric ozone depletion, originate from both natural and anthropogenic sources. Current estimates of CH3Br and CH3Cl emissions from oceanic sources, terrestrial plants and fungi, biomass burning and anthropogenic inputs do not balance their losses owing to oxidation by hydroxyl radicals, oceanic degradation, and consumption in soils, suggesting that additional natural terrestrial sources may be important. Here we show that CH3Br and CH3Cl are released to the atmosphere from all vegetation zones of two coastal salt marshes. We see very large fluxes of CH3Br and CH3Cl per unit area: up to 42 and 570 micromol m(-2) d(-1), respectively. The fluxes show large diurnal, seasonal and spatial variabilities, but there is a strong correlation between the fluxes of CH3Br and those of CH3Cl, with an average molar flux ratio of roughly 1:20. If our measurements are typical of salt marshes globally, they suggest that such ecosystems, even though they constitute less than 0.1% of the global surface area, may produce roughly 10% of the total fluxes of atmospheric CH3Br and CH3Cl.