人类活动引起的对流层臭氧浓度的全球变化

地面观测记录表明,北半球对流层中臭氧的平均浓度一直在升高。特别是近年来的观测数据与巴黎Montsouris实验室测定的1876—1910年的数据相比较说明,地球中—高纬度地区近地面大气中的臭氧浓度在过去100年间增加了两倍多。这一结果对探讨一系列环境问题具有深远的意义。因为臭氧浓度的升高对人类及生态系统有直接影响,又由于臭氧是一种强辐射气体,所以如果大气中臭氧浓度升高则会引起显著的全球变暖。本文采用对流层全球模式对工业化以前及现在的大气化学进行了模拟研究,发现工业化以前近地面大气中臭氧浓度与Montsouris实验室所分析的同期臭氧浓度值相同。另外,根据模拟计算所得现在大气中的臭氧浓度与目前对各种大气化学组份的观测结果相吻合。依据对人类排放的氮氧化物(NO_x)的未来增长速度的估计，已有人对2020年的大气臭氧浓度作了类似的计算。基于上述推测，对流层大气中臭氧浓度将会以比过去100年更快的速度增长。因此，在评价大气污染排放物的影响以及制定适当控制它们的措施时，应考虑对流层大气臭氧浓度的未来变化。     

对流层活性卤素化学:充满机遇和挑战的研究领域

活性卤素物种(RHS)参与大气对流层中许多化学过程,影响许多重要物种的源和汇,在大气对流层化学中起着十分重要的作用,因此对流层活性卤素化学成为近年来国际大气化学研究的重要前沿研究领域。RHS在对流层的外场观测方法主要包括化学放大、大气压化学电离质谱（APCIMS）、长程差分吸收光谱（DOAS）、雾室和湿法化学分析法、光解法、碳同位素的比率法等。各种观测方法表明大气边界层中存在着不同种类的RHS,特别在海洋边界层、极地边界层和盐湖地区。RHS的浓度有较大的变化范围（10-12~10-10）。RHS可引起一些VOCs的氧化,影响HOx和NOx的反应,减少对流层O3,并对硫的氧化和汞化学有较大的影响。对流层RHS的源主要为有机卤素化合物的排放和海盐气溶胶的释放。在讨论RHS在对流层的循环转化的基础上,归纳总结出一个示意图;提出了现有的主要科学问题,进而展望了今后的研究前景。     

关于研究四川盆地温室效应及其研究方法的建议

四川盆地温室效应的研究具有丰富的地球科学意义，并且对农业生产和农业科学研究具有指导作用。为此，建议应尽早调查盆地当今和历史温室气体的排放率以及大气的化学组成情况；研究近几万年来以盆地古气候的变化特点。建议并指出该项研究的关键问题是寻求盆地近百年气候变化与温室气体的统计关系，同时预测２１世纪中期前四川盆地未来气候的变化趋势。     

大气氧化态活性氮循环与稳定同位素过程：问题与展望

大气中氧化态活性氮主要包括氮氧化物(NOX=NO+NO2)和硝酸等。NOX的循环过程会影响臭氧和羟基自由基的浓度,进而影响大气氧化能力。NOX的氧化终端产物硝酸是颗粒污染物的重要组成部分,其干湿沉降过程会对生态系统产生影响。氮稳定同位素(δ15N)在大气活性氮循环,示踪区域和全球活性氮排放、传输和沉降等研究方面都展现出了一定的潜力。回顾目前用δ15N研究NOX排放和大气活性氮循环的现状,从NOX的产生机制和收集分析方法等方面讨论NOX源δ15N数据的不确定性及原因,分析NOX和硝酸在大气转化和传输过程中氮同位素的分馏效应和影响等,最后讨论用δ15N示踪NOX排放的可能性和问题。虽然目前用δ15N量化示踪排放源还存在比较大的不确定性,但是δ15N可以有效地示踪大气活性氮循环和转化过程。在此基础上,有望利用大气化学传输模型,结合同位素观测数据和分馏机制,对区域和全球大气活性氮循环过程中的同位素效应进行综合评估,提高用δ15N研究大气氧化态活性氮来源以及循环的准确性和可靠性。     

臭氧变化及其气候效应的研究进展

综述了近２０年来臭氧变化的规律和机制及其气候效应等领域的研究进展,指出对流层臭氧（主要在北半球）增加、平流层臭氧减少和臭氧总量减少是全球臭氧的变化趋势,原因主要是人类活动导致的ＮＯｘ、ＮＭＨＣ、ＣＯ、ＣＨ４等对流层臭氧前体物的增加和ＮＯｘ、Ｈ２Ｏ、Ｎ２Ｏ、ＣＦＣｓ等平流层臭氧损耗物质的增加。臭氧变化引起的气候效应表现在对流层臭氧的增加将带来地表和低层大气的升温,平流层臭氧的减少则可能导致地表和低层大气的升温或降温。将全球或区域气候模式和大气化学模式进行完全耦合来研究臭氧变化的气候效应是一种十分有效的手段,具有广阔的应用前景。     

大气甲烷浓度变化的源汇因素模拟研究进展

从甲烷大气化学过程、传输模式和反向模拟机理等方面综述了大气甲烷浓度变化及其源汇研究的主要进展及存在的问题。基于数据同化算法的反向模拟能有效降低全球及国家尺度甲烷排放估计的不确定性。但在具体的算法实施中,先验的甲烷排放估计和地面站大气甲烷浓度测定的不确定性量化仍然主要是经验性的,缺乏严格和系统性的量化算法。相对于有限的地面站测定,基于卫星平台的大气甲烷浓度变化监测数据极大地提高了数据的空间覆盖度,进一步促进了反向模拟的应用。当前的反向模拟研究在全球尺度上确认了自然湿地甲烷排放对大气甲烷浓度年际波动的决定性作用;在国家尺度上,反向模拟在国家温室气体清单的"可核查"方面也有广泛的应用前景。     

平流层-对流层交换研究进展

平流层与对流层之间的物质输送和混合（STE）是控制自然和人为排放的化学痕量物质对大气成分影响的一个重要过程。STE可以影响温室气体在上对流层和下平流层中的垂直分布，进而影响气候。要预报全球气候变化就必须了解平流层与对流层之间动力、化学及辐射的耦合。从 STE研究的尺度问题，热带和中纬度地区STE研究以及我国STE研究现状进行了评述。STE具有多种尺度和形式，热带外平流层由波强迫驱动的全球尺度环流，可以诊断长时间尺度的STE，它不能充分描述短时间尺度过程。热带外低平流层环流不能简单地描述为纬向平均，要正确描述痕量气体的分布必须包含纬向非对称的天气尺度过程。热带地区的滴漏管理论提供了一个新的诊断 STE框架。目前对中纬度地区对流层顶折叠和切断低压的研究是比较充分的。     

上对流层/下平流层大气垂直结构研究进展

大气上对流层与下平流层区域是对流层与平流层之间的过渡区域,热带对流层顸确定了全球整个平流层的化学边界条件,该区域大气的垂直结构及变化对于平流层一对流层交换和上对流层/下平流层大气成分收支有重要影响;该区域也是大气动力、热力和大气成分结构发生巨大转换的区域,辐射过程、多尺度动力学过程、化学过程和微物理学过程等都起着同样重要的作用,对流层顶变化也是人类活动引起气候变化的一个敏感指示因子,因此关于对流层顶的研究(尤其是其精细结构和过程)重新唤起了人们的关注.针对对流层顶的各种定义(包括热力学、动力学和化学成分)以及它们相互之间的关系、对流层顶是一个面还是层以及对流层与平流层之间的转换特征、对流层顶强逆温层的特征及形成原因等基本科学问题,回顾了近年来的一些重要研究进展.     

概论N2O大气浓度演变及其大气化学

Ｎ２Ｏ在对流层中是长寿命的痕量温室气体,在平流层,它是破坏Ｏ３层主要痕量气体之一－ＮＯ的生成源。本文主要综述了Ｎ２Ｏ的大气浓度演变,大气寿命,对温室效应的贡献,大气化学等,着重探讨了可能存在的Ｎ２Ｏ大气生成和消耗过程。     

IPCC第一工作组第五次评估报告对全球气候变化认知的最新科学要点

2013年9月27日, 在瑞典首都斯德哥尔摩, 联合国政府间气候变化专门委员会第一工作组第五次评估报告《Climate Change 2013: The Physical Science Basis》决策者摘要(Summary for Policymakers, SPM)发布, 随后于9月30日公布了报告全文. 报告指出, 全球气候系统变暖的事实是毋庸置疑的, 自1950年以来, 气候系统观测到的许多变化是过去几十年甚至近千年以来史无前例的. 全球几乎所有地区都经历了升温过程, 变暖体现在地球表面气温和海洋温度的上升、 海平面的上升、 格陵兰和南极冰盖消融和冰川退缩、 极端气候事件频率的增加等方面. 全球地表持续升温, 1880-2012年全球平均温度已升高0.85 ℃[0.65～1.06 ℃]; 过去30 a, 每10 a地表温度的增暖幅度高于1850年以来的任何时期. 在北半球, 1983—2012年可能是最近1 400 a来气温最高的30 a. 特别是1971-2010年间海洋变暖所吸收热量占地球气候系统热能储量的90%以上, 海洋上层(0～700 m)已经变暖. 与此同时, 1979-2012年北极海冰面积每10 a以3.5%～4.1%的速度减少; 自20世纪80年代初以来, 大多数地区多年冻土层的温度已升高. 全球气候变化是由自然影响因素和人为影响因素共同作用形成的, 但对于1950年以来观测到的变化, 人为因素极有可能是显著和主要的影响因素. 目前, 大气中温室气体浓度持续显著上升, CO₂、 CH₄和N₂O等温室气体的浓度已上升到过去800 ka来的最高水平, 人类使用化石燃料和土地利用变化是温室气体浓度上升的主要原因. 在人为影响因素中, 向大气排放CO₂的长期积累是主要因素, 但非CO₂温室气体的贡献也十分显著. 控制全球升温的目标与控制温室气体排放的目标有关, 但由此推断的长期排放目标和排放空间数值在科学上存在着很大的不确定性.     

On the OH initiated oxidation of C2-C5 aliphatic aldehydes in the presence of mineral aerosols

Clay particles are present in large quantities in mineral dust of atmospheric aerosols, and their interaction with organic species may influence atmospheric reactions and the prediction of environmental risks. However, the kinetics and mechanisms of adsorption and reaction of atmospheric volatile organic compounds on aerosol surfaces are not well understood.In this work, quantum chemical methods are used to study the adsorption of C2-C5 aliphatic aldehydes on silicate clusters active sites, and their subsequent reaction with OH radicals. It is shown that adsorption may occur in two different ways, and that the adsorption complex structure determines the subsequent path of its reaction with OH. The initial step in the OH reaction with acetaldehyde occurs according to the same mechanism as in the gas phase, i.e., the aldehydic hydrogen abstraction. Starting from propanal, another abstraction channel becomes increasingly important, involving mainly the abstraction of a β-hydrogen of the aliphatic chain. In the presence of a silica monomer model surface, the reaction rate of aldehydes with OH free-radicals is smaller than in the gas phase. Furthermore silicates are good sinks for trapping these aldehydes. Thus, our results may have implications in the study of tropospheric chemistry and cosmochemistry.     

Volcanic emissions and the early Earth atmosphere

Despite uncertainties in our understanding of early Earth volcanism and atmospheric composition, thermodynamic modelling is able to offer estimates of the global production of reactive trace species (NO, OH, SO₃, Cl, Br and I) from early Earth volcanism, and thereby to shed light on processes which may have been different in Earth’s early atmosphere. Model results show that thermal decomposition of magmatic H₂O, CO₂ and SO₂ in high-T mixtures of magmatic and atmospheric gases (at T > 1400 °C) generate high levels of reactive trace gas species. Production of these reactive trace species is insensitive to atmospheric CO₂ in mixtures where the atmospheric gas is the minor component and will hence continue during periods of low atmospheric CO₂. Fluxes of NO, OH, Cl, Br and I from early Earth volcanism are predicted to exceed those from modern Earth volcanism as the higher temperature of early Earth emissions compensates for lower levels of O₂ in the atmosphere, compared to the modern Earth. Under certain conditions, the volcanic NO flux from early Earth volcanism is found to be comparable to other sources of reactive N such as lightning NO and photochemical HCN. This is one possible source of fixed nitrogen which may alleviate any postulated Archean nitrogen crisis. Our thermodynamic model reveals that production of SO₃ (a potential precursor for near-source volcanic sulphate and hence ‘primary’ volcanic aerosol) is likely to be significantly lower from early Earth volcanism. Uncertainty in the pathway to near-source sulphate in modern volcanism (i.e., the reaction of SO₃ with water or direct emission) introduces a large uncertainty into the production rate of near-source volcanic sulphate on the early Earth.     

大气硝酸盐中氮氧稳定同位素研究进展

受人类活动和工农业快速发展的影响,大气硝酸盐(NO_3^-)污染越来越严重且已成为世界范围内的环境问题之一。探究大气NO_3^-的稳定同位素组成(δ15N,δ18O和Δ17O),可以为深入理解大气氮循环、有效控制大气NO_3^-污染提供有力依据。综述了目前大气NO_3^-不同来源NOx的δ15N值、NO_3^-的δ15N季节变化特征及主要影响因素,总结了大气中不同氧化剂的δ18O值和Δ17O值,归纳了全球范围内部分大气NO_3^-中δ18O值和Δ17O值的时空分布特征及可能影响因素,回顾了NO_3^-同位素分析测试技术的主要进展,在前期工作基础上提出未来大气NO_3^-稳定同位素研究应更多关注NO_3^-的氧化生成机制(不同类型氧化剂同位素组成时空差异)、不同NOx来源的δ15N组成、借助化学模型开展大气NO_3^-循环过程等方面的研究。     

Sensitivity of the tropical nonlinear stationary Kelvin and Rossby waves to the vertical structure of heating

Idealized experiments using linear (LM) and nonlinear (NM) multilevel global spectral models have been carried out to investigate and understand the impact of nonlinearities on the stationary wave response in the tropical atmosphere and its sensitivity to the vertical profile of heating. It is found that nonlinearities exert a dominant influence on the low-latitude stationary Kelvin and Rossby waves particularly in the vicinity of the forcing region. Our study shows that nonlinear effects on the upper tropospheric response produce prominent eastward displacement of the anticyclonic vorticity and horizontal shifts of the maximum equilibrium divergence relative to the prescribed heating. These changes due to nonlinear terms are found to be quite sensitive to the vertical structure of diabatic heating. The strongest nonlinear effects are found to occur when the vertical level under consideration is strongly forced from below. Detailed vorticity budget calculations indicate that stronger nonlinear contributions from stretching and horizontal advection of relative vorticity favour the generation of upper tropospheric anticyclonic circulation and its eastward displacement. Larger vertical advection and twisting terms appear to oppose the generation of upper tropospheric anticyclonic vorticity. It is found that the nonlinear terms which affect the vorticity generation in the upper levels are crucially controlled by the vertical profile of heating. The mid-tropospheric response due to deep convective heating in the NM is characterized by anomalous equatorial westerlies in the low-latitude Rossby regime and exhibits prominent ageostrophic motions. Such nonlinear effects appear probably because of a vertical shift of the low level circulation anomalies in the NM. In the case of shallow convective heating the occurrence of anomalous zonal flows and ageostrophic motions in the low latitude regions of the NM takes place near the level of the maximum heating. Our study shows that large heating amplitudes and small vertical gradient of heating at a given vertical level together favour generation of anomalous zonal flows and ageostrophic motions in the near equatorial regions. These anomalous basic flows in the low-latitudes have implications on the propagation of transients from the tropics to midlatitudes. Non-linear effects on the lower tropospheric stationary waves are prominently seen in the case of strong low level heating which produces a large strengthening of the lower tropospheric cyclonic anomalies that exhibit distinct eastward shifts in the NM relative to the LM.     

BrO formation in volcanic plumes

Volcanoes have only recently been recognized as a potentially major source of reactive bromine species to the atmosphere, following from the detection of bromine monoxide (BrO) in the plume emitted by Soufrière Hills Volcano, Montserrat. However, BrO is not expected to be emitted in significant quantity from magma, presenting a puzzle regarding its formation. We report here new field measurements of the tropospheric plume emitted by Mt. Etna, Italy, which provide the first direct evidence of fast oxidation of halogen species in a volcanic plume, and lead to an explanation of how BrO is generated from magmatic HBr emissions. We show that the timescale of BrO formation (a few minutes after emission into the atmosphere) is consistent with rapid heterogeneous halogen chemistry involving sulphate aerosol in the plume. The model highlights considerable complexity to the oxidative chemistry of volcanic plumes.     

Study on the sensitivity of the vertical cooling (heat sink) on the displacements of the mid-tropospheric ridge using a linear model

A linear model of the response of a stratified atmosphere to isolated heat sources in spherical coordinates is used to study the maintenance of the mean position of the mid tropospheric ridge and its displacement. It is well known that the performance of the southwest Indian monsoon is related to the latitudinal position of the April 500 hPa ridge along 75‡E. It was demonstrated that an anomalous cooling associated with the increased snow cover in Eurasia can result in moderate southward displacement of the mid-tropospheric ridge. The results of this study indicate that the vertically integrated cooling rate (strength of heat sink) has more effect on the southward displacement of the ridge when the sink is closer to the ridge.     

地下水硝酸盐中氧同位素研究进展

硝酸盐中氧同位素在某些情况下能弥补氮同位素组成无显著差别的不足以及更有效地识别反硝化作用。文中综述了氧同位素检测技术、NO-3 源的氧同位素组成特征和氧同位素的应用等方面的研究进展。检测技术经历了 5个发展过程。大气和土壤环境形成的NO-3 具明显的氧同位素组成差异 ,由此可识别地下水NO-3 是来自含NO-3 化肥或大气沉降NO-3 还是来自土壤环境中的NH+ 4 经微生物硝化作用形成的NO-3 。反硝化作用使δ15N和δ18O成比例线性增加。今后的研究方向是完善检测技术、研究NO-3 中氧来自水和大气比例的影响因素及氮、氧同位素与地球化学和水文模型的结合等。     

Dissolution kinetics and the weathering of mafic minerals

Fayalite, hypersthene, basalt, and obsidian were dissolved in buffered solutions (25°C; pH 4.5 and 5.5) under air, N₂ or O₂ atmospheres, in order to follow the kinetics of dissolution. Each dissolved more rapidly at lower pH values, dissolving most rapidly in the initial few days, followed by slower dissolution for periods up to six months. Dissolution was more rapid when air was excluded. In oxygen atmospheres an Fe(OH)₃ precipitate armors mineral surfaces, thus inhibiting further dissolution, and further affects the solution by scavenging dissolved silica and cations. Dissolution reactions include initial exchange between cations and H⁺, incongruent dissolution of silicate structures, oxidation of Fe²⁺ in solution, precipitation of Fe(OH)₃, and scavenging of dissolved silica and cations by Fe(OH)₃. Dissolution kinetics may explain weathering of mafic rocks and minerals at the Earth's surface, the formation of Fe-oxide coatings on mineral grains, weathering of submarine mafic rocks and intrastratal solution of mafic minerals in buried sandstones. Early Precambrian weathering would have been more rapid before the appearance of large amounts of oxygen in the atmosphere, and continental denudation rates may have been higher than at present because of this effect and the predominance of mafic igneous rocks at an early stage of continent formation and growth.     

钛基柱撑累托石矿物材料的研究

在氮气环境中用TiCI4和HCI制成钛基柱撑液，采用离子交换法，用[Ti20O32(OH)12(OH2)18]^4 Dawson型Ti多核阳离子，交换累托石蒙皂石质晶层中的Na等阳离子，制成钛基柱撑累托石。通过电子探针定量分析、X射线衍射、红外光谱、热分析及魔角旋转核磁共振等方法，对钛基柱撑累托石的成分、结构和热稳定性进行了表征。钛基柱撑累托石具1．6nm的层孔隙，是一种很有应用前途的柱撑粘土矿物材料，有望在催化剂载体及环保材料领域中得到广泛的使用。