平流层臭氧季节变化的动力和光化学作用之比较

1992年到2005年的HALOE资料显示, 在臭氧光化损耗中, ClOx 和NOx 的贡献大小和作用位置有所差异。SOCRATES3模式模拟表明, 两半球夏季高纬极区的臭氧减少, 主要是NOx的化学贡献; 北极春季和南极冬季副极地臭氧的变化, 主要是动力输送引起。南、北极春季臭氧减少的化学机制也有所不同, 南极春季的臭氧耗损包括极区内ClOx 的异相化学作用和副极区NOx的化学作用; 北极春季的臭氧耗损主要以NOx 和ClOx 的气相化学作用为主, 其中NOx 的作用更大。动力和光化学在臭氧变化中的贡献表明, 整个中低平流层及低纬平流层高层的动力输送贡献可达到45%, 而高纬平流层中上层, 化学作用贡献在65%以上。     

High-Latitude Springtime Photochemistry. Part I: NOx, PAN and Ozone Relationships

Springtime measurements of NO_x, ozone, PAN,J(NO₂), and other compounds were made near Ny-Ålesund,Svalbard (78°54N, 11°53E), in 1994 and Poker Flat,Alaska (65°08N, 147°29W), in 1995. At Svalbard medianmixing ratios for PAN and NO_x of 237 and 23.7 pptv,respectively, were observed. The median mixing ratios at Poker Flat for PANand NO_x were 79.5 and 85.9 pptv, respectively. These data areused to estimate thermal PAN decomposition using several differentapproaches. At Svalbard PAN decomposition was very small, while at PokerFlat up to 30 pptv/h PAN decomposed. At both sites the NO_x/PANratio increased with temperature between –10 and 20°C implyingthat PAN decomposition is an important NO_x source. In-situozone production was calculated from the measured NO, NO₂,O₃, J(NO₂), and temperature data, using thesteady state assumption Median ozone production was 605 pptv/h at PokerFlat, and one order of magnitude smaller at Svalbard during the daytime.Only at Poker Flat could a direct influence on the diurnal ozone cycle beobserved from in-situ production. These results imply that PAN decompositionis a major source of NO_x in the high latitude troposphere, andthat this contributes to the observed spring maximum in surface ozone.     

Free Radicals and Fast Photochemistry during BERLIOZ

The free radicals OH, HO₂, RO₂, and NO₃ are known to be the driving force for most chemical processes in the atmosphere. Since the low concentration of the above radicals makes measurements particularly difficult, only relatively few direct measurements of free radical concentrations have been reported to date.We present a comprehensive set of simultaneous radical measurements performed by Laser Induced Fluorescence (LIF), Matrix Isolation –Electron spin Resonance (MI-ESR), Peroxy Radical Chemical Amplification (PERCA), and Differential Optical Absorption Spectroscopy (DOAS) during the BERLIner OZonexperiment (BERLIOZ) during July and August of 1998 near Berlin, Germany. Most of the above radical species were measured by more than one technique and an intercomparison gave good agreement. This data set offered the possibility to study and quantify the role of each radical at a rural, semi-polluted site in the continental boundary layer and to investigate interconnections and dependencies among these free radicals.In general (box) modelled diurnal profiles of the different radicals reproduced the measurements quite well, however measured absolute levels are frequently lower than model predictions. These discrepancies point to disturbing deficiencies in our understanding of the chemical system in urban air masses.In addition considerable night-time peroxy radical production related to VOC reactions with NO₃ and O₃ could be quantified.     

The photochemistry of synoptic-scale ozone synthesis: Implications for the global tropospheric ozone budget

The oxidation of nonmethane hydrocarbons represents a source of tropospheric ozone that is primarily confined to the boundary layers of several highly industrialized regions. (Each region has an area greater than one million km²). Using a photochemical model, the global tropospheric ozone budget is reexamined by including the in-situ production from these localized regimes. The results from these calculations suggest that the net source due to this photochemistry, which takes place on the synoptic scale, is approximately as large as the amount calculated for global scale photochemical processes which consider only the oxidation of methane and carbon monoxide. Such a finding may have a considerable impact on our understanding of the tropospheric ozone budget. The model results for ozone show reasonable agreement with the climatological summer distribution of ozone and the oxides of nitrogen at the surface and with the vertical distribution of ozone and nonmethane hydrocarbons obtained during a 1980 field program.     

The Balloon Intercomparison Campaigns an introduction and overview

The Balloon Intercomparison Campaigns of 1982 and 1983 compared balloon-borne sensors of HCl, HNO3, NO2, NO and O3, and measured many other stratospheric constituents. Most sensors were remote rather than in-situ. In the 1982 campaign, three large gondolas were successfully launched from Palestine, Texas on the same day; in the 1983 campaign, four gondolas were launched within 3 days. Accompanying papers describe the results of these successful intercomparisons.     

Influence of thin liquid films on polar ice chemistry: Implications for Earth and planetary science

The polar snowpack (and sea-ice) plays a major role in affecting overlying boundary layer chemistry and has only recently come to light. Furthermore, the understanding of this system and its importance is steadily growing. Investigations done thus far, nonetheless, examined the subsets of the polar environment as an uncoupled system. Analogous to some materials, the surface of snow/ice exhibits thin liquid layers (e.g., the quasi-liquid layer (QLL) and brine layer (BL)). This paper gives an overview of thin liquid films and illustrations of their function in Earth science. The impact of such films in polar science (i.e., polar snowpack photochemistry) is discussed within the context of how field data has been elucidated through laboratory data and modeling techniques. Specifically, what laboratory and modeling investigations have revealed about the effect of thin liquid layers on constraining field observations and, more importantly, the physicochemical mechanisms that govern the behavior of trace gases within the snowpack (and sea-ice) and how they are released from the polar snowpack. Current and future impacts of these findings are discussed, along with putative implications of the effect of thin liquid films in planetary science.     

海洋石油光化学降解的研究

石油进入海水会发生各种物理、化学变化,以往的研究已证明光化学氧化在石油及其精炼产品风化过程中具有重要意义.光化学氧化机理主要在于接受日光照射的能量,以不同的方式与溶解氧结合,从而最终降解石油烃.生成的光氧化产物一般为羧酸、醇、醚、羰基化合物等几类,还有一些产物尚不能确定其结构.光氧化产物仍然存在毒性,对海洋生物等十分有害.在动力学方面,针对其某一组分已证实为一级反应动力学行为,并定量地得出了速率常数.光降解速率会受到光照条件、溶解氧、金属离子等因素的影响.目前的研究表明,对石油光化学进行深入探讨具有较高的研究价值和现实意义.     

The Role of In Situ Photochemistry in the Control of Ozone during Spring at the Jungfraujoch (3,580 m asl) – Comparison of Model Results with Measurements

A photochemical box model has been used to model themeasured diurnal ozone cycle in spring at Jungfraujochin the Swiss Alps. The comparison of the modelleddiurnal ozone cycle with the mean measured diurnalozone cycle in spring, over the period 1988–1996,shows a good agreement both with regard to the shapeand amplitude. Ozone concentrations increase duringthe daytime and reach a maximum at about 16:00–17:00(GMT) in both the modelled and the mean observed ozonecycle, indicative of net ozone production during thedaytime at Jungfraujoch in spring. The agreement isbetter when the modelled ozone cycle is compared withthe mean measured diurnal cycle (1988–1996) filteredfor north-westerly winds >5 m/s (representative ofregional background conditions at Jungfraujoch). Inaddition to ozone, the modelled diurnal cycle of[HO₂] + [CH₃O₂] also shows rather goodagreement with the mean diurnal cycle of the peroxyradicals measured during FREETEX '96, a FREETropopsheric Experiment at Jungfraujoch in April/May1996. Furthermore, this mean diurnal cycle of the sumof the peroxy radicals measured during FREETEX '96 isused to calculate, using steady-state expressions, therespective diurnal cycle of the OH radical. Thecomparison of the OH diurnal cycle, calculated fromthe peroxy radical measurements during FREETEX '96,with the modelled one, reveals also good agreement.The net ozone production rate during the day-time is0.27 ppbv h^-1 from the model, and 0.13 ppbvh^-1 from the observations during FREETEX '96. Theobservations and model results both suggest that thediurnal ozone variation in spring at Jungfraujoch isprimarily of photochemical origin. Furthermore, theobserved and modelled positive net ozone productionrates imply that tropospheric in situphotochemistry contributes significantly to theobserved high spring ozone values in the observedbroad spring-summer ozone maximum at Jungfraujoch.     

Measurement of Particle-Bound Reactive Oxygen Species in Rubidoux Aerosols

The diurnal variations in the concentrations of reactive oxygen species (ROS) in various size fractions were determined for ambient particles in Rubidoux, CA. Sampling of particles was conducted at 3 h intervals using a cascade impactor. The collected particles were reacted with dichlorofluorescin (DCFH), a non-fluorescent probe that fluoresces when oxidized. The factors affecting the diurnal variation in ROS concentration were also investigated with special emphasis on the relation between ROS concentration and the intensity of photochemical reactions where the ozone concentration was taken as an index. The intensity of photochemical reactions was found to be a moderate factor affecting the daytime ROS concentration. The concentration of ROS was found to be higher on the smaller particles of the ambient aerosol. An erratum to this article is available .