Trend of Ozone in the free troposphere above Europe

Summary Ozone observations were made one century ago by the Sch?nbein technique at meteorological observatories in the alpine region. Within the intrinsic limitations of the technique, historical readings have been converted to present-time concentrations (p.p.b.v.). The evaluated ozone level in the free troposphere (17 p.p.b.v.) was twice as large as at the surface; comparable values were obtained by chemical and spectroscopic technique in the first half of our century. Furthermore, the reconstructed ozone trend in the free troposphere shows a sharp increase after the ’50s, as already observed at the surface at midlatitudes of the northern hemisphere.     

Stratospheric ozone descent into the troposphere: Case studies

Summary The penetration of stratospheric air into the troposphere, revealed by high ozone concentrations measured both by an aircraft (Electra) and at a mountain station (Mt. Cimone) during a lee cyclogenesis event (April 24–25, 1982), is investigated. A detailed analysis of the meteorological fields and the application of the isentropic-trajectory method allowed us to reveal the dynamical processes responsible for the ozone transport into the troposphere. We show that the two episodes of high ozone concentrations have to be attributed to the evolution of two distinct upper vortexes, only one of which was associated with surface lee cyclone development. Paper presented at the 1° Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 19–22, 1984, Rome.     

紫外/臭氧法PDMS表面亲水改性机理研究

紫外/臭氧改性法是一种操作简单、成本低廉的PDMS表面亲水改性方法。采用该方法对PDMS表面进行亲水改性,利用接触角测量仪对改性效果进行评价,并与PDMS无臭氧紫外法进行了比较。测试表明PDMS表面经紫外/臭氧法处理12小时后,表面接触角达到60°左右,在空气中放置两周后仍保持较好的亲水性。其改性机理可以通过多种表征手段进行分析。红外光谱测试可以看出,PDMS在经过紫外/臭氧改性后,其表面官能团变化明显,随改性时间延长,疏水基团—CH₃逐渐减少,亲水基团Si—OH和—OH逐步增加,二氧化硅典型红外光谱峰也同时出现。通过扫描电镜和能谱测试可以看出,PDMS表面经过改性产生了二氧化硅为主的硅的氧化物。综合上述结果,紫外/臭氧处理法能够使PDMS表面亲水基团增多,同时生成类玻璃态SiO_x薄层,既改善了PDMS表面的亲水性,又阻止了PDMS表面疏水性的完全恢复,亲水性可以长时间保持。     

On the ozone hole in October

Summary Concentration (by number) of magnetic spheroids recorded in 1967, 1969, and 1971 in the Northern and Southern Hemisphere at different longitudes and latitudes during the month of October may be associated with the formation of the ozone hole in the ozone layer during September and the first part of October. The flux of magnetic spheroids was found to increase from the North toward the South thus providing sufficient concentrations of particles around the South Pole capable of reacting chemically with ozone. The surfaces of magnetic spheroids consisted of FeO_1.3 and sub-surfaces of FeO_1.1 indicating that oxidation proceeded from the outside inward. The ozone hole in October in the Southern Hemisphere may be a natural phenomenon. The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

Carbon nanohorn sensor to detect ozone in water

A sensor to detect ozone in water was fabricated using coating film of single-wall carbon nanohorns (CNHs). This sensor is based on the phenomena that the electric resistance of the CNH-film decreased with the adsorption of ozone molecules thereon due to charge transfer from the surface of CNHs to O₃ molecules. The shift of the electric resistance of the CNH-film was monitored with varied concentrations of aqueous ozone at several temperatures. The shift of the electric resistance of the CNH-film was correlated with the ozone concentration and temperature based on monolayer adsorption model with consideration of activation energies of the relevant adsorption, desorption, and sensitivity of charge transfer.     

Effect of Carbon Fiber Surface Oxidation on Tribological Properties of PTFE Composite under Oil-Lubricated Conditions

Air-oxidation and ozone surface treatment of carbon fibers (CF) on tribological properties of CF reinforced polytetrafluoroethylene (PTFE) composites under oil-lubricated conditions was investigated. Experimental results revealed that ozone treated CF reinforced PTFE (CF/PTFE) composite had the lowest friction coefficient and wear under various applied loads and sliding speeds compared with untreated and air-oxidated composites. X-ray photoelectron spectroscopy (XPS) study of the carbon fiber surface showed that, after ozone treatment, oxygen concentration was obviously increased, and the amount of oxygen-containing groups on CF surfaces were increased greatly. The increase in the amount of oxygen-containing groups enhanced interfacial adhesion between CF and PTFE matrix, and large scale rubbing-off of PTFE was prevented; therefore, the tribological properties of the composite were improved.     

Influence of reactive oxygen species on the sterilization of microbes

The influence of reactive oxygen species on living cells, including various microbes, is discussed. A sterilization experiment with bacterial endospores reveals that an argon–oxygen plasma jet very effectively kills endospores of Bacillus atrophaeus (ATCC 9372), thereby indicating that oxygen radicals are the key element of sterilization. Ozone in acidic water also kills endospores of B. atrophaeus very effectively, demonstrating the capability of cleaning a large surface area contaminated by toxic biological agents. The viable microbe numbers after the contact with acidic ozone water directly correlate with increase in the ozone decay time in water after lowering the pH value of water from pH = 7 to 4 indicating that acidic ozone water is an effective means of sterilizing microbes. However, advanced cells such as fertilized eggs were not greatly influenced by the acidic ozone water. Also, both human and canine cells after treatment with the acidic ozone water prospered without showing signs of stress due to ozone in acidic water. This study suggests that antioxidant enzymes such as superoxide dismutase can be developed in the advanced cells to protect themselves from attacks by reactive oxygen species. Meanwhile, the advanced cells utilize oxygen by certain enzymes, proliferating life on earth.     

Etching-enhanced surface stress relaxation during initial ozone oxidation

Initial oxidation via ozone on the Si(1 0 0) surface is investigated by measuring surface stress and observing atomic structure via a scanning tunneling microscopy (STM). A similar investigation is also carried out for molecular oxygen and the results are compared. As a result, monotonic increase of the surface stress to the compressive stress side is obtained up to 0.33 N/m for ozone oxidation at room temperature, while molecular oxygen shows only tiny surface stress growth. From the STM observations, it is found that the difference between ozone and molecular oxygen oxidation is the existence of surface etching. As the origin of the surface stress, therefore, the reduction of the intrinsic tensile surface stress due to the reconstructed surface by the etching process is proposed.     

Effect of electronegative impurities on the generation of ozone in air

A self-consistent numerical model is used to investigate the effect of electronegative impurities on the ozone yield in a dielectric barrier discharge with a pulsed voltage supply, and the range of impurity concentrations giving a substantial (two-or threefold) increase in the ozone yield is established. Sulfur hexafluoride is considered as a representative component having strong electronegative properties. It is shown that a tiny admixture [SF₆]<0.1% can have an appreciable effect on the characteristics of an ozonator. The calculations are compared with published experimental data and given an interpretation. Zh. Tekh. Fiz. 69, 49–52 (January 1999)     

臭氧修饰(001)晶面TiO2纳米片及其光催化降解甲苯研究

本文系统研究了臭氧修饰对(001)主导晶面锐钛矿型TiO₂光催化剂降解甲苯性能的影响. 利用自行搭建的光催化VOCs降解装置对催化剂光降解甲苯的性能进行了测试. 通过多种表征手段,结合原位DRIFTS和DFT计算研究了臭氧表面修饰及甲苯吸附和降解机理. 结果表明,用臭氧进行表面修饰可以显著提高(001)主导晶面TiO₂光催化降解甲苯的性能. (001)晶面上丰富的5c-Ti不饱和配位是臭氧分子的吸附位点,其解离后形成的Ti-O键与H₂O分子结合,在表面生成大量孤立的Ti_5c-OH. Ti_5c-OH 是甲苯分子的吸附位,它的形成显著提高了对甲苯分子的吸附能力. 在光照下Ti_5c-OH与光生空穴结合能形成·OH自由基. 通过臭氧解离产生的O₂也可以与光生电子结合形成超氧自由基. 这些具有强氧化性活性自由基的形成促进了对气相甲苯的光催化降解速率.     

臭氧化法表面改性聚苯乙烯薄膜

 为增强聚苯乙烯(PS)与聚乙烯醇(PVA)之间的结合力,进而提高PS-VA双层空心微球存活率。利用臭氧化改性法在酸性介质中对聚苯乙烯薄膜进行表面改性,用红外光谱对处理后的表面进行了半定量的分析。结果表明：改性过后聚苯乙烯表面产生羟基、羰基等极性基团;接触角测试证明,处理后的表面由憎水变为亲水,并通过纳米压痕划痕法得到了处理前后PS与PVA薄膜之间的相互作用强度,臭氧化改性后PS与PVA膜间作用强度增大了40%。     

Transport of photochemical ozone along the western Adriatic shore near a petrochemical plant

Summary During the warm months, the whole area surrounding Ravenna's petrochemical plant, which is about 5 km inshore of the northern Adriatic coast (Po Valley region), is subject to photochemical reactions producing high values of ozone concentration. The transport offshore of oxidants' precursors by the land breeze, photochemical reactions and subsequent transport inshore of oxidants by the sea breeze, may cause high concentrations of ozone along the coast up until the late evening. Similar phenomena have already been observed in other coastal regions. Classifying the ozone data into days with different circulations, the following can be seen: on days with W or NW circulation, a regular diurnal variation of ozone correlated with solar radiation is found; with winds from E or SE, the ozone variations are irregular and ozone concentrations can maintain high levels ((40÷70) p.p.b.) even during the nightime. This is a report of the results of several field measurements aimed at showing the ozone production and destruction processes, as well as its recirculation mechanisms under breeze conditions. Paper presented at the 1^o Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 19–22, 1984, Rome.     

Surface modification of polyester to produce a bacterial cellulose-based vascular prosthetic device

The surface of medical grade polyesters was modified to impart hydrophilic character for attachment to bacterial synthesized cellulose to produce a vascular prosthetic device. The polyesters were treated with UV/ozone, air plasma, and nitrogen plasma for various lengths of time. The unmodified and modified surfaces were analyzed by X-ray photoelectron spectroscopy (XPS) and advancing contact angle measurements. The surfaces were then coated with bacterial produced cellulose to study adhesion properties through tensile testing (peel testing). UV/ozone and plasma treatment XPS results indicated an increase in the oxygen concentration in the form of CO(H) on the treated polyester surfaces. The treatment time to reach steady state in the case of air and nitrogen plasmas took the order of seconds, while 7 min and longer were required for UV/ozone treatment. Peel strength tests to measure adhesion of modified polyester to cellulose reached their maximum values when the CO(H) concentrations were at the highest level. It was also at this level that the contact angle measurements showed no further decrease.     

多次反射池FTIR光谱法的臭氧浓度反演及其相关性分析

同温层臭氧对人类起保护作用,地面臭氧对人类健康是有害的,能够对它进行多途径多方法监测对于了解臭氧分布和变换规律以及控制污染排放有积极作用.文章利用多次反射式怀特池傅里叶变换红外光谱仪测得傅里叶变换红外光谱,使用非线性最小二乘算法对它们进行反演,准确得到了臭氧浓度.将测得的臭氧浓度结果与开放光路紫外差分光谱仪以及热电公的...     

Estimation of the Covariance Matrix in Hierarchical Bayesian Spatio-Temporal Modeling via Dimension Expansion

Ozone concentrations are key indicators of air quality. Modeling ozone concentrations is challenging because they change both spatially and temporally with complicated structures. Missing data bring even more difficulties. One of our interests in this paper is to model ozone concentrations in a region in the presence of missing data. We propose a method without any assumptions on the correlation structure to estimate the covariance matrix through a dimension expansion method for modeling the semivariograms in nonstationary fields based on the estimations from the hierarchical Bayesian spatio-temporal modeling technique (Le and Zidek). Further, we apply an entropy criterion (Jin et al.) based on a predictive model to decide if new stations need to be added. This entropy criterion helps to solve the environmental network design problem. For demonstration, we apply the method to the ozone concentrations at 25 stations in the Pittsburgh region studied. The comparison of the proposed method and the one is provided through leave-one-out cross-validation, which shows that the proposed method is more general and applicable.     

Tropospheric ozone concentrations related to atmospheric conditions at Iza?a BAPMoN weather station, Canary Islands

Summary The 24h average concentrations of tropospheric ozone were measured in the BAPMoN (Background Atmospheric Pollution Monitoring Network) baseline station of Iza?a (Canary Islands, Spain). Concentrations were studied through a methologody based on nonparametric statistics. Three sectors of wind direction were selected and the air mass properties from these were characterized. The ozone concentration data were related to air masses in terms of aerometric elements. Highest values of ozone concentrations were found when the wind direction was from Sector I or Atlantic Sector because fair-weather conditions are associated with air flows from this sector and with long-range transport possibly from North Atlantic and Europe. Furthermore, the dependence of daily ozone concentration on some cloud types was investigated. Higher ozone concentrations were associated with high clouds having a lesser rate of depletion for solar radiation than middle and low clouds.     

Percentage contribution of ozone depleting substances on Antarctic ozone decline

A critical analysis has been made on contribution on ozone depleting substances (ODS) on the decline of ozone concentration at Antarctica. The nature of yearly variation of concentrations of ODS as well as of ozone has been presented. Possible mechanisms of ozone destruction processes catalyzed by ODS have also been offered.     

Surface control of CdSe nanocrystals by UV-exposure in air and successive thermal treatment under ultra high vacuum

Colloidal CdSe nanocrystals were synthesized through a solution process. The CdSe nanocrystals coated on Si(1 0 0) wafers were UV-exposed in either an air or argon atmosphere to distinguish the effect of generated ozone from UV-radiation at 365 nm on the removal of surface capping pyridine molecules. The pyridine on the CdSe nanocrystal's surface could be effectively removed by the ozone generated during UV-exposure with an accompanying highly oxidized surface state of the CdSe nanocrystals. For the removal of surface oxides of CdSe nanocrystals, a successive thermal treatment under ultra high vacuum (UHV) was adopted. The optical energy bandgap measured by using UV-vis absorption spectroscopy showed a red shift with treatment with an increase of annealing temperature. The electronic energy structure of UHV-annealed CdSe nanocrystals film was analyzed in situ using X-ray absorption and photoelectron spectroscopy. A great resemblance was found between the values of the optical and electron energy bandgaps of effectively surface-treated CdSe nanocrystals film after UHV-annealing at 400 °C.     

Kinetics of microplasma atmospheric ion generation correlated with discharge current

The conditions necessary for achieving a stable bipolar ion generation (in the order of 10⁶ ion/cm³) and lower ozone concentration (less than 50 ppb) using a surface discharge microplasma device (SMD) by adjusting the applied voltage and frequency were experimentally determined and investigated. Measurements of the discharge current characteristics of the SMD revealed saturation against the frequency (1.5–2.5 kHz, depending on the applied voltage). The ion and ozone concentrations both increased in step with the discharge current in the lower frequency region. The ion concentration reached equilibrium in the frequency range of 200–500 Hz, and the point of equilibrium within that range depended on the applied voltage. The ozone concentration did not reach equilibrium under our experimental conditions (ozone concentration < 100 ppb). The kinetics of the ion/ozone generation rate with a focus on the plasma reaction and recombination of bipolar ions is discussed.     

On the role of water vapour in the heat balance of the antarctic lower stratosphere

Summary A general circulation model (GCM) is used to investigate the effect on Antarctic temperatures due to changes in ozone and water vapour concentrations. It is shown that the stratospheric cooling due to the ozone secular trend is largely compensated by the H₂O loss associated with the formation of type 2 polar stratospheric clouds (PSC-2). The partial dehydration of the Antarctic lower stratosphere acts in such a way to significantly reduce the cooling associated to the O₃ depletion.