首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Previous zero-dimensional photochemical calculations indicate that multiple tropospheric steady states may exist, in which different NO x (NO+NO2) levels could be supported by the same source of NO x . To investigate this possibility more closely, a one-dimensional photochemical model has been used to estimate the rate of removal of atmospheric NO x compounds at different NO x levels. At low NO x levels NO x is photochemically converted to HNO3, which is removed by either wet or dry deposition. At high NO x levels formation of HNO3 is inhibited, and NO x is removed by a variety of other processes, including rainout of N2O4 and N2O5, surface deposition of NO and NO2, and direct dissolution of NO and NO2 in rainwater. Multiple steady states are possible if surface deposition of NO x is relatively inefficient. The NO x source required to trigger high atmospheric NO x levels is approximately 10 to 15 times the present global emission rate-less than half the source strength predicted by the zero-dimensional model. NO x mixing ratios in excess of 10-7 would cause severe damage to the ozone layer and could result in either a climatic warming or cooling, depending upon the amount of NO2 present.  相似文献   

2.
The chemical reactivity of NO and NO2 is so rapid that their fluxes and concentrations can be considerably modified from that expected for conserved variables in the atmospheric surface layer, even as low as a meter above the surface. Fitzjarrald and Lenschow (1983) have calculated flux and mean concentration profiles for NO, NO2 and O3 in the surface layer using numerical techniques. However, their solutions do not approach the photostationary state at large heights. Here we solve a simpler set of equations analytically (i.e. we assume a constant O3 concentration and neutral hydrodynamic stability), and are able to show how the flux profiles behave at large heights assuming that the concentrations approach their photostationary values. We find, for example, that at large heights the ratio of the flux of NO to that of NO2 is equal to the ratio of their concentrations. These results are relevant to estimating surface fluxes of NO and NO2, and are most applicable to nonurban environments where NO and NO2 concentrations are usually much less than O3 concentration.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

3.
Chemical amplification, CA, a method commonly used for the detection of peroxy radicals, HO2 and RO2, was found to be sensitive towards ClOx (Cl+ClO+OClO) as well. ClOx is reduced by NO to Cl atoms which react with carbon monoxide in the presence of O2. The reaction sequence thus initiated oxidizes CO to CO2 and NO to NO2, with a chain length of 300 ± 60. This allows the atmospheric ClOx content to be measured under ambient conditions with a detection limit of better than 1 ppt. In parallel peroxy radicals are indicated with a chain length of 160 ± 15. Chemical amplification is not specific and does not indicate which radical chain it is seeing. Identification relies solely on plausibility. During the ARCtic Tropospheric Ozone Chemistry (ARCTOC) campaign in spring 1995 and 1996 the CA technique was used at Ny-Ålesund. ClOx at mixing ratios of up to 2 ppt were found in the boundary layer under certain conditions. The low concentrations of ClOx indicate that the arctic boundary ozone depletion is mainly driven by bromine.  相似文献   

4.
Eddy correlation measurements of NO vertical flux were made periodically from October 1983 through June 1984 at a height of eight meters above grass in northeastern Illinois, U.S.A. From 207 data points, each representing a 25 min average, 19 daytime cases and 8 nighttime cases were selected on the basis of steady, nonadvective atmospheric conditions. Each case was represented by a set of data constituting a 3 to 5 hr average. Concentrations of O3, NO, and NO y (from which NO2 was inferred) and local atmospheric and surface conditions also were measured, to provide the information necessary to assess the relative importance of surface deposition, surface emission, and air chemistry on the observed NO flux. On the basis of a linear regression analysis applied with independent variables representing physical, chemical, and biological processes, surface uptake of NO was very small for data primarily collected in the daytime during spring, and measured deposition velocities at a height of 8 m were very small, much smaller than expected for NO2. For the same time period, the surface emission rates of elemental nitrogen in NO were in the range of 1.4 to 4.2 ng m-2 s-1 for moist, unsaturated soils at temperatures near 15° C. These emissions were partially masked in the measured fluxes by rapid in-air chemical reactions involving O3 and NO2. The effects of rapid in-air chemical reactions involving O3 were to decrease the (upward) flux of NO with height. While the information collected at night was too limited to strongly support hypotheses concerning emissions and deposition, a pathway for NO production by reactions involving NO3 and related compounds was indicated. For daytime conditions, this production pathway is not evident, probably because of the relatively strong effects of photochemical reactions involving NO, NO2, and O3.Formerly with the Chemical Technology Division of Argonne National Laboratory and currently affiliated with Bio-Rad Laboratories, Digilab Division, Minneapolis, MN, U.S.A.  相似文献   

5.
The kinetics of the reaction of NO2 with O3 have been investigated at 296 K, using UV absorption spectroscopy to monitor decay of NO2 or O3 and infrared laser absorption spectroscopy to monitor formation of the reaction product N2O5. The results both for the rate coefficient at 296 K (k 1=3.5×10-17 cm3 molecule-1 s-1) and the reaction stoichiometry (NO2/O3=1.85±0.09) are in good agreement with previous studies, confirming that the two step mechanism involving formation of symmetrical NO3 as an intermediate is predominant.% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaeOtaiaab+% eadaWgaaWcbaGaaeOmaaqabaGccqGHRaWkcaqGpbWaaSbaaSqaaiaa% bodaaeqaaOWaa4ajaSqaaaqabOGaayPKHaGaaeOtaiaab+eadaWgaa% WcbaGaae4maaqabaGccqGHRaWkcaqGpbWaaSbaaSqaaiaabkdaaeqa% aaaa!41D7!\[{\text{NO}}_{\text{2}} + {\text{O}}_{\text{3}} \xrightarrow{{}}{\text{NO}}_{\text{3}} + {\text{O}}_{\text{2}} \]% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaeOtaiaab+% eadaWgaaWcbaGaae4maaqabaGccqGHRaWkcaqGobGaae4tamaaBaaa% leaacaqGYaaabeaakiabgUcaRiaab2eadaGdKaWcbaaabeGccaGLsg% cacaqGobWaaSbaaSqaaiaabkdaaeqaaOGaae4tamaaBaaaleaacaqG% 1aaabeaakiabgUcaRiaab2eaaaa!4464!\[{\text{NO}}_{\text{3}} + {\text{NO}}_{\text{2}} + {\text{M}}\xrightarrow{{}}{\text{N}}_{\text{2}} {\text{O}}_{\text{5}} + {\text{M}}\]A possible minor role for the unsymmetrical ONOO species is suggested to account for the lower-than-expected stoichiometry factor. The importance of this reaction in the oxidation of atmospheric NO2 is discussed.  相似文献   

6.
The response of tropospheric ozone to a change in solar UV penetration due to perturbation on column ozone depends critically on the tropospheric NO x (NO+NO2) concentration. At high NO x or a polluted area where there is net ozone production, a decrease in column ozone will increase the solar UV penetration to the troposphere and thus increase the tropospheric ozone concentration. However, the opposite will occur, for example, at a remote oceanic area where NO x is so low that there is net ozone destruction. This finding may have important implication on the interpretation of the long term trend of tropospheric ozone. A change in column ozone will also induce change in tropospheric OH, HO2, and H2O2 concentrations which are major oxidants in the troposphere. Thus, the oxidation capacity and, in turn, the abundances of many reduced gases will be perturbed. Our model calculations show that the change in OH, HO2, and H2O2 concentrations are essentially independent of the NO x concentration.  相似文献   

7.
We use a global atmospheric chemistry transport model to study the possible influence of aqueous phase reactions of peroxynitric acid (HNO4) on the concentrations and budgets of NOx, SOx, O3 and H2O2. Laboratory studies have shown that the aqueous reaction of HNO4aq withHSO– 3aq, and the uni-molecular decomposition of the NO4 – anion to form NO2 – (nitrite) occur on a time scale of about a second. Despite a substantial contribution of the reaction of HSO– 3aq with HNO4aq to the overall in-cloud conversion of SO2 to SO4 2–, a simultaneous decrease of other oxidants (most notably H2O2) more than compensated the increase in SO4 2– production. The strongest influence of heterogeneous HNO4 chemistry was found in the boundary layer, where calculated monthly average ozone concentrations were reduced between 2% to 10% andchanges of H2O2 between –20% to +10%compared to a simulation which ignores this reaction. Furthermore, SO2 was increased by 10% to 20% and SO4 2–depleted by up to 10%. Since the resolution of our global model does not enable a detailed comparison with measurements in polluted regions, it is not possible to verify whether considering heterogeneous HNO4 reactions results in a substantial improvement of atmospheric chemistry transport models. However, the conversion of HNO4 in the aqueous phase seems to be efficient enough to warrant further laboratory investigations and more detailed model studies on this topic.  相似文献   

8.
A catalytic reduction technique for the measurement of total reactive odd-nitrogen NO y in the atmosphere was evaluated in laboratory and field tests. NO y component species include NO, NO2, NO3, HNO3, N2O5, CH3COO2NO2(PAN), and particulate nitrate. The technique utilizes the reduction of the higher oxides to NO in reaction with CO on a metal catalyst and the subsequent detection of NO by chemiluminescence produced in reaction with O3. The efficiency and linearity of the conversion of the principal NO y species were examined for mixing ratios in the range of 0.1 to 100 parts per billion by volume (ppbv). Results of tests with Au, Ni, and stainless steel as the catalyst in the temperature range of 25–500°C showed Au to be the preferred catalyst. NH3, HCN, N2O, CH4, and various chlorine and sulfur compounds were checked as possible sources of NO y interference with the Au catalyst. The effects of pressure, O3, and H2O on NO y conversion were also examined. The results of the checks and tests in the laboratory showed the technique to be suitable for initial NO y measurements in the atmosphere. The technique was subsequently tested in ambient air at a remote ground-based field site located near Niwot Ridge, Colorado. The results of conversion and inlet tests made in the field and a summary of the NO y data are included in the discussion.  相似文献   

9.
Upto 13% of -pinene and 3-carene had reacted after 213 s in this dark experimental set-up, where O3, NO and NO2 were mixed with terpenes at different relative humidities (RHs). The different experiments were planned according to an experimental design, where O3, NO2, NO, RH and reaction time were varied between high and low settings (25 and 75 ppb, 15 and 42%, 44 and 213 s). An increased amount of -pinene and 3-carene reacted in the chamber was observed, when the level of O3, NO and reaction time was increased and RH was decreased. In the study, it was found that different interactions affected the amount of terpene reacted as well. These interactions were between O3 and NO, O3 and reaction time, NO and RH, and between NO and reaction time.  相似文献   

10.
A multi-layer deposited ice film was prepared through water vapor deposition on a Ni plate in a vacuum chamber at 90 K, and was used as it was or after annealing at 140 K. NO2 was adsorbed as N2O4 approximately 90 K on the ice film prepared as above, and irradiated by 193 nm excimer laser light. The time-of-flight (TOF) spectra of the desorbed species, i.e., NO2, NO, O2 and O, were measured by a quadrupole mass spectrometer. The photochemical process obeyed an one-photon process. The relative yields of the products and their TOF spectra were dependent on the preparation condition of the ice film and also varied with the continuation of the laser irradiation. From the ice film annealed at 140 K, NO2, NO and O2 were desorbed with an approximate ratio of 1:1:0.01. From the non-annealed film, the relative yield of NO2 was much smaller than that of NO. The TOF spectrum of NO from the non-annealed ice film consisted of distinctly different two components corresponding to the 1700 and 100 K translational temperature, respectively. The fast component was lost when additional ice was deposited on the adsorbed N2O4. NO was supposed to be a predissociation product from the electronically excited NO2 prepared through the photodissociation of N2O4.  相似文献   

11.
This paper reports the results of a study on the transformation of benzene in the presence of solid nitrate salts (NaNO3, NH4NO3) under irradiation in a gas-solid photoreactor. Sodium and ammonium nitrate have been chosen as representative of the composition of atmospheric particulate, benzene as a model aromatic molecule. The purpose is to simulate the transformations that aromatic compounds undergo on the surface of dispersed particles in the atmosphere. Irradiation of sodium nitrate causes hydroxylation and nitration of benzene, yielding phenol and nitrobenzene. This is most likely due to the generation of •OH and •NO2 radicals upon nitrate photolysis, with •OH + O2 leading to the formation of phenol and •OH + •NO2 yielding nitrobenzene. The percentage of oxygen in the reaction environment influences the transformation pathways, with phenol formation being favoured and nitrobenzene formation depressed by high O2 concentration. In the presence of hematite (α-Fe2O3, another component of atmospheric particulate) very relevant formation of nitrobenzene takes place even with 21% oxygen (simulated air), indicating that the interaction between hematite and nitrate can lead to the formation of aromatic nitroderivatives on the surface of atmospheric particulate. The effect of hematite is possibly due to protonation of peroxynitrite, formed upon nitrate photoisomerisation, to peroxynitrous acid, a powerful nitrating agent. A similar effect leads to relevant formation of nitrobenzene under atmospheric conditions upon irradiation of the acid salt ammonium nitrate.  相似文献   

12.
Generally, it is assumed that UV-light, high temperature or reactive molecules like O3 and OH are needed to activate gas reactions in air. In consequence, the catalytic activity on natural materials such as sand and soil on the earth's surface is assumed to be insignificant. We have measured O2-dissociation rates on natural quartz sand at 40˚C and compared these with O2-dissociation rates near 500˚C on materials with well-known catalytic activity. In terms of probabilities for dissociation of impinging O2-molecules the measured rates are in the 10−12–10−4 range. We have also measured dissociation rates of H2 and N2, water-formation from H2 and O2 mixtures, exchange of N between N2, NO x and a breakdown of HNO3, NO2 and CH4 on natural quartz sand at 40˚C. The measured rates together with an effective global land area have been used to estimate the impact of thermodynamically driven reactions on the earth's surface on the global atmospheric budgets of H2, NO2 and CH4. The experimental data on natural quartz sand together with data from equilibrium calculations of air suggest that an expected increase in anthropogenic supply of air pollutants, such as NO x or other “reactive” nitrogen compounds, hydrogen and methane, will be counter-acted by catalysis on the earth's surface. On the other hand, at Polar Regions and boreal forests where the “reactive” nitrogen concentration is below equilibrium, the same catalytic effect activates formation of bio-available nitrogen compounds from N2, O2 and H2O.  相似文献   

13.
We have developed a simple, steady-state, one-dimensional second-order closure model to obtain continuous profiles of turbulent fluxes and mean concentrations of non-conserved scalars in a convective boundary layer without shear. As a basic tool we first set up a model for conserved species with standard parameterizations. This leads to formulations for profiles of the turbulent diffusivity and the ratio of temperature-scalar covariance to the flux of the passive scalar. The model is then extended to solving, in terms of profiles of mean concentrations and fluxes, the NO x –O3 triad problem. The chemical reactions involve one first-order reaction, the destruction of NO2 with decay time τ, and one second-order reaction, the destruction of NO and O3 with the reaction constant k. Since the fluxes of the sum concentrations of NO x = NO + NO2 and O3 + NO2 turn out to be constant throughout the boundary layer, the problem reduces to solving two differential equations for the concentration and the flux of NO2. The boundary conditions are the three surface fluxes and the fluxes at the top of the boundary layer, the last obtained from the entrainment velocity, and the concentration differences between the free troposphere and the top of the boundary layer. The equations are solved in a dimensionless form by using 1/(kτ) as the concentration unit, the depth h of the boundary layer as the length unit, the convective velocity scale w * as the velocity unit, and the surface temperature flux divided by w * as the temperature unit. Special care has been devoted to the inclusion of the scalar–scalar covariance between the concentrations of O3 and NO. Sample calculations show that the fluxes of the reactive species deviate significantly from those of non-reactive species. Further, the diffusivities, defined by minus the flux divided by the concentration gradient may become negative for reactive species in contrast to those of non-reactive species, which in the present model are never negative.  相似文献   

14.
北京秋季一次典型大气污染过程多站点分析   总被引：3，自引：1，他引：2  
多站点多种大气污染物的同步在线观测对深入剖析大气污染的成因和演变机制有重要意义。以龙潭湖、北京325 m塔、双清路和阳坊4监测站点实时NOx、SO2、O3、PM2.5和PM10浓度观测数据为基础,介绍了北京地区2010年10月3～11日发生的一次典型污染过程。不同污染物在污染过程中变化特征不一致,表现为NOx、SO2、O3浓度有明显日变化,而PM浓度升高后一直维持在高值,日变化幅度很小。通过分析不同站点、相同污染物之间的相关性和变异系数发现,4站点间一次污染物NO和SO2空间浓度差别大,变异系数分别为77%和70%,相关系数低于0.44;而二次污染物NO2、PM2.5、O3空间浓度差别较小,变异系数分别为34%、36%和29%,相关系数均超过0.54。结合中尺度气象模式研究发现,该污染过程中,850 hPa高空持续的西南暖平流造成华北地区显著平流逆温,与近地层辐射逆温共同作用,使北京地区混合层高度维持在1200 m以下。低混合层高度和低风速限制了大气垂直和水平扩散,造成北京地区近地层污染物累积,形成重度污染。  相似文献   

15.
The exchange of NO3 radicals with the aqueous-phase was investigated at room temperature (293 K) in a series of wetted denuders. From these experiments, the uptake coefficient of NO3 was determined on 0.1 M NaCl solutions and was found to be (NO3) 2 × 10-3 in good agreement with recent studies. The Henry coefficient of NO3 was estimated to be KH(NO3) = 1.8 M · atm-1, with a (2) uncertainty of ±3 M · atm-1. From the upper limit for the Henry coefficient (KH = 5 M · atm-1) and available thermodynamic data, the redox potential of dissolved NO3/NO 3 – is estimated to be in the range of 2.3 to 2.5 V. This range is at the lower boundary of earlier estimates. The results are discussed in the light of a recent publication. Based on our data and a model of the transport and chemistry in the liquid film, an upper limit is derived for the product of the Henry coefficient KH and the rate coefficient k 10 of the potential reaction NO3 + H2O HNO3 + OH. For KH = 0.6 M · atm-1, we find k 10 < 0.05 s-1 · atm-1, i.e., about 100 times smaller than what was suggested by Rudich and co-workers. Because of its small solubility, heterogeneous removal of NO3 is only important under conditions where the dissolved NO3 is removed quickly from equilibrium, for example by reactions with Cl– or HSO 3 – ions in the liquid-phase. Otherwise, heterogenous removal should mainly proceed via N2O5.  相似文献   

16.
The rate of formation of N2O via the thermochemically favourable reaction of NO3(A2E) with N2, which would represent an additional source of stratospheric N2O and therefore NOx, has been investigated. Mixtures of NO2+O3 in synthetic air were photolysed at 662 nm. No evidence was found for the production of N2O via this pathway, the upper limit for the quantum yield of nitrous oxide formation being % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXafv3ySLgzGmvETj2BSbqefm0B1jxALjhiov2D% aebbfv3ySLgzGueE0jxyaibaiiYdd9qrFfea0dXdf9vqai-hEir8Ve% ea0de9qq-hbrpepeea0db9q8as0-LqLs-Jirpepeea0-as0Fb9pgea% 0lrP0xe9Fve9Fve9qapdbaqaaeGacaGaaiaabeqaamaabaabcaGcba% GaeqOXdy2aaSbaaSqaamaaBaaameaadaWgaaqaamaaBaaabaGaamOt% amaaBaaabaGaaGOmaiaad+eaaeqaaaqabaaabeaaaeqaaaWcbeaatu% uDJXwAK1uy0HMmaeHbfv3ySLgzG0uy0HgiuD3BaGqbaOGae8hzIqOa% aGimaiaac6cacaaI2aGaaiyjaaaa!4E60!\[\phi _{_{_{_{N_{2O} } } } } \le 0.6\% \]. However, a dark conversion of NOx to N2O was observed and is attributed tentatively to a heterogeneous reaction on the wall of the reaction vessel. This process, although most likely to be insignificant in the atmosphere, needs to be taken into consideration in laboratory investigations or field studies of N2O emission or deposition.  相似文献   

17.
In view of the uncertainty of the origin of the secular increase of N2O, we studied heterogeneous processes that contribute to formation of N2O in an environment that comes as close as possible to exhaust conditions containing NO and SO2, among other constituents. The N2O formation was followed using electron capture gas chromatography (ECD-GC). The other reactants and intermediates (SO2, NO, NO2 and HONO) were monitored using gas phase UV-VIS absorption spectroscopy. Experiments were conducted at 298 and 368 K as well as at dry and high humidity (approaching 100% rh) conditions. There is a significant heterogeneous rate of N 2 O formation at conditions that mimic an exhaust plume from combustion processes.The simultaneous presence of NO, SO2, O2 in the gas phase and condensed phase water, either in the bulk liquid or adsorbed state has been confirmed to be necessary for the production of significant levels of N2O. The stoichiometry of the overall reaction is: 2 NO+SO2+H2O N2O+H2SO4. The maximum rate of N2O formation occurred at the beginning of the reaction and scales with the surface area of the condensed phase and is independent of its volume. A significant rate of N2O formation at 368 K at 100% rh was also observed in the absence of a bulk substrate. The diffusion of both gas and liquid phase reactants is not rate limiting as the reaction kenetics is dominated by the rate ofN2O formation under the experimental conditions used in this work. The simultaneous presence of high humidity (90–100% rh at 368 K) and bulk condensed phase results in the maximum rate and final yield of N2O approaching 60% and 100% conversion after one hour in the presence of amorphous carbon and fly-ash, respectively.Work performed in partial fulfillment of the requirements of Dr ès Sciences at EPFL.  相似文献   

18.
Improvements of the matrix isolation/electron spin resonance technique for the measurement of NO2, NO3, and RO2 radicals in the atmosphere are described. The use of D2O instead of H2O as the matrix yields a better spectral resolution and, as a consequence, larger a signal-to-noise ratio as well as better identification of the different species. Reference spectra of the different radicals in H2O and D2O matrices are compared. While a large degree of correlation exists amongst the spectra of the different (unsubstituted and substituted) alkylperoxy radicals, the spectra of HO2, CH3C(O)O2, and NO3 show significant differences that allow their distinction in atmospheric samples.A numerical procedure for the analysis of the composite ESR spectra obtained from atmospheric samples was developed. Subtraction of the dominant NO2 signal is performed by matching a reference NO2 spectrum with respect to amplitude, spectral position, and line width to the sample spectrum. The manipulations are performed with the virtually noise-free reference spectrum and are based on physical information. The residual spectrum is then analyzed for RO2 (and/or NO3) by simultaneously fitting up to six different reference spectra.The method was applied to laboratory samples as well as to atmospheric samples in order to demonstrate the ability of retrieving small amounts of HO2 in the presence of large amounts of NO2 and other peroxy radicals. The new algorithm allowed, for the first time, the identification of the HO2 and CH3C(O)O2 radical in tropospheric air at concentrations ranging up to 40 ppt.  相似文献   

19.
The average dispersion of a plume in the atmospheric boundary layer is strongly influenced by atmospheric turbulence. Atmospheric turbulence determines also concentration fluctuations due to turbulent meandering by large scale turbulent eddies and in-plume fluctuations, due to smaller scale eddies. Conversion of NO to NO2 in a plume is influenced by micro-scale mixing, due to the concentration fluctuation correlation % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaa0aaaeaaca% qGobGaae4tamaaCaaaleqabaGaaeymaaaakiaab+eadaqhaaWcbaGa% ae4maaqaaiaabgdaaaaaaaaa!3AF4!\[\overline {{\rm{NO}}^{\rm{1}} {\rm{O}}_{\rm{3}}^{\rm{1}} } \] and macro-scale mixing, the mixing in of ambient air containing O3 into the plume.The study of turbulent meandering, in-plume fluctuations, microscale and macro-scale mixing will contribute to a better understanding of concentration fluctuations in general.  相似文献   

20.
Summary The atmospheric concentrations of several primary species: NO, NO2, NOx, CO, SO2, reactive hydrocarbons (ROG) and other 15 atmospheric and meteorological variables have been measured at several locations in Córdoba city, Argentina since June 1995. The measurements are carried out using two mobile stations to cover several important areas of Córdoba. The objective of this work is to estimate the effects of meteorology and urban structure on the air quality levels for this city using simple statistics. We analyze the correlation between primary pollutants (CO and NOx) and site locations of the air quality monitoring stations (AQMS) during the whole 1995 field campaign. In this study we take the measured data for primary pollutants and group them by location and time of the year. The results of this work may be useful to forecast air pollution episodes. Also we can get indirect information about emissions and maybe identify source characteristics. Once the influences of topography, meteorology, and land use will be fully characterized, the existing monitoring data will be used to do air quality modeling analysis and to select monitoring locations. The use of mobile stations instead of stationary ones at this stage is justified because of limited funding. Therefore, it is a valid option to decide in the future the additional instrumentation required to characterize completely the atmospheric urban area.With 5 Figures  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号