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1.
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   

2.
Summary Vertical profiles of H2O, CO2, O3, NO and NO2 were measured during the Hartheim Experiment (HartX) to develop and calibrate a multi-layer resistance model to estimate deposition and emission of the cited gaseous species. The meteorological and gas concentration data were obtained with a 30 m high telescopic mast with 7 gas inlets located at 5 m intervals and meteorological sensors at 5, 15 and 30 m above ground; a complete gas profile was obtained every 9 min 20 s. Measured profiles were influenced by several exchange processes, namely evapotranspiration, dewfall, assimilation of CO2 in the tree crowns, soil respiration, deposition of NO2 and O3 to the soil and advection of NOx from the nearby highway. Surprisingly, no decrease in O3 concentration was observed in the crown layer during daytime, probably due to the relatively low density of foliage elements and strong turbulent mixing.The advantage of measuring in-canopy profiles is that turbulent exchange coefficients need not be estimated as a prerequisite to obtaining vertical flux estimates. In recent years, flux-gradient relationships in canopies have been subject to many criticisms. If fluxes are calculated at several heights considering only the transfers between the turbulent air and the interacting surfaces at a certain height, and those fluxes are then integrated vertically in a subsequent step, then exchange estimates (deposition or emission) can be obtained independent of turbulent exchange conditions.Typical estimated deposition velocities calculated for a 3-day period are between 4 and 10 mm/s for NO2 and about 4–9 mm/s for O3 (day and night values respectively). This leads to deposition rates of about 20–40 ng N/m2s for NO2 and about 30–40 mg O3/m2 deposited daily under the conditions encountered during HartX. Sensitivity tests done with the best available and most realistic values for model parametrization have shown that sensitivity is large with respect to the soil and cuticula resistances as well as for gas-phase ozone destruction and that more research is required to describe the effectiveness of cuticula and soil in modifying sink characteristics for NO2 and O3.With 12 Figures  相似文献   

3.
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   

4.
This study describes the chemical composition of dry deposition collected at a highway traffic site in central Taiwan during daytime and nighttime periods by using a dry deposition plate (DDP) and water surface sampler (WSS). In addition, the characterization for mass and water-soluble species of total suspended particulate (TSP), both PM2.5 and PM10, was studied at the study site from August 22 to November 30, 2006. Dry deposition fluxes of ambient air particulates and inorganic species (Na+, NH4+, K+, Mg2+, Ca2+, Cl−, NO3− and SO42−) were analyzed by Ion Chromatography (DIONEX-100).Results of the particulate dry deposition fluxes and mass concentrations are higher in the water surface sampler with respect to the dry deposition plate used in this study. Statistical results also showed the average dry deposition flux of the ionic species (Na+, NH4+, K+, Cl−, NO3− and SO42−) obtained by the DDP and WSS displayed significant differences. Also, the average concentrations of Mg2+ and, Ca2+ were statistically the same at this study site.  相似文献   

5.
Field measurements of NO and NO2 emissions from soils have been performed in Finthen near Mainz (F.R.G.) and in Utrera near Seville (Spain). The applied method employed a flow box coupled with a chemiluminescent NO x detector allowing the determination of minimum flux rates of 2 g N m-2 h-1 for NO and 3 g m-2 h-1 for NO2.The NO and NO2 flux rates were found to be strongly dependent on soil surface temperatures and showed strong daily variations with maximum values during the early afternoon and minimum values during the early morning. Between the daily variation patterns of NO and NO2, there was a time lag of about 2 h which seem to be due to the different physico-chemical properties of NO and NO2. The apparent activation energy of NO emission calculated from the Arrhenius equation ranged between 44 and 103 kJ per mole. The NO and NO2 emission rates were positively correlated with soil moisture in the upper soil layer.The measurements carried out in August in Finthen clearly indicate the establishment of NO and NO2 equilibrium mixing ratios which appeared to be on the order of 20 ppbv for NO and 10 ppbv for NO2. The soil acted as a net sink for ambient air NO and NO2 mixing ratios higher than the equilibrium values and a net source for NO and NO2 mixing ratios lower than the equilibrium values. This behaviour as well as the observation of equilibrium mixing ratios clearly indicate that NO and NO2 are formed and destroyed concurrently in the soil.Average flux rates measured on bare unfertilized soils were about 10 g N m-2 h-1 for NO2 and 8 g N m-2 h-1 for NO. The NO and NO2 flux rates were significantly reduced on plant covered soil plots. In some cases, the flux rates of both gases became negative indicating that the vegetation may act as a sink for atmospheric NO and NO2.Application of mineral fertilizers increased the NO and NO2 emission rates. Highest emission rates were observed for urea followed by NH4Cl, NH4NO3 and NaNO3. The fertilizer loss rates ranged from 0.1% for NaNO3 to 5.4% for urea. Vegetation cover substantially reduced the fertilizer loss rate.The total NO x emission from soil is estimated to be 11 Tg N yr-1. This figure is an upper limit and includes the emission of 7 Tg N yr-1 from natural unfertilized soils, 2 Tg N yr-1 from fertilized soils as well as 2 Tg N yr-1 from animal excreta. Despite its speculative character, this estimation indicates that NO x emission by soil is important for tropospheric chemistry especially in remote areas where the NO x production by other sources is comparatively small.  相似文献   

6.
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   

7.
Automobile exhaust emissions are becoming increasingly serious with the drastic increase of the number of vehicles in Beijing. In order to investigate the air pollution level and characteristics in the areas near the main traffic lines in Beijing and to identify the contributions from traffic and other sources, gaseous pollutants including NOx, CO, O3, SO2, and meteorological parameters have been monitored at a monitoring site and a contrasting site in winter and summer in 2006. The volumes of vehicles on Beiyuan Road were recorded. The average concentrations of NO, NO2, NOx, CO, O3, and SO2 at the monitoring site were 0.148 mg/m3, 0.107 mg/m3, 0.333 mg/m3, 5.110 mg/m3, 0.006 mg/m3, and 0.157 mg/m3, respectively during the sampling period in winter and 0.021 mg/m3, 0.068 mg/m3, 0.101 mg/m3, 4.170 mg/m3, 0.083 mg/m3, and 0.056 mg/m3, respectively in summer. The high concentrations of CO and O3 reflect the influence of vehicles emission near the traffic lines evidently. The higher concentrations of CO, NO and O3 in summer may indicate that the characteristics of traffic pollution were more pronounced in summer. Results of regression analysis showed that in winter the concentrations of SO2 and CO were significantly positively correlated with the emission of heating boilers at night and negatively correlated with wind speed in daytime. The concentrations of NO and NOx were negatively correlated with wind speed, positively correlated with emission of heating boilers in daytime and positively correlated with traffic density at nighttime. The concentrations of NO2 were positively correlated with the emission of heating boilers in daytime and traffic density at nighttime. In summer, the air quality at the monitoring site and the contrasting site was mainly influenced by the traffic emissions.  相似文献   

8.
Data obtained in an intensive field study of the dry deposition of sulfur dioxide, ozone, and nitrogen dioxide, conducted in 1985 in central Pennsylvania, are used to illustrate the factors that must be considered to assure that high quality results are derived. In particular, the quality of the site must be such that flux measurements made above the surface are representative of surface values. For this purpose, tests involving momentum transfer and the surface energy budget are especially useful. In addition, conditions must not be changing rapidly, and the statistical uncertainty associated with flux measurement must be low. For the set of data presented here, conservative quality-assurance guidelines are used to reject potentially erroneous flux data. For ozone, most of the measured fluxes are of use in deriving surface resistances. For SO2, far fewer data points are available. For NO2, fluxes appear to lack the order of the O3 and SO2 fluxes, and do not enable surface resistances to be computed. The highest-quality SO2 and O3 data yield surface resistances in fair average agreement with model predictions for SO2, but substantially higher than predictions for O3.  相似文献   

9.
Measurements of surface ozone (O3), nitric oxide (NO), nitrogen dioxide (NO2), oxides of nitrogen (NOx=NO+NO2) and meteorological parameters have been made at Agra (North Central India, 27°10??N, 78°05??E) in post monsoon and winter season. The diurnal variation in O3 concentration shows daytime in situ photochemical production with diurnal maximum in noon hours ranging from 51 to 54 ppb in post monsoon and from 76 to 82 ppb in winter, while minimum (16?C24 ppb) during nighttime and early morning hours. Average 8-h O3 concentration varied from 12.4 to 83.9 ppb. The relationship between meteorological parameters (solar radiation intensity, temperature, relative humidity, wind speed and wind direction) and surface O3 variability was studied using principal component analysis (PCA), multiple linear regression (MLR) and correlation analysis (CA). PCA and MLR of daily mean O3 concentrations on meteorological parameters explain up to 80 % of day to day ozone variability. Correlation with meteorology is strongly emphasized on days having strong solar radiation intensity and longer sunshine time.  相似文献   

10.
Using long path UV absorption spectroscopy we have measured OH concentrations close to the earth's surface. The OH values observed at two locations in Germany during 1980 through 1983 range from 0.7×106 to 3.2×106 cm-3. Simultaneously we measured the concentrations of O3, H2O, NO, NO2, CH4, CO, and the light non methane hydrocarbons. We also determined the photolysis rates of O3 and NO2. This allows calculations of OH using a zero dimensional time depdendent model. The modelled OH concentrations significantly exceed the measured values for low NO x concentrations. It is argued that additional, so far unidentified. HO x loss reactions must be responsible for that discrepancy.  相似文献   

11.
对临安大气本底站2003-2004年冬、夏季二氧化氮(NO2)、二氧化硫(SO2)、臭氧(O3)进行了分析.结果表明:冬季NO2和SO2平均体积分数分别为19.48×10-9和35.74 x10-9,而夏季的平均体积分数分别为4.81×10-9和8.12×10-9,冬季高于夏季;O3在夏季的平均体积分数为33.55×10-9,略高于冬季的25.44×10-9;夜间NO2和SO2体积分数比白天高,并且NO2呈明显的单峰单谷型分布,O3也呈单峰型但峰值出现在白天.NO2、SO2体积分数存在着明显的“假日效应”,假日比非假日低,周五高于假日和非假日;但O3体积分数没有明显的假日效应.降水对SO2有明显的清除作用,但对NO2的清除作用不明显.与风向对比发现,夏季高体积分数的NO2、SO2都受到NW、WNW风的影响,冬季则分别受NE和SW、SSW风的影响;而O3受风向的影响较复杂,与局地光化学反应有关.  相似文献   

12.
Air pollutant emission rates and concentrations in medieval churches   总被引：1，自引：0，他引：1  
A series of indoor air quality parameters were determined in two medieval churches, in Cyprus (temperature, relative humidity, total and UV solar radiation, CO2 indoors and O3, NO, NO2 *, HNO3 *, HCl, HCOOH, CH3COOH indoors and outdoors). These data were used as input in a validated indoor air quality model to predict indoor air pollutant source strengths and species concentrations that resulted from dark or photochemical reactions. The NO and NO2 emission rates due to the burning of incense or candles were estimated. Model results revealed that heterogeneous NO formation takes place simultaneously with the heterogeneous HONO formation. Also, model application has shown that indoor NOx emissions resulted in decreased free radical concentrations, in contrast to the organic compound emissions, which increased free radical concentrations. This effect of indoor emissions on indoor radicals can partly explain the indoor enhancement/depression of indoor gaseous acid formation.  相似文献   

13.
Atmospheric hydroxyl (OH), hydroperoxy (HO2), total peroxy (HO2 and organic peroxy radicals, RO2) mixing ratios and OH reactivity (first order OH loss rate) were measured at a rural site in central Pennsylvania during May and June 2002. OH and HO2 mixing ratios were measured with laser induced fluorescence (LIF); HO2 + RO2 mixing ratios were measured with chemical ionization mass spectrometry (CIMS). The daytime maximum mixing ratios were up to 0.6 parts per trillion by volume (pptv) for OH, 30 pptv for HO2, and 45 pptv for HO2 + RO2. A parameterized RACM (Regional Atmospheric Chemistry Mechanism) box model was used to predict steady state OH, HO2 and HO2 + RO2 concentrations by constraining the model to the measured OH reactivity and previously measured volatile organic compound (VOC) distributions. The averaged model calculations are generally in good agreement with the observations. For OH, the model matched the observations for day and night, with an average observed-to-modeled ratio of 0.80. In previous studies such as PROPHET98, nighttime NO was near 0 pptv and observed nighttime OH was significantly larger than modeled OH. In this study, nighttime observed and modeled OH agree to within measurement and model uncertainties because the main source of the nighttime OH was the reaction HO2 + NO → OH + NO2, with the NO being continually emitted from the surrounding fertilized corn field. The observed-to-modeled ratio for HO2 is 1.0 on average, although daytime HO2 is underpredicted by a factor of 1.2 and nighttime HO2 is over-predicted by a factor of ∼2. The average measured and modeled HO2 + RO2 agree well during daytime, but the modeled value is about twice the measured value during nighttime. While measured HO2 + RO2 values agree with modeled values for NO mixing ratios less than a few parts per billion by volume (ppbv), it increases substantially above the expected value for NO greater than a few ppbv. This observation of the higher-than-expected HO2 + RO2 with the CIMS technique confirms the observed increase of HO2 above expected values at higher NO mixing ratios in HO2 measurements with the LIF technique. The maximum instantaneous O3 production rate calculated from HO2 and RO2 reactions with NO was as high as 10–15 ppb h−1 at midday; the total daily O3 production varied from 13 to 113 ppbv d−1 and was 48 ppbv d−1 on average during this campaign.  相似文献   

14.
The seasonal and diurnal variations of ozone mixing ratios have been observed at Niwot Ridge. Colorado. The ozone mixing ratios have been correlated with the NO x (NO+NO2) mixing ratios measured concurrently at the site. The seasonal and diurnal variations in O3 can be reasonably well understood by considering photochemistry and transport. In the winter there is no apparent systematic diurnal variation in the O3 mixing ratio because there is little diurnal change of transport and a slow photochemistry. In the summer, the O3 levels at the site are suppressed at night due to the presence of a nocturnal inversion layer that isolated ozone near the surface, where it is destroyed. Ozone is observed to increase in the summer during the day. The increases in ozone correlate with increasing NO x levels, as well as with the levels of other compounds of anthropogenic origin. We interpret this correlation as in-situ or in-transit photochemical production of ozone from these precursors that are transported to our site. The levels of ozone recorded approach 100 ppbv at NO x mixing ratios of approximately 3 ppbv. Calculations made using a simple clean tropospheric chemical model are consistent with the NO x -related trend observed for the daytime ozone mixing ratio. However, the chemistry, which does not include nonmethane hydrocarbon photochemistry, underestimates the observed O3 production.  相似文献   

15.
Measurements of atmospheric composition have been made over a remote rainforest landscape. A box model has previously been demonstrated to model the observed daytime chemistry well. However the box model is unable to explain the nocturnal measurements of relatively high [NO] and [O3], but relatively low observed [NO2]. It is shown that a one-dimensional (1-D) column model with simple O3-NOx chemistry and a simple representation of vertical transport is able to explain the observed nocturnal concentrations and predict the likely vertical profiles of these species in the nocturnal boundary layer (NBL). Concentrations of tracers carried over from the end of the night can affect the atmospheric chemistry of the following day. To ascertain the anomaly introduced by using the box model to represent the NBL, vertically-averaged NBL concentrations at the end of the night are compared between the 1-D model and the box model. It is found that, under low to medium [NOx] conditions (NOx?<?1 ppbv), a simple parametrisation can be used to modify the box model deposition velocity of ozone, in order to achieve good agreement between the box and 1-D models for these end-of-night concentrations of NOx and O3. This parametrisation would could also be used in global climate-chemistry models with limited vertical resolution near the surface. Box-model results for the following day differ substantially if this effective nocturnal deposition velocity for ozone is implemented; for instance, there is a 9% increase in the following days peak ozone concentration. However under medium to high [NOx] conditions (NOx > 1 ppbv), the effect on the chemistry due to the vertical distribution of the species means no box model can adequately represent chemistry in the NBL without modifying reaction rate coefficients.  相似文献   

16.
This paper describes laboratory experiments designed to obtain the infrared spectra of some atmospherically important radical species and related compounds. A Fourier transform spectrometer was used that was capable of yielding resolutions as great as 0.0024 cm-1, and optical paths of up to 512 m were employed. The objective of the experiments was to obtain the spectra for subsequent application to remote sounding measurements in the atmosphere.Radicals were generated by a variety of chemical reactions involving atoms or other highly reactive precursors. Spectra of the 3 band of NO3, at ca. 1500 cm-1, were obtained with up to 0.005 cm-1 resolution using the reaction between NO2 and O3 to produce the radical. The most satisfactory source of ClO was found to be the reaction between Cl and O3, and the (1-0) vibration-rotation band in the region 829–880 cm-1 was recorded at a resolution of 0.02 cm-1. We were unable to observe infrared absorption of HO2 with any of the radical sources that we tested. High-resolution survey spectra were obtained of compounds used as reactants, or formed as side-products in the radical-generating processes. These compounds included N2O5, HNO3, ClONO2, FNO2, Cl2O, HO2NO2, and probably FO2.The ability to monitor concentrations of the NO3 radical in the visible region of the spectrum as well as the concentrations of reactants and other products in the infrared region allowed us to undertake a study of the time-dependent interactions occurring when NO2 reacts with O3. The results indicate the importance of heterogeneous processes, especially when traces of water are present, and lend credence to suggestions that heterogeneous mechanisms in the NO3–N2O5–H2O system might be a viable source of HNO3 in the atmosphere.  相似文献   

17.
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   

18.
Four case studies are described, from a three-site field experiment in October/November 1991 using the Great Dun Fell flow-through reactor hill cap cloud in rural Northern England. Measurements of total odd-nitrogen nitrogen oxides (NO y ) made on either side of the hill, before and after the air flowed through the cloud, showed that 10 to 50% of the NO y , called NO z , was neither NO nor NO2. This NO z failed to exhibit a diurnal variation and was often higher after passage through cloud than before. No evidence of conversion of NO z to NO3 - in cloud was found. A simple box model of gas-phase chemistry in air before it reached the cloud, including scavenging of NO3 and N2O5 by aerosol of surface area proportional to the NO2 mixing ratio, shows that NO3 and N2O5 may build up in the boundary layer by night only if stable stratification insulates the air from emissions of NO. This may explain the lack of evidence for N2O5 forming NO3 - in cloud under well-mixed conditions in 1991, in contrast with observations under stably stratified conditions during previous experiments when evidence of N2O5 was found. Inside the cloud, some variations in the calculated total atmospheric loading of HNO2 and the cloud liquid water content were related to each other. Also, indications of conversion of NO x to NO z were found. To explain these observations, scavenging of NO x and HNO2 by cloud droplets and/or aqueous-phase oxidation of NO2 - by nitrate radicals are considered. When cloud acidity was being produced by aqueous-phase oxidation of NO x or SO2, NO3 - which had entered the cloud as aerosol particles was liberated as HNO3 vapour. When no aqueous-phase production of acidity was occurring, the reverse, conversion of scavenged HNO3 to particulate NO3 -, was observed.  相似文献   

19.
Rate constants for the gas-phase reactions of OH radicals, NO3 radicals and O3 with the C7-carbonyl compounds 4-methylenehex-5-enal [CH2=CHC(=CH2)CH2CH2CHO], (3Z)- and (3E)-4-methylhexa-3,5-dienal [CH2=CHC(CH3)=CHCH2CHO] and 4-methylcyclohex-3-en-1-one, which are products of the atmospheric degradations of myrcene, Z- and E-ocimene and terpinolene, respectively, have been measured at 296 ± 2 K and atmospheric pressure of air using relative rate methods. The rate constants obtained (in cm3 molecule–1 s–1 units) were: for 4-methylenehex-5-enal, (1.55 ± 0.15) × 10–10, (4.75 ± 0.35) × 10–13 and (1.46 ± 0.12) × 10–17 for the OH radical, NO3 radical and O3 reactions, respectively; for (3Z)-4-methylhexa-3,5-dienal: (1.61 ± 0.35) × 10–10, (2.17 ± 0.30) × 10–12, and (4.13 ± 0.81) × 10–17 for the OH radical, NO3 radical and O3 reactions, respectively; for (3E)-4-methylhexa-3,5-dienal: (2.52 ± 0.65) × 10–10, (1.75 ± 0.27) × 10–12, and (5.36 ± 0.28) × 10–17 for the OH radical, NO3 radical and O3 reactions, respectively; and for 4-methylcyclohex-3-en-1-one: (1.10 ± 0.19) × 10–10, (1.81 ± 0.35) × 10–12, and (6.98 ± 0.40) × 10–17 for the OH radical, NO3 radical and O3 reactions, respectively. These carbonyl compounds are all reactive in the troposphere, with daytime reaction with the OH radical and nighttime reaction with the NO3 radical being predicted to dominate as loss processes and with estimated lifetimes of about an hour or less.  相似文献   

20.
A modified profile method for determining the vertical deposition (or/and exhalation) fluxes of NO, NO2, ozone, and HNO3 in the atmospheric surface layer is presented. This method is based on the generally accepted micrometeorological ideas of the transfer of momentum, sensible heat and matter near the Earth's surface and the chemical reactions among these trace gases. The analysis (aerodynamic profile method) includes a detailed determination of the micrometeorological quantities (such as the friction velocity, the fluxes of sensible and latent heat, the roughness length and the zero plane displacement), and of the height-invariant fluxes of the composed chemically conservative trace gases with group concentrations c 1=[NO]+[NO2]+[HNO3], c 2=[NO2]+[O3]+3/2·[HNO3], and c 3=[NO]–[O3]–1/2·[HNO3]. The fluxes of the individual species are finally determined by the numerical solution of a system of coupled nonlinear ordinary differential equations for the concentrations of ozone and HNO3 (decoding method). The parameterization of the fluxes is based on the flux-gradient relationships in the turbulent region of the atmospheric surface layer. The model requires only the vertical profile data of wind velocity, temperature and humidity and concentrations of NO, NO2, ozone, and HNO3.The method has been applied to vertical profile data obtained at Jülich (September 1984) and collected in the BIATEX joint field experiment LOVENOX (Halvergate, U.K., September 1989).  相似文献   

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