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1.
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   

2.
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3.
Peroxyacetyl nitrate (PAN,CH3C(O)O2NO2) has been measured inthe polluted boundary layer and free troposphere by thermal conversion tonitrogen dioxide (NO2) followed by detection of thedecomposition product with a Scintrex LMA-3 NO2-luminolinstrument. Following laboratory tests of the efficiency of PAN conversionand investigations of possible interferences, the technique was evaluated atthe West Beckham TOR (Tropospheric Ozone Research) Station near the northNorfolk coast in Eastern England between September 1989 and August 1990. PANmeasured by the new technique was reasonably well correlated with PANrecorded using electron capture gas chromatography (EC/GC). PAN was alsowell correlated with ozone (O3) in the summer months. Springand autumn episodes of simultaneously high concentrations of PAN andO3 were examined in conjunction with air parcelback-trajectories and synoptic- and local-scale meteorology in a study ofthe sources of photooxidants on the east coast of England. Spring-timemeasurements of PAN made in the free troposphere in a light aircraft ataltitudes up to 3.1 km showed the presence of 0.54 and 0.26 ppbv PAN inpolar maritime and mid-latitude oceanic air masses, respectively. Thetechnique is particularly suited to airborne applications because potentialinterferences are minimised and the frequency of measurements is higher thangenerally achieved with EC/GC methods.  相似文献   

4.
Quantitative infrared measurements of ethane (C2H6) in the upper troposphere and lower stratosphere are reported. The results have been obtained from the analysis of absorption features of the 9 band at 12.2 m, which have been identified in high-resolution ballon-borne and aircraft solar absorption spectra. The ballon-borne spectral data were recorded at sunset with the 0.02 cm-1 resolution University of Denver interferometer system from a float altitude of 33.5 km near Alamogordo, New Mexico, on 23 March 1981. The aircraft spectra were recorded at sunset in July 1978 with a 0.06 cm-1 resolution interferometer aboard a jet aircraft at 12 km altitude, near 35°N, 96°W. The balloon analysis indicates the C2H6 mixing ratio decreased from 3.5 ppbv near 8.8 km to 0.91 ppbv near 12.1 km. The results are consistent with the colum value obtained from the aircraft data.  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.
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   

7.
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   

8.
In situ aircraft measurements of O3, CO,HNO3, and aerosol particles are presented,performed over the North Sea region in the summerlower stratosphere during the STREAM II campaign(Stratosphere Troposphere Experiments by AircraftMeasurements) in July 1994. Occasionally, high COconcentrations of 200-300 pbbv were measured in thelowermost stratosphere, together with relatively highHNO3 concentrations up to 1.6 ppbv. The particlenumber concentration (at standard pressure andtemperature) between 0.018-1 m decreased acrossthe tropopause, from >1000 cm-3 in the uppertroposphere to <500 cm-3 in the lowermoststratosphere. Since the CO sources are found in thetroposphere, the elevated CO mixing ratios areattributed to mixing of polluted tropospheric air intothe lowermost extratropical stratosphere. Further wehave used a chemical model to illustrate that nitrogenoxide reservoir species (mainly HNO3) determinethe availability of NOx (=NO + NO2) andtherefore largely control the total net O3production in the lower kilometers of thestratosphere. Model simulations, applying additionalNOx perturbations from aircraft, show that theO3 production efficiency of NOx is smallerthan previously assumed, under conditions withrelatively high HNO3 mixing ratios, as observedduring STREAM II. The model simulations furthersuggest a relatively high O3 productionefficiency from CO oxidation, as a result of therelatively high ambient HNO3 and NOxconcentrations, implying that upward transport of COrich air enhances O3 production in the lowermoststratosphere. Analysis of the measurements and themodel calculations suggest that the lowermoststratosphere is a transition region in which thechemistry deviates from both the upper troposphere andlower stratosphere.  相似文献   

9.
We present here experimental determinations of mass accommodation coefficients using a low pressure tube reactor in which monodispersed droplets, generated by a vibrating orifice, are brought into contact with known amounts of trace gases. The uptake of the gases and the accommodation coefficient are determined by chemical analysis of the aqueous phase.We report in this article measurements of exp=(6.0±0.8)×10–2 at 298 K and with a total pressure of 38 Torr for SO2, (5.0±1.0)×10–2 at 297 K and total pressure of 52 Torr for HNO3, (1.5±0.6)×10–3 at 298 K and total pressure of 50 Torr for NO2, (2.4±1.0)×10–2 at 290 K and total pressure of 70 Torr for NH3.These values are corrected for mass transport limitations in the gas phase leading to =(1.3±0.1)×10–1 (298 K) for SO2, (1.1±0.1)×10–1 (298 K) for HNO3, (9.7±0.9)×10–2 (290 K) for NH3, (1.5±0.8)×10–3 (298 K) for NO2 but this last value should not be considered as the true value of for NO2 because of possible chemical interferences.Results are discussed in terms of experimental conditions which determine the presence of limitations on the mass transport rates of gaseous species into an aqueous phase, which permits the correction of the experimental values.  相似文献   

10.
Simultaneous measurements of peroxy and nitrate radicals at Schauinsland   总被引：3，自引：0，他引：3  
We present simultaneous field measurements of NO3 and peroxy radicals made at night in a forested area (Schauinsland, Black Forest, 48° N, 8° N, 1150 ASL), together with measurements of CO, O3, NO x , NO y , and hydrocarbons, as well as meteorological parameters. NO2, NO3, HO2, and (RO2) radicals are detected with matrix isolation/electron spin resonance (MIESR). NO3 and HO2 were found to be present in the range of 0–10 ppt, whilst organic peroxy radicals reached concentrations of 40 ppt. NO3, RO2, and HO2 exhibited strong variations, in contrast to the almost constant values of the longer lived trace gases. The data suggest anticorrelation between NO3 and RO2 radical concentrations at night.The measured trace gas set allows the calculation of NO3 and peroxy radical concentrations, using a chemical box model. From these simulations, it is concluded that the observed anthropogenic hydrocarbons are not sufficient to explain the observed RO2 concentrations. The chemical budget of both NO3 and RO2 radicals can be understood if emissions of monoterpenes are included. The measured HO2 can only be explained by the model, when NO concentrations at night of around 5 ppt are assumed to be present. The presence of HO2 radicals implies the presence of hydroxyl radicals at night in concentrations of up to 105 cm–3.  相似文献   

11.
The latitudinal variation of the photolysis frequency of ozone to O(1D) atoms, J(O1D), was measured using a filter radiometer during the cruise ANT VII/1 of the research vessel Polarstern in September/October 1988. The J(O1D) noon values exhibited a maximum of 3.6×10-5 s-1 (2 sr) at the equator and decreased strongly towards higher latitudes. J(O1D) reached highest values for clean marine background air with low aerosol load and almost cloudless sky. The J(O1D) data, measured under these conditions and a temperature of 295 K, can be expressed by: % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOsaiaacI% cacaqGpbWaaWbaaSqabeaaiiaacqWF8baFaaGccaqGebGaaeykaiaa% bccacqWF9aqpcaqGGaGaaeyzaiaabIhacaqGWbGaaeiiaiaabUhacq% GHsislcaaI4aGaaiOlaiaaicdacaaIYaGaeyOeI0IaaGioaiaac6ca% caaI4aGaaiiEaiaaigdacaaIWaWaaWbaaSqabeaacqGHsislcaaIZa% aaaOGaaeiiaiaabIhacaqGGaGaam4uaiabgUcaRiaaiodacaGGUaGa% aGinaiaacIhacaaIXaGaaGimamaaCaaaleqabaGaeyOeI0IaaGOnaa% aakiaadofadaahaaWcbeqaaiaaikdaaaGccaGG9bGaaeikaiaaboha% daahaaWcbeqaaiabgkHiTiaaigdaaaGccaGGPaaaaa!5EE9!\[J({\text{O}}^| {\text{D) }} = {\text{ exp \{ }} - 8.02 - 8.8x10^{ - 3} {\text{ x }}S + 3.4x10^{ - 6} S^2 \} {\text{(s}}^{ - 1} )\] where S represents the product of the overhead ozone column (DU) and the secant of the solar zenith angle. The meridional profile of the primary OH radical production rate P(OH) was calculated from the J(O1D) measurements and simultaneously recorded O3 and H2O mixing ratios. While the latitudinal distribution of J(O1D) and water vapour was nearly symmetric to the equator, high tropospheric ozone levels up to 40 ppb were observed in the Southern Hemisphere, SH, resulting in higher P(OH) in the SH.  相似文献   

12.
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   

13.
On the Significance of the Webb Correction to Fluxes   总被引：2，自引：0，他引：2  
For establishing correct mass or energy balances at the Earth's surface, detailed and correct measurements of air constituent fluxes are needed. Flux measurements obtained from the eddy covariance technique have to pass several corrections of different relevance in order to give correct flux data. One of these corrections, the Webb correction, is analysed herein from latent heat flux and CO2 flux data recorded during two field experiments. The significance of this correction for the latent heat flux data varies with the air humidity and the Bowen ratio. The correction changes the latent heat flux values only a little, but significantly (by 2 to 3%). For other air constituents (like CO2), the Webb correction is much more important (20 to 30% of the flux).  相似文献   

14.
The NO3 radical initiated oxidation of cyclopentene, cyclohexene and 1-methyl-cyclohexene has been studied. The products formed in an N2O5-NO2-N2-O2-cycloalkene-static reactor system, at 0.1 MPa and 296 K, were investigated using long path FTIR. The principal products were aldehydes formed via a ring opening process. The reactions also resulted in significant yields of three types of ring retaining nitrooxy-substituted compounds. The average yields of alkyl nitrates from, e.g., reactions with cycloalkene were 25.1% 2-oxo-cyclohexyl nitrate, 22.8% 2-hydroxy-cyclohexyl nitrate and 4.0% 1,2-cyclohexyl dinitrate. The mechanisms involved resembles those proposed for acyclic alkenes. In absence of NO, -oxo and -hydroxy-cycloalkyl nitrates are formed via self reactions of -nitrooxy substituted cycloalkyl peroxy radicals. Estimated branching ratios for the reactants leading to ring retaining products in the presence and in the absence of NO are given and the possible relevance of these reactions for cycloalkenes under tropospheric conditions is discussed.  相似文献   

15.
This paper shows a comparative study of particle and surface ozone concentration measurements undertaken simultaneously at two distinct semi-urban locations distant by 4 km at Saint-Denis, the main city of La Réunion island (21.5° S, 55.5° E) during austral autumn (May 2000). Black carbon (BC) particles measured at La Réunion University, the first site situated in the suburbs of Saint-Denis, show straight-forward anti-correlation with ozone, especially during pollution peaks ( 650 ng/m3 and 15 ppbv, for BC and ozone respectively) and at night-time (90 ng/m3 and 18.5 ppbv, for BC and ozone respectively). NOx (NO and NO2) and PM10 particles were also measured in parallel with ozone at Lislet Geoffroy college, a second site situated closer to the city centre. NOx and PM10 particles are anti-correlated with ozone, with noticeable ozone destruction during peak hours (mean 6 and 9 ppbv at 7 a.m. and 8 p.m. respectively) when NOx and PM10 concentrations exhibit maximum values. We observe a net daytime ozone creation (19 ppbv, O3 +4.5 ppbv), following both photochemical and dynamical processes. At night-time however, ozone recovers (mean 11 ppbv) when anthropogenic activities are lower ([BC] 100 ng/m3). BC and PM10 concentration variation obtained during an experiment at the second site shows that the main origin of particles is anthropogenic emission (vehicles), which in turn influences directly ozone variability. Saint-Denis BC and ozone concentrations are also compared to measurements obtained during early autumn (March 2000) at Sainte-Rose (third site), a quite remote oceanic location. Contrarily to Saint-Denis observations, a net daytime ozone loss (14.5 ppbv at 4 p.m.) is noticed at Sainte-Rose while ozone recovers (17 ppbv) at night-time, with however a lower amplitude than at Saint-Denis. Preliminary results presented here are handful data sets for modelling and which may contribute to a better comprehension of ozone variability in relatively polluted areas.  相似文献   

16.
In summer, atmospheric ozone was measured from an aircraft platform simultaneously with nitric oxide (NO), oxides of nitrogen (NO y ), and water vapor over the Pacific Ocean in east Asia from 34° N to 19° N along the longitude of 138±3°E. NO y was measured with the aid of a ferrous sulfate converter. The altitude covered was from 0.5 to 5 km. A good correlation in the smoothed meridional distributions between ozone and NO y was seen. In particular, north of 25° N, ozone and NO y mixing ratios were considerably higher than those observed in tropical marine air south of 25° N. NO y and O3 reached a minimum of 50 pptv and 4 ppbv respectively in the boundary layer at a latitude of 20° N. The NO concentration between 2 and 5 km at the same latitude was 30 pptv. The profiles of ozone and water vapor mixing ratios were highly anti-correlated between 25° N and 20° N. In contrast, it was much poorer at the latitude of 33° N, suggesting a net photochemical production of ozone there.  相似文献   

17.
The results of an intercomparison campaign of eight different long path UV-visible DOAS instruments measuring NO2, O3 and SO2 concentrations in a moderately polluted urban site are presented. For effective optical path lengths of 230 and 780 m the overall spread of these measurements (±1) are 5×1010, 6×1010 and 1×1010 molec·cm-3 (2.0, 2.4, and 0.4 ppb) for these molecules respectively when all instruments used a common set of absorption cross sections. The remaining differences are not completely random and the systematic differences are attributed to the different retrieval methods used for each instrument.  相似文献   

18.
Since April 1986, measurements of the CO2 concentration in the surface air have been conducted at the Meteorological Research Institure (MRI, 36°04 N, 140°07 E, 25 m above sea level) in Tsukuba, located 50 km northeast of Tokyo, Japan. The CO2 data measured over times between 11:00 Japan Standard Time (JST) and 16:00 JST (C N ) were considered to be representative of the air (within a few ppmv) in the planetary boundary layer. To evaluate the representative CO2 level on a spatial scale larger than that of the C N record, the CO2 data with hour-to-hour variation less than 1 ppmv were selected (C P ). Comparison of these data with those of Ryori (39°02 N, 141°50 E), a continental station operated by the Japan Meteorological Agency, indicates that the C P record provides a representative CO2 level in the air on spatial scales of at least a few hundred kilometers.The C N record allows an investigation of the internanual changes in photosynthesis/respiration against changes in climatological parameters. Within a small temperature anomaly (ca.±1 °C) respiration is sensitive to the temperature change, while photosynthesis is less sensitive. When the temperature anomaly is large, however, photosynthesis and respiration tend to be competitive.  相似文献   

19.
The photochemical oxidation of SO2 in the presence of NO and C3H6 was studied in a 18.2 liter pyrex reactor. When light intensity, irradiation time and SO2 concentration were constant, SO4 2- concentration, derived from the total volume of aerosol produced, peaked when [C3H6]/[NO] was approximately 6.0. Another increase im SO4 2- formation was reached at very high ratios (>50). The experimental observations are consistent with the two SO2 oxidation mechanisms. At low [C3H6]/[NO] ratios, the processes proceed via the HO–SO2 reaction, while at high ratios the O3–C3H6 adduct is assumed to oxidize SO2 to produce SO4 2- aerosols.  相似文献   

20.
A cryogenic system for the airborne and ground based sampling of ambient radicals by matrix isolation is described. The trapped radicals, e.g., NO2 and RO2, are analyzed by ESR. The technique has been improved, mainly by addition of water vapor to the sampled air, to yield a collection efficiency of (90±10)% and a lower detection limit of about 20 ppt, but it still does not distinguish between the different RO2. Careful calibration reduced the measurement error (1 ) to ±10% for NO2 and ±15% for HO2. Two diurnal variations of RO2 and NO2 at ground level and vertical profiles in the lower troposphere are presented.  相似文献   

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