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1.
《Atmospheric Research》2007,83(3-4):547-553
Ions can speed up the formation of aerosol particles. The former studies have mainly concerned on the role of the ion charge itself. We have studied the possible (additional) role of the actual small air ion spectrum shape, and the quantitative role of ion–ion recombination pathway. By means of our ion evolution model, formation of new species (H2SO4)n(NH3)m(HNO3)k via ion–ion recombination was investigated. The model shows how the generation rate of the new species depends on the concentrations of H2SO4 and NH3, and how it depends on the tropospheric background aerosol situation. The rate can be up to a few new neutral complexes per cubic centimeter and per second. New particle generation via ion–ion recombination provides an extra channel, especially for the clean atmosphere. Former results have shown that such situations are often present in Antarctica. Our aerosol spectrum measurements reveal a number of similar non-Antarctic results. Sometimes, such situations are followed by aerosol bursts, which may be (partly) due to an ion–ion recombination channel.  相似文献   

2.
The effects of below-cloud aerosol on the acidification process of rain   总被引：1，自引：0，他引：1  
Using a model of the acidification process of rain, we calculate and analyze the effects and contributions of a below-cloud aerosol in its different concentrations and acidities on the pH and ion components of rain (SO 4 2– , H+, NO 3 – , NH 4 + , etc.) under the conditions of different concentrations of pollution gases. The results show that the aerosol has an acidification or alkalization effect on the rain which changes the pHs of rain and aerosol. As acidifying pollution gas concentrations (SO2, HNO3) are low, the acid aerosol has important effects on the pH and H+ of rain, but as the gas concentrations are high, the acid aerosol has very little effect. The alkalizing aerosol makes the pH of rain increase by between 0.3 and 0.5 and neutralizes about 60% of H+ in the rain. As alkalizing pollution gas NH3 exists, the acid aerosol has important effects on the pH and H+ of rain. But the alkalizing aerosol has very little effect, especially as the NH3 concentration is high. The percentage contribution of the aerosol to SO 4 2– in rain is generally 7–15%, the contribution of the aerosol to NO 3 – is nearly the same as that of HNO3=1 ppb, and the contribution of the aerosol to NH 4 + is nearly the same as that of NH3, from 5 to 7 ppb, and is an important source of NH 4 + in rain. Finally, according to the actual conditions of typical regions in the south and north of China (Chongqing and Beijing), we analyze the effects of aerosol and pollution gases on the ion components of rain.  相似文献   

3.
In this study bulk airborne aerosol composition measured by the PILS-IC (integration time of 3 min 24 s) during TRACE-P P3B Flight 10 are used to investigate the ionic chemical composition and mixing state of biomass burning particles. A biomass burning plume, roughly 3–4 days old, moderately influenced by urban pollution aerosols recorded in the Philippine Sea is investigated. Focusing on the fine particle NO3−, SO42−, K+, NH4+, and water-soluble organics, the observed correlations and nearly 1-to-1 molar ratios between K+ and NO3− and between NH4+ and (SO42−+ inferred Organics) suggest the presence of fine-mode KNO3, (NH4)2SO4, and NH4(Organics) aerosols. Under the assumption that these ion pairs existed, and because KNO3 is thermodynamically less favored than K2SO4 in a mixture of NO3−, SO42−, K+, NH4+, and Organic anions, the measurements suggest that aerosols could be composed of biomass burning particles (KNO3) mixed to a large degree externally with the (NH4)2SO4 aerosols. A “closed-mode” thermodynamic aerosol simulation predicts that a degree of external mixing (by SO42− mass) of 60 to 100% is necessary to achieve the observed ionic associations in terms of the existence of KNO3. However, the degree of external mixing is most likely larger than 90%, based on both the presence of KNO3 and the amounts of NH4NO3. Calculations are also shown that the aerosol mixing state significantly impacts particle growth by water condensation/evaporation. In the case of P3B Flight #10, the internal mixture is generally more hygroscopic than the external mixture. This method for estimating particle mixing state from bulk aerosol data is less definitive than single particle analysis, but because the data are quantitative, it may provide a complementary method to single particle chemical analysis.  相似文献   

4.
Henry's law constants KH (mol kg–1 atm–1) for the reaction HOCl(g)=HOCl(aq) near room temperature, literature data for the associated enthalpy change, and solubilities of HOCl in aqueous H2SO4 (46 to 60 wt%) at temperatures relevant to the stratosphere (200 KT230 K) are shown to be thermodynamically consistent. Effective Henry's law constants [H*=mHOCl/pHOCl, in mol kg–1 atm–1] of HOCl in aqueous H2SO4 are given by: ln(H*)=6.4946–mH2SO4(–0.04107+54.56/T)–5862 (1/To–1/T) where T(K) is temperature and To=298.15K. The activity coefficient of HOCl in aqueous H2SO4 has a simple Setchenow-type dependence upon H2SO4 molality.  相似文献   

5.
An in-cloud scavenging case study of the major ions (NH4 +, SO4 2- and NO3 -) determining the cloudwater composition at a mountain site (1620 m.a.s.l.) is presented. A comparison between in-cloud measurements of the cloudwater composition, liquid water content, gas concentrations and aerosol concentrations and pre-cloud gas and aerosol concentrations yields the following results. Cloudwater concentrations resulted from scavenging of about half of the available NH3, aerosol NH4 +, aerosol NO3 -, and aerosol SO4 2-. Approximately a third of the SO2 was scavenged by the cloudwater and oxidized to SO4 2-. Cloud acidity during the first two hours of cloud interception (pH 3.24) was determined mostly by the scavenged gases (NH3, SO2, and HNO3); aerosol contributions to the acidity were found to be small. Observations of gas and aerosol concentrations at three elevations prior to several winter precipitation events indicated that NH3 concentrations are typically half (12–80 %) of the total (gas and aerosol) N (-III) concentrations. HNO3 typically is present at much lower concentrations (1–55 %) than aerosol NO3 -. Concentrations of SO2 are a substantial component of total sulfur, with concentrations averaging 60 % (14–76 %) of the total S (IV and VI).  相似文献   

6.
The growth of monodisperse particles (0.07 to 0.5 µm) exposed to SO2 (0–860 ppb), H2O2 (0–150 ppb) and sometimes NH3 (0–550 ppb) in purified air at 22 °C at relative humidities ranging from 25 to 75% were measured using the Tandem Differential Mobility Analyzer technique. The experiments were performed in a flow reactor with aqueous (NH4)2SO4 and Na2SO4 droplets. For (NH4)2SO4 droplets the fractional diameter growth was independent of size above 0.3 µm but decreased with decreasing size below that. When NH3 was added the fractional growth increased with decreasing size. Measurements were compared with predictions of a model that accounts for solubility of the reactive gases, the liquid phase oxidation of SO2 by H2O2, and ionic equilibria. Agreement between measured and predicted droplet growth is reasonable when the ionic strength effects are included. Theory and experiments suggest that NH3 evaporation is responsible for the decrease in relative growth rates for small aqueous ammonium sulfate particles. The observed droplet growth rates are too slow to explain observed growth rates of secondary atmospheric sulfate particles.  相似文献   

7.
Inorganic seed particles have relatively large surface area, and play an important role in the formation and aging of secondary organic aerosol (SOA). The effects of dry (NH4)2SO4 which is the most commonly found in urban atmosphere on the aged benzene SOA were qualitatively studied utilizing aerosol laser time-of-flight mass spectrometer (ALTOFMS) coupled with Fuzzy C-Means (FCM) clustering algorithm in this study. Experimental results indicated that nitrophenol, oxocarboxylic acid, epoxide products are the predominant components in the aged benzene SOA in the presence of low concentration (about 10 μg m?3) of dry (NH4)2SO4. These aged products are the same as the previously obtained aged benzene SOA without (NH4)2SO4 seed aerosol, indicating that low concentration of dry (NH4)2SO4 acts just as the nucleation or condensation center of the SOA, and do not affect the chemical composition of SOA. However, 1 H-imidazole, 1 H-imidazole-2-carbaldehyde, hydrated 1 H-imidazole-2-carbaldehyde, 2,2′-biimidazole, hydrated N-glyoxal substituted 1 H-imidazole, N-glyoxal substituted hydrated 1 H-imidazole-2- carbaldehyde, hydrated mono glyoxal substituted hydrated 1 H-imidazole-2-carboxaldehyde, mono glyoxal substituted 2,2-biimidazole and hydrated glyoxal dimer substituted imidazole which are formed from ammonium ion reaction with glyoxal are the major particulate products in the aged benzene SOA in the presence of high concentration (about 100 μg m?3) of dry (NH4)2SO4. The retention of water on the dry (NH4)2SO4 particles creates ammonium ion, which can promote the formation of high-molecular-weight (HMW) products through multiphase reactions such as hydration and polymerization of aldehydes form from OH-initiated oxidation of benzene.  相似文献   

8.
In this study the possible conditions for new aerosol particle formation in a background area of Helsinki have been analysed. The measurements of aerosol particle size distribution, main gaseous pollutant compounds, UV spectra and meteorological parameters were performed during April–May 1993. The main interest was concentrated on the investigations of photochemical OH radical formation, the oxidation of gas phase SO2 to H2SO4 and the formation of H2SO4---H2O aerosol particles. The measurements were analysed using a model for OH radical formation and aerosol dynamics. The analysis of aerosol size distributions was carried out using positive matrix factorization. The main conclusion is that based on our model analysis no evidence of new particle formation in the vicinity of the measurement station was found. However, the high concentrations of aerosol particles in the ultrafine size range indicate that some other particle formation pathways are to be considered.  相似文献   

9.
A one-dimensional cloud model with size-resolved microphysics and size-resolved aqueous-phase chemistry, driven by prescribed dynamics, has been used to study gas scavenging by weak precipitation developed from low-level, warm stratiform clouds. The dependence of the gas removal rate on the physical and chemical properties of precipitation has been explored under controlled initial conditions. It is found that the removal of four gaseous species (SO2, NH3, H2O2 and HNO3) strongly depends on the total droplet surface area, regardless the mean size of droplets. The removal rates also correlate positively with the precipitation rate, especially for precipitation having a mean radius larger than 20 μm. The dependence of the scavenging coefficients on the total droplet surface area is stronger than on the precipitation rate. The removal rates of SO2, NH3 and H2O2 by precipitation strongly depend on the others' initial concentrations. When NH3 (or H2O2) concentration is much lower than that of SO2, the removal rate of SO2 is then controlled by the concentration of H2O2 (or NH3). The removal of NH3 (or H2O2) also directly depends on the concentration of SO2. NH3 and H2O2 can also indirectly affect each other's removal rate through interaction with SO2. The scavenging coefficient of SO2 increases with the concentration ratio of NH3 to SO2 if the ratio is larger than 0.5, while the scavenging coefficient of NH3 increases with the concentration ratio of SO2 to NH3 when the ratio is smaller than 1. The scavenging coefficient of H2O2 generally increases with the concentration ratio of SO2 to H2O2. Although the Henry's law equilibrium approach seems to be able to simulate gas scavenging by cloud droplets, it causes large errors when used for simulating the scavenging of soluble gas species by droplets of precipitating sizes.  相似文献   

10.
A three-dimensional model of the global ammonia cycle   总被引：16，自引：0，他引：16  
Using a three-dimensional (3-D) transport model of the troposphere, we calculated the global distributions of ammonia (NH3) and ammonium (NH 4 + ), taking into account removal of NH3 on acidic aerosols, in liquid water clouds and by reaction with OH. Our estimated global 10°×10° NH3 emission inventory of 45 Tg N-NH3 yr– provides a reasonable agreement between calculated wet NH 4 + deposition and measurements and of measured and modeled NH 4 + in aerosols, although in Africa and Asia especially discrepancies exist.NH3 emissions from natural continental ecosystems were calculated applying a canopy compensation point and oceanic NH3 emissions were related to those of DMS (dimethylsulfide). In many regions of the earth, the pH found in rain and cloud water can be attributed to acidity derived from NO, SO2 and DMS emissions and alkalinity from NH3. In the remote lower troposphere, sulfate aerosols are calculated to be almost neutralized to ammonium sulfate (NH4)2SO4, whereas in the middle and upper troposphere, according to our calculations, the aerosol should be more acidic, as a result of the oxidation of DMS and SO2 throughout the troposphere and removal of NH3 on acidic aerosols at lower heights. Although the removal of NH3 by reaction with the OH radical is relatively slow, the intermediate NH2 radical can provide a substantial annual N2O source of 0.9 –0.4 +0.9 Tg, thus contributing byca. 5% to estimated global N2O production. The oxidation by OH of NH3 from anthropogenic sources accounts for 10% of the estimated total anthropogenic sources of N2O. This source was not accounted for in previous studies, and is mainly located in the tropics, which have high NH3 and OH concentrations. Biomass burning plumes, containing high NO x and NH3 concentrations provide favourable conditions for gas phase N2O production. This source is probably underestimated in this model study, due to the coarse resolution of the 3-D model, and the rather low biomass burning NH3 and NO x emissions adopted. The estimate depends heavily on poorly known concentrations of NH3 (and NO x ) in the tropics, and uncertainties in the rate constants of the reactions NH2 + NO2 N2O + H2O (R4), and NH2 + O3 NH2O + O2 (R7).  相似文献   

11.
The pH and the concentrations of sulfate, nitrate, ammonia, and calcium in rainwater were measured for two periods of a single midwest rainstorm which occurred over a mesometeorological network in central Illinois on 24–25 July 1979. Regression analysis was used to compare ion concentrations with rainfall amount, and ion balance was used to compare cation and anion concentrations at individual sites. Only the ions SO4 2- and NO3 - show any significant relationship to rainfall amount, decreasing as rainwater amounts increase (r=–0.57 and –0.60, respectively). During the first period of the rainstorm, a sequential sampler measurements allowed the calculation of detailed temporal variations in SO4 2-, pH, and rain rate. SO4 2- decreased, and pH increased as the rate increased and the opposite temporal pattern occurred as the rain decreased at the end of the period. Reasons for these variations are discussed.Research done while a visiting scientist at the Illinois State Water Survey, Champaign, Illinois, U.S.A.  相似文献   

12.
Atmospheric nitric acid measurements by ACIMS (Active Chemical Ionization Mass Spectrometry) are based on ion-molecule reactions of CO3 -(H2O) n and NO3 -(H2O) n with HNO3. We have studied these reactions in the laboratory using a flow tube apparatus with mass spectrometric detection of reactant and product ions. Both product ion distributions and rate coefficients were measured. All reactions were investigated in an N2-buffer (1–3 hPa) at room temperature. The reaction rate coefficients of OH-, O2 -, O3 -, CO4 -, CO3 -, CO3 -H2O, NO3 -, and NO3 -H2O were measured relative to the known rate k=3.0×10-9 cm3 s-1 for the reaction of O- with HNO3. The main product ion of the reaction of CO3 -H2O with HNO3 was found to be (CO3HNO3)- supporting a previous suggestion made on the basis of balloon-borne ACIMS measurements. For the reaction of bare CO3 - with HNO3 three product ions were observed, namely NO3 -, (NO3OH)-, and (CO3HNO3)-. The reaction rate coefficients for CO3 -H2O (1.7×10-9 cm3 s-1) and NO3 -H2O (1.6×10-9 cm3 s-1) were found to be close to the collision rate. The measured k values for bare CO3 - (1.3×10-9 cm3 s-1) and NO3 - (0.7×10-9 cm3 s-1) are somewhat smaller. The collisional dissociations of CO3 -(H2O) n , NO3 -(H2O) n (n=1, 2), (CO3HNO3)- and (NO3HNO3)-, occasionally influencing ACIMS measurements, were also studied. Fragment ion distributions were measured using a triple quadrupole mass spectrometer. The results showed that previous stratospheric nitric acid measurements were unimpaired from collisional dissociation processes whereas these processes played a major role during previous tropospheric measurements leading to an underestimation of nitric acid concentrations. Previous ACIMS HNO3 detection was also affected by the conversion of CO3 -(H2O) n to NO3 -(H2O) n due to ion source-produced neutral radicals. A novel ACIMS ion source was developed in order to avoid these problems and to improve the ACIMS method.  相似文献   

13.
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   

14.
The second Arctic Gas and Aerosol Sampling Program (AGASP-II) was conducted across the Alaskan and Canadian Arctic in April 1986, to study the in situ aerosol, and the chemical and optical properties of Arctic haze. The NOAA WP-3D aircraft, with special instrumentation added, made six flights during AGASP-II. Measurements of wind, pressure, temperature, ozone, water vapor, condensation nuclei (CN) concentration, and aerosol scattering extinction (bsp) were used to determine the location of significant haze layers. The measurements made on the first three flights, over the Arctic Ocean north of Barrow and over the Beaufort Sea north of Barter Island, Alaska are discussed in detail in this report of the first phase of AGASP II. In the Alaskan Arctic the WP-3D detected a large and persistent region of haze between 960 and 750 mb, in a thermally stable layer, on 2, 8, and 9 April 1986. At its most dense, the haze contained CN concentrations >10,000 cm–3 and bsp of 80×10–6 m–1 suggesting active SO2 to H2SO4 gas-to-particle conversion. Calculations based upon observed SO2 concentrations and ambient relative humidities suggest that 104–105 small H2SO4 droplets could have been produced in the haze layers. High concentrations of sub-micron H2SO4 droplets were collected in haze. Ozone concentrations were 5–10 ppb higher in the haze layers than in the surrounding troposphere. Outside the regions of haze, CN concentrations ranged from 100 to 400 cm–3 and bsp values were about (20–40)×10–6 m–1. Air mass trajectories were computed to depict the air flow upwind of regions in which haze was observed. In two cases the back trajectories and ground measurements suggested the source to be in central Europe.  相似文献   

15.
A box model, involving simple heterogeneous reaction processes associated with the production of non-sea-salt sulfate (nss-SO 4 2– ) particles, is used to investigate the oxidation processes of dimethylsulfide (DMS or CH3SCH3) in the marine atmosphere. The model is applied to chemical reactions in the atmospheric surface mixing layer, at intervals of 15 degrees latitude between 60° N and 60° S. Given that the addition reaction of the hydroxyl radical (OH) to the sulfur atom in the DMS molecule is faster at lower temperature than at higher temperature and that it is the predominant pathway for the production of methanesulfonic acid (MSA or CH3SO3H), the results can well explain both the increasing tendency of the molar ratio of MSA to nss-SO 4 2– toward higher latitudes and the uniform distribution with latitude of sulfur dioxide (SO2). The predicted production rate of MSA increases with increasing latitude due to the elevated rate constant of the addition reaction at lower temperature. Since latitudinal distributions of OH concentration and DMS reaction rate with OH are opposite, a uniform production rate of SO2 is realized over the globe. The primary sink of DMS in unpolluted air is caused by the reaction with OH. Reaction of DMS with the nitrate radical (NO3) also reduces DMS concentration but it is less important compared with that of OH. Concentrations of SO2, MSA, and nss-SO 4 2– are almost independent of NO x concentration and radiation field. If dimethylsulfoxide (DMSO or CH3S(O)CH3) is produced by the addition reaction and further converted to sulfuric acid (H2SO4) in an aqueous solution of cloud droplets, the oxidation process of DMSO might be important for the production of aerosol particles containing nss-SO 4 2– at high latitudes.  相似文献   

16.
A Forest SO2 Absorption Model (ForSAM) was developed to simulate (1) SO2 plume dispersion from an emission source, (2) subsequent SO2 absorption by coniferous forests growing downwind from the source. There are three modules: (1) a buoyancy module, (2) a dispersion module, and (3) a foliar absorption module. These modules were used to calculate hourly abovecanopy SO2 concentrations and in-canopy deposition velocities, as well as daily amounts of SO2 absorbed by the forest canopy for downwind distances to 42 km. Model performance testing was done with meteorological data (including ambient SO2 concentrations) collected at various locations downwind from a coal-burning power generator at Grand Lake in central New Brunswick, Canada. Annual SO2 emissions from this facility amounted to about 30,000 tonnes. Calculated SO2 concentrations were similar to those obtained in the field. Calculated SO2 deposition velocities generally agreed with published values.Notation c air parcel cooling parameter (non-dimensional) - E foliar absorption quotient (non-dimensional) - f areal fraction of foliage free from water (non-dimensional) - f w SO2 content of air parcel - h height of the surface layer (m) - H height of the convective mixing layer (m) - H stack stack height (m) - k time level - k drag coefficient of drag on the air parcel (non-dimensional) - K z eddy viscosity coefficient for SO2 (m2·s–1) - L Monin-Obukhov length scale (m) - L A single-sided leaf area index (LAI) - n degree-of-sky cloudiness (non-dimensional) - N number of parcels released with every puff (non-dimensional) - PAR photosynthetically active radiation (W m–2) - Q emission rate (kg s–2) - r b diffusive boundary-layer resistance (s m–1) - r c canopy resistance (s m–1) - r cuticle cuticular resistance (s m–1) - r m mesophyllic resistance (s m–1) - r s stomatal resistance (s m–1) - r exit smokestack exit radius (m) - R normally distributed random variable with mean of zero and variance of t (s) - u * frictional velocity scale, (m s–1) - v lateral wind vector (m s–1) - v d SO2 dry deposition velocity (m s–1) - VCD water vapour deficit (mb) - z can mean tree height (m) - Z zenith position of the sun (deg) - environmental lapse rate (°C m–1) - dry adiabatic lapse rate (0.00986°C m–1) - von Kármán's constant (0.04) - B vertical velocities initiated by buoyancy (m s–1) - canopy extinction coefficient (non-dimensional) - ()a denotes ambient conditions - ()can denotes conditions at the top of the forest canopy - ()h denotes conditions at the top of the surface layer - ()H denotes conditions at the top of the mixed layer - ()s denotes conditions at the canopy surface - ()p denotes conditions of the air parcels  相似文献   

17.
Intensive measurements of gas and aerosol for 2 weeks were carried out at Qingdao (gas and aerosol in 2000, 2001 and 2002), Fenghuangshan (gas and aerosol in 2000 and 2001), and Dalian (aerosol in 2002) in the winter–spring period. High SO2 episodes were observed on 18 January 2000 at both Qingdao and Fenghuangshan. According to back trajectory calculations and analysis of gaseous species, high SO2 episodes were caused by local pollution and transport.Nitrate, sulfate and ammonium were the major species in PM2.5. Mass fractions of NO3−, nss-SO42− and NH4+ at Qingdao in 2002 were 10%, 12% and 5.5% for PM2.5, respectively, which were higher than that of nss-Ca2+ (1%). Chemical compositions observed at Dalian and Fenghuangshan were similar to those at Qingdao. The mass ratio of nss-SO42−/SO2 at Qingdao in winter was low (< 1.2), indicating that sulfate was probably produced by the slow oxidation of SO2 in the gas phase and/or was transported from outside of Qingdao in winter. The equivalent ratio of NH4+ to nss-SO42− was 1.39, suggesting that ammonium sulfate was one of the major chemical compositions in PM2.5. The NO3−/SO42− ratio at Qingdao was higher than that at remote places in East Asia. Gas and aerosol data obtained at Fenghuangshan were similar to data at Qingdao, suggesting that emissions from small cities may have a great influence on pollution in northern China.  相似文献   

18.
The potential resources on the ion-stimulated syntheses effects of aerosol particles of lower troposphere in test sites in the arctic, mountain, arid and forest areas as the function of irradiation time and gas-precursor concentration were experimentally and theoretically evaluated. The dust-free outdoor air was irradiated with an ionization current of 10− 6 A by α-rays from isotope 239Pu. The total output of radiolytic aerosols (RA) with a diameter of 3–1000 nm was found to be 0.05–0.1 molecules per 1 eV of absorbed radiation, while the physical upper limit is 0.25–0.4 molecules/eV. In an interval of exposition time from 6 to 800 s (adsorbed energy is 3 · 1012–1014 eV/cm3) the RA mass concentration at different sites was increased from 1–10 to 50–500 μg/m3. According to the liquid chromatography data the major RA material is the H2O/HNO3 solution with acid concentration  25%. The used physical model presents new aerosols as a product from small and intermediate ion association through formation of neutral clusters and describes adequately some of the peculiarities in field experiment data. Introducing SO2, NH3, and also hydrochloric, nitric and sulphuric acid vapours with concentration 0.1–1 mg/m3 in the irradiated air stimulated an increase of mass aerosol concentration by a factor of 8–30. The mean size also decreased by a factor of 3–5. These facts allowed us to expect that the chemical composition of radiolytic aerosols generated in outdoor air would noticeably differ after addition of the gas-precursors.  相似文献   

19.
Research flights in November 1990 over the central parts of the United States, Wyoming and Colorado, were aimed to the investigation of the properties and microstructure of cirrus clouds (mainly cirrocumulus lenticularis). Among the other parameters measured on board the NCAR Saberliner were the concentration and size distribution of submicron particles and, in some cases, the particle deliquescence. For coarse insoluble particles found inside and outside of cloud elements, size distributions and morphology information were obtained by evaluating inertial impactor samples with an optical microscope and scanning electron microscope. In addition, the coarse particle composition was determined by x-ray energy spectrum analysis. The following conclusions from these measurements are:The large and coarse particle size distribution can be roughly simulated by a log-normal function with the modus around r=0.5 μm. Particle concentrations are very variable between several tenths and several particles per cm3. Particle volume distribution features a distinct maximum around 0.75 μm without a broad plateau which was observed in the case of sampling at lower altitude. Aerosol composition heterogeneity at cirrus cloud level is well documented by the evaluation of the fine particle sampling taken with the UMR sampling system. This heterogeneity can be partly explained by the interaction between aerosol and cloud elements, which is documented by the measured particle size distribution curves inside and outside of cloud elements. Assuming that particle deliquescence is caused by H2SO4 and/or by (NH4)2SO4, particle soluble mass fractions were found to be around 30% in the first case and about 40% in the second. The most frequently occurring elements in large and coarse particles at cirrus cloud level were Si, Cl, Ba, S, Ca and C.  相似文献   

20.
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