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  • 1
    ISSN: 1573-0662
    Keywords: J NO 2 ; NO2 photolysis ; atmospheric photochemistry ; J NO 2measurement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract An instrument, specifically designed for measurements from a balloon platform in the stratosphere, has been used to obtain ground-level values of the atmospheric photodissociation coefficient of nitrogen dioxide, J NO 2.A typical clear-sky value is 8.0×10-3 s-1 when the solar zenith angle is 40°. Measurements were made as a function of solar zenith angle and correlated with a calibrated Eppley UV radiometer. It is shown that J NO 2may be expressed as a simple function of the radiometer output so that estimates of J NO 2can be made using just an upward looking radiometer to an accuracy of about 20%. The measurements are also found to be in good agreement with calculations of J NO 2using a simplified isotropic multiple scattering computer routine.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of atmospheric chemistry 1 (1983), S. 53-63 
    ISSN: 1573-0662
    Keywords: NO2 oxidation ; ozone reactions ; nitrogen pentoxide ; nitrate radical ; kinetic spectroscopy ; atmospheric NO2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract 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 (ΔNO2/ΔO3=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.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of atmospheric chemistry 1 (1984), S. 111-123 
    ISSN: 1573-0662
    Keywords: Sulfur gases ; marine atmosphere ; diurnal variations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Concentrations of sulfur gases H2S and SO2 have been measured in the marine atmosphere over the Atlantic Ocean at various sites. Mean values of 40 ng H2S m-3 STP and 209 ng SO2 m-3 STP are the results of the measurements. A diurnal variation of H2S concentration was detected on the west coast of Ireland with nighttime concentrations of up to 200 ng H2S m-3 STP and values below detection limit (15 ng H2S m-3 STP) during daytime.
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  • 4
    ISSN: 1573-0662
    Keywords: Carbon monoxide ; tropospheric background ; Antarctica ; ozone background ; interhemispheric gradients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The results of a research study of the carbon monoxide concentration from California to 90° S, Antarctica are presented. The data both extend and support other research studies of the latitudinal distribution of carbon monoxide in that higher concentrations are evident over the Northern Hemisphere than over the Southern Hemisphere. Carbon monoxide concentrations range between 50 to 60 ppb with a few peaks into the 60s in the latitudinal area south of the ITCZ and values of 80 ppb or higher at latitudes north of Hawaii. A comparison is also made of carbon monoxide and ozone concentrations along the flight tract between California and Antarctica, over the Ellsworth Mountains of Antarctica, and between 78° S and the South Pole. These ozone-carbon monoxide data show statistically significant negative correlations in the upper troposphere and lower stratosphere over Antarctica. It is believed that this is a good indication of mixing across the tropopause.
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  • 5
    ISSN: 1573-0662
    Keywords: Antarctica ; ice core ; paleoclimate ; atmospheric aerosol ; dust
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Simultaneous measurements of soluble and insoluble impurities were made on the 950 m deep Vostok (78°30′S, 106°54′E, 3420 m a.s.l.) ice core, spanning roughly 50000 yr, using various analytical techniques. We observed higher continental (×37) and marine (×5.1) inputs during the last glacial age than during the Holocene stage. A study of microparticle compositions and of volcanic indicators (Zn, H2SO4), shows that the high observed crustal input is not due to enhanced volcanism, but is rather of continental eolian origin. For the first time, the ionic balance along a deep ice core is established, mainly used in discussing the evolution of the Cl to Na ratio over central East Antarctica with changing climatic conditions: the presence of relatively high amounts of Na2SO4 in the marine aerosol at the Vostok site during the Holocene is demonstrated. Comparison with the Dome C (74°39′S, 124°10′E, 3040 m a.s.l.) results confirms the chronology of the major events: (i) maximum terrestrial input around the last glacial maximum (∼18 ka BP); (ii) end of the high continental flux over Antarctica near 13 ka BP; (iii) marine input varying in an opposing manner to isotopic fluctuations with rather high concentrations beginning to decrease when isotopic values increase and reaching Holocene values at the end of the transition between cold and warmer climate conditions. Detailed comparison with results provided by deep ice cores from other sites which are probably more influenced by oceanic air masses seems to indicate that most of the aerosol reaching central East Antarctica travel over large distance probably at rather high altitude through the troposphere. We can consider that central East Antarctica is well representative of the upper part of the troposphere (higher than i.e., 3000 m) and should, therefore, provide valuable data for global and Antarctic paleoclimatological models.
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  • 6
    ISSN: 1573-0662
    Keywords: Acid rain ; convective diffusion equation ; gas desorption ; gas scavenging ; mass transfer ; reversible washout ; sulfur dioxide ; trace gas absorption ; wet deposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract For the purpose of testing our previously described theory of SO2 scavenging a laboratory investigation was carried out in the UCLA 33 m long rainshaft. Drops with radii between 250 and 2500 μm were allowed to come to terminal velocity, after which they passed through a chamber of variable length filled with various SO2 concentrations in air. After falling through a gas separating chamber consisting of a fluorocarbon gas the drops were collected and analyzed for their total S content in order to determine the rate of SO 2 absorption. The SO2 concentration in air studied ranged between 1 and 60% (v). Such relatively large concentrations were necessary due to the short times the drops were exposed to SO2 in the present setup. The present experimental results were therefore not used to simulate atmospheric conditions but rather to test our previously derived theory which is applicable to any laboratory or atmospheric condition. Comparison of our studies with the results from our theory applied to our laboratory conditions led to predicted values for the S concentration in the drops which agreed well with those observed if the drops had radii smaller than 500 μm. In order to obtain agreement between predicted and observed S concentrations in larger drops, an empirically derived eddy diffusivity for SO2 in water had to be included in the theory to take into account the effect of turbulent mixing inside such large drops. In a subsequent set of experiments, drops initially saturated with S (IV) were allowed to fall through S-free air to determine the rate of SO 2 desorption. The results of these studies also agreed well with the results of our theoretical model, thus justifying the reversibility assumption made in our theoretical models. In a final set of experiments, the effects of oxidation on SO2 absorption was studied by means of drops containing various amounts of H2O2. For comparable exposure times to SO2, the S concentration in drops with H2O2 was found to be up to 10 times higher than the concentration in drops in which no oxidation occurred.
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  • 7
    ISSN: 1573-0662
    Keywords: Formaldehyde ; sulfur (IV) ; sulfonic acids ; sulfur oxidation ; air pollution ; fogwater chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Elevated concentrations of S(IV) and formaldehyde were observed in fog- and cloudwater at sites in California. The highest concentrations (up to 3 mM S(IV) and 0.7 mM CH2O) were measured at Bakersfield, during a prolonged period of repeated fog. In Bakersfield [S(IV)] generally exceeded [CH2O], while in the Los Angeles area the reverse was observed. The lowest concentrations of both species were observed at marine and high altitude sites away from local emissions. Equilibrium computations indicate that high concentrations of S(IV) cannot be achieved without the formation of S(IV)-RCHO adducts.
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  • 8
    ISSN: 1573-0662
    Keywords: aerosols ; middle atmosphere ; vertical transport ; residence time ; photophoresis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Gravitophotophoresis, a type of photophoresis related to the direction of gravity, is examined in view of its possible importance to some aerosols in stratosphere and mesosphere. particles of various materials from about 1 to 100 μm in size show levitation by photophoretic forces under laboratory simulation of irradiation by the sun at air densities of the middle atmosphere. Minimum air densities for levitation are about 2–3 g m−3 with mineral and metallic powders, about 0.08 g m−3 with carbonaceous powders. The fraction of rising particles can be about 0.01 to 1%. Velocities of ascent are in the range of 0.001 to 0.01 m s−1 at a pressure of several mbar. The magnitude and the mechanical character of the force of gravitophotophoresis can be explained if it is identified with a radiometer force caused by a difference of the accommodation coefficient on the surface. It is suggested that gravitophotophoresis can be important to the residence time and the maximum altitude of carbonaceous and mineral particles, such as volcanic ash or products of meteorite impact, and to the presence of microorgnisms in the middle atmosphere.
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  • 9
    ISSN: 1573-0662
    Keywords: Stratosphere ; deuterated water ; isotopic composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Factors influencing the18O content of stratospheric H2O are reviewed in order to provide a theoretical framework for the interpretation of measurements of this quantity, which are now becoming available. Depletions in18O of 5–10% in stratospheric H2O are expected based on the known correlation between that of D and18O in tropospheric H2O and observed measurements of large (typically 50%) depletions of D in stratospheric H2O. H2O formed in the stratosphere as a result of oxidation of CH4 can be expected to reflect primarily the18O content of stratospheric O2, which is the same as that of tropospheric O2 (slightly enhanced with respect to standard mean ocean water). Thus, a reduction in the18O depletion is expected with increasing altitude, but not a large enhancement in18O in upper stratospheric H2O as found in recent far infrared measurements. The observed large enhancement of18O in stratospheric O3 is not expected to be reflected in stratospheric H2O. Necessary laboratory data for the improved quantification of these effects are reviewed.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of atmospheric chemistry 10 (1990), S. 97-97 
    ISSN: 1573-0662
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Type of Medium: Electronic Resource
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