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R. C. Robbins
,
R. D. Cadle
, and
D. L. Eckhardt

Abstract

A reaction route is suggested, based on experimental results, for the conversion of sodium chloride particles to gaseous hydrogen chloride in the atmosphere. The first step is the hydrolysis of nitrogen dioxide (NO2) to form nitric acid (HNO3) vapor. The second step is either adsorption on the relatively dry sodium chloride particles at relative humidities less than about 75 per cent or, at high relative humidities, solution in aqueous droplets containing sodium chloride. The third step is interaction of the nitric acid and sodium chloride and the fourth is desorption of the hydrogen chloride, either immediately following the reaction or during subsequent evaporation of the droplets.

The results also indicate that the reaction between nitrogen dioxide and sodium chloride to form nitrosyl chloride (NOCl) and sodium nitrate (NaNO3), often suggested as a possible primary step in the formation of chlorine or hydrogen chloride in the atmosphere, occurs at a negligible rate compared with the reaction described above.

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A. L. Lazrus
,
B. Gandrud
, and
R. D. Cadle

Abstract

Evidence is presented indicating that nitrate present in stratospheric filtration samples represents adsorbed nitric acid vapor. The concentrations observed are comparable to those found by solar infrared spectrometry. Concentrations increase with altitude up to 28 km. Concentrations in the Southern Hemisphere are similar to those in the Northern.

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Patrick Hamill
,
R. D. Cadle
, and
C. S. Kiang

Abstract

The homogeneous- and heterogeneous-heteromolecular nucleation of H2SO4-H2O solution droplets in the stratosphere is investigated and order-of-magnitude nucleation rates are evaluated. The heterogeneous processes considered are nucleation (i) onto soluble particles, (ii) onto flat insoluble surfaces, (iii) onto spherical insoluble particles and (iv) onto ions. The relative importance of the various nucleation mechanisms is determined for conditions assumed to correspond to 18 km altitude. Under the assumed conditions the heterogeneous nucleation rate onto insoluble particles is shown to be about 1069 times larger than the homogeneous nucleation rate and 1057 times larger than nucleation onto ions.

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R. D. Cadle
,
W. H. Fischer
,
E. R. Frank
, and
J. P. Lodge Jr.

Abstract

Samples of particles collected by impaction in the antarctic atmosphere near the earth's surface during November and December 1966 contained much higher concentrations of sulfur than similar samples collected in most parts of the world. The sulfur was largely in the form of SO4 , but some S2O8 may also have been present. The cations mere largely NH4 + and H+. Most samples contained little sodium chloride.

The concentrations in the air of collected particles varied from 0.1 to 1 cm−3.

Possible explanations for the high sulfur to chlorine ratio are suggested.

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R. D. Cadle
,
F. E. Grahek
,
B. W. Gandrud
, and
A. L. Lazrus

Abstract

The relative efficiencies of impactors of the type used by Junge and co-workers for collecting stratosphere sulfate particles and of filters used in these laboratories have been determined by flying these collecting devices on the same aircraft in the stratosphere. The impactors have less than 20% of the efficiency of the filters for total sulfate. At most, a small percentage of the stratospheric sulfate was present as the ammonium salt. At least about half of the ammonium ion found on the impactors could have resulted from reaction of the collected samples with ammonia in tropospheric air.

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R. D. Cadle
,
R. Bleck
,
J. P. Shedlovsky
,
I. H. Blifford
,
Jan Rosinski
, and
A. L. Lazrus

Abstract

An extensive series of experiments is being undertaken to determine the concentrations and transport of trace atmospheric constituents in the stratosphere and troposphere in the vicinity of jet streams during tropopause “folding” episodes. The first experiments were undertaken in March and April 1968 and the results are described and discussed. Both propeller-driven aircraft and U. S. Air Force jet aircraft were used, supplemented by ozonesonde and lidar measurements. Trace constituents investigated included ozone, sulfates, various cations, freezing nuclei, aerosol particles in general, and radioactive nuclides. A high, positive correlation was observed between the intensity of radioactivity and the sulfate concentrations. Relative concentrations were consistent with transport of air from the troposphere to the stratosphere on the anticyclonic side of the jet stream. Concentrations of freezing nuclei were on the average much lower but much more uniform in the stratosphere than in the troposphere.

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