DISCUSSION 255 
lentia, in contrast to Kinnvika, rainout and 
precipitation gave lines of identical slope. Cham- 
paign, Illinois, lies well to the right of the mean- 
atmosphere line, because of added sulfate from 
the continent, but this addition increases with 
higher chloride loadings, so that the line remains 
nearly parallel to the mean atmosphere line. 
Probably this can be explained by the absence 
of large nearby sources. It may also reflect the 
role of aerosols in the oxidation of the lower 
valence states of sulfur to sulfate. 
Summary—Examination of chloride-sulfate re- 
lationships in air and precipitation at a number 
of sites has led to the postulation of a three- 
source model for the composition of atmospheric 
particulate matter. It would be highly desirable 
to study all available data, in order to shed 
more light on these important correlations. It is 
possible that an index of the relative contribu- 
tion of urban and maritime sources can be de- 
vised, based upon the chloride-sulfate ratio of 
the environment. 
REFERENCES 
Byers, H. R., J. R. Stevers, anp B. J. Turrs, Dis- 
tribution in the atmosphere of certain particles 
capable of serving as condensation nuclei, Arti- 
ficial Stimulation of Rain (H. Weickmann and 
W. E. Smith, ed.) Pergamon Press, pp. 47-70, 
1957. 
Eener, H. ano E. Ertksson, Current data on the 
chemical composition of air and_ precipitation, 
Tellus, 7, 134-139, 1955. 
Eriksson, E., On the geochemistry of chloride and 
sulfate, The atmospheric chemistry of chlorine 
and sulfur compounds (J. P. Lodge, ed.), Geo- 
phys. Mono. 3, Amer. Geophys. Union, pp. 124— 
127, 1959. 
Harrison, W. K., Jr. ano J. P. Lopcr, Jr., Some 
measurements of oxidant levels at remote Cali- 
fornia sites, J. Air Poll. Control Assn., 8, 341- 
345, 1959. 
HotzwortH, G. C., Atmospheric contaminants at 
remote California coastal sites, J. Met., 16, 68- 
79, 1959. 
Larson, T. E., anp I. Herrick, Mineral composi- 
tion of rainwater, Tellus, 8, 191-201, 1956. 
Lopcg, J. P., A. J. MacDonatp, anp E. Viuman, A 
study of the composition of marine atmospheres, 
Tellus, 1960, in press. 
Discussion 
Dr. R. M. Schotland—Is there any possibility 
of stack gases from the ship contributing to the 
sulfur content of the samples taken at Station 
November? 
Dr. Lodge—I think not. We were simultane- 
ously measuring sulfur dioxide and found very 
little of it at any time. 
Dr. C. E. Junge—To me it was very interest- 
ing that you found these industrial sulfurs over 
the Pacific. I think I did not make my point very 
clear this morning when I spoke about the two 
hemispheres. Industrial sulfur, having only a 
lifetime of a few days, can therefore neither 
penetrate to the arctic areas nor into the tropi- 
eal regions. So it will normally remain in mid- 
dle latitudes, and was therefore found at Station 
November in the Pacific. The sulfur which we 
found in Greenland was natural, that is, we are 
pretty sure that the sulfur is primarily present 
as H.S which is oxidized and then washed out. 
This agrees with our findings that the residence 
time of the total sulfur which includes a natu- 
ral component, is much longer than ten days, 
which is approximately the residence time of the 
industrial component (SO.). 
Dr. M. Neiburger—In connection with this it 
would be very desirable to know the lifetime of 
the pollutants which go into the atmosphere. 
How many times around the Earth will they 
travel before they are washed out? My frank 
opinion is that industrial sources still are affect- 
ing Station November even though the aerosol 
will have to come all the way from Europe or 
with easterly winds all the way around from the 
United States. It seems to me this is also of in- 
terest in terms of the organics that might be 
acting as inhibitors to the freezing nuclei. It 
would be very valuable if somebody could make 
an attack on that question. 
Dr. Junge—1 definitely think this material 
circulates around the northern hemisphere once 
or twice before most of it is washed out. We have 
now a number of residence times from various 
sources which are not too accurate, but they 
give an approximate picture. We know that the 
lifetimes are of the order of 30 days in the tropo- 
sphere. They are shorter for some other pollu- 
tants, like sodium chloride formed from sea 
spray. Estimates show that they may be of the 
order of five to ten days. Of course, the water 
cycle has a ten-day turnover, so actually it looks 
as if most of the material which is readily washed 
out has approximately the same residence time 
