SOME PROBLEMS OF ATMOSPHERIC CHEMISTRY 
hydrogen peroxide could be detected only in the im- 
mediate vicinity of fireplaces and therefore cannot be 
considered an oxidizing factor of practical importance. 
RESULTS FROM THE CONDENSATION METHOD 
This method takes into account merely those con- 
densation nuclei around which water droplets form by 
condensation, not only during the slight water-vapor 
supersaturations and pressure fluctuations possible in 
the free atmosphere, but also even before saturation 
is attaimed. The condensation nuclei thus represent 
distinctly hygroscopic substances, that is, those sec- 
ondary constituents of the air which possess the most 
intense molecular attractive forces (capillary forces). 
Their radii range,in order of magnitude from 1077 cm 
to 10~* cm. In the following discussion the averages and 
fluctuations obtained thus far will be considered; the 
data are given in Table II. 
Tasie II. Surrace CoNCENTRATIONS OF NuCcLEI-FORMING 
SUBSTANCES IN EUROPE 
Substance Region Mean (ug m7) | Range (ug m-) 
Mg Mainland and coast 3.1 0.0- 65.2 
cl Mainland and coast Be) 0.0-964.8 
SO4 Mainland and coast 2.6 0.0-732.0 
NH; Mainland 7.9 2.5- 54.4 
NH; Island of Norderney 5.5 0.0- 25.0 
NO, Mainland 1.0 0.0- 21.6 
NO» Island of Norderney 0.14 On0> ae 
02 0.0 0.0- 0.0 
HCHO Mainland 0.5 0.0- 16.0 
Chlorine of the Air. Contrary to previous concepts, 
it is not the sulfates but the chlorides that represent the 
principal mass of nuclei-producing substances in 
Europe, except in the more populous regions. 
In contrast to the spray theory, according to which 
sea salts are transported chemically unchanged in drop- 
lets of sea water, lose their water in dry air, and function 
subsequently as condensation nuclei far inland, it was 
possible to determine that a sharp chemical disintegra- 
tion of the droplets takes place very soon after lifting 
from the ocean surface [16, 17]. The ratio of the Cl- 
to the Mg**, K+, and Nat on the high seas, as deter- 
mined during submarine voyages, does not correspond 
even approximately to the ratios in the sea water, 
where, for example, a constant weight ratio, Mg/Cl = 
1/15, is found. The chlorine in the gaseous phase appar- 
ently escapes rapidly from the droplets by autocata- 
lytic processes and under the influence of O3 [6]. However, 
the chlorine evidently remains in this state only a short 
time [16, 17]. Under the influence of light quanta it is 
partly converted with hydrogen into HCl, which, being 
hygroscopic, produces condensation nuclei, and is partly 
oxidized to ClO2, according to data obtained on islands 
in the North Sea. This ClO, is likewise productive of 
condensation nuclei and dissociates in the dissolved 
droplets to form HClO, or HCl and HCIO 3. These 
alternations between the dissolved and gaseous phases 
probably occur in the air in the nature of a continuous 
cycle. In the eastern regions of central Europe Cly is 
occasionally absent from the air, even in the form of 
1131 
chlorides. The invasion of maritime air into these re- 
gions (Tatra and Riesengebirge) can often be detected 
by the fact that chlorides appear and that their amounts 
increase rapidly. The alkali ions and alkaline-earth 
ions, which are enriched by the liberation of Cl, from 
the droplets, do not show such a cyclic phenomenon. 
They combine with CO. and diminish rapidly by pre- 
cipitation. 
Nitrogen Compounds of the Air. Nitrites and nitrates 
appear to be quantitatively dependent on eleetrical 
discharge phenomena, on the heating and humidity of 
the ground (bacterial activity), and on pressure fluctua- 
tions [11, 12]. In the air of high mountains they repre- 
sent important condensation nuclei (nitrite production 
from rock formations in the Andes or in the Atacama 
Desert). In contrast, they exist only to a minor degree 
in maritime air. 
Ammonia or ammoniacal compounds appear to de- 
pend quantitatively on anaerobic processes of decom- 
position, combustion processes, and periods of inflores- 
cence (¢.g., of the Prunus genus) [12], and, next to 
chlorides, represent the largest group of substances 
which form condensation nuclei over the European 
continent. They occur over the entire continent without 
exception. Only on sand islands having sparse vegeta- 
tion and human population are zero values found in 
maritime air. In the case of land winds that have 
traversed the sea, low values are also encountered. 
Formaldehyde of the Air. Formaldehyde was found 
to be an index of the presence of incomplete combustion 
processes. No indication of a transportation by subsi- 
dence from high altitudes, a process assumed by Dhar 
and Ram [21] and by Groth and Suess |27], could be 
found up to the present time. Some of the results have 
been published elsewhere [28]. 
Tasie III. Averace pH Vatur or THE AnROSOL AND MEAN 
REDUCTION VALUES OF THE AIR 
Mean reduc- 
2 tion value 
acation ease msl Mean DE fective 
deficiency 
in wg m=) 
Nebelhorn, Alps............./1000-2000 3.4 = 
High Tatra, Slovakia........ > 1000 4.0 = 
Ober Schreiberhau, Riesen- 
PODITMe nats dari ae 50 4.7 160 
Berlin hey sen sae Pk 25 6.2 1600 
Island of Norderney, North 
Sede feet HSPs coche 10 4.6 — 
Diesel engine rooms......... _— 5.2) 18,800 
The pH Value of the Aerosol. The mean pH value 
of the condensation nuclei seems to be a function of the 
mass ratio of the hygroscopic acidic and basic second- 
ary constituents in each case (see Table III). In high 
mountains (1000 m above sea level), the strongly acidic 
average pH value (bactericidal for pathogenic bacteria) 
is due to the decrease in ammoniacal substances, so 
that without the attendant buffer effects the nitrite 
present in the droplets is able to dissociate strongly. 
In the mountains at an altitude of only 700 m the 
mean is forced into the weakly acidic range (which 
