THE PROBLEM OF THE APPLICATION OF TOXIC CHEMICALS IN THE FORM OF AEROSOLS

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP80-00809A000700070284-8
• Release Decision: RIPPUB
• Original Classification: C
• Document Page Count: 6
• Document Creation Date: December 22, 2016
• Document Release Date: August 19, 2011
• Sequence Number: 284
• Publication Date: July 14, 1952
• Content Type: REPORT

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INFORMATION FROM
FOREIGN DOCUMENTS OR RADIO BROADCASTS CD NO.
FOR OEFiCIAL USE Oiu
CLASSIFICATION -CONFFDENTIAL-
SECURrrr-IrwoRMATION
DATE OF
INFORMATION 1951
14
WHERE
PUBLISHED Moscow
DATE
PUBLISHED Jul 1951
LANGUAGE Russian
Tilt CCCOII.OT "STAIRS INFO .OATWO AlNMNS TOt RATICOAL .["I"I
Or TOt OIIITC0 5T... 01}111 TII. .un11S Or INNONAC, ACT IN
O. t. C.. 11 A..... AS AO.0000. IT? T.Altl.ltt.O. YO ... .... o
NI.IT1O IF LAW IN KMOOCTIOIN Or TOIL IONS OII PIONINITIN. IS PRO'
DATE LIST. J' Jul 1952
Doklsd Vseso zno Ordena Lenina Akademii Sel'skokhoz the
Nauk imeni V. I. Lenina, Vol XVI, No , 1951, pp 3 -3
THE PROBLEM OF THE APPLICATION OF TOXIC CHMUCALS
IN THE FORM OF AEROSOLS
A. G. Amelin, Dr Tech Sci
Sci-Research Inst of Fertilizers and Insectofungicides
- 1 -
ATI/~11 --C D> OR-OFnCItt USE ONLY
I.. V1JJI rI IJIT + 1 V AT _
DISTRIBUTION
STAT
STAT
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fligurea referred to are appended
Spraying anC dusting with toxic chemicals of large areas of agricultural
fields and forest plantings to combat pests is expensive because the rate of
utilization of the chemicals is low. Furthermore, such methods have the fol-
lowing disadvantages.
Relatively large drops are formed in spraying, so that the toxic chemical
is not distributed uniformly over the surface. In dusting, solid particles of
the dust do not adhere to the surface of the plants and are blown off by the
viral. Addition of substances which improve adhesion complicates the technology
of the production of materials for dusting and promotes their caking.
Treatment of crops is made considerably cheaper and, at the same time, is
simplified by the use of liquid-in-air aerosols. Dispersion of a liquid is
easier to accomplish than that of a solid material, so that a liquid toxic
chemical can be dispersed immediately before its application. The droplets of
liquid, after reaching the surface of the plant, stick to it and thereupon
spread and penetrate into the surface. In this manner, the uniformity )f cover
age of the surface with the toxic agent is improved, and penetration of the
toxic agent into the organism of insects is assured when the insects feed on
the poisoned plant or come in contact with its surface.
To obtain the most uniform coverage of the surface, it is desirable to use
an aerosol cloud consisting of the smallest possible drops. However, in some
cases, we are compelled to increase the dimensions of the drops to improve their
deposition on the surface being treated.
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Enclosed spaces, open air spaces, 'r field and forest sections may be
treated. Depending on which of these objectives is involved, the degree of
dispersion of the aerosol cloud =at be varied, and this determines the method
of obtaining the liquid-in-air aerosol as well as the way in which it is ap-
plied.
The application of liquid-in-air aerosols is particularly effective for
the treatment of large areas and results in the highest efficiency under' these
circumstances. However, one cannot bring about a directed movement of drops
under such conditions because covering of the surface with the toxic agent
takes place as a result of precipitation of drops of the liquid from a moving
cloud. Hence, precipitation of the drops depends on their size, velocity of
the wind, velocity of rising currents of air, etc.
consists The cprecipitation of drops in the layer of air next to the ground
components which are added together: (1) Stokes' velocity of
precipitation, which is brought about by the force of gravity; and (2) the tur-
bulent velocit of precipitation, which results from turbulent expansion of the
air stream jj. Furthermore,
W = S' = y a (1)
where S' is Stokes' velocity of precipitation; v, velocity of the wind; and o(,
a coefficient which characterizes the irregularity of the wind.
In Figure 1, both components are plotted as functions of the velocity of
the wind. The data of Figure 1 applies to drops with a density up to 1 g/cm3.
Precipitation of suspended particles under the action of the force of gravity
takes place only when the atmosphere is in a state of viscous calm. Periods
during which the atmosphere is in this state are the lees prolonged, the higher
the velocity of the wind. Therefore, the Stokes velocity of precipitation
drops when the velocity of the wind increases.
It can be seen from Figure 1 that when the velocity of the wind is higher
than 2 m/sec and the drops have a diameter smaller than 120 micron (this is
the size usually applied under practical conditions), the turbulent velocity
of precipitation greatly exceeds the Stokes velocity. Under these corditions,
the Stokes velocity does not have to be conetdered at all.
This means that in a strong wind, all drops, independently of their di-
mensions, precipitate with the same velocity. C..ie might think that this cir-
cumstance would facilitate designing of equipment for the production of liquid-
in-air aerosols, but this is not the case at all.
In a strong wind the quantity of matter deposited per unit of area under
the action of the turbulent velocity of precipitation drops logarithmically
with the distance from the aerosol generator, i.e., a very large quantity of
matter precipitates in the vicinity of the generator, and this quantity drops
sharply as the distance from tl.e generator increases.
The quantity of matter that precipitates on a surface is given by the
equation
A = CW (2)
where C is the concentration of she matter in sir and W, the velocity of pre-
cipitation of the particles suspended in air.
In a strong wind, and for small drops in any wind, the concentration of
matter in an aerosol cloud is given by the following equation n7:
STAT
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~i I Q i t 3z1?.. r~^ ..C
where Q is the quantity of matter dispersed per unit of time; v, the velocity
of the wind; 1, the distance from the generator; h, the height from the ground
at which the aerosol is released; and a and m are constants.
Using this equation, we carried out sample calculations, the results of
which are shown in Figure 2. These results show that the quantity of precipi-
tated matter drops rapidly with increased distance from the generator. Further-
more, the smaller the height from which the aerosol is released, the more
sharply the quantity of precipitated matter diminishes.
The curves shown on Figure 3 represent the quantity of matter precipitated
on the total surface between the generator and some distance 1 from it, if this
quantity is expressed in percent of the total quantity of matter which has been
dispersed. The values used have been computed from Shleykhovskiy's equations D1 7.
As can be seen from Figure 3, the total luantity of ma'.ter which precipi-
tates on the surface is small. With a wind velocity equal to 2 m/sec and
height of aerosol release equal to 3m, only 40% of the dispersed matter pre-
cipitates up to a distance of 200 m from the generator. When the height of
aerosol release is reduced, the completeness of precipitation is somewhat in-
creased. Thus, when the aerosol i., released at a height of 1 m, the degree of
precipitation reaches 55%, but the main quantity of liquid precipitates near
the generator, i.e., the uniformity of coverage diminishes.
In the calculations cited, it has been assumed that a drop which reaches
the surface precipitates on it. Actually, a part of the drops rebounds from
the surface and is carried away by the air current. The coefficient of reflec-
tion which characterizes the proportion of drops that reboun?i increases when
the ~_locity of the wind becomes greater and the diameter of the drops smaller.
For that reason, the degree of precipitation under field conditions will be
lower than that shown in Figure 3, and its eduction will depend on the wind
velocity and the drop sire.
For drops which have an electric charge, the coefficient of reflection
must be lower, so that the completeness of precipitation will be greater in
this case.
The most favorable conditions exist in the case of a cloud consisting of
drops with a diameter of about 100 microns. In a weak wind (up to 1 m/sec),
such drops precipitate mainly under the effect of the force of gravity. Theo-
retically, one may create an aerosol cloud having such a dispersion of drop
sizes that a uniform quantity of matter per unit of area will be precipitated
throughout the whole extent of the surface being treated. Under such condi-
tions, one may achieve a practically complete precipitation of the dispersed
liquid on the surface that has been treated.
The advantages presented by large drops give reason to assume that clouds
consisting of large drops will be widely used whenever the surface under treat-
ment must be covered by a large quantity of the toxic agent per unit of area.
The velocity of precipitation of drops under the effect of the force of
gravity is given by the following equation L 1 7:
W _ pp gD2
STAT
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where W is the velocity of precipitation of the drops; P, a coefficient the
value of which depends on the velocity of the wind; J , the specific gravity
of the liquid; g, acceleration of the force cf gravity; tk , viscosity of the
air; and D, diameter of the drops.
Knowing the velocity of precipitation of the drops, it is easy to calcu-
late the distance from the fog or aerosol generator to the spot where the drops
precipitate by using the expression
by
K
where 1 is the distance from the aerosol generator; h, the height from the
ground at which the aerosol cloud is released; and v, the velocity of the wind.
1 = 18 h?
PP
The quantity of liquid which precipitates per unit of time on the
is given by the expression
where Q is the expenditure of liquid per unit of time, i.e., the output of the
generator; q, the degree of coverage, the quantity of liquid per unit of area;
and u, the velocity of displacement of the generator along the section being
treated. If the number of drops precipitated on the section between the dis-
tances 0 and 1 is designated by n, the quantity of liquid precipitated on the
section dl will amount to
dQ = ?rte Y do . (8)
Equating the right sides of equations (7) and (8), and substituting the
value of dl obtained from equation (6), we get, after differentiation,
do _ 216.1uhv? D 6 _ AD 6
dD Pf2m~
lg dda = lgA - 6 lgD
Equation (10) is the equation of a straight light for which tgoc = -6,
which corresponds to a slope angle oC ? 990281. Under the assumed conditions,
the magnitude of this angle does not depend on the velocity of the wind, the
nature of the substance being dispersed, the height at which the aerosol cloud
has been released, etc.
Equation (6) permits determination of the dimensions of drops of which
the aerosol c_oud should consist, while equation (10) indicates the number of
drops which is necessary so that the total volume of drops per unit of area be
uniform throughout the extent of the area being treated within a given distance
from the generator. Sample calculations show that to treat a section extending
over 100 m at a wind velocity of 1 m/sec and at a height of release of the
aerosol cloud equal to 4 m, the average surface diameter of the drops should
comprise 114 microns.
STAT
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Conclusions
1. Whenever an adequate quantity of a toxic chemical is to be precipi-
tated per unit area of the surface being treated, the use of an aerosol cloud
consisting of drops having a diameter smaller than 30 microns is inadvisable;
such drops will be carried away too far from the generator, so that the chemi-
cal of which they consist will be lost.
2. The treatment of large areas with aerosol clouds should be carried
out in a wind which is not particularly strong, i.e., one that has a velocity
up to 1 m/sec. A wind of this strength usually occurs at night and in the
morning; consequently, this is the ?,st favorable time for releasing the aero-
sol cloud.
1. G. Ya. Bey-Bienko, N. N. Bogdanov-Karpov, B. Yu. Fal'kenshteyn, G. A.
Chigarev, V. N. Shcheglov, Sel'skokhozyaystvennaya Entomologiya (Ag-
ricultural Entomology), Ogiz - Sel'khozgiz, Moscow/Leningrad, 1949.
2. G. V. Sheleykhovskiy, Z..dymleniye Gorodov (Blacv.ening of Cities With
Smoke), Ministry of Communal Management, Moscow/Leningrad, 1949.
3. Ye. N. Taverovakiy, paper in collection entitled"Novyye Ideye v Ob-
lasti Izuchen'_ya Aerosoley,(New Ideas in the Field of Investigation
of Aerosols), edited by B. V. Deryagin, Corresponding Member, Academy
of Sciences USSR, published by the Academy of Sciences USSR, Moscow
Leningrad, 1949.
jppended figures follo'.7
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0.1 aB 1.2 26 20
Figure 1. Velocity of Precipita-
tion of Drops, Depend-
ing on the Velocity of
the Wind. 1 - Turbu-
lent velocity of pre-
cipitation. 2,3, and
4 - Stokes velocity of
precipitation for drops
having diameter of 50,
100, and 150 ? , re-
spectively.
ti a
X74
b
Figure 2. Quantity of Substance
Precipitating per Unit
of Area Being Treated
at Wind Velocity of 2
m/sec. 1 - Aerosol re-
leased at height of 1 m.
2 - Aerosol released at
height of 3 m.
0 40 M ,n !O 740 X4
o:,re,.ce A... ye--o- i. ..,
Figure 3. Degree of Precipitation
at Wind Velocity of 2
m/sec. 1 - Aerosol re-
leased at height of 1 m.
2 - Aerosol released at
height of 3 m.
STAT
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