216
PERKINS, THOMAS, AND NIELSEN
material is compared with the total ‘41 content of the air in Fig. 14,
The fraction of airborne ‘*I in the particulate form ranged from about
10 to 90%. The peak '*4I air concentration in October 1962 was accom-
panied by a definite peak in the fraction of particulate activity (~ 90%),
whereas the peak '!] air concentration in November 1962 was accom-
panied by a minimum of particulate '!1 (~ 12%). Presumably, these
extreme differences in the fraction of particulate *'I are due to the
nature of the nuclear detonations responsible for these peaks in the
1317 activity. The nature of the gaseous }*4I in fallout was investigated
by placing a 2-in.-thick silver-mesh (1 by 20-mil silver-plated copper
mesh) bed in the air-sampling head between thefilter and the charcoal.’
Laboratory experiments had shown that for the flow velocities used
this bed was 95 and 99% efficient for removal of I, and HI, respec-
tively. It was observed that less than 10% of the gaseous '*'I was held
by the silver mesh; therefore greater than 85 to 90% of the ‘I is ina
form other than I, or HI and is presumably present as organic iodides.
LC A
tr
Ou
Oo
Gs
L
A TOTAL "1
‘
a
:
>
~
0.01
a
E
a
r—
t
0.001
-
\
=
of
*
us
=
—
—
"oe
5
=
10
=
1.0
=
o
.
So?
°
° qj
eo?
2
‘Oye =
%
°
5
9
7
P.007¢ Se
am
or
@
8
131;
oF
92 0
“
#8 0
=
° dep,
a°@ bo
°
3°
o
ao°
co
8 "ote
7
oT
°
3°?
° sf =
a9
7
4
>
a
Po
DETONATIONS
|
>10 MT
— Ta — U.S.S.R.
U.5.
|
1-10 MT
|
< 10 MT i
|
< 20 KT
o,°
o
—_
a %,%
0°88
—;
5
°
<
im
poo
100 &
@,°o
;
oq
oa
aes .
°
:
4
ar
°
Z
4
ao
8-DAY 91) HALF-LIFE
1961
|
i
A7
| }| eeS|
MyM Ma
\
O'TNi ol ste tM aimi
7
|
a|
.
" a
a
HHalll
ebl it! i
{
:
i|
1]
yl
I
1962
i
slats
!to'tn!'!
Fig, 14—Physical form and abundance of airborne *9'1.
ee
op