PREDICTION OF RADIONUCLIDE DEPOSITION
729
Fig. 2. The curves shown in this figure could be fitted to the general
equation
-D
—-H(a-—e™
(1)1
BS
c,
where D = four-week deposition, pc/m?
C, = average four-week air concentration, pe/m’
H = constant, m
a =factor to account for dry fallout onto the precipitation col-
lector, dimensionless units
b = elimination constant, (inches of rain)~!
r = four-week rainfall, in.
Actually, from the point of view of curve fitting, there waslittle
choice between a linear model and the exponential model shown by
Eq. 1. When the term “b” in Eq. 1 becomes small, the equation tends to
become linear, especially in the region of the measurements. This is
also true when the term ‘“H” becomes very large. The main reason for
choosing the exponential model was thatitconformsto what little theory
there is concerning the washout of particles from the atmosphere.’
10° =
T
T
T
r
0
t
1
l
|
2
3
RAINFALL, IN.
|
4
_--d
E
o£
T
|
T
S
x
~
=
S
=
5 0
1
(a)
2
3
RAINFALL, IN.
4
5
l
Li iiy
(b)
Fig. 2—Ratio of deposition, D, and
air concentration, C,, of gross beta
radioactivity vs. rainfall for fourweek sampling periods in the wesi-
ern Lake Erie area. (a) C, Dec. 27,
Liiutl
d
> lo
L
4a
|
0
]
|
|
|
2
3
4
RAINFALL, IN.
(c)
1962, to June 13, 1963; O, Dec. 26,
1963, to Mar. 19, 1964. (b) June 13
to Oct. 31, 1963. (c}) Oct. 31 to
Dec.
26,
1963, and
June 15, 1964,
wn
=
r
Mar.
19 to