240
LOWDER, BECK, AND CONDON
Table 2—SUMMARY OF SURVEY RESULTS IN 1962 TO 1964
— Survey area
New York
South and west
North
New York City
Date
Aug.
Aug,
Aug,
May
1963
1964
1963
to
Sept, 1962
Mayto
Sept. 1963
Jan, to
Sept. 1964
No, of
locations
35
g
19
3
Gamma dose-rate range, wr/hr
Natural
Fallout
5 to
5 to
4to
5 to
3
0.5
3
3
7
7
8
10
to
to
to
to
4
1
5
5
3
7
4tos
3
7
0.5 to 2
Vermont
July 1962
26
4to8
2 to 3
New Hampshire
July 1962
May 1963
Sept. 1963
May 1964
39
5
10
4
6
6
6
7
15
8
15
11
2to3
3 to 5
3 ta 5
lto 2
Southeastern United States*
South Carolina
North Carolina
Apr. 1963
Apr. 1963
Apr. 1963
§
6
2
3 to 7
3 to 10
15 to 19
4to7
4to7
2to4
Oct,
Oct.
Oct.
Oct.
1962
1962
1962
1962
6
4
3
9
6 to 8
6 to 8
4
3 to 5
2to5
3 to 4
2
} to 4
Oct.
Oct.
Oct.
Oct.
Oct.
Oct.
1962
1963
1962
1963
1962
1963
6
6
6
3
9
10
4to
5 to
5 to
5 to
9 to
8 to
1 to 2
1
1 to 4
2to3
2to3
1 to 2
Oét. 1962
Oct. 1963
15
11
7 ta 9
7 to 9
Western United States
Black Hills, 8, Dak.
Seattle, Wash,
Olympic Peninsula, Wash.
San Francisco, Calif,
Nevada and Utah
Denver and Colorado
Springs, Colo.
Central United Statest
Aug. 1963
6
4to 8
to
to
to
to
8
8
9
9
14
15
4to5
3 to 6
2to 4
*Includes locations in Texas (2), Louisiana (1), Arkansas (1), Alabama (2), Tennessee (1), and Georgia (1).
tIncludes locations in Wisconsin (1), Minnesota (1), eastern South Dakota (4), Illinois (4), Kansas (3), and Missouri (2).
natural-gamma values fall between 5 and9 yr/hr, withan average reading for all 210 locations of 7 pr/hr. Higher observed natural-gamma
dose rates occurred in the Denver, Colo., andthe Conway, N. H., areas,
where average readings of 11 ur/hr were encountered. In both of these
regions, high thorium contents in the soils were primarily responsible
for the enhanced readings (e.g., see Table 1). In general, it has been
observed that *°K and the thorium series contribute roughly equally to
the natural-gamma-radiation field and the uranium series a somewhat
lesser amount, seldom amounting to more than 25% of the total. The
unexpectedly low uranium-Series dose rates at many locations are related to the removal of the parents of the gamma-emitting radioiso-
topes from the upper layers of the soil by the leaching of 7U and 7*°Ra
and the emanation of free 7“*Rn gas from the soil into the atmosphere.
The preceding discussion of natural-radiation measurements sets
into proper perspective the significance of additional gamma radiation
in the environment from man-made sources. In Table 2 it is note-