Table 1 Mass concentrations of U, Th and K and external gamma dose rate in clay soil samples

U (ppm)

1.6-4.0

2.0-3.6

1.6-4.1

1.2-3.4

1.5-3.2

(3.2 ± 1.1)

(2.6 ± 0.7)

(3.1 ± 1.2)

(2.2 ± 1.0)

(2.5 ± 0.8)

²³²Th (ppm)

3.3-7.2

4.2-6.5

2.7-6.4

3.3-4.5

3.7-8.2

(5.3 ± 1.6)

(5.6 ± 1.0)

(4.2 ± 1.4)

(4.0 ± 0.5)

(5.7 ± 1.7)

K (%)

1.0-1.6

0.1-0.7

0.2-0.9

0.2-0.8

0.3-1.2

(1.3 ± 0.3)

(0.4 ± 0.3)

(0.5 ± 0.3)

(0.4 ± 0.2)

(0.7 ± 0.3)

Dose rate (nGyh^-1)

30.0-62.3

26.6-39.5

(22.5-43.7)

(20.6-40.7)

(21.8-49.9)

(48.1 ± 12.2)

(34.6 ± 10.2)

34.8 ± 6.2

27.2 ± 8.4

37.5 ± 11.3