Table 3 Element-specific ecological half-times parameters of the contribution to the external dose rate 1 m above ground from fallout in terms of a double exponential decay function (Eq. 9) for the elements represented in the nuclide vectors in Table 2. N/A = Not applicable.

Nuclide	c_short,i	T_eco,i,short (y)	T_eco,i,long (y)
^110mAg	0.63	0.6	22.7
¹⁴⁰Ba	0.63	0.6	22.7
⁸²Br	0.63	0.6	22.7
¹⁴⁴Ce	0.63	0.6	22.7
¹³⁴Cs	0	0.6	3.2 or 6.7 or 15
¹³⁶Cs	0	0.6	3.2 or 6.7 or 15
¹³⁷Cs + ^137mBa	0	0.6	3.2 or 6.7 or 15
¹³¹I	1	0.125*	22.7
¹³²I	1	0.125	22.7
¹³³I	1	0.125	22.7
¹³⁵I	1	0.125	22.7
¹⁴⁰La*	0.63	0.6	22.7
⁹⁹Mo	0.63	0.6	22.7
⁹⁵Nb*	0.63	0.6	22.7
⁹⁷Nb	0.63	0.6	22.7
¹⁴⁴Pr*	0.63	0.6	22.7
¹⁰³Ru	0.63	0.6	22.7
¹⁰⁶Ru + ¹⁰⁶Rh	0.63	0.6	22.7
¹²⁵Sb	0.63	0.6	22.7
¹²⁷Sb	0.63	0.6	22.7
⁸⁹Sr**	N/A	N/A	N/A
⁹⁰Sr + ⁹⁰Y**	N/A	N/A	N/A
^99mTc	0.63	0.6	22.7
^131mTe + ^129mTe + ¹²⁹Te	0.63	0.6	22.7
¹³²Te	0.63	0.6	22.7
¹³²Te + ¹³²I	0.63	0.6	22.7
⁹⁵Zr	0.63	0.6	22.7

*Based on the initial slope of ambient equivalent dose rate data from Jönsson et al.⁷.
**For the pure beta-emitters ⁸⁹Sr and ⁹⁰Sr/⁹⁰Y, the bremsstrahlung generates an external dose contribution that will be ecologically damped more rapidly than for gamma emitters. According to Kumar Sahoo et al.⁴⁴ radiostrontium migrates at a rate of ~1 cm y⁻¹ which, in combination with data from the ICRP¹⁴ suggests that the bremsstrahlung component decreases rapidly (T_eco,Sr,short < 1 y).

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