Effective dose-rate [nSv h⁻¹ Bq⁻¹ kg]; ambient dose equivalent rate, [nSv h⁻¹ Bq⁻¹ kg]; and air kerma rate, [nGy h⁻¹ Bq⁻¹ kg], coefficients for nuclides of the radioactive decay chain in secular equilibrium uniformly distributed to an infinite depth in the soil.

Decay chains headed by 232Th, 238U, and 235U are the thorium, uranium, and actinium series shown in Fig 2, respectively. The 137Cs chain indicates the secular radioactive equilibrium between 137Cs and 137mBa.