Abstract
The ionizations by the beta and gamma-radiations near the ground were measured in and around Nagoya during the last four years (1963-1966). Although the ionization by the beta-radiation decreased gradually from 1963 through 1966, that by the gamma-radiation did not decrease remarkably. Therefore, the contribution of the beta-radiation to the ionization of the air exceeded that of the gamma-radiation from 1963 through 1964, while the latter exceeded the former in 1966.
In general, the ionization by the beta-radiation from the ground surface covered with the grass exceeded that from the ground covered with no grass because of the fallout radioactivity accumulated in the leaves and roots of the grass.
