Abstract
Concentrations of 90Sr and 137Cs in an airborne dust at altitudes of 10km and 6km were measured. Samples were collected on filter paper with the dust sampler mounted on an aircraft over the northern, middle and western parts of Japan, during the period between October in 1972 and September in 1975. And the following results were obtained;
1. The concentration of 90Sr and 137Cs changes in a seasonal variation showing a tendency of increase from October, reaches its maximum from February to April, decreases gradually afterwards reaching its minimum from July to September.
2. The regional distribution for the nuclides tends to be high in the northern parts and low in the western parts.
3. There is about 1/10 difference in the value of each concentration between the altitudes of 10km and 6km.
