ANOMALOUS 235U/238U RATIOS AND METAL ELEMENTS DETECTED IN THE BLACK RAIN FROM THE HIROSHIMA A-BOMB

Abstract

Contents of black rain from the A-bomb are important to clarify the health and environmental hazard caused by nuclear warfare. We analyzed the only existing physical remains of the black rain from Hiroshima A-bomb (Little Boy), a plastered wall with black streaks. Excess 137Cs and anomalous 235U/238U ratios detected in the black residues on the wall confirmed that the black streaks on the wall originated from Little Boy. The results also showed that excess 235U could be used as a fingerprint to clarify the distribution of materials discharged from Little Boy into the environment. High concentrations of lead and zinc, which may have caused a degree of heavy metal pollution in the area where the rain fell, were also detected in the black rain sample.