THE STUDY OF THE BEHAVIOR AND SIGNIFICANCE OF CERTAIN RADIOACTIVE ISOTOPES FOUND IN THE SEWAGE TREATMENT PLANTS OF SELECTED CITIES Summary of Findings for I960-1961 Part A: Comparison of the Hyperion Plant of the City of Los Angeles with Eleven Other Treatment Plants

摘要

This report describes measurements of traces of certain radioactivities made between 1958 and 1961 at the Hyperion Treatment Plant of the City of Los Angeles and in samples from 11 other selected sewage treatment plants. Only gamma ray emitters were studied, and most attention was given to the behavior of cesium-137, one of the long-lived fission products. However, other isotopes measured in sewage include cobalt-60, zinc-65, iodine-131, radium-226, thorium-232, and potassium-40. Special methods have been developed for conveniently determining the low levels of radiocesium now found in tap water and in sea water, and the cesium-137 activity found in Hyperion sewage has been compared with that now present in the coastal waters and in the waters of the open Pacific. No concentration believed hazardous has been discovered in ally of the treatment plants, but the effects of the new usage of artificial radioactivities are already discernable above the natural background radio¬activities in many sewage specimens, as was the reappearance of young fallout activities only a few weeks after weapons testing was renewed.