1.2 Precipitation Collections for Radiostrontium and Radiobarium in precipitation collections, two collectors are simultaneously exposed during dry and rainy weather. The collection period terminates immediately after a precipitation or after a week of no rainfall. 1.21 Pittsburgh, Pennsylvania Since February 1955, precipitation collections have been made by Nuclear Science and Engineering Corporation in galvanized tubs (exposed surface 2.58 rt? per tub). Table 4, up-dates the Pittsburgh precipitation data in HASL-5l. Pigure 4 depicts cumulative Sr?9 fallout. The cumulative error terms represent the standard error of duplicate analyses. Until February 1957, the contents of the two tubs were combined resulting in one analysis for the collection period. Since February 1957, the contents of each tub have been analyzed separately. Precipitation values were obtained from the United States Weather Bureau until June 19, 1957. Since then, precipitation has been measured by Nuclear Science and Engineering personnel using a Fisher # 1-2)2-5 United States Weather Bureau typo rain gauges ~ 13 -