characteristic of the alkaline solution of Ca(OH),, bnt the pH of the water-surface burst fallout was about the same as ocean water, 7.5 to 7.7. Approximately 25 percent of the particulate matter was not radioactive. The e-a)aation of this number is uncertain due to the possible introduction of dust into collector trays. One sample from Site Huw indicated that 33 percent uf the activity was assoviated with particles greater than 225 microns in diameter. A iarge fraction of the activity wae also found to be associated with very~small particles, but these could have veen the result of particle break-up in the sizing procedure. Radioautographs of partic'va revealed ‘ooo Topote —t- — —~4—tofu ot. Joy deep Particle Diameter, microns tee 10 ao 00801 O02 O8 . 2 3 10 200 (B40 6D 80 O76 a) a6 98 oe 97 00.8 888 Oe oo 08 Percentage of Particlas with Smatler Diameter Figure 3.11 Cumulative particle-size distribution. some with activity only on the surface, others with activity irregularly distributed, and still others that were radioactive throughout. The angular~shaped particles usually had the activity on the surface, whereas the uniformly radioactive particles had a sphercidal shape. The average particle density was 2.4 gm/cm’ Samples collected on aerosol filters after Shot 1 revealed the same types of particulate: angular with surface activity and spheroidal with a volume-distributed activity. A water leaching only removed 24 percent of the activity, whereas about 96 percent was removed by weak acetic acid. Aerosol samples were collected aboard the ships (YAG's) stationed {n the fallout zone during Shots 2 and 4. The activity appears to have arrived principally in water droplets. Chemical analysis of the samples was used to separate the fallout composition into coral, sea~water, and device contributions by evaluating the Ca, Na, and Fe contentof 52