Precipitation (inches) it 0 T Jan. Figure 32. | T ' Mar. q T ' ft May July Month of the year T | Sept. qT T Nov. Average monthly rainfall at Bikini Atoll from 1982 through 1987. Our measurements of resuspension in the coconut grove on Bikini Island were made in 1978. Since then, the coconut grove has matured and the coconut trees have increased in height; as a result, most of the wind is directed up and over the coconut canopy. In addition, the ground cover has increased, so that the mass loading at breathing height might currently be less than the measurements taken in 1978. We also observed on Bikini Island that the Pu specific activity of material on the air filters exceeded the specific activity of Pu in the top 5 cm of surface soil, which is the source of the resuspended material. As a result, we developed the concept of the enhancement factor (EF) to account for the increased activity in the respirable-size resuspended material. In addition, people in the process of their daily activities often produce a dust concentration in their immediate environment that exceeds the dust mass loading measured in the open field. Personal dosimeters (air samplers) were worn by our field teams performing various tasks to determine the personal dosimeter enhancement (PDE). 62