RESULTS AND DISCUSSION
Individual particle data are listed in Appendix A. The results of
particle measurements are summarized in Table 1, where the distribution
and activity characteristics of the size and size-type group of each sample collection are listed. The small number in some of the groups emphasizes the difficulties in obtaining sufficient single particle data and
indicates that the reliability of such data is low. Particles smaller
than 31 yp were not studied in the YAG-40-Shot A group - probably because
of investigator bias toward larger sizes and the difficulties of sizing
small particles imbedded in grease.
Particle Size Distribution
For the size distribution studies, it was not possible to mark a
tray area completely at random because of practical considerations. Areas
selected were limited to those having 10 to 20 particles sufficiently well
spaced to permit pick-up. A studyl° has shown that the quantities of fall-
out deposited at the different collector positions in the standard platform were affected by varying degrees of wind bias; for this reason the particle size distribution data as given may not be representative of the geographical location. Since the effects of wind bias were lower in the case
of the YAG-40-Shot B sample, this collection is considered to be reasonably
representative of location.
Activity Characteristics
The most notable aspect of the activity data is the wide range of
activities associated with each size group and size-type subgroup. Though
activity ranges were extensive, variation through each range was nearly
continuous; however, in a number of cases, extreme low or high values
occurred. The activity characteristics of each size group of each collection are given in Table 1 in terms of minimm activity, maximum activity,
median activity, and group activity (except YAG~40-Shot A) - which is
obtained by summing individual particle activities. Due to the lower frequencies of the size-type subgroups, only their median activities and subgroup activities are listed.
As discussed in the following section, there are indications that the
activities of a size-type subgroup may follow a normal distribution, in