40
4.3 Analyses
4.31 Radiometric analyses of 1958 samples.
The gross
beta radioactivity (corrected for K40) of the plated samples
was determined with an Anton Laboratories end tube, mica
window model,
type 1001-T detector with 2-inch lead shielding
in conjunction with a Nuclear-Chicago Model 181-A scaler,
C-110-B automatic sample changer and C-110-B printing timer.
The plated tissue samples were then pooled into groups
distinguished by taxonomic family and habitat, and an estimate of the relative total gamma radioactivity for each group
was determined from a 10-minute count,
Model 1810 single channel analyzer,
using a Nuclear Chicago
Model DS-3, well-type
scintillation counter with a 2x2-inch,
thallium-activated,
sodium iodide crystal, C-111 printing timer and a Tracerlab
superscaler.
Spectrometric analyses of gamma radiation were conducted
for the three groups having the highest total gamma activity.
A Radiation Counter Laboratories 256-channel analyzer, Model
20609, with a 3x3-inch, thallium-activated sodium iodide crystal was used for this purpose,
4.32
1959 samples
4.321 Radiometric analyses.
individual specimen
The ash from each
(spread in a thin film over the bottom of a