Abstract:
The specific activity of ⁶⁵Zn (nanocuries ⁶⁵Zn/g total Zn)
was determined in various organs of the common coastal mussel,
Mytilus californianus Conrad, collected from six locations along
the Pacific Coast. These organs included the gills, mantle, foot,
reproductive organs, adductor muscle, and viscera. After ashing
and dissolving with nitric acid (8 M), each tissue was analyzed for
⁶⁵Zn by gamma-ray spectrometry. The determination of total zinc
concentrations of the various organs was accomplished by atomic
absorption spectrophotometry as well as by neutron activation
analysis.
Variable amounts of both stable zinc and radioactive ⁶⁵Zn
were observed within the specific tissues from a given location.
The ⁶⁵Zn specific activities of the tissues of organisms from a
particular station however, tended to be uniform, at least within
the uncertainty of the measurements. Both radiozinc and ⁶⁵Zn
specific activity decreased with distance from the Columbia River
mouth, whereas the stable zinc tended to remain uniform for a
specific tissue. Tissues high in radiozinc were also high
in stable zinc and conversely.
An estimate of the input specific activity from the mussel'
environment (food and/or water) was calculated from a simple
model resulting in a value similar to zooplankton values sampled
from within the Columbia River plume.
Comparison of the concentrations of zinc determined by
neutron activation with those determined by atomic absorption
spectrophotometry indicated a linear relationship between the
two methods. Results of atomic absorption measurements were
approximately 27% larger than the results of neutron activation
analysis, indicating the presence of a systematic error. The
higher values attained by atomic absorption are attributed to
evaporation during storage of the ash solution which would lead
to an increase in zinc concentration. In considering the two
methods of analysis, economy of both time and expenses favors
the atomic absorption method over that of neutron activation.
