Instrumental Neutron Activation
Analysis of Tree Rings for Dendrochemical Studies
J.C. Schaumloffel, R.H. Filby, B.C. Moore 1996. Radioanalytical and Nuclear Chemistry:
207(2) p. 425-435.
ABSTRACT
Instrumental neutron activation analysis (INAA) was employed to determine zinc, cadmium
and potassium concentrations in the growth rings of ponderosa pine (Pinus ponderosa
Dougl.) trees growing along the shores of Lake Roosevelt in Washington State, U.S.A.
where mineral processing activities have resulted in high burdens of zinc and cadmium in
the lake sediments. The tree growing along the contaminated waterway display elevated
concentrations of zinc in its growth rings relative to a tree growing along an
uncontaminated tributary of Lake Roosevelt. Cadmium concentrations in the growth rings fro
both sites are similar from 1988 to 1993. Water quality data indicate an increased
concentration of cadmium in the lake from 1984 to 1988. The increased concentrations of
cadmium in the lake water were reflected in apparent increases in concentrations of
cadmium in individual rings of the tree sampled at the contaminated site. This suggests
that translocation of cadmium in the sapwood of heartwood-forming species does not occur
in the short term, and thus may not be a limiting factor in using trees as environmental
monitors for cadmium. In addition, five-year tree ring segments were analyzed and
subsequently reanalyzed as individual single-year ring segments. The analytical data
obtained for the pooled individual rings are essentially the same as for the five-year
segments, demonstrating the utility of NAA for dendrochemical studies.