The potential of laser ablation sampling (LAS) in
conjunction
with inductively coupled plasma−mass spectrometry
(ICP−MS) for multi-element analysis of tree rings in
Acer
pseudoplatanus L. (sycamore) growing in urban U.K. is
evaluated. Annual growth increments in xylem tissue
are
readily observed. Individual rings formed between
1975
and 1992 were sampled and analyzed by ICP−MS after LAS
or after conventional nitric acid digestion. To correct
for
differences in ablation, 13C was used as in
internal
standard. Significant linear relationships were found
for
Pb, Mg, and Mn concentrations recorded after acid
digestion and values determined by LAS. Lead in xylem
declined steadily after 1975 until the late 1980s, clearly
reflecting a reduction in lead deposition in urban U.K.
during this period. Using acid digestion, Cd was
detected
only in a tree close to a Cu−Cd refinery; concentrations
generally remained steady in this tree through the study
period.
A similar response was found in this tree with LAS.
Cadmium
was also detected in one of the two other trees 6 km from
the refinery using LAS, but at much lower concentrations.
Distribution of Mg and Mn within tree rings differed
between trees; more likely reflecting differences in soil
chemistry rather than atmospheric deposition. The
results
indicate that LAS coupled with ICP−MS can be used
directly to determine changes in xylem chemistry, which
reflect changes in exposure to metal deposition or
changes in soil chemistry. This provides a repeatable,
non-destructive sensitive method for determining many elements
in wood, with high spatial resolution.