4. Conclusions
A sensitive fluorimetric method in FIA able to determine calcium
in firn and ice samples has been developed. It allows to
analyse concentrations around 0.2 gL−1 with a reproducibility
of 3.7% using a 275 L injection loop; the reproducibility
improves till values lower than 0.5% for concentrations around
10gL−1, using a 50 L loop. With the same loop, the reproducibility
here obtained is significantly lower than the one
reported in literature (reproducibility of 3.5% for concentrations
of 20gL−1 [15]). The calculated detection limit revealed to be
15 ng L−1, which is one order of magnitude lower than the most
sensitive CFA method for Ca determination currently available
(0.1gL−1, [14]).
In order to validate the method here developed, it was applied
to the analysis of discrete samples from an alpine ice core and
the results were compared with the analysis of the same samples
by Ion Chromatography revealing no bias between the two data
sets.
Ca high-resolution record of the top 10m of Lys ice core
allowed to detect its seasonal pattern and the occurrence of a
few Saharan dust events, to be used for ice core dating. The method performances and the comparison with another
analytical technique, already established in ice core analysis
revealed it is suitable for Ca determination at ppb levels (Alpine
and Arctic samples, Antarctic ice samples belonging to glacialcold
periods) and at ppt levels (Antarctic samples corresponding
to interglacial-warm periods).