M. Boiseau et A. Juilletleclerc, H2O2 TREATMENT OF RECENT CORAL ARAGONITE - OXYGEN AND CARBON ISOTOPICIMPLICATIONS, Chemical geology, 143(3-4), 1997, pp. 171-180
Coral skeletons contain relatively little organic material and inorgan
ically precipitated carbonate cement, although these quantities are en
ough to bias geochemical measurements. Preliminary treatment is theref
ore often necessary to remove these materials. Hydrogen peroxide seems
to be the most efficient reagent. This strong oxidant destroys organi
c matter and its acid pH promotes dissolution of carbonate cements tha
t precipitate after the coral skeleton has formed. We tested the isoto
pic effects (both on O-18/O-16 and C-13/C-12 ratios) of such a chemica
l treatment on coral aragonite. We demonstrate that only one treatment
is necessary to eliminate different contents without alteration of co
ral aragonite and we verified that there is no isotopic exchange betwe
en the oxygen atoms from CaCO3 and H2O2. We measured carbon and oxygen
isotopic compositions from samples that cover 2.5 years of coral grow
th and that were split in two ways: untreated and H2O2-treated. The H2
O2-treated subsamples reveal a clear seasonal oscillation that is not
evident in the untreated isotopic record. Therefore, hydrogen peroxide
treatment should be systematically carried out before isotopic analys
es in order to perform palaeoclimatic reconstructions. (C) 1997 Elsevi
er Science B.V.