Utilisation géochimique des carbonates biogènes marins : exemples des colonies coralliennes, des coquilles de moules et des otolithes de poissons

Cet article présente, à partir d'études et de résultats concrets, les principaux intérêts des analyses isotopiques qu'il est possible de mener sur des archives carbonatées marines. Les mesures des isotopes du plomb et de l'oxygène effectuées par exemple sur des colonies récifales, des coquilles de moules et des pièces calcifiées de l'oreille interne de poissons téléostéens, permettent ainsi d'accéder à une meilleure compréhension des perturbations environnementales

Utilisation géochimique des carbonates biogènes marins : exemples des colonies coralliennes, des coquilles de moules et des otolithes de poissons

Cet article présente, à partir d'études et de résultats concrets, les principaux intérêts des analyses isotopiques qu'il est possible de mener sur des archives carbonatées marines. Les mesures des isotopes du plomb et de l'oxygène effectuées par exemple sur des colonies récifales, des coquilles de moules et des pièces calcifiées de l'oreille interne de poissons téléostéens, permettent ainsi d'accéder à une meilleure compréhension des perturbations environnementales

Pollutant lead transport and input to the Caribbean during the 20th\mathsf{^{th}} century


Here we evidence significant shifts in the sources of Pb input to the Caribbean based on lead isotope records from massive corals collected near Puerto Rico. While mean Pb/Ca ratios in these corals generally mimic alkyl Pb consumption in the US, we observe a 5 to 8 years delay in the maximum Pb peak in the 1970s. Pollutant Pb decay in corals is not as rapid as expected from the phasing out of leaded gasoline related to European and regional sources. Furthermore, $^{206}$Pb/$^{207}$Pb imprints often display significant interannual variations with no clear temporal evolution. This seems to be partly connected to specific meteorological events and seasonal atmospheric shifts with mixed input from the southern US, Europe and Latin America/Caribbean. New corats from the Western Caribbean (Martinique, Guadeloupe) are presently analysed in order to investigate these isotopic shifts in relation to atmospheric input sources and oceanic recirculation

Lead in the western South China Sea: Evidence of atmospheric deposition and upwelling

In recent decades, rapid industrial developments have increased lead (Pb) inputs to the South China Sea. To quantify the increasing variability, we investigated 170 years of skeletal Pb and Pb isotopes from an offshore, central Vietnamese coral. The Pb/Ca in the coral was 10–16 nmol/mol before the mid-1950s and increased to more than 30 nmol/mol by 2000. While the regional phaseout of leaded petrol commenced in 2000, coral Pb/Ca continued increasing until 2004, possibly due to regional upwelling and the transport of previously emitted Pb from tropical Pacific waters. The [superscript 206]Pb/[superscript 207]Pb ratio in the coral was 1.191–1.195 before mid-1950s, suggesting natural sources. Since then, the ratio decreased, reaching ~1.165 in 2004. Lead isotopes show high linearity between natural and Chinese emitted Pb, with the latter contributing ~40%~60% of the skeletal Pb after 2000.Singapore-MIT Alliance for Research and Technology. Center for Environmental Sensing and ModelingSingapore. National Research Foundatio