title: LA-ICP-MS-derived U-concentrations and microstructural domains within biogenic aragonite of Arctica islandica shell.
abstract: Understanding of the uranium uptake processes (both in vivo and post-mortem) into the skeletal structures of marine calcifiers is a subject of multi-disciplinary interest. U-concentration changes within the molluscan shell may serve as a paleoceanographic proxy of the pH history. A proxy of this type is needed to track the effects of fossil fuel emissions to ocean acidification. Moreover, attaining reliable U-series dates using shell materials would be a geochronological breakthrough. Picturing the high-resolution changes of U-concentrations in shell profiles is now possible by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Here, we analyzed in situ U-concentration variations in sub-fossilized shells of ocean quahog (Arctica islandica), a commonly studied bivalve species in Quaternary geoscience, using LA-ICP-MS. Microstructural details of the shell profiles were achieved by the scanning electron microscopy (SEM). Comparison of the shell aragonite microstructure with the changes in U-concentration revealed that uranium of possibly secondary origin is concentrated into the porous granular layers of the shell. Our results reinforce the hypothesis that U-concentration variations can be linked with microstructural differences within the shell. A combination of LA-ICP-MS and SEM analyses is recommended as an interesting approach for understanding the U-concentration variations in similar materials.
authors: Arctic Centre, University of Lapland, P.O. Box 122, 96101, Rovaniemi, Finland, samuli.helama@luke.fi.
authors: Samuli
authors: S
authors: Helama
authors: Pasi
authors: P
authors: Heikkilä
authors: Katja
authors: K
authors: Rinne
authors: Jan Kresten
authors: JK
authors: Nielsen
authors: Jesper Kresten
authors: JK
authors: Nielsen
mesh_terms: D000818:Animals; D049872:Bivalvia / Q000737:chemistry; D002119:Calcium Carbonate / Q000737:chemistry*; D004784:Environmental Monitoring; D013057:Spectrum Analysis; D014501:Uranium / Q000032:analysis*; D014875:Water Pollutants, Radioactive / Q000032:analysis*
chemical_list: D014875:Water Pollutants, Radioactive; D014501:Uranium; D002119:Calcium Carbonate