Sr isotope analysis of water samples at the Radiogenic Isotope Laboratory of the Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Napoli - Osservatorio Vesuviano (INGV-OV)

Riassunto

Since 2000, a Thermal Ionisation Mass Spectrometer (Thermo ScientificTM Triton TI® Mass Spectrometer) and a clean laboratory are operating at the Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Napoli, Osservatorio Vesuviano (OV) to measure strontium (Sr) and neodymium (Nd) isotope compositions of volcanic products for scientific purposes. In 2014 particular attention has been dedicated to set up the analytical procedure for extracting Sr and Nd and measuring their isotope compositions from groundwater and mineral water, due to its growing interest on environmental topics. Strontium is considered a trace element and Sr2+ preferentially substitutes for Ca2+ in most rock types since it geochemically behaves like calcium. Groundwater is enriched in Sr during water-rock interaction processes occurring within the saturated and/or unsaturated zones. Conversely, Sr is removed from water as a result of mineral precipitation and ion exchange reactions. The most common removal process is the coprecipitation of Sr2+ ions with calcium carbonate. However, this latter process does not fractionate Sr2+ [Faure and Powell, 1972]. Therefore, the Sr isotopic composition of groundwater records an integrated signal of water-rock interaction along flow path and dissolution/precipitation events, and can be used as a dynamic tracer to constrain subsurface...