Fast deuterium analysis of water samples by LIBS.

The deuterium composition of natural waters, along with other isotopic and chemical data, is a fundamental parameter in geochemical studies. For example, 1) the deuterium concentrations in the water discharged from geothermal wells is useful to discriminate its possible source; 2) temporal variation of the deuterium content in the steam condensates from high-temperature volcanic fumaroles may indicate changes in the degassing mechanism from the related deep magma, or different contributions from shallow groundwater to the fumarolic conduits linked to changes (e.g. earthquake-induced) in the fracture permeability of the rocks. The deuterium content in a water sample is commonly obtained by a two-steps method. The water sample reacts with zinc shots at 450ºC to give hydrogen, that is subsequently transferred to the mass spectrometer for analysis. Recent preliminary applications of the LIBS technique by the Applied Laser Spectroscopy Laboratory at IFAM to deuterium-rich water samples revealed that the deuterium and hydrogen spectral lines can be easily distinguished if the deuterium concentration is higher than about 5 parts per hundred. More work will be necessary in the future to decrease this lower limit in the deuterium content.