HR: 0830h
AN: V21C-0533    [PDF]
TI: Use of PTFE membrane for in-situ gas phase extraction from natural waters
AU: * De Gregorio, S
EM: sofiadg@tiscali.it
AF: Dipartimento di Chimica e fisica della terra ed applicazioni dell'Universit… di Palermo, V. Archirafi 36, Palermo, Pa 90136 Italy
AU: Gurrieri, S
EM:
AF: Istituto Nazionale di Geofisica e Vulcanologia - Sezione di Palermo, V. Ugo La Malfa 153, Palermo, Pa 90146 Italy
AU: Valenza, M
EM: valenza@pa.ingv.it
AF: Dipartimento di Chimica e fisica della terra ed applicazioni dell'Universit… di Palermo, V. Archirafi 36, Palermo, Pa 90136 Italy
AB: The extraction of the dissolved gas phase in natural waters is a delicate operation which can frequently invalidate the analytical data. Several methodologies were developed in order to separate the dissolved gaseous phase from water. They can be divided in two main groups: the extraction laboratory technique (ELT) (Mazor, 1977; Sugisaki \& Taki, 1987; Andrews et al.,1989; Holt et al. 1995; Capasso \& Inguaggiato, 1998) and the extraction field technique (EFT) (Tonani, 1971; Chiodini, 1996). Recently, new EFT method have been developed using PDMS membrane, (Sanford et al., 1996; Jacinthe \& Groffman, 2001). We perform a method based on semi-permeable polymeric membrane PTFE (waterproof and permeable to the gases).The sampling device consists of a PTFE tube, sealed at one end, and connected to a glass vessel. The evacuated system is plunged in the natural water for one or more days. During this time the dissolved gases flows inside the system. The equilibrium is reached after 10 days, but a theoretical model was developed to recalculate the partial pressure of each gas species, from not equilibrated gas sample. The recalculation model was developed combining Mass Balance with "Diffusion-Solution Model", the best model to describe the gas permeation through the PTFE membrane. The recalculation model was experimentally validated by several laboratory tests and compared with ELT methods. The new method was applied in groundwater of Vulcano Island, and allows us to carry out chemical and isotopic data of dissolved gas phase from a same gas sample
DE: 1040 Isotopic composition/chemistry
DE: 1045 Low-temperature geochemistry
DE: 1094 Instruments and techniques
DE: 8419 Eruption monitoring (7280)
DE: 8494 Instruments and techniques
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting