Metodi di camionamento ed analisi di gas vulcanici e geotermici

Presentazione sul tema: "Metodi di camionamento ed analisi di gas vulcanici e geotermici"— Transcript della presentazione:

1 Metodi di camionamento ed analisi di gas vulcanici e geotermici

2 Tecniche di campionamento gas di ambiente vulcanico
Prima (e unica) legge universale: L’intepretazione dei dati anaitici dipende in prima istanza dalla loro qualità, che dipende dal metodo di raccolta ed analisi, che dipende dal tipo di emissione, dal tipo di analisi che si intende svolgere e dalla composizione stessa del gas

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4 …a brief preliminary remark
Why , where and when fluid geochemistry ? Is a sampling-analytical protocol already existing ? What does it remain to improve ? Everything?

5 Are we ready to start the sampling experience? …some considerations
To be a direct or a remote sampler ? ..or not to be

6 Two opposite (?) views direct approach. Remote sensing

7 Advantages …. sampling Disadvantages
Indirect measurements are easy to be done, allow to abtain a high number of data, imply low hazard Direct measurements have a long tradition, permit a complete analysis. Disadvantages Indirect measurements depend on parameters that cannot be exactly evaluated, complicate models calculations and assumptions. Direct measurements imply a high hazard and tedious operations at the lab.

8 fumaroles AND plume volcan Lascar flanco sur-oeste

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11 outline To sample, to analyze volcanic (and geothermal) gases
A possible way for data interpretation magmatic vs. hydrothermal gases from Andean systems Key studies to look for problems and solutions

12 sampling The collection of a naturally discharged gas phase depends on the type of emission : Atmospheric contamination Gas-gas chemical reactions Reactions with the sampling devices Type of analysis Safety conditions

13 sampling Looking for a good place to take a gas sample
in a steaming area…. The place was found …or not ?

14 Which is the “best” fumarole ? some parameter to decide
sampling Which is the “best” fumarole ? some parameter to decide Flux Temperature Type of emission Sampling point access Hazard

15 Thermal spring with bubbling gas
sampling A dirty guy A giant Deep temptation Etna volcano (Sicily, Italy) Black Smokers (middle ocean ridges) mud volcano (Azerbaijan) Muddy and burning Black monster Thermal spring with bubbling gas (Yellowstone Park, U.S.) Lava lake (Erta Ale, Ethiopia)

16 Fumaroles, the best way to discharge collectable gas
sampling Fumaroles, the best way to discharge collectable gas …a fumarolic field is even better

17 Discussing about the “correct “sampling way
Discussing about the “correct “sampling way. More questions than answers…but at the end all of us are Giggenbach’s followers

18 Muestreo de una fumarola a baja temperatura (78 °C)-Volcan Masaya - Nicaragua

19 Muestreo de una fumarola a alta temperatura (829 °C) -Volcan Satsuma Iwojima - Japan

20 Gas diffusi dal suolo– campionamento con camera di accumulo

21 Manifestacioni gassose
Un classico domo vulcanico ( °C). Anche con fumarole ad alto flusso è molto difficile evitare contaminazione di gas atmosferici in quanto è il domo stesso permeabile a tali gas.

22 Volcano Momotombo Località: 12.4N; 86.5W Altitud max: 1258 m
Ultima eruzione: 1905 15 eruzioni dal 1524; nel fu distrutta la ciuttà di Leon. Tipo de vigilanza: geofisica (INETER); visuale (Web cam).

23 Manifestacioni gassose
Il vulcano presenta un esteso campo fumarolico all’interno del cratere sommitale. Presenti numerosi punti di emissione a bassa (100°C), media ( °C) e alta temperatura (hasta 740°C). La scelta è caduta su due fumarole (614 y 741°C), Aprile

24 Vulcano Poas Località: 10.2N; 84.2W Altitud max: 2704 m
Ultima eruzione: 1992 (freatica) 39 eruzioni dal 1828 Tipo de vigilanza: geofisica (OVSICORI); geochimica (OVSICORI-Univ. Florencia - CNR Pisa); visuale

25 Once upon a time…the Dragër tubes

26 SAMPLING THE METHOD HAS TO ANSWER TO SPECIFIC REQUIREMENTS
Avoid atmospheric contamination Avoid reactions between gaseous species after the sampling Avoid reactions with sampling materials Simplicity, hardiness, lightness and cheapness of materials Safeguard the operator health DEPENDS ON THE TYPE OF EMISSION FUMAROLES BOILING/BUBBLING POOLS SOIL

27 Separation of soluble (liquid) and insoluble (headspace) compounds
sampling Separation of soluble (liquid) and insoluble (headspace) compounds

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29 Why not a simple glass vial ?
chemical solutions are a problem at the duty and the sampling time seems neverending… BUT Insoluble gases are to be “concentrated” Gas-gas reactions must be prevented Use of wet chemistry

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31 NaOH dissolve the acidic gases + H2O + Cd(OH)2 to catch H2S as CdS
A modified Giggenbach flask Non condesable gases NaOH dissolve the acidic gases + H2O + Cd(OH)2 to catch H2S as CdS Solid residue (sulfur) Gas and ionic chromatography (mass spectrometry)

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33 Gas Acidi

34 Water isotopic data can strongly improve our knowledge, thus…
sampling Water isotopic data can strongly improve our knowledge, thus…

35 “the glass sampling lines”

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37 sampling inlet Cooling water circulation Dry gas condensate

38 BOILING/BUBBLING POOLS
SOIL GASES

39 …or underwater vents

40 vacuum vial filled with NaOH solution and Cd(OH)2
plastic funnel

41 Chemicals analyzed in a basic lab (titrator, IC, GC)
analysis Chemicals analyzed in a basic lab (titrator, IC, GC) CO2, acidimetric titration HF, HCl, SO2, H2S HBr ionic chromatography H2O by weight difference H2, O2+Ar, N2, CH4, CO (TCD, He carrier) H2, He, Ne (TCD, Ar carrier) O2, Ar (TCD, He carrier, 0°C) CH4, C2-C15 (FID, He carrier) CO (FID, H2 carrier)

42 Useful parameters analyzed by…less basic lab (GC-MS, polyMS, ICP-MS)
VOCs 3He/4He 40Ar/36Ar 13dC-CO2 13dC-CH4 dD-CH4 dD-H2O d18O-H2O 34S/32S-SO2 34S/32S-H2S Metals …

43 analysis The final aim Different sources produce different compositions …and various sampling and analytical problems

44 Gas-cromatografo

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46 volcano monitoring Why do we need these data ? Geothermal prospection
Low cost information of geothermal potential evolution of the geothermal reservoir changes of the volcanic status (precursory) hot fluid characterization (geothermal application ?)

47 interpretation

48 interpretation Evaluation of deep (magmatic) and shallow (hydrothermal) fluid contribution is the aim of volcano geochemical monitoring Geothermal and volcanological investigations involve the same geochemical tools