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Defining, exploring, imaging and assessing reservoirs for potential heat exchange - Potsdam, Germany, Workshop1
Defining, exploring, imaging and assessing reservoirs for potential heat exchange - Potsdam, Germany, Workshop1
6-8 November 2006 GeoForschungsZentrum Potsdam (GFZ)
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Methods and apparatus for feeding samples of gas at controlled pressure into a gas chromatograph (international patent pending PCT/IB2005/001568) and its application to geochemical surveillance of reactive gas from Pozzuoli Solfatara (Naples, Italy): chronological evolution and local ground displacement
Caprai Antonio
This new apparatus (International patent Caprai-CNR pending no. PCT/IB2005/001568) 
for use in the analysis of gas mixtures can be fitted on one or more gas 
chromatographers working in parallel or at different times, and used to adjust the 
internal pressure of the gas to the value most convenient for introducing the 
sample into the analyzer. It can also be used for only one or two points of 
calibration of a pure gas standard (no preparation of a particular external 
standard is necessary). No detector overloading of any kind will occur. 
Main uses
It can be applied to any kind of gas analysis, but is particularly suited to 
environmental and geochemical investigations.
1.	Where a number of runs are required, there is no need to take different 
samples of gas from the flask. 
2.	We have a continual knowledge of the internal pressure of the flasks. 
3.	We achieve  similar conditions for standards and samples. 
4.	We simplify the standardization procedure. 
5.	We can increase pressure so as to introduce more absolute small quantities 
of a given component. 

The advantages of this system include: 
1.	Analytical error is minimized because pressure is completely under control. 
2.	One quantity of sample only can be analyzed several times in different gas 
3.	The pressure inside the flasks is legible. 
4.	Both sample and standard can be introduced at the same pressure. 
5.	Excellent standardization can be achieved with two calibration points. 
6.	Errors in preparation of standards can be avoided. 
7.	The pressure of low-pressure samples can be increased. 

Application at Pozzuoli Solfatara 
Caprai  A., Calvi E., Doveri M., Leone G. and Mussi M.

In 2001, a team from the Institute of Geosciences and Earth Resources working in 
the Phlegrean Fields area began a new survey consisting of the systematic sampling 
of the fluids emerging from the Pozzuoli Solfatara, and particularly from the 
fumarole known as Bocca Grande; the same team had carried out a similar survey from 
1982 to 1985, while Cioni (CNR-IGG) and his co-workers monitored the same 
parameters in the area from 1982 to1997 and Martini (Università di Firenze – DST) 
from 1994 to 2000. The results of chemical analyses of the most reactive gases, 
such as H2, CH4, and H2S, from 2001 until now, have revealed a trend that is shown 
in the triangular diagram. The main feature of this trend is the temporal evolution 
of the chemical composition of the above gases in Pozzuoli Solfatara during the 
period 2001-2005, which indicates a gradual return to the same compositions 
measured during the period 1983-1985, with a significant increase in bradyseism. 
The chemical composition of these gases reached values very similar to the current 
values in coincidence with the maximum displacement of bradyseism recorded at the 
end of 1984.
 A similar trend in gas chemical composition can also be observed for the period 
1989-1997 and 1998-2000. Comparison of triangular diagrams H2, CH4, H2S with the 
plot of altitude variations available up to 2003 reveals a correspondence between 
the evolution of relative gas concentrations and the trend of bradyseism.    On the 
basis of the data available, we can observe a typical trend characterized by a 
relative increase of H2S and decrease of CH4 during the phase of changing tendency 
in bradyseism . These observations should be verified by a careful comparison with 
renewed measurements of ground movement.
Further evidence of an apparent correspondence between temporal evolution of gas 
chemical composition and the trend in bradyseism would confirm the important role 
of geochemical monitoring of these parameters in the prediction of bradyseismic 
Id: 20
Place: GeoForschungsZentrum Potsdam (GFZ)
14473 Potsdam, Telegrafenberg
Starting date:
06-Nov-2006   15:25
Duration: 03'
Contribution type: Poster
Primary Authors: Dr. CAPRAI, Antonio (National Council of Research - Institute of Geosciences and Earth Resources)
Co-Authors: Mr. CALVI, Enrico (National Council of Research - Institute of Geosciences and Earth Resources)
Dr. DOVERI, Marco (National Council of Research - Institute of Geosciences and Earth Resources)
Prof. LEONE, Gabriello (Pisa University - Department of Man and Environmental Sciences)
Dr. MUSSI, Mario (National Council of Research - Institute of Geosciences and Earth Resources)
Presenters: Dr. CAPRAI, Antonio
Material: slides Slides
poster Poster

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