Dear Istvan and others,
Though we do not extract CO2 from ice (we analyse only firn air, which
is sucked from a porous firn),
I can give some brief information and references. This information is
not complete, just to start with.
In ice core samples air is trapped in form of small bubbles. These
bubbles are formed by continuous
reformation/re-crystallisation/densification of porous firn, at the
depth of 50 to 100 m ( firn/ice transition),
as firn moves down with the rate of snow accumulation. Thus, the newly
formed ice is rather porous (the density
is about 0.85) so that ~100 cc air is located within 1 kg of ice.
The amount of CO2: with ambient CO2 of 370 ppmv, 1 kg of ice gives about
0.037 cc STP of CO2, really not much.
To extract this CO2, ice is crushed under vacuum (needle crushers or
“cheese grater”), followed by
cryogenic trapping of released CO2. In practice that means taking ice
sample, keeping that in a cold
room before extraction, making some pre-cleaning (with a knife, to
remove upper few mm of ice contaminated
by transport etc.), then placing in vacuum chamber, crushing it and
collecting CO2. Melting techniques are
avoided – simply because accumulated snow often has carbonate dust and
some acids from precipitation
which would react upon melting, giving CO2.
Concerning ice from a cave - that would have different mechanism of CO2
trapping and possibly different
CO2 content. I would not surprise that people use different methods to
extract CO2 from similar samples,
e.g. from ice in permafrost.
Hope that will help you to start with,
Best regards, Sergey
A few refs are given below:
Etheridge, D. M., Steele, L. P., Langenfelds, R. L., Francey, R. J.,
Barnola, J. M. and Morgan, V. I., Natural and anthropogenic changes in
atmospheric CO2 over the last 1000 years from air in Antarctic ice and
firn. J. Geophys. Res. - Atmos., 101, 4115-4128, 1996.
Gulluk, T., Slemr, F. and Stauffer, B., Simultaneous measurements of
CO2, CH4, and N2O in air extracted by sublimation from Antarctica ice
cores: Confirmation of the data obtained using other extraction
techniques. J. Geophys. Res. - Atmos., 103, 15971-15978, 1998.
Neftel, A., Oeschger, H., Schwander, J. and Stauffer, B., Carbon-Dioxide
Concentration in Bubbles of Natural Cold Ice. Journal of Physical
Chemistry, 87, 4116-4120, 1983.
Sowers, T. et al., An interlaboratory comparison of techniques for
extracting and analyzing trapped gases in ice cores. Journal of
Geophysical Research-Oceans, 102, 26527-26538, 1997.
Sowers, T. and Jubenville, J., A modified extraction technique for
liberating occluded gases from ice cores. Journal of Geophysical
Research-Atmospheres, 105, 29155-29164, 2000.
One more ref ( I have not seen the paper)
Calmels, F. and Allard, M., Ice segregation and gas distribution in
permafrost using tomodensitometric analysis. Permafrost and Periglacial
Processes, 15, 367-378, 2004.
Forizs Istvan wrote:
> Dear Sergey,
>
> recently we have studied the stable isotope composition of block ice
> (10-20 meter thick) in ice cave and we got interesting results, but
> the interpretation of the data is not so easy. Therefore we are
> thinking about to measure the isotopic composition of CO2 trapped in
> the ice if there is a cheap method for sampling. From your letter I
> see that you have experience with stable isotope analyses of CO2
> trapped in ice.
> Would you be so kind to refer me to papers describing methods for
> sampling this CO2 gas for stable isotope analysis? We would like to
> take samples from cave ice, and the cave is not reachable by car, only
> by foot!!
>
> Best regards
> Istvan Forizs
>
> Sergey Assonov wrote:
>
>> Dear Carsten,
>>
>> just a question - could it be a higher rank or could you have other
>> job openings in near future?
>>
>> Few words about me – Russian, PhD in isotopic geochemistry, presently
>> works in the group of Carl Brenninkmeijer, at the Air Chemistry
>> Department, the Max-Planck-Institute for Chemistry, Mainz, Germany.
>> Here I have taken part in several projects, some of them are as
>> following: high-accuracy CO2 isotopic analyses of tropospheric air
>> samples (the aircraft project CARIBIC), development of new method for
>> 17O analysis in stratospheric CO2, analyses of CO2 and CO in
>> Antarctic firn aimed to reconstruct CO trend in SH (the EU project
>> CRYOSTAT), investigation of non-methane hydrocarbons extracted from
>> air samples with the aim of their future isotope analyses. Besides, I
>> have taken part in two other international ecological projects,
>> namely studies of methane emissions from Russian wetlands and methane
>> leakages from gas-transporting pipelines in Russia. A lot of other
>> analytical/instrumental experience.
>>
>> Presently I am looking for a job with modern analytical instruments,
>> aimed monitoring and environment studies, developing new analytical
>> methods as well as performing automation of analytical instruments.
>> Your Black See project looks exciting.
>>
>> Best regards,
>>
>> Sergey Assonov
>
>
>
--
Dr. S. S. Assonov,
Max-Planck -Institute of Chemistry,
J.J.Becher Weg 27,
55128 Mainz, Germany
Phone: +49 (0)6131-305-495
Fax: +49 (0)6131-305-436
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