Dear Istvan,
hope you had a nice travel home from the ESIR Meeting in Leipzig already 
one month ago.
I followed with interest the discussion of obtaining gas inclusions from 
ice. Long long ago, I worked with a melting procedure for obtaining gas 
inclusions from ice cores from the Novolazarevskya station, Antarctica. 
I will send you an article "Extractive methode for obtaining gas 
inclusions from ice" we (Peter Kowski and me) published in our 
ZfI-Mitteilungen No 51, 1982, 41-48.
Sergey may be right if dust is a really  contamination source AND if 
acid particles or acids dissolved in ice may react with the dust 
carbonate. Otherwise, small bubles or dissolved gas in ice could 
probably be closed in ice or adsorbed on it during vacuum extraction 
after crushing. And, the melt water may also neutralize any acids 
although the mineralization of the water is very low. Therefore, I would 
prefer the melting procedure under vacuum.
Best wishes
Gerhard

Sergey Assonov schrieb:

> 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



-- 
Dr. Gerhard Strauch
UFZ-Umweltforschungszentrum Leipzig-Halle GmbH
UFZ-Centre for Environmental Research Leipzig-Halle
Department Hydrogeologie
Department Hydrogeology 
Theodor-Lieser Str. 4
D-06120 Halle
Tel  ++49 (0) 345-5585 206
Fax  ++49 (0) 345-5585 559