Dear all,

my insitute is considering to purchase a CRDS instrument in order to 
analyse liquid water samples from soils and aquifers for dH2 and d18O. 
To analyse pore water with this technique there seem to be three major 
aspects:

1. Disturbance from organic compounds in the pore water if extracted 
liquid water is analysed. The bias from alcohols had been already 
addressed by Brand et al., RCM 23, 1879-1884. Has anyone checked if soil 
water (including pore water from organic soils) containing variable 
amounts of DOC would be feasible with this technique?

2. Using liquid--vapor equilibration and analysing H2O vapor. This has 
been suggested by Wassenar et al, 2008, EST 2008 42, 9262-9267. However 
this methods seems to be somewhat difficult as it requires complete 
tightness of flexible enclosures for equilibrating soil or sediment 
samples. We are also wondering if analysis of the equilibration bags can 
be done fully automated. However, this technique might be superior since 
it overcomes the problems from organic contamination.

3. As far as we can see there are two companies (Los Gatos, Picarro) 
offering instruments for liquid water or water vapor. The question is 
which one would be preferable for our application?

We would greatly appreciate any information to support our decision.

Reinhard

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____________________________________________________________
PD Dr. Reinhard Well
Telefon: +49 (0)531 596 2535
Fax: +49 (0)531 596 2599 
E-Mail:[log in to unmask]

Adresse:
Johann Heinrich von Thünen-Institut
Bundesforschungsinstitut für Ländliche Räume, Wald und Fischerei
Institut für Agrarrelevante Klimaforschung 
Bundesallee 50 
38116 Braunschweig 
Deutschland 
Web: http://www.vti.bund.de/de/institute/ak/

address:
Johann Heinrich von Thünen-Institut
Federal Research Institute for Rural Areas, Forestry and Fisheries
Institute of Agricultural Climate Research 
Bundesallee 50 
38116 Braunschweig 
Germany 
Web: http://www.vti.bund.de/en/institutes/ak/