ICOS Science Conference, Session 3

1. ICOS flask sampler tests in Bern
Michael Schibig, Peter Nyfeler, Markus Leuenberger
Climate and Environmental Physics, Physics Institute
and
Oeschger Centre for Climate Change Research
University of Bern
ICOS Science Conference 2020, 15.-17. September 2020

2. Solved issues
> About 75 % of our sample flasks were leaky
— NORMAG took all faulty flasks back, received new sample flasks this summer
> Flask sampler needed hard- and software update
— Technicians from MPI Jena updated the sampler last year
> Testing the updated flask sampler
— Are all ports sampling the same?
— Fractionation?
— Any differences between constant flow and 1/t-sampling method?

3. Measurement setup without flask sampler
SS
S
Solenoid valve
Needle valve
Pressure regulator
Flow meter
1.6 bar
6 L min-1
250 mL min-1
S

4. Measurement setup with flask sampler
6 L min-1
SS
S
Solenoid valve
Needle valve
Flow meter
250 mL min-1

5. Sampling without flask sampler using
constant flow (10 x exchange)
CO2
δO2/N2
δAr/N2
Flask average
Outlier

6. Sampling with flask sampler using
constant flow (10 x exchange)
δO2/N2 average
δAr/N2 average
CO2 averageCO2
δO2/N2
δAr/N2
Average without sampler
Flask average
Outlier

7. Sampling with 1/t method for 15 minutes
δO2/N2 average
δAr/N2 average
CO2 averageCO2
δO2/N2
δAr/N2
Average without sampler
Flask average
Outlier
δO2/N2 10 x exchange control
δAr/N2 10 x exchange control
CO2 10 x exchange control

8. Sampling with 1/t method for 60 minutes
δO2/N2 average
δAr/N2 average
CO2 averageCO2
δO2/N2
δAr/N2
Average without sampler
Flask average
Outlier

9. Summary
CO2
[ppm]
O2/N2
[per meg]
Ar/N2
[per meg]
Flasks without
sampler
(10 x exchange)
422.74 ± 0.05 -563.8. ± 3.2 -907.8 ± 11.1
Flasks with
sampler
(10 x exchange)
422.69 ± 0.04 -564.3 ± 4.8 -902.3 ± 10.5
Flasks with
sampler
1/t 15 min
422.65 ± 0.02 -570.7 ± 2.4 -912.4 ± 6.9
Flasks with
sampler
1/t 60 min
422.63 ± 0.04 -571.8 ± 1.3 -904.3 ± 4.9

10. Conclusions
Conclusions
> Flask sampler seems to perform well in Bern
> The 24 sampling ports yield similar results
> No obvious fractionations of CO2, O2 or Ar with either of the sampling methods were observed
> Only one single gas was used for tests

11. Current issues to be solved
ICOS flask sampler is now at Jungfraujoch
> Original flask sampler pump was to weak
— Pump was replaced with a stronger one, the flow is now much better
> Flask sampler does not reach the needed sampler pressure
— Pressure sensors not suited for the low ambient pressure at Jungfraujoch?
— Back pressure valves too weak?
> Water trap of drying unit freezes over after some time, probably due to diffusion
— Add some solenoid valves to the sample line, to disconnect it from the ambient air when not sampling

12. Questions?