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Prof. Dr. Nicolas Brüggemann │IBG-3 Agrosphere │Foschungszentrum Jülich GmbH

Experience with isotope-specific laser instruments

IBG-3 Agrosphäre 213. Dezember 2010

Instruments used

TGA100A (Campbell Scientific): lab and fieldTGA200 (Campbell Scientific): labL1102-i (Picarro): lab

Experiments

Natural abundance measurementsTracer experiments (13CO2, H218O)

IBG-3 Agrosphäre 313. Dezember 2010

CO2 profiles soil respiration

Isotope-specific measurements of

Deep (30 cm) and shallow (2 cm) collars

IBG-3 Agrosphäre 413. Dezember 2010

The instrumentTDL instrument: TGA100A (Campbell Scientific, USA)

IBG-3 Agrosphäre 513. Dezember 2010“Chamber-in-chamber” system

Air inlet for soil chamber

Sample intake for ambient air

Soil chamber

IBG-3 Agrosphäre 613. Dezember 2010

δ13C of soil-respired CO2 in shaded and unshaded alpine grassland after 13CO2 pulse labelling: labelled plots

Bahn et al. (2009), New Phytologist 182: 451–460

IBG-3 Agrosphäre 713. Dezember 2010

…Picarro L1102-i …Campbell TGA200

Laboratory experiments with…

IBG-3 Agrosphäre 813. Dezember 2010

Experimental setup plant measurements

Norwayspruce

Grey poplar

IBG-3 Agrosphäre 913. Dezember 2010

Experimental setup soil measurements

IBG-3 Agrosphäre 1013. Dezember 2010

CalibrationTGAOne reference gas at high

concentration− TGA 100A: �20 vol%− TGA 200: �0.5-1 vol%

Usually two calibration tanks (tertiary standard), bracketing ambient CO2(higher conc for tracer applications)

− 325 ppm− 550-670 ppm

Traceable secondary standard from INSTAAR/CMDLCalibration frequency (automated)

− TGA 100A: every 10-15 min− TGA 200: every 3 min

PicarroManual switching between sample air

inlet and vaporizerManual start of the calibration with

liquid waterTwo-point calibrationPrimary standard from IAEAFrequency: �once per week

=> Calibration is now improved and automated in the new L2120-i

IBG-3 Agrosphäre 1113. Dezember 2010

Materials used

Synflex-1300 ¼‘‘ tubingStainless steel valves and fittingsStainless steel air humidifiers Stainless steel chambers for soil respiration measurementsPerspex chambers/cuvettes for lab experiments

Measurement frequency and averaging intervals

TGA100A: 10 Hz, averaging the last 30-45 s of a 90-100 s intervalTGA200: 10 Hz, averaging the last 10 s of a 20 s intervalPicarro: ? Hz, 15 s output (=averaging?) interval

IBG-3 Agrosphäre 1213. Dezember 2010

What do we want to know?What do we have to measure where and how often?

How to measure plant CO2 and H2O isofluxes continuously? Automated chambers?

How to measure soil moisture and CO2 profiles at all/continuously?How to integrate precipitation isotope measurements into your

ongoing H2O vapor measurements?

What does the ideally equipped isoflux field site look like?