Comparison of static chambers to measure N 2 O and CH 4 fluxes from soils: results Mari Pihlatie, Jesper Riis Christiansen, Hermanni Aaltonen, Janne Korhonen, Jukka Pumpanen, Terhi Rasilo, Ana Paula Rosa, Giuseppe Benanti, Jatta Hirvensalo, Michael Giebels, Mohamed Helmy, Peter Schreiber, Radoslaw Juszczak, Roland Klefoth, Sara Vicca, Serça Dominique, Stephanie Jones, Raquel Lobo do Vale, Benjamin Wolf
Content What does the data look like? How do we calculate the fluxes from the reference chamber (Pumpeli)? Performance of the calibration system Chamber fluxes versus reference fluxes Future work
The calibration system (Pumpeli) Quartz sand Gas samples Gas samples N 2 O CH 4 FANS 17 mm 1 mm 113mm
What does the data look like? N2O concentration (ppmv) N2O concentration (ppmv).46.46.46.46.46.46.46.46.45.56.56.56.56.55.55.55.55.55 Calibration tank (Pumpeli) concentrations FL1 1 2 3 4 5 6 7 8 FL2 N2O concentration (ppmv) time (min) 2.6 2.6 2.5 2.5 2.5 2.5 2.5 1 2 3 4 5 6 7 8 time (min) N2O concentration (ppmv).9.89.88.87.86 FL5.85 2.4 2.4 2.4 2.4 1.51 2 4 6 8 time (min) N2O concentration (ppmv).84 1 2 3 4 5 6 7 8 time (min) 1.52 1.5 FL3 FL4 1.49 1.48 1.47 1.46 1.45 1.44 1 2 3 4 5 6 7 8 time (min)
Some problems during the campaign Autosampler problem: gas vials not pressurized (week 35) GC problem: Much of the N 2 O data useless Non-linearity of the ECD (can be possibly corrected?) Unstability of the GC 2.12 2.12 2.11 2.11 2.1 2.1 1.7 1.65 1.6 1.55 1.5 2.9 2 4 6 8 1 12 14 16 18 1.45 2 4 6 8 1 12 14 16 18
How the reference fluxes are calculated? Flux from the tank (Pumpeli) according to Pumpanen et al. (24): F V( C ( t ) ( C ( t )) V (( C ( t ) C ( t ))/2 ( C ( t ) C ( t ))/2) f 1 f 2 s f 1 amb 1 f 2 amb 2 ( t t ) A 2 1 Where C f (t i ) = fitted gas concentration inside the tank at time t i C amb (t i ) = ambient gas concentration at time t i V = volume of the tank (1 m 3 ) V s = volume of air-filled porosity in the sand A = surface area of the sand layer Time steps 5 min Gas samples N 2 O CH 4 Quartz sand FANS 113mm Gas samples 17 mm 1 mm
N2O concentration (ppmv) 2.58 2.56 2.54 2.52 2.5 2.48 2.46 2.44 2.42 2.4 FL5 y = 2.5575e -.9x R 2 =.9977 28 g N 2 O m -2 h -1 21 g N 2 O m -2 h -1 2.38 2 4 6 8 CH4 concentration (ppmv) 28. 27.5 27. 26.5 26. 25.5 25. 24.5 time (min) y = 27.412e -.15x R 2 =.9996 2113 g CH 4 m -2 h -1 1998 g CH 4 m -2 h -1 24. 2 4 6 8 time (min)
Performance of the calibration system 25 Reference flux ( g CH4 m -2 h -1 ) 25 2 15 1 5 Coarse dry 5 1 15 2 25 3 35 CH 4 concentration in pumpeli Reference flux ( g CH4 m -2 h -1 ) 34 36 37 38 39 Reference flux ( g CH4 m -2 h -1 ) 2 15 1 5 25 2 15 1 5 Fine dry 5 1 15 2 25 3 35 Fine wet CH 4 concentration in pumpeli 34 36 37 38 39 36 37 38 39 5 1 15 2 25 3 35 CH 4 concentration in pumpeli
Comparable to the CO 2 campaign
Not so good with N 2 O 4 Reference flux ( g N2O m -2 h -1 ) 4 3 2 1 Coarse dry.5 1 1.5 2 2.5 3 CH 4 concentration in pumpeli Reference flux ( g N2O m -2 h -1 ) 34 35 36 37 38 39 Reference flux ( g N2O m -2 h -1 ) 3 2 1 4 3 2 1 Fine dry 1 2 3 4 CH 4 concentration in pumpeli Fine wet.5 1 1.5 2 2.5 3 CH 4 concentration in pumpeli
How the chamber fluxes are calculated? Linear regression Exponential fit (not yet) Other calculation methods (not yet)
Data examples Flux level 5 Coarse sand linear regression 2.56 N2O conc (ppmv) 2.54 2.52 2.5 2.48 2.46 2.44 2.42 y = 2.5422e -.9x R 2 =.9935.7.6.5 Chamber N 2 O concentration y =.4538x +.3935 R 2 =.996 2.4 2.38 2.36 233 µg N m -2 h -1.4.3 2 4 6 8 Time (min).2 Pumpeli N 2 O concentration N2O conc (ppmv).1 18 µg N m -2 h -1...1.2.3.4.5 time after enclosure (h)
Flux level 4 Coarse sand 17 16.8 16.6 y = 16.924e -.12x R 2 =.9992 CH4 conc (ppmv) 16.4 16.2 16 15.8 15.6 15.4 15.2 819 µg C m -2 h -1 2 4 6 8 time (min) CH4 conc (ppmv) 5.5 5 4.5 4 3.5 3 2.5 y = 4.5744x + 2.9394 R 2 =.992 Series1 Expon. (Series1) 238 µg C m -2 h -1 2..1.2.3.4.5.6 time after enclosure (h)
Exponential behaviour 8 7 CH4 conc (ppmv) 6 5 4 3 2 1 5.5 5 y = 4.5744x + 2.9394 R 2 =.992 4.5 29 3 31 32 33 Running time (seconds) CH4conc (ppmv) 4 3.5 Series1 Linear (Series1) 3 2.5 2..1.2.3.4.5.6 time after enclosure (h)
Chamber fluxes vs. reference fluxes Chamber flux ( g CH4 m -2 h -1 ) 25 2 15 1 5 34: Peter coarse dry fine dry fine wet 5 1 15 2 25 Reference flux ( g CH 4 m -2 h -1 ) Chamber flux ( g CH4 m -2 h -1 ) 25 2 15 1 5 36: Jatta coarse dry fine dry fine wet 5 1 15 2 25 Reference flux ( g CH 4 m -2 h -1 )
Chamber flux ( g CH4 m -2 h -1 ) Chamber flux ( g CH4 m -2 h -1 ) 25 2 15 1 5 25 2 15 1 5 37: Stephanie coarse dry fine dry fine wet 5 1 15 2 25 Reference flux ( g CH 4 m -2 h -1 ) 37: Mohamed coarse dry fine dry fine wet 1 2 3 4 5 Reference flux ( g CH 4 m -2 h -1 )
Chamber flux ( g CH4 m -2 h -1 ) Chamber flux ( g CH4 m -2 h -1 ) 25 2 15 1 5 25 2 15 1 5 38: Radek coarse dry fine dry fine wet 5 1 15 2 25 Reference flux ( g CH 4 m -2 h -1 ) 38: Michael coarse dry fine dry fine wet 1 2 3 Reference flux ( g CH 4 m -2 h -1 )
Chamber flux ( g CH4 m -2 h -1 ) 25 2 15 1 5 Giuseppe coarse dry fine dry fine wet 5 1 15 2 25 Reference flux ( g CH 4 m -2 h -1 ) Chamber flux ( g CH4 m -2 h -1 ) 25 2 15 1 5 Roland coarse dry fine dry fine wet 5 1 15 2 25 Chamber flux ( g CH4 m -2 h -1 ) 25 2 15 1 5 Sara coarse dry fine dry fine wet 5 1 15 2 25 Reference flux ( g CH 4 m -2 h -1 ) Reference flux ( g CH 4 m -2 h -1 )
Future work Process the missing data Use different flux calculation methods for chambers Compare chamber fluxes to the MEGA chamber Estimate a leak rate using Chamber A / Pumpeli surface A Collar insertion depth Other? Roland Klefoth D=19cm Week 39 Calibration tank D = 1 cm Guiseppe Benanti 5 x 5 cm Week 39 Sara Vicca D=1 cm Week 39
Calibration Peter Schreiber tank D = 61 x cm Week 34 Roland Klefoth D=19cm Week 39 Calibration tank D = 1 cm Guiseppe Benanti 5 x 5 cm Week 39 Sara Vicca D=1 cm Week 39
Flux calculation Linear regression Exponential fit F dc dt H dc() t Ag g ( Cs C) ( Cs C) dt V H Where A = chamber basal area (m 2 ) g = transport coefficient (m s -1 ) V = chamber volume (m 3 ) C s = gas concentration in the soil C = gas concentration at time (ambient) H = chamber height (m) B' B' C( t) ( C ) e A' A' A' At ' Ag AgCs B' V V