gaseous emissions from soil quantified by a photoacoustic method
DESCRIPTION
Gaseous Emissions from soil quantified by a photoacoustic methodby dr. Martina PredotovaTRANSCRIPT
Gaseous emissions from soil quantified by a photoacoustic
method
Dr. Martina Predotova
ICRAF, KenyaJuly 2011
Origin
INNOVA monitor originally product of Brüel & Kjær(www.bksv.com)
Sound and vibration analyses/measurements
LumaSense Technologies, Inc.(www.lumasenseinc.com)
Over 50 yearsTemperature and gas sensing intruments
Industry, energy and cleaning technologies
Gas monitor: Innova
Uses- Quantitative analyses of up to 5 gases + H2O, separated
or in mixtures- Health and safety measurements- Indoor air-quality and ventilation measurements- Detection of accidental releases of gases/vapours- Gaseous emissions in agriculture
Gas monitor: Innova
- Selectively measures a wide range of gases/vapours- Accurate: Self-testing procedures- Compensates for: water vapour interference
interference from other gases- Portable- Distanced sample collection- Operates immediately
no long warm-up, immediate analyses - Real time measurement data on screen,
background memory- Offline or online measuring task possible- User-friendly handling
Gas monitor: InnovaFunctional diagram
Methodology: Method comparison
1. Innova2. Li-Cor CO2 analyzer3. Gas chromatograph
(GC)
Closed chamber
(1)
(1)
(2)
(3) (3)
Methodology: Method comparisonInnovaChamber closure time: 6 minSampling interval: every 2 minAnalyzed gases: CO2, N2O and CH4
Li-CorChamber closure time: 5 minSampling interval: continousAnalyzed gases: CO2
GCChamber closure time: 30 minSampling interval: at 0, 10, 20 and 30 minAnalyzed gases: N2O and CH4
5 chambers per site
Methodology: Method comparison
Kakamega district: forests / areas converted to cropland
3 conversion categories (3 farms + 3 forests per category)- Converted in 50‘s- Converted in 80‘s- Recent conversion
Results: Method comparison
0
5
10
15
20
25
30
50's 80's Recent
Conversion category
CO
2(k
g ha
-1h-1
)
CO2 emissions from farms and forests(means and stdev., n = 15)
Farm / InnovaFarm / Li-CorForest / InnovaForest / Li-Cor
Results: Method comparisonN2O emissions from farms and forests
(means and stdev., n = 15)Farm / InnovaFarm / GCForest / InnovaForest / GC
0
2
4
6
8
10
12
14
16
50's 80's Recent
Conversion category
N2O
(g h
a-1h-1
)
Methodology: Spatial variability of GHG
Measured with Innova, 12 rings per site
Sites
1. Heavy soil, recent conversion, high Corg., maize
2. Heavy soil, old conversion, low Corg.,maize
3. Forest, high Corg.
4. Sandy degraded soil, no vegetation
5. Sandy soil, rehabilitated, acacia
(1) (3)
(4) (5)
Results: Spatial variability of GHG
Heavy soil, high Corg.
6.06.57.07.58.08.59.09.5
10.0
CO
2(k
g ha
-1h-1
) 3 rings
4 rings
5 rings
6 rings
7 rings
8 rings
9 rings
10 rings
11 ringsRehabilitated sandy soil, low Corg
1.01.52.02.53.03.54.04.55.0
Increasing number of rings
CO
2(k
g ha
-1h-1
)
Differences between sites (means, n = 3-11)
Results: Spatial variability of GHG
2
3
4
5
6
7
8
N2O
(g h
a -1
h-1)
Heavy soil, high Corg.
3 rings
4 rings
5 rings
6 rings
7 rings
8 rings
9 rings
10 rings
11 rings
N2O
(g h
a -1
h-1)
Degraded sandy soil, low Corg.
-2
-1
0
1
2
3
4
Increasing number of rings
Differences between sites (means, n = 3-11)
Results: Spatial variability of GHGC
O2
(kg
ha-1
h-1)
Increasing number of rings
Degraded sandy soil, low Corg.
01
2345
67
Heavy soil, high Corg.
2468
1012141618
CO
2(k
g ha
-1h-1
)
Number of rings to measure (means and stdev., n = 3-11)
3 rings
4 rings
5 rings
6 rings
7 rings
8 rings
9 rings
10 rings
11 rings
8 rings?
7 rings or less?
Results: Spatial variability of GHGNumber of rings to measure (means and stdev., n = 3-11)
-202468
101214
Heavy soil, high Corg.
N2O
(g h
a -1
h-1)
3 rings
4 rings
5 rings
6 rings
7 rings
8 rings
9 rings
10 rings
11 rings
8 rings?
7 rings?
Heavy soil, low Corg.
N2O
(g h
a -1
h-1)
Increasing number of rings-2
0
2
4
6
8
10
12
Methodology: Temporal variability of GHG
24 hours experiment, with Innova
Measuring in 2 h interval, 8 rings
Sites1. field maize, beans intercropping2. forest
Results: Temporal variability of GHG
N2O
(g h
-1ha
-1)
-4-202468
1012
CH
4(g
h-1
ha-1
)
-500
50100150200250300350
16:00
18:00
20:00
22:00
00:00
02:00
04:00
06:00
08:00
10:00
12:00
14:00
Time of a day (hours)
CO
2(k
g h-
1ha
-1)
456789
1016
:0018
:0020
:0022
:0000
:0002
:0004
:0006
:0008
:0010
:0012
:0014
:00
Time of a day (hours)
(Means and stdev: chamber temp. n=16, soil temp. n=1, gas flux n=8)
05
10152025303540
Tem
p. (C
°)
ChamberSoil 0.1m depth
16:00
18:00
20:00
22:00
00:00
02:00
04:00
06:00
08:00
10:00
12:00
14:00
Conclusions
The three tested methods delivered comparable results of CO2 and N2O fluxes from forests and farm land.
Manual sampling for GC with subsequent sample analyses is more labour and time intensive.
Spatial variability of gaseous emissions vary between different ecosystems.
Measurements on 8 spots covered the spatial variability of CO2 and N2O fluxes on most tested sites.
The emissions of CO2, N2O and CH4 fluctuate strongly in a course of 24 hours.
Thank you
Detection limits
NH3: 200 ppbN2O: 30 ppbCO2: 3.4 ppmCH4: 400 ppb