1. ForestC-WP4: N2O emissions
from a recently afforested
grassland in Dripsey, Co. Cork
Vesna Jaksic
Cork, February 2010

2. Contents
Introduction: N2O emissions observation (WP4)
Site Location and Sampling setup
Instruments
Chambers
Sampling protocol
Data collection
Gas analysis
Flux calculation
Results

3. Introduction: N2O emissions
observation (WP4)
N2O flux is measured with eddy covariance system since
June 2002 at an intensively managed and fertilized
grassland in Dripsey, Co. Cork
In January 2005 portion of grassland was afforested with
an 80/20 mixture of ash and alder
N2O fluxes in afforested area are measured using
chamber techniques for Gas analysis
By comparing these values to pre-afforestation fluxes of
N2O (Leahy et al., 2004) the short-term effect of
afforestation on N2O fluxes will be assessed

4. Forest site
0.4 0 0.4 0.8 1.2 Kilometers
Site Location and Sampling setup
Forest site
0.4 0 0.4 0.8 1.2 Kilometers
Latitude: 52.14ºN
Longitude 8.66ºW).

5. Site - Sampling setup
Dry side of site Wet side of site
EC Tower

6. Instruments
Rain gauge
Model ARG100 Campbell Scientific
Soil temperature probes
Model 107 Campbell Scientific
Soil moisture (water content)
reflectometer
Model CS616 Campbell Scientific

7. Chambers
The gas sampling chambers used are manufactured from PVC Pipe
They have a diameter of 300mm and a height of 250mm
The vent pipe was introduced to relieve any pressure increase that may occur
inside the chamber
Thermocouple was introduced to measure the chamber’s internal temperature
3- Way Luer Valve
Vent Pipe
Vent Pipe
Thermocouple
Fan

8. Sampling protocol
c
d
a
Ring
b
Measurement of
chamber temperature
Chamber fan
Dataloger records
soil temperature
and moisture

9. Data collection
Initial N2O sampling at the moment chamber is
placed in ring slot
N2O sampling every 10 min for duration of 30min
(4 samples per chamber)
N2O sampling frequency apx. once per week
Frequency of meteorological data collection (soil
moisture, soil temperature and precipitation) is
30min and it is recorded by datalogers

10. Gas analysis
Gas samples are chemically analysed by 3800 Gas Chromatograph, Auto
sampler, ECD and GC Packed Column (PorpakQS 80-100 MESH)

11. Flux Calculation
de
a
Chromatogram (a)
c
GCGUI2 used to integrate N2O
peaks (c)
Matlab window (d)
Excel file for flux calculations (e)
b
Text file by ‘Varian to text
conversion tool ’(b)

12. Flux Calculation
Cm = the mass/volume concentration
Cv = the volume/volume concentration (e.g. ppm or ppb)
M = the molar weight of trace gas (e.g. 28 µg N2O-N / µmol N2O)
P = barometric pressure (e.g. 1 atm)
R = the universal gas constant (0.0820575 L atm. 0[K]. Mole)
T = air temperature within enclosure at the time of sampling in [K]
TR
PMC
C v
m
×
××
=
A
CV
f rate×
=
f = gas flux as mass e.g. µg N2O-N.m-2. h-1
V = the internal volume of the enclosure [m3]
A = the soil area enclosure covers [m2]
Crate = change in concentration of gas over the enclosure period
0.0 10.020.030.040.050.060.070.0
0.0000
200.0000
400.0000
600.0000
f(x) = 3.06x + 365.7
R² = 0.86
C rate
Time (min)
Cm
Equations are adopted from
Holland et al 1999.

13. Results – to be updated for forest!
Time series analysis of
the N2O flux
Soil Moisture variation
and shows the minimum
and maximum range
Rainfall pettern
Soil temperature variation
Oct Jan Apr Jul Oct
-5
0
5
10
Flux,µgN
2
O-Nm-2
h-1
Solohead 1 (SH1)
Oct Jan Apr Jul Oct
0
5
10
15
20
SoilTemperature,°C
Oct Jan Apr Jul Oct
0
0.5
1
SoilMoisture,cm3
cm-3
2007-2008
Oct Jan Apr Jul Oct
0
20
40
Rainfall,mmday-1

14. THANK YOU