EGM-5 Operation Manual V. 1.04 126 support@ppsystems.com
The initial moles CO
2
in the system =
× , where
is CO
2
concentration in mol mol
-1
.
T
hen, the final moles CO
2
in the system =
×
(
+
)
, where
is CO
2
concentration in mol mol
-1
.
(
1.8) The change in moles of CO
2
is (
×
(
+
)
(
× ) =
+
T
he term
is equivalent to the / term calculated above, and the
term is the
correction due to evapotranspiration.
(
1.9) So, with the H
2
O compensation, we have
= +
where can be either from the quadratic or linear fit.
FCO
2
Units for measurement of Soil CO
2
Efflux
(1.10) To give the CO
2
flux in mass/unit area/unit time the following conversion is made:
(g m
hr
) =
mol
mol s
×
1013
×
273
273 +
×
44.009 g
22.414 L
×
m
m
×
mol
10
mol
×
3600 s
hr
×
10
L
m
Where
/ i
s from eqn 1.9 from linear or quadratic fit and with H
2
O compensation
is the correction for barometric pressure with P measured in mbar by the EGM-5,
is the correction for air temperature with
input by the user in ºC,
.
.
is the molar volume and Ideal Gas constant at STP,
is the chamber volume and soil surface area,
And the remaining terms are units conversions.
(1.11) The same equation in alternate units is
(mol m
s
) =
mol
mol s
×
1013
×
273
273 +
×
1 mol
22.414 L
×
m
m
×
10
L
m
Or to convert (g m
-2
hr
-1
) to (µmol m
-2
s
-1
) multiply
(g m
hr
) by 6.312.
References
Parkinson K.J. (1981). An improved method for measuring soil respiration in the field. Journal of Applied
Ecology, 18, 221-228.
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