An oxygen sensor for continuous long-term
measurement of soil respiration
Bruce Bugbee
Utah State University
Mark Blonquist
Apogee Instruments
CH2O + O2
20.95%
Advantage of
measuring CO2
Advantage of
measuring O2
CO2 + H2O
0.04%
O2 = 20.95%
CO2 = 0.04%
= 520 x
CO2 is 30 times more soluble
in water than O2
CO2 is 30 times more soluble in water than O2
CO2
O2
Respiratory quotient: CO2 / O2
Carbohydrate
Protein
Fat
Lignin
Nitrification:
NH4 + 2O2
= 1.0
= 0.8
= 0.6
= 0.2
RQ = 0.0
NO3 + 2H+ + H2O
Factors affecting
gas concentration in soil
• Temperature
• gas / liquid partitioning
• effect on molar density and sensor electronics
Factors affecting
gas concentration in soil
• Humidity
H2O
Factors affecting
gas concentration in soil
• Atmospheric pressure