Abstract:
Microbial biomass gases, carbon dioxide (CO2) and methane (CH4), are generated by a
microbial respiration process. They can be used as environmental indicators for assessing degree of a
pollutant exposing to the environmental system. These gases are considered as green house gases which
directly affect the change of the earth’s climate. The respiration process plays a major role for observing
those gases and their content in environment can be measured by many analytical approaches.
This work focused on CO2 and CH4 gases analysis in soil using titration method and headspace
gas chromatography (HS-GC). Titration method was studied with the adjusted respirometer by flushing
CO2 gas with N2 gas from the reaction chamber for CO2 trapping by KOH solution. This method is
simple and inexpensive for determining CO2. Detection limit, linearity range, and %RSD in titration
method were 14.12 mg m-3 CO2, 50-180 mg m-3 CO2, and 3.98 - 9.63 %, respectively. Percentage
efficiency of trapping CO2 was in the range 61.41 ± 4.26 %. Comparative measurement using HS-GC
was applied by studying packing materials for packing the column. The optimum packed column was
silica gel (3.1 mm x 101 cm, 6.5 g) which could separate CO2 and CH4 using the optimum HS-GC
condition. The HS-GC gave high sensitivity and low detection limits which were 2.29 μg m-3 for CO2
and 0.02 μg m-3 for CH4, respectively. Soil and sediment samples applications using both techniques to
determine CO2 and CH4 were selected from a vegetable garden at Salaya campus and a canal at
Phayathai campus. The biomass gases were 7.51 g CO2 m-2 d-1 for soil samples and 8.01 g CO2 m-2 d-1
for sediment samples. CH4 gas was not found in all samples. CO2 and CH4 contents are significantly
different with the sample niches. These measurements will help us to understand the environmental
system better.