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soil respiratory work

Soil Respiration Equipment

Soil Respiration Equipment

soil respiration equipment

The 12-channel ADC Bioscientific 2250 infrared gas analyser monitors microbial respiration activity by measuring the evolved CO2 values at regular intervals to an accuracy of 0.1 mg.m-3. The system operates by sequentially analysing each channel on an automatic trigger signal from the Gas Handling Unit (GHU). Through a series of solenoids the GHU maintains the airflow in the other 11 channels using a bypass pump, whilst the 2250 gas analyser draws the air through the current channel using the sample pump. The system stays on the current channel (dwell time) until steady state conditions are reached and just prior to channel switch over, sample values are logged to file. In this way the values can be plotted for each channel over a period of time to establish its respiratory activity.

To prevent soils from drying out the input air is taken from the top of a water tank containing a depth of 200 mm of de-ionised water. Through this, a low volume pump fed air into two large porous stones (see diagram below). This ensured that the input air is saturated. The amount of CO2 is then removed from the input air by means of a chemical stripper containing sodium hydroxide granules prior to entering the samples. Each sample is analysed every at set intervals for evolved CO2. The output values from the gas analyser are then sent directly to a data logger to log the results.

soil respiration diagram

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