10 WS-TOX-H2S Hydrogen sulfide detector
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10.3
Flux measurement
H
2
S fluxes from soil are simulated by injecting a known flow of gas into the
accumulation chamber. The interface between the accumulation chamber and
the calibration table is built to minimize the gas leakage.
For flux between 0.0002 and 0.02 moles/m
2
/day the injected flux is controlled
and measured with a precision mass flow controller. This MFC is electronically
stabilized (Accuracy 3%).
For fluxes between 0.06 moles/m
2
/day and 0.6 moles/m
2
/day the injected flux
is controlled by means of a mechanical flow reducer and measured using a
bubble flowmeter (Accuracy 3%) before and after the flux measurement with
the accumulation chamber.
A thermometer and barometer were utilized to measure the barometric pressure
and the air temperature during the experiment in order to select the correct
accumulation chamber conversion factor.
The same procudure was utilized to check the instrumental response to Carbon
Dioxide.
Standard mixture of hydrogen sulfide/carbon dioxide/nitrogen cylinder and
pressure reducing valve.