Photo-acoustic spectroscopy

A photo-acoustic field gas monitor from Lumasense™ Technologies – INNOVA 1412i has been used for agricultural air monitoring studies including measurements of N2O, CO2, and NH3, in maize and grasslands.

At IRRI, photo-acoustic spectroscopy (PAS) has been used to monitor CH4 and N2O emissions from rice fields in tandem with the LI-COR portable dew point generator. Preliminary tests have shown that the water vapor compensation feature of the PAS was not sufficient to eliminate water vapor interference for CH4 measurements in rice fields especially when the ambient air temperature was high, resulting in very high PAS readings for CH4. However, this interference was eliminated when the sampled gas was cooled down, as it passed through the condenser of a dew point generator, before it goes to the PAS. This procedure resulted in low and very stable water vapor readings during the measurements.