The "Lung": a software-controlled air accumulator for quasi-continuous multi-point measurement of agricultural greenhouse gases.

Citation

Martin, R.J., Bromley, A.M., Harvey, M.J., Moss, R.C., Pattey, E., and Dow, D. (2011). "The "Lung": a software-controlled air accumulator for quasi-continuous multi-point measurement of agricultural greenhouse gases.", Atmospheric Measurement Techniques Discussion, 4(2), pp. 1935-1962. doi : 10.5194/amtd-4-1935-2011

Abstract

We describe the design and testing of a flexible bag ("Lung") accumulator attached to a gas chromatographic (GC) analyzer capable of measuring greenhouse gas emissive fluxes in a wide range of environmental/agricultural settings. In the design presented here, the Lung can collect up to three gas samples concurrently, each accumulated into a Tedlar® bag over a period of 20 min or longer. Toggling collection between 2 sets of 3 bags enables quasi-continuous collection with sequential analysis and discarding of sample residues. The Lung thus provides a flexible "front end" collection system for interfacing to a GC or alternative analyzer and has been used in 2 main types of application. Firstly, it has been applied to micrometeorological assessment of paddock-scale N₂O fluxes. Secondly, it has been used for the automation of concurrent emission assessment from three flux chambers, multiplexed to a single GC.
The Lung allows the same GC equipment used in laboratory discrete sample analysis to be deployed for continuous field measurement. Continuity of measurement enables spatially-averaged N₂O fluxes in particular to be determined with greater accuracy, given the highly heterogeneous and episodic nature of N₂O emissions. We present a detailed evaluation of the micrometeorological flux estimation alongside an independent tuneable diode laser system, reporting excellent agreement between flux estimates based on downwind vertical concentration differences. Whilst the current design is based around triplet bag sets, the basic design could be scaled up to a larger number of inlets or bags and less frequent analysis (longer accumulation times) where a greater number of sampling points are required.

Publication date

2011-12-31