The development of a tunable diode laser trace gas analyzer and its application to the measurement of trace gas fluxes using micrometeorological techniques

In 1990, during the Northern Wetlands Ecosystem Study (NOWES), a new tunable diode laser based trace gas analyzer (TGA100, Campbell Scientific, Logan, Utah), developed at the University of Guelph, was introduced to the scientific community. During NOWES, the technology was used with the eddy correlation method to measure the air-surface exchange of CH4 over natural Boreal Wetlands. The data collected contributed significantly to the understanding of the processes controlling methane evasion to the atmosphere from those ecosystems. Since that time, the TGA100 has been extensively applied by the authors for the study of the air-surface exchange of the trace gases N2O, CH4, and NH3. Using primarily the flux-gradient micrometeorological technique, studies have been conducted to determine fluxes of: CH4 over Boreal forests; N2O and CH4 over agricultural plots; CH4 over manure storage and management systems; and NH3 over fields. In addition, the TGA has been used in laboratory-scale studies of processes controlling the production of N2O in agricultural soils.

The TGA100 is a fast response, sensitive instrument capable of achieving total system noise levels on the order of 4 ppbv rms for CH4, 1 ppbv rms for N2O, and 2 ppbv rms for NH3 in a 5 second period. It is also capable, depending on the associated fluid system design, of sampling rates as high as 10 samples per second. The TGA100 technology is presented, with emphasis on recent improvements to this system. The paper also highlights the key contributions to science by the authors through the application of the TGA100 technology since its inception a decade ago.