| A tunable diode laser trace gas analyzer (TGA 100, Campbell Scientific, Logan, Utah) was evaluated in laboratory and field settings for its ability to measure ammonia (NH3) fluxes using eddy-covariance (EC) and flux-gradient (FG) methods.; Laboratory tests revealed significant TGA spectral losses at high frequencies, due to dispersion and adsorption of concentration fluctuations in the system. High amplitude, low-frequency noise was produced by the TGA due to effects of optical fringing and laser state fluctuations.; Field evaluation above a fertilized turf grass surface at Elora Research Station resulted in significant underestimation of EC-measured ammonia flux compared to FG, due to large spectral losses at high frequencies, where most NH3 transfer occurred. EC operation above a semi-natural forest at Canadian Forces Base Borden produced no significant ammonia flux measurement, as presence of low-frequency TGA-generated noise resulted in reduction of minimum system resolution beyond the magnitude of environmental exchange. |
