Inverse-dispersion techniques allow inference of a gas emission rate Q from measured air concentration. In "ideal surface layer problems," where Monin-Obukhov similarity theory (MOST) describes the winds transporting the gas, the application of the technique can be straightforward. This study examines the accuracy of an ideal MOST-based inference, but in a nonideal setting. From a 6 m ϫ 6 m synthetic area source surrounded by a 20 m ϫ 20 m square border of a windbreak fence (1.25 m tall), Q is estimated. Open-path lasers gave line-averaged concentration C L at positions downwind of the source, and an idealized backward Lagrangian stochastic (bLS) dispersion model was used to infer Q bLS. Despite the disturbance of the mean wind and turbulence caused by the fence, the Q bLS estimates were accurate when ambient winds (measured upwind of the plot) were assumed in the bLS model. In the worst cases, with C L measured adjacent to a plot fence, Q bLS overestimated Q by an average of 50%. However, if these near-fence locations are eliminated, Q bLS averaged within 2% of the true Q over 61 fifteen-minute observations (with a standard deviation Q/Q ϭ 0.20). Poorer accuracy occurred when in-plot wind measurements were used in the bLS model. The results show that when an inverse-dispersion technique is applied to disturbed flows without accounting for the disturbance, the outcome may still be of acceptable accuracy if judgment is applied in the placement of the concentration detector.

Seventy‐five percent of swine (Sus scrofa) production systems in North America use anaerobic or liquid‐slurry systems for waste holding or disposal. Accurate emissions data and emission factors are needed for engineering, planning, and regulatory agencies. These data are used for system design and evaluation of the effect of animal concentrations on the regional soil, surface and ground waters, and atmospheric environments. Noninvasive techniques were used to evaluate trace gases without disturbing the meteorology or lagoon system being measured. Micrometeorological and gas sensors were mounted on a submersible barge in the center of the lagoon for use with flux‐gradient methodology to determine trace gas fluxes, without disturbing atmospheric transport processes, over extended periods. Collateral measurements included lagoon nutrient, dissolved gas concentrations, and sludge gas mass flux. Ammonia emissions varied diurnally and seasonally and were highly correlated with windspeed and water temperature. Nutrient loading measurements showed that mobile ions, which were nonvolatile, were constant throughout four successive lagoons. Immobile ions concentrated primarily in the sludge layer of the first lagoon. Measurements of denitrification N2 losses suggest as much N2−N lost as from NH3‐N. Ammonia gas emissions are not as large a percentage of total nitrogen input to the lagoons as previously thought but unaccounted‐for nitrogen requires further research.

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