Two methods to estimate horizontal standard deviations of dispersion in lowwind speeds conditions

International audienceIn this paper, two methods to obtain dispersion coefficient, during low wind speed and stable conditions, are presented. These methods have been developed by using wind velocities recorded with an ultrasonic anemometeron a typical subUrban site

Estimates of lateral dispersion parameters in low wind speed conditions

International audienceWind speed time series recorded during stable low wind speed conditions are typically non-stationary, with large horizontal oscillations, commonly known as meandering. In this paper, two wavelet-based methods are proposed to obtain lateral dispersion coefficients from such time series. These methods, associated with a specific wind model, have been tested by using wind velocities recorded, with an ultrasonic anemometer, on a typical suburban site located in the southern part of the Paris region (France). Both of them give similar results and differ from classical Briggs's and Doury's parameterisations for standard deviations.Les composantes horizontales de la vitesse du vent, enregistrées pendant des épisodes de vent faible et en atmosphère stable, forment généralement des séries temporelles non stationnaires qui présentent de grandes oscillations communément connues sous le nom de méandres. Dans cet article, deux méthodes basées sur la décomposition en ondelettes discrètes de ces séries sont proposées afin d'obtenir les coefficients de dispersion latérale caractéristiques d’un site donné. Ces deux méthodes, associées à un modèle de vent spécifique, ont été testées en utilisant des vitesses enregistrées, à l'aide d'un anémomètre sonique, sur un site situé dans une zone péri-urbaine caractéristique du sud de la région parisienne (France). Les deux méthodes donnent des résultats similaires et différents des coefficients de dispersion classiques de Briggs et Doury

Ammonia Emissions Measured Using Two Different GasFinder Open-Path Lasers

The challenges of accurately measuring in situ ammonia (NH3) losses from agricultural systems are well known. Using an open path laser coupled with a backward Lagrangian stochastic dispersion model is a promising approach for quantifying both point- and area-sources; however, this approach requires the open path laser to detect low NH3 concentrations and small concentration differences. In this study, we compared the new GasFinder3 open path laser (Boreal laser Inc., Edmonton, Canada) with the GasFinder2 sensor, the previous version. The study took place at two locations: an outdoor open-air manure compost site, and a field of wheat stubble which was fertilized with urea ammonium nitrate. Results showed the two lasers reported similar concentrations during three days of measurements at the compost site, but differed at the field site, where concentrations were close to the minimum detection limit. The GasFinder3 had a lower standard deviation under all conditions, especially with low wind speed and high relative humidity

Effects of Two Manure Additives on Methane Emissions from Dairy Manure

Liquid manure is a significant source of methane (CH4), a greenhouse gas. Many livestock farms use manure additives for practical and agronomic purposes, but the effect on CH4 emissions is unknown. To address this gap, two lab studies were conducted, evaluating the CH4 produced from liquid dairy manure with Penergetic-g® (12 mg/L, 42 mg/L, and 420 mg/L) or AgrimestMix® (30.3 mL/L). In the first study, cellulose produced 378 mL CH4/g volatile solids (VS) at 38 °C and there was no significant difference with Penergetic-g® at 12 mg/L or 42 mg/L. At the same temperature, dairy manure produced 254 mL CH4/g VS and was not significantly different from 42 mg/L Penergetic-g®. In the second lab study, the dairy manure control produced 187 mL CH4/g VS at 37 °C and 164 mL CH4/g VS at 20 °C, and there was no significant difference with AgrimestMix (30.3 mL/L) or Penergetic-g® (420 mg/L) at either temperature. Comparisons of manure composition before and after incubation indicated that the additives had no effect on pH or VS, and small and inconsistent effects on other constituents. Overall, neither additive affected CH4 production in the lab. The results suggest that farms using these additives are likely to have normal CH4 emissions from stored manure