Evaluation of a new inference method for estimating ammonia volatilisation from multiple agronomic plots

Abstract

Abstract. Tropospheric ammonia (NH 3 ) is a threat to the environment and human health and is mainly emitted 9 by agriculture. Ammonia volatilisation following application of nitrogen in the field accounts for more than 40% 10 of the total ammonia emissions in France. This hence represents a major loss of nitrogen use efficiency which 11 needs to be reduced by appropriate agricultural practices. In this study we evaluate a novel method to infer 12 ammonia volatilisation from small agronomic plots made of multiple treatments with repetition. The method is 13 based on the combination of a set of ammonia diffusion sensors exposed for durations of 3 hours to 1 week, and 14 a short-range atmospheric dispersion model, used to retrieve the emissions from each plot. The method is 15 evaluated by mimicking ammonia emissions from an ensemble of 9 plots with a resistance-analogue-16 compensation-point surface exchange scheme over a yearly meteorological database separated into 28-days 17 periods. A multi-factorial simulation scheme is used to test the effects of sensor number and heights, plot 18 dimensions, source strengths and background concentrations, on the quality of the inference method. We further 19 demonstrate by theoretical considerations in the case of an isolated plot that inferring emissions with diffusion 20 sensors integrating over daily periods will always lead to underestimations due to correlations between emissions 21 and atmospheric transfer. We evaluated these underestimations as -8% ± 6% of the emissions for a typical 22 western European climate. For multiple plots, we find that this method would lead to median underestimations of 23 -16% with an interquartile [-8% -22%] for two treatments differing by a factor of up to 20 and a control 24 treatment with no emissions. We further evaluate the methodology for varying background concentrations and 25ammonia emission patterns and demonstrate the low sensitivity of the method to these factors. The method was 26 also tested in a real case and proved to provide sound evaluations of ammonia losses from surface applied and 27 incorporated slurry. We hence showed that this novel method should be robust and suitable for estimating 28 ammonia emissions from agronomic plots. Further work should anyway be produced for validating this method 29 in real conditions. 30 31

Volatile organic compound fluxes over a winter wheat field by PTR-Qi-TOF-MS and eddy covariance

“…The FIDES concentration and flux footprint model (Flux Interpretation by Dispersion and ExchangeS) was used to evaluate the flux footprint and to infer the contribution of the VOC fluxes to the VOC concentrations measured at the site (Loubet et al, 2010;Carozzi et al, 2013;Loubet et al, 2018). The flux footprint ϕ (x, y) of the measurement mast is the probability density that the measured flux F originates from the field point of coordinates (x, y).…”

“…Here field has no units while H field has units of transfer resistance (s m −1 ). The model is based on the same analytical solution of the advection-diffusion equation as the Korman-Meixner model (Kormann and Meixner, 2001), All details of the model can be found in Loubet et al (2018).…”

Comment on acp-2020-1328

“…The FIDES concentration and flux footprint model (Flux Interpretation by Dispersion and ExchangeS) was used to evaluate the flux footprint and to infer the contribution of the VOC fluxes to the VOC concentration measured 295 at the site (Carozzi et al, 2013;Loubet et al, 2018;Loubet et al, 2010). The model is based on the same analytical solution of the advection-diffusion equation as the Korman-Meixner model (Kormann and Meixner, 2001), All details of the model can be found in (Loubet et al, 2018).…”