Investigating the stomatal, cuticular and soil ammonia fluxes over a growing tritical crop under high acidic loads

[摘要] Ammonia concentration and fluxes were measured above agrowing triticale field for two months during May and June 2010 at theNitroEurope crop site in Grignon (Fr-Gri) near Paris, France. Themeasurement campaign started 15 days following a 40 kg N ha⁻¹application of an ammonium nitrate solution. A new mini-wedd (Wet EffluentDenuder) flow injection analyser with three channels (ROSAA, RObust andSensitive Ammonia Analyser) was used to measure NH₃ fluxes using theaerodynamic gradient method. The measured ammonia concentrations varied from0.01 to 39 μg NH₃ m⁻³ and were largely influenced byadvection from the nearby farm. The ammonia fluxes ranged from –560 to220 ng NH₃ m⁻² s⁻¹ and averaged–29 ng NH₃ m⁻² s⁻¹. During some periods the largedeposition fluxes could only be explained by a very small surfaceresistance, which may be partly due to the high concentrations of certainacid gases (HNO₃ and SO₂) observed in this suburban area. Ammoniaemissions were also observed. The canopy compensation point C_c wasaround 1.5 μg NH₃ m⁻³ on average. The canopy emissionpotential Γ_c (C_c normalised for the temperature response ofthe Henry equilibrium) decreased over the course of the measurement campaignfrom Γ_c = 2200 to Γ_c = 450, the latter value beingclose to the median stomatal emission potential (Γ_s) and lowerthan the median ground emission potential (Γ_g) for managedecosystems reported in the literature. The temporal dynamics of the measuredNH₃ flux compared well with the Surfatm-NH₃ model using fittedparameters. The subjectivity of the model fitting is discussed based on asensitivity analysis.

[学科分类] 地球化学与岩石