Experimental Assessment of Atmospheric Ammonia Dispersion and Short Range Dry Deposition in a Maize Canopy |
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Authors: | Loubet Benjamin Cellier Pierre |
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Institution: | (1) Institut National de la Recherche Agronomique (INRA), Thiverval-Grignon, France (author for correspondence, e-mail, 3081 5563) |
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Abstract: | In order to study the effect of thevegetation structure on atmospheric ammonia(NH3) dispersion and deposition, anexperiment was set up near Paris, in July 1997.Between 12 and 162 m downwind of a 200 m line-source releasing 600 to 1200 g NH3hr-1placed at the top of a maize canopy, NH3concentration was measured, within and above thecanopy, with a set of 30 active, acid-coateddenuders over periods of 2 to 3 hr. Eight datasets were collected over a one-month period.NH3 concentration decreased sharply withdistance to the source, from up to800 g NH3 m-3 at 12 m, to lessthan 10 g NH3 m-3 at 162 m andshowed strong vertical gradients. Within thecanopy, the concentration scaled using thefriction velocity, the canopy height, and thesource strength, exhibited a universal power lawrelationship as a function of the normaliseddownwind distance from the source. A mass balancemethod and a resistance model approach were usedas independent estimates of the cumulateddeposition at 162 m downwind from the source,which range between 1 and 29% of the emittedNH3. Both methods agreed approximately inmagnitude. A sensitivity analysis showed that thecuticular uptake and the compensation point aremajor parameters that needs to be bettercharacterised under high NH3 concentrationif one wants to improve NH3 short-rangedeposition modelling. |
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Keywords: | atmospheric ammonia dry deposition line source experiment NH3 short-range dispersion |
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