Model-Measurement Comparison of Ammonia Bi-Directional Air-Surface Exchange Fluxes over Agricultural Fields

Zhuanshi He,Leiming Zhang,Lorraine Paige Wright

doi:10.4236/acs.2013.34048

Abstract

Modeled and measured bi-directional fluxes (BDFs) of ammonia (NH3) were compared over fertilized soybean and corn canopies for three intensive sampling periods: the first, during the summer of 2002 in Warsaw, North Carolina (NC), USA; and the second and third during the summer of 2007 in Lillington, NC. For the first and the third experimental periods, the BDF model produced reasonable diurnal flux patterns. The model also produced correct flux directions (emission and dry deposition) and magnitudes under dry and wet canopy conditions and during day and nighttime for these two periods. However, the model fails to produce the observed very high upward fluxes from the second sampling period due to the fertilization application (and thus being much higher soil emission potentials in the field than the default model values), although this can be improved by adjusting model input of soil emission potentials. Model-measurement comparison results suggest that the model is likely capable for improving long-term or regional scale ammonia predictions if implemented in chemical transport models replace the traditional dry deposition models, although modifications are needed when applying to specific situations.

Highlights

Ammonia (NH3) plays important roles in atmospheric chemical processes and biogeochemical cycles [1,2,3].NH3 is a major contributor to secondary inorganic aerosol compounds [4,5] which affect air quality and have direct and indirect impacts on climate [6]
Model-measurement comparison results suggest that the model is likely capable for improving long-term or regional scale ammonia predictions if implemented in chemical transport models replace the traditional dry deposition models, modifications are needed when applying to specific situations
We aim to evaluate the performance of the bi-directional dry deposition scheme of Zhang et al (2010) [30] using measured bi-directional fluxes of NH3 over fertilized soybean during the summer of 2002 in Warsaw, North Carolina (NC), USA, and over a fertilized corn canopy during the summer of 2007 in Lillington, NC

Summary

Introduction

Ammonia (NH3) plays important roles in atmospheric chemical processes and biogeochemical cycles [1,2,3].NH3 is a major contributor to secondary inorganic aerosol compounds [4,5] which affect air quality and have direct and indirect impacts on climate [6]. NH3 and ammonium ( NH4 ) represent important nutrients to the biosphere in some areas, and their deposition can fertilize nitrogen-limited ecosystems. The primary sources of NH3 are animal waste, ammonification of humus followed by emission from soils, losses of NH3-based fertilizers from soils, and industrial emissions [11]. The majority of these emissions come primarily from biological processes, as well as from byproducts of agricultural and waste production and processing of both human and animal waste [12,13,14].

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