Evaluation of ammonia fluxes into the free atmosphere over Western Germany

Abstract

The upward flux densities of gaseous ammonia and particulate ammonium through a layer 400 m above ground were determined by aircraft measurements over a rural area in Western Germany. The flux densities were calculated according to the gradient method. The fluxes amounted to 118 ± 49 ?g/m 2 h NH 3 -N and 93 ± 47 ?g/m 2 h NH + 4 -N in summer and to 7 ± 14 ?g/m2h NH3-N and 23 ± 34 ?g/m 2 h NH + 4 -N in winter. When integrated over a year, the sum of these ammonia fluxes can be maintained by NH 3 volatilization from domestic animal excrements. The NH3 liberation from mineral fertilizer and natural soils contributes only a small amount to the overall production rate. Most of the NH 3 and NH + 4 diffusing upwards into the middle troposphere will eventually be incorporated in rain. For the conversion of gaseous NH 3 to particulate NH + 4 in the first 400 m of the atmosphere a lower limit for a pseudo first-order reaction rate constant of 1–2 × 10 -5 s -1 was deduced from flux density considerations. DOI: 10.1111/j.2153-3490.1980.tb01721.x