Summary: Atmospheric Environment 38 (2004) 3469­3480
Ammonia flux and dry deposition velocity from near-surface
concentration gradient measurements over a grass surface
in North Carolina
Sharon B. Phillips*, S. Pal Arya, Viney P. Aneja
Department of Marine, Earth, and Atmospheric Sciences, Box 8208, Jordan Hall, North Carolina State University,
Raleigh, NC 27695, USA
Received 11 September 2003; accepted 23 February 2004
Abstract
Atmospheric ammonia concentrations were measured during fall 2001, winter, spring, and summer 2002 over natural
surfaces in North Carolina where animal farms and waste storage and treatment lagoons (which are known to emit
ammonia) at two heights (2 and 6 m) above the surface employing an arrangement of two Thermo Environmental
Instruments, Inc. Model 17C chemiluminescent nitrogen oxides (NOX)­ammonia (NH3) analyzers along with a
solenoid for each analyzer to alternate measurements between the two elevations. Simultaneously, mean winds and
temperatures are also measured at the same two heights. The micrometeorological gradient method is used in
conjunction with the Monin­Obukhov similarity theory, to estimate the vertical flux and dry deposition velocity of
ammonia under different meteorological conditions. Diurnal and seasonal variations of ammonia flux and dry
deposition velocity were investigated under a wide range of wind and atmospheric stability conditions yielding hourly
variation of NH3 fluxes and deposition during each seasonal campaign. Fall average NH3 concentrations were generally
the highest with daytime concentrations of 7.6076.54 mg mÀ3

Source: Aneja, Viney P. - Department of Marine, Earth and Atmospheric Sciences, North Carolina State University

Collections: Environmental Sciences and Ecology; Geosciences