A sampler for measuring atmospheric ammonia flux

Abstract

This paper describes the design, construction and testing of a simple sampling device for determining ammonia fluxes in the atmosphere. Sampler performance was predicted theoretically and tested in a wind tunnel, the laboratory and in the field. The results showed that air flowed through the sampler at a rate linearly proportional to the external wind speed and that the ammonia it contained was absorbed quantitatively by the sampler. The mass of ammonia, M, collected by the instrument during a sampling period, t, is thus proportional to the mean convective flux density of ammonia, ( ) since , where u is the wind velocity, ϱ_N the ammonia density, A is the effective cross-sectional area of the sampler, and the overbar represents a time-mean.