The Radiello Diffusive Sampler
The Radiello-brand sampler, a passive device for measuring atmospheric ammonia (or other gases), is a simple diffusion-type sampler with no moving parts. It works on diffusion theory, where ammonia is sorbed on the interior surface. This induces a concentration gradient from the outside of the sampler to the inside of the sampler.
Phosphoric acid is impregnated on the interior cartridge. This cartridge is placed inside the porous outer body, which provides a predictable diffusion distance and a reproducible diffusion rate of ammonia gas to the interior sorbent. For analysis, the sampler is returned to the laboratory, where the cartridges are removed, and the ammonia (as NH4+) is removed by sonication in deionized water.
Laboratory analysis for ammonium is accomplished by Flow Injection Analysis (FIA).
The sampler shelter consists of an inverted plastic shelter permanently fastened to an aluminum u-channel mounting bracket (see diagram). The shelter is erected such that the lower edge is 2 meters (80 inches) above surrounding surfaces. Triplicate ammonia samples are mounted within the shelter.
Samplers are not mounted near plumbing stacks, chimneys, vents, exhausts or other possible sources of direct ammonia emissions.
The vertical arm of the aluminum bracket can be fastened to a metal fence post. Alternatively, the shelter can be mounted on a suitable wooden post or pole by using screws (or small lag bolts) driven through the predrilled holes in the lower part of the bracket.