Wednesday, November 15, 2006

Measuring Ammonia Flux using Relaxed Eddy Accumulation and Honeycomb Denuders.

Kristen Baum and Jay Ham. Kansas State Univ, Dept of Agronomy, Manhattan, KS 66506

A Relaxed Eddy Accumulation (REA) system was designed for measuring gaseous and aerosol ammonia fluxes from a cattle feedlot.  The main components were a 3D sonic anemometer, an air flow and valve control system, and two speciation sampling cartridges (Chemcomb Model 3500) containing acid-coated glass honeycomb denuders.  The up- and down-moving eddies were sorted into different sampling cartridges via fast-response valves attached to the inlets of the cartridges.  The glass honeycomb denuders were coated with a phosphoric acid/methanol solution that trapped the gaseous ammonia.  The denuder extracts were analyzed using ion chromatography and the concentration difference between up- and down‑moving eddies was determined.  Fluxes were then calculated using REA theory.  This system has the advantage of having a very large capacity due to the honeycomb configuration of the denuders and can be used in the ammonia-rich environment of animal feeding operations.  In addition, multiple trace gases could be sampled simultaneously by using a combination of denuder coatings within the chemcomb cartridges.