A PASSIVE FLUX SAMPLER FOR MEASURING AMMONIA VOLATILIZATION FROM MANURE STORAGE FACILITIES

An integrated horizontal flux technique was tested for quantification of ammonia (NH3) emission from manure storage, The method is based on a simple and inexpensive passive flux sampler consisting of two discon nectable glass tubes, coated on the inside with oxalic acid, The flux sampler is mounted at a minimum of three heights, 20 to 100 cm above t he storage, on each of four masts, placed perpendicular to each other around the storage, The samplers continuously integrate the horizontal flux of NH3 at the various heights, After analysis of the NH3 content in the tubes facing the storage (exposed tubes) and surroundings (bac kground tubes), the vertical flux of NH3 from the storage can be obtai ned by application of mass balance equations (micrometeorological mass balance technique), For the measurements of NH3 volatilization from s lurry tanks or lagoons the technique is useful, because it is not affe cted by heterogenity in wind profiles and the masts with the passive f lux samplers are placed on the periphery of the slurry store. The flux samplers were able to accurately quantify NH3 volatilization from slu rry tanks, From above the rim of the slurry tank the horizontal net fl ux decline exponential with height. This may facilitate the calculatio n of the vertical flux of NH3. Bypass of NH3 between exposed and backg round tubes may occur during periods with high wind velocities (>10 m s(-1)) or when more than one-fifth of the oxalate in the exposed tube has reacted, However, if bypass occurs, a good estimate of NH3 volatil ization can still be obtained by addition of exposed and background tu bes, because the NH3 flux from storage are usually much greater than t he Bur from surroundings, Bypass due to high net horizontal fluxes of NH3 can be avoided by reducing the measuring period or increasing the length of the tubes, Storm conditions with heavy rain can flood the fl ux samplers and spoil the measurements, Within the study NH3 volatiliz ation from stored cattle slurry were measured eight times from October to December 1992. Daily loss rates of NH3 varied between 0.33 and 4.1 5 g NH3-N m(-2) d(-1).