Validation of Ogawa passive samplers for the determination of gaseous ammonia concentrations in agricultural settings

The Ogawa passive sampler (Ogawa USA, Pompano Beach, Florida) is a useful tool for monitoring atmospheric ammonia (NH3(g)) concentrations and assessing the effects of agricultural waste management practices on NH3(g) emissions. The Ogawa sampler, with filter-discs impregnated with citric acid, was used to trap and determine NH3(g) concentrations in a variety of agricultural settings. A wide range of NH3(g) concentrations can be monitored by varying the sampler exposure time, provided that no more than B10 mg of NH3-N are adsorbed on the acid-coated filters. Concentrations less than 1mg NH3-Nm 3 can be detected using long deployments (p14 days), while concentrations as great as 10mg NH3-Nm 3 may be determined in very short (e.g. 5min) deployments. Reproducibility ranged from 5% to 10% over the range of concentrations studied and passive determinations of NH3(g) were similar to those determined using dilute-acid gas scrubbers. Background levels of NH3(g) at a non-agricultural site in southern Delaware were typically o1 mg NH3-Nm . The air entering a chicken house was 10 mg NH3-Nm , reflecting the background levels in agricultural settings in this region. Within the house, concentrations p8.5mg NH3-Nm 3 were observed, reflecting the high rates of NH3(g) emission from chicken excreta. Using measured NH3(g) concentrations and poultry house ventilation rates, we estimate that each broiler grown to production size over 6 weeks contributes approximately 1973 g of NH3-N to the atmosphere, a value consistent with other published results. r 2003 Elsevier Science Ltd. All rights reserved.