Ammonia concentrations and modeling of inorganic particulate matter in the vicinity of an egg production facility in Southeastern USA
2014
Li, Qian-Feng | Wang-Li, Lingjuan | Shah, Sanjay B. | Jayanty, R. K. M. | Bloomfield, Peter
Ammonia (NH₃) is an important base gas and can react with acidic species to form atmospheric aerosols. Due to the rapid growth of poultry and swine production in the North Carolina Coastal Plain, atmospheric NH₃concentrations across the region have subsequently increased. Ammonia concentrations and inorganic particulate matter (PM) at four ambient stations in the vicinity of an egg production facility were measured for 1 year using PM₂.₅speciation samplers with honeycomb denuders and ion chromatography (IC). Meanwhile, concentrations of NH₃and inorganic PM in one of the egg production houses were also simultaneously measured using a gas analyzer for NH₃and the filter pack plus IC method for inorganic PM. An equilibrium model-ISORROPIA II was applied to predict the behavior of inorganic aerosols in response to precursor gas concentrations and environmental parameters. Average ambient NH₃concentrations varied from 10.0 to 27.0 μg/m³, and they were negatively correlated with the distances from the ambient location to the nearest egg production house exhausts. Ambient NH₃concentrations were higher in warm seasons than in cold seasons. Measured NH₃concentrations agreed well with ISORROPIA II model predictions at all sampling stations. For the ambient stations, there was a good agreement in particle phase NH₄⁺between the model simulation and observations. For the in-house station, the model simulation was applied to correct the overestimation of particle phase NH₄⁺due to gas phase NH₃breaking through the denuders. Changes in SO₄²⁻, NO₃⁻, and Cl⁻yield proportional changes in inorganic PM mass. Due to the abundance of NH₃gas in the vicinity area of the monitored farm, changes in NH₃concentrations had a small effect on inorganic PM mass. Aerosol equilibrium modeling may be used to assess the influence of precursor gas concentrations on inorganic PM formation when the measurements for some species are unavailable.
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