Atmospheric Chemistry and Air/Surface Exchange of Ammonia in an Agricultural Region of the Southeast United States

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dc.contributor.advisor Wayne Robarge, Committee Member en_US Walker, John Thomas en_US 2010-04-02T19:07:16Z 2010-04-02T19:07:16Z 2005-04-28 en_US
dc.identifier.other etd-04252005-215055 en_US
dc.description.abstract Animal manure, synthetic fertilizer, and agricultural crops are the primary sources of atmospheric ammonia and together contribute approximately 64% of global emissions. Subsequently, mixed (i.e. animal and crop production) agricultural regions may experience high concentrations of ammonia in air and precipitation, along with elevated ambient inorganic PM[subscript 2.5] concentrations. In this study, the behavior of atmospheric ammonia is examined in eastern North Carolina where ammonia emissions from animal and crop production are high. Annular denuders are used to measure atmospheric concentrations of ammonia, acid gases, and inorganic aerosol. At a site influenced by high local ammonia emissions, annual ammonia and ammonium aerosol concentrations are 5.6 (±5.1) and 1.8 (±1.4) μg m⁻³, respectively. Variability in ammonia is highly correlated with ambient temperature, which is a controlling factor for ammonia emissions from animal manure. The mean concentration of total inorganic PM[subscript 2.5] at this site, which includes sulfate, nitrate, ammonium, and chloride, is 8.0 (±5.8) μg m⁻³. Sulfate, nitrate, ammonium, and chloride represent 53, 24, 22, and 1% of measured inorganic PM[subscript 2.5]. Ammonia contributes 72% of total ammonia + ammonium, on average. Equilibrium modeling of the gas + aerosol ammonium/sulfate/nitrate system shows that, under elevated ammonia, inorganic PM[subscript 2.5] is more sensitive to reductions in gas + aerosol concentrations of sulfate and nitrate relative to ammonia. Chemiluminescence technology is used as part of a micrometeorological flux measurement system to examine the air/surface exchange of ammonia over soybean at a second site with high local ammonia emissions. A mean flux of -10.8 ng m⁻² s⁻¹ indicates that the canopy was a net sink for ammonia, though emission fluxes occurred frequently during the late morning and early afternoon. The mean deposition velocity during the experiment was 3.3 mm s⁻¹. Measured deposition velocities indicate a large canopy resistance (median = 228 s m⁻¹), which is likely the result of very dry conditions. The net flux during the experiment corresponds to a dry deposition rate of 0.7 kg NH₃-N ha⁻¹ for the entire summer compared to wet deposition of 1.9 kg NH₄⁺-N ha⁻¹ at a nearby site during the same period. Dry deposition of ammonia accounted for approximately 0.3% of crop nitrogen requirements. en_US
dc.rights I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. en_US
dc.subject nitrogen deposition en_US
dc.subject micrometeorology en_US
dc.subject ammonium aerosol en_US
dc.subject ammonia en_US
dc.title Atmospheric Chemistry and Air/Surface Exchange of Ammonia in an Agricultural Region of the Southeast United States en_US PhD en_US dissertation en_US Soil Science en_US

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