Date of Award

1-1-2009

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

College/School/Department

Department of Environmental Health Sciences

Content Description

1 online resource (vii, 136 pages) : illustrations (some color), color maps.

Dissertation/Thesis Chair

Xianliang Zhou

Committee Members

Haider Khwaja, Michael Kitto, James Schwab, Ying Wang, Xianliang Zhou

Keywords

Aerosol, Ammonia, Ammonium, Continually-Wetted Frit, Inter-comparison, LOPAP, Atmospheric nitrogen compounds, Air

Subject Categories

Analytical Chemistry | Atmospheric Sciences

Abstract

Ammonia is the primary base in the atmosphere. It reacts readily with atmospheric acids such as sulfuric acid, nitric acid, and hydrochloric acid to form ammonium salts that occur predominantly in the fine aerosol particle (PM2.5) fraction. The ability to measure ammonia species (NHx, the sum of gaseous NH3 and particulate NH4+) is essential for the investigation of atmospheric behaviors of NHx. In this dissertation work, a highly sensitive technique has been developed for the measurement of atmospheric NHx species. The method is based on aqueous scrubbing of the atmospheric NH3 and NH4+ using a Continually-Wetted Frit (CWF) sampler, followed by derivatization of the analyte to form a highly efficient light-absorbing indophenol in an on-line reaction coil, and analysis of the derivative by LOng-Path Absorption Photometry (LOPAP) using a miniaturized optical fiber spectrophotometer with a long-path liquid waveguide capillary cell. The method was first validated by calibrations using aqueous and gas-phase standards. The method possesses a wide linearity range of 0-35ppbv, a lower detection limit of 30 pptv, a good precision of 3% at 1.5-ppbv level, and a good sample time resolutions of ≤5 min. The method was further validated by inter-comparisons with several independent measurement techniques in the laboratory and in the field. These methods include Particle-Into-Liquid sampler/Ion Chromatography (PILS/IC), Quadropole-Aerosol Mass Spectrometry (Q-AMS) and integrated filter/ion chromatography (STN) for NH4+, and Tunable Diode Laser Absorption Spectroscopy (TDLAS), Wet Effusive Diffusion Denuder (WEDD), Ion Mobility Spectrometry (IMS), and laser acousto-opticalabsorption (Nitrolux) for NH3. The method was successfully deployed in 4 field measurement intensives: a rural forest site in University of Michigan Biological Station in Pellston, MI during the summer of 2003; an urban site on Queens College campus in Queens, NY, during the winter of 2004; a rural site in Pinnacle State Park in Addison, NY, during the summer of 2004; and an urban environment in downtown Albany, NY, during the summer of 2005. Atmospheric behaviors of NHx species were investigated in these environments, such as the partitioning of ammonia between the gas and the aerosol phases, the diurnal variation patterns, and the impact of metrological parameters on the variation of ammonia species such as wind direction, ambient temperature and precipitation. Back trajectories of air masses were calculated to aid the data interpretation.

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