New instrumentation for the detection of sulfur dioxide in the remote atmosphere

Sulfur gases are an important chemical component of the atmosphere. Gaseous sulfur compounds effect the acidity of rainwater and are important precursors to aerosol particles which affect public health, climate and visibility of scenic vistas such as the Grand Canyon. Sulfate aerosols are also known to participate in ozone catalysis in the stratosphere. A vast majority of the gaseous sulfur cycling through the atmosphere will exist as sulfur dioxide (SO₂) at some time during its atmospheric lifetime. Since SO ₂ is a primary component of the atmospheric sulfur cycle, quality measurements of this gas are important to understanding the cycling of sulfur through the atmosphere. The mixing ratio of SO₂ in the atmosphere can be as low as a few 10's of parts-per-trillion by volume (pptv) in unpolluted areas and as high as 100's of parts-per-billion by volume (ppbv) near industrial centers. Obtaining SO₂ measurements with mixing ratios that can differ by 105 in magnitude is a difficult task, especially for mixing ratios less than a few hundred pptv.; The Diffusion Denuder/Sulfur Chemiluminescence Detector (DD/SCD) was developed further and tested in a rigorously blind comparison under controlled laboratory conditions. The DD/SCD exhibited excellent sensitivity and little-to-no interference from other trace gases. The DD/SCD performance was comparable to that of other state-of-the-art instruments developed for measuring SO ₂ in the remote atmosphere.; The Continuous SO₂ Detector was developed to overcome the limitation of long sampling times (4 to 90 minutes) inherent in the DD/SCD and other state-of-the-art techniques. The Continuous SO₂ Detector (CSD) was developed based on the design of the DD/SCD, but has been optimized for sensitive, high-time resolved measurements of SO₂ in air. Sensitive, high-time resolved measurements would be beneficial for studying atmospheric SO₂ over large geographical areas from a moving sampling platform such as an aircraft. The current prototype of the CSD is capable of measuring SO₂ at mixing ratios of less than 100 pptv on the order of seconds. The DD/SCD, CSD and an automated, computer controlled dynamic dilution system described in this thesis represent a suite of instruments for the measurement of SO₂ in the remote atmosphere.