The cycling of sulfur dioxide in the marine boundary layer

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)

First Committee Member

Eric S. Saltzman, Committee Chair


The atmospheric cycling of sulfur dioxide (SO$\sb2$) is examined through the use of field measurements and photochemical modeling. A question exists as to whether or not SO$\sb2$ is a major product of dimethylsulfide (DMS) oxidation and subsequently important in the formation of new particles and cloud condensation nuclei (CCN). The relative magnitudes of the different sources and sinks of SO$\sb2$ in the remote marine boundary layer are looked at using field measurements of SO$\sb2$, DMS, and hydrogen sulfide (H$\sb2$S) and a time dependent photochemical box model of an air mass in the marine boundary layer.A new automated technique for measuring SO$\sb2$ was developed. It enables continuous real-time measurement of SO$\sb2$ using HPLC/Fluorescence at parts-per-trillion levels. Atmospheric and seawater DMS and atmospheric H$\sb2$S were also measured during these cruises in order to define the biogenic sources of SO$\sb2$.The observed SO$\sb2$ levels in the marine boundary layer are much lower than those predicted by current photochemical models using the measured DMS concentrations. Also, current models predict that SO$\sb2$ should have a pronounced diel cycle that is anticorrelated to that of DMS, however there is no observable diel cycle in the SO$\sb2$ data. Using a time-dependent photochemical box model and a model of the aqueous phase sea-salt aerosol chemistry, we examine the role of heterogeneous loss to sea-salt aerosols as a potentially important but previously unaccounted for sink for SO$\sb2$ in the marine boundary layer. Our results indicate that this is a large sink for SO$\sb2$ in this region.


Biogeochemistry; Environmental Sciences; Geochemistry

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