Atmospheric sulfur chemistry and cloud condensation nuclei (CCN) concentrations over the northeastern pacific coast
- Georgia Institute of Technology, Atlanta, GA (United States)
- Univ. of Washington, Seattle, WA (United States)
Correlated measurements of dimethylsulfide (DMS), gas phase dimethylsulfoxide (DMSO), methane-sulfonic acid (MSA)(g), sulfuric acid (H{sub 2}SO{sub 4}), and cloud condensation nuclei (CCN) were conducted in April 1991 at a Pacific coastal site in northern Washington. Measurements of SO{sub 2}, aerosol methanesulfonate (MSA)(p), and non-sea-salt sulfate (nss-SO{sub 4}) concentrations were also included. Maximum DMS concentrations between 100 and 240 pptv were observed when the measurement site (480 m above sea level) was embedded in clouds and air from the marine boundary layer was flowing upslope to the site. DMS levels measured in continental air and/or above the mixed layer were typically less than 20 pptv. The sulfur gases DMSO, H{sub 2}SO{sub 4}, and MSA(g) were measured in real time on a continuous basis (once every 60-150 s) using selected ion chemical ionization mass spectrometry. Corresponding concentrations ranged between <0.5-3.2 pptv, 0.001-1.19 pptv, and 0.002-0.19 pptv, respectively. All three sulfur gases showed significant diel variations mostly in phase with each other. Their corresponding lifetimes in the marine atmosphere are estimated to be of the order of a few hours. CCN concentrations measured in marine air ranged roughly between 10-200 cm{sup {minus}3} and 200-400 cm{sup {minus}3} at 0.3% and 0.9% supersaturation, respectively. A statistical analysis using only data obtained in predominantly marine air and during non-fog/non-precipitation periods showed significant correlations between individual sulfur species and between CCN (0.3% ss) and H{sub 2}SO{sub 4} and CCN (0.3% ss) and nss- SO{sub 4}. The results indirectly support a relationship between DMS and CCN concentrations. However, other observations also suggest that at higher supersaturations (0.9%), compounds less soluble than sulfate may become important in marine CCN formation. 43 refs., 7 figs., 1 tab.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 91350
- Journal Information:
- Journal of Geophysical Research, Vol. 98, Issue D7; Other Information: PBD: 20 Jul 1993
- Country of Publication:
- United States
- Language:
- English
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