Investigation of the Los Angeles Basin Atmospheric Sulfur Budget

Airborne sulfur, as gas phase SO2 and particle phase SO42-, was measured in Southern California by in situ instruments aboard the NASA DC-8 during the summer 2007 TC4 and summer 2008 ARCTAS/CARB missions. Two chemical ionization mass spectrometers with differing ionization methods provided independent measurements of SO2. High-resolution time-of-flight aerosol mass spectrometry and a mist chamber / ion chromatography system provided independent measurements of SO42-. Ion chromatography was used to measure SO42- in aqueous extracts of bulk aerosol samples. Observed sulfur concentrations are considerably greater than those predicted from known sulfur sources. We investigate previously underrepresented sulfur sources from ship and aircraft emissions.