Changes in the South Coast air Basin atmospheric sulfur budget between 2002 and 2008

Observations of airborne sulfur in the South Coast air Basin obtained during the 2008 NASA DC-8 ARCTAS/CARB field campaign were compared to those obtained during the 2002 NOAA WP-3D ITCT field campaign. In the 2002 study, no discernible impact of marine vessel emissions on atmospheric sulfur was observed. However, in 2008, large sulfur contributions were observed from sources along the coast and offshore, indicating ships and refineries potentially contribute a large portion of the sulfur in the South Coast air Basin. On-road traffic emissions in 2008 appear to have decreased compared to those observed in 2002, due most likely to stricter regulations on sulfur content in automotive fuels. These in-situ observations are compared to OMI SO2 column data to aid in identifying long-term trends in South Coast airborne sulfur, as well as to evaluate the potential for spatial and temporal oversampling and undersampling during the aircraft campaigns.