Abstract
Average particulate sulfate concentrations in air as measured from serial short-term samples collected on glass-fiber filters were consistently and significantly higher than those from single long-term samples. In investigating this anomaly, we found that significant amounts of extraneous sulfate can be formed on glass-fiber filters, presumably by oxidation of atmospheric sulfur dioxide, thus leading to highly inflated values for particulate sulfate as determined from short-term samples. The discrepancy is reduced with longer-term samples because the formation of sulfate from sulfur dioxide is surface-limited and reaches a saturation level.
