Mass-independent sulfur isotopic compositions in stratospheric volcanic eruptions

The observed mass-independent sulfur isotopic composition (Delta S-33) of volcanic sulfate from the Agung ( March 1963) and Pinatubo ( June 1991) eruptions recorded in the Antarctic snow provides a mechanism for documenting stratospheric events. The sign of Delta S-33 changes over time from an initial positive component to a negative value. Delta S-33 is created during photochemical oxidation of sulfur dioxide to sulfuric acid on a monthly time scale, which indicates a fast process. The reproducibility of the results reveals that Delta S-33 is a reliable tracer to chemically identify atmospheric processes involved during stratospheric volcanism.