ORIGINS AND VARIATIONS OF NITRATE IN SOUTH POLAR PRECIPITATION

The resulting data reveal no evidence of a positive correlation between solar activity (11-yr solar cycle, low solar activity time periods, and solar proton events) and the NO3 content of south polar snow. This study of the NO3 content of high latitude precipitation suggests a major contribution by lightning (from a third to a half of the total) and by NOx produced in the lower stratosphere (approximately a third from N2O oxidation and to a lesser extent galactic cosmic rays) to the NO3 budget of this background atmosphere, the remaining portion being related to the present NOx surface sources of the Southern Hemisphere. Our data point to a decrease of NO3 content when very large amounts of sulfuric acid are present in South Pole snow layers. This observation suggests a possible interaction (via the hydroxyl radical) between S- and N-derived species when large quantities of SO2 are injected by volcanic eruptions. -from Authors