The SO4:Cl Ratio in Oceanic Rainwater

Abstract

Rainwater samples collected on 20 islands in the Pacific and Atlantic oceans since 1961 have been analyzed for dissolved sulfate and chloride ion concentrations. Samples from sparsely populated islands have S04: CI ratios approximately equal to that observed in seawater. Notable exceptions are samples from Midway and Christmas islands, which are enriched in sulfate, and those from the ocean stations Echo, Papa, and Victor, which are depleted in sulfate. The 8180 of the oxygen in the S04 ion ranges from 9.5 %0 in seawater and unpolluted rain to 11.2 %0 in rain derived from a continental air mass. Aerosols and snow samples have higher 8180 values of 11.2 to 14.8%0 due to their greater efficiency in trapping locally produced sulfate pollutants.