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
