Department of Earth System Science

Measurements of H₂O₂ in rainwater collected in Miami, Florida, and the Bahama Islands area indicate the presence of H₂O₂concentration levels ranging from (1–7)×10⁻⁵ M. No systematic trends in H₂O₂ concentration were observed during an individual storm, in marked contrast to the behavior of other anions (e.g., [NO₃ ⁻], [SO₄ ⁼], and [Cl⁻]). The data suggest that a substantial fraction of the H₂O₂found in precipitation is generated by aqueous-phase reactions within the cloudwater rather than via rainout and washout of gaseous H₂O₂.