Measurements of atmospheric gas-phase and aqueousphase hydrogen peroxide concentrations in winter on the east coast of the United States

Measurements of the concentrations of hydrogen peroxide (H₂O₂) in the gas-phase and in cloud water were obtained in the vicinity of the Carolina Coast of the United States between late January and early March, 1986. The gas-phase concentrations were always less than 2.4 ppbv and generally less than 1 ppbv. Vertical profiles of H₂O₂ in the clear air around clouds and storm systems were highly variable. The concentrations of H₂O₂ in the cloud water ranged from the detection limit of 0.3 μM to 112 μM, with the higher values generally occurring in the vicinity of lightning activity. Hydrogen peroxide concentrations in cloud water were well below those calculated to be in Henry’s law equilibrium with the gas-phase concentrations of H₂O₂ in the cloudy air. This is attributed to the rapid depletion of aqueous-phase H₂O₂ as it oxidizes S(IV).