Hydrogen peroxide at the Bermuda Atlantic Time Series Station. Part 1: Temporal variability of atmospheric hydrogen peroxide and its influence on seawater concentrations

Diurnal and seasonal variations in atmospheric hydrogen peroxide concentrations were investigated during a summer and winter cruise aboard the R.V. 'Endeavor' at the Bermuda Atlantic Time Series Station. Rainwater peroxide concentrations in August displayed diel variability while no temporal H2O2 pattern was evident in March rain. Average concentrations in March were also significantly lower than August which indicates photochemical processes are involved in controlling hydrogen peroxide concentrations in marine rainwater falling over the open ocean. The range of gas phase hydrogen peroxide concentrations was between 1 and 6 ppbv and also exhibited a strong diurnal pattern during both August and March with concentration maxima in the early evening. The influence of atmospheric deposition on surface seawater hydrogen peroxide levels was also evaluated. Hydrogen peroxide depth profiles were measured on four separate occasions before and after rain events during the August sampling period. The input of rainfall hydrogen peroxide was observed throughout the 25 meter mixed layer with surface concentrations two fold larger in the morning after a rain event. The integrated increase in hydrogen peroxide after the rain from 0 to 90 meters was 1,720 mu mol almost all of which could be accounted for by the peroxide added from rain. The data presented in this study represent the first detailed, simultaneous measurements of hydrogen peroxide in marine air, rain and surface seawater.