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 concentrat ions were investigated during a summer and winter cruise aboard the R.V. 'E ndeavor' at the Bermuda Atlantic Time Series Station. Rainwater peroxide co ncentrations in August displayed diel variability while no temporal H2O2 pa ttern 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 rainwat er falling over the open ocean. The range of gas phase hydrogen peroxide co ncentrations was between 1 and 6 ppbv and also exhibited a strong diurnal p attern during both August and March with concentration maxima in the early evening. The influence of atmospheric deposition on surface seawater hydrog en peroxide levels was also evaluated. Hydrogen peroxide depth profiles wer e measured on four separate occasions before and after rain events during t he August sampling period. The input of rainfall hydrogen peroxide was obse rved throughout the 25 meter mixed layer with surface concentrations two fo ld larger in the morning after a rain event. The integrated increase in hyd rogen peroxide after the rain from 0 to 90 meters was 1,720 mu mol almost a ll of which could be accounted for by the peroxide added from rain. The dat a presented in this study represent the first detailed, simultaneous measur ements of hydrogen peroxide in marine air, rain and surface seawater.