The variation of hydrogen peroxide in rainwater over the South and CentralAtlantic Ocean

The concentration of hydrogen peroxide in rainwater over the South and Cent ral Atlantic Ocean was determined. The rainwater samples were collected dur ing an Intergovernmental Oceanographic Commission (IOC) sponsored baseline expedition in May and June 1996. The concentration of hydrogen peroxide was determined on diluted samples using a cobalt-catalyzed luminol chemilumine sence method. The concentration of hydrogen peroxide in rainwater varied fr om 3.5 to 71 mu M with an average (n = 25) and standard deviation of 26 and 22 mu M, respectively. These are similar to previously reported average hy drogen peroxide concentrations in marine rainwater of the Gulf of Mexico (4 0 mu M), the western Atlantic Ocean (13 mu M), and Florida Keys (28 mu M). The concentration of hydrogen peroxide in rainwater varied with time of the day, with lower concentrations in early morning and higher concentrations in the late afternoon. The rainwater concentration of hydrogen peroxide als o decreased during a rainstorm that may be an indication of a washout effec t. The general levels of hydrogen peroxide in rainwater reported here and e lsewhere together with the satellite-measured global distribution of precip itation indicate that wet deposition could affect water column hydrogen per oxide significantly in certain parts of the world. (C) 2000 Elsevier Scienc e Ltd. All rights reserved.