The distribution of hydrogen peroxide in seawater of the Central Atlantic Ocean and in river waters of southern Mississippi and Louisiana

Jinchun Yuan

Abstract

A series of methodological studies were conducted for determining hydrogen peroxide in seawater and river waters. These studies led to the development of an analytical method for determining hydrogen peroxide in seawater, based on the catalytic (cobalt (II)) oxidation of luminol by hydrogen peroxide. The accuracy and precision of the method can be as low as 0.42 nM and 17 pM, respectively. The methodological studies also indicated that the I 3 - -based method is applicable for determining hydrogen peroxide in river waters. A series of photochemical studies of hydrogen peroxide were conducted in the South and Central Atlantic Ocean. Diel variations of ∼25 nM, a dark decay half-life of 5.5 days, and a noon time photochemcial production rate of 8.3 nM/hr were observed in surface waters. Three types of profiles were observed: surface maximum, surface mixed, and sub-surface maximum. In the surface waters, hydrogen peroxide increased with latitude from about 24 nM in the south (33.8°S) to about 80 nM in the north (8.9°N). This latitudinal variation of hydrogen peroxide correlated with solar irradiance, wet deposition, depth of the mixed layer, and possibly total organic carbon. A one-dimensional model, including eddy diffusion, photochemical production, and dark decay, is used to simulate the dynamics of hydrogen peroxide in surface seawater. Eddy diffusion, photo-production, and decay are calculated using field-measured parameters. With some adjustment of the decay rate, the numerical solution of hydrogen peroxide in surface waters agrees well with the field measurements. A series of photochemical studies were also conducted on the lower Mississippi River and the Pearl River, Mississippi. Diel cycles of hydrogen peroxide were observed in the Mississippi and Pearl rivers, respectively. Hydrogen peroxide half-life (14 min) in the Pearl River is significantly shorter than in seawater. In the Mississippi River plume, the concentration of hydrogen peroxide decreases with decreasing salinity. The concentrations of hydrogen peroxide in these rivers (<5 to><800 >nM) are lower than reported for the other rivers (∼3 μM).