The influence of solar ultraviolet radiation on the photochemical production of H2O2 in the equatorial Atlantic Ocean

Abstract

Hydrogen peroxide (H 2 O 2 ) was measured in marine surface waters of the eastern Atlantic Ocean between 25jN and 25jS. H 2 O 2 concentrations decreased from 80 nM in the north to 20 nM in the south, in agreement with earlier observations. A diel cycle of H 2 O 2 production as a function of sunlight in surface waters was followed twice whilst the ship steamed southward. Around 23jN a distinct diel cycle could be measured which correlated well with irradiance conditions. The wavelength dependency of H 2 O 2 formation was studied near the equator. For 16 hours, water samples were incubated with wavelength bands of the solar spectrum, i.e. visible (VIS: 400 -700 nm), VIS and ultraviolet A radiation (UVAR: 320 -400 nm) and VIS, UVAR and ultraviolet B radiation (UVBR: 280 -320 nm). A significant relationship was found between wavelength band and the production of H 2 O 2 . In addition, a clear positive relationship between intensity and production was found. UVAR was 6.5 times more efficient than VIS in producing 1 nM of H 2 O 2 , whereas UVBR was 228 times more efficient than VIS. When these data were weighted with respect to the energy of the solar spectrum at zenith hour, 28% of the H 2 O 2 was formed by VIS, 23% was formed by UVAR and 48% was formed by UVBR. Considering the strong attenuation of UVBR in marine waters as compared with UVAR and VIS radiation, the role of UVAR deeper in the water column is recognised. Furthermore results of this research emphasise the importance of VIS radiation in the formation of H 2 O 2 .

The role of polysaccharides and diatom exudates in the redox cycling of Fe and the photoproduction of hydrogen peroxide in coastal seawaters

“…Reported photochemical production rates of H 2 O 2 in the Atlantic Ocean and Antarctic waters are much lower than those reported here, and range from 2.1 to 9.6 nmol L −1 h −1 (Gerringa et al, 2004;Obernosterer, 2000;Yocis et al, 2000;Yuan and Shiller, 2001). Gerringa et al (2004) calculated a net production rate of 7 nmol L −1 h −1 at irradiance levels of 2.8 (UVB), 43 (UVA) and 346 W m −2 (VIS/PAR) in 0.2 µm filtered water from the eastern Atlantic close to the Equator. These low rates are presumably due to lower DOC concentrations and higher decay rates due to colloids or enzymatic activity in natural waters (Moffett and Zafiriou, 1990;Petasne and Zika, 1997).…”

“…The PS in our study caused strong photogeneration of H 2 O 2 even under low light exposure probably due to the absence of peroxide destruction processes such as enzymatic decomposition of H 2 O 2 (Moffett and Zafiriou, 1990). Reported photochemical production rates of H 2 O 2 in the Atlantic Ocean and Antarctic waters are much lower than those reported here, and range from 2.1 to 9.6 nmol L −1 h −1 (Gerringa et al, 2004;Obernosterer, 2000;Yocis et al, 2000;Yuan and Shiller, 2001). Gerringa et al (2004) calculated a net production rate of 7 nmol L −1 h −1 at irradiance levels of 2.8 (UVB), 43 (UVA) and 346 W m −2 (VIS/PAR) in 0.2 µm filtered water from the eastern Atlantic close to the Equator.…”

Enhancement and inhibition of iron photoreduction by individual ligands in open ocean seawater

“…Hydrogenperoxide (H 2 O 2 ) was measured after Gerringa et al (2004) by fluorescence (Waters fluorometer, type 470) after enzyme-catalyzed dimerisation of (p-hydroxyphenyl) acetic acid (POHPAA) Kester, 1988, 1994b).…”

Real‐time detection of reactive oxygen species generation by marine phytoplankton using flow injection—chemiluminescence

“…Atmospheric deposition of peroxides, particularly during wet precipitation events, also results in a significant increase in ROS concentrations in surface waters (Cooper et al 1987;Yuan and Shiller 2000;Croot et al 2004;Gerringa et al 2004). In contrast, relatively little is known about the biological contributions to the ROS pool in surface waters.…”