Dynamics of UV‐driven hydrogen peroxide formation on an intertidal sandflat

Abstract

Photochemically produced H,O, was found to accumulate at micromolar concentrations in intertidal Waddcn Sea areas. Annual amplitudes of solar radiation lead to variations of the intertidal H,O, accumulation with concentrations between 1 and 4 p,mol liter 1 during summer, while winter concentrations were mostly CO.5 pmol liter-l. Diurnal variations of H,O, accumulation over daily low-tide periods in intertidal environments are determined by the incident solar radiation, the concentration of UV-absorbing dissolved organic carbon in the water, as well as the concomitant biological and chemical H,O, degradation within the sediment surface. The efficiency of photosynthetic available radiation (PAR), UVA and UVB photons for photochemical H,O, production was assessed using cut-off filters in the UVB and in different UVA ranges. UVB photons (295-320 nm) displayed an 1 i-fold higher efficiency compared to UVA (335-370 nm) and a 340-fold higher efficiency compared to PAR photons (>400 nm). A 10% ozone reduction leads to a doubling of UVB surface irradiance at 300 nm, which entails a 30 and 40% increase of the apparent intertidal H,O, concentrations. Progressive stratospheric ozone depletion via UVB-induced H,O, formation will have yet unpredictable effects on boreal and Antarctic intertidal ecosystems.

Using Limes and Synthetic Psoralens to Enhance Solar Disinfection of Water (SODIS): A Laboratory Evaluation with Norovirus, Escherichia coli, and MS2

“…12 The UV-A wavelengths are not absorbed by nucleic acids, and instead inactivate microorganisms by activating dissolved organic carbon (DOC) in water, which in turn leads to the formation of reactive oxygen species (ROS). 13,14 This form of disinfection is more than 1,000-fold slower than direct damage of UV-C. 15 Several researchers have looked for means to accelerate SODIS, using such compounds as riboflavin, TiO 2 , H 2 O 2 , and copper plus ascorbic acid. [16][17][18][19][20][21] Many of these compounds have photoactivity in the UV-A spectrum, thereby enhancing normally inefficient insults of UV-A against microorganisms.…”

Hydrogen peroxide production driven by UV-B in planktonic microorganisms: a photocatalytic factor in sea warming and ice melting in regions with ozone depletion?

“…Accordingly, to establish whether H 2 O 2 is photoproduced in microorganisms, plankton samples should be placed in the darkness enough time to suppress catalase activity (Angel et al 1999), and then measuring H 2 O 2 after a short exposure to UV-B (see above). However, due to the fact that H 2 O 2 produced in aquatic environments is highly unstable, H 2 O 2 measurements are always performed immediately (Abele-Oeschger et al 1997;Yocis et al 2000). By doing so, only traces of H 2 O 2 produced at the extracellular space by UV-B photoactivation of DOC have been thus far detected (Abele-Oeschger et al 1997;Yocis et al 2000), whilst massive H 2 O 2 generation by WPO in microorganisms would have systematically escaped experimental detection.…”

“…However, due to the fact that H 2 O 2 produced in aquatic environments is highly unstable, H 2 O 2 measurements are always performed immediately (Abele-Oeschger et al 1997;Yocis et al 2000). By doing so, only traces of H 2 O 2 produced at the extracellular space by UV-B photoactivation of DOC have been thus far detected (Abele-Oeschger et al 1997;Yocis et al 2000), whilst massive H 2 O 2 generation by WPO in microorganisms would have systematically escaped experimental detection. On the other hand, SH is one of the most variable factors in the climate system showing deviations of ±25% (Kiehl and Trenberth 1997), so changes in SH UV-B due to WPO-Cat would be hidden by that natural variability.…”

“…On the other hand, DOC and other UV-B absorbers at the extracellular space come mainly from plankton and follow a similar distribution, so the remaining UV-B not absorbed by planktonic proteins will also contribute to heat production at sea surface. In fact, the same UV-B wavelengths that activate WPO-Cat in microorganisms also activate the H 2 O 2 photoproduction by DOC at the extracellular space (Abele-Oeschger et al 1997;Yocis et al 2000), which could represent a soluble form of WPO-Cat. To sum up, UV-B disappearing suddenly in eutrophic waters would mostly become heat.…”

“…However, to study the effects of short-term exposure to UV-B on plankton, samples must be placed in the darkness for a while in order to compare the activity in samples exposed again to UV-B with that in samples that continue in the darkness. As catalase is suppressed in the darkness (Angel et al 1999), the detrimental effects observed in microorganisms suddenly brought from darkness to normal-higher levels of UV-B (1-3 W/m 2 ) (Herndl et al 1993) could be due to the well-known toxic effects of H 2 O 2 (Abele- Oeschger et al 1997;Angel et al 1999). From this perspective, the existence of WPO-Cat in microorganisms is consistent with the results of Herndl et al (1993).…”