H2O2 accumulation from photochemical production and atmospheric wet deposition in Antarctic coastal and off-shore waters of Potter Cove, King George Island, South Shetland Islands

Temporal and spatial variations of the hydrogen peroxide accumulation were measured in off-shore waters and in intertidal rockpools near Jubany Statio n, King George Island, South Shetland Islands. As H2O2 photoformation is ma inly driven by the short wavelength radiation in the UV-B and the UV-A rang e of the solar spectrum, the study was conducted between the beginning of O ctober and the end of December 1995, the period of Antarctic spring ozone d epletion. Wet deposition of H2O2 containing snow was identified as a major source of hydrogen peroxide in the surface waters of Potter Cove. As the co ncentrations of dissolved organic carbon (DOC)in Potter Cove surface waters were low(121 +/- 59 mu mol C l(-1)), when compared to the highly eutrophic ated waters on the German Wadden coast (6000-7000 mu mol C l(-1)), direct U V-induced DOC photo-oxidation was of only limited significance in the Antar ctic sampling site. Nonetheless, under experimental conditions, H2O2 photof ormation in Potter Cove surface waters amounted to 90 +/- 40 nmol H2O2 h(-1 ) l(-1) under a UV-transparent quartz plate. When high energy UV-B photons were cut-off by a WG320 filter formation continued at a rate of 66 +/- 29 n mol H2O2 h(-1) l(-1) due to UV-A and visible light photons. Samples from fr eshly deposited snow contained between 10 000 and 13 600 nmol H2O2 l(-1), a nd a snowfall event in mid November resulted in a maximum concentration of 1450 nmol H2O2 l(-1) in the upper 10 cm layer of Potter Cove surface waters . Maximal H2O2 concentrations in intertidal rockpools were even higher and reached up to 2000 nmol H2O2 l(-1) after the snowfall event. During a grid survey on December 17 1995, H2O2 concentrations and salinity displayed a no rth to south gradient, with higher concentrations and PSU at the south coas t of the cove. The reasons for this spatial inhomogenety are as yet unknown , but may relate to a minor local input of photo-reactive organic matter fr om creeks entering the cove in the south-east, as well as to waste water di scharge from the station, located on the south beach.