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

Abstract

Temporal and spatial variations of the hydrogen peroxide accumulation were measured in off-shore waters and in intertidal rockpools near Jubany Station, King George Island, South Shetland Islands. As H₂O₂ photoformation is mainly driven by the short wavelength radiation in the UV-B and the UV-A range of the solar spectrum, the study was conducted between the beginning of October and the end of December 1995, the period of Antarctic spring ozone depletion. Wet deposition of H₂O₂ containing snow was identified as a major source of hydrogen peroxide in the surface waters of Potter Cove. As the concentrations of dissolved organic carbon (DOC) in Potter Cove surface waters were low (121 ± 59 μmol Cl⁻¹), when compared to the highly eutrophicated waters on the German Wadden coast (6000–7000 μmol Cl⁻¹), direct UV-induced DOC photo-oxidation was of only limited significance in the Antarctic sampling site. Nonetheless, under experimental conditions, H₂O₂ photoformation 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 nmol H₂O₂ h⁻¹ l⁻¹ due to UV-A and visible light photons. Samples from freshly deposited snow contained between 10 000 and 13 600 nmol H₂O₂ l⁻¹, and 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 north to south gradient, with higher concentrations and PSU at the south coast 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 from creeks entering the cove in the south-east, as well as to waste water discharge from the station, located on the south beach.