New Zealand Journal of Marine and Freshwater Research abstracts

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Hydrogen peroxide concentrations in relation to optical properties in a fiord (Doubtful Sound, New Zealand)

Barrie M. Peake
Luke M. Mosley

Department of Chemistry
University of Otago
P.O. Box 56
Dunedin, New Zealand
email: bpeake@alkali.otago.ac.nz

Abstract  Hydrogen peroxide concentrations are reported for the first time in the surface low salinity layer (LSL) and underlying saline layer (SL) of a fiord. Measurements were made in Deep Cove and Hall Arm in Doubtful Sound, New Zealand under contrasting climatic conditions in early summer (October; wet, windy, and dull: November; dry, still, and sunny). Steady state peroxide concentrations in the range 100-400 nM rapidly declined with depth in the LSL and across the LSL/SL interface. Spectral measurements of absorption coefficients and downwelling irradiance indicated this is largely because of high levels of chromophoric dissolved organic matter (CDOM) in the LSL filtering out the UV component (<400 nm) of the sunlight that is mainly responsible for the photochemical formation of peroxide. The depth dependence of peroxide concentrations in the LSL was similar to that of the CDOM concentrations as measured by the corrected absorption coefficent at 340 nm. During the October sampling event there also appeared to be a contribution to the peroxide levels in the LSL at Deep Cove arising from the input of rainwater containing high levels of peroxide (1.7-7.5 μM).

Keywords  hydrogen peroxide; photochemistry; downward irradiance; absorbance; coloured dissolved organic matter; salinity; temperature; low salinity layer; mixing; rainwater; fiord; New Zealand

M02107; Received 24 December 2002; accepted 21 June 2004; Online publication date 5 August 2004
New Zealand Journal of Marine and Freshwater Research, 2004, Vol. 38: 729-741
0028-8330/04/3804-0729 © The Royal Society of New Zealand 2004

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