Patterns of hydrogen peroxide among lakes of the Mackenzie Delta, western Canadian Arctic

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Abstract:

Dissolved organic carbon (DOC) in Mackenzie Delta lakes varies in composition and concentration, ranging from low concentrations and high colour in frequently flooded lakes to high concentrations in clear lakes that are infrequently flooded. DOC is a precursor to the photochemical production of hydrogen peroxide (H2O2) in lake waters. Here we assessed the patterns of H2O2 using three approaches: (i) H2O2 levels were tracked in 40 lakes during the open water season from the Arctic summer solstice (24 h sunlight) to late summer; (ii) diurnal dynamics of in situ H2O2 were tracked in a pair of lakes with contrasting DOC regimes (coloured vs. noncoloured DOC); and (iii) buildup of H2O2 was tracked in experimental microcosms of lake water exposed to manipulated UV levels. H2O2 levels were highest at the solstice and in intermittently flooded lakes. During 24 h daylight, lakes with contrasting DOC regimes showed cumulative build up of H2O2 during multiple cloudless days. Cumulatively, H2O2 was highest in the Delta lake with a higher DOC concentration and low in colour. H2O2 buildup in lake water shielded from UVB exposure was not significantly lower from microcosms under full sunlight. UVA was the most important in coloured DOC photobleaching and H2O2 production.

La composition et la concentration du carbone organique dissous (DOC) dans les lacs du delta du Mackenzie varient, allant de concentrations faibles et de colorations foncées dans les lacs à inondations fréquentes à des concentrations élevées dans les lacs clairs à inondations rares. DOC est un précurseur dans la production photochimique du peroxyde d'hydrogène (H2O2) dans les eaux de lac. Nous évaluons les patrons d'H2O2 d'après trois stratégies: (i) en suivant les concentrations d'H2O2 dans 40 lacs pendant la période d'eau libre depuis le solstice d'été de l'arctique (24 h d'éclairement) à la fin de l'été; (ii) en déterminant la dynamique journalière d'H2O2 in situ dans deux lacs à régimes de DOC différents (DOC incolore et DOC coloré) et (iii) en mesurant l'accumulation d'H2O2 dans des microcosmes expérimentaux d'eau de lac exposés à des niveaux variés d'UV. Les concentrations d'H2O2 sont maximales au solstice et dans les lacs inondés de façon intermittente. Durant l'éclairement de 24 h, les lacs possédant des régimes différents de DOC subissent une accumulation d'H2O2 lorsqu'il y a plusieurs jours de suite sans nuages. De façon cumulative, H2O2 atteint un maximum dans le lac du delta qui a une plus forte concentration de DOC et une couleur pâle. L'accumulation d'H2O2 dans l'eau de lac protégée de l'exposition à l'UVB n'est pas significativement plus basse que celle des microcosmes en plein soleil. L'UVA joue le rôle primordial dans le photo-blanchiment du DOC coloré et la production d'H2O2.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: September 1, 2006

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  • Published continuously since 1901 (under various titles), this monthly journal is the primary publishing vehicle for the multidisciplinary field of aquatic sciences. It publishes perspectives (syntheses, critiques, and re-evaluations), discussions (comments and replies), articles, and rapid communications, relating to current research on cells, organisms, populations, ecosystems, or processes that affect aquatic systems. The journal seeks to amplify, modify, question, or redirect accumulated knowledge in the field of fisheries and aquatic science. Occasional supplements are dedicated to single topics or to proceedings of international symposia.
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