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Photochemical production and consumption of ammonium in a temperate river-sea system

Lookup NU author(s): Dr Vassilis Kitidis, Dr Guenther Uher, Professor Nick Owens, Professor Robert Upstill-Goddard

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Abstract

We carried out 12 irradiation experiments under artificial light using samples collected from two UK upland temperate rivers, the Tyne and the Tay. and from the Tyne estuary and adjacent coastal North Sea waters. During these experiments, we followed concentration changes of ammonium (NH4+) and spectral changes of chromophoric dissolved organic matter (CDOM). In all experiments CDOM absorbance followed pseudo-first-order loss kinetics and photochemical NH4+ production occurred consistently. However, the patterns of NH4+ concentration changes with time were complex. Experiments in which irradiated waters were sampled at approximately 10 min intervals revealed an initial lag phase of similar to 30 to 120 min during which NH4+ concentrations did not change significantly. This lag phase was followed by a net photoproduction phase, and finally an apparent NH4+ consumption phase. Such behaviour has not previously been reported and appeared to be independent of sample origin, initial NH4+ concentration and initial CDOM absorption coefficient at 350 nm (a(350)). The observed behaviour could be described by a 3-stage irreversible reaction model: A -> B -> NH4+-> D with first-order rate constants ka, kb and kc for the 3 consecutive reaction steps. Both ka and kc were significantly correlated (p


Publication metadata

Author(s): Kitidis V, Uher G, Woodward EMS, Owens NJP, Upstill-Goddard RC

Publication type: Article

Publication status: Published

Journal: Marine Chemistry

Year: 2008

Volume: 112

Issue: 1-2

Pages: 118-127

ISSN (print): 0304-4203

ISSN (electronic): 0304-4203

Publisher: Elsevier BV

URL: http://dx.doi.org/10.1016/j.marchem.2008.07.005

DOI: 10.1016/j.marchem.2008.07.005


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