Experimental simulation of the effects of extreme climatic events on major ions, acidity and dissolved organic carbon leaching from a forested catchment, Gardsjon, Sweden

Moldan, Filip; Hruska, Jakub; Evans, Christopher D. ORCID:; Hauhs, Michael. 2012 Experimental simulation of the effects of extreme climatic events on major ions, acidity and dissolved organic carbon leaching from a forested catchment, Gardsjon, Sweden. Biogeochemistry, 107 (1-3). 455-469.

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Climate change is predicted to lead to an increase in extreme rainfall and, in coastal areas, sea-salt deposition events. The impacts of these two climatic extremes on stream hydrochemistry were separately evaluated via a novel watering manipulation at the Gårdsjön experimental catchment, SW Sweden. In summer 2004, a 2000 m2 hillslope draining to a defined stream reach was brought to a high-flow hydrological steady state for a nine day period by sustained addition of ‘clean’ water using a distributed sprinkler system. Marine ions were then added, to generate a realistic ‘sea salt’ episode. A remarkably well constrained hydrological response was observed, such that a simple two-compartment mixing model could reasonably well reproduce observed conservative tracer (chloride, Cl) measurements, and 78% of added water was recovered in runoff. Stream base cation concentrations and acidity responded predictably to clean water and sea-salt addition, with the former leading to an increase in pH and acid neutralising capacity, and the latter to episodic acidification through hydrogen ion and aluminium displacement from soil exchange sites by marine base cations. Anion responses were less predictable: water addition caused a flush of nitrate, but this was apparently independent of rainfall composition. Sulphate remained near-constant during clean water addition but declined sharply during sea-salt addition, indicative of a strong, pH-dependent solubility control on leaching, presumably adsorption/desorption in the mineral soil. Most strikingly, dissolved organic carbon (DOC) concentrations were stable during clean water addition but varied dramatically in response to sea-salt addition, exhibiting a strong negative correlation with Cl concentrations in water draining the organic soil. These observations provide a robust experimental verification of the hypothesis that deposition chemistry, through its influence on acidity and/or ionic strength, has a major influence on DOC leaching to surface waters.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: CEH Topics & Objectives 2009 - 2012 > Biogeochemistry > BGC Topic 1 - Monitoring and Interpretation of Biogeochemical and Climate Changes > BGC - 1.3 - Quantify & attribute changes in biogeochemiical cycles ...
UKCEH and CEH Sections/Science Areas: Emmett
ISSN: 0168-2563
Additional Information. Not used in RCUK Gateway to Research.: The attached document is the author’s final manuscript version of the journal article, incorporating any revisions agreed during the peer review process. Some differences between this and the publisher’s version remain. You are advised to consult the publisher’s version if you wish to cite from this article. The final publication is available at
Additional Keywords: acidity, climate change, DOC, ionic strength, hydrological episodes, nitrogen leaching, sea salt, sulphate adsorption, Gårdsjön
NORA Subject Terms: Ecology and Environment
Date made live: 16 Dec 2011 10:04 +0 (UTC)

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