Suppression of dissolved organic carbon by sulfate induced acidification during simulated droughts

Clark, Joanna M.; Chapman, Pippa J.; Heathwaite, A. Louise; Adamson, John K.. 2006 Suppression of dissolved organic carbon by sulfate induced acidification during simulated droughts. Environmental Science & Technology, 40. 1776-1783. 10.1021/es051488c

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The relationship between dissolved organic carbon (DOC) and the acidification of soils and freshwaters by sulfate (SO42-) has been a topic of great debate over the last few decades. Most interest has focused on long-term acidification. Few have considered the influence of episodic drought-induced acidification in peatlands on DOC mobility, even through the increased acidity and ionic strength associated with the oxidation of reduced sulfur to SO42- are known to reduce DOC solubility. Reduced DOC concentrations during droughts have often been attributed to: (i) reduced hydrological export; (ii) physicochemical changes in the peat structure; or (iii) changes in the biological production and/or consumption of DOC. Our experimental drought simulations on peat cores showed that SO42- induced acidification reduced DOC concentrations during droughts. However, the relationships between SO42-/pH/ionic strength and DOC were only apparent when the reductions in observed DOC were expressed as a fraction of the estimated DOC concentration in the absence of SO42-, which were derived from soil depth, temperature, and water table data. This analysis showed that a pH fall from 4.3 to 3.5, due to a SO42- rise from <2.5 to 35 mg L-1, caused a 60% reduction in DOC concentrations. In contrast, poor correlations were recorded between SO42-/pH/ionic strength and the observed DOC data. As DOC both influences acidity and is influenced by acidity, the relative change in DOC needed to be considered to disentangle the effect of inputs of mineral acids into a system naturally dominated by variable concentrations of organic acids.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1021/es051488c
Programmes: CEH Programmes pre-2009 publications > Biodiversity > CC01A Detection and Attribution of Change in UK and European Ecosystems > CC01.1 Environmental Change Network (ECN)
CEH Sections: _ Environmental Chemistry & Pollution
ISSN: 0013-936X
Format Availability: Electronic, Print
NORA Subject Terms: Ecology and Environment
Date made live: 29 Jun 2007 16:39

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