Sources and ages of dissolved organic matter in peatland streams: evidence from chemistry mixture modelling and radiocarbon data

Tipping, E.; Billett, M.F.; Bryant, CC.L.; Buckingham, S.; Thacker, S.A.. 2010 Sources and ages of dissolved organic matter in peatland streams: evidence from chemistry mixture modelling and radiocarbon data. Biogeochemistry, 100. 121-137.

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Monitoring data over the period 1994-2007 were analysed for three streams (Cottage Hill Sike, CHS; Rough Sike , RS; Trout Beck, TB) draining blanket peat underlain by glacial clay and limestone-rich sub-strata at Moor House (Northern England). Dissolved organic carbon concentration, [DOC], showed complex relationships with both discharge and calcium concentration, [Ca]. A model based on [Ca] was constructed to simulate stream [DOC] by mixing dissolved organic matter (DOM) from shallow peat, quantified by measured [DOC] (15-30 mg l-1) in peat porewater, with DOM assumed to be present at a constant concentration (c. 5 mg l-1) in groundwater. A temperature-based adjustment to the measured porewater [DOC] was required to account for relatively low streamwater [DOC] during winter and spring. The fitted model reproduced short-term variation in streamwater [DOC] satisfactorily, in particular variability in RS and TB due to groundwater contributions. Streamwater DOM is largely derived from surface peat, which accounts for more than 96% of the total DOC flux in both RS and TB, and 100% in CHS. Model outputs were combined with streamwater and porewater DO14C data to estimate the 14C contents, and thereby the ages, of DOM from peat and groundwater. The peat-derived DOM is five years old on average, with most of it very recently formed. The derived age of groundwater DOM (8500 years) is comparable to the 4000-7000 years estimated from the DO14C of water extracts of clay underlying the peat, suggesting that the clay is the source of groundwater DOM.

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: Shore
Billett (to November 2013)
ISSN: 0168-2563
Additional Keywords: carbon isotopes, discharge, dissolved organic matter, groundwater, Peat, Stream
NORA Subject Terms: Ecology and Environment
Date made live: 18 Oct 2010 13:53 +0 (UTC)

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