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| Titel |
Dissolved organic carbon dynamics in a UK podzolic moorland catchment: linking storm hydrochemistry, flow path analysis and sorption experiments |
| VerfasserIn |
M. I. Stutter, S. M. Dunn, D. G. Lumsdon |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 9, no. 6 ; Nr. 9, no. 6 (2012-06-18), S.2159-2175 |
| Datensatznummer |
250007124
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| Publikation (Nr.) |
 copernicus.org/bg-9-2159-2012.pdf |
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| Zusammenfassung |
| Better knowledge of spatial and temporal delivery of dissolved organic carbon
(DOC) in small catchments is required to understand the mechanisms behind
reported long-term changes in C fluxes from some peatlands. We monitored two
storms with contrasting seasons and antecedent conditions in a small upland
UK moorland catchment. We examined DOC concentrations and specific UV
absorbance (SUVA at 285 nm), together with solute concentrations required to
undertake end-member mixing analyses to define dominant flow paths
contributing to streamflow. This was combined with laboratory soil-solution
equilibrations. We aimed to resolve how seasonal biogeochemical processing of
DOC and flowpath changes in organo-mineral soils combine to affect DOC
exported via the stream. An August storm following a dry period gave maximum
DOC concentration of 10 mg l−1. Small DOC:DON ratios (16–28) and SUVA
(2.7–3.6 l mg−1 m−1) was attributed to filtration of aromatic
compounds associated with up to 53% B horizon flow contributions. This
selective filtration of high SUVA DOC was reproduced in the experimental
batch equilibration system. For a November storm, wetter antecedent soil
conditions led to enhanced soil connectivity with the stream and seven times
greater DOC stream-load (maximum concentration 16 mg l−1). This storm
had a 63% O horizon flow contribution at its peak, limited B horizon
buffering and consequently more aromatic DOC (SUVA
3.9–4.5 l mg−1 m−1 and DOC:DON ratio 35–43). We suggest that
simple mixing of waters from different flow paths cannot alone explain the
differences in DOC compositions between August and November and biogeochemical
processing of DOC is required to fully explain the observed stream DOC
dynamics. This preliminary evidence is in contrast to other studies proposing
hydrological controls on the nature of DOC delivered to streams. Although our
study is based only on two storms of very different hydrological and
biogeochemical periods, this should promote wider study of DOC biogeochemical
alteration in headwaters so that this be better incorporated in modelling to
predict the impacts of changes in DOC delivery to, and fate in, aquatic
systems. |
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