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| Titel |
Sediment flow paths and associated organic carbon dynamics across a Mediterranean catchment |
| VerfasserIn |
C. Boix-Fayos, E. Nadeu, J. M. Quiñonero, M. Martínez-Mena, M. Almagro, J. De Vente |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 19, no. 3 ; Nr. 19, no. 3 (2015-03-03), S.1209-1223 |
| Datensatznummer |
250120648
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| Publikation (Nr.) |
 copernicus.org/hess-19-1209-2015.pdf |
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| Zusammenfassung |
| Terrestrial sedimentation buries large amounts of organic carbon (OC)
annually, contributing to the terrestrial carbon sink. The temporal
significance of this sink will strongly depend on the attributes of the
depositional environment, but also on the characteristics of the OC reaching
these sites and its stability upon deposition. The goal of this study was to
characterise the OC during transport and stored in the depositional settings
of a medium-sized catchment (111 km2) in SE Spain, to better understand
how soil erosion and sediment transport processes determine catchment-scale
OC redistribution. Total organic carbon (TOC), mineral-associated organic
carbon (MOC), particulate organic carbon (POC), total nitrogen (N) and
particle size distributions were determined for soils (i), suspended
sediments (ii) and sediments stored in a variety of sinks such as sediment
wedges behind check dams (iii), channel bars (iv), a small delta in the
conjunction of the channel and a reservoir downstream (v), and the reservoir
at the outlet of the catchment (vi). The data show that the OC content of
sediments was approximately half of that in soils (9.42 ± 9.01 g kg−1
versus 20.45 ± 7.71 g kg−1, respectively) with important
variation between sediment deposits. Selectivity of mineral and organic
material during transport and deposition increased in a downstream
direction. The mineralisation, burial or in situ incorporation of OC in deposited
sediments depended on their transport processes and on their
post-sedimentary conditions. Upstream sediments (alluvial wedges) showed low
OC contents because they were partially mobilised by non-selective erosion
processes affecting deeper soil layers and with low selectivity of grain
sizes (e.g. gully and bank erosion). We hypothesise that the relatively
short transport distances, the effective preservation of OC in
microaggregates and the burial of sediments in the alluvial wedges gave rise
to low OC mineralisation, as is arguably indicated by C : N ratios similar to
those in soils. Deposits in middle stream areas (fluvial bars) were enriched
in sand, selected upon deposition and had low OC concentrations. Downstream,
sediment transported over longer distances was more selected, poorly
microaggregated, and with a prevalence of silt and clay fractions and MOC pool.
Overall, the study shows that OC redistribution in the studied catchment is
highly complex, and that the results obtained at finer scales cannot be
extrapolated at catchment scale. Selectivity of particles during detachment
and transport, and protection of OC during transport and deposition are key
for the concentration and quality of OC found at different depositional
settings. Hence, eco-geomorphological processes during the different phases
of the erosion cycle have important consequences for the temporal stability
and preservation of the buried OC and in turn for the OC budget. |
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