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| Titel |
Influence of distributary channels on sediment and organic matter supply in the Po prodelta (Italy) |
| VerfasserIn |
Leonardo Langone, Stefano Miserocchi, Tommaso Tesi, Margherita Turchetto, Miguel A. Goñi, Amelia De Lazzari |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250057317
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| Zusammenfassung |
| From November 2008 through May 2009, the Po river (north of Italy) experienced several
floods exceeding 5,000 m3s-1. This long series of events ended with a large flood
in early May 2009 (Â 8,000 m3s-1). An event-response sampling was carried out
in the Po prodelta in April-May 2009 to characterize this latter event. The water
sampling was carried out during two periods of the May 2009 flood, including early in
the event under conditions of moderate river flow (Â 5000 m3s-1) and 24h later
during the peak discharge (Â 8000 m3s-1). At each station, profiles of conductivity,
transmittance, and fluorescence were acquired. Surface and bottom waters were sampled
to collect sediments in suspension. In addition, a few days before the May 2009
event, suspended sediments were collected at Pontelagoscuro gauging station, Â 90
km upstream from the coast. Biogeochemical compositions and sedimentological
characteristics of suspended samples were investigated using bulk and biomarker
analyses.
During moderate flow, the water column did not show evidence of plume penetration.
Stations re-occupied 24h later exhibited marked physical and biogeochemical changes during
the peak flood. However, the concentration of terrestrially-derived material in surface waters
was still less then expected. These results suggested that, since material enters the Adriatic as
buoyancy-driven flow with a reduced transport capacity, settling and flocculation processes
result in trapping a significant fraction of land-derived material in shallow sediments and/or
within distributary channels.
A two end-member mixing model was used to quantify the influence of land-derived
material and autochthonous phytoplankton in the surface plume. In both moderate and
peak discharge, the relative fraction of terrigenous OC decreased with distance
from the Pila distributary. In spite of this north-to-south decrease, concentrations of
allochthonous OC exhibited an overall increase throughout the prodelta because of the flood,
especially in the northern prodelta. In the southern prodelta, a thick layer of fresh water
characterized by relatively low SSC was observed during the peak of the flood.
In this region, autochthonous OC was the main OC source even during the peak
flood. This suggests that settling processes, coupled with significant input of fresh
water, are key factors for phytoplankton blooms during flood events in this region. |
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