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| Titel |
Interpreting stream sediment fingerprints against primary and secondary source signatures in agricultural catchments |
| VerfasserIn |
Will H. Blake, Steve Haley, Hugh G. Smith, Alex Taylor, Rupert Goddard, Sean Lewin, David Fraser |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250081686
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| Zusammenfassung |
| Many sediment fingerprinting studies adopt a black box approach to source apportionment
whereby the properties of downstream sediment are compared quantitatively to the
geochemical fingerprints of potential catchment sources without consideration of
potential signature development or modification during transit. Working within a
source-pathway-receptor framework, this study aimed to undertake sediment source
apportionment within 6 subcatchments of an agricultural river basin with specific attention to
the potential role of contaminants (vehicle emissions and mine waste) in development of
stream sediment signatures. Fallout radionuclide (FRN) and geochemical fingerprinting
methods were adopted independently to establish source signatures for primary sediment
sources of surface and subsurface soil materials under various land uses plus reworked mine
and ‘secondary’ soil material deposited, in transit, along road networks. FRN data
demonstrated expected variability between surface soil (137Cs = 14 ± 3 Bq kg-1; 210Pbxs =
40 ± 7 Bq kg-1) and channel bank materials (137Cs = 3 ± 1 Bq kg-1; 210Pbxs =
24 ± 5 Bq kg-1) but road transported soil material was considerably elevated in
210Pbxs (up to 673 ± 51 Bq kg-1) due to sediment interaction with pluvial surface
water within the road network. Geochemical discrimination between surface and
subsurface soil materials was dominated by alkaline earth and alkali metals e.g.
Ba, Rb, Ca, K, Mg which are sensitive to weathering processes in soil. Magnetic
susceptibility and heavy metals were important discriminators of road transported material
which demonstrated transformation of the signatures of material transported via the
road network. Numerical unmixing of stream sediment indicated that alongside
channel bank erosion, road transported material was an important component in
some systems in accord with FRN evidence. While mining spoil also ranked as a
significant source in an affected catchment, perhaps related to legacy sediment, the
potential role of dissolved metal leaching and subsequent sediment-water interaction
within the channel on signature modification remained unclear. Consideration of
sediment signature modification en route from primary source to stream elucidated
important information regarding sediment transfer pathways and dynamics relevant
to sediment management decisions. Further work on sediment-water interactions
and potential for signature transformation in the channel environment is required. |
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