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| Titel |
Combined use of fallout radionuclides and stable isotopes for investigating soil erosion processes in a Moroccan watershed |
| VerfasserIn |
Moncef Benmansour, Lionel Mabit, Anis Zouagui, Nouredinne Amenzou, Mohamed Sabir, Asmae Nouira, Christian Brandt, Frank Rasche, Mustapha Naimi, Mohamed Chikhaoui, Hamid Marah, Azzouz Benkdad, Fouad Taous |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250114445
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| Publikation (Nr.) |
 EGU/EGU2015-14793.pdf |
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| Zusammenfassung |
| On-site and off-site impacts associated with land degradation by soil erosion are a major concern in Morocco. This study aimed to use fallout radionuclides (FRNs): Caesium-137 ($^{137}$Cs), excess Lead-210 ($^{210}$Pb$_{ex}$) and Beryllium-7 ($^{7}$Be) in combination with carbon and nitrogen stable isotopes (i.e.\ Carbon-13 ($^{13}$C) and Nitrogen-15 ($^{15}$N)) in estimating soil loss in the "My Bouchta" watershed and the origin of sediment deposits in a downstream water reservoir (i.e.\ "Talembout"). Using $^{137}$Cs, the net soil erosion rate, for the "My Bouchta" watershed over a period of 50 years, was estimated at 23 t/ha/yr with a main sediment contribution (> 90{\%}) from the agricultural fields, the forest and shrub fields contributing to less than 10{\%} of the overall sediment production. \newline
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This result indicates clearly the role and the effectiveness of the forest plantations and vegetation cover to protect soil resource against erosion processes. The use of the $^{210}$Pb$^_{ex}$ technique in three different fields further highlighted that soil erosion rates over a period of 100 years were lower than those obtained by $^{137}$Cs reflecting the increase of soil loss during the last decades. Tests of fallout $^{7}$Be associated with short rainfall events in four fields confirmed the results obtained with $^{137}$Cs, that areas under natural vegetation were protected against erosion. \newline
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Sedimentation rates were assessed for the "Talembout" water reservoir and the mean values obtained for two sediment cores using $^{210}$Pb$_{ex}$ and the Constant Rate of Supply (CRS) model were about 0.51-0.58 g/cm$^2$/yr. The obtained results showed also a significant yearly increase of the sedimentation rate.\newline
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The results derived from the stable isotopes depth profiles indicated similar behavior for forest and shrub fields. Furthermore, strong correlation between $\delta$$^{13}$C and total C was observed for this type of land use while for the agricultural fields, the correlation was not significant. In addition, the sediment profile of N-15 indicated an increased use of synthetic fertilizers during the last 15 years.\newline
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In addition, the compound-specific stable isotope (CSSI) techniques have been tested in the study area using C-13 signatures in fatty acids extracted from soil sources and sediment materials. The preliminary results highlight that more than 80{\%} of the sediment deposits are originating from agricultural areas. Additional measurements are needed for reinforcing the final interpretation. \newline |
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