Franchi, F.; Comte, J.C.

Sediment records of the 2016-2017 flood from Notwane dam, Upper Limpopo basin, Botswana

The data set contains grain size distributions, organic matter (OM) contents and trace metals distribution metal distribution (Fe, Zn, Cu, Cr and Pb) of seven (7) shallow cores of sediments from the Notwane Dam (southern Botswana). The cores have been collected with a push corer using PVC pipes of 5 cm diameter by a team from BIUST led by Dr. Franchi between November 2017 and February 2018. The data were collected as part of the PULA project, which aimed at understanding the immediate effect of heavy rainfall and floods on water resources in arid Botswana and their transitional hydrologic readjustment towards the dry period, and the role of these events in supporting either or both resources replenishment and contamination. Grain size profiles of the cores have been obtained by analyzing wet sediments with a laser diffraction particle size analyzer. The OM content of the sediments was obtained by measuring the loss on ignition (LOI) of bulk sediments after calcination in a muffle furnace. The sediments have been analyzed for trace metal distribution using a Microwave Plasma-Atomic Emission Spectrometer (MP-AES). The grain size distribution has allowed to pinpoint the presence of flood couplets, characterized by coarse lags followed by fine grained materials. The trace metal distribution profiles have been compared with the flood couplets to assess the entity of metal mobilization during floods and subsequent droughts.

Publication date: 2019-11-18

Get the data

This dataset is available under the terms of the Open Government Licence

Format of the dataset : Comma-separated values (CSV)

You must cite: Franchi, F.; Comte, J.C. (2019). Sediment records of the 2016-2017 flood from Notwane dam, Upper Limpopo basin, Botswana. NERC Environmental Information Data Centre. https://doi.org/10.5285/022b3fff-55d7-46f5-b11f-2f7366e508b0

 

© Natural Environment Research Council

Where/When

Study area
Temporal extent
2017-11-22    to    2018-02-19

Provenance & quality

Seven cores of sediments were collected at scattered locations in the Notwane dam over 2 days (22/11/2017 and 19/02/2018) for further sedimentological and geochemical analyses. Core collection was realised with 50 mm diameter PVC pipes though use of a push corer equipped with extension rods from shore or from a small boat. They were subsequently stored the same day at 4 ˚C in a refrigerator at the Botswana International University of Science and Technology (BIUST) to allow for water retention. Before analysis, core were split in half, photographed and sub-sampled at selected intervals for lab analysis. Grain size distribution for each interval was obtained through dispersing a few grams of sediment into distilled water which was analysed with a Malvern Mastersizer 3000 laser diffraction particle size analyser at BIUST. The organic matter (OM) content was measured at BIUST through measuring the loss on ignition (LOI) of bulk sediments after calcination in a muffle furnace. The porcelain crucibles were pre-heated in a muffle furnace for 1 hour at 375°C and after cooling transferred into a desiccator for further cooling and weighed. Samples were dried at 105°C for 24 hours and weighed. The dried samples were then heated for 16h at 550°C. 95 samples of sediments from selected intervals of the cores were further analysed for trace metal distribution (Fe, Zn, Cu, Cr and Pb) using an Agilent 4200 Microwave Plasma-Atomic Emission Spectrometer (MP-AES) at BIUST. About 1 g of sample was treated with 10-15 ml of 65% nitric acid at 60°C for a period of 4 hours. The samples were then filtered at <0.45 µm and brought to 50 ml adding Milli-Q distilled water. Average standard deviations were as follows: Fe %RSD = 1.81; Zn %RSD = 4.02; Cu %RSD = 1.43; Cr %RSD = 0.82; Pb %RSD = 1.72. Detection limits for the metals reported here (as weight of dry sediment) were as follows: Cr = 0.8 µg kg-1, Fe = 1.7 µg kg-1; Cu = 0.5 µg kg-1; Zn = 28 µg kg-1; Pb = 2.5 µg kg-1

Correspondence/contact details

Dr Jean-Christophe Comte
University of Aberdeen
Aberdeen
UK
 jc.comte@abdn.ac.uk

Authors

Franchi, F.
Botswana International University of Science and Technology
Comte, J.C.
University of Aberdeen

Other contacts

Custodian
Environmental Information Data Centre
 eidc@ceh.ac.uk
Publisher
NERC Environmental Information Data Centre
 eidc@ceh.ac.uk

Additional metadata

Topic categories
Environment , Inland Waters , Geoscientific Information
Keywords
Botswana Chromium,  Copper,  grain size,  Iron,  Lead,  Notwane Dam,  organic matter,  Sediment,  trace metals,  Zinc
Spatial representation type
Spatial reference system
WGS 84
Last updated
19 November 2019 15:26