Sediments grain size and geo-chemical interpretation of three successive cutoff meanders of the Danube Delta,Romania |
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| Institution: | 1. Área de Ciencias de la Tierra, Facultad de Ingeniería, Universidad Autónoma de San Luís de Potosí, Av. Dr. Manuel Nava No. 8, Zona Universitaria, San Luis Potosí, C.P., 78290, Mexico;2. Department of Energy Resources, University of Stavanger, 4036 Stavanger, Norway;3. Instituto de Geología, Universidad Autónoma de San Luis Potosí, Manuel Nava #5Zona Universitaria, San Luis Potosí, S.L.P., Mexico;4. Unidad Académica de Ciencias de la Tierra, Universidad Autónoma de Guerrero, Ex–Hacienda de San Juan Bautista, S/N, Taxco el Viejo, Guerrero, Mexico;5. Grupo de Geología Exógena y del Sedimentario, Valle de la Hiedra 113B, Fracc. Valle de Santiago, Soledad de Graciano Sánchez, San Luis Potosí, C.P. 78433, Mexico;1. MNR Key Laboratory of Saline Lake Resources and Environments, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China;2. Trent School of the Environment, Trent University, 1600 West Bank Drive Peterborough, Ontario K9L 0G2, Canada;1. State University of Campinas, Brazil;2. University of Brasília, Brazil;3. Natural History Museum—Leibniz Institute for Evolution and Biodiversity Research, Berlin, Germany;4. Federal University of Bahia, Brazil;5. University of São Paulo, Brazil;1. Qingdao Institute of Marine Geology, China Geological Survey, Minisitry of Natural Resources, Qingdao 266071, China;2. Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, China;3. State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China |
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| Abstract: | The paper presents the results of granulometric and geochemical analyses of the superficial bed sediments of the St. George branch, one of three Danube River distributaries. Three cutoff meander reaches (the Mahmudia, Dunav?? de Sus (Upper Dunav??) and Dunav?? de Jos (Lower Dunav??) meanders, noted here as M, DS and DJ meanders) was selected as an example to analyse the impact of the meanders rectification on the grain size and sediment quality. The cut-offs of the meanders by navigational canals since 1984–1988 caused dramatic changes in the distribution of velocities, discharge and sediment fluxes (Popa, 1997; Panin, 2003, Tiron and Provansal, 2010, Tiron Dutu et al., 2014). The correction of the studied meanders induced different hydro-sedimentary impacts: strong modifications by acceleration of the fluxes through the artificial canals combined with dramatically enhanced deposition in the former meander in two cases (Mahmudia and Dunav?? de Jos meanders) and slight modifications in Dunav?? de Sus meander, where the natural channel still keeps almost its initial conveyance capacity. Sediment samples were acquired throughout several cross-sections of both natural and artificial canals of the three rectified meanders, in order to investigate the bed sediment characteristics. Grain size parameters (such as Median, Standard deviation, Skewness) show the predominance of fine fraction (silt and medium/ fine sand), relatively good sorted depending of the sample location (on the natural course of the branch, on the rectification canals or the former meanders. The statistical analysis of chemical data evidenced a high compositional variability, with concentration variation coefficients ranging between 27.4% – Sr and 178.3% – TOC (Total Organic Carbon). Generally, the highest concentrations of terrigenic compounds appear in the samples collected from the rectified natural canals. These results are validated by comparison with aDcp measurements made on each investigated profile. |
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| Keywords: | Former meander Sediment pollutants Grain size parameters Human impact aDcp |
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