Name: Ludmila Fava Zogheib
Type: MSc dissertation
Publication date: 03/03/2020

Namesort descending Role
Alex Cardoso Bastos Advisor *

Examining board:

Namesort descending Role
Alex Cardoso Bastos Advisor *
Fabian Sá Internal Examiner *

Summary: The continental shelf adjacent to the Doce River received a large amount of iron ore tailings in November 2015, with a mineralogical and sedimentary characteristic very different from that expected for the region, thus affecting the behavior of the hydrological and sedimentary regime. Therefore, the objective of this research is to investigate the effect of the contribution of this tailings material on the granulometry of the sedimentary deposit on the internal platform adjacent to the mouth of the Rio Doce and on the dynamics of dispersion of the sediment, comparing different moments before and after the dam rupture event. , both to the south and north of the river mouth. The methodology is developed from a database of superficial bottom sediment samples collected from 2013 to 2017, investigating, through granulometric analysis and meteoceanographic forces, their temporal and spatial variation, focusing on fine sediments. For this, the percentages, D50, maximum and minimum levels of fine sediment granulometries and box-plot graphs are used to understand the temporal variability. May and October 2013 have the D50 both to the north and south of the mouth in fine silt granulometry, already in July 2013 and January 2014 the D50 is represented by medium silt in the northern sector and fine silt in the southern sector. December 2015 is the campaign that represents the arrival of tailings at the mouth of the Rio Doce, and the D50 to the north and south is made of thick clay and very fine silt respectively. February 2016 has the northern sector represented by the D50 in granulometry fine silt and the south with D50 calculated very fine silt, December 2016 medium silt and fine silt in due order and April 2017 with the D50 of both sectors being very fine silt. The graphs of temporal variation for mud content, despite showing great variation between campaigns, do not show a trend or pattern, WHEREas the graphs of clay content and D50 clearly show that the arrival of the tailings, increasing the amount of clay and decreasing the D50 of the months studied. The ore input in the coastal and marine region changed the size of the seabed particles and, consequently, their sedimentary dynamics, since the resuspension and transport behavior is directly linked to the particle size. The importance of further detailing the physical forces is also highlighted, as these are also directly related to the dynamics of the seabed. The change in the size, composition and behavior of the particles is evident and leads to a series of changes in the environment, with longer residence in the water column, greater resuspension potential and availability to the environment, directly affecting the habitats there.

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