At 14:00 (France) (09:00 in Brazil)
By videoconference at the University of Toulon - La Garde Campus - V 217
& in person at the Universidade Federal de Fortaleza - Bloco 901 do Campus do Pici - Sala De Videoconferência Do Instituto UFC Virtual (09:00)
On the following subject: Geochemistry of trace metals and organic matter in equatorial estuaries in north-eastern Brazil
before a jury made up of
Ms Mélanie DAVRANCHE, University Professor, University of Rennes 1 (France), Rapporteur
Mr Carlos Eduardo de REZENDE, University Professor, Universidade Estadual do Norte Fluminense Darcy Ribeiro (Brazil), Rapporteur
Mr Luiz Drude LACERDA, University Professor, Universidate Federal do Ceara - UFC Labomar (Brazil), Examiner
Ms Florence VOUVE, Senior Lecturer, University of Perpignan (France), Examiner
Ms Rozane Valente MARINS, University Professor, Universidate Federal do Ceara - UFC Labomar (Brazil), Thesis co-supervisor
Mr Stéphane MOUNIER, Senior Lecturer (HDR), University of Toulon (France), Thesis co-supervisor
Abstract
The present work hypothesizes that trace metals from natural and non-natural sources may be controlled by the dissolved organic matter (DOM) of the mangrove forest, which acts as a geochemical transporter that regulates the distribution, mobility and possible toxicity to biota under geochemical effect. and hydrodynamic conditions of the tropical estuary of the Parnaíba River Delta (PRD). A sampling campaign was carried out in December 2019 to collect groundwater in order to obtain the particulate, dissolved and colloidal fractions. The environmental quality index results for trace metals identified moderate to highly contaminated Zn enrichment in the particulate fraction. Trace metals in the particulate fraction showed an increase in desorption from the dissolved fraction with increasing salinity, as observed mainly for Ba and Zn. This behaviour was evident from the distribution coefficient, which indicated potential mobility for Ba, Zn and Cu. The DOM showed a composition of humic substances of terrestrial (peaks A+C) and marine (peak M) origin. The complexation capacity showed a strong interaction of DOM with Cu at the Mangrove Channel stations, suggesting a lower availability of the metal in the water column. Therefore, the present study characterised the importance of mangrove DOM in controlling trace metal partitioning in the tropical estuarine system, as this DRP case study.