Mercury speciation changes in waters of the sepetiba Bay, SE Brazil during tidal events and different seasons

Abstract

Este estudo descreve as mudanças na especiação de Hg nas águas da Baía de Sepetiba, SE, Brasil, ao longo do gradiente estuarino, durante eventos de maré em diferentes estações. A avaliação química das águas da baía indicou uma exportação de material particulado em suspensão (MPS) pobre em carbono orgânico para a plataforma continental adjacente, principalmente durante a estação chuvosa e uma importação de MPS oceânico rico em carbono orgânico, provavelmente de origem fitoplanctônica, durante a estação seca. A especiação química do Hg demonstrou que a produção de Hg 0 na Baía de Sepetiba pode ser controlada pela produtividade primária, e que a baía atua como produtora e exportadora de formas orgânicas de Hg para as áreas adjacentes, já que as maiores concentrações de Hg não-reativo foram encontradas durante a maré vazante. Não foram observadas correlações significantes entre as concentrações de Hg não-reativo e carbono orgânico dissolvido ou particulado. Em geral, as frações de Hg particulado, Hg não-reativo e Hg reativo representam 55%, 35% e 9,5% do conteúdo total de Hg nas águas da Baía de Sepetiba, respectivamente.This work describes changes in Hg speciation in water along the transport from Sepetiba Bay, SE Brazil, to the adjacent continental platform during tide events and in different seasons. The chemical evaluation of Sepetiba Bay waters showed that the bay exports suspended particulate material (SPM) impoverish in organic carbon to adjacent continental platform areas, mainly during the wet season and imports SPM enriched in organic carbon from the ocean, probably of phytoplanktonic origin, during the dry season. The chemical speciation of Hg during the study period showed that Hg 0 production can be controlled by primary productivity and that the bay acts as a producer and exporter of organic species of Hg to adjacent areas, since the highest non-reactive Hg concentrations were observed during the ebb tide. No significant correlations were found between non-reactive Hg and dissolved or particulate organic matter concentrations. In general the particulate Hg, non-reactive Hg and reactive Hg fractions represents 55%, 35.5% and 9.5% of the total Hg content in Sepetiba Bay waters, respectively.Keywords: mercury speciation, coastal area, organic carbon, Sepetiba Bay IntroductionCoastal environments are complex and very dynamic systems showing a strong salinity gradient, high variation of suspended matter concentration and complex hydrodynamic processes. They act as links between the terrestrial and oceanic environments, present a large capacity to accumulate materials of continental and marine origin and are strongly affected by tidal events and continental hydrology. These environments are also characterized by land-sea gradients of physicochemical processes such as oxidation/reduction, sorption/desorption and precipitation/dissolution, which result in gradients of dissolved chemical species concentration, ionic force, pH and redox potential, which are responsible for the precipitation of the major part of ...

Mercury methylation in sediments of a Brazilian mangrove under different vegetation covers and salinities

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Mercury in tropical and subtropical coastal environments

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