26 documents found, page 1 of 3
Mercury speciation changes in waters of the sepetiba Bay, SE Brazil during tida...
Paraquetti, Heloísa Helena M.; Lacerda, Luiz Drude de; Almeida, Marcelo D.; Marins, Rozane Valente; Mounier, StephaneThis 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 en...
Geoquímica de fósforo como indicadora da qualidade ambiental e dos processos es...
Marins, Rozane Valente; Paula Filho, Francisco José de; Rocha, Carlos Artur Sobreirahosphorus geochemistry as a proxy of environmental estuarine processes at the Jaguaribe River, Northeastern Brazil. Sedimentation of different phosphorus geochemical fractions can characterize the natural or anthropogenic processes dominant in the watershed. Selective chemical extraction of different phosphorus geochemical forms in estuarine sediments showed the predominance of inorganic over organic forms sugg...
Distribuição de mercúrio total como indicador de poluição urbana e industrial n...
Marins, Rozane Valente; Paula Filho, Francisco José de; Maia, Saulo Robério Rodrigues; Lacerda, Luiz Drude de; Marques, Wanessa Sousahe monitoring of the pollution status of the Brazilian coast is hampered by the lack of a consistent environmental indicator. We propose Hg as an environmental proxy to anthropogenic pollution of coastal regions due to its absence in the Brazilian geology, its ubiquity in anthropogenic effluents, and its toxicity. Available data suggest Hg "backgrounds" in coastal sediments of 1-10 ng g-1, in the East and 15-30...
Alternativa analítica para especiação físico-química de mercúrio em águas coste...
Marins, Rozane Valente; Paraquetti, Heloísa Helena M.; Ayres, Gisele A.The determination of the physical-chemical mercury speciation in tropical coastal waters using the derivatization technique with CVAFS detection was optimized. This methodology is able to separate the elementary, reactive, organic and total mercury phases with low operational costs. The importance of bromide chloride solution, the diluted aqua regia, used as the oxidative solution, and different compositions of...
Background values for evaluation of heavy metal contamination in sediments in t...
Paula Filho, Francisco José de; Marins, Rozane Valente; Lacerda, Luiz Drude de; Peres, Tiago FariasThis study establishes regional background levels and upper thresholds (geochemical baseline) for Zn, Cu, Pb, Cr, Mn, and Fe from surface samples and profiles taken in 16 sedimentary environments of the Parnaíba River Delta estuary, NE–Brazil. Three approaches were applied to evaluate metal contamination: normalization to Fe, statistical analysis and sediment quality guidelines or environmental assessment crite...
Natural and anthropogenic emissions of N and P to the Parnaíba River Delta in N...
Paula Filho, Francisco José de; Marins, Rozane Valente; Lacerda, Luiz Drude deThe Parnaiba River Delta is the largest open sea delta in the Americas, having a unique ecological importance for the conservation of wildlife and fisheries resources. However, little is known about the biogeochemistry of this ecosystem. This study estimates N and P emissions to the delta using emissions factors, calibrated with field samples and N and P concentrations in different compartments of the delta. Th...
The geostatistics of the metal concentrations in sediments from the eastern Bra...
Aguiar, Jose Edvar; Lacerda, Luiz Drude de; Miguens, Flavio Costa; Marins, Rozane ValenteGeostatistical techniques were used to evaluate the differences in the geochemistry of metals in the marine sediments along the Eastern Brazilian continental margin along the states of Ceará and Rio Grande do Norte (Northeastern sector) and Espírito Santo (Southeastern sector). The concentrations of Al, Fe, Mn, Ba, Cd, Cu, Cr, Ni, Pb, V, Hg, and Zn were obtained from acid digestion and quantified using flame at...
Pluriannual Watershed Discharges of Hg into a Tropical Semi-Arid Estuary of the...
Lacerda, Luiz Drude de; Dias, Francisco J. S.; Marins, Rozane Valente; Soares, Talita M.; Godoy, José Marcos O.; Godoy, Maria Luiza D. P.Mercury fluxes were measured during the dry and rainy seasons (2005 to 2009) at the Jaguaribe River estuary, which discharges into the Equatorial Atlantic Ocean in NE Brazil. During rainy periods, the water masses exhibited a short residence time within the estuary (0.8 days). During dry periods, seawater choked the fluvial discharge, resulting in longer residence times (3.1 days). Dissolved (< 0.7 µm) and part...
A new protocol to detect light elements in estuarine sediments by X-ray microan...
Miguens, Flavio Costa; Oliveira, Martha Lima de; Marins, Rozane Valente; Lacerda, Luiz Drude deThe analytical scanning electron microscope (SEM) has been used to determine the presence and distribution of atomic elements in mineralogy. However, the detection of light elements such as carbon is difficult to obtain with standard energy-dispersive X-ray spectrometry (EDS) and usual proceedings for SEM. This study proposes a new protocol to detect calcium carbonate by SEM/EDS using sediments from the Jaguari...
Geoquímica de sedimentos e o monitoramento de metais na Plataforma Continental ...
Lacerda, Luiz Drude de; Marins, Rozane ValenteThis study discusses the interactions between alloctonous continental sources andautochthonous geochemical processes occurring at the continental shelf in controlling heavy metalsconcentrations in sediments. The magnitude of the continental sources results in variations in heavymetal concentrations, which are large enough to make monitoring of local sources (offshore oil and gasexploration) very difficult. Ther...