Skills and Expertise
Research Items (13)
In this work, a multi-elemental approach combining Cu and Zn stable isotopes is used to assess the metal contamination evolution in the Loire estuary bulk sediments. Elemental geochemical data indicate an increase of metal concentrations from the beginning of the industrial period peaking in the 1990s, followed by an at-tenuation of metal contamination inputs to the estuary. Zinc isotope compositions suggest a binary mixing process between Zn derived from terrigenous material and multi-urban anthropogenic sources. Copper isotope systematics indicate a single natural dominant source represented by weathered silicate particles from soils and rocks. This work demonstrates the applicability of Zn isotopes to identify anthropogenic Zn sources in coastal systems, even under a low to moderate degree of contamination. Further studies are required to constrain Cu sources and to elucidate possible effects of grain-size and mineralogy in the Cu isotope composition of sediment in the Loire estuary.
- May 2018
Recent work has shown that variations in zinc (Zn) isotope ratios enable us to identify contamination sources in the terrestrial environment and uptake processes in higher plants. Here in this study, we demonstrate that this also holds true for mangrove forests, which play an important role in the biogeochemical cycling of metals in tropical coastal ecosystems and that are seriously threatened by anthropogenic pollution. To this end, we determined zinc concentration and isotope composition (expressed using the δ⁶⁶Zn notation relative to the JMC 3-0749-L standard) in sediments and tree leaves collected from a mangrove close to Rio de Janeiro in Brazil. The δ⁶⁶ZnJMC values of sediments vary between +0.36 and + 0.84‰ and fall on a mixing line between detrital terrestrial sources (characterized with δ⁶⁶ZnJMC = +0.28 ± 0.12‰, 2σ) and metallurgical ore sources (δ⁶⁶ZnJMC = +0.86‰ ±0.15‰, 2σ). Leaves of Laguncularia racemose, in contrast, showed δ⁶⁶ZnJMC values ranging between +0.08 and + 0.23‰, suggesting that processes including uptake, translocation and bioavailability in the rhizosphere control the isotope composition of zinc in the mangrove plant.
The source assessments of metal contaminants are critical for a consistent management of coastal zones. In this work, lead (Pb) concentration and isotopic composition were determined in sediments from Angra dos Reis coast (Brazil) to evaluate the potential influence of contamination sources on Pb distribution. Estimated Pb enrichment factor superior to 1.64 suggested natural source predominance. Diagrams of 206Pb/207Pb ratio plotted against 208Pb/206Pb and 1/Pb ratios indicated a binary source mixing that was explained by marine and terrigenous influences. Only some specific sites fall close to anthropogenic Pb isotopes signatures (e.g., from urban effluents and gasoline). The lower Pb concentrations were associated with a marine carbonate dilution effect, as indicated by a negative relationship between Pb and Ca. Past dredging activities contributed to explain a diffuse occurrence of anthropogenic Pb isotopic signature. The overall results reveal the beginning of a transition from pristine to slightly-polluted condition. ResumoA avaliação das fontes dos contaminantes metálicos é fundamental para um bom gerenciamento das zonas costeiras. Neste trabalho, as concentrações e composições isotópicas do chumbo (Pb) foram determinadas em sedimentos do litoral de Angra dos Reis (Brasil) para avaliar a potencial influência das fontes de contaminação na distribuição de Pb. Fatores de enriquecimento de Pb de até 1,64 sugeriram predominância de fontes naturais. Diagramas da razão 206Pb/207Pb plotados contra as razões 208Pb/206Pb e 1/Pb indicaram uma mistura binária de fontes, que foi explicada por influências marinhas e terrígenas. Apenas alguns locais específicos possuem assinaturas isotópicas similares às antropogênicas (por exemplo, de efluentes urbanos e gasolina). As concentrações mais baixas de Pb foram associadas a um efeito de diluição pelo carbonato marinho, como indicado por uma relação negativa entre Pb e Ca. Atividades de dragagem no passado contribuíram para explicar uma ocorrência difusa da assinatura isotópica de Pb antropogênico. Os resultados, em geral, revelam o início de uma transição da condição natural para levemente poluída.
- Feb 2018
Air pollution imposes serious health risks to urban populations and currently is the major environmental threat to the public health worldwide. In this context, discrimination and tracing of pollutants in atmosphere is a great challenge nowadays. This study reports the simultaneous use of Pb, Cu and Zn Multi-Isotopic Systems (MIS) to identify and discriminate pollutant sources of atmospheric particulate matter (PM) collected in day and nighttime temporal resolution in São Paulo city, Brazil. The isotopic fingerprints of road dust and tires (δ66Zn = 0.00 to +0.20‰ and 206Pb/207Pb = 1.16 to 1.19) were differentiated from vehicular traffic (δ66Zn = −0.60 to +0.00‰ and 206Pb/207Pb < 1.19) and PM from an industrial area (δ66Zn < −0.60‰ and 206Pb/207Pb > 1.20). Isotopic signatures of cement (δ66Zn = 0.00 to +0.30‰ and δ65CuNIST = +0.30 to +0.61‰) were distinguished from road dust (δ65Cu = +0.08 to +0.25‰) and vehicular traffic (δ65CuNIST = +0.46 to +0.59‰). The isotopic compositions found in PM for Pb (206Pb/207Pb = 1.156 to 1.312, n = 113), Zn (δ66Zn = +0.43 to −1.36‰, n = 62) and Cu (δ65Cu = +0.12 to 0.66‰, n = 7) are comparable with those measured on the main pollutant sources found in urban areas. Zinc and lead isotopic compositions of PM from Sao Paulo showed diurnal variations indicating the industrial contributions carried by cold fronts and road dust suspension associated to high wind speeds and traffic pattern. A ternary mixing model based on Pb and Zn isotopic fingerprints of the main pollutant sources were developed to account vehicular traffic (70%), industrial area (10%) and another uncharacterized source (20%) contributions, possibly associated with industrial and biomass burning emissions. Our findings validate the use of Pb, Cu and Zn MIS to source apportionment studies in the atmosphere with multiple and complex pollutant sources. https://www.sciencedirect.com/science/article/pii/S004896971830233X
- Jul 2017
The application of zinc (Zn) isotopes in bivalve tissues to identify zinc sources in estuaries was critically assessed. We determined the zinc isotope composition of mollusks (Crassostrea brasiliana and Perna perna) and suspended particulate matter (SPM) in a tropical estuary (Sepetiba Bay, Brazil) historically impacted by metallurgical activities. The zinc isotope systematics of the SPM was in line with mixing of zinc derived from fluvial material and from metallurgical activities. In contrast, source mixing alone cannot account for the isotope ratios observed in the bivalves, which are significantly lighter in the contaminated metallurgical zone (δ⁶⁶ZnJMC = +0.49 ± 0.06‰, 2σ, n = 3) compared to sampling locations outside (δ⁶⁶ZnJMC = +0.83 ± 0.10‰, 2σ, n = 22). This observation suggests that additional factors such as speciation, bioavailability and bioaccumulation pathways (via solution or particulate matter) influence the zinc isotope composition of bivalves.
- Dec 2016
The use of zinc isotopes to trace anthropogenic sources in coastal areas has been tested in this study. We determined the stable isotopic composition of zinc in sediment cores, suspended particulate matter (SPM) and rocks collected at the Sepetiba Bay (southeastern Brazil), an estuarine lagoon heavily impacted by metallurgic activities. These isotopic signatures were compared with those from willemite ore, which represent the main mineral refined by the major industrial source of zinc. The aim was to test if this tracer system enables to identify sources and sinks of anthropogenic zinc and to reconstruct the temporal and spatial evolution of zinc contamination. The zinc isotopic compositions (expressed using the δ⁶⁶Zn notation relative to the JMC 3-0749-L solution) showed significant variations in the sediment cores, the SPM, and willemite ore minerals, ranging between − 0.01 and + 1.15‰. Spatial and temporal analysis of sediments samples fit well in a model of mixing involving three main end-members: i) Terrestrial background (δ⁶⁶ZnJMC = + 0.28 ± 0.12‰, 2σ); ii) marine detrital material (δ⁶⁶ZnJMC = + 0.45 ± 0.03‰, 2σ); and iii) a major anthropogenic source associated with electroplating wastes released into the bay (δ⁶⁶ZnJMC = + 0.86 ± 0.15‰, 2σ). Sediment cores collected in the mud flats showed high correlation between δ⁶⁶Zn and zinc enrichment factors, suggesting good preservation of the isotopic records of natural and anthropogenic sources. The sediment core sampled from a mangrove wetland located in a zone impacted by the metallurgy presented levels of zinc up to 4% (sediment dry weight) and preserved the isotopic signatures of electroplating wastes, despite evidences that post depositional processes slightly changed the isotopic signatures in some layers from this core toward heavier δ⁶⁶ZnJMC values (above + 1.0‰). A two component mixing model suggests contributions of this major anthropogenic Zn source up to nearly 80% during periods of electroplating activities. Our work suggests that Zn isotope compositions of sediments are reliable tracers of anthropogenic sources and, therefore, can be useful to improve environmental monitoring efforts in coastal systems.
- May 2016
Lake Paranoá is a human-made water reservoir created in 1959 together with the new capital of Brazil (Brasilia). With the demands of urban development, population growth, and land use changes, the lake presented severe deterioration of water quality due to the disposal of wastewater with a high concentration of nutrients. To better elucidate the natural and anthropogenic sources controlling the water quality from Lake Paranoá, this study aimed to (1) investigate the main geochemical processes controlling water quality of the lake and its tributaries; (2) evaluate Lake Paranoá’s trophic state; and (3) determine the occurrence and fate of organic micropollutants in Lake Paranoá waters and WWTPs effluents. The waters from Lake Paranoá tributaries are naturally acidic due to the nature of the extremely weathered ferralsols and the crustal material composition. The main processes linked with anthropogenic activities that affect the water quality from the tributaries are the input of untreated domestic wastewater and the dissolution of carbonate minerals arising from construction material residues. Generally, the waters of Lake Paranoá presented low nutrient and chlorophyll-a concentrations, indicating a low trophic state (oligo-mesotrophic). A significant increase in the trophic state (super-eutrophic) was observed at specific regions of the lake that have high nutrient input from tributaries, caused by the continuous disposal of untreated domestic sewage. In Lake Paranoá waters, the organic micropollutants that were identified and quantified (caffeine, bezafibrate, bisphenol A, diethyl phthalate, and nonylphenol) presented concentrations consistent with previous studies and within the threshold of toxicity, except bisphenol A.
Precise and accurate δ66/64Zn data for environmental reference materials (RMs) including rocks, sediments, soils and plants are presented in order to improve the metrological traceability and analytical control of Zn isotope ratio determinations in future environmental studies. Previously developed ion exchange chromatography protocols were adjusted to enable faster sample throughput and instrumental mass bias processes were investigated. The improved chromatographic protocol yielded precise and quantitative recoveries (99 ± 7%, σ, n = 16), while the mass bias correction using Cu as external dopant provided precisions better than 0.02‰, 2σ, n = 7. Investigations into spectral and non-spectral interferences identified significant formation of Cr and Ti oxides and hydroxide ionic species. Analysis of six RMs (BHVO-2 basalt (USGS), BCR-2 basalt (USGS), AGV-2 andesite (USGS), 2709 San Joaquin soil (NIST), 1646a estuarine sediment (NIST) and 1573a tomato leaves (NIST)) showed good reproducibility (< 0.01‰, 2σ, 5 ≤ n ≥ 1).
This work reports a geochemical study of sediments from the upper Paracatu River Basin. The objective is to define the influences of Au, Zn, and Pb mineral deposits and mining activities on the sediment metal sources, distribution, and accretion. The samples were analyzed using ICP/OES, AAS, and XRD techniques and were treated with principal components analysis and the geo-accumulation index. The main geochemical processes that control the sediment composition are pyrite oxidation, muscovite weathering, carbonate dissolution, and the erosion of oxisols enriched with Zn and Pb. The upper Rico Stream has high Al, Fe, Cu, Cr, Co, and Mn concentrations due erosion of oxisols and pyrite oxidation and muscovite alteration present in the parental rock. The artisanal alluvial gold mining increased the primary rock-minerals’ weathering and Hg sediment concentration. The lower Escuro River and Santa Catarina Stream are enriched with Zn and Pb due the erosion of metal-rich soils formed over galena, sphalerite, calamine, and willemite mineral deposits located upstream. Elements such as Ca, Mg, and Ba have low concentrations throughout the sampled area due the high solubility of these metals-bearing minerals. The dispersion of metals is limited by the basin geomorphology and their affinity to silt-clayey minerals and Fe and Mn oxides and hydroxides in circumneutral pH waters.
This work reports a geochemical study of three watersheds located in the upper course of the Paracatu River (one of the most important sub-basins of the upper-middle Sao Francisco River). It aimed to establish a geochemical model that can assist in identifying the sources and distribution of physico-chemical components and dissolved metals in water, assessing how the local geology and human activities influence the quality of the aquatic systems. The predominant geology of the region includes the Vazante Group, basically formed by a sequence of clay and dolomitic clay where zinc and lead mineralization occurs, and the Canastra Group (Paracatu Formation) composed of a sequence of phyllites and carbonaceous phyllites with intercalations of quartzites, where gold occurs in iron and arsenic sulfides. The samples were analysed using ICP/OES, AAS, spectrophotometric (UV/Visible) techniques and volumetric methods. The development of the geochemical model used multivariate statistical analysis including principal components, multiple regression and hierarchical clustering. The proposed model determined that Fe, Mn, SO42-, and color come primarily from sulfide oxidation; HCO3-, Ca, Mg, Zn, and Ba, from dolomitic limestone dissolution, and PO43-, NO3-, NH3 and turbidity from the input of urban sewage. Indices were created for each group of parameters representing the intensity of these processes and classifying the sampling sites according to their predominant chemical composition (water with low mineralization, high carbonate, or sulphate mineralization and pollution by urban sewage). The proposed model can be used in regional water quality monitoring, and as a reference for other locations.