Wilson Machado

Mercury, zinc, and copper accumulation in mangrove sediments surrounding a large landfill in southeast Brazil

The accumulation of Hg, Zn, and Cu was evaluated in mangrove sediments located between a large, 20-years-old landfill and waters of Guanabara Bay (southeast Brazil). The contamination history of the area provides substantial evidence that metal accumulation in the study site is influenced by past metal emissions from multiple sources (e.g. contaminated rivers and the landfill surrounding the site). At the southern part of the site, metal levels are up to 890 ng g(-1) Hg, 850 microg g(-1) Zn, and 58 microg g(-1) Cu. Enrichment factors and excess (background-deducted) concentration inventories show a high spatial variability of metal contamination and storage in the site, with differences often by a factor higher than two within a sampling station and higher than five between sampling stations. These contrasts are attributable to a coupling between spatial variability of anthropogenic metal input and metal behavior and retention within the sediments. Results indicate that during the last few decades mangrove sediments retained a substantial part of metal emissions to the site, probably reducing the metal transport to Guanabara Bay waters, and suggest the suitability of mangrove ecosystems as physical and biogeochemical barriers to metal contaminant transport.

Trace metal retention in mangrove ecosystems in Guanabara bay, SE Brazil

Along contrasting environmental conditions (e.g., degree of trace metal contamination and mangrove forest structural development), sediments of Laguncularia racemosa-dominated mangrove stands in Guanabara Bay (SE Brazil) presented a trend of trace metal accumulation in forms with low potential of remobilization and biotic uptake. Concurrently, a relatively low transfer of sediment-bound metals to L. racemosa leaves was observed, which may moderate the metal export from the forests via leaf litter transport and the metal availability to enter in food chains based on leaf consumption.

Trace metals in mangrove seedlings: role of iron plaque formation

Metal-rich mineral deposits on the roots of aquatic plants, denominated iron plaques, may moderate the uptake of essential, but potentially toxic metals by roots. We investigated the iron plaque formation on the fine, nutritive roots of mangrove seedlings growing in contrasting environments (oxidizing sand flat sediments and reducing mangrove forest sediments) in southeast Brazil. The results indicate that Avicennia schaueriana, Laguncularia racemosa, and Rhizophora mangle seedlings developed an efficient exclusion of Fe, Mn, and Zn through iron plaque formation. This process seems to be influenced substantially by species-specific responses to environmental conditions. While Fe and Zn translocation to leaves appear to be suppressed by accumulation within root tissues, this did not appear to occur for Mn, suggesting that Mn trapping in rhizosphere sediments and iron plaque formation are the main mechanisms responsible for the Mn exclusion from the organism level. In addition to factors well recognized as affecting mangrove seedling development (e.g., salinity stress and nutrient availability), the mediation of trace metal uptake by iron plaque formation possibly contribute to determine the seedling adaptability to waterlogged conditions.

Variabilidade espacial e sazonal da concentração de elementos-traço em sedimentos do sistema estuarino de Santos-Cubatão (SP)

Multi-element analyses of sediment samples from the Santos-Cubatao Estuarine System were carried out to investigate the spatial and seasonal variability of trace-element concentrations. The study area contains a rich mangrove ecosystem that is a habitat for tens of thousands of resident and migratory birds, some of them endangered globally. Enrichments of metals in fine-grained surface sediments are, in decreasing order, Hg, Mn, La, Ca, Sr, Cd, Zn, Pb, Ba, Cu, Cr, Fe, Nb, Y, Ni and Ga, relative to pre-industrial background levels. The maximum enrichment ranged from 49 (Hg) to 3.1 (Ga). Mercury concentrations were greater in the Cubatao river than in other sites, while the other elements showed greater concentrations in the Morrao river. Concentrations of Mn were significantly greater in winter and autumn than in summer and spring. However, other elements (e.g. Cd and Pb) showed the opposite, with greater concentrations in summer and spring. This study suggests that seasonal changes in physical and chemical conditions may affect the degree of sediment enrichment and therefore make the assessment of contamination difficult. Consequently, these processes need to be considered when assessing water quality and the potential contamination of biota.

Eutrophication history of Guanabara Bay (SE Brazil) recorded by phosphorus flux to sediments from a degraded mangrove area

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Elevated rates of organic carbon, nitrogen, and phosphorus accumulation in a highly impacted mangrove wetland

- see front matter 2009 Elsevier Ltd. All rights reserved.doi:10.1016/j.marpolbul.2009.08.005

Multi-elemental contamination and historic record in sediments from the Santos-Cubatão Estuarine System, Brazil

The effect of nutrient enrichment on mangrove sediment accretion and carbon accumulation rates is poorly understood. Here we quantify sediment accretion through radionuclide tracers to determine organic carbon (OC), total nitrogen (TN), and total phosphorus (TP) accumulation rates during the previous 60 years in both a nutrient-enriched and a pristine mangrove forest within the same geomorphological region of southeastern Brazil. The forest receiving high nutrient loads has accumulated OC, TN, and TP at rates that are fourfold, twofold, and eightfold respectively, higher than those from the undisturbed mangrove. Organic carbon and TN stable isotopes (δ13C and δ15N) reflect an increased presence of organic matter (OM) originating with either phytoplankton, benthic algae, or another allochthonous source within the more rapidly accumulated sediments of the impacted mangrove. This suggests that the accumulation rate of OM in eutrophic mangrove systems may be enhanced through the addition of autochthonous and allochthonous nonmangrove material.

MERCURY ACCUMULATION IN SEDIMENTS OF A MANGROVE ECOSYSTEM IN SE BRAZIL

Este trabalho registra pela primeira vez o historico da contaminacao e as fontes de 38 elementos em sedimentos do sistema estuarino de Santos-Cubatao (SE do Brasil), em uma das areas mais industrializadas da America Latina. A composicao de um testemunho de 260 cm de profundidade do estuario do rio Morrao foi determinada por ICP-MS e avaliada por meio de fatores de enriquecimento, analise de componentes principais, matrizes de correlacao e assinaturas geoquimicas. Elementos contaminantes como Cr, Mn, Ni, Zn, Ga, Ag, Cd, Sn, Sb, Pb e Bi foram associados ao Fe, derivados de atividades siderurgicas, enquanto Be, Ca, Sc, Co, Cu, Sr, Y, Zr, Nb, Hf, Ta, Th e U estiveram associados ao P, relacionados ao processo produtivo de fertilizantes. Uma sobreposicao da distribuicao do Fe sedimentar e producao local de aco indicaram que o Fe e um marcador confiavel do historico da contaminacao, permitindo a estimativa de taxas de sedimentacao para 45 anos de atividades industriais. This paper records for the first time the contamination history and identifies the sources of 38 elements in sediments from the Santos-Cubatao Estuarine System (SE Brazil), at one of the most industrialized areas in Latin America. The compositions of samples from a 260 cm long sediment core collected in the Morrao River estuary were determined by ICP-MS. Enrichment factors, principal component analysis, correlation matrixes, and the characterization of geochemical signatures permitted a consistent data evaluation. Contaminant elements such as Cr, Mn, Ni, Zn, Ga, Ag, Cd, Sn, Sb, Pb, and Bi were associated with steel plant-derived Fe concentrations, while Be, Ca, Sc, Co, Cu, Sr, Y, Zr, Nb, Hf, Ta, Th, and U were associated with fertilizer industry-derived P concentrations. An overlap of sedimentary Fe distribution and local steel plant production indicated that Fe is a reliable marker of the contamination history, allowing the estimation of sedimentation rates over a period of 45 years of industrial activities.

Relation of Reactive Sulfides with Organic Carbon, Iron, and Manganese in Anaerobic Mangrove Sediments: Implications for Sediment Suitability to Trap Trace Metals

The Hg accumulation in sedimentary environments of a mangrove ecosystem in Sepetiba Bay, SE Brazil, was investigated. These environments include sediments of a mangrove forest, the main tidal creek that drains the forest, and the bare seaward-edge mud flat adjacent to forest and tidal creek. Maximum Hg concentration peaks in sediments from the mud flat (184 ng g-1), tidal creek (98 ng g-1), and mangrove forest (60 ng g-1) correspond to enrichment factors of 6.1, 3.3, and 2.0 above the estimated average background level, respectively. Average inventories of Hg excess (background-corrected) concentrations were substantiallydifferent between environments, decreasing from mud flat sediments (5.2 mg m-2) to creek sediments (3.3 mg m-2)to mangrove forest sediments (0.9 mg m-2). Mercury concentration profiles indicated a consistently higher accumulation of Hg in surface layers of mud flat and tidal creeksediments, whereas mangrove forest sediments showed a higher Hgaccumulation in root-rich subsurface layers, in agreement with an enrichment of Fe and organic matter contents. While Hg distribution in mud flat and tidal creek sediments appears to belargely affected by contamination, its distribution in mangrove forest substrate appears to be greatly affected by root-sedimentinteractions. Mercury levels in the study site were comparable tothose observed in coastal sediments under moderate Hg contamination at local and regional scales. Results indicate thatsedimentary environments surrounding the mangrove forest retain most of the anthropogenic Hg reaching the ecosystem. Since tidal waters have been previously demonstrated as the main source of metals to the site, it is suggested that the Hg retention in mudflat sediments precede and may avoid a higher Hg accumulation inlandward environments.

Mercury accumulation in sediments along an eutrophication gradient in Guanabara Bay, southeast Brazil

Abstract The accumulation of acid-volatile sulfides and its relation with other trace metal-binding sediment constituents may be important mechanisms to determine the suitability of anaerobic sediments to trap trace metals. An investigation into the relationships among acid-volatile sulfides, total organic carbon, and reactive (hydrogen chloride–soluble) iron, manganese, and trace metals of environmental concern (cadmium, copper, nickel, lead, and zinc) was conduced in anaerobic sediments from a disturbed mangrove ecosystem in Sepetiba Bay (SE Brazil). The two main metal contaminants in the study area (cadmium and zinc) presented levels above regional backgrounds (showing enrichment factors up to 8.5 and 9.1, respectively) and a significant correlation, suggesting a contamination source similarity. Positive correlations among total organic carbon, acid-volatile sulfides, and iron and negative correlations of manganese with total organic carbon and acid-volatile sulfides occurred, probably because of (1) organic matter fuelling of acid-volatile sulfides production and depletion of manganese levels due to manganese oxide consumption by microbial respiration and (2) manganese oxide depletion in reaction with acid-volatile sulfides. The elevated acid-volatile sulfides concentrations and inventories observed, exceeding those of metals of environmental concern, indicate the sediment suitability to trap these metals as metal sulfides. While comparatively low manganese concentrations are probably unable to influence acid-volatile sulfides distribution, results evidenced that acid-volatile sulfides may affect manganese distribution negatively. To our knowledge, this negative metal–sulfur relationship was demonstrated for the first time in sediments from a tropical coastal ecosystem, which may help elucidate the behavior of manganese and manganese-associated elements in anaerobic mangrove sediments.