Wilson Machado

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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(More)
This paper reports on a study to determine the Hg content in the five most abundant aquatic macrophyte species (Elodea densa, Sagittaria montevidensis, Salvinia auriculata, Pistia stratiotes and Eichhornia crassipes) in two artificial reservoirs flooded by water diverted from the Paraíba do Sul river, SE Brazil. The potential of these species for Hg(More)
Atmospheric Hg transfer to the forest soil through litterfall was investigated in a primary rainforest at Ilha Grande (Southeast Brazil) from January to December 1997. Litter mass deposition reached 10.0 t ha (-1)y(-1), with leaves composing 50-84% of the total litter mass. Concentrations of Hg in the total fallen litter varied from 20 to 244 ng g(-1), with(More)
99, 311–314. O’Dor, R.K., Weber, M.J., 1987. Energy and nutrient flow. In: Boyle, P.R. (Ed.), Cephalopod Life Cycles, Comparative Reviews, vol. II. Academic Press, London, pp. 109–133. Pereira, P., Vale, C., Raimundo, J., Kadar, E., 2009. Metal concentrations in digestive gland and mantle of Sepia officinalis from two coastal lagoons of Portugal. Science of(More)
Dissolved silicate (DSi), NH4(+), NO3(-) and PO4(3-) susceptibility to be exchanged between sediment pore waters and overlying waters was evaluated in Jurujuba Sound (JS station) and Coroa Grande Sound (CGS station), southeastern Brazil. Sedimentary elemental (C, N and P) and isotopic (δ(13)C and δ(15)N) compositions evidenced stronger anthropogenic(More)
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(More)
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(More)
Since transition metal impurities affect the electronic and optical properties of semiconductors [1], it is important to understand the role of such unavoidable impurities on those properties. At the same time, transition metals in semiconductors can be used in other unusual situations. The energy levels related to transition metal impurities are aligned(More)
The potential association of acid-volatile sulfides (AVS) and reactive (HCl soluble) Fe with the distribution of reactive trace metals (Cu, Cd, Ni, Pb and Zn) was investigated in sediment cores collected in the Iguaçu river estuarine system (Guanabara bay, Brazil), within the river (core R) and the bay (core B) areas. Moderate to extremely high AVS(More)
The geochemical composition of sediment pore water was investigated in comparison with the composition of sediment particles and surface water in an estuary within one of the most industrialized areas in Latin America (Santos-Cubatão estuarine system, SE Brazil). Pore and surface waters presented anomalously high levels of F(-), NH4(+), Fe, Mn and P due to(More)