Effects of iron-ore mining and processing on metal bioavailability in a tropical coastal lagoon

In water systems, water quality and geochemical properties of sediments determine the speciation of trace metals, metal transport, and sediment-water exchange, influencing metal availability and its potential effects on biota. Studies from temperate climates have shown that iron-ore mining and tailing wastewaters, besides being a source of trace metals, usually show high levels of dissolved ions and particulate suspended matter, thus having the potential of indirectly changing metal bioavailability. For the first time in the tropics, we identified the effects of iron-ore mining and processing on metal bioavailability in a coastal lagoon. With an extensive sampling scheme, we investigated the potential sources of metals; the links among metal levels in water, sediments, and invertebrates; and the contrasting effects on metal speciation and bioavailability. The metals Fe, Mn, Al, Cr, Zn, Cu, Ni, Pb, Cd, Hg, and As were measured in water, sediments (surface and profiles), and invertebrates from Mãe-Bá Lagoon and in the sites directly influenced by the mining operations (tailing dams and nearby rivers). In addition, samples from two other lagoons, considered pristine, were analyzed. The study area is located in the southeast of Brazil (Iron Quadrangle Region and a coastal area of Espírito Santo State). General water characteristics included pH, dissolved organic carbon, alkalinity, and anion composition. Water metal speciation was assessed by a speciation model (Chemical Equilibria in Aquatic Systems). Grain-size distribution, organic carbon, carbonate, and acid volatile sulfide (AVS) were determined in sediments. Statistical methods included comparison of means by Mann-Whitney test, ordination and correlation analyses, and analysis of regression for geochemical normalization of metals with grain size. The dissolved metal concentrations, the total metal levels in sediments, and the normalization based on the fine sediment fraction showed that the mining operations constitute potential sources of Fe, Mn, Cr, Cu, Ni, Pb, As, and Hg to Mãe-Bá Lagoon. However, trace metal availability was reduced because of increased pH, hardness, and sulfide content (356 μmol/g) in the sites influenced by the mining. The lagoon showed similar water chemistry as in the mining sites, with metal bioavailability further decreased by the presence of dissolved organic carbon and chloride. Although AVS levels in the lagoon were low (0.48-56 μmol/g), metal bioavailability was reduced because of the presence of organic matter. Metal levels in invertebrates confirmed the predicted low metal bioavailability in Mãe-Bá Lagoon. The lagoon was considered moderately contaminated only by Hg and As. The iron-ore mining and processing studied here constitute potential sources of metal pollution into the tropical lagoon. Contrary to expectations, however, it also contributes to reducing the overall metal bioavailability in the lagoon. These findings are believed to be useful for evaluating metal exposure in a more integrated way, identifying not only the sources of pollution but also how they can affect the components involved in metal speciation and bioavailability in water systems, leading to new insights

Trophic Relationships and Habitat Preferences of Delphinids from the Southeastern Brazilian Coast Determined by Carbon and Nitrogen Stable Isotope Composition

To investigate the foraging habitats of delphinids in southeastern Brazil, we analyzed stable carbon (δ13C) and nitrogen (δ15N) isotopes in muscle samples of the following 10 delphinid species: Sotalia guianensis, Stenella frontalis, Tursiops truncatus, Steno bredanensis, Pseudorca crassidens, Delphinus sp., Lagenodelphis hosei, Stenella attenuata, Stenella longirostris and Grampus griseus. We also compared the δ13C and δ15N values among four populations of S. guianensis. Variation in carbon isotope results from coast to ocean indicated that there was a significant decrease in δ13C values from estuarine dolphins to oceanic species. S. guianensis from Guanabara Bay had the highest mean δ13C value, while oceanic species showed significantly lower δ13C values. The highest δ15N values were observed for P. crassidens and T. truncatus, suggesting that these species occupy the highest trophic position among the delphinids studied here. The oceanic species S. attenuata, G. griseus and L. hosei had the lowest δ15N values. Stable isotope analysis showed that the three populations of S. guianensis in coastal bays had different δ13C values, but similar δ15N results. Guiana dolphins from Sepetiba and Ilha Grande bays had different foraging habitat, with specimens from Ilha Grande showing more negative δ13C values. This study provides further information on the feeding ecology of delphinids occurring in southeastern Brazil, with evidence of distinctive foraging habitats and the occupation of different ecological niches by these species in the study area.Peer reviewe

Anthropogenic sources and distribution of phosphorus in sediments from the Jaguaribe River estuary, NE, Brazil

This paper estimates annual P emission to the Jaguaribe River estuary, NE Brazil, responsible for approximately 30% of the country's farmed shrimp production. Emissions increased three times between 2001 and 2006 and reached 43.9 t.year-1. These emissions make aquaculture the third main source of P for this estuary and are much smaller than emissions from agricultural sources and slightly lower than emissions from wastewater. Their relative contribution also increased from 10.5% to 20.5%. Temporal variability of P concentrations in estuarine bottom sediments also suggest an increase, but not as evident as the emissions. The spatial distribution and speciation of P (total P and inorganic P) in sampling stations located upstream and downstream from the main aquaculture area confirmed the importance of this source. Inorganic P was the dominant form present in sediments downstream and showed an increase from 67% to 75% of the total P present in the sediment

Contrasting mercury and manganese deposition in a mangrove-dominated estuary (Guaratuba Bay, Brazil)

Sediment cores were taken at seven sites along the mangrove-bound Guaratuba Bay estuary (southern Brazil), with the purpose of assessing conditions controlling Hg deposition along a horizontal estuarine sediment gradient. The data suggest contrasting depositional patterns for Hg and Mn in this relatively pristine setting. Total Hg contents of bulk sediments ranged from 12 to 36 ng/g along the estuary, the highest values being found in muddier organic-rich sediments of the upper estuary (the corresponding mud gradient is 12 to 42 wt.%, and the organic matter gradient 4 to 10 wt.%). Thus, the deposition of fine sediments relatively enriched in mercury occurs primarily in closer proximity to the freshwater source. The data also indicate a reverse gradient in reactive Mn contents, ranging from 29 to 81 μg/g, and increasing seaward. This implies that reactive Mn is mobilized from fine-grained reducing mangrove forest sediments in the upper estuary, and deposited downstream in sandier, oxygen-rich nearshore sediments. These results suggest that mangrove-surrounded estuaries may act as barriers to mercury transport to coastal waters, but as a source of manganese. The present findings also imply that reactive Mn may be used as an indication of Hg depositional patterns in other similar coastal sedimentary settings

Fatores ambientais associados ao sobrepeso infantil Environmental factors associated with childhood overweight

OBJETIVO: Avaliar os fatores ambientais intra-uterinos, perinatais e familiares associados ao sobrepeso infantil, ainda controversos na literatura. MÉTODOS: Estudo transversal realizado com 627 crianças, de 6 a 10 anos, matriculadas em escolas urbanas públicas e privadas do município de Viçosa (MG). O estado nutricional das crianças foi classificado pelo índice de massa corporal, segundo a preconização do Centers for Disease Control and Prevention. Foram aferidas as medidas de peso, estatura, pregas cutâneas tricipital e subescapular, circunferências da cintura e do quadril e pressão arterial das crianças, sendo os fatores ambientais obtidos por meio de questionário, segundo informações maternas. Classificou-se o estado nutricional das mães segundo a recomendação do World Health Organization. RESULTADOS: Do total de crianças, 87,9% eram eutróficas e 12,1% apresentavam sobrepeso. De acordo com a análise de regressão logística múltipla, os fatores associados ao sobrepeso infantil foram apresentar mãe obesa (OR: 6,92; p<0,001), ser filho unigênito (OR: 1,87; p=0,03), permacer tempo superior a 3 horas diárias em frente à televisão (OR: 1,91; p=0,04), não realizar educação física na escola (OR: 4,80; p=0,02) e ser do sexo masculino (OR: 2,60; p=0,001). CONCLUSÃO: Este estudo permite elucidar a identificação de fatores ambientais, potencialmente modificáveis, associados ao sobrepeso infantil no município de Viçosa. A determinação dos fatores ambientais é importante, uma vez que o aumento na prevalência do sobrepeso na infância não pode ser totalmente explicado pelos fatores genéticos.<br>OBJECTIVE: The objective of this study was to assess intrauterine, perinatal and family factors associated with childhood overweight, which are still controversial in the literature. METHODS: This cross-sectional study included a total of 627 children aged 6 to 10 years, who were enrolled in public and private schools in the city of Viçosa, Minas Gerais State. The nutritional status of the children was classified according to their body mass index, as recommended by the Centers for Disease Control and Prevention. The following data were collected: weight, height, tricipital and subscapular skinfold thicknesses, circumferences of the waist and hip, and blood pressure. The environmental factors were determined by means of a questionnaire, answered by the mother. The nutritional status of the mothers was classified according to the World Health Organization criteria. RESULTS: Out of 627 children, 551 were normal weight children and 76 were overweight. According to multiple logistic regression analysis, the following factors were associated with childhood overweight: maternal obesity (OR: 6.92; p<0.001); being an only child (OR: 1.87; p=0.03); watching television for more than 3 hours per day (OR: 1.91; p=0.04); not practicing physical education at school (OR: 4.80; p=0.02) and being male (OR: 2.60; p=0.001). CONCLUSION: This study elucidated the potentially modifiable environmental factors associated with childhood overweight in the city of Viçosa. The determination of the environmental factors is important, since the increased prevalence of childhood overweight cannot be fully explained by genetic factors