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Wetlands are the largest global source of atmospheric methane (CH4), a potent greenhouse gas. However, methane emission inventories from the Amazon floodplain, the largest natural geographic source of CH4in the tropics, consistently underestimate the atmospheric burden of CH4determined via remote sensing and inversion modelling, pointing to a major gap in our understanding of the contribution of these ecosystems to CH4emissions. Here we report CH4fluxes from the stems of 2,357 individual Amazonian floodplain trees from 13 locations across the central Amazon basin. We find that escape of soil gas through wetland trees is the dominant source of regional CH4emissions. Methane fluxes from Amazon tree stems were up to 200 times larger than emissions reported for temperate wet forests and tropical peat swamp forests, representing the largest non-ebullitive wetland fluxes observed. Emissions from trees had an average stable carbon isotope value (δ13C) of −66.2 ± 6.4 per mil, consistent with a soil biogenic origin. We estimate that floodplain trees emit 15.1 ± 1.8 to 21.2 ± 2.5 teragrams of CH4a year, in addition to the 20.5 ± 5.3 teragrams a year emitted regionally from other sources. Furthermore, we provide a ‘top-down’ regional estimate of CH4emissions of 42.7 ± 5.6 teragrams of CH4a year for the Amazon basin, based on regular vertical lower-troposphere CH4profiles covering the period 2010–2013. We find close agreement between our ‘top-down’ and combined ‘bottom-up’ estimates, indicating that large CH4emissions from trees adapted to permanent or seasonal inundation can account for the emission source that is required to close the Amazon CH4budget. Our findings demonstrate the importance of tree stem surfaces in mediating approximately half of all wetland CH4emissions in the Amazon floodplain, a region that represents up to one-third of the global wetland CH4source when trees are combined with other emission sources.

Large amounts of reactive oxygen species are produced in hemodialysis (HD) patients, and, at higher concentrations, reactive oxygen species are thought to be involved in the pathogenesis of cardiovascular disease. It has been proposed that selenium (Se) may exert an antiatherogenic influence by reducing oxidative stress. The richest known food source of Se is the Brazil nut (Bertholletia excelsa, family Lecythidaceae), found in the Amazon region.

Abstract: Human milk is the best source of nourishment for the newborn because of its incomparable balanced nutrition and psychological benefits to the infant's development. Dental fillings containing metallic Hg are the primary source of inorganic Hg contamination of humans. We studied Hg concentrations in the breast milk of mothers during the first month (7–30 d) postnatal in relation to the number of amalgam surfaces. The concentration of total Hg was determined in 23 samples of human milk collected from lactating mothers with a varied number of amalgam dental restorations. The average number of amalgam surfaces was 6.87 (5.81, SD) with a range of 0 to 20. The mean concentration of total Hg in breast milk was 5.73 ng/g (range: 0–23.07). The Pearson corrlation coefficient was significant (r=0.6087, p=0.0057) between breast-milk Hg and number of amalgam surfaces. In 56.5% of low-fish-eating mothers, the amount of Hg likely to be ingested by breastfed infants is above the World Health Organization reference.

Guanabara Bay (GB), located in the Rio de Janeiro State, is still a productive estuary on the south-eastern Brazilian coast. It is an ecosystem heavily impacted by organic matter, oil and a number of other toxic compounds, including Hg. The present study aimed to comparatively evaluate the aquatic total mercury (THg) and MeHg contamination, and the ratios of MeHg to THg (% MeHg), in 3 species of marine organisms,Micropogonias furniert— carnivorous fish (N=81),Mugil spp.— detritivorous fish (N=20) andPerna perna— filter-feeding bivalves (N=190), which are widely consumed by the population. A total of 291 specimens were collected at the bay in different periods between 1988 and 1998. THg concentrations were determined by cold vapour AAS with stannous chloride as a reducing agent. MeHg was extracted by dithizonebenzene and measured by GC-ECD. Analytical quality was checked through certified standards. All organisms presented both low THg and MeHg concentrations and they were below the maximum limit of 1,000 μg Hg.kg-1wet wt. as established for human intake of predatory fish by the new Brazilian legislation. Carnivorous fish showed higher THg and MeHg concentrations, and also % MeHg in muscle tissues, than organisms with other feeding habits and lower trophic levels. The average of THg concentrations in carnivorous fish was 108.9 ± 58.6 μg.kg-1wet wt. (N=61) in 1990 and 199.5 ± 116.2 μg.kg-1wet wt. (N=20) in 1998, but they presented different total length and body weights. The average THg content in detritivorous fish was 15.4 ± 5.8 μg.kg-1wet wt., whereas THg concentrations ranged from 4.1 to 53.5 μg.kg-1wet wt. for the molluscs. The THg and MeHg contents of mussel varied according to the sampling point and water quality. MeHg concentration in detritivorous fish was similar to MeHg concentration in molluscs, but there was a significant difference in the MeHg/THg ratio: the carnivorous fish presented higher MeHg percentages (98%) than the detritivorous fish (54%) and the molluscs (33%). Weight-normalised average concentration of THg in carnivorous fish collected in 1990 (0.18 ± 0.08 μg.g-1/0.7 kg wet wt.) and in 1998 (0.16 ± 0.09 μg.g-1/0.7 kg wet wt.) presented no significant difference (t=1.34;P< 0.5). In conclusion, the low THg and MeHg concentrations in the organisms from the GB ecosystem, are related to its eutrophic conditions and elevated amounts of suspended matter. In this situation, Hg could be strongly complexed or adsorbed by the particulate, which would dilute the Hg inputs and reduce its residence time in the water column, with a consequent decrease in its availability to organisms.

DDT contamination was investigated in soil, sediment, and chicken eggs from an endemic leishmaniasis area located in Rio de Janeiro City, Brazil. The last DDT application in this area was in 1990, for sand-fly vector control. Sampling campaigns were conducted in 1997 and 1999. DDT was extracted by use of a modified soxhlet apparatus and analysis was performed by gas chromatography with electron capture detector. The results show that, in 1997, soil samples contained up to 351 μg.kg−1d.w. of ∑DDT near the insecticide-sprayed sites. In 1999, the soil concentration decreased to 112 μg.kg−1d.w. of ∑DDT. Sediments from small creeks also showed low concentrations (up to 32.9 μg.kg−1d.w. of ∑DDT). Chicken eggs had, on average, 1.98 mg.kg−1∑DDT (twice FAO's maximum residue limit), comprising 82% of p,p′-DDE. Taking into account the egg results, DDT bioaccumulation is a question of concern. Considering just the egg consumption, it was estimated that DDT intake in the study area is 0.38×10−4mg.kg−1body weight.day−1whereas the reference maximum dose (US EPA) is 5×10−4mg.kg−1body weight.day−1. This approach can be used to estimate DDT exposure in other places where DDT contamination may be of concern, especially in places where locally produced animals and eggs are a significant portion of the diet.

The objective of this study was to develop an educational program for preventing metallic mercury emissions due to the burning of mercury–gold amalgams inside houses. The main participants were adolescents from a school in the city of Poconé, State of Mato Grosso. The program was developed in five stages, including discussions of the methods and exhibition of slides showing people working in activities including the garimpos, planning activities as dramatizations, making posters and preparing a screenplay for the production of a video, discussing how to prevent indoor burning of gold–mercury amalgams, and a final evaluation of the adolescents about what they had learned during the program. The evaluation of the impact was done through a comparison of correct answers from a questionnaire before and after the development of the educational activities and by means of a comparison of urinary mercury in school students and a group of residents (women) at three different times: before the program (2.30 μg/L), 6 months after (2.90 μg/L), and 11 months after (1.49 μg/L).

In order to evaluate aquatic environmental mercury (Hg) and methylmercury (MeHg) contamination, a wide variety of fish species were sampled from some tributaries of the Brazilian Amazon river system, the Balbina reservoir and the Pantanal watersheds. These water bodies present different mercury inputs and biogeochemical characteristics. Amazon fish, which are the main pathway of MeHg to the local population, are the most important protein source for them, and fishing is a significant economic activity throughout these regions. MeHg in fish samples (164) were analysed with an efficient extraction technique and measured by GC–ECD. Analytical quality was checked through intercomparisons between two laboratories with local samples and a certified standard from IAEA. MeHg concentrations of carnivorous, omnivorous, detritivorous and herbivorous species ranged from 0.1 to 1.25 mg kg−1wet wt and the mean percentages of MeHg to total mercury were usually higher than 80%. Carnivorous (piscivorous) fish, which represented 74% of all samples, effectively showed higher MeHg concentrations as well as a higher MeHg/total mercury ratio in muscle tissue than fish from lower trophic levels. In general, MeHg concentrations in carnivorous fish were higher in places close to goldmining activities, the Madeira river and the Tapajós river near Itaituba city. The MeHg/total mercury ratios in fish were higher in non‐impacted areas and with smaller amounts of suspended particulate materials (Negro river, Balbina reservoir and Pantanal watershed). No MeHg seasonal variability was observed in Serrasalmus rhombeus(carnivorous fish) from the Madeira river basin during the year. High variability in MeHg levels was observed in muscle of the same carnivorous species fish with similar weights sampled at the same place and by similar nets. Copyright © 1999 John Wiley & Sons, Ltd.

In order to evaluate aquatic environmental mercury (Hg) and methylmercury (MeHg) contamination, a wide variety of fish species were sampled from some tributaries of the Brazilian Amazon river system, the Balbina reservoir and the Pantanal watersheds. These water bodies present different mercury inputs and biogeochemical characteristics. Amazon fish, which are the main pathway of MeHg to the local population, are the most important protein source for them, and fishing is a significant economic activity throughout these regions. MeHg in fish samples (164) were analysed with an efficient extraction technique and measured by GC–ECD. Analytical quality was checked through intercomparisons between two laboratories with local samples and a certified standard from IAEA. MeHg concentrations of carnivorous, omnivorous, detritivorous and herbivorous species ranged from 0.1 to 1.25 mg kg⁻¹ wet wt and the mean percentages of MeHg to total mercury were usually higher than 80%. Carnivorous (piscivorous) fish, which represented 74% of all samples, effectively showed higher MeHg concentrations as well as a higher MeHg/total mercury ratio in muscle tissue than fish from lower trophic levels. In general, MeHg concentrations in carnivorous fish were higher in places close to goldmining activities, the Madeira river and the Tapajós river near Itaituba city. The MeHg/total mercury ratios in fish were higher in non-impacted areas and with smaller amounts of suspended particulate materials (Negro river, Balbina reservoir and Pantanal watershed). No MeHg seasonal variability was observed in Serrasalmus rhombeus (carnivorous fish) from the Madeira river basin during the year. High variability in MeHg levels was observed in muscle of the same carnivorous species fish with similar weights sampled at the same place and by similar nets. Copyright © 1999 John Wiley & Sons, Ltd.

The main aims of the present study were to determine the concentrations of Cu, Ni, Zn, Cr, Pb, Cd, Fe, Mn and Al in drinking water after conventional treatment as well as the efficiency of metal removal by the different water treatment plants (WTP) in the State of Rio de Janeiro, Brazil. Suspended particles are the critical compartment in the heavy metal removal by the WTP. Results show that the treatment does not affect the metal concentration in the dissolved phase, except for Fe.

The present study aimed to evaluate methylmercury in fish and human hair samples from an important hydroelectrical reservoir, Balbina (Brazil, Amazon). It presents a quite intense fishing activity and there is no known goldmining activity in its watershed. Fish and human hair were analyzed with a new extraction technique and measured by GC-ECD. Analytical quality was checked through intercomparisons between two laboratories with local samples and certified standards from IAEA. Methylmercury in hair ranged from 2.0 to 21.6 μg · g−1with a mean of 8.76±5.20 μg · g−1(N=20), while the methylmercury percentages were above 90. Fish presented methylmercury levels ranging from 0.03 to 0.9 μg · g−1wet wt with a mean of 0.24±0.18 μg · g−1wet wt (N=32), which is below the limit established for food by Brazilian legislation (0.5 μg · g−1wet wt) and methylmercury mean percentages were above 95%. The total mean daily methylmercury intake ranged from 11 to 55 μg for 70% of the sampled population from the village based on a daily consumption of about 110 g of fish with methylmercury concentrations in the range of 0.1 to 0.5 μg · g−1. This calculation is consistent with methylmercury concentrations in hair samples in the range of 2.6 to 13.1 μg · g−1.

Amalgamation has been used for more than 4500 years in mining processes. Mercury has been extensively used in South America by Spanish colonizers for precious metal recovery. It is estimated that between 1550 and 1880, nearly 200,000 metric tonnes of mercury was released to the environment. During the present gold rush, Brazil is first in South America and second in the world in gold production (with 90% coming from informal mining orgarimpos). At least 2000 tonnes of mercury has been released to the environment in the present gold rush. From the mid 1980s, environmental research has been carried out in impacted Amazon rivers, later followed by human exposure studies. The river basins studied were the Tapajós, Madeira, and Negro, but also some man-made reservoirs and areas in central Brazil. The analyses mainly involved sediments, soil, air, fish, human hair, and urine. The results show high variability, perhaps related to biological diversity, biogeochemical differences in the river basins, and seasonal changes. High mercury values also occur in some areas with no known history of gold mining. The results available document a considerable impact on environmental mercury concentrations and frequent occurrence of human exposure levels that may lead to adverse health effects.

This corrects the article DOI: 10.1038/nature24639

Dietary intake of selenium (Se) plays an important role as an antioxidant and anti-inflammatory agent due to its antioxidant properties and the richest known food source of Se is the Brazilian nut, found in the Amazon region, Brazil. The aim of this study was to evaluate the effect of the Brazilian nut supplementation on oxidative stress and inflammation markers and lipid stratus in HD patients. Forty HD patients (57.5% men, 53.3±16.1yrs) were studied and received 1 nut (around 5g) a day for three months. The GSH-Px, 8-isoprostane, 8-OHdG, TNF-α and IL-6 levels were determined by ELISA before and after supplementation. The LDL-c and HDL-c levels were determined by enzymatic colorimetric method using the specific kit. After 3 months supplementation, cytokines, 8-OHdG, 8-isoprostane levels decreased and the activity of GSH-Px increased significantly. Besides, after supplementation, the HDL levels increased and LDL levels decreased significantly.ParametersBefore supplementationAfter supplementationGSH-Px (nmol/mL/min)34.06±5.240.3±8.4⁎8-isoprostane (pg/mL)12.2±4.56.6±4.6*8-OHdG (pg/mL)214.5(1.0−1042.0)18.7 (1.0−78.8)*IL-6 (pg/mL)67.1 (21.1−80.2)13.5 (12.8−22.2)*TNF-α (pg/mL)21.0±0.313.9±8.7*HDL (mg/dL)39.0±14.244.7± 4.8*LDL (mg/dL)86.0±28.774.7±29.5*⁎p<.0001