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The current study combined chemical data on trace elements and polycyclic aromatic hydrocarbons (PAH) from sediment and used a multibiomarker approach in the catfish Sciades herzbergii to evaluate two different sites in São Marcos Bay, Brazil. Higher diffuse contaminations by trace elements and PAH were detected in the sediment of Porto Grande (PG) harbor than in the Ilha dos Caranguejos (IC) reference area. A multibiomarker was used in catfish to evaluate the bioavailability of PAH in bile and the effects of pollutants in target tissues. The parameters considered were oxidative stress biomarkers (SOD, CAT, GSH, GST and LPO) and histopathological alterations and were compared between two seasons. The biological responses revealed adverse effects on the population, as indicated by the presence of trace elements and PAH as stressors. Principal component analysis (PCA) of the biomarkers corroborated these results and indicated that fish from the PG site during the rainy season in 2019 exhibited many biological effects compared to 2018. Overall, the present study showed that environmental contamination increased over the years and provides information on the contamination of sediments in the São Marcos Bay, Brazil. The results showed that the presence of contaminants was correlated with the health status of the catfish S. herzbergii.

The present study aims to understand how ecological and biological factors affect the Hg levels in stingrays occurring in the Northeastern Brazilian coast. Total mercury (Hg), methylmercury (MeHg) and stable isotope (δ13C and δ15N) analyses were performed in five species. Hypanus americanus and Gymnura micrura showed the highest total Hg concentrations (300 and 176 ng.g−1, respectively). Hypanus guttatus exhibited a significant correlation between total Hg and size. Both species of the genus Hypanus presented the highest percentage of MeHg, around 100%, whereas the other species showed median percentages below 50%. The δ13C and δ15N signatures suggest that all studied species present the same foraging habitat but different trophic positions. Trophic position and animal size were the main factors influencing total Hg and MeHg concentrations in batoid species. The genus Hypanus, present in the Brazilian fish markets, showed concentrations above the accepted limits for human consumption.

The simple view of the classical phytoplankton–zooplankton–fish food chain (CFC) has been replaced by a more complex framework, integrating microbial compartments (microbial food web, MFW). Few studies considered all components of the pelagic MFW in freshwaters and mostly are from temperate regions. We investigated carbon partitioning in the CFC and the MFW in an Amazonian floodplain system and analyzed the strength of interactions among components through structure equation modeling. We hypothesized that (i) MFW contributes highly to total plankton biomass throughout the year; and (ii) all plankton communities increase in biomass during low water, increasing the role of trophic interactions. We collected 30 subsurface samples (nutrients and plankton communities). MFW predominated over CFC in carbon biomass, and plankton components and their interactions changed according to the contrasting water level. Because phosphorus can be a potentially limiting resource for strict primary producers, higher biomass and a more complex MFW occurred during low water. We concluded that hydrology is a key factor shaping biotic interactions during low-water periods, and that MFW plays a key role in floodplain lakes, being potential mixotrophy an important strategy for phytoplankton.

Damming rivers to generate electricity creates a lentic environment that favors methylmercury (MeHg) formation. Reservoirs in the Amazon are critical environments for MeHg formation, considering its old soils and the use of Hg in gold mining in the region. The objective of this study was to evaluate MeHg accumulation in three environmental compartments (aquatic macrophytes, suspended particulate matter (SPM) and sediment) of the Samuel reservoir (Western Amazon, Brazil), during the low water, ebb and high water hydrological periods, characterizing the dry season, the end of the rainy season and the rainy season, respectively. MeHg concentrations were determined through GC-AFS. The aquatic macrophytes presented higher %MeHg in their roots (up to 12%) compared to their other tissues. This ratio was 1.7 and 5.9 times higher than those observed for SPM and the sediment, but MeHg concentrations were the lowest (0.5–4.5 ng g−1) among the three environmental compartments. Contrary, the highest MeHg concentration was observed in SPM (104 ng g−1) during the low water period. The MeHg concentration in the sediment profile decreased with increasing depth (0.93–0.48 ng g−1) and with decreasing organic matter lability (increasing C:N ratio). In the SPM, on the other hand, MeHg concentration showed a positive association with increasing C:N ratio. We conclude that MeHg dynamics in the SPM are associated with the hydrological periods, with peaks during the low water period. The organic matter lability of the sediments is more limiting to the production of MeHg than the total Hg concentrations.

The energy transfer in the aquatic food chain is an important way for mercury (Hg) to enter other trophic levels. The objective of this work was to evaluate the Hg concentrations in plankton upstream and downstream of the Samuel Hydroelectric Reservoir, Rondonia, Brazil. Phytoplankton and zooplankton samples were collected with 20-μm and 68-μm nylon nets. An aliquot was removed for taxonomic analysis and another for total mercury determination, performed by cold vapor atomic absorption spectroscopy. Water physical-chemical parameters were also measured. The Hg concentrations in total plankton (phytoplankton and zooplankton samples) obtained at the three sampling upstream stations showed the same behavior, with the highest values registered in June 2005 (232 μg kg-1, 118 μg kg-1, 128 μg kg-1). The lowest values at stations J1 and M1 were recorded in November 2005 (4 μg kg-1 and 22 μg kg-1, respectively), while the lowest values at stations M4 and M8 were recorded in October 2005 (22 μg kg-1 and 5 μg kg-1, respectively). The Hg results found in the plankton in this study corroborate the results of other recent studies in the same region. The statistical analyses revealed that Hg concentrations in plankton do not explain the distribution of these organisms at the four sampling stations of Samuel Reservoir. Graphical Abstract.

This study was to evaluate the exposure to methylmercury (HgMe) and the potential health risk of Tupari Indians through the consumption of their main foods. Were collection of samples of plant foods and muscle tissue from different species of fish and wild animals consumed in three villages of the Rio Branco Indigenous Land in Rondonia, in the Brazilian Amazon. The HgMe was measured in an atomic fluorescence spectrophotometer with gas chromatography. The statistical treatment of the data was performed by software R. Of the six different plant species, only sweet potato (Ipomoea batatas) had mean concentrations of HgMe above the limit of detection of the analytical technique for the three villages. There was a significant difference in the levels of HgMe between the species of wild animals and fish belonging to the same alimentary habit. Carnivores presented higher levels of HgMe than those obtained for non-predators, both for fish and for wild animals. The results of the assessment of the potential risk to indigenous health indicated a total HgMe of the weekly ingestion rate (WIR) of between 8.4 and 15.0 μg / kg of body weight for the villages evaluated, extrapolating all reference doses ( RfD) regarding for the Provisional Tolerable Weekly Intake (PTWI). The risk quotients (RQ) varied from 5.3 to 21.4, considerably exceeding the limit (RQ ≤ 1), which allows to consider the impossibility of toxic effects of HgMe. The fishes accounted for the highest percentage of WIR of HgMe for all villages, with an emphasis on predatory species. Considering the nutritional value of fish meat, it is suggested the continuity of the consumption of this meat in the villages with preference for non-carnivores.

Scientific studies suggest that eating habits of traditional communities all over the world have been suffering changes as a result of gradual replacement of regional products with imported ones and also because of the increase of consumption of carbohydrates and trans fats. The nutritional state of populations, as riverine people in the Amazon region, has been widely affected by factors as changes in the eating and epidemiologic patterns. This study aims at the identification of the perception of dwellers of a riverine community the Brazilian Amazon region on their eating habits, their health and on the changes caused by development. This is a qualitative study, in which we used ethnographic semi structured interviews as a tool to collect data, conducted through a semi structured script, and applied to 16 dwellers/heads of families, in which 11 are men and 5 are women. The interviews were recorded in audio, full text transcribed and analyzed, and resulted in a descriptive system of categories and subcategories. As a result, we identified an increase of purchase capacity, greater participation in the market economy, lack of effective and continuous actions by the administrators of basic health services in the city. These joint factors contribute to the process of nutritional transition that is occurring in the community, as well as to the increase of health vulnerability of the dwellers.

Background The Madeira River (Amazon Basin) has been impacted by activities related to artisanal and small-scale gold mining (ASGM), deforestation and burning (for timber, agriculture, and hydroelectric dam projects). All these activities contribute to environmental mercury (Hg) release and cycling into the Amazon ecosystem and thus to changing lifestyles. Method We assessed exposure to total and MeHg in two small riverine communities of the Madeira River (Amazon): Lago Puruzinho (LP, n = 26 families) and Sao Sebastiao do Tapuru (SST, n = 31 families). Samples of human hair (n = 137), blood (n = 39), and feces (n = 41) were collected from adults and children (0–15 years of age). Results In women of childbearing age from LP village, the mean blood total-Hg (THg) (45.54 ± 24.76 μg.L−1) and MeHg (10.79 ± 4.36 μg.L−1) concentrations were significantly (p = 0.0024; p Conclusion Women and children excrete THg in feces in comparable concentrations. However, the mean fish consumption rate and blood MeHg are higher in the most remote villagers. Mother`s hair-Hg concentration is a good predictor of children’s hair-Hg.

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 CH4 in the tropics, consistently underestimate the atmospheric burden of CH4 determined via remote sensing and inversion modelling, pointing to a major gap in our understanding of the contribution of these ecosystems to CH4 emissions. Here we report CH4 fluxes 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 CH4 emissions. Methane fluxes from Amazon tree stems were up to 200 times larger than emissions reported for temperate wet forests6 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 CH4 a 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 CH4 emissions of 42.7 ± 5.6 teragrams of CH4 a year for the Amazon basin, based on regular vertical lower-troposphere CH4 profiles covering the period 2010–2013. We find close agreement between our ‘top-down’ and combined ‘bottom-up’ estimates, indicating that large CH4 emissions from trees adapted to permanent or seasonal inundation can account for the emission source that is required to close the Amazon CH4 budget. Our findings demonstrate the importance of tree stem surfaces in mediating approximately half of all wetland CH4 emissions in the Amazon floodplain, a region that represents up to one-third of the global wetland CH4 source when trees are combined with other emission sources.

This study evaluated the levels of total Hg and CH3Hg+ from a comprehensive perspective, considering the retention, leaching, and deposition of these contaminants in the main compartments (soil, plant litter, and sediment) of three landscapes (Atlantic Forest, pasture, and agricultural area) in a watershed in northern Rio de Janeiro State, Brazil. Variables analyzed were total Hg, CH3Hg+, organic carbon, total nitrogen, grain size, and surface area. In soil samples, total Hg levels were the highest in agricultural soil followed by forest soil and pasture (97.3, 87.6, and 77.1 ng g−1, respectively), and CH3Hg+ was lower than 1.7%. Total Hg levels in leaf litter varied between 22.6 and 34.2 ng g−1, and CH3Hg+ was 4.37%. In sediment, Hg (60–180 ng g−1) and CH3Hg+ (

Aquatic ecosystems in the Amazon are exposed to mercury, mostly from natural sources. Hg accumulation in fish tissues poses a risk to the local population since fish is one of the main sources of protein in the region. The aim of this study was to evaluate Hg distribution in demersal and pelagic carnivorous fish between seasons in Puruzinho Lake in the Brazilian Amazon. Total Hg was quantified in 221 individuals of 8 species obtained during the high water and low water seasons. Two-way ANOVA indicated an interaction between foraging habitat and season. During high water, total Hg concentrations were similar between demersal and pelagic fish, while in low water, total Hg levels were higher in demersal fish. Pelagic and demersal fishes’ Hg levels were similar between the two seasons.

Freshwater invertebrates occupy important roles in ecological processes and are frequently used as indicators of water quality. Their existence, however, is still obscure in many regions of the country, i.e. very few relevant studies have been conducted regarding their presence especially in the Amazon region. Thus, this study aimed to present an inventory of aquatic macroinvertebrates from the marginal region of an Amazonian lake. This study was conducted in a floodplain area, at the Extractivist Reserve of Cuniã Lake (margin of the Madeira River).To sample macrofauna, were collected sediment and aquatic macrophytes near the marginal region in seven sites during low-water season (August 2015) and the high-water season (February 2016). The environmental variables (water temperature (ºC), electric conductivity (μS /cm), pH, and dissolved oxygen (mg/L) were measured at each site and concentrations of organic matter in the sediment were also determined. A total of 28 taxa were recorded. The most significant taxa for the lake were the genera: Campsurus (Ephemeroptera: Polymitarcydae) and Tenagobia (Hemiptera: Corixidae. The lake presents diverse macrofauna, indicating good environmental quality and organic enrichment, which highlights the importance of flood in composition of local macrofauna.

An agroforestry system (AFS) describes the conjoint use of land for agricultural andforestry purposes. An AFS plays a strategic role in the mitigation of carbon dioxide(CO2) emissions, and stands as an alternative in land use that reduces mercury (Hg)remobilization in cultivated soils. This study evaluated the spatial variability of Hgconcentrations as indicators of environment changes and soil quality in different landcover and use systems in a rural settlement in southern Amazon, Brazil. Themethodological procedures were carried out as steps: the experimental units weredefined, physical and chemical characteristics of soil samples were analyzed, anddata were evaluated using conventional and spatial statistics. The AFS included hadbeen established 10 years before or more, and had high Hg retention capacity ,compared with Hg levels in soils on migratory agriculture or that are not fallowed .Therefore, due to low AFS improve soil quality due to the low intensity of harrowing,increasing retention of gaseous and particulate Hg in the soil. O sistema agroflorestal (SAF) é o uso da terra que integra no mesmo espaço ocultivo de espécies agrícolas e silviculturais. O SAF é apontado como estratégico namitigação das emissões de dióxido de carbono (CO2) e, é uma alternativa de uso daterra capaz de atenuar a remobilização de mercúrio em solo cultivado. O objetivo doestudo foi analisar a variabilidade espacial das concentrações do mercúrio comoindicador de mudança ambiental e da qualidade do solo em diferentes sistemas deuso e cobertura da terra no Assentamento Rural Umari, sul do Amazonas. Osprocedimentos metodológicos compreenderam a descrição das unidadesexperimentais; procedimentos analíticos dos atributos físicos e químicos do solo e;aplicação de métodos estatísticos espaciais e convencionais. Os solos sob SAF’scom dez anos ou mais de implantação apresentaram elevada capacidade deretenção de mercúrio quando comparado ao solo sob agricultura itinerante com ousem pousio. Portanto, admite-se que os SAF’s promovem melhorias à qualidade dosolo, contribuindo na retenção de mercúrio depositado na forma gasosa eparticulada.

Increasing concerns have been raised about the toxicity of mercury (Hg) to humans, especially for those that consume a great amount of fish. High Hg concentrations have previously been measured in Amazonian waterbodies, both resulting from natural and anthropogenic sources. However, few studies have been conducted so far in Amazonian lakes that are fished by local populations. In addition, few of those studies included methylmercury (MeHg), the most toxic and bioaccumulative Hg form, and evaluated the influence of physico-chemical conditions and season on Hg dynamics. In the present study, total Hg (THg) and MeHg concentrations were measured in bottom sediment as well as in two fish and two crocodile species of the Amazonian Cunia Lake. Bottom sediment MeHg concentrations were higher in the dry season than in the wet season, which is related to differences in physico-chemical (pH and electrical conductivity) conditions. Diet appeared to be related with animal tissue MeHg concentrations, with the herbivorous fish having lower MeHg levels than the predatory fish and crocodiles. Based on the measured tissue concentrations and published data on local person weight and fish consumption, MeHg risk to Cunia Lake populations was estimated. Although the MeHg fish tissue concentrations did not exceed national and international standards, a significant risk to the local population is anticipated due to their high fish consumption rates. Graphical abstract.

A cohort of 100 exclusively breastfed children was formed to study association between neurodevelopment and Hg exposure [1]. Detailed questionnaires were administered by trained interviewers to the mothers, and measurements of early child development were collected at 6, 36 and 60 months by trained nurses and psychologists using the Gesell Developmental Schedules. The association between prenatal and postnatal organic Hg (methyl-Hg from fish consumption and ethyl-Hg from Thimerosal-containing vaccine) exposures with Gesell scores of the four domains [Adaptive ability, Language development, Motor abilities (gross motor), and Personal-social ability] were studied in preschool children. Keywords: Child development, Fish, Mercury exposure, Hair mercury

Hg accumulation in fish is influenced by several factors including seasonality. In the Amazon, ecosystems are marked by strong seasonal variation in precipitation, which leads to drastic changes in the water level of lakes and rivers. The aim of this study was to evaluate Hg levels in muscle of detritivorous, herbivorous and omnivorous fish from an Amazon lake (Madeira River Basin, Amazonas, Brazil) over four seasons (rising water, high water, falling water and low water). We hypothesized that total Hg concentration varies during the seasons. The results indicate that total Hg levels in detritivorous fish were higher in rising and low water seasons while in herbivorous and omnivorous fish the total Hg concentration was higher during the rising water season. The hypothesis was supported by the results. Additionally, the study provides evidence that Hg levels in fish with different feeding habits are influenced by the flood pulse of the Amazon region.

The present study assesses mercury biomagnification and the trophic structure of the ichthyofauna from the Puruzinho Lake, Brazilian Amazon. In addition to mercury determination, the investigation comprised the calculation of Trophic Magnification Factor (TMF) and Trophic Magnification Slope (TMS), through the measurements of stable isotopes of carbon (δ13C) and nitrogen (δ15N) in fish samples. These assessments were executed in two different scenarios, i.e., considering (1) all fish species or (2) only the resident fish (excluding the migratory species). Bottom litter, superficial sediment and seston were the sources used for generating the trophic position (TP) data used in the calculation of the TMF. Samples from 84 fish were analysed, comprising 13 species, which were categorized into four trophic guilds: iliophagous, planktivorous, omnivorous and piscivorous fish. The δ13C values pointed to the separation of the ichthyofauna into two groups. One group comprised iliophagous and planktivorous species, which are linked to the food chains of phytoplankton and detritus. The other group was composed by omnivorous and piscivorous fish, which are associated to the trophic webs of phytoplankton, bottom litter, detritus, periphyton, as well as to food chains of igapo (blackwater-flooded Amazonian forests). The TP values suggest that the ichthyofauna from the Puruzinho Lake is part of a short food web, with three well-characterized trophic levels. Mercury concentrations and δ13C values point to multiple sources for Hg input and transfer. The similarity in Hg levels and TP values between piscivorous and planktivorous fish suggests a comparable efficiency for the transfer of this metal through pelagic and littoral food chains. Regarding the two abovementioned scenarios, i.e., considering (1) the entire ichthyofauna and (2) only the resident species, the TMF values were 5.25 and 4.49, as well as the TMS values were 0.21 and 0.19, respectively. These findings confirm that Hg biomagnifies through the food web of Puruzinho Lake ichthyofauna. The migratory species did not significantly change mercury biomagnification rate in Puruzinho Lake; however, they may play a relevant role in Hg transport. The biomagnification rate (TMS value) in Puruzinho Lake was higher than the average values for its latitude, being comparable to TMS values of temperate and polar systems (marine and freshwater environments).

Seasonal flooding changes chemical and morphometric characteristics of the tropical floodplain lakes, affecting stratification which can influence mercury dynamics. We investigate the influence of flooding on the mercury dynamics in an Amazon floodplain lake. Three points on the lake, the Solimoes River, and the connecting channel to the river were sampled along the annual flood pulse. During high-water, the lake was deep (12.7 m, on average) and the area farthest from the river was stratified with low oxygen and high methylmercury concentrations ([MeHg]) at depths below 7 m (0.37 ng l−1, on average). The two sites closest to the river were destratified and the [MeHg] was lower (0.077 ng l−1, on average along all depths). At low-water, the lake was shallower (3 m, on average) and destratified, with higher oxygen concentrations, and no difference in [MeHg] along the water column at all lake sites. Independent of season, the [MeHg] in the connecting channel was higher than those in the river. The [MeHg] in phytoplankton varied in response to changes in biomass, showing a biodilution effect. Variations in lake morphometry controlled the stratification and [MeHg] in the lake during the high-water. Floodplain lakes export hypolimnetic MeHg to their associated rivers during high-water.

This study aims to evaluate the Cr concentrations in surface water, suspended particles, and bottom sediments exposed to tannery effluent releases in the Candeias River. Cr concentrations were compared in relation to environmental thresholds imposed by United States Environmental Protection Agency (USEPA) and the Brazilian Environmental Council (CONAMA), and the geoaccumulation index (Igeo) was calculated in bottom sediment. Samples were collected in flood and dry seasons. Cr extraction was done by an acid extraction and quantified by flame atomic absorption spectrometry. Most samples were found to be below the environmental thresholds imposed by CONAMA and USEPA, except in the one from the discharge zone sampled during the dry season, showing values 1.5 and 6.1 higher than CONAMA in water and bottom sediment, respectively. Cr concentrations were significantly higher (P

Regions in the Amazon Basin have been associated with specific biogeochemical processes, but a detailed chemical classification of the abundant and ubiquitous dissolved organic matter (DOM), beyond specific indicator compounds and bulk measurements, has not yet been established. We sampled water from different locations in the Negro, Madeira/Jamari and Tapajos River areas to characterize the molecular DOM composition and distribution. Ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) combined with excitation emission matrix (EEM) fluorescence spectroscopy and parallel factor analysis (PARAFAC) revealed a large proportion of ubiquitous DOM but also unique area-specific molecular signatures. Unique to the DOM of the Rio Negro area was the large abundance of high molecular weight, diverse hydrogen-deficient and highly oxidized molecular ions deviating from known lignin or tannin compositions, indicating substantial oxidative processing of these ultimately plant-derived polyphenols indicative of these black waters. In contrast, unique signatures in the Madeira/Jamari area were defined by presumably labile sulfur-and nitrogen-containing molecules in this white water river system. Waters from the Tapajos main stem did not show any substantial unique molecular signatures relative to those present in the Rio Madeira and Rio Negro, which implied a lower organic molecular complexity in this clear water tributary, even after mixing with the main stem of the Amazon River. Beside ubiquitous DOM at average H / C and O / C elemental ratios, a distinct and significant unique DOM pool prevailed in the black, white and clear water areas that were also highly correlated with EEM-PARAFAC components and define the frameworks for primary production and other aspects of aquatic life. Funding Agencies|FAPERJ; CAPES; CNPq; Alexander von Humboldt; DAAD; STINT; VR; Cientista do Nosso Estado from FAPERJ

Damming rivers to construct hydroelectric reservoirs results in a series of impacts on the biogeochemical Hg cycle. For example, modifying the hydrodynamics of a natural watercourse can result in the suspension and transport of Hg deposits in the water column, which represents an exposure risk for biota. The objective of this study was to evaluate the influences of seasonality on the dispersion of total Hg in the Hydroelectric Power Plant (HPP)-Samuel Reservoir (Porto Velho/Brazil). Sampling campaigns were performed during the three following hydrological periods characteristic of the region: low (Oct/2011), ebbing (May/2012), and high (Feb/2013) water. Sediment profiles, suspended particulate matter (SPM), and aquatic macrophytes (Eicchornia crassipes and Oryza spp.) were collected, and their Hg concentrations and isotopic and elemental C and N signatures were determined. The drainage basin significantly influenced the SPM compositions during all the periods, with a small autochthonous influence from the reservoir during the low water. The highest SPM Hg concentrations inside the reservoir were observed during the high water period, suggesting that the hydrodynamics of this environment favor the suspension of fine SPM, which has a higher Hg adsorption capacity. The Hg concentrations in the sediment profiles were ten times lower than those in the SPM, indicating that large particles with low Hg concentrations were deposited to form the bottom sediment. Hg concentrations were higher in aquatic macrophyte roots than in their leaves and appeared to contribute to the formation of SPM during the low water period. In this environment, Hg transport mainly occurs in SPM from the Jamari River drainage basin, which is the primary source of Hg in this environment.

The present work tests the use of carapace fragments of the marine turtle Caretta caretta as a tool for environmental biomonitoring of mercury (Hg) and to evaluate the influence of biological and ecological factors in Hg concentrations. Samples of carapace fragments were obtained during the nesting season of 2012 and 2016 and were analyzed for their total-Hg and methyl-Hg concentrations and the isotopic composition of carbon and nitrogen (δ15N and δ13C). Seventy-six females were sampled, with an average size of 87.1 to 107 cm of curved carapace length (CCL). The results showed a wide variation in total Hg concentrations (3.3 – 1,672 ng g-1) and low concentrations of methyl-Hg, not showing any pattern of accumulation among the individuals. The isotopic composition of δ15N and δ13C suggests that the individuals sampled belong to a high trophic level but did not present any relationship with the Hg concentrations. It suggests that, at least with the existing results, and unlike other turtle species, carapace fragments of C. caretta cannot yet be used in environmental monitoring.

Floodplain systems are widespread in the Amazon and several studies have evaluated mercury biogeochemistry in these systems. The Amazon region can be considered a “hotspot” for the study of mercury (Hg), due to the naturally high concentration of the pollutant in its old soils and the anthropogenic emissions from small-scale gold mining activities. The periodic flooding influences the availability and distribution of Hg contamination. Therefore, it is possible that flooding can influence accumulation of Hg in fish. The aim of this study was to evaluate total Hg (THg) concentration in four seasons (rising water, high water, falling water and low water) in six fish guilds in a lentic part of a floodplain system (Puruzinho Lake). We hypothesized that fish guilds would show different seasonal patterns of THg concentration variation. A total of 2016 fish specimens were sampled over the four seasons. Two-way ANOVA indicated an interaction between guilds and seasonality (F = 7.3; p

Total mercury (Hg) and methylmercury (MeHg) circulation in a connected river-floodplain system composed of two black water (a small forest river, igarape, and Cunia Lake) and a white water body (Madeira River), located in the Madeira River Basin were evaluated during the rising-water, early and late falling-water periods. We assessed organic matter (C and N composition, (C:N)a; and δ13C isotopic signature), and physical and chemical influences (pH, dissolved O2, electric conductivity) in relationship to Hg and MeHg concentrations. Hg and MeHg concentrations in a sediment profile and three aquatic macrophytes (E. crassipes, E. azuera and Oryza sp.) were measured. Igarape and Cunia Lake showed higher Hg and MeHg concentrations (115–709; 10–25 ng g−1) in the suspended particulate matter compared (SPM) compared to the Madeira River (Hg: 5–16; MeHg: 0.2–0.3 ng g−1), partially independent of seasonality (p = 0.06). Total Hg had higher affinity for the SPM (1.75 times) than for dissolved organic matter. Organic matter characteristics correlated with MeHg concentrations (δ13C and (C:N)a; r2 = 0.79; p

The increase in global demand for electric energy is reflected in plans to construct numerous hydroelectric dams in South America that can cause chronic ecological impacts if not built and managed correctly. One of the main impacts generated by hydropower dams is the accumulation of Hg chemical species in their reservoir compartments and the downstream transport of these contaminants. Hg circulation in these environments has been studied for 27 years and this review brings a synthesis of the dynamics that are now well established, so that future studies can focus on gaps and inconsistent results in the literature. The topics cover the methylation process of Hg, its transfer along the trophic chain and the impacts downstream from dams. In addition, meta-analyses are used to propose regression models that explain Hg dispersion in environmental compartments of reservoirs, using as predictors morphological, spatial and temporal aspects of these environments.

The studies on metals in Madeira River’s principal flow show high variability of Co, Cr, Cu, Fe, Ni, Pb and Zn concentrations. However, the transfer of these metals from the main river channel, whose physical and chemical characteristics differ from those of lakes, has not been fully characterized. The objective of this study was to discuss how the transfer of Madeira River’s metals changes the spatial dynamics of these metals in sediments of the Puruzinho Lake (AM). The principal component analysis pointed to differences in the order of the data, creating two distribution zones of metals. The average concentrations of Co, Cu, Cr, Mn and Fe are higher in the area under the influence of the suspended solids coming from the Madeira River. The zoning of metals in lakes is structured by the forces acting across the river’s course at the same time as plains flood and generates ecotones. RESUMO Os estudos sobre metais no canal principal do Rio Madeira demostram alta variabilidade nas concentrações dos elementos Co, Cr, Cu, Fe, Ni, Pb e Zn. No entanto, a dinâmica da transferência destes metais da calha central do rio, que possui características físicas e químicas distintas às dos lagos, permanece não compreendida. O objetivo deste estudo foi discutir como a transferência de metais do Rio Madeira influencia a dinâmica espacial destes metais no sedimento de fundo do Lago Puruzinho (AM). A análise de componentes principais mostrou as diferenças na ordenação dos dados, gerando duas zonas de distribuição de metais. As concentrações médias de Co, Cu, Cr, Mn e Fe são superiores na região do lago sob influência dos sólidos em suspensão provenientes do Rio Madeira. A zonação de metais em lagos é estruturada pelas forças que atuam transversalmente ao curso do rio no momento da inundação das planícies, formando zonas de ecótonos.

Significant knowledge gaps exist regarding the fate and transport of persistent organic pollutants like dichlorodiphenyltrichloroethane (DDT) in tropical environments. In Brazil, indoor residual spraying with DDT to combat malaria and leishmaniasis began in the 1950s and was banned in 1998. Nonetheless, high concentrations of DDT and its metabolites were recently detected in human breast milk in the community of Lake Puruzinho in the Brazilian Amazon. In this work, we couple analysis of soils and sediments from 2005 to 2014 at Puruzinho with a novel dynamic floodplain model to investigate the movement and distribution of DDT and its transformation products (dichlorodiphenyldichloroethylene (DDE) and dichlorodiphenyldichloroethane (DDD)) and implications for human exposure. The model results are in good agreement with the accumulation pattern observed in the measurements, in which DDT, DDE, and DDD (collectively, DDX) accumulate primarily in upland soils and sediments. However, a significant increase was observed in DDX concentrations in soil samples from 2005 to 2014, coupled with a decrease of DDT/DDE ratios, which do not agree with model results assuming a post-ban regime. These observations strongly suggest recent use. We used the model to investigate possible re-emissions after the ban through two scenarios: one assuming DDT use for IRS and the other assuming use against termites and leishmaniasis. Median DDX concentrations and p,p'-DDT/p,p'-DDE ratios from both of these scenarios agreed with measurements in soils, suggesting that the soil parameterization in our model was appropriate. Measured DDX concentrations in sediments were between the two re-emission scenarios. Therefore, both soil and sediment comparisons suggest re-emissions indeed occurred between 2005 and 2014, but additional measurements would be needed to better understand the actual re-emission patterns. Monte Carlo analysis revealed model predictions for sediments were very sensitive to highly uncertain parameters associated with DDT degradation and partitioning. With this model as a tool for understanding inter-media cycling, additional research to refine these parameters would improve our understanding of DDX fate and transport in tropical sediments.

The Madeira River is the largest tributary of the Amazon River Basin and one of the most impacted by artisanal gold-mining activities, deforestation for agricultural projects, and recent hydroelectric reservoirs. Total Hg (and methylmercury-MeHg) concentrations was determined in 3182 fish samples of 84 species from different trophic levels as a function of standard size. Species at the top of the trophic level (Piscivorous, Carnivorous) showed the highest mean total Hg concentrations (51-1242 µg/kg), Planctivorous and Omnivorous species showed intermediate total Hg concentrations (26-494 µg/kg), while Detritivorous and Herbivorous species showed the lowest range of mean total Hg concentrations (9-275 µg/kg). Significant correlations between fish size (standard length) and total Hg concentrations were seen for Planctivorous (r=0.474, p=0.0001), Piscivorous (r=0.459, p=0.0001), Detritivorous (r=0.227, p=0.0001), Carnivorous (r=0.212, p=0.0001), and Herbivorous (r=0.156, p=0.01), but not for the Omnivorous species (r=-0.064, p=0.0685). Moreover, fish trophic levels influenced the ratio of MeHg to total Hg (ranged from 70% to 92%). When adjusted for standard body length, significant increases in Hg concentrations in the last 10 years were species specific. Spatial differences, albeit significant for some species, were not consistent with time trends for environmental contamination from past alluvial gold mining activities. Fish-Hg bioaccumulation is species specific but fish feeding strategies are the predominant influence in the fish-Hg bioaccumulation pattern.

Total mercury (THg) concentrations measured in two freshwater shrimp species (Macrobrachium depressimanum and Macrobrachium jelskii) showed a relationship with the location of artisanal and small-scale gold mining (ASGM) from the Madeira River Basin, Western Amazon. Between August 2009 and May 2010, 212 shrimp samples were collected in the confluence of the Madeira River with three of its tributaries (Western Amazon). THg concentration was quantified in the exoskeleton, hepatopancreas and muscle tissue of the shrimps by cold vapor atomic absorption spectrophotometry. There were no significant differences between the two shrimp species when samples came from the Madeira River, but Hg concentrations were significantly lower in a tributary outside the influence of the gold mining area. Average THg concentrations were higher in the hepatopancreas (up to 160.0 ng g−1) and lower in the exoskeleton and muscle tissue (10.0–35.0 ng g−1 and

Bioaccumulation of mercury and methylmercury in fish represents a serious risk to human beings. Extreme climate events like droughts may increase the trophic transfer of contaminants and net methylation of mercury. The present study assessed the influence of the 2014 drought on total mercury and methylmercury levels in fish from the lower Paraiba do Sul river basin. Contaminant levels were compared for Pimelodus fur, Pachyurus adspersus, Pimelodella lateristriga, Oligosarcus hepsetus, and Crenicichla lacustris captured in five sites in 2013 (N = 212) and 2014 (N = 231). The results indicate that levels of contaminants were higher during the drought in most species. Rainfall was weakly and negatively correlated with total mercury levels in most of the species. The weak relationship between these two variables was due to the indirect influence of rainfall on mercury bioaccumulation. In summary, drought increased the levels of two contaminants in fish.

Nature 552, 230–234 (2017); doi:10.1038/nature24639 (2017) In this Letter, owing to an error during the production process, the surname of author Humberto Marotta was incorrectly listed as ‘Ribeiro’. This has been corrected in the author list and the Author Contributions section of the original Letter.

Infant exposure to neurotoxic elements is a public health issue that needs monitoring with regard to breast milk composition. We studied six neurotoxic elements in breast milk samples at different stages of lactation in mothers from Porto Velho, Brazil. We used a flow-injection mercury system (FIMS) to determine total Hg concentrations and an inductively coupled plasma optical emission spectrometer (ICP-OES) to determine the concentrations of Al, As, Cd, Pb, and Mn in 106 donors of a human milk bank. Association rules analyses were applied to determine the pattern of binary and ternary mixtures of the measured exposants. The metal concentration was mostly below the limit of detection (LOD) for Cd (99%), Pb (84%), and Hg (72%), and it was above the LOD for As (53%), Mn (60%), and Al (82%), respectively. Median concentrations (dry weight) of Al, As, Hg, Mn, and Pb were 1.81 μg/g, 13.8 ng/g, 7.1 ng/g, 51.1 ng/g, and 0.43 μg/g, respectively. Al is singly the most frequent element to which infants are exposed. Occurring binary combination (> LOD) was 56% for Al-Mn, 41% for Al-As, 22% for Al-Hg, and 13% for Al-Pb. In 100% of neonates, exposure to Al-ethylmercury (EtHg) occurred through immunization with thimerosal-containing vaccines (TCV). Association rules analysis revealed that Al was present in all of the multilevel combinations and hierarchical levels and that it showed a strong link with other neurotoxic elements (especially with Mn, As, and Hg). (a) Nursing infants are exposed to combinations of neurotoxicants by different routes, dosages, and at different stages of development; (b) In breastfed infants, the binary exposures to Al and total Hg can occur through breast milk and additionally through TCV (EtHg and Al)

Objetivo : Estudar a prevalência de zumbido, verificando se há associação entre a queixa desse sintoma e o teor de mercúrio e mensurar seu impacto na qualidade de vida. Métodos : Estudo seccional em toda a população do Lago do Puruzinho, localizada na margem esquerda do Rio Madeira, cidade de Humaitá, Estado do Amazonas, Brasil. Todos os residentes maiores de 18 anos, de ambos os gêneros, foram submetidos à anamnese, avaliação otorrinolaringológica e exame audiológico. Os indivíduos que apresentaram queixa de zumbido responderam à versão traduzida do questionário Tinnitus Handicap Inventory (THI). Também foram pesquisados os teores de mercúrio total no cabelo desses indivíduos. Resultados: Para análise dos resultados sobre a queixa de zumbido, os sujeitos foram divididos em dois grupos quanto à presença ou não de zumbido. O Grupo 1 foi composto por indivíduos que apresentaram queixa de zumbido e o Grupo 2, por indivíduos sem zumbido. Foi observado que 40% dos indivíduos apresentaram escores do THI compatíveis com handicap leve. A análise da associação da presença de zumbido com os teores de mercúrio total no cabelo mostrou que ambos os grupos apresentaram níveis elevados de mercúrio, porém não ocorreram diferenças entre os grupos. Conclusão : Um quarto dos ribeirinhos apresentou queixa de zumbido e exposição significativa ao mercúrio, mas não houve associação entre o zumbido e os níveis elevados de mercúrio.

Pristine forest ecosystems provide a unique perspective for the study of plant-associated microbiota since they host a great microbial diversity. Although the Amazon forest is one of the hotspots of biodiversity around the world, few metagenomic studies described its microbial community diversity thus far. Understanding the environmental factors that can cause shifts in microbial profiles is key to improving soil health and biogeochemical cycles. Here we report a taxonomic and functional characterization of the microbiome from the rhizosphere of Brosimum guianense (Snakewood), a native tree, and bulk soil samples from a pristine Brazilian Amazon forest reserve (Cunia), for the first time by the shotgun approach. We identified several fungi and bacteria taxon significantly enriched in forest rhizosphere compared to bulk soil samples. For archaea, the trend was the opposite, with many archaeal phylum and families being considerably more enriched in bulk soil compared to forest rhizosphere. Several fungal and bacterial decomposers like Postia placenta and Catenulispora acidiphila which help maintain healthy forest ecosystems were found enriched in our samples. Other bacterial species involved in nitrogen (Nitrobacter hamburgensis and Rhodopseudomonas palustris) and carbon cycling (Oligotropha carboxidovorans) were overrepresented in our samples indicating the importance of these metabolic pathways for the Amazon rainforest reserve soil health. Hierarchical clustering based on taxonomic similar microbial profiles grouped the forest rhizosphere samples in a distinct clade separated from bulk soil samples. Principal coordinate analysis of our samples with publicly available metagenomes from the Amazon region showed grouping into specific rhizosphere and bulk soil clusters, further indicating distinct microbial community profiles. In this work, we reported significant shifts in microbial community structure between forest rhizosphere and bulk soil samples from an Amazon forest reserve that are probably caused by more than one environmental factors such as rhizosphere and soil depth.

This is one of the first studies to evaluate the effect of biometric variables (total length and weight), diet, and abiotic matrices (sediment and water column) on the bioaccumulation of methylmercury in tissues (muscle, liver, and gills) of four fish (two carnivore-invertivores, Pimelodus fur and Pachyurus adspersus; one carnivore-piscivore, Oligosarcus hepsetus; and one omnivore, Pimelodella lateristriga) in the lower section of a river in southeastern Brazil. Samples of fish (n = 120), water (n = 5) and sediment (n = 5) were collected at five sites characterized by pollution with mercury due to the use of organomercury fungicides and stream bed gold mining, commonly carried out in that section of the river in the 1980s. The results show that biometric variables are strongly correlated with methylmercury levels in muscle (r = 0.61, p 0.0005) of P. fur. As a rule, concentrations of total mercury and methylmercury did not vary considerably between the organs of the species of different food habits, because of the environmental conditions in the study area. Despite the low concentrations of mercury in sediments (0.05 mg kg

Mercury is a major pollutant in the Amazon River system, and its levels in fish and human hair are usually above the limit recommended by health agencies. The objective of this study was to analyze the methylmercury (MeHg) concentration in fish tissue from the Roosevelt River. The river's water velocity, depth, pH, temperature, electrical conductivity, dissolved oxygen and substrate type were measured, and fifty specimens distributed in 14 fish species were collected. A total of 64.3% of the sampled species were of the order Characiform and 71.4% of the species were carnivores. Fifty percent of the species had MeHg concentrations above threshold limit (Hg-T 0.5 mg kg-1) established for food by the World Health Organization. Cichla monoculus had the highest value of MeHg (2.45 mg kg-1). The MeHg concentration in fish varied according to dietary habits. The study also found bioaccumulation of MeHg in fish tissue in the following descending order: carnivorous > detritivorous > frugivore. Low significant correlations were found between fish weight or length and MeHg. Further studies on MeHg contamination are recommended in tissues of fish consumed in human riverine communities in the Roosevelt River Basin. Resumo O mercúrio tem sido um dos principais poluentes no sistema do rio Amazonas, cujos níveis em peixes e cabelo humano são geralmente acima dos limites recomendados pelos órgãos de saúde. O objetivo deste estudo foi analisar a concentração de metilmercúrio (MeHg) em tecidos de peixes do rio Roosevelt. Os atributos medidos do rio foram a velocidade da água, profundidade, pH, temperatura, condutividade elétrica, oxigênio dissolvido, e profundidade. Cinquenta espécimes distribuídas em 14 espécies de peixes foram coletadas. A ordem Characiformes representou 64,3% das espécies amostradas e os carnívoros representaram 71,4%. Cinquenta por cento das espécies apresentaram concentrações de MeHg acima do limite (Hg-T 0,5 mg kg-1) estabelecido para os alimentos pela Organização Mundial de Saúde. Cichla monoculus apresentou o maior valor de MeHg (2,45 mg kg-1). A concentração de MeHg variou por hábitos alimentares. Este estudo demonstrou bioacumulação de MeHg em tecidos de peixes, como segue: carnívoros > detritívoros > frugívoros. Baixas correlações entre peso ou cumprimento de peixe e MeHg foram encontradas. Recomenda-se um estudo mais aprofundado de contaminação do MeHg em tecidos de peixes consumidos nas comunidades ribeirinhas na bacia do rio Roosevelt.

The goal of this research was to evaluate the biodegradation of diesel by a microbial consortium collected in a region close to distributors of fuel. The experiments were monitored by SPME-GC-FID and SPME-GC-MS. The consortium showed a high potential for production of biosurfactants, presenting an emulsification index of 53%. The consortium degraded completely n-alkanes, while dimethylnaphtalene, hepthyl-cyclohexane and 2,6,10-trimethyl-undecane were partially degraded and pristane was not degraded. From this consortium five strains were isolated and identified as Acinetobacter baumannii. Based on this initial investigation this consortium appears to be effective for bioremediation in Porto Velho - RO region.

Subsistence ribeirinhos of the Amazon Basin depend on fish for their principal source of protein, but fish availability changes with seasonal high and low waters.To assess taxa and quantity of fish consumed and estimate attendant exposure to methyl-Hg in a traditional subsistence high fish-eating community of the Amazon Basin.120 villagers in 18 households were followed for 6 months (August to February) for weighed portions of fish consumed.Mean daily per capita fish consumption was high (406 g/day) with fish meals ranging from 4 to 14 times/week and an integrated yearly consumption of 148.2 kg/person. Median total-Hg concentrations in fish ranged from 0.011 to 0.409 ppm; six of the more consumed fish species comprised more than 50% of the fish consumed. The villagers mean hair-Hg concentration was high (17.4 +/- 11.5 microg/g), with both inter- and intra-household variation despite similar high fish consumption; only 7% showed hair-Hg concentrations5 microg/g, but 75% had hair-Hg levels above 10 microg/g. Maternal hair-Hg was significantly correlated with respective children's hair-Hg (Spearman r = 0.5390; p0.0001). The high daily fish intake of these villagers is predominantly of species with much lower Hg concentrations.In Amazonian lifestyle of ribeirinho communities traditional fish consumption is high and depends on available species; fish is also the principal via of meHg exposure and attendant hair-Hg concentrations.

DDT concentrations had been quantified in fishes and at 20 points along the "Puruzinho" lake. The determination of pollutants in the samples consisted in four consecutive steps: extraction, clean-up, fractionation and automatic injection in high resolution gas chromatography coupled to an electron capture detector. The ΣDDT results in fishes (ng g-1 dry weight) ranged from 0.3 to 71.4. The concentrations of ΣDDT on house soils varied from 2.0 to 55.4 ng.g-1 while forest soils the obtained values were between 1.6 e 13.3 ng g-1. The Shapiro-Wilk test showed that the distribution was not normal for both the results of the soil of the houses (p 0.290).

Because of heavy dependence on fish, Amazonian riparian communities are chronically exposed to high levels of methylmercury (MeHg). We studied fish-MeHg exposure (total hair-Hg, HHg) as a determinant of neurocognitive scores of children living in two geographically distant, culturally distinct and isolated poor communities of non-urban environments: Amazonian riverines (Riparians, n=38) of the Puruzinho Lake community in the Rio Madeira Basin and rural agrarians from Iuna, Espirito Santo (Agrarians, n=32). Nutritional status was estimated by anthropometry (Z-scores) and individual cognitive abilities were assessed by the Wechsler Intelligence Scale for Children-III (WISC-III) and the Human Figure Drawings (HFD), both validated versions for Brazilian children. Anthropometric assessment showed slightly elevated Z-scores for the Agrarian children (not statistically significant) but median HHg concentrations were 14.4 and 0.25microgg(-1) respectively for Riparian and Agrarian children (p=0.000). Despite paradoxical MeHg exposures, both groups showed comparable HFD scores but very poor performance in WISC-III test battery; median of sum of WISC-III subtests scores (SigmaTOT) were 17.9 and 28.6 (p

This study presents an overview of the appropriateness of the use of Amazonian cetaceans as sentinel species for environmental contamination by micropollutants, such as organochlorines and mercury. Due to the top position in food webs occupied by cetaceans and to their long life-span, high micropollutant concentrations have been verifi ed in their tissues, what allows an amplifi cation of the determination capacity by different analytical procedures. Besides providing an analytical advantage, the continuous micropollutant determination in cetaceans has been useful: as a reference of pollutant availability to other organisms; to integrate a complex signal of pollution; to quantify the ecological signifi cance of a contamination. Therefore, published information on the concentrations of the quoted pollutants in the Amazonian cetaceans Inia geoffrensis (boto) and Sotalia fl uviatilis (tucuxi) were gathered herewith. Carrying out comparison with data from Brazilian coastal cetaceans, it became clear how high the levels observed in Amazonian aquatic mammals are. In this context, mercury deserves to be highlighted. Despite the little volume of information on the concentrations of mercury, polychlorinated biphenyls and dichlorodiphenyltrichloroethane in Amazonian cetaceans, the existing information already demonstrates that the levels observed mirror the environmental contamination by such pollutants in distinct Amazonian environments. Perspectives for future investigations are also discussed, including possible ways of overcoming obstacles related to sampling of Amazonian cetaceans. Keywords: Brazil, Amazon, cetacean, mercury, organochlorines.

The variance of variables associated with neurodevelopment at 180 days, pre-natal variables (Hg in placenta, blood and hair) and post-natal Hg exposure (including Thimerosal-containing vaccines, TCV) were examined in 82 exclusively breastfed infants using principal component analysis (PCA). This multivariate method was applied to identify hierarchy and sets of interrelated variables. The PCA yielded a two-factor solution, explaining 92% of variance and summarizing most of the relevant information in the dataset matrix: the first component represented birth weight and vaccine (first doses of Hepatitis B and DTP) variability and explained 57% of variance; the second component represented a gradient of neurodevelopment (Gesell scores) and explained 35% of variance. The third component explained only 3% of the remaining 8% variance. Beside CNS priming by breastfeeding, infant development (birth weight) and time of immunization with TCV should be considered in epidemiological studies. PCA can classify sets of variables related to vaccination and neuromotor development schedules, clearly discriminating between earlier and later TCV exposures of exclusively breastfed infants. In conclusion, the incommensurable concept of the chance of toxic risk caused by TCV-EtHg exposure against the proven benefit of immunization is in no way disputed here. However, infant neurodevelopmental (ND) disorders linked to Thimerosal-Hg stands in need of proof, but PCA points to the possibility of identifying exposure risk variables associated with ND schedules.

Over the last 20 years several projects carried on the Madeira River basin in the Amazon produced a great amount data on total Hg concentration in different fish species. In this paper we discuss temporal trends in Hg contamination and its relation to body weight in some of those fishes, showing that even within similar groups, such as carnivorous and non-migratory fish, the interspecies variability in Hg accumulation is considerable. Vários estudos têm sido desenvolvidos nos últimos 20 anos na bacia do Rio Madeira (Amazônia) com o objetivo de diagnosticar a presença de mercúrio em peixes e compreender o ciclo deste elemento no meio ambiente tropical. Neste artigo são discutidas tendências temporais na concentração de Hg e sua relação com a massa corporal de algumas espécies de peixes com diferentes hábitos alimentares, coletadas no Rio Madeira e no reservatório da hidroelétrica de Samuel, no Rio Jamari, Estado de Rondônia. Foi avaliada uma amostragem de peixes de 14 anos (1987 - 2000) com 86 espécies e um total de 1100 espécimes.

Children are exposed to Hg from mothers (via placenta and lactation), environment (food), and in many parts of the world by thimerosal-containing vaccines (TCV) during immunization. Neurodevelopment studies based on infant hair-Hg (HHg) have been designed without explicit attention to the factors associated with changes in infant physiology and Hg sources of exposure. A longitudinal study of changes in HHg concentrations from birth to 5 years was done in a sample of children from Porto Velho (Rondonia), Brazilian Amazonia. The study extracted information from the asymmetry associated with maternal and infant HHg changes at specified sampling: birth (fetal exposure), 6 months of exclusive breastfeeding, 36 months (weaning) and 60 months (pre-school). The distribution of HHg in breastfed infants followed a pattern different from their mothers. While mothers had the highest HHg concentrations at childbirth, infants showed the highest HHg values at 6 months after the recommended full schedule (six shots) of immunization with TCV; after that, the downward trend in HHg shown by children coincided with both weaning and less frequent vaccination period (5 years). Extended lactation (up to 36 months) was not significantly associated with HHg of infants or mothers; however, significant association (Spearman’s r ) between maternal and infant HHg concentration was seen at birth ( r = 0.3534; P = 0.001), 6 months ( r = 0.4793; P r = 0.0122; P = 0.012) and 5 years ( r = 0.0357; P = 0.005). Maternal postpartum metabolic changes, infant development and transitional diets and possibly Hg from TCV contribute to the asymmetry of HHg changes between mothers and children.

Aim: Brazilian newborns immunized with hepatitis-B (thimerosal containing vaccine, TCV) receive the first dose within 24 h if delivered in public hospitals, but at a later time if born in private hospitals. We compared neurodevelopment (ND) in infants born in a state hospital (immunized within 24 h) and in privately run hospitals (immunized 2–4 days postnatally). Methods: We used the Gesell Developmental Schedules in 82 healthy exclusively breastfed infants at 6 months to assess motor skills, language development, comprehension capacity and social skills. Results: Compared to the group immunized 2–4 days after hospital discharge, the group immunized within 24 h showed no significant difference in ND delays. Despite the variation in gestational age (range 36–42 weeks) and TCV-ethylmercury (EtHg) dose (5.7–11.3 μgHg/kg b.w.) at birth, time of exposure to TCV showed no significant association with ND. Gesell Developmental Score was not significantly correlated with total parenteral EtHg/unit of body mass neither with the relative increase in hair-Hg (as an additional challenge to prenatal Hg exposure). Conclusion: In breastfed infants, differences in early exposure to TCV-EtHg cannot portend clinical neurodevelopment delays at 6 months. We speculate that breastfeeding remains a significant strategy to improve central nervous system protection of infants facing early exposure challenges.

Spanish moss, the epiphyte bromeliad Tillandsia usneoides (in Brazil, “Barba-de-velho”), has been used as biomonitor to evaluate air pollutants. In this article, total Hg concentrations were determined in bromeliads exposed at different areas of a Brazilian chlor-alkali plant while a calibration curve was built under controlled conditions in order to estimate atmospheric Hg concentrations. Hg determinations were performed by atomic absorption spectrometry. In the laboratory, the bromeliad exhibited linear Hg retention (r = 0.99; p < 0.05) when exposed to different Hg concentrations for 15 days under controlled conditions. While Tillandsia usneoides allows simultaneous and continuous monitoring of several workplaces inside a factory, identifying critical areas where workers can be overexposed, we conclude that bromeliad biomonitoring does not appear to be a trustworthy procedure to estimate Hg concentration in the air. However, this just can be a useful method for identifying and monitoring critical sites in continuous occupational and environmental control risk programs.

Mercury in the plankton of an Amazon natural lake, Puruzinho Lake (Brazil) This study has the objective of evaluating the total mercury concentrations (Hg) in plankton samples of Puruzinho Lake, which is located on the left margin of the Madeira River, 20 km downstream of the Humaita city (Amazon state, Brazil). Three samples were taken at a central part of the lake (S07°22’19.2”; W063°02’32.2”) during rainy (February 2004 and May 2005) and dry (October 2004) seasons. Plankton samples were collected using two nets of nylon. An aliquot of each plankton filtrate was preserved for posterior plankton identification, and another lyophilized for Hg analysis. The total mercury was determined by atomic absorption spectrophotometry and cold vapor generation (FIMS-400). The highest concentration of mercury in the plankton was observed in February of 2004 (337 µg kg –1 ), the rainy period. Levels in the plankton were comparable to those from regions considered contaminated by Hg. Inputs of mercury are likely to happen due to run off after soil flooding during the rainy season, which also turn this metal available to the planktonic community.

The aim of this study was to evaluate the quality of fish meat in relation to inorganic contaminants (Zn, Pb, Cu, Cr, Ni and Hg), following the Brazilian Health Surveillance Agency (ANVISA) standards in five Amazonian fish exposed to untreated urban sewage. Trace metal concentrations were evaluated in the muscle tissues of Schizodon fasciatus (herbivorous), Potamorhina latior (detritivorous), Triportheus angulatus (omnivorous), Plagioscion squamosissimus (carnivorous) and Rhaphiodon vulpinus (piscivorous), sampled upstream and downstream of Santo Antônio's Hydroelectric Dam, Madeira River (Porto Velho City, Brazil). An acid chemical digestion was used to extract trace metals from the tissues, and atomic absorption spectrometry methods were used to quantify the trace metal concentrations. Fish samples showed values above allowed limits for Cr (0.10 mg.kg-1), except in Plagioscion squamosissimus (0.09 mg.kg-1). Potamorhina latior specimens sampled downstream showed higher values for Cr (p

Sex plays an important role in the kinetics and dynamics of methylmercury in some animals. Although fish is the main source of mercury exposure to consumers, the role of sex in fish-Hg bioaccumulation is less known. We studied total Hg (THg) concentrations in 2538 samples (males=1052, females=1486) of fish from different trophic levels (herbivorous, planctivorous, detritivorous, omnivorous, carnivorous, piscivorous); for each species we made a post hoc estimation of the minimum number of samples required to detect variance-based differences between sexes. Only five of the 41 studied species showed significant difference between sexes; but, no consistent dominant pattern of THg concentrations favored either sex. When grouped by trophic levels, overall mean difference in THg concentrations between males and females were not statistically significant. Correlation analysis showed sex-dependent THg bio-accumulation as a function of condition factor was statistically significant and negative for all trophic levels (detritivorous, herviborous, omnivorous, planctivorous, carnivorous, and piscivorous). Conclusions: Sex is not the main driver of Hg bioaccumulation in most Amazonian fish species; however, studies have to consider the minimum number of samples required to ascertain sex effects on THg bioaccumulation. Therefore, neither the surveillance of environmental pollution nor the current food advisories based on muscle THg need to change because of fish sex.

The central nervous system is a critical target for Hg toxicity in all living organisms. Total Hg (THg) was determined in brain and muscle samples of 165 specimens of eight species of catfish (Brachyplatystoma filamentosum; Brachyplatystoma platynemum; Brachyplatystoma rousseauxii; Brachyplatystoma vaillantii; Phractocephalus hemiliopterus; Pseudoplatystoma punctifer; Pseudoplatystoma tigrinum; Zungaro zungaro) from the Madeira River, Brazilian Amazon. Despite the narrow range of Fishbase trophic level (4.2-4.6) the median THg concentrations ranged from 0.39 to 1.99mg/kg and from 0.03 to 0.29mg/kg respectively in muscle and brain from the studied species. Overall, the median concentration for all samples analyzed was 0.93mg/kg and 0.16mg/kg respectively in muscle and brain; most samples (76%) showed muscle Hg concentrations0.5mg/kg. There were statistically significant THg differences between sex (femalemales). The correlation between THg concentrations in muscle and brain was statistically significant (r=0.9170; p0.0001). In the studied specimens, fish total length was significantly correlated with muscle (r=0.3163; p=0.0001) and brain (r=0.3039; p=0.0003) THg; however, fish age was negatively and significantly correlated (r=-0.2991; p=0.0012) with THg in muscle but not with THg in brain (r=-0.0190; p=0.8492). Amazonian catfish accumulate high levels of Hg in muscle and brain; however, brain-THg concentrations can be predicted from muscle-THg. Muscle-Hg in catfish can be a tool to detect brain-Hg concentrations associated with environmental Hg.