Metal and metalloid distribution in different environmental compartments of the middle Xingu River in the Amazon, Brazil

Double-layer membrane framework-based gold microelectrode for determination of natural labile copper in complex water environments

Copper (Cu) is an essential trace element for plankton, but excessive amounts can be toxic and threaten the ecosystems and human health. However, the determination of low concentration labile Cu (CuLabile) in complex water environments remains a huge challenge. In this work, a gold microelectrode (μ-GE) with high sensitivity and anti-fouling capability was fabricated based on a double-layer membrane framework consisting of ion-exchange polymer (Nafion) and agarose gel (LGL). The Nafion stabilized on the surface of μ-GE not only enhanced the voltammetric response significantly through its specific cation-exchange ability with Cu2+, but also improved the chemical and mechanical stability. In addition, the LGL formed an another efficient anti-fouling membrane which could prevent the contamination of electrode by microorganisms, particulate matters, etc. Benefiting from the synergistic effects of the double-layer membrane framework, the so-designed LGL/Nafion functionalized μ-GE (LGL/Nafion/μ-GE) exhibited excellent detection performance for Cu, as well as anti-biofouling capability. Two linear ranges (0.5-10 nM and 10-1000 nM) were achieved for Cu2+, with a detection limit of 0.043 nM in NaCl solution with a salinity of 30 ‰. The LGL/Nafion/μ-GE was successfully applied for the determination of CuLabile in complex environmental water samples including natural seawater and artificial algae culture medium. Furthermore, the real-time changes of CuLabile in culture medium of Synechococcus sp.PCC 7002 was obtained successfully with the LGL/Nafion/μ-GE via in situ continuous monitoring.

Human health risks associated to trace elements and metals in commercial fish from the Brazilian Amazon

Fish constitutes the main protein source for the Amazonian population. However, the impact of different anthropogenic activities on trace element and metal accumulation in fish and their risks for human health at a regional scale remain largely unexplored. Here we assessed exposure levels of 10 trace elements and metals (Cr, Mn, Fe, Ni, Cu, Zn, As, Cd, Pb, and Hg) in 56 samples belonging to 11 different species of fish from the Brazilian Amazon. We studied the relationship between exposure levels, fish origin, and fish feeding habits, and assessed toxicological and carcinogenic risks for the Amazonian population. No significant correlation was found between sampling site and exposure levels to the studied elements, but a significant difference was found between the accumulation of some metals and the position of the fish species in the food chain. The concentrations of Cr and Hg in fish flesh were found to exceed the Brazilian limits for human consumption. This study shows that current fish consumption patterns can lead to estimated daily intakes of Hg, As and Cr that exceed the oral reference dose, thus posing a toxicological concern. Furthermore, carcinogenic risks may be expected due to the continued exposure to Cr and As. The results of this study show that the consumption of wild caught fish in the Amazon region should be controlled. Moreover, continued monitoring of trace element and metal contamination in fish and on the health of the Amazonian population is recommended, particularly for riverine and indigenous communities.

Performance, kinetic characteristics and bacterial community of short-cut nitrification and denitrification system at different ferrous ion conditions

In order to explore the operation performance, kinetic characteristics and bacterial community of the short-cut nitrification and denitrification (SND) system, the SND system with pre-cultured short cut nitrification and denitrification sludge was established and operated under different ferrous ion (Fe (II)) conditions. Experimental results showed that the average NH4+-N removal efficiency (ARE) of SND system was 97.3% on Day 5 and maintained a high level of 94.9% ± 1.3% for a long operation period. When the influent Fe(II) concentration increased from 2.3 to 7.3 mg L-1, the sedimentation performance, sludge concentration and organic matter removal performance were improved. However, higher Fe(II) of 12.3 mg L-1 decreased the removal of nitrogen and CODCr with the relative abundance (RA) of Proteobacteria and Bacteroidetes decreased to 30.28% and 19.41%, respectively. Proteobacteria, Bacteroidetes and Firmicutes were the dominant phyla in SND system. Higher Fe(II) level of 12.3 mg L-1 increase the RA of denitrifying genus Trichococcus (33.93%), and the denitrifying genus Thauera and Tolumonas dominant at Fe(II) level of no more than 7.3 mg L-1.

Change in water quality in an Amazonian microbasin: ecological and human health implications

The decline in the quality of water resources in the Amazon is very rapid in cities suffering from unplanned urban growth. The region has two defined seasons, winter (wet) and summer (dry), which directly affect the behavior of contaminants in aquatic ecosystems. The aim of this study was to assess the ecological and human health risks associated with the use of the watershed. In addition, an ecological index was proposed: the Quality Index for Aquatic Life, for the risk of contaminants to aquatic life. Sampling was carried out at six points in the Juá watershed. Physicochemical parameters, major anions, metals and total phosphorus were analyzed at both stations between 2020 and 2021. The highest concentrations of contaminants were found in the rainy season, due to the washing away of the banks. In this sense, Cl presented a concentration more than 307 times higher than that permitted by Brazilian legislation (wet). The ecological index showed that the watershed has a high risk of metals such as Cr III and Cr VI for the biota. The human health risk analysis showed a low risk; however, the lack of basic sanitation in the city indicates that monitoring of urban water resources is necessary.

Abiotic and biotic factors influencing heavy metals pollution in fisheries of the Western Amazon

The escalating industrial and artisanal extraction of natural resources in the Amazon Basin has centered it into the spotlight of global environmental concern. This study deals with the environmental problems of heavy metals pollution and biomagnification, which stem from mining, agricultural, petrochemical, and industrial discharges. We conducted an extensive investigation, analyzing 360 fish specimens representing 58 species, to assess the concentrations of 11 metals (Al, As, Cd, Cr, Cu, He, Mn, Ni, Pb, Zn, and Hg) along the Ecuadorian sections of the Napo and Pastaza watersheds. Stable isotope analyses (δ15N and δ13C) were employed to determine their trophic positions and potential biomagnification risks. Sampling was carried out during two distinct hydrological seasons to capture seasonal variations in metal concentrations. Furthermore, we estimated species-specific daily heavy metal intake levels. The results of our study revealed that 15 fish species and 53 individual specimens exhibited heavy metal concentrations surpassing recommended standards, with elevated levels of Al, As, and Hg posing significant risks to human consumers with daily intakes of 0.46 kg/day. Notably, our investigation unveiled concerning trends, including increased metal concentrations, Hg biomagnification within fish populations from the Pastaza watershed, and an association between smaller fish size and higher metal content. This study provides a crucial baseline for monitoring future environmental changes and understanding the persistent impacts of heavy metal pollution in the Ecuadorian Amazon region and the broader Western Amazon. It underscores the urgent need for sustainable environmental management practices to mitigate the escalating threat to these vital ecosystems.

Ecological risk assessment for metals in sediment and waters from the Brazilian Amazon region

Pollution by metals is a matter of concern around the world. In recent decades, the high population growth in urban centers has significantly magnified the entry of these pollutants into aquatic ecosystems. The Amazon region, intense migratory flow, gold mining, and industrialization have been considered the main driving forces for increasing metal pollution. Thus, the main aim of this study is to conduct, for the first time, an Ecological Risk Assessment (ERA) based on metal concentrations measured in the sediment and water of several aquatic environments from the Amazon basin, based on the risk quotient values (RQ = measured environmental concentration - MEC/predicted no effect concentration - PNEC). In addition, the metal contamination factor (CF) was estimated. Although metal concentrations in water were generally low, these values were far above the limits established by current national legislation in many areas, showing higher concentrations for the metals Co, Pb, Cr, Cu, and Ni. Concentrations of Mn, Cu, Ba, Pb, Co, Ni, Cr, Zn, Cd, and As were especially high in the sediment for several evaluated environments. The ERA for the water compartment revealed that 56% of the studied areas presented high risk (RQ > 1) for aquatic biota. In the sediment, 66% of the sites presented a high risk and 40% medium risk (RQ = 0.1-1). The CF indicated that 49% of the sampling points had high contamination and only 24%, had low contamination. These results reveal that monitoring studies in the Amazon region, provides important information so that public policies for the preservation of water resources can be strengthened in the Amazon.

A systematic review on metal contamination due to mining activities in the Amazon basin and associated environmental hazards

Metal contamination associated with mining activities has been considered one of the main environmental pollution problems in the Amazon region. Understanding the levels of metal contamination from mining activities requires a good understanding of background metal concentrations, which may vary notably according to the geology/lithology characteristics of the region, soil type, and predominant biogeochemical processes. This review assessed 50 papers and reports published between 1989 and 2020 describing environmental concentrations of different metals and metalloids (As, Hg, Mn, Fe, Cd, Cu, Cr, Pb, Ni, and Zn) in water and sediments of mining and non-mining areas in five geographic regions of the Amazon basin. Metal enrichment caused by mining activities was calculated and exposure concentrations were compared with sediment and water quality standards set for the protection of aquatic life. Significant enrichments of Cd, Cu, Cr, Fe, Hg, Mn, Ni and Zn were observed in mining areas in both sediment and water. Regarding background levels in the different geographic regions, the highest prevalence of metal enrichment (i.e., concentrations 10 to 100-fold higher than mean background values) in sediment samples was found for Fe (100% of samples), Ni (90%), and Mn (69%). For water, high prevalence of metal enrichment occurred for Zn, Mn, and Fe (100% of samples), and for Hg (86%). Hg, Fe, Pb, Cu, Cd, Ni and Zn exceeded water and/or sediment quality standards in a significant number of samples in the proximity of mining areas. This study indicates that mining activities significantly contribute to water and sediment contamination across the Amazon basin, posing hazards for freshwater ecosystems and potentially having human health implications.

Metal bioaccumulation and genotoxicity in Oreochromis niloticus reared in farming pools influenced by mining activities in Napo, in the Ecuadorian Amazon

Mining areas may suffer long-term metal contamination and represent harmful remnants of former mining activities. In the northern Amazon of Ecuador, former mining waste pits are used in Oreochromis niloticus (Nile tilapia) fish farming. Given the high consumption of this species by the local population, we aimed to estimate human consumption risks by determining Cd, Cu, Cr, Pb, and Zn tissue bioaccumulation (liver, gills, and muscle) and genotoxicity (micronucleus essay) in tilapia cultivated in one former mining waste pit (S3) and compare the findings to tilapias reared in two non-mining areas (S1 and S2); 15 fish total. Tissue metal content was not significantly higher in S3 than in non-mining areas. Cu and Cd were higher in the gills of tilapias from S1 compared to the other study sites. Higher Cd and Zn were detected in the liver of tilapias from S1 compared to the other sampling sites. Cu was higher in the liver of fish from S1 and S2, and Cr, in the gills of fish from S1. The highest frequency of nuclear abnormalities was observed in fish from S3, indicating chronic exposure to metals at this sampling site. The consumption of fish reared at the three sampling sites results in a 200-fold higher Pb and Cd ingestion than their maximum tolerable intake thresholds. Calculated estimated weekly intakes (EWI), hazard quotients (THQ), and Carcinogenic Slope Factors (CSF_ing) denote potential human health risks, indicating the need for continuous monitoring in this area to ensure food safety not only in areas affected by mining, but in general farms in the region.

Multiple anthropogenic influences in the Pará River (Amazonia, Brazil): A spatial-temporal ecotoxicological monitoring in abiotic and biotic compartments

The mineral wealth of the Amazon region is prone to intense exploration with consequent metals mobilization in ecosystems. Besides that, a number of other anthropogenic activities contribute to the imbalance of this important environment. The Pará River is an important water body in the Amazon basin and is under multiple anthropogenic influences, including disorderly urbanization, port activities and processing of minerals such as bauxite and kaolin. In this study, metals concentrations (Al, Cr, Pb, Ba, Ni, and Mn) in water, sediment and organisms (the fish Cheirocerus goeldii and the shrimp Macrobrachium amazonicum) and biochemical biomarkers (total antioxidant capacity, ACAP and lipid peroxidation, LPO) were analyzed along five points in the Para River with different distances to a center of anthropogenic activity, in three seasonal periods (rainy, transition and dry). Metals concentrations were similar among sites in each seasonal period but Aluminium (Al) presented the highest concentrations among all analyzed metals both in sediment and water considering all sampling points and all seasonal periods. In the dissolved fraction, Al had values above those established by the local environmental agency, especially during the rainy season. In the biotic compartment, both fish and shrimps showed higher concentrations of metals (Al and Ba) in the rainy season compared to the other seasons. Shrimp was more responsive to metal accumulation than fish, showing an adaptive response of biomarkers. Fish showed an increase of LPO in gills for individuals from the point of greater anthropogenic interference during the rainy season, but no differences in metal accumulation. We conclude that there is a seasonal pattern of metals concentration in different environmental compartments. Metal concentration in organisms and biomarkers responses, showed the effect of anthropogenic influences, which was not evident in results from chemical analyses alone, due to the intensive hydrodynamics in the region.

Flood pulse as a driving force of Pb variation in four fish guilds from Puruzinho Lake (western Amazon)

The Brazilian Amazon is heavily impacted by mining activities, especially by gold and cassiterite mining. Pb is a contaminant released during cassiterite extraction, and it stands out for its high toxicity. The present study aimed to evaluate the effect of flood pulse on Pb dynamics in four fish species with different feeding habits (Cichlapleiozona: carnivorous, Mylossomaduriventre: herbivorous, Prochilodus nigricans: detritivorous, and Serrasalmus rhombeus: piscivorous) over four hydrological periods in Puruzinho Lake (Brazilian Amazon), which receives water from the Madeira River. The risk assessment for daily Pb intake through the consumption of these fish by the local riverside population was also carried out. Fish species were sampled during four Amazonian hydrological periods: rising water, high water, falling water, and low water. Pb and stable isotopes (δ¹⁵N and δ¹³C) measurements were carried out on fish muscle. The flood pulse had the same effect on Pb concentrations of all the fish species regardless of their feeding habits, as we found a nonsignificant interaction between these variables. The Pb in fish muscle increased in the flood season (rising and high water) and decreased in the dry season (falling and low water). The Pb concentration in fish increased significantly with their trophic level (δ¹⁵N), evidencing the occurrence of biomagnification of the element along the trophic chain (R² = 0.24). The main food source of the herbivorous fish (δ¹³C) was very distinct from that of the others, which had a large overlap in their values. Regarding risk assessment, the daily Pb intake through consumption of the herbivorous species during high water (17.82 ± 19.68 µg∙day^-1) exceeded the limit determined by the Food and Drug Administration (FDA) of 12.5 µg∙day^-1, representing a health risk to the riverside population of Puruzinho Lake.

Enhancement and mechanisms of iron-assisted anammox process

Anaerobic ammonium oxidation (anammox) is a sustainable biological nitrogen removal technology that has limited large-scale applications owing to the low cell yield and high sensitivity of anammox bacteria (AnAOB). Fortunately, iron-assisted anammox, being a highly practical method could be an effective solution. This review focused on the iron-assisted anammox process, especially on its performance and mechanisms. In this review, the effects of iron in three different forms (ionic iron, zero-valent iron and iron-containing minerals) on the performance of the anammox process were systematically reviewed and summarized, and the strengthening effects of Fe (II) seem to be more prominent. Moreover, the detailed mechanisms of iron-assisted anammox in previous researches were discussed from macro to micro perspectives. Additionally, applicable iron-assisted methods and unified strengthening mechanisms for improving the stability of nitrogen removal and shortening the start-up time of the system in anammox processes were suggested to explore in future studies. This review was intended to provide helpful information for scientific research and engineering applications of iron-assisted anammox.

Distribution of metals in different environmental compartments and oxidative stress biomarkers in Bryconops caudomaculatus (Osteichthyes: Characiformes) from a bauxite mining area in the Eastern Amazon

The Eastern Amazon is rich in bauxite ore. The extraction and processing of bauxite lead to the mobilization of Aluminum (Al) and other metals in environmental. We evaluated the metals (Al, Mn, Ba, and Cr) concentration in tissue, water, and sediment associated with antioxidant and oxidative damage responses in Bryconops caudomaculatus. The samplings were done in two hydrological periods (post-rain and post-dry periods) and at three points, located at two rivers: one in the surroundings of the mining area (P1) and other inside the mining area, upstream (P2), and downstream (P3). Defense antioxidant system biomarkers analyzed were total antioxidant capacity (ACAP) and glutathione-S-transferase (GST) activity. As an oxidative damage biomarker, the lipoperoxidation (LPO) was evaluated. Metals concentrations in the water and sediment were higher in the post-rain period compared to post-dry period. The water samples were acidic, with dissolved Al concentrations above the values established by local legislation at all points. In the gills, the metals accumulation was higher in fish from in the surrounding and upstream sites, and in the liver, was higher in fish from downstream site. Fish from the surrounding had increased antioxidant defenses, with higher ACAP in all tissues and higher GST in the gills. Consequently, they had lower levels of LPO. Fish from the mining area had decreased antioxidant defenses, with lower ACAP in all tissues and lower GST in the gills. Consequently, they had higher levels of LPO, indicating oxidative stress. The fish muscle was not responsive to GST and LPO at all sites. We conclude that the oxidative stress observed in the gills and liver of B. caudomaculatus from the area modified by the mining activity reflected the local anthropogenic impact status.

Tip-porous microneedle: A highly stable sensing platform for direct determination of labile metals in natural seawater

Nanomaterial-functionalized voltammetric microsensors are promising tools for detecting trace metals at low concentrations in the complex environment of natural seawater. However, the sensitivity reduction caused by the loss of modified nanomaterials in the detection process has always been a major problem. Herein, to fabricate a highly stable sensing platform, a microneedle electrode with a hierarchical porous tip was prepared through electrochemical etching technology to firmly embed nanoparticles. Using copper (Cu) as a model trace metal, a micro-cluster needle sensor based on a gold nanoparticle (AuNP)-embedded tip-porous microneedle electrode (P-MNE) was fabricated for the direct voltammetric determination of labile Cu in natural seawater. The porous structure of P-MNE not only provided a larger specific surface area and active sites for AuNPs which had excellent electrocatalytic performance for Cu²⁺ determination, but also protected from their loss during the detection process in seawater. Therefore, this novel micro-cluster needle sensor exhibited significantly improved stability with a relative standard deviation (RSD) of 1.5% for 30 detections. The linear range of Cu²⁺ on this micro-cluster needle sensor was from 0.1 to 1000 nM with a detection limit of 0.03 nM. More importantly, this micro-cluster needle sensor was successfully used for directly detecting labile Cu in natural seawater samples without any preaccumulation treatment or reagent addition to obtain the contribution proportions of the labile fraction in total dissolved Cu. Furthermore, this sensing platform might also be extended to the reliable determination of other labile metals in seawater by changing the functional nanoparticles embedded in the nanopores.

Spatial-temporal dynamics of Cr in fish from Puruzinho Lake (Western Amazon) and dietary risk assessment

Cr contamination is a growing concern in the Amazon. Along with the rise of cattle farming in the region, tanneries are becoming more common and threatening environmental quality, since the effluents from this activity are rich in Cr. The objective of this study was to evaluate the seasonal and spatial dynamics of Cr in fish with different feeding habits from Puruzinho Lake, located in the Madeira River basin, also determining the daily intake of Cr associated with the consumption of these fish by the population that lives around the lake. Seasonality and feeding habits directly affected Cr dynamics in fish (p < 0.0001), with medians of Cr concentration ranging between 0.07 mg kg^-1 in the species Cichla pleiozona, a carnivorous fish, and 0.62 mg kg^-1 in Mylossoma duriventre, a herbivorous fish. The high Cr concentrations in M. duriventre were related to the biodilution effect of Cr in the trophic chain (R² = 0.14, p < 0.0001). The consumption of M. duriventre by the population was associated with the highest daily intake of Cr (55.5 μg∙day^-1), exceeding the recommended limits of Cr intake (35 μg∙day^-1). However, no harmful effects on health are expected due to the ingestion of Cr through the consumption of fish from Puruzinho Lake. Spatial analysis showed an increasing trend in Cr concentrations along the Madeira River, suggesting that contaminants present in the river are being carried over long distances and are reaching preserved areas of the Amazon.

Interplay of Seasonality, Major and Trace Elements: Impacts on the Polychaete Diopatra neapolitana

Simple Summary

Coastal systems often serve as sinks for toxic elements, and seasonality has been responsible for many changes in the physical and chemical parameters of waters and sediments, leading to geochemical alterations in aquatic systems and the alteration of element uptake rates in organisms. Diopatra neapolitana worms were collected from five sites of the Ria de Aveiro lagoon in the autumn, winter, spring, and summer of 2018/2019 and were tested to check for differences in the biochemical responses (cell damage, antioxidant enzymes, biotransformation enzymes, and energy-related parameters) among seasons and sites. In general, the results demonstrated that enzyme activities were higher in spring and summer due to high temperatures and element bioaccumulation. Energy-related parameters presented with higher levels in spring and autumn, which was mainly due to element bioaccumulation. Oxidative damage was higher during winter and was related to salinity and decreases in temperature. This study demonstrated that abiotic factors influence the geochemistry of elements and that both significantly affect organism performance in low-contamination systems, such as the Ria de Aveiro lagoon. This knowledge is important to understand how ecological and economically relevant species such as D. neapolitana respond to environmental changes.

Abstract

Polychaetes are known to be good bioindicators of marine pollution, such as inorganic contamination. Major and trace elements are commonly present in sediment and may be accumulated by polychaetes such as the tubiculous Diopatra neapolitana. In this study, D. neapolitana individuals were collected in the autumn, winter, spring, and summer of 2018/2019 from the Ria de Aveiro lagoon (western Portugal) to understand how seasonality influences element accumulation. The impact of the interaction of seasonality and elements on oxidative status, energy metabolism, and oxidative damage was also assessed. The obtained results showed that the activity of the antioxidant enzymes catalase, glutathione S-transferases, and non-protein thiol levels were higher in summer and that superoxide dismutase, lipid peroxidation, and electron transport system activity increased in winter. The lowest glycogen levels were observed during spring, and protein carbonylation was the highest during autumn. These results could mainly be related to high temperatures and the bioaccumulation of Al, As, Mn, and Zn. Energy-related parameters increased during spring and autumn, mainly due to the bioaccumulation of the same elements during spring and summer. Lipid damage was higher during winter, which was mainly due to salinity and temperature decreases. Overall, this study demonstrates that seasonality plays a role in element accumulation by polychaetes and that both impact the oxidative status of D. neapolitana.

Trace metal concentrations, fluxes, and potential human health risks in West Africa rivers: a case study on the Bia, Tanoé, and Comoé rivers (Cote d'Ivoire)

Downstream water pollution resulting from anthropogenic pressures on upstream water can cause conflicts, especially in transboundary rivers basins. This study assessed trace metals cadmium, lead, copper, and iron total concentrations, fluxes, and the potential human health risks through ingestion or dermal contact of waters at the mouth of three West African transboundary rivers: the Comoé, Bia, and Tanoé rivers. The results showed highest total concentrations during the months of May and October and statistically comparable concentrations in the rivers. The fluxes discharged to the Atlantic Ocean through the Aby and Ebrie Lagoons are as high as average values found elsewhere in the World. Trace metals lead, copper, and iron fluxes were highest during the month of October in the Bia, Tanoé, and Comoé rivers. The cadmium flux was highest during the month of October in the Bia and Comoé rivers, and during the months of February and December in the Tanoé River, indicating that contamination came mainly from upstream waters and the draining of the river basins. The Pearson correlation analysis showed that the trace metals were mainly from anthropogenic sources including gold mining and agriculture. The total concentrations were lower than international guidelines set by the World Health Organization (WHO). However, the potential human health risk assessment results suggest a significant likelihood of community exposure to harmful effects but not to cancers through water ingestion. This work recommends including small rivers when assessing global river metal fluxes to the ocean and also reducing upstream inputs from human activities to mitigate downstream river water pollution.

Connections among Land Use, Water Quality, Biodiversity of Aquatic Invertebrates, and Fish Behavior in Amazon Rivers

Rivers in the Amazon have among the greatest biodiversity in the world. The Xingu River, one of the tributaries of the Amazon River, has a length of 1640 km, draining 510,000 km2 in one of the most protected regions on the planet. The Middle Xingu region in Brazil has been highly impacted by mining and livestock farming, leading to habitat fragmentation due to altered water quality. Therefore, comparing two rivers (the preserved Xingu River and the impacted Fresco River) and their confluence, the aims of the present study were to (1) assess the land uses in the hydrographic basin; (2) determine the water quality by measurements of turbidity, total solids, and metals (Cd, Cu, Fe, Mn, Pb, Zn, and Hg); (3) compare the zooplankton biodiversity; and (4) to evaluate the avoidance behavior of fish (Astyanax bimaculatus) when exposed to waters from the Xingu and Fresco Rivers. Zooplankton were grouped and counted down to the family level. For the analysis of fish avoidance, a multi-compartment system was used. The forest class predominated at the study locations, accounting for 57.6%, 60.8%, and 63.9% of the total area at P1XR, P2FR, and P3XFR, respectively, although since 1985, at the same points, the forest had been reduced by 31.3%, 25.7%, and 27.9%. The Xingu River presented almost 300% more invertebrate families than the Fresco River, and the fish population preferred its waters (>50%). The inputs from the Fresco River impacted the water quality of the Xingu River, leading to reductions in local invertebrate biodiversity and potential habitats for fish in a typical case of habitat fragmentation due to anthropic factors.

Bioaccumulation and human health risks of potentially toxic elements in fish species from the southeastern Carajás Mineral Province, Brazil

Anthropogenic activities may have increased the concentrations of potentially toxic elements (PTEs) in fish from the southeastern Carajás Mineral Province in Brazil, which has not yet been studied. The objectives were to determine the quality parameters of surface water and bottom sediments, and to assess the bioaccumulation and risks of Al, Fe, Ba, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Ti, V and Zn in fish species from the southeastern Carajás Mineral Province. Water, sediments and fish species (Colossoma macropomum, Curimata cyprinoides, Geophagus sp., Leporinus trifasciatus, and Serrasalmus eigenmanni) were collected in 14 areas in the municipalities of Parauapebas, Marabá and Canaã dos Carajás, contemplating the Gelado Stream and the Parauapebas, Tapirapé and Itacaiúnas Rivers. Water samples were subjected to physicochemical analysis using a multiparameter meter. Concentrations of PTEs in all samples were quantified by inductively coupled plasma-optical emission spectrometry. Enrichment factor (EF) and geoaccumulation index (Igeo) were calculated to study the sediment enrichment and contamination. Ecological and human health risk assessments were performed to determine the risks to the environment and population's health. EF and Igeo revealed that the sediments from the Parauapebas River and Gelado Stream are respectively enriched by Ba, Co, Cu, Cr, Mn, Pb, and Ba, Co, Cr, Ni, Pb and V. The concentrations of Fe (1.67 mg L^-1) and Mn (0.11 mg L^-1) in water and the concentrations of Cr (>0.1 mg kg^-1) and Pb (>2 mg kg^-1) in fish were above the Brazilian legislation thresholds. The ecological risk assessment revealed considerable risk from Ni and moderate risk from multiple PTEs in sediments from the Gelado Stream. Human health risks were detected for Pb in all fish species and for Mo in L.trifasciatus. These results indicate that techniques for monitoring and controlling contamination must be implemented by the environmental agencies.

High concentrations of metals in the waters from Araguari River lower section (Amazon biome): Relationship with land use and cover, ecotoxicological effects and risks to aquatic biota

The Araguari River is one of the most important water body in the Brazilian state of Amapá. However, the quality of its waters has been deteriorating and, recently, high concentrations of metals were found in water samples collected from its lower section. Overall, we aimed to evaluate land use and cover around three sampling sites located in the Araguari River lower section and its contribution to water pollution by metals; correlate land use pattern with detected metal concentrations; assess acute toxicity using the Daphnia similis test and genotoxicity using the Danio rerio bioassay of water samples from the three sampling sites; and investigate the risks arising from metals present in waters to aquatic biota. Riparian forest around all sampling sites is fragmented owing to the expansion of pasture areas, which showed a significant positive correlation (p < 0.05) with the concentrations of Hg and Cu in water samples. Water samples from sampling sites 2 and 3 presented acute toxicity for D. similis, and the D. rerio bioassay confirmed the presence of genotoxic pollutants in the waters from all sampling sites. Our preliminary risk assessment showed that individual concentrations and the mixture of metals posed a high risk to aquatic biota. Taken together, our results demonstrate that the conversion of native forest to pastureland contributes to water contamination by metals, which contributes to the risks to aquatic biota.

Fish tissues for biomonitoring toxic and essential trace elements in the Lower Amazon

Brazilian soils can have high concentrations of toxic elements, mainly mercury (Hg) and arsenic (As), metals also associated with anthropogenic activities (e.g. intensive agriculture, mining, deforestation and hydroelectric plants). This can lead to large amounts of these elements reaching and/or being mobilized in the aquatic ecosystem, which constitutes a serious threat to the environment and to the health of local populations. Thus, we evaluate the feasibility of analyzing the tissues of freshwater fish species for monitoring toxic and trace element accumulation within the aquatic ecosystem in the Lower Amazon, Brazil. Two fish species were considered: Cichla temensis (Tucunaré), a carnivorous species, and Pterygoplichthys pardalis (Acari), a detritivorous species. Samples of liver and muscle from both species were evaluated in relation to their potential use for biomonitoring purposes. The study findings clearly demonstrate the value these fish species and tissues, particularly liver, for biomonitoring toxic and trace element concentrations in the aquatic environment across the study region. While Tucunaré liver proved the best option for biomonitoring elements that accumulate through the food chain (e.g. Hg), Acari liver better reflected elements that typically accumulate in the sediments (e.g. As). Moreover, the trace element profiles, determined using chemometric (multivariate) techniques, differed greatly in specimens from waters in the Andean mountain range (sampling sites located in the main course of the Amazon River) with high sediment concentrations, and in specimens from the Guyana and Brazilian shields (Porto Trombetas on the Trombetas River and Itaituba on the Tapajós River). The findings also indicate that deposition of elements in freshwater fish in this area is mainly associated with the geological origin of the soils and that large amounts of toxic elements can reach the aquatic ecosystem due to anthropogenic activities, thereby posing a serious danger to the environment and the health of the riverside communities.

Toxic and essential trace element concentrations in fish species in the Lower Amazon, Brazil

The Lower Amazon region (Western Pará, northern Brazil) is greatly affected by mining exploitations (particularly artisanal gold mines) and other industrial and intensive agricultural activities with potentially strong impacts on aquatic ecosystems. Although such impacts include contamination with various toxic elements, to date only the effects of Hg have been considered. In this study, toxic and trace element concentrations were determined in the flesh of 351 fish specimens, including detritivores (Acarí, Pterygoplichthys pardalis), omnivores (Piranha, Pygocentrus nattereri; Pirarucu, Arapaima sp.) and carnivores (Caparari, Pseudoplatystoma fasciatum; Tucunaré, Cichla ocellaris), during the dry and wet seasons in 2015 and 2016. The range of concentrations of toxic element residues were 2-238 μg/kg fresh weight for As, 1-77 μg/kg for Cd, 4-1922 μg/kg for Hg and 1-30 μg/kg for Pb. Only the maximum concentrations of Hg established in the Brazilian legislation for fish destined for human consumption (0.5 mg/kg) were exceeded (in 16% of carnivorous species). The large between-species and seasonal differences observed for all these toxic elements are probably related to the seasonal behaviour and dietary habits of the different fish species. By contrast, essential trace element concentrations were low and not related to seasonal or dietary factors, and the observed differences may be at least partly related to the metabolism of each species. The associations between Hg and the essential trace elements Se, Fe, Co and Mn deserve special attention, as these trace elements may play a role in Hg cycling and methylation and merit further evaluation with the aim of reducing Hg toxicity in aquatic environments.

Metals, n-Alkanes, Hopanes, and Polycyclic Aromatic Hydrocarbon in Sediments from Three Amazonian Streams Crossing Manaus (Brazil)

Pollution is increasing in the Amazon region and its real impact is still unclear. Since this region is of great interest to the global community, this study aimed to assess geochemical biomarkers and metals in sediments from three streams crossing Manaus, a Brazilian city of 2.1 million inhabitants located in the heart of the Amazon rainforest. The Mindu and Quarenta streams criss-cross the urban area of Manaus and receive domestic effluents from many heavily populated districts. In addition, the Quarenta stream is subjected to effluents from the industrial district of Manaus. The Tarumã-Açu stream is mostly covered by vegetation, although the region presents some occurrence of family farming, floating petrol station, marinas, and floating restaurants and bars. n-Alkanes were determined by Gas Chromatography with Flame Ionization Detection (GC-FID), whereas hopanes and polycyclic aromatic hydrocarbons (PAHs) were determined by Gas Chromatography coupled to Mass Spectrometry (GC-MS). The metals Ag, Cd, Cr, Co, Cu, Mn, Ni, Pb, and Zn were determined by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) after microwave-assisted acid digestion. Concentrations of total PAHs and metals were higher in sediments from the urban streams Mindu and Quarenta because of the occurrence of more intense and diverse sources of pollution. In addition, some sediment samples from both these streams presented concentrations of fluoranthene, phenanthrene, and metals higher than the limits of low probability of adverse effects on biota established by the international guideline and by the Brazilian legislation. A similar total n-alkane concentration for sediments from all streams associated with profiles of n-alkanes with no odd/even hydrocarbon predominance suggests that biomass burning is an important source of hydrocarbons. Petroleum-derived products also represented a source for n-alkanes, as confirmed by the presence of α,β-hopanes, including an α,β-homohopane series from C31 to C35 with the presence of both 22S and 22R epimers. This is the first report on n-alkanes, PAHs, and hopanes in sediments from the Mindu, Quarenta, and Tarumã-Açu streams. The concentrations reported herein may be considered as baseline data in future monitoring programs of these streams.

Influence of Local Variables and Landscape Metrics on Gerromorpha (Insecta: Heteroptera) Assemblages in Savanna Streams, Brazil

Aquatic systems have been degraded by environmental changes aimed at increasing the productivity of farmland and ranches. These changes affect aquatic assemblages at both local and regional scales. The hypothesis of this study is that in-stream environmental conditions are more important determinants of species richness and composition of Gerromorpha assemblage, given that they are affected directly by changes that occur within the stream, rather than by landscape conditions. To test our hypothesis, we collected at 20 sites of agricultural and forested regions in the Brazilian Cerrado. We relate predictors of the landscape and sites, of the streams with the assemblages of Heteroptera. While landscape metrics play an important role in the formation of stream conditions, local and physico-chemical variables had a significant influence on the structure of the Gerromorpha assemblages in the study area. This indicates that these organisms are more dependent on the processes that occur within the stream than those that occur outside the area of the gallery forest, considering the spatial scale of this study.

An integrative approach to identify the impacts of multiple metal contamination sources on the Eastern Andean foothills of the Ecuadorian Amazonia

Currently, several concerns have been raised over metal contamination in the upper Amazon basin. Rivers that flow from the high Andes to the lowland Amazon are threatened by anthropogenic activities, which may, in turn, lead to increased metal concentrations in both water and sediments. In the present study, the impacts of multiple metal contamination sources in these ecosystems were identified. The degree of metal contamination was assessed in water and sediment and seed phytotoxicity analyses were carried out in samples taken from 14 sites located in upper Napo River tributaries, combining geochemical and ecotoxicological techniques. These tributaries were chosen based on their degree of anthropogenic contamination and proximity to known sources of relevant pollution, such as small-scale gold mining (MI), urban pollution (UP), fish farming (FF) and non-functional municipal landfill areas (LF). Our results suggest that anthropogenic activities are introducing metals to the aquatic ecosystem, as some metals were up to 500 times above the maximum permissible limits for the preservation of aquatic life established by Ecuadorian and North American guidelines. Sites located close to small-scale gold mining and sanitary landfills presented 100 to 1000 times higher concentrations than sites classified as "few threats". In water, Cd, Pb, Cu, Zn and Hg were mostly above the maximum permissible limits in the samples, while Cd in sediment reached concentrations 5-fold above the probable effect level (PEL). Phytotoxicity was associated through the diffuse contamination present in urban and landfill areas. Overall, metal concentrations and phytotoxicity assessments suggest anthropogenic effects to environmental contamination, even though natural sources cannot be disregarded. Anthropogenic effects in the eastern Andean Rivers need to be constantly monitored in order to build a complete picture on how pollution sources may affect this strategic Amazon basin area.

Arsenic and Trace Metals in Three West African rivers: Concentrations, Partitioning, and Distribution in Particle-Size Fractions

Despite increasing mining activities, and fertilizer and pesticide use in agriculture, little information is available on the status of metal(loid) contamination in rivers in West Africa. Sixty water samples were collected from three significant rivers (the Bandama, Comoé, and Bia Rivers) in Côte d'Ivoire, the world's top cocoa producer, to examine As, Pb, Cu, Fe, Cd, and Zn concentrations, partitioning, and distribution in suspended particle-size fractions. The results showed higher total metal(loid) concentrations during the dry and flood seasons than during the rainy season. Significant As and Pb concentrations, moderate Cu and Fe concentrations, and low Zn concentrations were observed during the flood season. The metal(loid) concentrations decreased upstream to downstream primarily due to increased deposition through flocculation. Inverse or no obvious spatial trends often were observed, indicative of local contamination from anthropogenic activities. The suspended solid phase and the strength of metal affinity to the particles controlled the metal(loid) concentrations. Furthermore, total metal(loid) concentrations increased significantly with decreasing suspended particle-size fractions. The results underline that As and Pb contents in the Comoé and Bia Rivers threaten the health of at least 3 million people in southeastern Côte d'Ivoire. Filtering river waters before use will significantly reduce human health risks.

Simultaneous Speciation Analysis of Trace Heavy Metals (Cu, Pb, Cd and Zn) in Seawater from Sishili Bay, North Yellow Sea, China

Different species of trace heavy metals (HMs) in seawater samples were simultaneously analyzed by anodic stripping voltammetric method, an analytical technique that does not require sample pre-concentration or the addition of reagents. The effects of the crucial parameters, deposition potential and time, on the determination of HMs were investigated. Concentrations of the total dissolved, dissolved active, and dissolved inert HMs were obtained through different analysis processes. The three species of Cu, Pb, Cd and Zn in seawater samples collected in different locations across Sishili Bay, North Yellow Sea, China were studied. The relative concentration of the dissolved active Cu, Pb, Cd and Zn in the total dissolved concentrations is 59.0%, 69.6%, 87.3% and 84.1%, respectively. The concentrations of different HMs species in Sishili Bay could be affected by the discharged effluent, sea current, and uptake of marine organism.

Metal contamination in a riparian wetland: Distribution, fractionation and plant uptake

Heavy metal pollution in aquatic system is of concern due its ecologic risk. In this study, we investigated the distribution, fractionation and plant uptake of heavy metals (As, Cd, Cr, Co, Cu, Ni, Pb and Zn) in a riparian wetland impacted by mining activities in Yunnan, southwest China. The results showed that excluding Cr, metal contents in sediment were higher than the background values, especially for As, which was 100-fold higher. While Cd showed high levels in the acid-soluble fraction with high availability, As, Cr, Cu, Ni and Pb mainly existed in the residual fraction with low availability. Two native aquatic plants including Phragmites australis (common reed) and Typha orientalis (bullrush) showed different uptake ability. T. orientalis accumulated more As, while P. australis accumulated more other metals. Based on geoaccumulation index (I_geo), As, Cd and Zn were more contaminated (I_geo> 3), followed by Cu, Pb and Co (I_geo<3), with Cr and Ni being slightly polluted (I_geo<1). According to risk assessment code, Cd showed high availability, followed by Zn and Co, with As exhibiting the lowest. The data suggested that both total and bioavailable metals should be considered for risk assessment of metal pollution in a wetland.

Effect of Fe (II) in low-nitrogen sewage on the reactor performance and microbial community of an ANAMMOX biofilter

In this study, the effect of Fe (II) on Anaerobic Ammonium Oxidation (ANAMMOX) process was investigated by step-wise increasing the Fe (II) in influent from 1 to 50 mg L^-1. The nitrogen removal, biofilm property and the microbial community were analyzed in each phase. Results showed that, the anaerobic ammonia-oxidizing bacteria (AAOB) bioactivity and the nitrogen removal of ANAMMOX system were slightly improved to 0.58 from the initial 0.51 kg m^-3 d^-1 by Fe (II) in 1-5 mg L^-1. The nitrogen removal was suppressed and could recover to the initial level during the same period under 10-20 mg L^-1 Fe (II), while it did not recover to the initial level under 30 mg L^-1 Fe (II) and showed no recovery performance under 50 mg L^-1 Fe (II). The irreversible suppression threshold of Fe (II) was calculated as 50 mg L^-1. The iron content in ANAMMOX biofilm presented linear correlation with the influent Fe (II) in 1-20 mg L^-1, which then tended to be stable when Fe (II) was higher. Dehydrogenase activity (DHA) showed similar and faster response to Fe (II) than the microbial activity, and it was an effective pre-indicator for the nitrogen removal performance in the ANAMMOX system suffered Fe (II). The Fe (II) feeding firstly led to the relative abundance of AAOB decreased to 11.04% from the initial 35.46%, and finally picked up to 19.39% after the long-term acclimatization.