Artisanal mining of monazite and cassiterite in the Amazon: Potential risks of rare earth elements for the environment and human health.

Artisanal mining is intensely carried out in developing countries, including Brazil and especially in the Amazon. This method of mineral exploration generally does not employ mitigation techniques for potential damages and can lead to various environmental problems and risks to human health. The objectives of this study were to quantify the concentrations of rare earth elements (REEs) and estimate the environmental and human health risks in cassiterite and monazite artisanal mining areas in the southeastern Amazon, as well as to understand the dynamics of this risk over time after exploitation. A total of 35 samples of wastes classified as overburden and tailings in active areas, as well as in areas deactivated for one and ten years were collected. Samples were also collected in a forest area considered as a reference site. The concentrations of REEs were quantified using alkaline fusion and ICP-MS. The results were used to calculate pollution indices and environmental and human health risks. REEs showed higher concentrations in anthropized areas. Pollution and environmental risk levels were higher in areas deactivated for one year, with considerable contamination factors for Gd and Sm and significant to extreme enrichment factors for Sc. Human health risks were low (< 1) in all studied areas. The results indicate that artisanal mining of cassiterite and monazite has the potential to promote contamination and enrichment by REEs.

Assessment of the reproduction of six collembolan species in tropical soils naturally rich in potentially toxic elements.

Laboratory ecotoxicological tests are important tools for the management of environmental changes derived from anthropogenic activities. Folsomia candida is usually the model species used in some procedures. However, this species may not be sufficiently representative of the sensitivity of the other collembolan species. This study aimed to evaluate (i) the effects of soils naturally rich in potentially toxic elements (PTE) and soil characteristics on the reproduction and survival of different collembolan species, (ii) whether the habitat function of these soils is compromised, and (iii) to what extent F. candida is representative of the other collembolan species. For this, reproduction tests with six collembolan species were conducted in 14 different samples of soils. In general, collembolan reproduction was not completely inhibited in none of the natural tested soils. Even soils with high pollution load index values did not negatively affect collembolan reproduction for most of the species. In contrast, the lowest collembolan reproduction rates were found in a visually dense soil (lowest volume/weight ratio), highlighting that soil attributes other than total PTE concentration also interfere in the reproduction of collembolans. Our results support the idea that the F. candida species might not be representative of other collembolan species and that laboratory tests to assess soil contaminations should be conducted using diverse collembolan species.

Clean and accurate soil quality monitoring in mining areas under environmental rehabilitation in the Eastern Brazilian Amazon.

Soil quality monitoring in mining rehabilitation areas is a crucial step to validate the effectiveness of the adopted recovery strategy, especially in critical areas for environmental conservation, such as the Brazilian Amazon. The use of portable X-ray fluorescence (pXRF) spectrometry allows a rapid quantification of several soil chemical elements, with low cost and without residue generation, being an alternative for clean and accurate environmental monitoring. Thus, this work aimed to assess soil quality in mining areas with different stages of environmental rehabilitation based on predictions of soil fertility properties through pXRF along with four machine learning algorithms (projection pursuit regression, PPR; support vector machine, SVM; cubist regression, CR; and random forest, RF) in the Eastern Brazilian Amazon. Sandstone and iron mines in different chronological stages of rehabilitation (initial, intermediate, and advanced) were evaluated, in addition to non-rehabilitated and native forest areas. A total of 81 soil samples (26 from sandstone mine and 55 from iron mine) were analyzed by both traditional wet-chemistry methods and pXRF. The available/exchangeable contents of K, Ca, B, Fe, and Al, in addition to H+Al, cation exchange capacity at pH = 7, Al saturation, soil organic matter, pH, sum of bases, base saturation, clay, and sand were accurately predicted (R2 > 0.70) using pXRF data, with emphasis on the prediction of Fe (R2 = 0.93), clay content (R2 = 0.81), H+Al (R2 = 0.81), and K+ (R2 = 0.85). The best predictive models were developed by RF and CR (86%) and when considering pXRF data + mining area + stage of rehabilitation (73%). The results highlight the potential of pXRF to accurately assess soil properties in environmental rehabilitation areas in the Amazon region (yet scarcely evaluated under this approach), promoting a more agile and cheaper preliminary diagnosis compared to traditional methods.

Exogenous Nitric Oxide Alleviates Water Deficit and Increases the Seed Production of an Endemic Amazonian Canga Grass.

Open pit mining can cause loss in different ecosystems, including damage to habitats of rare and endemic species. Understanding the biology of these species is fundamental for their conservation, and to assist in decision-making. Sporobolus multiramosus is an annual grass endemic to the Amazon canga ecosystems, which comprise rocky outcrop vegetation covering one of the world's largest iron ore reserves. Here, we evaluated whether nitric oxide aids S. multiramosus in coping with water shortages and examined the physiological processes behind these adaptations. nitric oxide application improved the water status, photosynthetic efficiency, biomass production, and seed production and germination of S. multiramosus under water deficit conditions. These enhancements were accompanied by adjustments in leaf and root anatomy, including changes in stomata density and size and root endodermis thickness and vascular cylinder diameter. Proteomic analysis revealed that nitric oxide promoted the activation of several proteins involved in the response to environmental stress and flower and fruit development. Overall, the results suggest that exogenous nitric oxide has the potential to enhance the growth and productivity of S. multiramosus. Enhancements in seed productivity have significant implications for conservation initiatives and can be applied to seed production areas, particularly for the restoration of native ecosystems.

Human and environmental exposure to rare earth elements in gold mining areas in the northeastern Amazon.

Rudimentary methods are used to exploit gold (Au) in several artisanal mines in the Amazon, producing hazardous wastes that may pose risks of contamination by rare earth elements (REEs). The objectives of this study were to quantify the concentrations of REEs and assess their environmental and human health risks in artisanal Au mining areas in the northeastern Amazon. Thus, 25 samples of soils and mining wastes were collected in underground, colluvial, and cyanidation exploration sites, as well as in a natural forest that was considered as a reference area. The concentrations of REEs were quantified using alkaline fusion and inductively coupled plasma mass spectrometry, and the results were used to estimate pollution indices and risks associated with the contaminants. All REEs showed higher concentrations in waste deposition areas than in the reference area, especially Ce, Sc, Nd, La, Pr, Sm, and Eu. Pollution and enrichment levels were higher in the underground and cyanidation mining areas, with very high contamination factors (6.2-27) for Ce, Eu, La, Nd, Pr, Sm, and Sc, and significant to very high enrichment factors (5.5-20) for Ce, La, Nd, Pr, and Sc. The ecological risk indices varied from moderate (167.3) to high (365.7) in the most polluted sites, but risks to human health were low in all areas studied. The results of this study indicate that artisanal Au mining has the potential to cause contamination, enrichment, and ecological risks by REEs in the northeastern Amazon. Mitigation measures should be implemented to protect the environment from the negative impacts of these contaminants.

Mercury in multimedia system of Itacaiúnas Basin, Brazilian Amazon: An integrated approach to understand its distribution, origin, and ecological risk.

This study presents the first integrated study on total Hg (THg) level in surface soil (SS), bottom soil (BS), stream sediments (SD), lake sediments (LS), stream water (SW), and lake water (LW) of Itacaiúnas River Watershed (IRW), Brazil to investigate the source and distribution of Hg in different environmental media considering contrasts of geological domains and sub-basins and its potential ecological and human risk. Hg content in most of the soils and sediments were above the upper crustal average values (56 µg/kg), however, when compared to the legal limits set by the Resolution CONAMA (Conselho Nacional de Meio Ambiente: soil 500 µg/kg; sediment 486 µg/kg), only 1 soil sample from Parauapebas sub-basin and 4 sediment samples from Violão Lake exceeded the limit. None of the SW and LW samples (<0.2 µg/L; CONAMA limit for Class II freshwater) are markedly contaminated by Hg. The SS and BS show similar contents and spatial distribution of Hg with higher contents being registered mostly in the Itacaiúnas and Parauapebas sub-basins, which are closely correlated with SD. This suggests that Hg levels are largely of geogenic origin and anthropogenic effect is highly limited. Principal Component Analysis (PCA) results show that Hg is strongly associated with total organic carbon (TOC), loss on ignition (LOI), and SO3, indicating organic matter as the main factor controlling the distribution of Hg and this is the major cause of accentuated Hg enrichment in lake sediments. The ecological risk index revealed a low pollution risk for most of the solid samples, except 11% LS and <1.5% SS and SD samples, which registered moderate risk. Health risk assessment indicated no adverse non-carcinogenic health effect on either adults and children in terms of Hg contamination. This information will be useful for Hg risk assessment in the Carajás region and future environmental research in this direction in the Amazonia.

Rock n' Seeds: A database of seed functional traits and germination experiments from Brazilian rock outcrop vegetation.

Advancing functional ecology depends fundamentally on the availability of data on reproductive traits, including those from tropical plants, which have been historically underrepresented in global trait databases. Although some valuable databases have been created recently, they are mainly restricted to temperate areas and vegetative traits such as leaf and wood traits. Here, we present Rock n' Seeds, a database of seed functional traits and germination experiments from Brazilian rock outcrop vegetation, recognized as outstanding centers of diversity and endemism. Data were compiled through a systematic literature search, resulting in 103 publications from which seed functional traits were extracted. The database includes information on 16 functional traits for 383 taxa from 148 genera, 50 families, and 25 orders. These 16 traits include two dispersal, six production, four morphological, two biophysical, and two germination traits-the major axes of the seed ecological spectrum. The database also provides raw data for 48 germination experiments, for a total of 10,187 records for 281 taxa. Germination experiments in the database assessed the effect of a wide range of abiotic and biotic factors on germination and different dormancy-breaking treatments. Notably, 8255 of these records include daily germination counts. This input will facilitate synthesizing germination data and using this database for a myriad of ecological questions. Given the variety of seed traits and the extensive germination information made available by this database, we expect it to be a valuable resource advancing comparative functional ecology and guiding seed-based restoration and biodiversity conservation in tropical megadiverse ecosystems. There are no copyright restrictions on the data; please cite this paper when using the current data in publications; also the authors would appreciate notification of how the data are used in publications.

O avanço da ecologia funcional depende fundamentalmente da disponibilidade de dados sobre traços reprodutivos, incluindo dados de plantas tropicais, que têm sido historicamente subrepresentados em bancos de dados de traços funcionais globais. Embora alguns bancos de dados valiosos tenham sido criados recentemente, eles são restritos principalmente a áreas temperadas e a traços vegetativos, como traços de folhas e madeira. Neste artigo apresentamos Rock n' Seeds, um banco de dados de traços funcionais de sementes e experimentos de germinação de vegetações associadas a afloramentos rochosos do Brasil, os quais são reconhecidos como centros notáveis de diversidade e endemismo. Os dados foram compilados através de uma revisão sistemática na literatura, resultando em 103 publicações das quais foram extraídos os traços funcionais das sementes. O banco de dados inclui informações de 16 traços funcionais para 383 taxa de 148 gêneros, 50 famílias e 25 ordens. Estes dezesseis traços incluem dois traços de dispersão, seis de produção, quatro morfológicos, dois biofísicos e dois germinativos; os eixos principais do espectro ecológico da semente. O banco de dados também fornece os dados brutos para 48 experimentos de germinação para um total de 10.187 registros para 281 taxa. Os experimentos de germinação no banco de dados avaliaram o efeito de uma ampla gama de fatores abióticos e bióticos sobre a germinação e diferentes tratamentos de quebra de dormência. Particularmente, 8.255 desses registros incluem a contagem diária da germinação. Estas informações facilitarão a síntese de dados de germinação e a utilização deste banco de dados para uma grande variedade de questões ecológicas. Dada a variedade de traços das sementes e as amplas informações sobre germinação disponibilizadas por este banco de dados, esperamos que ele seja um recurso valioso para o avanço da ecologia funcional comparativa e para orientar a restauração baseada em sementes e a conservação da biodiversidade em ecossistemas tropicais megadiversos. Não há restrições de direitos autorais sobre os dados; favor citar este artigo ao utilizar os dados nas publicações e os autores agradeceriam uma notificação de como os dados são utilizados nas publicações.

El avance de la ecología funcional depende fundamentalmente de la disponibilidad de datos sobre rasgos reproductivos-incluyendo los de las plantas tropicales-los cuales han estado poco representados en las bases de datos globales de rasgos. Aunque recientemente se han creado algunas bases de datos valiosas, estas se encuentran restringidas principalmente a las zonas templadas y a los rasgos vegetativos, como los de las hojas y la madera. En este artículo presentamos Rock n' Seeds, una base de datos de rasgos funcionales de semillas y experimentos de germinación de la vegetación asociada a afloramientos rocosos de Brasil, los cuales son destacados centros de diversidad y endemismo. Los datos se recopilaron mediante una búsqueda bibliográfica sistemática, que dio como resultado 103 publicaciones de las que se extrajeron los rasgos funcionales de las semillas. La base de datos incluye información de dieciséis rasgos funcionales para 383 taxones de 148 géneros, 50 familias y 25 órdenes. Estos rasgos incluyen dos rasgos de dispersión, seis de producción, cuatro morfológicos, dos biofísicos y dos de germinación; siendo estos los principales ejes del espectro ecológico de las semillas. La base de datos también proporciona los datos brutos de 48 experimentos de germinación, para un total de 10.187 registros de 281 taxones. Dichos experimentos de germinación evaluaron el efecto de una amplia gama de factores abióticos y bióticos sobre la germinación y de diferentes tratamientos para romper la dormancia. En particular, 8.255 de estos registros cuentan con conteos diarios de germinación. Esto facilitará la síntesis de los datos de germinación y el uso de esta base de datos para una gran diversidad de preguntas ecológicas. Dada la variedad de rasgos de las semillas y la amplia información sobre germinación que ofrece esta base de datos, esperamos que sea un recurso valioso para el avance de la ecología funcional comparativa y para orientar la restauración basada en semillas y la conservación de la biodiversidad en ecosistemas tropicales megadiversos. No hay restricciones de derechos de autor sobre los datos; se solicita citar este documento cuando se utilicen los datos en publicaciones y los autores agradecerán ser notificados sobre cómo se utilizan los datos en las publicaciones.

Molecular Mechanisms Underlying Mimosa acutistipula Success in Amazonian Rehabilitating Minelands.

Mimosa acutistipula is endemic to Brazil and grows in ferruginous outcrops (canga) in Serra dos Carajás, eastern Amazon, where one of the largest iron ore deposits in the world is located. Plants that develop in these ecosystems are subject to severe environmental conditions and must have adaptive mechanisms to grow and thrive in cangas. Mimosa acutistipula is a native species used to restore biodiversity in post-mining areas in canga. Understanding the molecular mechanisms involved in the adaptation of M. acutistipula in canga is essential to deduce the ability of native species to adapt to possible stressors in rehabilitating minelands over time. In this study, the root proteomic profiles of M. acutistipula grown in a native canga ecosystem and rehabilitating minelands were compared to identify essential proteins involved in the adaptation of this species in its native environment and that should enable its establishment in rehabilitating minelands. The results showed differentially abundant proteins, where 436 proteins with significant values (p < 0.05) and fold change ≥ 2 were more abundant in canga and 145 in roots from the rehabilitating minelands. Among them, a representative amount and diversity of proteins were related to responses to water deficit, heat, and responses to metal ions. Other identified proteins are involved in biocontrol activity against phytopathogens and symbiosis. This research provides insights into proteins involved in M. acutistipula responses to environmental stimuli, suggesting critical mechanisms to support the establishment of native canga plants in rehabilitating minelands over time.

Proteomic Profiling and Rhizosphere-Associated Microbial Communities Reveal Adaptive Mechanisms of Dioclea apurensis Kunth in Eastern Amazon's Rehabilitating Minelands.

Dioclea apurensis Kunth is native to ferruginous rocky outcrops (known as canga) in the eastern Amazon. Native cangas are considered hotspots of biological diversity and have one of the largest iron ore deposits in the world. There, D. apurensis can grow in post-mining areas where molecular mechanisms and rhizospheric interactions with soil microorganisms are expected to contribute to their establishment in rehabilitating minelands (RM). In this study, we compare the root proteomic profile and rhizosphere-associated bacterial and fungal communities of D. apurensis growing in canga and RM to characterize the main mechanisms that allow the growth and establishment in post-mining areas. The results showed that proteins involved in response to oxidative stress, drought, excess of iron, and phosphorus deficiency showed higher levels in canga and, therefore, helped explain its high establishment rates in RM. Rhizospheric selectivity of microorganisms was more evident in canga. The microbial community structure was mostly different between the two habitats, denoting that despite having its preferences, D. apurensis can associate with beneficial soil microorganisms without specificity. Therefore, its good performance in RM can also be improved or attributed to its ability to cope with beneficial soil-borne microorganisms. Native plants with such adaptations must be used to enhance the rehabilitation process.

Biochar mitigates bioavailability and environmental risks of arsenic in gold mining tailings from the eastern Amazon.

Artisanal gold mining has generated tailings highly contaminated by arsenic (As) in Cachoeira do Piriá, eastern Amazon, leading to severe risks to the environment. Such risks should be mitigated considering the bioavailable concentration of the element, since it implies immediate damage to the ecosystem. The objective of this study was to evaluate the potential of biochars in mitigating the environmental risks of bioavailable As concentrations in gold mining tailings from underground and cyanidation exploration. The biochar addition increased mineral components, cation retention, phosphorus in all fractions, and organic and inorganic carbon. The bioavailability of As was reduced after adding the biochars, following the order palm kernel cake biochar > Brazil nut shell biochar > açaí seed biochar, with reductions of up to 13 mg kg-1 in the underground mining tailings and 17 mg kg-1 in the cyanidation mining tailings. These results contributed to the statistically significant reduction of the environmental risks in both mining tailings (6-17% in the underground mining tailings and 9-20% in the cyanidation mining tailings), which was emphasized by Pearson's correlation and multivariate analyzes. The incorporation of the bioavailable fractions of As (from sequential extraction) in the environmental risk assessment was a promising method for evaluating the efficiency of biochars in mitigating the damage caused by this metalloid in gold mining tailings.

Levels and environmental risks of rare earth elements in a gold mining area in the Amazon.

Artisanal gold (Au) mining may have increased the concentrations of rare earth elements (REEs) in the Serra Pelada mine (southeastern Amazon, Brazil), which has not been evaluated so far. The objectives of this study were to determine the concentrations of cerium (Ce), lanthanum (La), scandium (Sc), and yttrium (Y) in the surroundings of the Serra Pelada mine, as well as the environmental risks associated with these elements. Therefore, 27 samples were collected in agricultural, forest, mining, and urban areas, and submitted to chemical and particle size characterization. The concentrations of REEs were quantified by inductively coupled plasma mass spectrometry (ICP-MS) and used to estimate pollution indices and environmental risks of the studied elements. All REEs had higher levels in the anthropized areas when compared to the forest area, except Sc in the mining and urban areas. Pollution load indices revealed that all areas are contaminated (>1) by the combined effect of REEs, especially the agricultural areas (index of 2.3). The element of greatest enrichment in the studied areas was Y, with enrichment factors of 18.2, 39.0, and 44.4 in the urban, agriculture, and mining areas, respectively. However, the potential ecological risk indices were low (<150) in all areas, indicating that there are no current environmental risks by the studied REEs.

Soil-sediment linkage and trace element contamination in forested/deforested areas of the Itacaiúnas River Watershed, Brazil: To what extent land-use change plays a role?

Trace elements (TE) contamination in forested areas of the Itacaiúnas River Watershed (IRW), Brazilian Amazon, arouses growing interest owing to the rapid deforestation and mining activities. In this study, soils (surface, SS; bottom, BS) and stream sediments (SD) from forested/deforested areas of IRW were analyzed with the aim of (1) evaluating the major sources of TE (mainly As, Ba, Cd, Cu, Co, Cr, Hg, Mo, Mn, Ni, Pb, V, and Zn), and (2) examining the soil-sediment TE link related to land-use change and/or geologic factors. Compositional data analysis (CoDA) was used to eliminate data closure issues and the centred log-ratio (clr) transformation yielded better results in Principal Component Analysis (PCA). The TE distribution pattern was significantly different (p < 0.05) between forested and deforested areas, but in both areas the TE distribution pattern is significantly correlated between SS, BS, and SD, indicating a strong lithogenic control. PCA (clr-transformed) identified the major geochemical bedrock signature as Fe-Ti-V-Cu-Cr-Ni, which is nearly similar in soil and sediments. The more accentuated enrichment and the maximum number of anomalies of these elements were found in the Carajás Basin and are highly coincident with mineral deposits/local lithologies without clear indication of anthropogenic contamination from point sources. Besides geogenic factors, deforestation is also affecting TE distribution in the basin. In deforested areas, Mn was significantly enriched in the surface horizon. Furthermore, linear regression analysis shows stronger TE relationships between soils and sediments in deforested areas than in forested ones, reflecting higher erosion in the former. This could be the reason for the relatively higher enrichment of TE (e.g., Fe, Mn, Cu, Cr, Ni) in deforested sediments. The TE contamination using regional background values provides more accurate results than worldwide reference values. Thus, the former should be considered for a more realistic environmental risk assessment in IRW and other forest ecosystems in the Brazilian Amazon.

Copper mining in the eastern Amazon: an environmental perspective on potentially toxic elements.

Mining activity is of great economic and social importance; however, volumes of metallic ore tailings rich in potentially toxic elements (PTEs) may be produced. In this context, managing this environmental liability and assessing soil quality in areas close to mining activities are fundamental. This study aimed to compare the concentrations of PTEs-arsenic (As), barium (Ba), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), mercury (Hg), molybdenum (Mo), nickel (Ni), lead (Pb) and zinc (Zn)-as well as the fertility and texture of Cu tailings and soils of native, urban and pasture areas surrounding a Cu mining complex in the eastern Amazon. The levels of PTEs were compared with soil prevention values, soil quality reference values, global average soil concentrations and average upper continental crust concentrations. The contamination factor (CF), degree of contamination (Cdeg), potential ecological risk index (RI), geoaccumulation index (Igeo) and pollution load index (PLI) were calculated. The levels of Co, Cu and Ni in the tailings area exceeded the prevention values, soil quality reference values and average upper continental crust concentrations; however, the tailings area was considered unpolluted according to PLI and RI and presented a low potential ecological risk. The high concentrations of PTEs are associated with the geological properties of the area, and the presence of PTEs-rich minerals supports these results. For the urban and pasture areas, none of the 11 PTEs analyzed exceeded the prevention values established by the Brazilian National Environment Council.

Impact of copper mining wastes in the Amazon: Properties and risks to environment and human health.

Improper disposal of copper mining wastes can threaten the ecosystem and human health due to the high levels of potentially toxic elements released into the environment. The objective of this study was to determine the properties of Cu mining wastes generated in the eastern Amazon and their potential risks to environment and human health. Samples of forest soil and artisanal/industrial Cu mining wastes were collected and subjected to characterization of properties and pseudo-total concentrations of Al, As, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, and Zn, in addition to chemical fractionation of Cu. The pH ranged from near neutrality to alkaline. Pseudo-total concentrations of Cu were high in all wastes, mainly in the artisanal rock waste, with 19,034 mg kg-1, of which 61% is concentrated in the most reactive fractions. Pollution indices indicated that the wastes are highly contaminated by Cu and moderately contaminated by Cr and Ni. However, only the artisanal rock waste is associated with environmental risk. Non-carcinogenic and carcinogenic human health risks were detected, especially from exposure to Cr in the artisanal rock waste. Prevention actions and monitoring of the artisanal mining area are necessary to avoid impacts to the local population.

Artisanal gold mining in the eastern Amazon: Environmental and human health risks of mercury from different mining methods.

Artisanal gold (Au) mining is the activity with the highest consumption of mercury (Hg) and the main source of environmental contamination by this element, which is a recurring problem in the Amazon. In this study, contamination and risks caused by Hg to the environment and human health were evaluated in different forms of artisanal Au mining in the Brazilian Amazon. For this purpose, 25 samples of soils and tailings were collected in three types of artisanal mine and one native forest. The mineralogical analysis revealed that there is no occurrence of minerals constituted by Hg. However, the concentrations of Hg in underground mining tailings were very high and exceeded the prevention values established by Brazilian environmental legislation, indicating elevated risk to the ecosystem and human health. The enrichment factor indicated that underground mining tailings are enriched by Hg, submitted to cyanidation or not, suggesting anthropogenic source for the high concentrations of Hg. The geoaccumulation index and the contamination factor showed that the colluvial mining tailings are moderately contaminated, and the tailings from underground mining are highly to extremely contaminated, leading to very high risks to the environment and the health of children from the region. These results represent a great contribution to the Amazon, since they provide subsidies for the definition of policies to mitigate environmental contamination and associated risks.

Bioavailability of copper and nickel in naturally metal-enriched soils of Carajás Mining Province, Eastern Amazon, Brazil.

Naturally elevated contents of copper (Cu) and nickel (Ni) are found in soils worldwide, and their potential toxicity is better understood when geochemical reactive fractions are identified and monitored. Thus, this study aimed to assess the bioavailability of Cu and Ni and estimate environmental risks in naturally metal-enriched soils of Carajás Mining Province, Eastern Amazon, Brazil. For that, 58 surficial soil samples were analyzed for their extractable contents of Cu and Ni by Mehlich 1. Next, 13 soil samples were selected for additional single and sequential extractions, for the determination of metal content in the shoots of grasses naturally growing in these soils and for calculating the risk assessment code. Despite the naturally high total concentrations, the contents of easily available Cu and Ni are a minor fraction of total concentrations (up to 10.15%), and the reducible oxide and residual pools hold the major proportion of total content of metals. This contributed to low bioavailability, low environmental risk, and also to low concentrations of these metals on grasses collected in the field. Soil organic matter, Fe2O3, Al2O3 and clay content have a dominant role in metals retention on studied soils. Our findings on the bioavailability of Cu and Ni in a region of great economic relevance for Brazil are important not only for predicting the elements' behavior in the soil-plant system but also for refining risk assessments and to provide useful data for environmental quality monitoring.

Environmental and human health risks of arsenic in gold mining areas in the eastern Amazon.

Knowledge of arsenic (As) levels in gold (Au) mining areas in the Amazon is critical for determining environmental risks and the health of the local population, mainly because this region has the largest mineral potential in Brazil and one of the largest in the world. The objective of this study was to assess the environmental and human health risks of As in tailings from Au exploration in the eastern Amazon. Samples were collected from soils and tailings from different exploration forms from 25 points, and the total concentration, pollution indexes and human health risk were determined. Concentrations of As were very high in all exploration areas, especially in tailings, whose maximum value reached 10,000 mg kg-1, far above the investigation value established by the Brazilian National Council of the Environment, characterizing a polluted area with high environmental risk. Exposure based on the daily intake of As demonstrated a high health risk for children and adults, whose non-carcinogenic risk indexes of 17.8, extremely above the acceptable limit (1.0) established by the United States Environmental Protection Agency. High levels of As in reactive fractions in underground, cyanidation, and colluvium mining areas, as well as extremely high gastric and intestinal bioaccessibility were found, suggesting that high levels may be absorbed by the local population. The results show that the study area is highly polluted through Au mining activities, putting the environment and population health at risk, and that there is an urgent need for intervention by the environmental control agencies for remediation.

Phosphorus lability increases with the rehabilitation advance of iron mine land in the eastern Amazon.

Impacted areas by iron mining may face challenges in the management of phosphate fertilization and reduced efficiency of rehabilitation practices, thus extending the time required for the rehabilitation of these areas. The objective of this study was to evaluate phosphorus (P) lability in soils of native forest and ferriferous canga areas (savanna vegetation above ironstone outcrops covering iron ore deposits) and in iron mine waste piles undergoing rehabilitation. Benches of the analysed waste pile differ in age of rehabilitation: as the initial rehabilitation stage (INI), we consider benches with fewer than 3 years of rehabilitation; the intermediate stage (INT) were benches with up to 5 years of rehabilitation; and the advanced rehabilitation stage (ADV) corresponds to benches with more than 8 years of rehabilitation activities. Organic and inorganic P fractions were analysed in these areas by chemical fractionation and were classified according to the degree of soil lability. The results show that in the canga environment, there was a predominance of inorganic fractions of moderate lability and moderate stability, with a strong dependency of the soil organic matter (SOM) on the P fractions, whereas there was a greater participation of the moderately labile organic fractions in the forest than in the canga. On the other hand, in the rehabilitation areas, there was an increase in the labile organic and inorganic fractions as the rehabilitation process advanced. The distribution of P in areas undergoing rehabilitation indicates that there is a tendency for P levels to resemble those of native environments, such as the forests.

Integrating environmental variables by multivariate ordination enables the reliable estimation of mineland rehabilitation status.

Despite the wide variety of variables commonly employed to measure the success of rehabilitation, the assessment and subsequent definition of indicators of environmental rehabilitation status are not simple tasks. The main challenges are comparing rehabilitated sites with target ecosystems as well as integrating individual environmental and eventually collinear variables into a single tractable measure for the state of a system before effective indicators that track rehabilitation may be modeled. Furthermore, a consensus is lacking regarding which and how many variables need to be surveyed for a reliable estimation of rehabilitation status. Here, we propose a multivariate ordination to integrate variables related to ecological processes, vegetation structure, and community diversity into a single estimation of rehabilitation status. As a case, we employed a curated set of 32 environmental variables retrieved from nonrevegetated, rehabilitating and reference sites associated with iron ore mines from the Urucum Massif, Mato Grosso do Sul, Brazil. By integrating this set of environmental variables into a single estimation of rehabilitation status, the proposed multivariate approach is straightforward and able to adequately address collinearity among variables. The proposed methodology allows for the identification of biases towards single variables, surveys or analyses, which is necessary to rank environmental variables regarding their importance to the assessment. Furthermore, we show that bootstrapping permitted the detection of the minimum number of environmental variables necessary to achieve reliable estimations of the rehabilitation status. Finally, we show that the proposed variable integration enables the definition of case-specific environmental indicators for more rapid assessments of mineland rehabilitation. Thus, the proposed multivariate ordination represents a powerful tool to facilitate the diagnosis of rehabilitating sites worldwide provided that sufficient environmental variables related to ecological processes, diversity and vegetation structure are gathered from nonrehabilitated, rehabilitating and reference study sites. By identifying deviations from predicted rehabilitation trajectories and providing assessments for environmental agencies, this proposed multivariate ordination increases the effectiveness of (mineland) rehabilitation.

A metagenomic survey of soil microbial communities along a rehabilitation chronosequence after iron ore mining.

Microorganisms are useful environmental indicators, able to deliver essential insights to processes regarding mine land rehabilitation. To compare microbial communities from a chronosequence of mine land rehabilitation to pre-disturbance levels from references sites covered by native vegetation, we sampled non-rehabilitated, rehabilitating and reference study sites from the Urucum Massif, Southwestern Brazil. From each study site, three composed soil samples were collected for chemical, physical, and metagenomics analysis. We used a paired-end library sequencing technology (NextSeq 500 Illumina); the reads were assembled using MEGAHIT. Coding DNA sequences (CDS) were identified using Kaiju in combination with non-redundant NCBI BLAST reference sequences containing archaea, bacteria, and viruses. Additionally, a functional classification was performed by EMG v2.3.2. Here, we provide the raw data and assembly (reads and contigs), followed by initial functional and taxonomic analysis, as a base-line for further studies of this kind. Further investigation is needed to fully understand the mechanisms of environmental rehabilitation in tropical regions, inspiring further researchers to explore this collection for hypothesis testing.