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Rare earth elements (REEs) have been intentionally used in Chinese agriculture since the 1980s to improve crop yields. Around the world, REEs are also involuntarily applied to soils through phosphate fertilizers. These elements are known to alleviate damage in plants under abiotic stresses, yet there is no information on how these elements act in the physiology of plants. The REE mode of action falls within the scope of the hormesis effect, with low-dose stimulation and high-dose adverse reactions. This study aimed to verify how REEs affect rice plants' physiology to test the threshold dose at which REEs could act as biostimulants in these plants. In experiment 1, 0.411 kg ha−1 (foliar application) of a mixture of REE (containing 41.38% Ce, 23.95% La, 13.58% Pr, and 4.32% Nd) was applied, as well as two products containing 41.38% Ce and 23.95% La separately. The characteristics of chlorophyll a fluorescence, gas exchanges, SPAD index, and biomass (pot conditions) were evaluated. For experiment 2, increasing rates of the REE mix (0, 0.1, 0.225, 0.5, and 1 kg ha−1) (field conditions) were used to study their effect on rice grain yield and nutrient concentration of rice leaves. Adding REEs to plants increased biomass production (23% with Ce, 31% with La, and 63% with REE Mix application) due to improved photosynthetic rate (8% with Ce, 15% with La, and 27% with REE mix), favored by the higher electronic flow (photosynthetic electron transport chain) (increase of 17%) and by the higher Fv/Fm (increase of 14%) and quantum yield of photosystem II (increase of 20% with Ce and La, and 29% with REE Mix), as well as by increased stomatal conductance (increase of 36%) and SPAD index (increase of 10% with Ce, 12% with La, and 15% with REE mix). Moreover, adding REEs potentiated the photosynthetic process by increasing rice leaves' N, Mg, K, and Mn concentrations (24–46%). The dose for the higher rice grain yield (an increase of 113%) was estimated for the REE mix at 0.72 kg ha−1. [ABSTRACT FROM AUTHOR]

Apesar de a mineração de bauxita causar grandes alterações nas características do solo, com efeitos negativos nas micorrizas arbusculares, os efeitos da reabilitação de áreas mineradas sobre os fungos micorrízicos arbusculares (MA) e sua simbiose são pouco conhecidos. O objetivo deste trabalho foi avaliar a ocorrência, diversidade e eficiência dos fungos MA, em áreas de mineração de bauxita, com diferentes tipos de vegetação e idades de reabilitação. Amostras de solo da rizosfera foram coletadas para analisar o micélio fúngico extrarradicular, o número de esporos, a riqueza e diversidade de fungos MA e para avaliar a colonização micorrízica e eficiência simbiótica de populações fúngicas. A mineração afetou negativamente os fungos MA, sendo a recuperação destes mais relacionada com o tipo de vegetação do que com o tempo de reabilitação da área. Foram encontradas as espécies: Gigaspora margarita, Gigaspora sp., Paraglomus occultum, Glomus sp., Entrophospora colombiana e Acaulospora scrobiculata. A ocorrência desses fungos foi favorecida pela presença de gramíneas ede bracatinga. Embora Eucalyptus saligna não seja um bom hospedeiro para os fungos MA, quando associado a sub-bosque bem desenvolvido e diverso, contribuiu para a recuperação dos fungos. As populações fúngicas isoladas de áreas com braquiária e feijão-guandu ou de bracatinga com capim-gordura apresentaram elevada eficiência para o feijoeiro, mostrando que é possível recuperar a função deste grupo de microrganismos utilizando diferentes tipos de vegetação. Estes isolados apresentam potencial de utilização em programas de reabilitação de solos minerados.

O objetivo deste trabalho foi avaliar, em casa de vegetação, o comportamento de espécies herbáceas em relação ao excesso de Cd e Zn no solo. O gradiente de contaminação foi estabelecido a partir de mistura de solo contaminado com solo sem contaminação em diferentes proporções. As sementes foram semeadas em tubetes contendo 250 mL de solo, e após 90 dias as plantas foram colhidas e avaliadas. A maioria das espécies apresentou redução no crescimento com aumento da contaminação do solo e elevadas concentrações de Cd e Zn na matéria seca da parte aérea (MSPA), na mistura com 15% de solo contaminado. A espécie Pffafia sp. mostrou-se tolerante à contaminação, crescendo em misturas de solo contendo até 90 mg kg-1 de Cd e 1.450 mg kg-1 de zinco. Além disso, apresentou concentração superior a 100 mg kg-1 de Cd na MSPA, sendo considerada hiperacumuladora desse metal. Sida glaziovii, Bidens pilosa, Rhynchelytrum repens, Cenchrus echinatus e Nicandra physaloides, por sua vez, foram severamente afetadas pela contaminação, ao contrário de Trifolium repens, Euchlaena mexicana, Cynodon dactylon, Avena strigosa, Cenchrus ciliares e Cyperus sp. que apresentaram crescimento satisfatório. As espécies avaliadas mostram-se promissoras para estudos adicionais sobre a reabilitação de áreas contaminadas com metais pesados.

O efeito da aplicação de níquel sobre o teor de nutrientes na raiz, no caule e nas folhas de mudas de cedro (Cedrela fissilis Vell.) foi estudado em um experimento realizado em casa de vegetação do Departamento de Ciência do Solo da Universidade Federal de Lavras. As mudas foram cultivadas em solução nutritiva de Clark e submetidas a doses crescentes de Ni: 0, 42, 84, 169 e 252 mimol. O experimento foi conduzido em delineamento estatístico de blocos ao acaso, e após 60 dias de exposição ao metal pesado foram feitas avaliações do teor de macro e de micronutrientes na matéria seca de raiz, caule e folha. Os resultados mostraram que a aplicação de níquel aumentou o teor de P, praticamente não afetou o teor de K e de S, no entanto reduziu o teor de Ca e de Mg. Os teores de Cu, Fe e Mn, de modo geral, sofreram redução, ao passo que o teor de Zn foi pouco afetado. O teor de Ni, na matéria seca de raiz, caule e folha, elevou-se com o aumento das doses deste metal pesado, que mostrou ser móvel nas plantas analisadas.

To reduce the net losses of biodiversity and ecosystem services caused by iron ore mining in Brazil, mineland rehabilitation using native plant species is necessary. However, systematic knowledge about which plant species are the best candidates for mineland rehabilitation is lacking. Therefore, iron mining companies working on the Urucum Massif reintroduce as many native herb and shrub species as possible to achieve the rehabilitation of savanna vegetation communities. To this end, seeds are collected from nearby native ecosystems, and seedlings are rescued from logged areas or produced in a local nursery. Monitoring is necessary to assess the persistence of the reinstated communities and their similarity to natural reference conditions. Ideally, monitoring efforts should compare the floristic composition of the rehabilitating sites with that of natural reference ecosystems. Here, we compared sites that had undergone two or three years of rehabilitation after iron ore mining on the Urucum Massif, MS, Brazil, with native reference sites. The species composition as well as structural, taxonomic, and phylogenetic diversity indices were compared between the reference and rehabilitating sites. Despite the differences in species composition between the rehabilitating and reference sites, we found more than 50 native species and partial recovery of the vegetation structure in the rehabilitating sites. Furthermore, we detected similar levels of animal‐dispersed plant species at rehabilitating and reference sites. These environmental indicators indicate that trial‐and‐error approaches are indeed able to establish considerable native species diversity during mineland rehabilitation. Furthermore, the partial recovery of the vegetation structure suggests the gradual return of soil functions in the long term, and the presence of zoochorous species is expected to attract seed‐dispersing animals that enable gene flow as well as the arrival of additional plant species. Nevertheless, the high cover values of alien exotic species, which are negatively correlated with the diversity of the reinstated communities, endanger the success of mineland rehabilitation in the Urucum Massif, and effective control methods for invasive populations are required. These efforts should be accompanied by enrichment plantings to maintain the diversity of native plant communities at the rehabilitation sites and ongoing environmental monitoring. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The continuous monitoring of mineland rehabilitation is paramount for identifying deviations from desired trajectories and providing assessments for environmental agencies. In this study, we analyzed soil texture and chemical properties, vegetation development and soil respiration along rehabilitation chronosequences including nonrehabilitated areas, areas at different rehabilitation stages and reference sites covered by native forests in three sand mines in the Carajás National Forest, eastern Amazonia, Brazil, to estimate their rehabilitation status. For nine environmental variables related to ecological processes, vegetation structure, and community diversity, we computed response ratios in relation to predisturbance levels found in native reference sites and integrated them into an index of rehabilitation status using a multivariate approach. Our analyses showed that the soil chemical properties and tree community composition of the rehabilitated minelands converged over time to those of native ecosystems. All environmental indicators and the overall rehabilitation status increased with rehabilitation time, indicating that rehabilitation interventions set the rehabilitation trajectory on a desired path. Although most indicators did not achieve predisturbance levels, we conclude that rehabilitation activities can effectively reduce the environmental impacts of sand extraction in Amazonia over short time periods, thereby contributing to the recovery of ecosystem services and the protection of biodiversity. [ABSTRACT FROM AUTHOR]

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Copyright of Rodriguésia is the property of Revista Rodriguesia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Highlights: [•] A total of 36 AMF species were recovered in pasture and forest. [•] Conversion of pasture to forest influence AMF taxonomic composition. [•] AMF species richness and abundance distribution were similar between forest and pasture. [Copyright &y& Elsevier]

Acid Mine Drainage (AMD) is an environmental problem associated with mining activities, which resulted from the exposure of sulfur bearing materials to oxygen and water. AMD is a pollution source due to its extreme acidity, high concentration of sulfate, and soluble metals. Biological AMD treatment is one alternative to couple environmental amelioration for valuable dissolved metals recovery, as a new source of raw materials. Covellite (CuS) particles were synthetized from an AMD sample collected in a Brazilian copper mine, after 48 and 96 h of exposure to hydrogen sulfide (H2S) produced in a bioreactor containing acidophilic sulfate reducing bacteria (SRB). The time of exposure affected the morphology, nucleation, and size of CuS crystals. CuS crystals synthetized after 96 h of H2S exposure showed better ordination as indicated by sharp and intense diffractograms obtained by X-ray diffraction (XRD), and the predominance of placoid sheets with hexagonal habit structure as observed by scanning electrons microscopy (SEM). Energy dispersive X-ray fluorescence (EDXRF) spectrometry indicated a Cu:S molar ratio in agreement with CuS. Granulometric analysis demonstrated that 90% of CuS particles were less than 22 µm size. AMD biological treatment is a potential economical CuS recovery option for metallurgical process chain incorporation, or new industrial applications, since the alteration of synthesis conditions can produce different crystal forms with specific characteristics. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The trophic relationships between earthworms and three species of AMF were evaluated. • P. corethrurus produces more casts eating on roots with R. clarus and C. etunicatum. • P. corethrurus concentrate propagules of R. clarus and C. etunicatum in their casts. • R. clarus and C. etunicatum spores extracted from casts germinate better. • P. corethrurus shows feed preference for roots with R. clarus and C. etunicatum. Abstract Earthworms and arbuscular mycorrhizal fungi (AMF) are essential for nutrient cycling and organic matter dynamics in terrestrial ecosystems. In soils, they tightly interact especially in the rhizosphere. Therefore, the objective of this study was to evaluate the trophic relationship between the earthworm Pontoscolex corethrurus and three species of AMF (Rhizophagus clarus , Claroideoglomus etunicatum , and Gigaspora margarita). We performed bioassays with different experimental designs and treatments, to evaluate cast production by P. corethrurus in the three different substrates, the number of AMF propagules after ingestion by earthworms, the germination capacity of ingested spores, the earthworm feeding preferences, and the influence of AMF species on earthworm growth. P. corethrurus produced more casts when R. clarus and C. etunicatum was present in the food source. Spore number, percentage of germinated spores and most probable number of infective propagules of R. clarus and C. etunicatum were higher in earthworm casts than in soil inocula, whereas opposite trend of results was found with G. margarita , suggesting that the digestion of AMF propagules by P. corethrurus varies with the AMF species. Earthworm weight increased when they were fed with R. clarus and G. margarita soil-inocula, but individuals showed no clear preference for different AMF species. Roots colonized by R. clarus were more attractive to P. corethrurus. Findings of this study have important implications for the roles of P. corethrurus in mycorrhizal potential of R. clarus e C. etunicatum and in the reduction of the propagules of G. margarita in soil. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal fungi (AMF) play a key role in plant nutrition and in the maintenance of soil fertility in agroecosystems, but their survival can be affected by different agricultural practices, including the use of pesticides. In this work, we assessed the impact of chemicals with herbicidal and fungicidal activity on mycelial growth and structure of the worldwide distributed AMF Funneliformis mosseae. Results showed that mycelial growth and interconnectedness of three different F. mosseae lineages were affected by the chemicals tested at concentrations lower than those indicated for agricultural use. Indeed, benomyl reduced mycelial growth in one lineage and fenhexamid negatively affected germlings growth in the three lineages, while both fungicides significantly affected mycelial viability and induced abnormal hyphal branching. The three F. mosseae lineages showed sensitivity to herbicides, with significant growth and viability decreases in the presence of the active ingredient glufosinate ammonium and a low viability at increasing concentrations of dicamba. Anastomosis rates were reduced by the two fungicides and by very low levels of the herbicide glufosinate, whose impact on AMF networks should be further investigated, given its wide use in agriculture. Our results suggest that the use of some pesticides in agroecosystems may lead to growth reduction and disruption of AMF mycelial structural traits, even in AMF species able to tolerate soil disturbance, posing serious threats to AMF symbiotic performance and to the maintenance of soil mycorrhizal potential. • Fungicides affect mycelial growth and viability of arbuscular mycorrhizal fungi. • Mycelial interconnectedness of arbuscular mycorrhizal fungi is reduced by fungicides. • The herbicide glufosinate decreases mycelial growth and interconnectedness. [ABSTRACT FROM AUTHOR]

Highlights • Endangered Isoetes cangae produces large quantities of viable spores per sporangia. • Large number of sporelings emerge from male and female spores in vitro culture. • The megaspore nutrient reserve ensures longstanding sporeling growth. • Sporelings are able to grow in a range of substrates and temperature regimes. • Successful growth and low mortality suggest that I. cangae is a resilient species. Abstract Isoëtes L. is a nearly cosmopolitan rhizomorphic lycopsid genus fundamental to disentangling plant evolution because of its singular position in the Plantae kingdom. A threatened Amazonian species recently described is I. cangae, inhabiting an oligotrophic upland lake over an iron-rich region facing substantial environmental alterations. In this study, we aim to optimize a reproduction protocol that can assist in the conservation efforts of Isoëtes species in tropical areas. We observed an average of 126 megaspores or 318,000 microspores per sporangia in field-collected plants. We obtained an elevated percentage of sporelings (63%) from an in vitro mixed culture of mega- and microspores. In addition, we recovered a large number of sporelings around adult plants after cultivating them over quartzite sand and distilled water. The megaspore nutrient reserve ensured longstanding sporeling growth and development in these environmental conditions. However, the sporeling growth rate increased when they were planted over their original lake sediments or over an organic substrate, with nonsignificant differences between the substrates. An increase in temperature also increased the sporeling growth rate. Together with the very low sporeling mortality, these results suggest that I. cangae is a resilient species able to grow and colonize environments with low trophic characteristics with a range of substrates and temperature regimes. The protocols established in this study could be useful for the ex situ propagation and growth of a large number of sporelings, representing critical steps towards the population rescue and conservation of tropical Isoëtes species. [ABSTRACT FROM AUTHOR]

Despite the urgent demand for sustainable mining, the revegetation and rehabilitation of areas degraded by mining activities remain challenging. Uncertainties about species selection, the management and control of alien invasive species and monitoring procedures require ongoing multidisciplinary research. Modern functional and phylogenetic approaches in community ecology represent powerful tools to enhance the entire rehabilitation process and to overcome these challenges, but methodologies that incorporate up-to-date phylogenetic information or knowledge about intraspecific variation along rehabilitation trajectories must be developed. Functional and phylogenetic criteria may play an especially important role in guiding the definition of faster-growing, more resistant species mixtures that can be applied in mine land revegetation and rehabilitation. Limiting similarity approaches may help to reduce biological invasions, enabling native vegetation to outcompete alien invasive species and aiding in the development of enduring mechanisms for controlling such species in rehabilitated mine land. Finally, incorporating phylogenetic and functional aspects into monitoring of the success of mine land rehabilitation with additional tools, such as remote sensing or metabarcoding, can enrich scientific knowledge about ecosystem functions such as nutrient cycling, community assembly and resource availability while providing sound information about the success of revegetation activities. In the middle to long term, research activities on these topics can provide valuable technical recommendations for all aspects of the management of rehabilitated ecosystems, thus contributing to more sustainable mining. [ABSTRACT FROM AUTHOR]

In 2015, the Fundão Dam collapse released over 40 million m3 of iron mine tailings, causing several environmental damages. Certain affected areas were revegetated with a mix of fast-growing species that can allowed the return of some organisms of soil fauna. Nematodes are the most abundant multicellular organisms in soil and are commonly used as bioindicators. Therefore, this study aimed to use the nematode community as bioindicators of the restoration process of an area affected by iron tailings at the margins of the Gualaxo do Norte River. Soil samples were collected from affected and native forest areas to perform physical, chemical, biochemical, and biological analyses. Nematodes were identified and classified according to feeding habits and on a colonizer-persisters (cp) scale. A non-metrical multidimensional scaling and PERMANOVA were conducted to assess differences between communities. Shannon's diversity index and the maturity index were significantly higher in the restoration area. There was a difference in the composition and the structure of nematode communities of the restoration and reference area, nematode genus occurrence and abundance were different between the areas resulting in differences in feeding habits and life strategies according to the cp scale. The cp-5 nematodes are more abundant in the restoration area and cp-1 in the forest reference area. Bacterivore nematodes were more abundant in the reference forest area. In addition, the soil attributes in the restoration area were altered following the tailings deposition. Such alterations include high pH, low organic matter content, and low microbial biomass, which consequently influenced the structure and the composition of the nematode community. This is likely the first report of soil nematode community diversity in the areas of the Rio Doce Basin impacted by the Fundão tailings, and nematodes proved to be good bioindicators to show the differences between the restoration and forest reference area. • This is the first study with nematodes in the impacted areas by Fundão tailings. • There is a great diversity of nematodes in the area under restoration process. • The nematode community between the restoration area and the reference is distinct. [ABSTRACT FROM AUTHOR]

Highlights: [•] All isolates abundantly colonized the corn roots, but only 23 promoted higher growth and P content. [•] The ability to promote growth and P nutrition was independent of the origin of the isolates. [•] Physiological responses were related to the ability of the fungi to provide P to the host in 93% of the fungus-plant combinations. [•] Functional variability can be greater between isolates of the same species than between isolates of distinct species. [•] The morphological characterization agreed with the genotypic characterization by 18S rDNA PCR-RFLP and sequencing. [•] R. clarus and S. heterogama isolates were consistently efficient in promoting corn growth. [Copyright &y& Elsevier]

• Geochemical background values in soils of Itacaiúnas River Basin are presented. • The validity of log-ratio transformation in compositional data analysis was discussed. • mMAD is the most preferred method for determining geochemical background values. • CONAMA Resolution 420/2009 limits are unrealistic to determine anthropogenic impact in Itacaiúnas soils. • High anomalies of Cr, Cu, and Ni are linked to catchment lithology and mineralization. This study aims at providing high quality soil geochemical data at a regional scale (1 sample per 25 km2) to understand the source and distribution of potentially toxic elements (PTEs: Al, As, Ba, Cd, Cu, Co, Cr, Fe, Hg, Mo, Mn, Ni, Pb, Se, U, V, and Zn) and to define their geochemical background threshold values (GBTVs) in the Itacaiúnas River Basin (IRB), Brazilian Amazon. A total of 2958 soil samples were collected at two depths (surface: 0–10 cm; bottom: 30–50 cm) and the fine fractions (<0.117 mm) were analyzed by ICP-MS and ICP-AES after aqua-regia digestion. The compositional nature of geochemical data was evaluated using the log-ratio approach and compared with traditional methods. Results show that compared to raw/log-transformation, centred log-ratio (clr) transformation improves spatial mapping and also better separated variables in Principal Component Analysis (PCA). Correlation analysis based on the isometric log-ratio (ilr) transformation in heat-maps provides reliable and better structure of the results. The spatial maps (clr) indicate that most of the elements in surface and bottom soils are mainly governed by underlying bedrock geology (parent lithologies and mineralization), while anthropogenic factors are insignificant. The resulting clr-based PCA and cluster analyses associated with geological information indicate that geochemical patterns of Fe-Ti-V-Cr-Sc can be linked to mafic to intermediate metavolcanic rocks and banded-iron formations, which are dominant in the Carajás basin, while Ni and Cr distribution pattern is attributed to mafic and ultramafic lithologies, and Cu anomalous values are mainly related to hydrothermal mineralized copper belts. Among the statistical methods applied for estimation of GBTVs, TIF produced the highest BTVs, followed by 98th and mMAD, with few exceptions, while mMAD was considered the more suitable for defining GBTVs. The number of potential anomalies of PTEs identified by these methods follow the order of MAD > 98th > TIF or MAD > TIF > 98th, and overall the anomalies are mostly related to the local lithology/mineralization with no indication of anthropogenic contamination. Compared with Brazilian guidelines (CONAMA Resolution No. 420/2009), the GBTVs determined for Cr, Co, Ni, and Cu by TIF, MAD, and 98th percentile mostly exceeded both IV and PV limits. However, these high values are due to the influence of local lithology. This reveals that the Brazilian CONAMA guidelines of these elements for the IRB are unrealistic because that suggests a large number of sites requiring investigation, which is not consistent with the geochemical evidence. Therefore, site-specific GBTVs must be considered for the accurate evaluation of anthropogenic contamination, as well as the ecological and human health risks of PTEs in this region. [ABSTRACT FROM AUTHOR]

Multi-elemental analysis of high-density (regional-scale) geochemical surveys is an important strategy for multi-purpose applications, particularly in addressing geochemical background concentrations in different sampling media. This approach was applied to the Itacaiúnas River Watershed (IRW), which is situated in the most prominent mining area of Brazil, the Carajás Mineral Province. Microcatchment-based mapping (~50 km2 each) covering the whole extent of IRW was delimited using remote sensing techniques and targeted for sampling. A total of 788 samples, including 27 duplicates, were collected in 2017. The <0.177 mm fraction of all samples was digested by aqua regia and 51 elements were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). Geochemical maps for Fe and potentially toxic elements (PTE; As, Ba, Cd, Co, Cr, Cu, Hg, Mn, Mo, Ni, Pb, Sn, V, and Zn) and microcatchment-based distribution maps based on threshold values were constructed for the whole IRW. The stream sediment geochemistry is mainly controlled by the local geologic setting and underlying lithology. Geochemical background (GB) values for 43 elements in stream sediments of the IRW were determined by a variety of methods (Tukey's inner fences -TIF, median ± 2*median absolute deviation - MAD, and percentile-based techniques). The results provided from the different methods show a wide range of values, with the MAD method being considered the most appropriate for deriving GB concentrations. A comparison of reference levels for PTE contemplated in the Brazilian regulation in stream sediments, the threshold concentrations obtained for the IRW area, and different study cases around the world is presented in detail. Our findings provide not only valuable information for selecting potential areas for mineral exploration surveys, but also for evaluating geochemical contaminant effects with time-varying treatments. Studies conducted to determine background values at regional scale are needed for environmental decision making, as well as to attest actions in cases of potential contamination. In the absence of these studies, misleading interpretations of the magnitude of contamination levels in a certain area may cause under- or overestimation of ecological and/or human-health risks of PTE. Image 1 • Stream sediments background values of the Itacaiúnas River basin were determined. • Median+2*MAD method gives better results for deriving geochemical background. • There is no clear contamination associated to anthropogenic activities. • Geological setting controls the distribution of Fe and potentially toxic elements. • Regional background studies are needed to define sediment quality guidelines. [ABSTRACT FROM AUTHOR]

Functional ecology provides useful tools for selecting native species for rehabilitation purposes. Here, we evaluated a list of native tree and shrub species as candidates for use in waste pile rehabilitation in the Carajás National Forest, eastern Amazon, Brazil, to increase the diversity and stability of the reinstated communities. Native species lists were compiled from vegetation inventories performed in two different ecosystems in the region, i.e., dense evergreen Amazonian forests and ferriferous savannah formations, locally known as cangas. For prospection, we evaluated the functional differences among the forest, canga and waste pile communities and computed the functional space defined by wood density and 14 leaf traits of species that had already established during former rehabilitation efforts targeting the waste piles. Native species falling within this trait space were selected for further initial rehabilitation activities, while species outside this space were considered unsuitable for this purpose. As a proof of concept, we compared the survival of seedlings of selected and nonselected tree species to evaluate their potential for initial rehabilitation activities. We found functional differences in the communities between the rehabilitating waste piles and natural environments but higher functional congruence with forest than with canga ecosystems, making the conversion of waste piles into forests more likely. The assessment of functional differences enabled the identification of additional species for initial waste pile rehabilitation; we present a list of 76 candidates for future waste pile rehabilitation activities in Carajás National Forest. Our approach was validated by the seedling survival experiment, where selected species showed higher survival than nonselected species, highlighting the suitability of the selected species for initial waste pile rehabilitation in the region to increase the species richness and functional redundancy of the reinstated communities. The validation via the seedling survival experiment furthermore encourages the replication of the proposed functional prospection procedure for other environments to be rehabilitated, with different species sets being sought for different regions. • Functional selection of species for rehabilitation is validated by a proof of concept. • Seventy-six candidates for future waste pile rehabilitation activities are presented. • Suitability is confirmed by higher survival of selected species on waste piles. • Functional congruence indicates the convergence of waste piles to forest ecosystems. [ABSTRACT FROM AUTHOR]