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Abstract Statistical evaluation applied to geochemical data of upland lake sediments and their catchment basins rocks from Serra dos Carajás was used to identify geochemical signatures associated with underlying processes, sediment provenances, and source-sink relationship. The lakes are Violão, Amendoim and Três Irmãs - TI1, TI2 and TI3. A centred log-ratio transformation (clr) was used prior to multivariate analyses in order to eliminate closure issues in compositional data. Due to the similarity between δ15N values and organic sources (mainly from C3 plants), the three lakes were clustered together. Violão Lake receives largest organic contribution from autochthonous sources, such as siliceous sponge spicules and algae, except for it shallower portion (WNW extension), which is more similar to TI2, having low δ15N values that are similar to the isotopic signature of upland swamps. The upper continental crust (UCC) normalization pattern shows that sediments are mainly enriched in Fe, P and Se, which is closely related to the catchment lithology. The distribution of elements in TI2 is significantly different from the other lakes, because it is dominated by organic carbon, while the other lakes are a mix of detritus and organic carbon. Factor Analysis (FA) using clr-transformed data distinguishes several geochemical assemblages in the sediments, with the major detritic groups being similar to catchment basin laterites: the Ti-Zr-Hf-Nb-Y-HREEs group corresponds to resistant minerals which remained stable during lateritization; the LREEs group reflects mobilization and reprecipitation by REE bearing minerals; and the Al-V-Cr-Sc association reflects metavolcanic rock. The Fe-P-Mo-As-Zn cluster in the sediments is attributed to Fe-oxyhydroxide precipitation, while TOC-SO 3 -Hg-Se group is controlled by organic matter. Principal Component Analysis (PCA) further indicates that detritic lake sediments are not directly derived from the parent rocks, but from weathered crusts, mainly ferruginous laterites and soils, which is consistent with their elements ratios. Highlights • Geochemical interpretation of Carajás upland lakes is aided by multivariate statistical analysis. • PCA performed on clr transformed data significantly eliminates closure issues. • Clr-transformed PCA classified efficiently the multi-element geochemical signature in lake sediments. • Lake sediment geochemical signature is due to catchment basin lithology and lateritization. • Clr-transformed PCA identified the major provenance of lake sediments. [ABSTRACT FROM AUTHOR]

Lake Três Irmãs (LTI), the largest upland lake in the Brazilian Amazonia, located in Serra dos Carajás, was characterized using multi-elemental and isotope geochemistry (δ 13 C and δ 15 N) to understand the significance of organic and inorganic sources, weathering and sedimentary processes on the distribution of elements in lake bottom (surficial) sediments. Carbon and nitrogen isotopes from sedimentary organic matter suggest C3 terrestrial plants (forests > canga vegetation), macrophytes and freshwater DOC as the main sources. Sediments are depleted in most of the major oxides (except Fe 2 O 3 and P 2 O 5 ) when compared to upper continental crust (UCC) and their spatial distribution is highly influenced by catchment lithology. Principal Component Analysis revealed that most of the trace elements (Ba, Sr, Rb, Sc, Th, U, Zr, Hf, Nb, Y, V, Cr, Ga, Co, Ni) and REEs are closely correlated with Al and Ti (PC1; Group-1), so their redistribution is less influenced by post-depositional process. This is due to their relative immobility and being hosted by Al-bearing minerals during laterization. High Chemical Index of Alteration (CIA), Mafic Index of Alteration (MIA) and Index of Laterization (IOL) values indicate intense chemical weathering at source areas, but the weathering transformation was better quantified by IOL. A-CN-K plot along with elemental ratios (Al/K, Ti/K, Ti/Zr, La/Al, Cr/Th, Co/Th, La/Sm, La/Gd, Zr/Y, and Eu/Eu*) as well as chondrite-normalized REE patterns show that the detritic sediments are mainly sourced from ferruginous laterites and soils in the catchment, which may have characteristics similar to mafic rocks. [ABSTRACT FROM AUTHOR]

The expansion of areas of human occupation and the increase in economic activity and deforestation are negatively impacting the Amazon ecosystem. Situated in the Carajás Mineral Province in the southeastern Amazon, the Itacaiúnas River Watershed (IRW) encompasses several active mines and has a historical record of intense deforestation primarily linked with the expansion of pasturelands, but also of urban areas, and mining activities. Industrial mining projects are subjected to strict environmental control, but artisanal mining (ASM; 'garimpos') sites have not been controlled, despite their known environmental impacts. In recent years, the opening and expansion of ASM in the IRW for the exploitation of mineral resources (Au, Mn, and Cu) have been remarkable. This study presents evidence of anthropogenic impacts, mainly caused by ASM, on the quality and hydrogeochemical characteristics of the IRW surface water. The hydrogeochemical data sets of two projects carried out in the IRW, during 2017 and from 2020 until present, were used to evaluate these impacts within the region. Water quality indices were calculated for the surface water samples. For the whole IRW, water collected during the dry season tended to yield better quality indicators in comparison to those collected during the rainy season. Two sampling sites at Sereno Creek showed very poor water quality and extremely high concentrations of Fe, Al, and potentially toxic elements over time. From 2016 to 2022, ASM sites increased markedly. Moreover, there are indications that Mn exploitation via ASM in Sereno hill is the main source of contamination in the area. New trends of ASM expansion were observed along the main watercourses, related to the exploitation of Au from alluvial deposits. Similar anthropogenic impacts are registered in other regions of the Amazon and environmental monitoring should be encouraged to assess the chemical safety of strategic areas. [Display omitted] • Climate, pedogeochemistry and land cover influence surface water composition. • Artisanal Mining (ASM) sites of Mn and Au impacted water quality. • ASM sites increased by more than 1500 ha (2883%) from 2016 to 2022. • Potentially toxic element concentrations are greater than background values. • Environmental monitoring of water bodies is mandatory for the Amazon. [ABSTRACT FROM AUTHOR]

Various compounds that are emerging contaminants pose a significant risk to aquatic ecosystems and human health due to their potential to harm human health and the environment.Thus, there is an urgent requirement to use effective remediation methods and techniques to minimize the harmful impact of these contaminants on the environment. Biochar (BC) is a lightweight black residue that is made of carbon after the pyrolysis of biomass. BC is a product that is stable, rich in carbon, and exhibited improved properties. BC has come up with fascinating properties and results to remediate these pollutants from the soil effectively. Furthermore, it becomes possible to recover resources using BC because of the benefits such as (a) it offers in terms of cost, (b) the preservation of nutrients, and (c) the efficiency with which it absorbs pollutants. Consequently, it is necessary to have a knowledge of the interaction involving biochar and resource recovery to explore the applicability of BC in the cleaning up of the surroundings and the exploitation of wastewater. This review emphasize the physio-chemical and biological modification methods for the preparation of various types of engineered BC. Therefore, the present review aims: (i) provide an overview of emerging pollutants of human activities in soil (ii) synthesis and engineer BC for field application (iii) critically discuss and evaluate the factors affecting large-scale application techno-economic challenges. The review provided insight into the areas that need immediate attention in the upcoming investigation regarding the use of engineered biochar for wastewater treatment. [Display omitted] • The various strategies to engineer the biochar have been discussed. • The effects of various pollutants in the soil and water have been highlighted. • The biochar based remediation of various pollutants have been discussed. • Techno-economic analysis and various challenges in large scale application discussed. [ABSTRACT FROM AUTHOR]

A multi-proxy geochemical study of surficial sediments of an upland lake (Amendoim Lake), located in the Serra dos Carajás region, Brazil, was carried out to understand catchment weathering and provenance of sediments in the basin, as well as sedimentary processes. The carbon and nitrogen isotopic compositions of organic matter in the sediment were quite homogeneous, and suggest that the organic sources for this lake are mainly composed of palms and submerged macrophytes. The R-mode factor analysis indicates that most of the trace elements, including rare earth elements (REEs), are clustered with Al (Group 1), Si is grouped with Zr and Hf (Group 4), total organic carbon (TOC) with TS and Hg (Group 2), and Fe with Mn and As (Group 3). The elements of the Group 1 show strong positive correlations with Al, suggesting that these elements are hosted in detrital minerals during laterization in the catchment basin and not significantly affected by diagenesis. The high CIA values (96–99) of sediments together with their position in A-CN-K and log (Fe 2 O 3 /K 2 O) vs log (SiO 2 /Al 2 O 3 ) plots indicate intense chemical weathering in source area. However, similar geochemical signatures between lake sediments and catchment lateritic crust indicates that mechanical erosion was the dominant sediment formation process. REE patterns normalized to chondrite along with geochemical indices (Al/K, Al/Ti, La/Th, La/Al, Ti/Zr, Zr/Hf, Th/Sc, Co/Th, Ba/Sr, and Eu/Eu*) also indicate that the sediments are mainly derived from laterite crust. This study provides reliable background information to reconstruct weathering processes and lake evolution in the Serra dos Carajás area. [ABSTRACT FROM AUTHOR]

Over the last several decades, extensive and inefficient use of contemporary technologies has resulted in substantial environmental pollution, predominantly caused by potentially hazardous elements (PTEs), like heavy metals that severely harm living species. To combat the presence of heavy metals (HMs) in the agrarian system, biochar becomes an attractive approach for stabilizing and limiting availability of HMs in soils due to its high surface area, porosity, pH, aromatic structure as well as several functional groups, which mostly rely on the feedstock and pyrolysis temperature. Additionally, agricultural waste-derived biochar is an effective management option to ensure carbon neutrality and circular economy while also addressing social and environmental concerns. Given these diverse parameters, the present systematic evaluation seeks to (i) ascertain the effectiveness of heavy metal immobilization by agro waste-derived biochar; (ii) examine the presence of biochar on soil physico-chemical, and thermal properties, along with microbial diversity; (iii) explore the underlying mechanisms responsible for the reduction in heavy metal concentration; and (iv) possibility of biochar implications to advance circular economy approach. The collection of more than 200 papers catalogues the immobilization efficiency of biochar in agricultural soil and its impacts on soil from multi-angle perspectives. The data gathered suggests that pristine biochar effectively reduced cationic heavy metals (Pb, Cd, Cu, Ni) and Cr mobilization and uptake by plants, whereas modified biochar effectively reduced As in soil and plant systems. However, the exact mechanism underlying is a complex biochar-soil interaction. In addition to successfully immobilizing heavy metals in the soil, the application of biochar improved soil fertility and increased agricultural productivity. However, the lack of knowledge on unfavorable impacts on the agricultural systems, along with discrepancies between the use of biochar and experimental conditions, impeded a thorough understanding on a deeper level. [ABSTRACT FROM AUTHOR]

Geochemical and isotopic compositions of surficial sediments from a plateau lake in Carajás, Southeastern Amazon region, were investigated to understand the spatial distribution of major and trace elements, δ 13 C, δ 15 N, and C/N ratio, depositional processes, and the origin of inorganic and organic fractions. The δ 13 C, δ 15 N, and C/N ratio indicate mainly an autochthonous source, with siliceous sponge spicules and algae being the major source of organic matter in the center of the lake (Sector 3), while an allochthonous source, mainly derived from C3 vascular forest plants dominates in the shallowest portion of the lake (Sector 1). Consequently, there was an apparent dilution of C4 plants (montane savanna) in the sediment/water interface. Among major elements, Fe 2 O 3 is highly enriched in Sector 3, which is controlled by the erosion of catchment laterites and underwater topography, while Al 2 O 3 and P 2 O 5 enrichment near the northern border of the lake is controlled by the weathering of mafic rocks. Similar spatial distribution of SiO 2 with total organic carbon (TOC) and isotopic evidence indicate that Si distribution is partially controlled by organic components such as siliceous sponge spicules and algae. The occurrence of most of the trace and rare earth elements (REE) is independent of Fe 2 O 3 and TOC, but controlled by detrital aluminum silicates and heavy minerals, indicating a lack of post-depositional diagenetic control on their distribution. The distribution of As and Mo are possibly controlled by organic matter mineralization during early diagenesis and subsequently precipitation of Fe phases. The values of the chemical index of alteration (CIA) in the sediments are very high (94–99) and similar to those of the source rocks, suggesting that sediment composition is mainly controlled by mechanical weathering, rather than chemical weathering. Geochemical indices (Al/K, Ti/K, Al/Ti, La/Th, Ti/Zr, Zr/Hf, Hf/Nb, La/Al, Co/Th, Ba/Sr, and Th/Sc), together with the A–CN–K plot, suggest that the provenance of the inorganic sediments remained relatively uniform or constant during the depositional period, and that they were mainly derived from laterite crusts and subordinately from mafic soils. This inference was further substantiated by the chondrite-normalized REE patterns and discrimination plots. Geochemical indices such as U/Th, authigenic-U, Mo/Al, and V/Cr indicate that the sediments were deposited under an oxic environment. [ABSTRACT FROM AUTHOR]

Multivariate statistical approaches were applied on geochemical data of lake sediments and the catchment basin materials (Al-enriched crusts and soils) from four upland lakes (namely LB1, LB2, LB3, and LB4) in the Serra da Bocaína, Southeast Amazon, to recognize the geochemical signatures of lake sediments and their link with source rocks. This is also compared with Fe-enriched crusts and soils, which collected from Serra Sul de Carajás. The major and trace elements were analyzed by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) and X-ray Fluorescence (XRF), and Inductively Coupled Plasma Mass Spectrometry (ICP-MS), respectively. The data closure effect was reduced by centred log ratio (clr) transformation. The upper continental crust (UCC) normalized patterns show that sediments are mainly enriched with Ti, Fe, P, Se, V and Cr, similar to catchment basin crusts and soils. The distribution of elements varied between lakes, which is mainly influenced by the morphology and lithology of the basin. The chemical index of alternation (CIA) values were very high (>90) for both lake sediments and catchment materials, which indicates intense source area weathering. Index of lateritization (IOL) shows that the catchment crusts are strongly lateralized and it identifies samples between extremely weathered and reworked samples that do not meet the criteria for strict in situ formation. The principal components analysis (PCA) and Spearman correlation matrices based on clr-transformed data revealed four geochemical groups in sediments. The major detritic geochemical association of sediments (Group 1: Al–Ti-Ga-Cr-V-Ti-Nb-Sc, which indicative of mafic/metavolcanic rock; and Group 2: Zr-Hf-HREEs, which refers to the heavy mineral fractions that remain stable during lateritization) had a close relationship with catchment lateritic crust, except a few alterations, which possibly influenced by weathering and transport processes. REE pattern normalized to chondrite and the geochemical ratios show the analogies between the lake sediments and the catchment lateritic crusts. The linear discriminant analysis (LD) and PCA distinguished Al-rich laterites from Fe-rich laterites and indicates that the former (which likely derived from mafic/metavolcanic rocks) is the main source of lake sediments. • Source-sink geochemical relationship was established for Bocaína lakes. • Index of Lateritization is a potential weathering index in lateritic environment. • Lake sediments provide geochemical evidence of catchment basin rocks. • Multivariate statistics efficiently discriminate the provenance of lake sediments. • Lakes sediments were mostly the weathering product of Al-enriched laterites. [ABSTRACT FROM AUTHOR]

A high resolution systematic geochemical mapping at regional-scale is considered to be the best available method to estimate geochemical baseline levels of trace elements in stream water, and is an essential part of environmental risk assessment. This methodology was applied in a project in the Itacaiúnas River Basin, southeastern Amazon, Brazil, which includes several mines of the Carajás Mineral Province (as part of the Itacaiúnas Geochemical Mapping and Background Project, ItacGMBP). A total of 1429 samples (including 55 duplicates) were collected in 2017 at 900 sites at one sample per microbasin, during both dry and rainy periods. The analyses of 34 elements were carried out using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). In general, the waters are slightly alkaline and are classified as mixed Ca-Na-HCO 3 type, indicating that they are mainly influenced by silicate rock weathering. Most metal concentrations in the water are low, except Fe and Mn. Seasonality explains differences in metal concentrations, with higher values being obtained in the rainy season. Baseline threshold values (B TVs) were calculated separately for both seasons by employing different statistical methods: iterative 2σ and DF preferentially delivered a more restrictive or conservative levels, which can be represenative of the natural B TVs (NB TVs), considering as the least degraded with low or no significant level of anthropogenic influence; and 98th percentile provides the ambient B TVs (AB TVs), which consists of natural plus diffuse anthropogenic input in the defined area. The AB TVs of Fe and Mn significantly exceed the WHO (1998) and CONAMA 357/05 limits. Spatial distribution indicates that Fe and Mn are not strictly related to geologic setting, rather they are highly influenced by specific local land use as well as deep weathering of the catchment and intense leaching and run-off during the rainy season. However, higher Mn occurrence in the dry period results from redox cycling of Fe and Mn via biogeochemical processes. The AB TVs of Ni, Cr, and V are controlled by bedrock lithology (geologic setting), mainly associated with mafic-ultramafic rocks; Cu is associated with two large hydrothermally mineralized copper belts. The estimation of baseline levels of As, Se, and Pb were highly limited due to of the large number of samples with results less than detection limits, in this case the 95th percentile was used for their B TVs. Geochemical data as well as anomalous values for most of the metals indicate that anthropogenic influence from point sources is highly negligible in the basin, except at a few points, where high NO 3- has been observed, probably due to more intense human and livestock activity. This study demonstrates that site-specific geochemical baseline assessment is a crucial factor when evaluating surficial water conditions in a large basin. • First detailed high resolution hydrogeochemical survey was carried out in Itacaiúnas basin. • We estimated the natural (NB TV) and ambient (AB TV) baseline threshold values. • High AB TVs of Fe and Mn in waters are related to local land use change activities. • The AB TVs of Cu is highly influenced by the hydrothermal mineralized copper belts. [ABSTRACT FROM AUTHOR]

New insights about climate conditions and their effect on vegetation and lakes of southeastern Amazonia were achieved over the last 50 cal ka using recent data obtained from a filled lake located in the Serra Sul de Carajás. Our analysis was done in a sediment core (R2) comprising of faciological, palynological, isotopic and radio carbon measurement supported by Bayesian age-depth modeling, as well species distribution modeling. Wet and cool climate conditions are proposed for the mid-Pleniglacial, which is favorable to intense weathering of the lake's catchment area and the expansion of high altitude taxa (cool-adapted) into forest formations during this period. From the late Pleniglacial to the Last Glacial Maximum, a change from relatively wet to dry climate possibly converted the studied lake from oxidizing to reducing conditions, which leads to the formation of diagenetic siderites at the end of this time interval. Warming during the Pleistocene to Holocene transition caused the disappearance of cool-adapted taxa in the study site. Concomitantly, increasing precipitation allowed the expansion of forest and high lake levels. A drier early-mid Holocene produced extensive open vegetation and desiccated lakes. Current climate and environmental conditions were likely attained in the region from the mid to late Holocene. [ABSTRACT FROM AUTHOR]

In the past two decades, several paleobotanical studies on lakes have indicated a drier climatic condition in Amazonia during the Last Glacial Maximum (LGM) and early-mid Holocene, which likely resulted in the contraction of the tropical forest and expansion of savanna. However, these investigations in the eastern Amazon are scarce, and the reliability and precision of the inference remains largely limited. In this study, palynological analyses were carried out in surficial sediments of Violão Lake, southeastern Amazonia, to assess the distribution and sources of pollen and spores from montane savanna and forest, based on surrounding vegetation types, catchment basin and wind patterns, and also to identify modern pollen rain characteristics of the ecosystems developed under edaphic conditions. Considering the spatial distribution of pollen and spores in the lake basin, the montane savanna pollen are predominant in the eastern and western borders and subordinate in the central portion of the lake, whereas those of forest formations are mainly present in its western margin. Pteridophytes and algae spores show a distinct surface distribution compared to montane savanna pollen, while the algae spores have a good correlation with forest formation pollen. The correlation of these data along with vegetation types of the catchment basin indicates that the absence of pollen grains from species, that present large occurrence along the catchment basin, may be partially related to phenological characteristics that avoided pollen losses. However, in general, montane savanna pollen in the bottom sediments tends to represent a signal of the regional vegetation developed over ferruginous duricrusts in the Serra do Carajás, while forest formation pollen may be used to identify changes in forest structure of the catchment basin of Violão Lake. As montane savanna is developed under edaphic conditions in hydric stress substrate, a systematic description of pollen grains clearly demonstrates that only changes in forest vegetation can be used as a reliable indicator of paleoclimate changes. [ABSTRACT FROM AUTHOR]

Stable isotope analysis of plant waxes (δ13C wax and δD wax) along with detailed pollen data provide a new perspective on vegetation and precipitation variability in Serra Sul de Carajás, southeastern (SE) Amazonia, over the past ∼25 cal kyr BP. The δD wax record indicates drier conditions during the Last Glacial Maximum (LGM) and a transition to wetter conditions into the Holocene, while the δ13C wax data reveal that vegetation did not experienced C 3 /C 4 shifts and remained dominated by C 3 -plant communities. Under glacial conditions C 3 -savanna was prominent on the Serra Sul plateau with tropical forest areas limited to the lower slopes. Tropical forests expanded upslope and forest patches developed on the plateau as a response to more humid and warmer conditions during the Holocene. Pollen data indicate a shift towards more open landscape of savanna, woodlands, and open forests during the mid-Holocene. The δD wax record exhibits a distinct moisture variability during the Holocene, not always coherent with the vegetation data (pollen), especially during the mid-Holocene interval. Our study confirms the complexity and the overall lack of coherence among Holocene moisture proxy records throughout the monsoon domain in South America and suggest that Holocene local moisture conditions might not follow the regional monsoonal variability. Our data further stress the need for more multi-proxy reconstructions of hydroclimate patterns in SE Amazonia. • C 3 -plant communities are dominant in Serra Sul de Carajás. • Formation of no-modern-analog community during the glacial period. • Hydroclimate heterogeneities in eastern Amazonia. [ABSTRACT FROM AUTHOR]