Department Of Environmental Science And Technology
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Item Geochemical mapping in stream sediments of the Caraj�s Mineral Province, part 2: Multi-element geochemical signatures using Compositional Data Analysis (CoDA)(Elsevier Ltd, 2021-04-30T00:00:00) Salom�o, Gabriel Negreiros; Dall'Agnol, Roberto; Ang�lica, R�mulo Sim�es; Sahoo, Prafulla K.; Wang, XueqiuThe geological imprint on the geochemical background in stream sediment of the Itacai�nas River Watershed (IRW), located in the most prominent mining area of Brazil, the Caraj�s Mineral Province, was evaluated. The stream sediment dataset from the Itacai�nas Geochemical Mapping and Background Project of the Instituto Tecnol�gico Vale was used to address multi-element associations and for the definition of surface geochemical compartments by applying a series of multivariate geostatistics tools and geoprocessing techniques, through the Compositional Data Analysis (CoDA) perspective. In this study, the geochemical dataset was processed for centered log-ratio (clr) transformation prior to the Principal Factor Analysis (PFA). The spatial distribution of factor scores derived from PFA indicates a pronounced control on stream sediment geochemistry by the underlying geological setting and lithology. Relevant hidden correlations were observed among the nine extracted factors. An unsupervised classification based on k-means clustering algorithm was performed for the factor scores of 761 stream sediment samples. A multiproxy approach that combines the cluster classification and geoprocessing tools revealed a strong similarity in the spatial distribution of different geochemical compartments and geological domains of the IRW. Threshold values of 51 elements were calculated by a variety of statistical methods for references to the main four geological domains of the IRW defined using the geological framework and the geochemical compartments. These values were then compared to the background concentrations of the entire study area and to the investigation levels proposed by the Brazilian environmental agencies for potentially toxic elements. The new threshold values for the geochemical compartments of the IRW can be used for improving the assessment of environmental impact by anthropic activities, and to establish more realistic threshold values for different chemical elements in stream sediments. This study provides useful information for new mineral development projects and ore prospects, with potential benefit to the mineral sector and industry. � 2021Item Source and background threshold values of potentially toxic elements in soils by multivariate statistics and GIS-based mapping: a high density sampling survey in the Parauapebas basin, Brazilian Amazon(Springer, 2020) Sahoo, P.K; Dall�Agnol R; Salom�o, G.N; da Silva, Ferreira Junior J; da Silva, M.S; Martins, G.C; e Souza Filho, P.W.M; Powell, M.A; Maurity, C.W; Angelica, R.S; da Costa, M.F; Siqueira, J.O.A high-density regional-scale soil geochemical survey comprising 727 samples (one sample per each 5 � 5�km grid) was carried out in the Parauapebas sub-basin of the Brazilian Amazonia, under the Itacai�nas Basin Geochemical Mapping and Background Project. Samples were taken from two depths at each site: surface soil, 0�20�cm and deep soil, 30�50�cm. The ground and sieved (< 75��m) fraction was digested using aqua regia and analyzed for 51 elements by inductively coupled plasma mass spectrometry (ICPMS). All data were used here, but the principal focus was on the potential toxic elements (PTEs) and Fe and Mn to evaluate the spatial distribution patterns and to establish their geochemical background concentrations in soils. Geochemical maps as well as principal component analysis (PCA) show that the distribution patterns of the elements are very similar between surface and deep soils. The PCA, applied on clr-transformed data, identified four major associations: Fe�Ti�V�Sc�Cu�Cr�Ni (Gp-1); Zr�Hf�U�Nb�Th�Al�P�Mo�Ga (Gp-2); K�Na�Ca�Mg�Ba�Rb�Sr (Gp-3); and La�Ce�Co�Mn�Y�Zn�Cd (Gp-4). Moreover, the distribution patterns of elements varied significantly among the three major geological domains. The whole data indicate a strong imprint of local geological setting in the geochemical associations and point to a dominant geogenic origin for the analyzed elements. Copper and Fe in Gp-1 were enriched in the Caraj�s basin and are associated with metavolcanic rocks and banded-iron formations, respectively. However, the spatial distribution of Cu is also highly influenced by two hydrothermal mineralized copper belts. Ni�Cr in Gp-1 are highly correlated and spatially associated with mafic and ultramafic units. The Gp-2 is partially composed of high field strength elements (Zr, Hf, Nb, U, Th) that could be linked to occurrences of A-type Neoarchean granites. The Gp-3 elements are mobile elements which are commonly found in feldspars and other rock-forming minerals being liberated by chemical weathering. The background threshold values (BTV) were estimated separately for surface and deep soils using different methods. The �75th percentile�, which commonly used for the estimation of the quality reference values (QRVs) following the Brazilian regulation, gave more restrictive or conservative (low) BTVs, while the �MMAD� was more realistic to define high BTVs that can better represent the so-called mineralized/normal background. Compared with CONAMA Resolution (No. 420/2009), the conservative BTVs of most of the toxic elements were below the prevention limits (PV), except Cu, but when the high BTVs are considered, Cu, Co, Cr and Ni exceeded the PV limits. The degree of contamination (Cdeg), based on the conservative BTVs, indicates low contamination, except in the Caraj�s basin, which shows many anomalies and had high contamination mainly from Cu, Cr and Ni, but this is similar between surface and deep soils indicating that the observed high anomalies are strictly related to geogenic control. This is supported when the Cdeg is calculated using the high BTVs, which indicates low contamination. This suggests that the use of only conservative BTVs for the entire region might overestimate the significance of anthropogenic contamination; thus, we suggest the use of high BTVs for effective assessment of soil contamination in this region. The methodology and results of this study may help developing strategies for geochemical mapping in other Caraj�s soils or in other Amazonian soils with similar characteristics. � 2019, Springer Nature B.V.Item High resolution hydrogeochemical survey and estimation of baseline concentrations of trace elements in surface water of the Itacaiúnas River Basin, southeastern Amazonia: Implication for environmental studies(Elsevier B.V., 2019) Sahoo P.K.; Dall'Agnol R.; Salomão Gabriel Negreiros; da Silva Ferreira Junior J.; Silva M.S.; e Souza Filho P.W.M.; Powell M.A.; Angélica. Rômulo Simões; Pontes P.R.; da Costa M.F.; Siqueira J.O.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-HCO3 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 (BTVs) 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 BTVs (NBTVs), considering as the least degraded with low or no significant level of anthropogenic influence; and 98th percentile provides the ambient BTVs (ABTVs), which consists of natural plus diffuse anthropogenic input in the defined area. The ABTVs 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 ABTVs 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 BTVs. 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 NO3- 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.Item Source and background threshold values of potentially toxic elements in soils by multivariate statistics and GIS-based mapping: a high density sampling survey in the Parauapebas basin, Brazilian Amazon(Springer, 2019) Sahoo, Prafulla Kumar; Dall’Agnol, R; Salomão, G.N; da Silva Ferreira Junior, J; da Silva, M.S; Martins ,G.C; e Souza Filho, P.W.M; Powell, M.A; Maurity, C.W; Angelica, R.S; da Costa, M.F; Siqueira, J.O.A high-density regional-scale soil geochemical survey comprising 727 samples (one sample per each 5 × 5 km grid) was carried out in the Parauapebas sub-basin of the Brazilian Amazonia, under the Itacaiúnas Basin Geochemical Mapping and Background Project. Samples were taken from two depths at each site: surface soil, 0–20 cm and deep soil, 30–50 cm. The ground and sieved (< 75 µm) fraction was digested using aqua regia and analyzed for 51 elements by inductively coupled plasma mass spectrometry (ICPMS). All data were used here, but the principal focus was on the potential toxic elements (PTEs) and Fe and Mn to evaluate the spatial distribution patterns and to establish their geochemical background concentrations in soils. Geochemical maps as well as principal component analysis (PCA) show that the distribution patterns of the elements are very similar between surface and deep soils. The PCA, applied on clr-transformed data, identified four major associations: Fe–Ti–V–Sc–Cu–Cr–Ni (Gp-1); Zr–Hf–U–Nb–Th–Al–P–Mo–Ga (Gp-2); K–Na–Ca–Mg–Ba–Rb–Sr (Gp-3); and La–Ce–Co–Mn–Y–Zn–Cd (Gp-4). Moreover, the distribution patterns of elements varied significantly among the three major geological domains. The whole data indicate a strong imprint of local geological setting in the geochemical associations and point to a dominant geogenic origin for the analyzed elements. Copper and Fe in Gp-1 were enriched in the Carajás basin and are associated with metavolcanic rocks and banded-iron formations, respectively. However, the spatial distribution of Cu is also highly influenced by two hydrothermal mineralized copper belts. Ni–Cr in Gp-1 are highly correlated and spatially associated with mafic and ultramafic units. The Gp-2 is partially composed of high field strength elements (Zr, Hf, Nb, U, Th) that could be linked to occurrences of A-type Neoarchean granites. The Gp-3 elements are mobile elements which are commonly found in feldspars and other rock-forming minerals being liberated by chemical weathering. The background threshold values (BTV) were estimated separately for surface and deep soils using different methods. The ‘75th percentile’, which commonly used for the estimation of the quality reference values (QRVs) following the Brazilian regulation, gave more restrictive or conservative (low) BTVs, while the ‘MMAD’ was more realistic to define high BTVs that can better represent the so-called mineralized/normal background. Compared with CONAMA Resolution (No. 420/2009), the conservative BTVs of most of the toxic elements were below the prevention limits (PV), except Cu, but when the high BTVs are considered, Cu, Co, Cr and Ni exceeded the PV limits. The degree of contamination (Cdeg), based on the conservative BTVs, indicates low contamination, except in the Carajás basin, which shows many anomalies and had high contamination mainly from Cu, Cr and Ni, but this is similar between surface and deep soils indicating that the observed high anomalies are strictly related to geogenic control. This is supported when the Cdeg is calculated using the high BTVs, which indicates low contamination. This suggests that the use of only conservative BTVs for the entire region might overestimate the significance of anthropogenic contamination; thus, we suggest the use of high BTVs for effective assessment of soil contamination in this region. The methodology and results of this study may help developing strategies for geochemical mapping in other Carajás soils or in other Amazonian soils with similar characteristics. © 2019, Springer Nature B.V.Item High resolution hydrogeochemical survey and estimation of baseline concentrations of trace elements in surface water of the Itacaiúnas River Basin, southeastern Amazonia: Implication for environmental studies(Elsevier, 2019) Sahoo, Prafulla Kumar; Dall'Agnol, R; Salomão, G.N; da, SilvaFerreira Junior J; Silva, M.S; e Souza, Filho P.W.M; Powell, M.A; Angélica, R.S; Pontes P.R; da, Costa M.F; Siqueira, J.O.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, 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-HCO3 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 (BTVs) 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 BTVs (NBTVs), considering as the least degraded with low or no significant level of anthropogenic influence; and 98th percentile provides the ambient BTVs (ABTVs), which consists of natural plus diffuse anthropogenic input in the defined area. The ABTVs 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 ABTVs 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 BTVs. 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 NO3- 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. © 2019 Elsevier B.V.