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Environ Monit Assess ; 193(12): 780, 2021 Nov 08.
Artigo em Inglês | MEDLINE | ID: mdl-34748090


This study aims to determine the concentration of potentially toxic elements (PTEs) and rare earth elements (REEs) in Brazilian sandy soils under the Cerrado at the Parnaíba-São Francisco Basin transition. We also explored the geochemical correlation between these elements and pH, cation exchange capacity (CEC), total organic carbon (TOC), sand, clay, oxides from secondary minerals, and chemical index of alteration for each basin. Mineralogical, physical, and chemical analyses were used to examine PTE and REE geochemistry in six sand soil profiles from the Brazilian Cerrado. The background concentrations of these elements are low, but soils from the Parnaíba Basin have higher concentrations of PTEs than soils from the São Francisco Basin. In soils from the Parnaíba Basin, mainly Al2O3 has relevance in the V and Cr geochemistry, as these elements increase with increasing Al2O3 content. On the other hand, the REEs have CEC as a soil attribute of higher relevance in the geochemistry of those elements is soils from the Parnaíba Basin, and this relevance divides the TOC, Fe2O3, and TiO2 minerals from the clay fraction. In soils from the São Francisco Basin, the geochemistry of PTEs is possibly associated with kaolinite, especially Cu, V, and Zn. In contrast, the Ba concentration was associated with the presence of feldspar. Unlike soils from the Parnaíba Basin, the REEs do not correlate with the studied soil attributes, except for Ho and Lu. Ho had a positive association with Al2O3. Ho and Lu are negatively related to the presence of iron oxides.

Metais Terras Raras , Poluentes do Solo , Monitoramento Ambiental , Metais Terras Raras/análise , Areia , Solo , Poluentes do Solo/análise
Artigo em Inglês | MEDLINE | ID: mdl-34110527


Establishing quality reference values (QRVs) for rare earth elements (REEs) in soils is essential for the screening of these emergent contaminants. Currently, Brazil has the second-largest reserve of REEs, but data regarding background concentrations and distributions in soils remain scarce. The aim of this study was to establish the QRVs and assess the spatial distribution of REEs in soils, including REE fractionations and anomalies in (Piauí) state (251,529.186 km2), northeastern Brazil. This study reports the most detailed data on REE geochemistry in Brazilian soils. A total of 243 composite soil samples was collected at 0-20 cm depth. The mean background concentrations in soils followed the abundance of the earth's upper crust: Ce > La > Nd > Pr > Sm > Dy > Gd > Er > Yb > Eu > Tb > Lu. The ∑REEs (mg kg-1) showed the following order based on the individual mesoregions of Piauí state: Southeast (262.75) > North and Central-North (89.68) > Southwest (40.33). The highest QRVs were observed in the Southeast mesoregion. The establishment of QRVs based on the mesoregion scale improves data representativeness and the monitoring of natural REE values by identifying hot spots. Geostatistical modeling indicated significant local variability, especially in the Southeast mesoregion. The levels of these elements in this spatial zone are naturally higher than the other values across Piauí state and the mesoregion itself and indicate a high potential to exceed the QRVs. Our approach provides much needed data to help strengthen policies for both human health and environmental protection.

Environ Monit Assess ; 192(7): 453, 2020 Jun 24.
Artigo em Inglês | MEDLINE | ID: mdl-32577924


High pedological and geological variability can trigger the formation of REE hotspots, causing a need to optimize the establishment of quality reference values (QRVs). Thus, we determined the background concentrations of REEs in the soils of an emerging Brazilian state and used a combination of Moran's I and indicator kriging to identify REE hotspots and determine QRVs. A total of 100 composite soil samples was collected at a 0.20 m depth to establish background concentrations, QRVs, and spatial distribution and to elaborate probability maps for REEs. The QRVs established for soils were the following (mg kg-1): La (27.21), Ce (57.26), Pr (10.49), Nd (24.29), Sm (4.75), Eu (0.90), Gd (4.22), Tb (0.82), Dy (1.54), Ho (0.38), Er (1.23), Yb (1.07), Lu (0.24), Y (10.65), and Sc (3.70). It was possible to draw attention to the Northwest and Southwest regions of the Rio Grande do Norte (RN) state, due to the formation of REE hotspots, indicated by Moran's I, and a high tendency to exceed the QRVs, confirmed by the indicator kriging. The high background concentrations and geochemical patterns for REEs showed that a single QRV for each REE and the entire state can neglect specific environmental characteristics and misrepresent the natural geochemistry of the soil. Thus, specific QRVs were established to optimize the monitoring of natural REE values by identifying hotspot areas. The criteria established here may be useful for other groups of potentially toxic elements, provided that observations meet the requirements of the spatial autocorrelation and kriging analyses. Graphical abstract.

Metais Terras Raras/análise , Poluentes do Solo/análise , Monitoramento Ambiental , Valores de Referência , Solo
Environ Monit Assess ; 192(4): 254, 2020 Mar 29.
Artigo em Inglês | MEDLINE | ID: mdl-32222881


The Cerrado soil is under constant modification, especially because of the use of agricultural systems, which affect soil carbon (C) and phosphorus (P) functioning. Thus, the objective of this study was to determine the C and P dynamics in Brazilian Cerrado Oxisol in Piauí State under natural and anthropic conditions, considering that conservational agricultural management and no-tillage systems can restore the C and P pools in that soil. Four soil samples with distinct characteristics (native Cerrado, NC; burned native Cerrado, BNC; conventional tillage agricultural system, CTS; and no-tillage agricultural system, NTS) were collected in the study area for chemical and physical laboratory analysis. The total organic carbon (TOC) concentrations found were 33 g kg-1, 27 g kg-1, 26 g kg-1, and 20 g kg-1 for CTS, NTS, NC, and BNC, respectively. The NTS had a total nitrogen (TN) concentration of 2.0 g kg-1. The CTS had 33.4 g kg-1 of soil-oxidizable C, followed by the NTS with 27.2 g kg-1. In both studied layers, the NTS had an organic P concentration > 200 mg kg-1. The higher TOC concentration in the CTS was because of the higher content of clay in comparison with that in the NTS. The organic P in the NTS was associated with a less labile fraction of C. Thus, despite the disturbance caused by agricultural systems, the adoption of the NTS could be an influential strategy in agricultural systems to restore soil organic functioning in the Brazilian Cerrado Oxisol in Piauí State.

Agricultura/métodos , Solo , Brasil , Carbono/análise , Monitoramento Ambiental , Fósforo/análise
Arq. Inst. Biol ; 87: e0822018, 2020. tab, graf
Artigo em Inglês | ID: biblio-1100115


The soil macrofauna is fundamental for the maintenance of soil quality. The aim of this study was to characterize the soil macrofauna under different species of cover crops, including monoculture or intercropping associated to two types of soil management in the southwest region of Piauí state. The study was carried out in an Oxisol (Latossolo Amarelo, according to Brazilian Soil Classification System) in the municipality of Bom Jesus, Piauí, distributed in 30 m2 plots. Testing and evaluation of the soil macrofauna were conducted in a 9 × 2 strip factorial design, with combinations between cover crops/consortia and soil management (with or without tillage), with four replications. Soil monoliths (0.25 × 0.25 m) were randomly sampled in each plot for macrofauna at 0‒0.1, 0.1‒0.2, and 0.2‒0.3 m depth, including surface litter. After identification and counting of soil organims, the relative density of each taxon in each depth was determined. The total abundance of soil macrofauna quantified under cover crops in the conventional and no-tillage system was 2,408 ind. m-2, distributed in 6 classes, 16 orders, and 31 families. The results of multivariate analysis show that grass species in sole cropping systems and no-tillage presents higher macrofauna density, in particular the taxonomic group Isoptera. No-tillage also provided higher richness of families, where Coleoptera adult were the second more abundant group in no-tillage and Hemiptera in conventional tillage.(AU)

Os organismos da macrofauna edáfica são fundamentais para a manutenção da qualidade do solo. O objetivo deste trabalho foi caracterizar a macrofauna edáfica sob diferentes espécies de plantas de cobertura, incluindo monocultura ou cultivo consorciado associados a dois tipos de manejo do solo no sudoeste do Piauí. O estudo foi realizado em Latossolo Amarelo (Sistema Brasileiro de Classificação de Solos) no município de Bom Jesus, Piauí, distribuídos em parcelas de 30 m2. O experimento e avaliação da macrofauna edáfica foram conduzidos em um ensaio fatorial em faixas 9 × 2, com combinações entre culturas /consórcios de cobertura e manejo do solo (com ou sem preparo), com quatro repetições. Os monólitos de solo (0,25 × 0,25 m) foram retirados aleatoriamente de cada parcela, para contagem da macrofauna, nas camadas de 0‒0,1, 0,1‒0,2, e 0,2-0,3 m de profundidade, inclusive liteira de superfície. Após a identificação e contagem dos organismos, foi determinada a densidade relativa de cada táxon em cada profundidade. A abundância total da macrofauna edáfica quantificada no experimento foi de 2.408 ind.m-2, distribuídos em 6 classes, 16 ordens e 31 famílias. Os resultados da análise multivariada revelaram que espécies de gramíneas em sistemas de cultivo solteiro e plantio direto favoreceram maior densidade da macrofauna, em especial do grupo taxonômico Isoptera. A ausência de preparo também proporcionou maior riqueza de famílias, destacando-se o grupo taxonômico Coleoptera adulto em plantio direto e Hemiptera em plantio convencional.(AU)

Qualidade do Solo , Biomarcadores Ambientais , Cultivos Agrícolas , Ciências do Solo
Environ Monit Assess ; 191(8): 514, 2019 Jul 26.
Artigo em Inglês | MEDLINE | ID: mdl-31346771


Despite the rare earth elements (REEs) being considered as emerging contaminants, their natural values and possible anthropogenic enrichments in soils have not been studied well in Brazil. The intensive use of conditioners and fertilizers in agricultural frontiers from Brazilian Cerrado can increase the concentration of REE in soils of the region. In this context, the objectives of this study were to determine the natural content and establish quality reference values (QRV) for REEs in soils of a watershed from Brazilian Cerrado composed of sedimentary rocks and to evaluate the influence of agricultural cultivation and the spatial variability of these elements. Thirty and twenty-six composite soil samples were collected under native vegetation and soybean cultivation, respectively. The background concentrations followed the order (mg kg-1) Ce > Nd > La > Pr > Sm > Yb > Er > Eu > Dy. The QRVs established were as follows (mg kg-1): La (1.76), Ce (5.20), Pr (0.74), Nd (1.35), Sm (0.38), Eu (0.06), Dy (0.15), Er (0.12), and Yb (0.14). Lantanium, Ce, and Er exhibited strong spatial dependence, while Eu, Dy, and Yb showed weak or total absence of spatial dependence. The spherical model was most suitable for the spatial characteristics of REEs. The parent material, mainly characterized by soils derived from sedimentary rocks (i.e., sandstone), was the primordial source of REEs for soils and that there was no or little effect of agricultural practices on these levels. Our data reinforced the need for geochemical mapping at the watershed scale, since they are important conservation units.

Monitoramento Ambiental , Metais Terras Raras/análise , Poluentes do Solo/análise , Agricultura , Brasil , Solo/química