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1.
Chemosphere ; 341: 140028, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-37660783

RESUMO

The knowledge of the lithological context is necessary to interpret trace elements concentrations in the soil. Soil magnetic signature (χ) and soil X-ray fluorescence (XRF) are promising approaches in the study of the spatial variability of trace elements and the environmental monitoring of soil quality. This research aimed to assess the efficiency of measurements of χ and XRF sensors for spatial characterization of zinc (Zn), manganese (Mn), and copper (Cu) contents in soils of a sandstone-basalt transitional environment, using machine learning modeling. The studied area consisted of the Western Plateau of São Paulo (WPSP), with soils originating from sandstone and basalt. A total of 253 soil samples were collected at a depth of 0.0-0.2 m. The soils were characterized by particle size and chemical analysis: organic matter (OM), cation exchange capacity (CEC), ammonium oxalate-extracted iron (Feo), sodium dithionite-citrate-bicarbonate-extracted iron (Fed), and sulfuric acid-extracted iron (Fet). Hematite (Hm), goethite (Gt), kaolinite (Kt), and gibbsite (Gb) contents were obtained by X-ray diffraction (XRD). Magnetite (Mt) and maghemite (Mh) contents were obtained by soil χ, while trace elements contents were obtained by XRF and predicted by χ. Descriptive analysis, the test of means, and correlation were performed between attributes. Zn, Mn, and Cu contents were predicted using the machine learning algorithm random forest, and the spatial variability was obtained using the ordinary kriging interpolation technique. Landscape dissections influenced iron oxides, which had the highest contents in slightly dissected environments. Trace elements contents were not influenced by landscape dissections, demonstrating that lithological knowledge is necessary to characterize trace elements in soils. The prediction models developed through the machine learning algorithm random forest showed that χ can be used to characterize trace elements. The similar spatial pattern of trace elements obtained by XRF and χ measurements confirm the applicability of these sensors for mapping it under lithological and landscape transition, aiming for sustainable strategic planning of land use and occupation.


Assuntos
Oligoelementos , Raios X , Fluorescência , Brasil , Zinco , Ferro , Manganês
2.
Data Brief ; 41: 108004, 2022 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-35274030

RESUMO

Proximal soil sensing technologies, such as visible and near infrared diffuse reflectance spectroscopy (VNIR), X-ray fluorescence spectroscopy (XRF), and laser-induced breakdown spectroscopy (LIBS), are dry-chemistry techniques that enable rapid and environmentally friendly soil fertility analyses. The application of XRF and LIBS sensors in an individual or combined manner for soil fertility prediction is quite recent, especially in tropical soils. The shared dataset presents spectral data of VNIR, XRF, and LIBS sensors, even as the characterization of key soil fertility attributes (clay, organic matter, cation exchange capacity, pH, base saturation, and exchangeable P, K, Ca, and Mg) of 102 soil samples. The samples were obtained from two Brazilian agricultural areas and have a wide variation of chemical and textural attributes. This is a pioneer dataset of tropical soils, with potential to be reused for comparative studies with other datasets, e.g., comparing the performance of sensors, instrumental conditions, and/or predictive models on different soil types, soil origin, concentration range, and agricultural practices. Moreover, it can also be applied to compose soil spectral libraries that use spectral data collected under similar instrumental conditions.

3.
Sci. agric. ; 77(1): e20170430, 2020. ilus, mapas, tab
Artigo em Inglês | VETINDEX | ID: vti-24367

RESUMO

Spatial soil data applications require sound geospatial data including coordinates and a coordinate reference system. However, when it comes to legacy soil data we frequently find them to be missing or incorrect. This paper assesses the quality of the geospatial data of legacy soil observations in Brazil, and evaluates geospatial data sources (survey reports, maps, spatial data infrastructures, web mapping services) and expert knowledge as a means to fix inconsistencies. The analyses included several consistency checks performed on 6,195 observations from the Brazilian Soil Information System. The positional accuracy of geospatial data sources was estimated so as to obtain an indication of the quality for fixing inconsistencies. The coordinates of 20 soil observations, estimated using the web mapping service, were validated with the true coordinates measured in the field. Overall, inconsistencies of different types and magnitudes were found in half of the observations, causing mild to severe misplacements. The involuntary substitution of symbols and numeric characters with similar appearance when recording geospatial data was the most common typing mistake. Among the geospatial data sources, the web mapping service was the most useful, due to operational advantages and lower positional error (~6 m). However, the quality of the description of the observation location controls the accuracy of estimated coordinates. Thus, the error of coordinates estimated using the web mapping service ranged between 30 and 1000 m. This is equivalent to coordinates measured from arc-seconds to arc-minutes, respectively. Under this scenario, the feedback from soil survey experts is crucial to improving the quality of geospatial data.(AU)


Assuntos
Sistemas de Informação Geográfica , Características do Solo , Brasil
4.
Sci. agric ; 77(1): e20170430, 2020. ilus, map, tab
Artigo em Inglês | VETINDEX | ID: biblio-1497824

RESUMO

Spatial soil data applications require sound geospatial data including coordinates and a coordinate reference system. However, when it comes to legacy soil data we frequently find them to be missing or incorrect. This paper assesses the quality of the geospatial data of legacy soil observations in Brazil, and evaluates geospatial data sources (survey reports, maps, spatial data infrastructures, web mapping services) and expert knowledge as a means to fix inconsistencies. The analyses included several consistency checks performed on 6,195 observations from the Brazilian Soil Information System. The positional accuracy of geospatial data sources was estimated so as to obtain an indication of the quality for fixing inconsistencies. The coordinates of 20 soil observations, estimated using the web mapping service, were validated with the true coordinates measured in the field. Overall, inconsistencies of different types and magnitudes were found in half of the observations, causing mild to severe misplacements. The involuntary substitution of symbols and numeric characters with similar appearance when recording geospatial data was the most common typing mistake. Among the geospatial data sources, the web mapping service was the most useful, due to operational advantages and lower positional error (~6 m). However, the quality of the description of the observation location controls the accuracy of estimated coordinates. Thus, the error of coordinates estimated using the web mapping service ranged between 30 and 1000 m. This is equivalent to coordinates measured from arc-seconds to arc-minutes, respectively. Under this scenario, the feedback from soil survey experts is crucial to improving the quality of geospatial data.


Assuntos
Características do Solo , Sistemas de Informação Geográfica , Brasil
5.
Sci Total Environ ; 693: 133463, 2019 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-31376756

RESUMO

The demand for information on the soil resource to support the establishment of public policies for land use and management has grown exponentially in the last years. However, there are still difficulties to the proper use of already existing information for soil mapping. Here we aimed to establish a protocol for soil mapping using legacy data, magnetic signature and soil attributes evaluation. A total of 493 soil samples were collected at 0-0.20 m in the geological domain of Western Plateau of São Paulo State. This work has three parts: First, we performed a classification analysis using soil mapping units (SMU) extracted from conventional soil map and Support Vector Machines algorithm (SVM). As covariates, we used categorical information, such as geology, dissection and landform maps. Second, we used soil attributes to perform a cluster analysis using k-means as partitioning method. To choose the optimal number of clusters, the same number of SMU showed in the conventional soil map (e.g. 34 clusters) were used. The last step was to compare soil and clusters maps predicted by SVM with the conventional soil map. Results showed good performance of SVM for both classifications (clusters and SMU), with overall accuracy of 0.60 and 0.90 respectively. In addition, the distribution of soil attributes within each cluster was more homogeneous and well distributed than within SMU, showing that is very possible to use numerical classification for soil mapping. Future soil surveys could use cluster analysis as a preliminary evaluation for better understanding of tropical soil variations.

6.
Semina Ci. agr. ; 40(1): 99-112, Jan.-Feb. 2019. ilus, tab, graf
Artigo em Inglês | VETINDEX | ID: vti-19390

RESUMO

The aim of this study is to evaluate the spatial distribution and relationships between the physicochemical attributes and radiometry of soils with high sand contents. One hundred surface horizon samples were collected for physicochemical and spectral analyses of the soil. The samples were selected spatially by the conditioned Latin hypercube method. The physicochemical analyses consisted of granulometry, organic carbon content, and iron oxides content, extracted using sodium dithionite-citrate-bicarbonate (DCB). The spectral response of the soils was analyzed in the 400 to 1000 nm range. The spectral curves were obtained from the samples of the surface horizons, which were categorized according to the attribute in question. The relationship between the soil physicochemical attributes and soil radiometry was evaluated through a Pearson's correlation. There was a tendency for the organic carbon content to decrease with an increase in soil depth, associated with the presence of soils with higher sand contents. For soils with iron contents lower than 80 g kg <->1, there was an increase in the reflectance along the spectrum, whereas for soils with contents between 80 and 160 g kg <->1, the reflectance decreased after 600 nm, with greater variation along the spectrum for soils with iron contents higher than 120 g kg <->1. The diffuse reflectance spectroscopy could potentially allow for granulometric distinction between the soils evaluated.(AU)


Este estudo objetivou avaliar a discretização espacial e relações entre atributos físico-químicos com a radiometria dos solos com altos teores de areia. Foram coletadas 100 (cem) amostras de horizontes superficiais para análises físico-químicas e espectrais do solo, selecionadas espacialmente pelo método do hipercúbico latino condicionado. As análises físico-químicas foram a granulometria, teores de carbono orgânico e de óxidos de ferro extraído por ditionito-citrato-bicarbonato de sódio (DCB). A resposta espectral dos solos foi analisada na faixa de 400 a 1000 nm. As curvas foram elaboradas a partir da média de reflectância espectral de cem amostras de horizontes superficiais categorizados de acordo com o atributo em questão. A relação entre os atributos físico-químicos do solo e a radiometria dos solos foi avaliada através da correlação de Pearson. Houve a tendência do decréscimo nos teores de carbono orgânico com a diminuição da altitude, associada a presença de solos com maiores teores de areia. Para os solos com teores de ferro inferiores 80 g kg <->1 houve um aumento da refletância ao longo do espectro, enquanto que solos com teores entre 80 a 160 g kg <->1 a refletância decresceu significativamente após os 600 nm, com maior variação nos solos com teores de ferro superiores a 120 g kg <->1. A espectroscopia de refletância difusa mostrou-se uma ferramenta com potencial de distinção granulométrica para os solos avaliados.(AU)


Assuntos
Solos Arenosos/análise , Radiometria , Análise Espectral , Fenômenos Químicos , Características do Solo/análise , Areia , Espectroscopia de Luz Próxima ao Infravermelho
7.
Semina ciênc. agrar ; 40(1): 99-112, 2019. ilus, tab, graf
Artigo em Inglês | VETINDEX | ID: biblio-1501345

RESUMO

The aim of this study is to evaluate the spatial distribution and relationships between the physicochemical attributes and radiometry of soils with high sand contents. One hundred surface horizon samples were collected for physicochemical and spectral analyses of the soil. The samples were selected spatially by the conditioned Latin hypercube method. The physicochemical analyses consisted of granulometry, organic carbon content, and iron oxides content, extracted using sodium dithionite-citrate-bicarbonate (DCB). The spectral response of the soils was analyzed in the 400 to 1000 nm range. The spectral curves were obtained from the samples of the surface horizons, which were categorized according to the attribute in question. The relationship between the soil physicochemical attributes and soil radiometry was evaluated through a Pearson's correlation. There was a tendency for the organic carbon content to decrease with an increase in soil depth, associated with the presence of soils with higher sand contents. For soils with iron contents lower than 80 g kg


Este estudo objetivou avaliar a discretização espacial e relações entre atributos físico-químicos com a radiometria dos solos com altos teores de areia. Foram coletadas 100 (cem) amostras de horizontes superficiais para análises físico-químicas e espectrais do solo, selecionadas espacialmente pelo método do hipercúbico latino condicionado. As análises físico-químicas foram a granulometria, teores de carbono orgânico e de óxidos de ferro extraído por ditionito-citrato-bicarbonato de sódio (DCB). A resposta espectral dos solos foi analisada na faixa de 400 a 1000 nm. As curvas foram elaboradas a partir da média de reflectância espectral de cem amostras de horizontes superficiais categorizados de acordo com o atributo em questão. A relação entre os atributos físico-químicos do solo e a radiometria dos solos foi avaliada através da correlação de Pearson. Houve a tendência do decréscimo nos teores de carbono orgânico com a diminuição da altitude, associada a presença de solos com maiores teores de areia. Para os solos com teores de ferro inferiores 80 g kg


Assuntos
Análise Espectral , Fenômenos Químicos , Radiometria , Solos Arenosos/análise , Areia , Características do Solo/análise , Espectroscopia de Luz Próxima ao Infravermelho
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