Process of generating acid mine drainage and heavy metal contamination in profiles of rebuilt soil in a coal mining area [Geração de drenagem ácida e de contaminação por metais pesados em perfis de solos construídos em área de mineração de carvão]
Bitencourt D.G.B.,Capao do Leao |
Pinto L.F.S.,Capao do Leao |
Pauletto E.A.,Capao do Leao |
Silva M.T.,Capao do Leao |
Garcia G.F.,Curso de Agronomia
Revista Brasileira de Ciencia do Solo | Year: 2015
Soils rebuilt after coal strip mining is composed of topsoil and, or, overburden, and their chemical properties differ from those of natural soils mainly due to the sulfurization process. The objective of this study was to evaluate the potential for acidification from sulfides and heavy metal contamination across profiles of soils rebuilt after coal mining, in areas of different ages, with and without concomitant environmental reclamation during mine operations. Mining areas of different ages were selected: areas I and II, without environmental reclamation during extraction and composed only from overburden, representing the oldest areas; and areas IV and VII, containing topsoil and, in some profiles, a clay layer (B and BC horizons from the natural soil) between the topsoil and the overburden, constituting the younger rebuilt mine soils. Soil pits were opened and disturbed samples were collected up to a depth of 2 m. Determinations were made of soil particle size, particle density, pH, Ca, Mg, Al, K, Na, P, H+Al, acidity potential, neutralization potential, net potential, organic C content, and electrical conductivity in saturated paste. In addition, potentially bioavailable metals were extracted by the USEPA 3050B method (Fe, Al, Mn, Ba, Cu, Zn, C, Cr, Co, Cd, Pb, Mo, As, and Se), and the results were compared to the guideline values of prevention and investigation for soils. In univariate analysis, descriptive statistics and the Kolmogorov-Smirnov test were applied. The degree of dispersion of each variable, expressed by the coefficient of variation, was qualitatively evaluated and classified as low, moderate, or high. Multivariate principal component analysis (PCA) was carried out for the constructed mine soils of areas I and II, and IV and VII, and then biplots were applied to the first principal components. The rebuilt mine soils from the oldest areas (I and II) showed lower pH (<3.2) and higher acidification potential. The topsoil and clay layers in areas IV and VII, in spite of providing favorable chemical conditions for surface vegetation, did not prevent acid mine drainage from developing in the subsurface. The sulfurization process and its relationship to release of metals was best characterized by principal component analysis performed in soils from areas IV and VII because the correlation between pH and base saturation in overburden layers is only expressed in base saturation above 40 %, which was not observed in rebuilt mine soils from areas I and II. © 2015, Revista Brasileira de Ciencia do Solo. All rights reserved.
Spatial variability structure of the surface layer attributes of gleysols from the coastal plain of rio grande do sul [Estrutura de variabilidade espacial dos atributos da camada superficial de gleissolos da planície costeira do rio grande do sul]
Bitencourt D.G.B.,Federal University of Pampa |
Timm L.C.,Federal University of Pelotas |
Guimaraes E.C.,Federal University of Uberlandia |
Pinto L.F.S.,Capao do Leao |
And 2 more authors.
Bioscience Journal | Year: 2015
The spatial variability structure of soil attributes in a certain area might influence the semivariogram fitting model and, consequently, the attribute behavior mapping in this area leading to different decisions regarding crop management. This study aimed to identify, characterize and quantify the spatial variability of chemical attributes and the clay content in the superficial layer of a Gleysoils mapping unit (MU) at reconnaissance scale in the coastal plain of Rio Grande do Sul, through descriptive statistics and geostatistics and compare the results taking into consideration the existence of three Gleysoils mapping units at semi-detailed scale through the scaled semivariogram technique. A 403 ha area located in the Rio Grande do Sul Coastal Plain, in the city of Jaguarão was sub-divided into three mapping units (GL-mo, GL-mo.lv and GL-lv), a sampling grid with 403 points, 100 m far one from another was established. In a 5 m radius around each sampling point, 10 sub-samples of disturbed soil were collected from the 0-0.20 m layer, making up a soil compound sample, and the following attributes were determined for each sample: pH in water, organic carbon, phosphorus, potassium, sodium, calcium, magnesium, aluminum, potential acidity and clay content. The cation Exchange capacity (pH=7.0) and base saturation were also calculated. The identification, characterization and quantification of the spatial variability of attributes from the soil Ap horizons were carried out through descriptive statistics and geostatistics, considering the mapping unit at the reconnaissance scale and the three units at the semi-detailed scale. In the geostatistics analysis, the scaled semivariogram technique was employed aiming to compare the spatial variability structure for each soil attribute in the total area and in the three MUs at the semi-detailed scale. Regarding the descriptive statistics, the Ap horizon attributes behavior in GL-lv was similar to that in the total area of the soil layer under analysis; however, when considering the spatial coordinates, the spatial variability structure of the GL-mo.lv attributes was the one that best described the attributes variability in the total area. The scaled semivariogram technique revealed that the spatial behavior of the attributes pH and exchangeable sodium was similar, regardless of the evaluation scale adopted or the factor used for the scaled semivariogram. © 2015 Universidade Federal de Uberlandia. All rights reserved.