Atributos físicos de um substrato formado pela disposição de rejeito de beneficiamento de bauxita após uma década de recuperação ambiental

• Autor(a) principal: Guimarães, Lorena Abdalla de Oliveira Prata
• Data de Publicação: 2010
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/5453
• topic: Indicadores de qualidade do solo; Recuperação ambiental; Rejeito de bauxita; Environmental reclamation; Bauxite tailings; Indicators of soil quality; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::CIENCIA DO SOLO

The tailings from bauxite washing presents chemical, physical and biological characteristics unsuitable for revegetation, which complicates the environmental reclamation of the deposition ponds. This study was conducted in the National Forest Saracá-Taquera (ICMBio), Porto Trombetas, Oriximiná-PA, and aimed to evaluate physical changes, the content of organic matter and microbial respiration of a substrate formed by the disposal of tailing from bauxite beneficiation at Porto Trombetas - PA, after ten years of environmental reclamation. The experiment was installed in 1999 in randomized block design with three replications. Three treatments were evaluated: T1 - without seedlings planting and without application of lime and fertilizer, T2 - planting of native species and lower level of fertilization; T3 - planting of native species and higher level of fertilization. In the field were determined the penetration resistance (RP) and substrate moisture (&#952;) until 60 cm depth. In the laboratory were determined: Limiting Water Range (IHO), S index, pore distribution by diameter classes, whose classes were: > 50, 50 to 10, 10 to 0.2 and < 0.2 &#956;m; bulk density (Ds); macro (Pma) and microporosity (Pmi); total porosity (Pt); water dispersible clay (ADA); organic matter (MO) and microbial respiration (RM). The results were statistically analyzed using orthogonal contrasts and simple linear correlation. RP values for treatments T1, T2 and T3 ranged from 2.15 to 4.61, 2.29 to 4.15 and from 2.79 to 4.02 MPa, respectively. Only at a depth of 55 to 60 cm is that there was treatments significant effect, where T3 had a higher average value of RP. Treatments T2 and T3 had higher &#952; at depths of 0 to 10, 20 to 30 and 30 to 40 cm. There was no significant difference between treatments T2 and T3 for these depths. The correlation coefficient between &#952; and RP was -0.73, which demonstrates the importance of water in the attenuation of the RP. Starting from treatment T1 to treatment T3 there is displacement of the IHO to left, in other words the lowest Ds values were obtained on treatment T3. The RP value used in the calculation as limiting the IHO (3.5 MPa) was adequate for the present study, and also is recommended not only for substrates formed by tailings of beneficiation of bauxite, but also to areas in process of environmental recovery. The S index values for treatments T1, T2 and T3 were 0.059, 0.053 e 0.044, respectively. The results of the remaining physical analysis indicated that the substrate on treatment T3 showed better physical quality, especially when compared to treatment T1 contesting the S index results. So the S index was not efficient to represent the physical changes in the substrate, after ten years of reclamation. In the study of pore distribution by diameter classes, the higher contribution was due to pores with diameters less than 0.2 &#956;m where water is strongly retained. The effect of treatments T2 and T3 resulted in an increased in the pore volume in the diameter class > 50 &#956;m. These treatments differed significantly only for the class of diameter > 50 &#956;m, in which the treatment T2 presented higher volume. The average values of Ds for the substrate in treatments T1, T2 and T3 were 1.38, 1.31 and 1.13 kg dm-3, respectively. Treatments T2 and T3, compared to T1, favored an increase of Pmi, Pt, RM and MO, and reduction of Ds and ADA in the substrate. The treatment T3 showed increased on the Pmi and decreased on the Ds and Pma, compared with treatment T2. Significant effect was observed on treatment T3 on the reduction of Ds and increased Pmi, Pt, RM and MO, compared to treatment T1. The lowest values obtained for ADA in treatments T2 and T3 may be associated with higher levels of flocculant character cations associated with the effect of MO on the aggregates stabilization, reducing the clay dispersion. The MO showed significant correlation with Pmi (r = 0.80), Pt (r = 0.85) and Ds (r = -0.74). The RM showed significant correlation with Pmi (r = 0.73), Pt (r = 0.81), MO (r = 0.961) and Ds (r = -0.63). The substrate chemistry correction and the planting of tree species were fundamental to the establishment of vegetation and environmental reclamation of the tailing ponds in Porto Trombetas. The planting of native species and the application of lime and fertilizer provided higher biomass production, resulting in improvement of the substrate physical attributes, especially in the substrate that received the highest level of fertilization. New characterizations should be conducted to identify the ecological balance level that can be achieved in these areas.