Physical characterization of a constructed soil in Candiota coal mining area, RS, Brazil. 2006.

A minera????o de carv??o representa uma grande import??ncia para a economia nacional, visto que a grande escassez de energia el??trica aliada ?? menor disponibilidade de recursos h??dricos, faz com que a gera????o de energia t??rmica passe a ser um dos focos principais das possibilidades de expans??o do sistema el??trico nacional. Com isso fez-se necess??rio o aumento em larga escala da extra????o do carv??o, proporcionado um aumento consider??vel dos impactos causados ao meio ambiente. Dentre os impactos, pode-se citar a degrada????o do solo e da ??gua, a polui????o do ar, a chuva ??cida, a redu????o da biodiversidade, o deslocamento das popula????es, implicando diretamente na qualidade de vida e na sustentabilidade da popula????o da regi??o. Assim, ?? necess??rio que se cumpra a legisla????o ambiental recompondo o solo degradado pela extra????o de carv??o. Na recomposi????o da ??rea destaca-se a topogr??fica do terreno, bem como a constru????o do solo. Nessa etapa, os atributos f??sicos do solo s??o afetados negativamente, originando condi????es f??sicas inadequadas para o restabelecimento do equil??brio ecol??gico e o retorno ?? atividade produtiva. Com isso, este trabalho teve como objetivo fazer uma caracteriza????o f??sica inicial de um experimento instalado em um solo constru??do na ??rea de minera????o de carv??o de Candiota cultivado com diferentes sistemas de cobertura e comparar os resultados obtidos com os de um solo natural da frente de minera????o. Foram feitas para as seguintes avalia????es: estabilidade de agregados em diferentes classes de tamanho, di??metro m??dio ponderado, carbono org??nico, densidade do solo, porosidade total, macro/microporosidade, densidade de part??culas, distribui????o das part??culas por tamanho, argila dispersa em ??gua, resist??ncia mec??nica do solo ?? penetra????o e ??gua dispon??vel. O experimento composto pelo solo constru??do, instalado na ??rea de minera????o de Candiota ?? composto por 4 blocos casualizados, sendo cada bloco constitu??do de 7 tratamentos, sendo que cada tratamento tem 3 pontos de coleta 6 para as camadas de 0,0 - 0,10 m e 0,10 0,20 m. J?? as amostras de solo natural foram coletadas ao longo de uma transe????o de 117 metros, sendo coletadas 40 amostras, onde o espa??amento entre as amostras ?? de 3,0 metros. Os resultados obtidos mostraram que: 1) N??o foram observadas diferen??as estat??sticas nos atributos f??sicos entre os tratamentos no solo constru??do da ??rea experimental; 2) Na compara????o com o solo natural o solo constru??do apresentou menor hierarquia de agrega????o, teor de mat??ria org??nica e ??gua dispon??vel e maior teor de argila e resist??ncia mec??nica ?? penetra????o para as camadas superficial e subsuperficial; 3) O solo constru??do apresentou um maior teor de argila dispersa em ??gua e menor DMP na camada de 0,0 - 0,10 m e para a camada de 0,10 - 0,20 m uma maior densidade do solo e resist??ncia ?? penetra????o; 4) O teor de argila, o teor de carbono org??nico e a cor de matiz 2,5 YR do solo constru??do na ??rea experimental indicam que foi constru??do com horizonte B do solo natural; 5) Os valores de resist??ncia mec??nica ?? penetra????o obtidos no solo constru??do s??o em ambas camadas, superiores aos considerados limitantes (2,5 MPa) ao desenvolvimento das plantas.Coal mining has a key role for the Brazilian economy since the lack of electric energy due to a lower availability of hydric resources is a subject of major concern, therefore it has become necessary a larger scale coal extraction, which promotes a considerable increase in the impacts on the environment. Among these impacts, are the soil and the water degradation, air pollution, acid rain, biodiversity reduction, need of population resettling, which directly affects the quality of life and sustainability of the population of the region. It is thus necessary that the environmental legislation be accomplished by the reclamation of the area where the coal was extracted from, the soil being one the most affected part. In the restoration of the area, it can be pointed out the landscape recovery and the construction of the soil. In this stage the soil physical attributes are negatively affected, attaining undesired physical conditions to the reestablishment of the ecological balance and the return to productive activities. In this context, this study had the objective of characterizing the initial stage of the physical conditions of a constructed soil under a revegetating experiment and compare the results to those obtained in a natural soil located in the mining area front. The following determinations were done: aggregates stability in different size classes, mean weight diameter (MWD), organic carbon, soil bulk density, total porosity, macro/microporosity, particles density, size particle distribution, water disperse clay, mechanical resistance to penetration and available water. The experiment installed in a recent constructed site is comprised of four randomized blocks with seven treatments. In each treatment it was collected three samples in the 0.0 - 0.10 m and 0.10 0.20 m layers. The natural soil samples were collected at 40 points, 3 m apart, along a 117 m transect, in the 0.0 - 0.10 m and 0.10 0.20 m layers. The results obtained showed that: 1) There were no statistical differences in 8 the constructed soil physical attributes in the experiment treatments; 2) Compared to the natural soil, the constructed soil presented lower hierarchic aggregation, organic matter content and available water, and higher clay and mechanical resistance to penetration for both surface and subsurface layers; 3) the constructed soil presented a higher water disperse clay and a lower MWD in the 0.0-0.10 m layer and higher bulk density and mechanical resistance to penetration in the 0.10-0.20 m layer; 4) The constructed soil clay and organic carbon content, and 2.5YR hue color indicates that the soil was constructed with the B horizon of the natural soil; 5) The values of mechanical resistance to penetration obtained in the constructed soil are, in both layers, much higher than the ones considered limiting to plant root development