Bauxite Mining Area Research Articles

Heavy Metals in Soil of the Tropical Climate Bauxite Mining Area in Malaysia

Heavy Metals in Soil of the Tropical Climate Bauxite Mining Area in Malaysia

Propagule emergence in topsoil from a high-altitude field and implications for bauxite mining area restoration

The identification of factors that influence the timing of seedling emergence in topsoil is important to improve restoration strategies in former mining areas. The aim of this study was to determine the time of emergence of seedlings present in the topsoil of high fields in the Atlantic Forest on bauxite mines in the plateau region of Pocos de Caldas, Minas Gerais, in both the dry and rainy seasons. The surface layer soil (top 5 cm) and litter were collected in August 2011 and March 2012. We collected 12 samples, consisting of 6 subsamples distributed in 3 sites (4 samples/site), from both the dry and wet periods (n = 24). The collected contents were placed in plastic trays and germination was evaluated in the greenhouse. The seedling emergence curve was adjusted. The values were submitted to analysis of variance associated with the Scott-Knott test (p < 0.05). The number of emerged seedlings and the time required for emergence to stop were lower in the rainy season than the dry season. The results show that the best time for the storage of the topsoil layer is the dry season, since it prolongs the viability of propagules and improves the success of recovery activities on mined areas. Key words: Atlantic forest, environmental restoration, emergence time, degraded areas, bauxite mining.

The occurrence and potential ecological risk assessment of bauxite mine-impacted water and sediments in Kuantan, Pahang,Malaysia

Recent bauxite mining activities in the vicinity of Kuantan, Pahang, have been associated with apparent environmental quality degradation and have raised environmental concerns among the public. This study was carried out to evaluate the overall ecological impacts on water and sediment quality from the bauxite mining activities. Water and sediment samples were collected at seven sampling locations within the bauxite mining areas between June and December 2015. The water samples were analyzed for water quality index (WQI) and distribution of major and trace element geochemistry. Sediment samples were evaluated based on geochemical indices, i.e., the enrichment factor (EF) and geoaccumulation index (I geo). Potential ecological risk index was estimated to assess the degree to which sediments of the mine-impacted areas have been contaminated with heavy metals. The results showed that WQIs of some locations were classified as slightly polluted and contained metal contents exceeding the recommended guideline values. The EFs indicated minimal to moderate enrichment of metals (Pb, Cu, Zn, Mn, As, Cd, Cr, Ni, Co, and Sr) in the sediments. I geo showed slightly to partially polluted sediments with respect to As at some locations. The potential ecological risk index (RI) showed that As posed the highest potential ecological risk with RI of 52.35-60.92 at two locations, while other locations indicated low risk. The findings from this study have demonstrated the impact of recent bauxite mining activities, which might be of importance to the local communities and relevant authorities to initiate immediate rehabilitation phase of the impacted area.

Rhizobial characterization in revegetated areas after bauxite mining.

Little is known regarding how the increased diversity of nitrogen-fixing bacteria contributes to the productivity and diversity of plants in complex communities. However, some authors have shown that the presence of a diverse group of nodulating bacteria is required for different plant species to coexist. A better understanding of the plant symbiotic organism diversity role in natural ecosystems can be extremely useful to define recovery strategies of environments that were degraded by human activities. This study used ARDRA, BOX-PCR fingerprinting and sequencing of the 16S rDNA gene to assess the diversity of root nodule nitrogen-fixing bacteria in former bauxite mining areas that were replanted in 1981, 1985, 1993, 1998, 2004 and 2006 and in a native forest. Among the 12 isolates for which the 16S rDNA gene was partially sequenced, eight, three and one isolate(s) presented similarity with sequences of the genera Bradyrhizobium, Rhizobium and Mesorhizobium, respectively. The richness, Shannon and evenness indices were the highest in the area that was replanted the earliest (1981) and the lowest in the area that was replanted most recently (2006).

Bacteria isolated from soils of the western Amazon and from rehabilitated bauxite-mining areas have potential as plant growth promoters

Several processes that promote plant growth were investigated in endophytic and symbiotic bacteria isolated from cowpea and siratro nodules and also in bacterial strains recommended for the inoculation of cowpea beans. The processes verified in 31 strains were: antagonism against phytopathogenic fungi, free-living biological nitrogen fixation, solubilization of insoluble phosphates and indole acetic acid (IAA) production. The resistance to antibiotics was also assessed. Sequencing of the partial 16S rRNA gene was performed and the strains were identified as belonging to different genera. Eight strains, including some identified as Burkholderia fungorum, fixed nitrogen in the free-living state. Eighteen strains exhibited potential to solubilize calcium phosphate, and 13 strains could solubilize aluminum phosphate. High levels of IAA production were recorded with L-tryptophan addition for the strain UFLA04-321 (42.3 μg mL⁻¹). Strains highly efficient in symbiosis with cowpea bean, including strains already approved as inoculants showed the ability to perform other processes that promote plant growth. Besides, these strains exhibited resistance to several antibiotics. The ability of the nitrogen-fixing bacteria to perform other processes and their adaptation to environmental conditions add value to these strains, which could lead to improved inoculants for plant growth and environmental quality.

Suitability evaluation for land reclamation in mining area: A case study of Gaoqiao bauxite mine

Suitability evaluation plays an important role in land reclamation because the choice of evaluation methods affects the accuracy and objectivity of the suitability evaluation results. Furthermore, it influences the decision-making related to land reclamation. An improved method, which is called limit comprehensive conditions method, was developed after different suitability evaluation methods were studied. Based on this method, the reclaimed land of the Gaoqiao bauxite mining area was evaluated. The Gaoqiao mining area was divided into seven evaluation units that were evaluated respectively by selecting evaluation factors and establishing grade standards. The results show that the proposed method is more applicable and easier to handle. Moreover, its evaluation results are more scientific compared with the traditional evaluation methods. The improved method can be beneficial to the rapid monitoring and the effective management of reclaimed land in the opencast mine area.

Fungos micorrízicos arbusculares em solos de área de mineração de bauxita em reabilitação

Apesar de a mineração de bauxita causar grandes alterações nas características do solo, com efeitos negativos nas micorrizas arbusculares, os efeitos da reabilitação de áreas mineradas sobre os fungos micorrízicos arbusculares (MA) e sua simbiose são pouco conhecidos. O objetivo deste trabalho foi avaliar a ocorrência, diversidade e eficiência dos fungos MA, em áreas de mineração de bauxita, com diferentes tipos de vegetação e idades de reabilitação. Amostras de solo da rizosfera foram coletadas para analisar o micélio fúngico extrarradicular, o número de esporos, a riqueza e diversidade de fungos MA e para avaliar a colonização micorrízica e eficiência simbiótica de populações fúngicas. A mineração afetou negativamente os fungos MA, sendo a recuperação destes mais relacionada com o tipo de vegetação do que com o tempo de reabilitação da área. Foram encontradas as espécies: Gigaspora margarita, Gigaspora sp., Paraglomus occultum, Glomus sp., Entrophospora colombiana e Acaulospora scrobiculata. A ocorrência desses fungos foi favorecida pela presença de gramíneas ede bracatinga. Embora Eucalyptus saligna não seja um bom hospedeiro para os fungos MA, quando associado a sub-bosque bem desenvolvido e diverso, contribuiu para a recuperação dos fungos. As populações fúngicas isoladas de áreas com braquiária e feijão-guandu ou de bracatinga com capim-gordura apresentaram elevada eficiência para o feijoeiro, mostrando que é possível recuperar a função deste grupo de microrganismos utilizando diferentes tipos de vegetação. Estes isolados apresentam potencial de utilização em programas de reabilitação de solos minerados.

The capacity of Jamaican mine spoils, agricultural and forest soils to nodulateMyrica cerifera, Leucaena leucocephalaandCasuarina cunninghamiana

Soils from seven sites on the island of Jamaica were assayed for the symbiotic diazotrophsFrankiaandRhizobiumusing serial dilutions. Most probable number and least squares regression methods were used to estimate each soil's capacity to nodulate nativeMyrica cerifera, exoticLeucaena leucocephalaand exoticCasuarina cunninghamiana. The sample sites included a montane forest, a slash‐and‐burn agricultural site, reclaimed bauxite mining areas, abandoned sugar cane fields, and a garden plot. None of the host plants used in the bioassay were present on the sites sampled except for scatteredL.leucocephalaon one site.Frankiacapable of nodulatingM. cerifera, which is native to Jamaican highlands, occurred at all sites sampled. NoC. cunninghamiana‐infective Frankiawas detected in soils sampled. Only soils from one site on the tropical coastal plain harbored rhizobia able to nodulateL. leucocephala(37 nodulation units cm−3 of soil). A subset of nodulatedM. ceriferaandL. leucocephalareduced acetylene to ethylene indicating nitrogenase activity. The slash‐and‐burn agricultural site, which was situated at an elevation of 200 m and possessed both high natural fertility and high soil moisture‐supplying capacity, had significantly greaterMyricainfectious capacity (1 000 nodulation units cm−3of soil) than the other sites (7−207 nodulation units cm−3of soil). A planned, paired comparison revealed that a recently cultivated sugar cane field and a recently reclaimed bauxite mining site together had significantly lessMyrica‐infectiveFrankia(4 nodulation units cm−3of soil) than a corresponding pair of sites consisting of a sugar cane field abandoned for 25 years and a bauxite mining site reclaimed 20 years before sampling (118 nodulation units cm−3of soil). Results indicate that Myrica‐infectiveFrankiais widespread in Jamaica, that the number ofMyrica‐infective Frankiaunits vary from site to site in accordance with soil type and soil history, that Jamaican sites sampled lack soilFrankiapopulations capable of nodulating a casuarina host, that rhizobial symbionts capable of nodulatingL. leucocephalamay be geographically restricted to lowlands in Jamaica, and that the occurrence ofFrankiain these soils is independent of host plant presence.

Water stress, transpiration and leaf area index in eucalypt plantations in a bauxite mining area in south-west Australia

The clearing of native forests for open cut mining for bauxite is a potential cause for severe modification of the hydrological cycle. In the Darling Range, Western Australia, jarrah (Eucalyptus marginata Sm.) woodlands are being cleared for mining and are being replaced with plantations of other eucalypts. The plantation trees, which were up to 8 years old, showed no greater water stress than those of the original forest. The leaf area index of older plantation trees was usually higher than that of the original, mature forest. Transpiration rate was estimated on twigs enclosed briefly in a transpiration chamber. Prior test showed that this method was appropriate for comparisons in field grown eucalypts. Field measurements of stratified samples showed little difference in transpiration rate per unit leaf area between plantation forests and original forests. For the last 3 months of the dry season, however, transpiration per unit area of leaves was depressed by 25% in the plantation forest.

Development of bauxite in relation to parent material near Jarrahdale, Western Australia

Abstract The relationship between well‐exposed bedrock materials and lateritic bauxite developed over them was investigated in a deep railway cutting, located within the Jarrahdale bauxite mining area in southwestern Australia. Observations in the field and chemical and quantitative mineralogical analysis indicate that the bauxite developed by lateritization in place of the underlying gneissic‐granite/meta‐quartz dolerite basement complex in a leaching environment.