Simulation of Contaminants Transport in Groundwater From Nickel Mining Waste Dump Southeast Sulawesi

The irregularities of nickel resource mining in Indonesia cause many serious environmental problems. Piles of leftover rocks on nickel mining waste dumps have the potential to be a source of heavy metal seepage into the water. This study was conducted to assess the impact of nickel mining in the Langgikima Subdistrict of the North Konawe Regency of Southeast Sulawesi Province. The focus is to assess the migration of hexavalent chromium (Cr6+) and iron (Fe) using MT3DMS to model the transport of solutes. The study's goal was to identify cr6+ and Fe concentrations in waste dumps and predict the spread of contaminants over a 20-year period of time. XRF (X-Ray Fluorescence) is done to determine the content of elements and minerals in rocks. Toxicity Characteristics Leaching Procedure (TCLP) is performed to estimate the concentration of Cr6+ and Fe in waste dumps. AAS (Atomic Absorption Spectrophotometer) to find out the content of Cr6+ and Fe in surface water and land water samples. The results showed the highest concentrations of Cr6+ of 0.0462 mg/L and Feat 0.8709 mg/L. Simulations without compacted clay coatings, Cr6+ and Fe contaminants could be transported consecutively by 2.7 km and 2.42 km while simulations used compacted clay layers with a hydraulic conductivity of 1 × 10−9 m/s of Cr6+ and Fe contaminants could be transported consecutively by 0.412 km and 0.467 km. It can therefore be concluded that heavy metals in the remaining rock piles from the waste dump can be transported into groundwater, and the action of using a compacted layer of clay must be taken to prevent contaminant migration into groundwater.

Determination of heavy metal elements concentration in soils and tailing sediments from lateritic nickel post-mining areas in Motui District, Southeast Sulawesi

Heavy metal elements concentration study has been determined from soils and tailing sediments in laterite nickel post-mining area in Motui District Southeast Sulawesi. This study aimed to determine the concentration of some heavy metal elements, especially Fe, Co, Mn and Cr, from surface soils sediments in waste dump sites and tailing sediments in settling ponds from lateritic nickel post-mining areas. A total of 20 samples consisting of 18 soil samples and 2 tailing sediments samples were systematically collected for the study. The soil samples from the waste dump site profile were collected from 3 layers which were divided based on the colour of the soils from top to bottom, namely Layer C, Layer D and Layer E. Six soil samples were taken from each layer with space between each sample in one layer was about 50 – 60 cm. The samples were sent to the laboratory and analysed using Atomic Absorption Spectrometer (AAS) method to determine the concentration of heavy elements. Metal-bearing minerals detected from the bedrock consists of chromite, manganese, magnetite and limonite which are responsible for the Cr, Mn and Co, and Fe content, respectively. The result showed that Fe content is significantly higher in soil samples from Layer C and tailing sediments with dark red to brown in colour, suggesting the strong relation between Fe content and colour index. The general element mobility trend showed that Mn and Co are positively correlated in soil sampling from all layers and tailing samples, whereas Fe and Cr show a negative correlation trend in Layer C, D and tailing sediments but positively correlated in Layer E.

Characterisation of the Dynamics of Leachate Contamination Plumes in the Surrounding of the Hulene - B Waste Dump, Maputo, Mozambique

The contamination of areas around solid urban waste dumps is a global challenge for the maintenance of environmental quality in large urban centres in developing countries. This study applied geophysical methods (electrical resistivity) to identify leachate contamina-tion plumes in the subsoil and groundwater, as well as to describe their temporal (2020 and 2021) dynamics in the lithology and groundwater around the Hulene - B waste dump, Maputo, Mozambique. Geophysical methods (electrical resistivity) were applied to identify possible groundwater contamination plumes, their dynamics, mechanisms of their enrichment and dispersion. Eight 400 m electrical resistivity profiles were performed, four profiles in January 2020 and four profiles in May 2021, overlapped, and the data were inverted with RES2D software. The electrical resistivity models indicate an E - W move-ment of large contamination plumes that dilute superficially into the natural surface wa-ter receiving basin and groundwater, creating zones of resistive anomalies. The thickness of the plumes in the subsurface environment was shown to be extensive in summer for profiles 1a and 2b and we associate it with the higher leachate production and migration mechanisms, which are intense in the hot and rainy season. Profile 4b showed the prop-agation of anomalous surface and subsurface areas, which was associated with higher leachate production and migration process in the new deposition zone (west). The spatial distribution of contamination plumes at both stations reduced significantly as we moved further away from the waste deposit, revealing the attenuating effect of groundwater and lithological substrate (Profile 3 a, b, and fig.7).

Geotechnical Engineering Perspectives: Challenges and Solutions in the Transition to a Post-Lignite Era

Coal and lignite regions are on the way to reinvent themselves. In this work, three aspects related to the reclamation and exploitation of these mining areas are analyzed, focusing on the role of geotechnical engineering. Firstly, the slope stability of lignite excavations is examined during the water filling reclamation practice. Secondly, the effect of extreme rainfall is studied on the slope stability of abandoned lignite mines. Finally, aspects of the potential reclamation of a waste dump by a highway or a railroad are investigated. Overall, the three studies underline the importance of geotechnical engineering in the transition to a post-lignite era.

Molecular and Stable Isotope Composition of Pollutants Emitted during Thermal Processes within the Rymer Coal Waste Dump (Upper Silesia, Poland)

Twenty-seven gases and sixteen rock wastes from the thermal active Rymer coal waste dump were collected. The composition and origin of gaseous, liquid, and solid pollutants emitted during the self-heating process and the development of these processes with time were established. Gases were subjected to determination of molecular and stable isotope (δ13C and δ2H) composition. Rock-Eval pyrolysis and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) were applied for evaluation of the quantity and molecular composition of pyrolysates released during the heating of rocks in temperatures from 100 to 650 °C. The main products of Py-GC-MS are released between 350 and 650 °C, namely alkanes, aromatic hydrocarbons, and aromatic alcohols. These components were also recorded in Py-GC-MS products of samples collected from the dump surface. Besides the high-molecular-weight organic compounds, in emitted gases CO2, CO, gaseous hydrocarbons, and S-compounds were recorded. The stable isotope data indicated that methane was generated mainly during the low-temperature thermogenic process, but a share of the microbial-originated gas was visible. The source of the CO2 was the oxidation of organic matter. The gaseous S-compounds were products of high-temperature decomposition of sulphides and organic S-compounds. The hydrocarbon and CO contents of the emitted gases proved to be good indicators for tracking of the self-heating processes.