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Abstract: Remediation of contaminated soil can be performed by using various techniques, which must be adequately tailored for each specific case. The aim of this research is to critically evaluate the potential use of red mud and paper ash and a combination of the two as immobilization additives for the remediation of contaminated soil from one of the most polluted sites in Slovenia. The proposed procedure involves the preparation of geotechnical composites made from contaminated soil and mixed with 25 wt% of immobilization additives and an optimal quantity of water to achieve consistency, at which maximum compaction according to the Proctor Compaction Test procedure can be achieved. The results reveal a positive, time-dependent trend for the immobilization of potentially toxic elements in the composite with paper ash, because of the formation of the new hydration products with potentially toxic elements. In a composite containing only red mud, potentially toxic elements were immobilized by sorption mechanisms with no general time-dependent trends. The composite with a combination of additives demonstrates the remediation characteristics of both red mud and paper ash. Using this approach excavated contaminated soil, red mud and paper ash can be successfully recycled in the proposed composites, which can be beneficially used in situ for rehabilitation of contaminated sites. Nevertheless, mobilization of some potentially toxic elements at high pHs may represent a limiting factor and has to be taken into the consideration when a combination of red mud and paper ash is used as immobilization additive.
Keywords: red mud, paper ash, contaminated soil, potentially toxic elements, geotechnical composites
Published in DiRROS: 31.08.2023; Views: 142; Downloads: 115
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Abstract: The potential environmental impact of historical mining and ore processing on stream sediments and water was studied in a small siderite iron ore deposit with diverse sulfide mineral paragenesis. The main aim was to characterize solid carriers of potentially toxic elements (PTEs) in stream sediments and mine waste, to understand their fate in fluvial systems. General mineralogy (X-ray powder diffraction) and individual solid PTE carriers (scanning electron microscopy/energy dispersive spectroscopy) were correlated with the geochemical composition of stream sediments, mine waste, and stream waters (inductively coupled plasma mass spectrometry). Primary solid PTE carriers were pyrite, chalcopyrite, sphalerite, Hg-bearing sphalerite, galena, and siderite. Slightly alkaline and oxidizing conditions in stream water promoted the transformation of primary phases into secondary PTE carriers. Fe(Mn)-oxide/oxyhydroxides were major sinks for Pb, Zn, and As. Compared to background levels, Co (14.6 ± 2.1 mg/kg), Cu (30 ± 2.9 mg/kg), Ni (32.1 ± 2.9 mg/kg), Pb (64.5 ± 16.4 mg/kg), Zn (175.3 ± 22.5 mg/kg), As (81.1 ± 63.7 mg/kg), and Hg (2 ± 0.8 mg/kg) were elevated in mining area. Mine waste contained similar PTE carriers as stream sediments, but much higher PTE contents. Prevailingly low PTE concentrations in streams, with the exception of As (1.97 ± 2.4 µg/L) and Zn (4.5 ± 5.7 µg/L), indicate the stability of PTE carriers. Environmental effects were not significant, and additional monitoring is recommended.
Keywords: environmental mineralogy, environmental geochemistry, potentially toxic elements, stream sediments, solid phases, iron ore deposit, SEM/EDS
Published in DiRROS: 16.11.2022; Views: 402; Downloads: 127
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Abstract: The EU Water Framework Directive requires the monitoring and evaluation of surface water sediment quality based on the assessment of risk posed by contamination on the biotic receptors. Floodplain sediments are important receptors of potentially toxic element (PTE) contamination from the upstream catchment areas, and floodplains host climate-sensitive riverine ecosystems and fertile agricultural areas at the same time. This study investigates the effect of PTE contamination on microbial communities in floodplain sediments and soils using the fast, inexpensive and reliable fluorescein diacetate (FDA) method in order to estimate its applicability for sediment quality monitoring and preliminary toxicity-based risk assessment. Sediment and soil samples were collected from the actively flooded alluvial plain and the river terrace areas along a 130-km stretch of the large Drava River floodplain known to be widely contaminated by historical mining, smelting and the associated industry in the upstream Alpine region. Results of detailed data analysis show that the total microbial activity represented by the measured FDA values is related to PTE (As, Cu, Zn, Cd, Pb) concentrations, but this relationship shows significant heterogeneity and depends on the spatial location and on the soil properties such as organic matter content, dissolved salt and nutrient content, and it is specific to the toxic elements. Results show that some microbe species appear to be able to adapt to the elevated PTE concentrations in toxic soil micro-environments, over time. Despite the observed heterogeneity of microbial activity, the results revealed a breakpoint in the FDA dataset around the FDA = 3 FC (fluorescein concentration) value suggesting that microbial activity is controlled by thresholds.
Keywords: potentially toxic elements, fluorescein diacetate activity, heavy metals, contamination, biological activity
Published in DiRROS: 25.08.2022; Views: 505; Downloads: 154
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Abstract: Street Dust (SD) acts as a sink and source of atmospheric particles containing Potentially Toxic Elements (PTEs) and can pose a possible pathway of PTEs to human bodies. Comprehensive SD study, where 249 samples were collected from rural, urban and industrialized areas aimed to increase the understanding between sedimentation of atmospheric dust derived from anthropogenic activities and elemental composition of SD. Elemental composition for 53 elements (ICP-MS, aqua regia digestion) was determined on fraction <0.063 mm. Significantly increased levels of Sn-Cu-Sb-Bi-Ag-Ba-Mo-Pt-Pb and other elements have been detected in urban environments, compared to the rural ones. SEM/EDS investigation identified that main carriers of Ba, Cu and Sn are most likely particles derived from non-exhaust traffic emissions. Areas around steel mills show a strong enrichment with Cr, Mo, Ni and W, which exponentially decreases with the increased distance from the plant, reaching corresponding urban background 15 and 20 km from the source. SEM/EDS inspection identified spherical and melted irregular particles as the main carriers of the above-mentioned elements. City managers shall adapt measures to reduce amount of vehicular traffic and quantity of deposited SD on the public surfaces and encourage green city planning, while industrial emitters are encouraged to reduce their dust emissions.
Keywords: ironwork, pollution, potentially toxic elements, Slovenia, traffic
Published in DiRROS: 10.06.2022; Views: 476; Downloads: 251
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Keywords: dietary reference intake, energy dispersive X-ray fluorescence spectrometry, metals, minerals, trace elements, total reflection X-ray fluorescence spectrometry
Published in DiRROS: 11.07.2017; Views: 3886; Downloads: 1289
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