| 1. |
- Qureshi, Asif, 1986-, et al.
(author)
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Effects of the co-disposal of lignite fly ash and coal mine waste rocks on AMD and leachate quality
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Other publication (other academic/artistic)abstract
- Lignite fly ash (FA) and waste rocks (WRs) were mixed in three different ratios (1:1, 1:3 and 1:5) and studied to compare the effects of adding FA on AMD generation from coal mining WRs, leachability of elements and the potential occurrence of secondary minerals. FA mixed with WRs showed significant differences in pH levels compared to previous research. The 1:1 mixture performed best of all the three mixtures in terms of pH and leachability of elements, mainly due to the higher proportion of FA in the mixture. The pH in the 1:1 mixtures varied between 3.3 – 5.1 compared to other mixtures (2.3 – 3.5). Iron and SO42- leached considerably less from the 1:1 mixture compared to the others, indicating that the oxidation of sulphides was weaker in this mixture. Aluminium leached to a high degree from all mixtures, with concentrations varying from mg L-1–g L-1. The reason behind this increase is probably the addition of FA which, due to acidic conditions and the composition of the FA, increases the availability of Al. For the same reason, high concentrations of Mn and Zn were also measured. Geochemical modelling indicates that the 1:1 mixture performs better in terms of precipitation of Al3+ minerals, whereas Fe3+ minerals precipitated more in mixtures containing less FA. These results suggest that, with time, the pores could possibly be filled with these secondary minerals and sulphate salts (followed by a decrease in sulphide oxidation), improving the pore water pH and decreasing the leachability of elements. Since grain size plays a crucial role in the reactivity of sulphides, there is a risk that the results from the leaching tests may have been influenced by crushing and milling of the WR samples.
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| 2. |
- Qureshi, Asif, 1986-, et al.
(author)
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Effects of the co-disposal of lignite fly ash and coal mine waste rocks on AMD and leachate quality
- 2019
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In: Environmental Science and Pollution Research. - : Springer. - 0944-1344 .- 1614-7499. ; 26:4, s. 4104-4115
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Journal article (peer-reviewed)abstract
- Lignite fly ash (FA) and waste rocks (WRs) were mixed in three different ratios (1:1, 1:3 and 1:5) and studied to compare the effects of adding FA on acid mine drainage generation from coal mining WRs, leachability of elements and the potential occurrence of the secondary minerals. FA mixed with WRs showed significant differences in pH levels compared to previous research. The 1:1 mixture performed best of all the three mixtures in terms of pH and leachability of elements, mainly due to the higher proportion of FA in the mixture. The pH in the 1:1 mixtures varied between 3.3 and 5.1 compared to other mixtures (2.3–3.5). Iron and SO42− leached considerably less from the 1:1 mixture compared to the others, indicating that the oxidation of sulphides was weaker in this mixture. Aluminium leached to a high degree from all mixtures, with concentrations varying from mg L−1 to g L−1. The reason behind this increase is probably the addition of FA which, due to acidic conditions and the composition of the FA, increases the availability of Al. For the same reason, high concentrations of Mn and Zn were also measured. Geochemical modelling indicates that the 1:1 mixture performs better in terms of precipitation of Al3+ minerals, whereas Fe3+ minerals precipitated more in mixtures containing less FA. These results suggest that, with time, the pores could possibly be filled with these secondary minerals and sulphate salts (followed by a decrease in sulphide oxidation), improving the pore water pH and decreasing the leachability of elements. Since grain size plays a crucial role in the reactivity of sulphides, there is a risk that the results from the leaching tests may have been influenced by crushing and milling of the WR samples.
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| 3. |
- Amofah, Lea Rastas, et al.
(author)
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Extraction of arsenic from soils contaminated with wood preservation chemicals
- 2010
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In: Soil & sediment contamination. - : Informa UK Limited. - 1532-0383 .- 1549-7887. ; 19:2, s. 142-159
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Journal article (peer-reviewed)abstract
- Three soil samples contaminated by chromated zinc arsenate (CZA) or chromated copper arsenate (CCA) were investigated in a laboratory scale to study As mobilization and to identify a chemical agent that could be used in soil washing to extract arsenic. Besides high As extraction, the cost, occupational health issues and technical aspects were considered when selecting the chemical. Arsenic is strongly bound to CZA/CCA soils; only ∼50% of the tot-As was removed from water-washed soils. High Fe or Al mobilization is not necessarily indicative of high As removal from CZA/CCA soils. A high Cu/As-ratio and a large amount of soluble Ca in the soil hampered As extraction. The high ratio can be an indication of stable Cu-arsenates in soil. Calcium can react with the extraction agent or with As during extraction. Sodium hydroxide, dithionite with citrate (and oxalate) (dithionite solutions), and oxalate with citrate were the most efficient chemicals for removing As from the soils. The disadvantages of using these strong chemicals are: a high cost (oxalate with citrate); damage to equipment (dithionite solutions); an adverse impact on occupational health (dithionite solutions); or a deterioration in soil quality after extraction (NaOH and dithionite solutons). Phosphate, solutions based on NH2OH·HCl, or citrate were not efficient in mobilizing As from the soils.
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| 4. |
- Amofah, Lea Rastas, et al.
(author)
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The influence of temperature, pH/molarity and extractant on the removal of arsenic, chromium and zinc from contaminated soil
- 2011
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In: Journal of Soils and Sediments. - : Springer Science and Business Media LLC. - 1439-0108 .- 1614-7480. ; 11:8, s. 1334-1344
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Journal article (peer-reviewed)abstract
- Purpose: Normal soil washing leave high residual pollutant content in soil. The remediation could be improved by targeting the extraction to coarser fractions. Further, a low/high extraction pH and higher temperature enhance the pollutant removal, but these measures are costly. In this study, the utility of NaOH, oxalate-citrate (OC) and dithionite-citrate-oxalate (DCO) solutions for extracting of arsenic, chromium and zinc from contaminated soil were assessed and compared. In addition the effects of NaOH concentration and temperature on NaOH extractions, and those of temperature and pH on OC and DCO extractions, were evaluated. Materials and methods: A two-level, full-factorial design with a centre point was implemented. Two factors, concentration and temperature,were evaluated in NaOH extractions, and pH and temperature for OC and DCO solutions. In all cases, the extraction temperature was 20°C, 30°C and 40°C. The studied NaOH concentrations were 0.05, 0.075 and 0.1 M. The pH in OC solutions was 3, 5 and 7, and in DCO solutions, 4.7, 6.3 and 6.7. Water-washed and medium coarse soil fraction of arsenic, chromium and zinc contaminated soil was agitated for 15 min with the extraction solution. Results and discussion: In NaOH extractions, the temperature and (less strongly) NaOH concentration significantly affected As and Cr mobilisation, but only the latter affected Zn mobilisation. Both pH and temperature significantly (and similarly) influenced As and Cr mobilisation in OC extractions, while only the pH influenced Zn mobilisation. In contrast, the extraction temperature (but not pH) influenced As, Cr and Zn mobilisation in DCO extractions. Conclusions: For all extractants, mobilisation was most efficient at elevated temperature (40°C). None of the extractants reduced the soil's As content to below the Swedish EPA's guideline value. Use of DCO is not recommended because dithionite has a short lifetime and residual arsenic contents in DCO-extracted soil are relatively high. Instead, sequential extraction with NaOH followed by OC solutions (affording significant reductions in As, Cr and Zn levels in the soil with short extraction times) at 40°C is recommended.
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| 5. |
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| 6. |
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| 7. |
- Herrmann, Inga, et al.
(author)
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Hydraulic conductivity of fly ash : sewage sludge mixes for use in landfill cover liners
- 2009
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In: Water Research. - : Elsevier BV. - 0043-1354 .- 1879-2448. ; 43:14, s. 3541-3547
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Journal article (peer-reviewed)abstract
- Secondary materials could help meeting the increasing demand of landfill cover liner materials. In this study, the effect of compaction energy, water content, ash ratio, freezing, drying and biological activity on the hydraulic conductivity of two fly ash - sewage sludge mixes was investigated using a 27-1 fractional factorial design. The aim was to identify the factors that influence hydraulic conductivity, to quantify their effects and to assess how a sufficiently low hydraulic conductivity can be achieved. The factors compaction energy and drying, as well as the factor interactions material×ash ratio and ash ratio×compaction energy affected hydraulic conductivity significantly (α = 0.05). Freezing on 5 freeze-thaw cycles did not affect hydraulic conductivity. Water content affected hydraulic conductivity only initially. The hydraulic conductivity data were modelled using multiple linear regression. The derived models were reliable as indicated by R2adjusted values between 0.75 and 0.86. Independent on the ash ratio and the material, hydraulic conductivity was predicted to be between 1.7 × 10-11 m s-1 and 8.9 × 10-10 m s-1 if the compaction energy was 2.4 J cm-3, the ash ratio between 20 and 75 % and drying did not occur. Thus, the investigated materials met the limit value for non-hazardous waste landfills of 10-9 m s-1.
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| 8. |
- Jia, Yu, et al.
(author)
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Using shrimp shells and concrete to mitigate leaching for metals from waste rock
- 2023
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In: Environmental Science and Pollution Research. - : Springer. - 0944-1344 .- 1614-7499. ; 30, s. 40825-40845
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Journal article (peer-reviewed)abstract
- The capability of shrimp shells or construction demolition concrete as amendments to immobilize elements, primarily Pb and Zn, generated from mine waste weathering, was investigated via standard batch leaching test (L/S 10 cm3/g, 24 h). The effect of the amendment was tested at waste rock-to-residue ratios 9:1, 9.5:0.5, and 9.8:0.2 (weight:weight, w/w), with seawater as leachant. The effect of freshwater vs. seawater on the leaching pattern was investigated. The elemental contents of rock varied largely. Elemental levels in shells and concrete had much lower values than waste rock. Leaching results showed that amendment in both cases had high capacity to immobilize Pb and Zn. A decrease of concrete-to-rock ratio from 1:9 to 0.2:9.8 (w/w) led to more leaching of Pb but less of Zn. Similarly, decreasing shrimp-to-rock ratio increased and decreased leaching of Pb and Zn, respectively. Increasing experimental time to 5 and 10 d in a shrimp-amended batch caused less leaching of Pb and more of Zn. Both Pb and Zn immobilization in the concrete amendment was considered due to the increase of pH by concrete amending. The Pb leaching in the present study was considered controlled primarily by a sorption process, whilst the leaching for Zn might have been influenced by other factors such as pH and DO. Pb leaching from rock was much higher in seawater than in freshwater, with same range for Zn leaching, irrespective of leachant. It showed consistence between the laboratory data and the field conditions. Calculation procedures were established for amendment to mitigate mine drainage.
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| 9. |
- Kumpiene, Jurate, et al.
(author)
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Assessment of zerovalent iron for stabilization of chromium, copper, and arsenic in soil
- 2006
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In: Environmental Pollution. - : Elsevier BV. - 0269-7491 .- 1873-6424. ; 144:1, s. 62-69
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Journal article (peer-reviewed)abstract
- Stabilization of soil contaminated with trace elements is a remediation practice that does not reduce the total content of contaminants, but lowers the amounts of mobile and bioavailable fractions. This study evaluated the efficiency of Fe(0) to reduce the mobility and bioavailability of Cr, Cu, As and Zn in a chromated copper arsenate (CCA)-contaminated soil using chemical, biochemical and biotoxicity tests. Contaminated soil was stabilized with 1% iron grit. This treatment decreased As and Cr concentrations in leachates (by 98% and 45%, respectively), in soil pore water (by 99% and 94%, respectively) and in plant shoots (by 84% and 95%, respectively). The stabilization technique also restored most of analyzed soil enzyme activities and reduced microbial toxicity, as evaluated by the BioTox test. After stabilization, exchangeable and bioaccessible fractions of Cu remained high, causing some residual toxicity in the treated soil.
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| 10. |
- Kumpiene, Jurate, et al.
(author)
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Editorial
- 2007
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In: Ambio. - 0044-7447 .- 1654-7209. ; 36:6, s. 429-
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Journal article (other academic/artistic)abstract
- During the last decades, contaminated soil has become of both public and scientific concern. National inventories have shown very large numbers of potentially contaminated sites originating from various industrial activities. Industrial technologies in the old days were often based on open systems designed without the insight of their being potential environmental threats. Legal actions taken against organizations responsible for water and air pollution have led to the development of new water and flue gas cleaning technologies. Today, contaminated land plays a major role in sustainable future land use, not only with regard to pollution resulting from old industrial activities but also with regard to the management of present industrial technologies and waste products.Issues related to contaminated soil are by definition interdisciplinary. In the Northern Sweden Soil Remediation Center (MCN), scientists from three universities (Umeå University, Luleå University of Technology, and Swedish University of Agricultural Sciences) and the Swedish Defense Research Agency (FOI) have focused on developing a detailed understanding of the mechanisms and processes in the soil system. Fundamental and applied research in collaboration with enterprises has been performed concerning critical knowledge gaps.The MCN was initiated in 2001 and consists of scientists, representatives from authorities, consultants, and entrepreneurs. The major goals of the MCN have been to increase the scientific basis for the risk assessment of contaminated soil and, by improved knowledge of the interactions between different contaminants and the soil system, to guide the development of remediation methods. New scientific results have been implemented by collaboration enterprises and authorities that have added strategic value for the whole sector in general.This issue of AMBIO summarizes the MCN's research activities, which have focused on inorganic and organic pollutant behavior, analytical methods, and risk assessments of brownfields. In addition, invited contributions from research groups outside the MCN have added other valuable aspects to the multidisciplinary research field.
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