| 1. |
- Gustafsson, Jon Petter, et al.
(författare)
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Towards a consistent geochemical model for prediction of uranium(VI) removal from groundwater by ferrihydrite
- 2009
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Ingår i: Applied Geochemistry. - Oxford : Pergamon Press. - 0883-2927 .- 1872-9134. ; 24:3, s. 454-462
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Tidskriftsartikel (refereegranskat)abstract
- Uranium(VI), which is often elevated in granitoidic groundwaters, is known to adsorb strongly to Fe (hydr)oxides under certain conditions. This process can be used in water treatment to remove U(VI). To develop a consistent geochemical model for U(VI) adsorption to ferrihydrite, batch experiments were performed and previous data sets reviewed to optimize a set of surface complexation constants using the 3-plane CD-MUSIC model. To consider the effect of dissolved organic matter (DOM) on U(VI) speciation, new parameters for the Stockholm Humic Model (SHM) were optimized using previously published data. The model, which was constrained from available X-ray absorption fine structure (EXAFS) spectroscopy evidence, fitted the data well when the surface sites were divided into low- and high-affinity binding sites. Application of the model concept to other published data sets revealed differences in the reactivity of different ferrihydrites towards U(VI). Use of the optimized SHM parameters for U(VI)-DOM complexation showed that this process is important for U(VI) speciation at low pH. However in neutral to alkaline waters with substantial carbonate present, Ca–U–CO3 complexes predominate. The calibrated geochemical model was used to simulate U(VI) adsorption to ferrihydrite for a hypothetical groundwater in the presence of several competitive ions. The results showed that U(VI) adsorption was strong between pH 5 and 8. Also near the calcite saturation limit, where U(VI) adsorption was weakest according to the model, the adsorption percentage was predicted to be >80%. Hence U(VI) adsorption to ferrihydrite-containing sorbents may be used as a method to bring down U(VI) concentrations to acceptable levels in groundwater.
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| 2. |
- Gunnarsson, Lina-Maria, 1977, et al.
(författare)
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Comparison of six different sewage treatment processes-Reduction of estrogenic substances and effects on gene expression in exposed male fish
- 2009
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Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 407:19, s. 5235-5242
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Tidskriftsartikel (refereegranskat)abstract
- Treated sewage effluents often contain a mixture of estrogenic compounds in low concentrations. The total combined activity of these, however, may be sufficiently high to affect the reproduction of aquatic vertebrates. The introduction of advanced treatment technologies has been suggested as a way to remove micro-contaminants, including estrogenic substances. In this study, one municipal influent was treated with six different processes in parallel on a semi-large scale in order to assess their potential to reduce substances that could contribute to estrogenic effects in male fish. The effluent from a conventional, activated sludge treatment line was compared to a similarly treated effluent with a final sand-filtering step. The addition of ozonation (15 g O-3/m(3)). a moving bed biofilm reactor (MBBR) or both in combination was also evaluated. There was also a separate treatment line that was based on a membrane bioreactor. A small battery of hepatic estrogen-responsive genes was measured in the exposed fish using quantitative PCR. Concentrations of steroid estrogens and estrogenic phenols in the effluents were measured by GC-ECNI-MS. The ozonated effluents were the only tested effluents for which all measured biological effects in exposed fish were removed. Chemical data suggested that the MBBR technology was equally effective in removing the analyzed estrogens; however, elevated expression of estrogen-responsive genes suggested that some estrogenic substances were still present in the effluent. The membrane bioreactor removed most of the measured estrogens and it reduced the induction of the estrogen-responsive genes. However, fish exposed to this effluent had significantly enlarged livers. Given that the same influent was treated in parallel with a broad set of technologies and that the chemical analyses were combined with an in vivo assessment of estrogenic responses, this study provides valuable input into the assessment of advanced treatment processes for removing estrogenic substances.
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| 3. |
- García García, Sandra, 1977-
(författare)
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Generation, stability and migration of montmorillonite colloids in aqueous systems
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In Sweden the encapsulated nuclear waste will be surrounded by compacted bentonite in the granitic host rock. In contact with water-bearing fractures the bentonite barrier may release montmorillonite colloids that may be further transported in groundwater. If large amounts of material are eroded from the barrier, the buffer functionality can be compromised. Furthermore, in the scenario of a leaking canister, strongly sorbing radionuclides, can be transported by montmorillonite colloids towards the biosphere. This thesis addresses the effects of groundwater chemistry on the generation, stability, sorption and transport of montmorillonite colloids in water bearing rock fractures. To be able to predict quantities of montmorillonite colloids released from the bentonite barrier in contact with groundwater of varying salinity, generation and sedimentation test were performed. The aim is first to gain understanding on the processes involved in colloid generation from the bentonite barrier. Secondly it is to test if concentration gradients of montmorillonite colloids outside the barrier determined by simple sedimentation experiments are comparable to generation tests. Identical final concentrations and colloid size distributions were achieved in both types of tests. Colloid stability is strongly correlated to the groundwater chemistry. The impact of pH, ionic strength and temperature was studied. Aggregation kinetics experiments revealed that for colloid aggregation rate increased with increasing ionic strength. The aggregation rate decreased with increasing pH. The temperature effect on montmorillonite colloid stability is pH-dependent. At pH≤4, the rate constant for colloid aggregation increased with increasing temperature, regardless of ionic strength. At pH≥10, the aggregation rate constant decreased with increasing temperature. In the intermediate pH interval, the aggregation rate constant decreased with increasing temperature except at the highest ionic strength, where it increased. The relationship between the rate constant and the ionic strength allowed the critical coagulation concentration (CCC) for Na- and Ca-montmorillonite to be determined. In order to distinguish the contribution of physical filtration and sorption to colloid retention in transport, the different retention mechanisms were quantified. Sorption on different representative minerals in granite fractures was measured for latex colloids (50, 100, 200 nm) and montmorillonite colloids as a function of ionic strength and pH. Despite of the negative charge in mineral surfaces and colloids, sorption was detected. The sorption is correlated to the mineral point of zero charge and the zeta potential of the colloids, and increases with increasing ionic strength and decreasing pH. In transport experiments with latex colloids in columns packed with fracture filling material, the retention by sorption could clearly be seen. In particular at low flow rates, when the contact time for colloids with the mineral surfaces were the longest, sorption contributed to retention of the transport significantly. The retention of latex colloids appeared to be irreversible in contrary to the reversible montmorillonite colloid retention. Generation, stability and sorption of the montmorillonite colloids are controlled by electrostatic forces; hence, the results were in qualitative agreement with DLVO.
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| 4. |
- Åström, Mats E., et al.
(författare)
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Lanthanoid behaviour in an acidic landscape
- 2010
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Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 74:3, s. 829-845
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Tidskriftsartikel (refereegranskat)abstract
- Lanthanoids were studied in a boreal landscape where an abundance of acid sulfate soils and Histosols provide a unique opportunity to increase the understanding of flow these metals behave in acidic soils and waters and interact with soil and aqueous organic matter. In the acid sulfate soils lanthanoids are mobile as reflected in high to very high concentrations in soil water and runoff (typically a few mg 1(-1) but Lip to 12 mg 1(-1)) and abundant release by several relatively weak extractants (ammonium acetate EDTA, sodium pyrophosphate, hydroxylamine hydrochloride) applied on bulk soil. Normalisation with the lanthanoid pool in the underlying parent materials (sulphide-bearing sediments deposited in brackish-water) and soil water showed that the extensive release/retention in the acidic soil was accompanied by large, and variable, fractionation trends across the lanthanoid series. In low-order streams draining these soils, the lanthanoid concentrations were high and, as indicated by frontal ultrafiltration and geochemical modelling, largely dissolved (<1 kDa) in the form of the species LnSO(4)(+) and Ln(3+). In other moderately acidic stream waters (pH 4.3-4.6), organic complexation was predicted to be important in the <1 kDa fraction (especially for the heavy lanthanoids) and strongly dominating in the colloidal phase (1 kDa-0.45 mu m). Along the main stem of a stream in focus (catchment area of 223 km(2)), lanthanoid concentrations increased downstream, in particular during high flows, caused by a downstream increase in the proportion of acid sulfate soils which are extensively flushed during wet periods. The geochemical models applied to the colloidal Ln-organic phase were not successful in predicting the measured fractionation patterns.
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| 5. |
- Garemark, Jonas, et al.
(författare)
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Advancing Hydrovoltaic Energy Harvesting from Wood through Cell Wall Nanoengineering
- 2023
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Ingår i: Advanced Functional Materials. - : John Wiley and Sons Inc. - 1616-301X .- 1616-3028. ; 33:4
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Tidskriftsartikel (refereegranskat)abstract
- Converting omnipresent environmental energy through the assistance of spontaneous water evaporation is an emerging technology for sustainable energy systems. Developing bio-based hydrovoltaic materials further pushes the sustainability, where wood is a prospect due to its native hydrophilic and anisotropic structure. However, current wood-based water evaporation-assisted power generators are facing the challenge of low power density. Here, an efficient hydrovoltaic wood power generator is reported based on wood cell wall nanoengineering. A highly porous wood with cellulosic network filling the lumen is fabricated through a green, one-step treatment using sodium hydroxide to maximize the wood surface area, introduce chemical functionality, and enhance the cell wall permeability of water. An open-circuit potential of ≈140 mV in deionized water is realized, over ten times higher than native wood. Further tuning the pH difference between wood and water, due to an ion concentration gradient, a potential up to 1 V and a remarkable power output of 1.35 µW cm−2 is achieved. The findings in this study provide a new strategy for efficient wood power generators. © 2022 The Authors.
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| 6. |
- Cucarella Cabañas, Victor
(författare)
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Recycling Filter Substrates used for Phosphorus Removal from Wastewater as Soil Amendments
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis studied the viability of recycling filter substrates as soil amendments after being used in on-site systems for phosphorus (P) removal from wastewater. Focus was put on the materials Filtra P and Polonite, which are commercial products used in compact filters in Sweden. A prerequisite for this choice was to review filter materials and P sorption capacity. The filter substrates (Filtra P, Polonite and wollastonite tailings) were recycled from laboratory infiltration columns as soil amendments to a neutral agricultural soil and to an acid meadow soil to study their impacts on soil properties and yield of barley and ryegrass. The amendments tended to improve the yield and showed a liming effect, significantly increasing soil pH and the availability of P. In another experiment, samples of Filtra P and Polonite were equilibrated in batch experiments with the two soils in order to study the P dynamics in the soil-substrate system. Batch equilibrations confirmed the liming potential of Filtra P and Polonite and showed that improved P availability in soils was strongly dependent on substrate P concentration, phase of sorbed P, and soil type. Finally, samples of Polonite used for household wastewater treatment were recycled as soil amendments to a mountain meadow and to an agricultural field for wheat cropping. The liming effect of Polonite was confirmed under field conditions and the results were similar to those of lime for the mountain meadow soil. However, the results were quite different for the agricultural field, where Polonite did not affect soil pH or any other chemical and physical soil properties investigated and had no impact on wheat yield and quality. The results from field experiments suggested that Polonite can be safely recycled to meadows and cropping fields at rates of 5-10 ton ha-1 but long-term studies are needed to forecast the effects of accumulation.
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| 7. |
- Potting, José, et al.
(författare)
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Stakeholder participation in sustainability assessment of non-wicked problems: The case of a future seaweed industry in Sweden
- 2021
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Ingår i: Ambio. - : Springer Nature. - 0044-7447 .- 1654-7209.
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Tidskriftsartikel (refereegranskat)abstract
- Acceptance by, and cooperation with relevant stakeholders in developing new sustainability initiatives when they are generally perceived as positive, is one of the keys for successful implementation of such new sustainability initiatives later on. It is remarkable, however, that ample literature exists about involving stakeholders in research projects focusing on problems with diverging views (controversy) around facts and values (wicked problems), but there is very little literature addressing whether and how to involve relevant stakeholders in case of initiatives where diverging norms and values do not play a (substantial) role, like in sustainability assessment for a future seaweed industry. This perspectives paper addresses that gap, and explores how to design such sustainability assessment, illustrated by how stakeholder interaction influenced the assessment and its results for a future seaweed industry in Sweden, followed by a discussion whether and how a similar approach may benefit sustainability assessment of other non-wicked sustainability initiatives.
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| 8. |
- Li, Xin, et al.
(författare)
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Glycine in aerosol water droplets : a critical assessment of Köhler theory by predicting surface tension from molecular dynamics simulations
- 2011
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 11:2, s. 519-527
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Tidskriftsartikel (refereegranskat)abstract
- Aerosol particles in the atmosphere are important participants in the formation of cloud droplets and have significant impact on cloud albedo and global climate. According to the Kohler theory which describes the nucleation and the equilibrium growth of cloud droplets, the surface tension of an aerosol droplet is one of the most important factors that determine the critical supersaturation of droplet activation. In this paper, with specific interest to remote marine aerosol, we predict the surface tension of aerosol droplets by performing molecular dynamics simulations on two model systems, the pure water droplets and glycine in water droplets. The curvature dependence of the surface tension is interpolated by a quadratic polynomial over the nano-sized droplets and the limiting case of a planar interface, so that the so-called Aitken mode particles which are critical for droplet formation could be covered and the Kohler equation could be improved by incorporating surface tension corrections.
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| 9. |
- Cui, Daqing, et al.
(författare)
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Reductive immobilization of Se-79 by iron canister under simulated repository environment
- 2009
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Ingår i: Journal of Radioanalytical and Nuclear Chemistry. - : Springer Science and Business Media LLC. - 0236-5731 .- 1588-2780. ; 282:2, s. 349-354
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Tidskriftsartikel (refereegranskat)abstract
- To understand the fate of Se-79 in a repository-like environment, the interactions between iron canister surface with dissolved selenite (SeO3 (2-)) and selenate (SeO4 (2-)) in anaerobic solutions have been investigated. Se(IV) immobilization on iron surface was observed to be about 100 times faster than that of Se(VI) at same conditions. An iron surface coated with a FeCO3 layer corrosion product is more reactive than a polished iron to immobilize Se(IV) and Se(VI). The reacted iron surfaces were analysed by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS), X-ray diffraction (XRD), Raman spectrometry and micro-X-ray Absorption Spectroscopy (XAS). The result show that Se(IV) and Se(VI) were reduced and precipitated. The dominating phase was found to be FeSe2..
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| 10. |
- Kvashnina, K., et al.
(författare)
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Electron transfer during selenium reduction by iron surfaces in aqueous solution: high resolution X-ray absorption study
- 2009
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 190:012191, s. 1-4
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Tidskriftsartikel (refereegranskat)abstract
- In several designs proposed by different countries, high-level radioactive waste will be disposed in a canister with a copper outer container and a cast iron or carbon steel insert. If the iron insert comes into contact with anoxic geological water, anaerobic corrosion could take place and release fission products such as 79Se to the biosphere. This paper present studies of the long-term kinetics of selenate (SeO42-) in the presence of iron surface under anaerobic conditions by Near Edge X-ray Absorption Spectroscopy (XANES). Substantial changes in the selenium oxidation state is found and discussed in details. We assume that such behaviour corresponds to the electron transfer from iron to selenium, which couldn't take place on oxidized iron surface. When selenate was in contact with polish steel foil in groundwater solution, reduction of Se and formation of Se(II-)was found. These findings suggest that depending of corroded or oxidised iron surface, the selenium mobility in nuclear waste disposal systems will be different.
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