| 1. |
- Bäckström, Mattias, 1974-, et al.
(författare)
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Effects of a fulvic acid on the adsorption of mercury and cadmium on goethite
- 2003
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Ingår i: Science of the Total Environment. - Amsterdam, Netherlands : Elsevier. - 0048-9697 .- 1879-1026. ; 304:1-3, s. 257-268
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Tidskriftsartikel (refereegranskat)abstract
- The effects of an aquatic fulvic acid on the pH-dependent adsorption of Hg(II) and Cd(II) to particulate goethite (a-FeOOH) were studied in batch systems. The ionic medium consisted of 0.01 M HClO and the total concentrations 4 of mercury and cadmium were maintained at 10y8 M with 203Hg and 109Cd as tracers. pH In the systems was varied in the range 3–10 by addition of HClO and NaOH.All commercial chemicals were of analytical grade or better. An 4 aquatic fulvic acid (20 ppm), previously isolated and characterised in detail, was used as a model for humic substances and its adsorption to goethite is included in this study. The adsorption of the fulvic acid (20 ppm) onto goethite decreased slowly from 90% at pH 3–7.5 to 10% at pH 10. In systems without fulvic acid the adsorption of mercury increased in a linear fashion from 10% at pH 3 to 70% at pH 10.In the presence of fulvic acid (20 ppm), the adsorption was almost quantitative in the intermediate pH range (pH 5–7), and exceeded 92% over the entire pH range. Thus, association between mercury and the fulvic acid enhanced adsorption in general although the largest impact was found at low pH.Adsorption of cadmium increased from nearly 0 to almost 100% at approximately pH 6. In the presence of fulvic acid, the adsorption increased below pH 7 and decreased above pH 7. The adsorption isotherm for mercury when the concentration was increased from 10y8 to 1.8=10y4 M showed a corresponding increase of K (lyg) up to a total concentration at 10y6 M.At higher mercury concentrations K was lowered. In the presence of fulvic acid the corresponding relationship of K was bi-modal, i.e. high values at low and intermediate concentrations of mercury. This behaviour suggests that in the absence of fulvic acid the adsorption follow the expected behaviour, i.e. adsorption sites with similar affinity for mercury. In the presence of fulvic acid, additional adsorption sites are available by the organic molecule (possibly sulfur groups) when it is associated to the goethite. The adsorption isotherm for cadmium indicates a lowering of K at 10y4 M. Cadmium had no competitive effect on mercury and vice versa. Zinc, however, affected the adsorption of cadmium but not the adsorption of mercury.
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| 2. |
- Chan, Wing Sze, et al.
(författare)
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Metal accumulations in aquatic organisms and health risks in an acid mine-affected site in South China
- 2021
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Ingår i: Environmental Geochemistry and Health. - : Springer Nature. - 0269-4042 .- 1573-2983. ; 43:11, s. 4415-4440
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Tidskriftsartikel (refereegranskat)abstract
- Metal contamination from base metal sulphide mines is a major environmental challenge that poses many ecological and health risks. We examined the metal concentrations in the Dabaoshan mine in South China in water, sediments, and aquatic organisms and their specific characteristics (i.e. size, body tissue, species, and habitat) along the Hengshi and Wengjiang River courses to assess acid mine drainage remediation efforts. Metal concentrations of arsenic, cadmium, chromium, copper, lead, nickel, thallium, and zinc were examined in tissues (i.e. gills, intestines, and muscles) of 17 freshwater species of fish, shrimps, and crabs. Metals in tissues followed the trend: intestines > gills > muscles; nearly all intestine samples exceeded the safe limits of metals analysed in this study. There is a positive correlation between distance from the mine and metal concentrations related to the flow of surface water and the habitat of aquatic organisms. The concentrations of arsenic, copper, and zinc were the highest in aquatic organisms, and the distribution was influenced by physical (distance from mine, currents, and seasonality), chemical (pH and competing ions), and biological (species, habitat, and predator-prey relation) factors. Large demersal fish and benthic fauna had higher concentrations of metals. Bioaccumulation and biomagnification of metals, as well as the high metal pollution index and target hazard quotient (arsenic, cadmium, copper, lead, thallium, and zinc), occurred in bottom feeders (C. aumtus, X. argentea) and fish belonging to higher trophic levels (P. fulvidraco, O. mossambicus). Lead and cadmium indicated the highest level of biomagnification from prey to predator. Health risks exist from the dietary intake of common aquatic species such as tilapia and carp besides crustaceans due to high arsenic, cadmium, lead, and thallium levels. Further reduction of metals is necessary to improve the effects of acid mine drainage in the catchment.
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| 3. |
- Dario, Mårten, et al.
(författare)
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Effects of cement additives on radionuclide mobility
- 2004
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Ingår i: Scientific basis for radioactive waste management XXVII. - Warrendale, Pa : Materials Research Society. - 1558997520 ; , s. 639-644
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 4. |
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| 5. |
- Dario, Mårten, 1970-
(författare)
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Metal distribution and mobility under alkaline conditions
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The adsorption of an element, expressed as its distribution between liquid (aquatic) and solid phases in the biogeosphere, largely determines its mobility and transport properties. This is of fundamental importance in the assessment of the performance of e.g. geologic repositories for hazardous elements like radionuclides. Geologic repositories for low and intermediate level nuclear waste will most likely be based on concrete constructions in a suitable bedrock, leading to a local chemical environment with pH well above 12. At this pH metal adsorption is very high, and thus the mobility is hindered. Organic complexing agents, such as natural humic matter from the ground and in the groundwater, as well as components in the waste (cleaning agents, degradation products from ion exchange resins and cellulose, cement additives etc.) would affect the sorption properties of the various elements in the waste. Trace element migration from a cementitious repository through the pH- and salinity gradient created around the repository would be affected by the presence and creation of particulate matter (colloids) that may serve as carriers that enhance the mobility. The objective of this thesis was to describe and quantify the sorption of some selected elements representative of spent nuclear fuel (Eu, Am) and other heavy metals (Zn, Cd, Hg) in a clay/cement environment (pH 10-13) and in the pH-gradient outside this environment. The potential of organic complexing agents and colloids to enhance metal migration was also investigated. It was shown that many organic ligands are able to reduce trace metal sorption under these conditions. It was not possible to calculate the effect of well-defined organic ligands on the metal sorption in a cement environment by using stability constants from the literature. A simple method for comparing the effect of different complexing agents on metal sorption is, however, suggested. The stability in terms of the particle size of suspended colloidal matter (clays and an iron hydroxide) was measured by photon correlation spectroscopy. In the absence of large amounts of organic material, the present colloids will, in most cases, not enhance metal migration in a cementitious environment due to agglomeration of the colloidal phase at high pH and salinities.
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| 6. |
- Dario, Mårten, et al.
(författare)
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Sorption of Cd to colloidal ferric hydroxides : impact of pH and organic acids
- 1997
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Ingår i: Chemical speciation and bioavailability. - 0954-2299 .- 2047-6523. ; 9:1, s. 3-14
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Tidskriftsartikel (refereegranskat)abstract
- The sorption (both ad- and desorption) of Cd to or from colloidal ferric hydroxides as a function of pH, the concentration of organic acids (acetic acid (AA), EDTA, fulvic acid (FA) and malonic acid (MA)), the precipitation procedure for the ferric hydroxide as well as the contact time were investigated in the present study. The concentrations of Cd, colloids and organic acids were chosen to be representative of natural surface waters. The ferric hydroxide were either precipitated in presence of FA or the acid was mixed with the colloids after the purification steps. The presence of FA during the precipitation of ferric hydroxide, had an impact on the size distribution of the solid phase, but it did not have any influence on the sorption behaviour of Cd. The adsorption process was found to be relatively fast and largely pH-dependent. It was fully reversible when the pH was decreased, however, with somewhat slower kinetics. The addition of up to 1 mmol L-1 AA or MA did not cause any measurable desorption of Cd, probably due to the relatively weak complexes formed between Cd(II)-ions and the anions of the acids. Thermodynamic calculations of the distribution between different soluble Cd-species indicated that EDTA and FA would form stronger complexes with Cd. This was indicated in the experiments as enhanced adsorption at low pH-values due to the adsorption of Cd(II)-organic species, and an increase in the soluble fraction at high pH-values caused by competition for Cd(II)-ions between complex forming groups on the surfaces and the soluble organic ligands.
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| 7. |
- Dario, Mårten, et al.
(författare)
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Sorption of europium on TiO2 and cement at high pH in the presence of organic ligands
- 2006
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Ingår i: Journal of Radioanalytical and Nuclear Chemistry. - : Springer Science and Business Media LLC. - 0236-5731 .- 1588-2780. ; 270:3, s. 495-505
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Tidskriftsartikel (refereegranskat)abstract
- Organic substances present in radioactive waste lower the sorption of metal ions at the high pH in cement matrices and, hence, enhance their possible migration. The aim of this study was to develop a method to compare organic substances or their degradation products with respect to what extent they affect metal sorption. Batch sorption studies were performed with cement or TiO2 as solid phase and Eu(III) as a model element for trivalent lanthanides and actinides at pH 12.5 (representative of a cement waste matrix during the first approximately 100,000 years). Different kinds of ligands were studied in a broad concentration range, e.g., organic acids, cement additives, cleaning agents and degradation products from ion-exchange resin.
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| 8. |
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| 9. |
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| 10. |
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| 11. |
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| 12. |
- Ghosh, Devanita, et al.
(författare)
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Elemental and biomarker characteristics in a Pleistocene aquifer vulnerable to arsenic contamination in the Bengal Delta Plain, India
- 2015
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Ingår i: Applied Geochemistry. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0883-2927 .- 1872-9134. ; 61, s. 87-98
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Tidskriftsartikel (refereegranskat)abstract
- An elevated level of arsenic (As) in the Indo-Gangetic delta plain aquifers has been reported since the 1990s. Organic matter (OM) present in groundwater and aquifer sediments supports the microbial communities in these aquifers. During installation of a drinking water well, 26 sediment intervals of 6 m each were retrieved up till 156 m from a Pleistocene brown sand aquifer (BSA). Grain size distribution, sequential extraction of metals and total extractable lipids were analyzed in each sample. These parameters were statistically correlated in order to establish relationship between the physical vs. inorganic and organic characteristics, and how these properties affected the distribution of As in BSAs. The aquifer sediments consisted of medium to coarse sand except the surface sediments and those at the bottom of the well, which had high clay and slit content. Arsenic (As) concentration in sediments ranged from 2 to 21 mg/kg and indicated a strong correlation with grain size. Arsenic was mostly associated with crystalline oxides and silicate-rich minerals. Arsenic showed significant correlation with Fe in all fractions, and suggests presence of pyrite bound As-bearing minerals in these sediments. The diagnostic sedimentary lipid biomarkers indicated presence of compounds derived from vascular plants and microbial cell wall. This inference was supported by various diagnostic lipid ratios. The biomarkers were abundant in surface and deeper layers, which had high clay and silt content. The BSA sediments indicated preferential preservation of n-alkanes over other functional compounds, which were more reactive and subject to degradation. The thick clay layer at 132-156 m contained visible plant fragments, and OM in this layer indicated preferential preservation of organic carbon most likely due to the absence of specific microbial communities that degraded these compounds and mobilized As. Statistical analyses indicated the influence of selective inorganic and organic components (As, Fe and fatty acids) controlling the co-distribution of various inorganic and organic components in the aquifer.
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| 13. |
- Laera, A, et al.
(författare)
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A simultaneous assessment of organic matter and trace elements bio-accessibility in substrate and digestate from an anaerobic digestion plant
- 2019
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Ingår i: Bioresource Technology. - : Elsevier. - 0960-8524 .- 1873-2976. ; 288
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Tidskriftsartikel (refereegranskat)abstract
- This study evaluates a simultaneous assessment of organic matter (OM) and trace elements (TE) bio-accessibility in substrate and digestate from a full-scale anaerobic digester by a sequential OM extraction method. Simultaneous release of TE was determined along with the extraction of different OM fractions and the effects of extracting reagents on characteristics of OM were evaluated by nuclear magnetic resonance (NMR) spectroscopy. The reagents used for sequential extraction of OM were not enough selective. However, proteins were particularly removed by 0.1 M NaOH, while 72% H2SO4 mainly extracted hemicellulose and cellulose. The OM fractionation allowed for simultaneous extraction of greater than60% of total As, Cd, Co, Fe, Mn, Ni and Zn, while the extraction was limited for Al, Cr, Cu, Mo, and Pb. In substrate, greater than50% of total As, Co, Mn and Ni and less than40% of total Fe, Zn and Mo were identified in bio-accessible fractions. In digestate, all elements demonstrated poor bio-accessibility except for As.less thanbr /greater than (Copyright © 2019 Elsevier Ltd. All rights reserved.)
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| 14. |
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| 15. |
- Maritati, Federica, et al.
(författare)
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Brief Report: Rituximab for the Treatment of Adult-Onset IgA Vasculitis (Henoch-Schonlein)
- 2018
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Ingår i: Arthritis & Rheumatology. - : WILEY. - 2326-5191 .- 2326-5205. ; 70:1, s. 109-114
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Tidskriftsartikel (refereegranskat)abstract
- ObjectiveAdult-onset IgA vasculitis (Henoch-Schonlein) (IgAV) is a rare systemic vasculitis characterized by IgA1-dominant deposits. The treatment of adult-onset IgAV is controversial and is based on the combination of glucocorticoids and immunosuppressive agents, but many patients have refractory or relapsing disease despite treatment. Rituximab (RTX) is a B cell-depleting antibody of proven efficacy in antineutrophil cytoplasmic antibody-associated vasculitis. We undertook this study to test the efficacy and safety of RTX in a multicenter cohort of patients with adult-onset IgAV. MethodsIn this multicenter observational study, we included patients with adult-onset IgAV who had received RTX either for refractory/relapsing disease or because they had contraindications to conventional glucocorticoid/immunosuppressive therapy. We analyzed the rates of remission (defined on the basis of the Birmingham Vasculitis Activity Score [BVAS]) and relapse as well as the variations over time in estimated glomerular filtration rate (GFR), proteinuria, C-reactive protein (CRP) level, BVAS, and prednisone dose. ResultsTwenty-two patients were included; their median duration of follow-up was 24 months (interquartile range 18-48 months). Sixteen patients received RTX as add-on therapy and 6 as monotherapy. Twenty patients (90.9%) achieved remission, and 7 of those 20 patients (35%) had subsequent relapse of disease. There were significant reductions in 24-hour proteinuria (P amp;lt; 0.0001), CRP level (P = 0.0005), BVAS (P amp;lt; 0.0001), and prednisone dose (P amp;lt; 0.0001) from RTX initiation through the last follow-up visit; estimated GFR remained stable. RTX was generally well tolerated. One patient died after 60 months of follow-up. ConclusionOur data suggest that RTX is an effective and safe therapeutic option for adult-onset IgAV.
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| 16. |
- Minu, Andrew, et al.
(författare)
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Temporal and spatial distribution of trace metals in the Rufiji delta mangrove, Tanzania
- 2018
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Ingår i: Environmental Monitoring & Assessment. - : SPRINGER. - 0167-6369 .- 1573-2959. ; 190:6
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Tidskriftsartikel (refereegranskat)abstract
- Spatial and temporal distribution of trace metals and their cycling is a key issue for understanding the ongoing biogeochemical processes in coastal environments. Sediment cores were collected from six different sampling locations from the Rufiji delta mangrove forests in southeastern coastal Tanzania that are perceived to be impacted by urban development and agricultural activities in the catchment, and pollution in upstream sections of the Rufiji River. The chronology and sediment accumulation rates at these sampling sites were derived based on the distribution of Pb-210(excess) method. The trace metals (As, Cd, Cr, Cu, Ni, Pb, and Zn) were sequentially extracted as per the BCR method and analyzed. The results indicate that the mass accumulation rates range from 0.40 g cm(-2) year(-1) (cores NR3 and NR4) to 1.75 g cm(-2) year(-1) (core SR1). Trace metals in the cores are mainly associated with the residual phase and their abundances in sediments are ranked as Cr amp;gt; Zn amp;gt; Ni amp;gt; Cu amp;gt; Pb amp;gt; Cd. The results imply that trace metals in the Rufiji delta mangroves are mainly of crustal origin, and they are less sensitive to weathering. Further, these metals are least available for uptake by plants and they pose limited threat to the biota.
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| 17. |
- Shakeri Yekta, Sepehr, et al.
(författare)
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Molecular characterization of particulate organic matter in full scale anaerobic digesters : An NMR spectroscopy study
- 2019
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Ingår i: Science of the Total Environment. - : ELSEVIER. - 0048-9697 .- 1879-1026. ; 685, s. 1107-1115
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Tidskriftsartikel (refereegranskat)abstract
- This study assesses the molecular characteristics of particulate organic matter (POM) in agricultural and food waste digesters and elucidates the molecular properties of the recalcitrant POM fraction, which remains in the digestate after AD process. Molecular properties of POM in influent (substrate) and effluent (digestate) of seven full-scale AD plants (three agricultural waste and four food waste digesters) were characterized and compared using solid-state (13)C( )cross-polarization magic angle spinning (CP-MAS) and solution-state H-1,C-13 heteronuclear single-quantum coherence (HSQC) nuclear magnetic resonance (NMR) spectroscopy. Comparison of the POM structural compositions of substrate and digestate from each AD plant revealed an enrichment of protein structures relative to the carbohydrates in most cases, implying a preferential degradation of the carbohydrates over proteins and/or increase of microbial biomass upon AD of agricultural and food wastes. Distinctive molecular structures of labile and recalcitrant fractions of POM, subjected to AD, were identified by comparing the NMR spectra of all substrate and digestate POM. Accordingly, the labile POM fraction in food and agricultural solid wastes is characterized by structural entities of lipids and starch-like carbohydrates, whereas recalcitrant POM structures resemble alkyl and aromatic subunits of amino acids, lignin, and polysaccharides with beta-glycosidic linkages. This information serves as a basis to further explore optimization approaches for improving AD of the underutilized POM and the fate of organic matter in digestate-amended arable lands. (C) 2018 The Authors. Published by Elsevier B.V.
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| 18. |
- Shakeri Yekta, Sepehr, 1982-, et al.
(författare)
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Pretreatment of anaerobic digester samples by hydrochloric acid for solution-state H-1 and C-13 NMR spectroscopic characterization of organic matter
- 2018
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Ingår i: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 199, s. 201-209
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Tidskriftsartikel (refereegranskat)abstract
- Pretreatment of anaerobic digester samples by hydrochloric acid (HCl) resulted in removal of Fe-based mineral and coordination compounds, attenuating their interferences with solution-state nuclear magnetic resonance (NMR) spectroscopic characterization of the solid phase organic matter. Substrate (influent) and digestate (effluent) samples from two full-scale anaerobic digesters, designated CD (co-digester) and SSD (sewage sludge digester), were investigated. Pretreatment of CD samples with 0.2-2.0 mol l(-1) HCl and pretreatment of SSD samples with 1.0-3.0 mol l(-1) HCl removed 96-100% and 76-80% of total Fe, respectively. Pretreatment declined overall paramagnetic characteristics of digestate samples, manifested by 50% (CD) and 70% (SSD) decrease in electron paramagnetic resonance signal intensities. As a result, meaningful solution-state H-1,C-13 heteronuclear single quantum coherence and H-1 NMR spectra of DMSO-d(6) soluble organic matter could be acquired. Sample pretreatment with the lowest concentration of HCl resulted in alteration of C:N ratios in solid phase, likely due to removal of labile organic and inorganic C- and N-containing compounds, while elevating the HCl concentration did not further change the C:N ratios. Furthermore, sample pretreatment increased the solubility of carbohydrates and proteins in DMSO-d(6), enabling the detection of NMR resonances from certain structural units of carbohydrates (e.g. anomeric O2CH) and proteins (e.g. CH alpha in amino acids). Both attenuation of the paramagnetic matrix as well as art enhanced solubility of carbohydrate and protein fractions of the samples in DMSO-d(6) solvent contributed to an improved molecular characterization of anaerobic digester samples by solution-state NMR analysis.
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| 19. |
- Shilla, Dativa, et al.
(författare)
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Trophodynamics and biomagnification of trace metals in aquatic food webs: The case of Rufiji estuary in Tanzania
- 2019
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Ingår i: Applied Geochemistry. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0883-2927 .- 1872-9134. ; 100, s. 160-168
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Tidskriftsartikel (refereegranskat)abstract
- Transfer of trace metals into fish of commercial value poses a public health concern. Therefore, sediments, invertebrates, and fish from three sampling sites in the Rufiji estuary were analyzed for trace metals to evaluate their concentrations and trophic transfer within estuarine food web. Stable isotopes of carbon and nitrogen were also used to study the trophic relationship between different organisms. Biomagnification of trace metals in organisms from different trophic levels was quantified and evaluated by calculating the bioaccumulation factor and biomagnification factor. Trophic magnification factor for different trace metals was determined from the slope of the regression line between trace metal concentration and the trophic level of functional groups in sampled organisms. The results indicated that As and Zn displayed trophic level-dependent accumulation in the Rufiji food webs. As and Zn increased with the trophic level, whereas Ag, As, Co, Cr, Cu, Mn, Ni, and Pb depicted an opposite trend. Food web magnification factors varied from -0.57 for Ni to 0.39 for Zn, whereas trophic magnification factor varied from 0.27 for Ni to 2.47 for Zn. Zn and Ni bioaccumulate in the food webs as indicated by a slope greater than zero, whereas the remaining trace metals are eliminated from food webs or their trophic transfer is interrupted.
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