| 1. |
- Bergknut, Magnus, et al.
(author)
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Molecular characterization of brominated persistent pollutants using extended X-ray absorption fine structure (EXAFS) spectroscopy
- 2008
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In: Analytical and Bioanalytical Chemistry. - : Springer. - 1618-2642 .- 1618-2650. ; 390:3, s. 921-928
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Journal article (peer-reviewed)abstract
- X-ray absorption fine structure (EXAFS) spectroscopy spectra were collected for three brominated persistent pollutants: 6-bromo-2,4,5-trichlorophenol (BrTriClP), pentabromophenol (PentaBrP) and 3,3',5,5'-tetrabromobisphenol A (TBBA). The substances were selected to be symmetrical (BrTriClP and TBBA) or asymmetrical (PentaBrP) with respect to the atomic Br positions and to differ in the number of bromine and other halide atoms, as well as their relative positions. The asymmetrical PentaBrP was modelled with special detail as not all bromine atoms have identical coordination environments. The studied substances displayed unique EXAFS spectra, which could be used to determine the molecular structure in fair detail. We conclude that EXAFS spectroscopy is a suitable technique for molecular characterization of the comparatively complex molecules within the class of compounds of brominated organic persistent pollutants. A detailed understanding of the EXAFS spectra of the pure compounds opens up possibilities to study the interactions with soil and sediment matrices by means of EXAFS spectroscopy. Figure Brominated organic persistent pollutants are characterized by EXAFS spectroscopy.
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| 2. |
- Bishop, Kevin, et al.
(author)
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The Effects of Forestry on Hg Bioaccumulation in Nemoral/Boreal Waters and Recommendations for Good Silvicultural Practice
- 2009
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In: Ambio. - : Royal Swedish Academy of Sciences. - 0044-7447 .- 1654-7209. ; 38:7, s. 373-380
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Journal article (peer-reviewed)abstract
- Mercury (Hg) levels are alarmingly high in fish from lakes across Fennoscandia and northern North America. The few published studies on the ways in which silviculture practices influence this problem indicate that forest operations increase Hg in downstream aquatic ecosystems. From these studies, we estimate that between one-tenth and one-quarter of the Hg in the fish of high-latitude, managed forest landscapes can be attributed to harvesting. Forestry, however, did not create the elevated Hg levels in the soils, and waterborne Hg/MeHg concentrations downstream from harvested areas are similar to those from wetlands. Given the current understanding of the way in which silviculture impacts Hg cycling, most of the recommendations for good forest practice in Sweden appear to be appropriate for high-latitude regions, e.g., leaving riparian buffer zones, as well as reducing disturbance at stream crossings and in moist areas. The recommendation to restore wetlands and reduce drainage, however, will likely increase Hg/MeHg loadings to aquatic ecosystems
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| 3. |
- Björn, Erik, et al.
(author)
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Recent Advances in Mercury Speciation Analysis with Focus on Spectrometric Methods and Enriched Stable Isotope Applications
- 2007
-
In: Ambio. - 0044-7447 .- 1654-7209. ; 36:6, s. 443–51-
-
Journal article (peer-reviewed)abstract
- This paper discusses some recent advances in spectrometric methods and approaches for mercury speciation analysis of environmental samples with focus on isotope dilution techniques for determination of mercury species' concentrations in gaseous samples and reaction rates in soils and sediments. Such analytical data is important inter alia in fundamental research on mercury biogeochemistry and for risk assessments of mercury-contaminated soils and sediments and for designing effective remedial actions. The paper describes how the use of enriched stable isotope tracers in mercury speciation analysis can improve the traceability and accuracy of results, facilitate rational method developments, and be useful for studying biogeochemical processes, i.e. rate of reactions and fluxes, of mercury species. In particular the possibilities to study and correct for unwanted species transformation reactions during sample treatment and to study “natural” transformations of species in environmental samples, or micro- and mesocosm ecosystems, during incubations are highlighted. Important considerations to generate relevant data in isotope tracer experiments as well as reliability and quality assurance of mercury speciation analysis in general are also discussed.
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| 4. |
- Drott, Andreas, et al.
(author)
-
Do Potential Methylation Rates Reflect Accumulated Methyl Mercury in Contaminated Sediments?
- 2008
-
In: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 42:1, s. 153-158
-
Journal article (peer-reviewed)abstract
- Relationships between the short-term mono-methyl mercury (MeHg) production, determined as the specific, potential methylation rate constant Km (day−1) after 48 h of incubation with isotope-enriched 201Hg(II) at 23 °C, and the long-term accumulation of ambient MeHg, were investigated in contaminated sediments. The sediments covered a range of environments from small freshwater lakes to large brackish water estuaries and differed with respect to source and concentration of Hg, salinity, primary productivity, quantity and quality of organic matter, and temperature climate. Significant (p < 0.001), positive relationships were observed between Km (day−1) and the concentration of MeHg normalized to total Hg (%MeHg) for surface sediments (0–10, 0–15, and in one case 0–20 cm) across all environments, and across subsets of organic and minerogenic freshwaters. This suggests that the methylation process (MeHg production) overruled demethylation and net transport processes in the surface sediments. The lack of a relationship between Km and %MeHg in two brackish water sediment depth profiles (0–100 cm) indicates that demethylation and the net effect of input−output are relatively more important at greater depths. Differences in the primary production and subsequent availability of easily degradable organic matter (serving as electron donor for methylating bacteria) was indicated to be the most important factor behind observed differences in %MeHg and Km among sites. In contrast, concentrations of sulfate were not correlated to Km, %MeHg, or absolute concentrations of MeHg. We conclude that total concentrations of Hg are of importance for the long-term accumulation of MeHg, and that %MeHg in surface sediments can be used as a proxy for the rate of methylation, across a range of sites from different environments.
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| 5. |
- Drott, Andreas, et al.
(author)
-
Effects of oxic and anoxic filtration on determined methyl mercury concentrations in sediment pore waters
- 2007
-
In: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 103, s. 76-83
-
Journal article (peer-reviewed)abstract
- Accurate determination of methyl mercury (MeHg) concentrations in sediment pore waters is crucial for an improved understanding of mercury (Hg) biogeochemistry, and for improved risk assessment of Hg contaminated sites. In the present study, effects of oxic (air) and anoxic (N2) filtration (after centrifugation) on determined pore water MeHg concentrations were investigated in severely Hg contaminated pulp fibre sediments from two estuaries of the Bothnian Sea, Sweden. MeHg was determined in the filtrate using species-specific isotope dilution gas chromatography inductively coupled plasma mass spectrometry (SSID–GC–ICPMS), after ethylation with sodium tetraethylborate. Determined concentrations of MeHg were greater after anoxic filtration than after oxic filtration for all samples investigated, with MeHg(N2)/MeHg(air) ratios ranging between 3.4 and 343. Adsorption to newly formed Fe(III)/Mn(III/IV)-oxy/hydroxide surfaces is proposed as the main mechanism responsible for MeHg removal during oxic filtration. This is supported by decreases in dissolved Fe and Mn concentrations during oxic filtration, and by decreases in dissolved sulphur concentrations during oxic filtration in the samples with largest effect on MeHg concentrations. The latter is explained by adsorption of SO42− to newly formed Fe(III)/Mn(III/IV)-oxy/hydroxide surfaces. The effect of oxidation during filtration on pore water MeHg concentrations was largest in samples in which FeS(s) was not present, but with calculated pe-values below − 3. Thus, our results indicate that the largest errors with respect to pore water MeHg concentrations when filtering in air can be expected in samples with an intermediate redox potential, possibly buffered by a mixture of oxidation sensitive Fe(II/III) minerals.
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| 6. |
- Drott, Andreas, et al.
(author)
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Importance of Dissolved Neutral Mercury Sulfides for Methyl Mercury Production in Contaminated Sediments
- 2007
-
In: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 41:7, s. 2270-6
-
Journal article (peer-reviewed)abstract
- Biotic transformation of inorganic mercury, Hg(II), to mono methyl mercury (MeHg) is proposed to be largely controlled by passive uptake of neutral Hg complexes by sulfate reducing bacteria (SRB). In this study, the chemical speciation of Hg(II) in seven locally contaminated sediments covering environments such as (i) brackish water, (ii) low-productivity freshwater, and, (iii) high-productivity freshwater was related to potential Hg methylation rates, determined by incubation at 23 C for 48 h under N2(g), and to total MeHg concentrations in sediments. Pore water speciation was modeled considering Hg complexes with halides, organic thiols [Hg(SR)2(aq), associated to dissolved organic matter], monosulfides, and bisulfides. The sum of neutral mercury sulfides [Hg(SH)20(aq)] and [HgS0(aq)] was significantly, positively (p < 0.001, n = 20) correlated to the specific methylation rate constant (Km, day-1) at depths of 5-100 cm in two brackish water sediments. Total Hg, total mercury sulfides or Hg(SR)2(aq) in pore water gave no significant relationships with Km. In two sub-sets of freshwater sediments, neutral mercury sulfides were positively correlated to total Hg in pore water, and therefore, total Hg also gave significant relationships with Km. The sum of [Hg(SH)20(aq)] and [HgS0(aq)] was significantly, positively correlated to total sediment MeHg (g kg-1) in brackish waters (p < 0.001, n = 23), in southern, high-productivity freshwaters (p < 0.001, n = 20), as well as in northern, low-productivity freshwater (p = 0.048, n = 6). The slopes (b, b') of the relationships Km (day-1) = a + b([Hg(SH)20(aq)] + [HgS0(aq)]) and MeHg (g kg-1) = a' + b'([Hg(SH)20(aq)] + [HgS0(aq)]) showed an inverse relationship with the C/N ratio, supposedly reflecting differences in primary production and energy-rich organic matter availability among sites. We conclude that concentrations of neutral inorganic mercury sulfide species, together with the availability of energy-rich organic matter, largely control Hg methylation rates in contaminated sediments. Furthermore, Hg(SH)20(aq) is suggested to be the dominant species taken up by MeHg producing bacteria in organic-rich sediments without formation of HgS(s).
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| 7. |
- Drott, Andreas, et al.
(author)
-
Potential demethylation rate determinations in relation to concentrations of MeHg, Hg and pore water speciation of MeHg in contaminated sediments
- 2008
-
In: Marine Chemistry. - : Elsevier. - 0304-4203 .- 1872-7581. ; 112:1-2, s. 93-101
-
Journal article (peer-reviewed)abstract
- Specific, potential demethylation rate constants (kd, day− 1) were determined in fresh and brackish water sediments from seven different sites in Sweden originally contaminated with either Hg0(l) or phenyl-Hg. Variations in kd among and within sites were related to ambient concentrations of Hg (1–1143 nmol g− 1) and MeHg (4.4–575pmol g− 1), and to pore water speciation of MeHg. Chemical speciation modeling revealed that MeHgSH(aq), MeHgS−(aq) and MeHg–thiol complexes [MeHgSR(aq)] associated to dissolved organic matter were the dominant MeHg species in the sediment pore water at all sites. Potential rates of MeHg demethylation were determined as the decomposition of isotopically enriched Me204HgCl during 48 h of incubation in darkness under N2(g) at 23 °C. There was a significant (p < 0.001) positive relationship between ambient MeHg concentrations in sediments and kd across all sites, but no significant relationship between ambient Hg and kd. At the three sites with the highest ambient Hg concentrations in sediments (average ± SD, 185 ± 249 nmol g− 1), kd was not significantly correlated with pore water MeHg speciation. At sites with lower concentrations of ambient Hg in sediments (average ± SD, 11 ± 8.4 nmol g− 1), there was a significant (p = 0.02) positive relationship between calculated concentrations of MeHgSH(aq), MeHgS−(aq), or the sum of these two species, and kd. If it is assumed that an oxidative demethylation process dominated at sites with lower concentrations of ambient Hg in sediments, the results suggest that it may be dependent on a passive uptake of inorganic MeHgSH molecules. It was shown that additions of different amounts of MeHg and Hg tracers, in relation to the ambient concentrations of MeHg and Hg, could result in dramatically different kd values within and between sites. At one brackish water site, both absolute demethylation rates and kds were significantly, inversely related to ambient concentrations of MeHg (and Hg). In contrast, at another brackish water site with generally less kds, samples with low ambient MeHg experienced toxic effects and demethylation was not detected. This implies that added (and possibly ambient) MeHg/Hg, depending on the environmental conditions, may have either stimulating or inhibitory effects on demethylation processes.
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| 8. |
- Eriksson, Johan, et al.
(author)
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Aniline and 2,4,6-trinitrotoluene associate preferentially to low molecular weight fractions of dissolved soil organic matter
- 2009
-
In: Environmental Pollution. - : Elsevier BV. - 0269-7491 .- 1873-6424. ; 157, s. 3010-3015
-
Journal article (peer-reviewed)abstract
- Aniline and 2,4,6-trinitrotoluene (TNT) were equilibrated with particulate (POM) and dissolved organic matter (DOM) from an organic soil at different compositions of adsorbed major cations (Na, Al) and pH (aniline: 3.7-5.1, TNT: 4.8-5.0). After separation of POM, concentrations of (14)C-labelled aniline and TNT* (including TNT degradation products) were determined in DOM size fractions using size-exclusion chromatography (SEC) and UV-detection. Concentrations in the <3.5 kDa size fraction were 2.8-6.0 and 8.5-9.5 times higher for aniline and TNT*, respectively, as compared to the >40 kDa fraction. Thus, both aniline and TNT* were preferentially associated to the smallest DOM size fraction. The significant binding to DOM (similar extent as to POM) and the fact that the <3.5 kDa DOM fraction was less susceptible to flocculation by major metals suggests that the mobility of aniline and TNT is highly affected by the solubility of soil organic matter. (C) 2009 Elsevier Ltd. All rights reserved.
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| 9. |
- Frankki, Sofia, et al.
(author)
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Mobility of Chloroaromatic Compounds in Soil: Case Studies of Swedish Chlorophenol-contaminated Sawmill Sites
- 2007
-
In: AMBIO: A Journal of the Human Environment. ; 36:6, s. 452–7-
-
Journal article (peer-reviewed)abstract
- This paper summarizes recent studies on the environmental fate of chloroaromatic compounds in chlorophenol (CP)-contaminated soil and groundwater at Swedish sawmill sites. Relative proportions of CPs, polychlorinated phenoxy phenols (PCPPs), polychlorinated diphenyl ethers (PCDEs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) were determined in preservatives, particulate organic matter (POM), dissolved organic matter (DOM), groundwater, and particles filtered from groundwater. All compound classes were found in the different compartments. The fraction of PCPPs, PCDEs, PCDDs, and PCDFs had increased in the soil samples relative to the proportions in the preservatives. This increase showed correlation with the hydrophobicity, that is, PCDDs had the largest increase. Similar correlation was found between hydrophobicity and the importance of partitioning to POM over DOM. The more water soluble compound group, CP, was found equally distributed between POM and DOM. For PCPPs, PCDEs, PCDDs, and PCDFs, the relative partitioning to POM increased with increased hydrophobicity. Despite the relative partitioning towards POM, compared with DOM, cotransport with DOM and suspended colloidal fractions was found to substantially increase the transport of these compounds in the groundwater samples.
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| 10. |
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| 11. |
- Frankki, Sofia, et al.
(author)
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Partitioning of CPs, PCDEs, and PCDD/Fs between particulate and experimentally
- 2006
-
In: Environmental Science & Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 40:21, s. 6668-73
-
Journal article (peer-reviewed)abstract
- We determined the distribution of hydrophobic organic contaminants (HOCs) to fractions of natural organic matter in a soil contaminated by chlorophenol wood preservatives more than 30 years ago. The concentration of dissolved organic matter (DOM) was enhanced in soil suspensions by raising pH to 6.8-9.1. After 48 h of desorption/equilibration, the DOM fraction was separated from the particulate organic matter (POM) of the soil by filtration. In the next step, DOM was flocculated by Al-nitrate, and free concentrations of HOCs were determined in the aqueous phase. The HOCs associated with DOM and POM were extracted with toluene. No significant differences in gross carbon chemistry were detected between DOM and POM, using X-ray photoelectron spectroscopy (XPS). Normalized to organic C, chlorophenols (CPs) showed a similar degree of partitioning between DOM and POM, whereas the partitioning of polychlorinated diphenyl ethers (PCDEs), polychlorinated dibenzo-p-dioxins, and furans (PCDD/Fs) was highly shifted toward POM. The partitioning to POM, relative to DOM, increased in the order PCDE < PCDF < PCDD, reflecting the hydrophobicity of the compounds.
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| 12. |
- Frankki, Sofia, et al.
(author)
-
Partitioning of CPs, PCDEs, and PCDD/Fs between particulate and experimentally enhanced dissolved natural organic matter in a contaminated soil.
- 2006
-
In: Environmental Science and Technology. - : American Chemical Society. - 0013-936X .- 1520-5851. ; 40:21, s. 6668-73
-
Journal article (peer-reviewed)abstract
- We determined the distribution of hydrophobic organic contaminants (HOCs) to fractions of natural organic matter in a soil contaminated by chlorophenol wood preservatives more than 30 years ago. The concentration of dissolved organic matter (DOM) was enhanced in soil suspensions by raising pH to 6.8-9.1. After 48 h of desorption/equilibration, the DOM fraction was separated from the particulate organic matter (POM) of the soil by filtration. In the next step, DOM was flocculated by Al-nitrate, and free concentrations of HOCs were determined in the aqueous phase. The HOCs associated with DOM and POM were extracted with toluene. No significant differences in gross carbon chemistry were detected between DOM and POM, using X-ray photoelectron spectroscopy (XPS). Normalized to organic C, chlorophenols (CPs) showed a similar degree of partitioning between DOM and POM, whereas the partitioning of polychlorinated diphenyl ethers (PCDEs), polychlorinated dibenzo-p-dioxins, and furans (PCDD/Fs) was highly shifted toward POM. The partitioning to POM, relative to DOM, increased in the order PCDE < PCDF < PCDD, reflecting the hydrophobicity of the compounds.
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| 13. |
- Karlsson, Torbjörn, et al.
(author)
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Complexation of cadmium to sulfur and oxygen functional groups in an organic soil
- 2007
-
In: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037. ; 71, s. 604-14
-
Journal article (peer-reviewed)abstract
- Cadmium (Cd) is a toxic trace element and due to human activities soils and waters are contaminated by Cd both on a local and global scale. It is widely accepted that chemical interactions with functional groups of natural organic matter (NOM) is vital for the bioavailability and mobility of trace elements. In this study the binding strength of cadmium (Cd) to soil organic matter (SOM) was determined in an organic (49% organic C) soil as a function of reaction time, pH and Cd concentration. In experiments conducted at native Cd concentrations in soil (0.23 μg g−1 dry soil), halides (Cl, Br) were used as competing ligands to functional groups in SOM. The concentration of Cd in the aqueous phase was determined by isotope-dilution (ID) inductively-coupled-plasma-mass-spectrometry (ICP-MS), and the activity of Cd2+ was calculated from the well-established Cd–halide constants. At higher Cd loading (500–54,000 μg g−1), the Cd2+ activity was directly determined by an ion-selective electrode (ISE). On the basis of results from extended X-ray absorption fine structure (EXAFS) spectroscopy, a model with one thiolate group (RS−) was used to describe the complexation (Cd2+ + RS− two left arrows CdSR+; log KCdSR) at native Cd concentrations. The concentration of thiols (RSH; 0.047 mol kg−1 C) was independently determined by X-ray absorption near-edge structure (XANES) spectroscopy. Log KCdSR values of 11.2–11.6 (pKa for RSH = 9.96), determined in the pH range 3.1–4.6, compare favorably with stability constants for the association between Cd and well-defined thiolates like glutathione. In the concentration range 500–54,000 μg Cd g−1, a model consisting of one thiolate and one carboxylate (RCOO−) gave the best fit to data, indicating an increasing role for RCOOH groups as RSH groups become saturated. The determined log KCdOOCR of 3.2 (Cd2+ + RCOO− two left arrows CdOOCR+; log KCdOOCR; pKa for RCOOH = 4.5) is in accordance with stability constants determined for the association between Cd and well-defined carboxylates. Given a concentration of reduced sulfur groups of 0.2% or higher in NOM, we conclude that the complexation to organic RSH groups may control the speciation of Cd in soils, and most likely also in surface waters, with a total concentration less than 5 mg Cd g−1 organic C.
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| 14. |
- Karlsson, Torbjörn, et al.
(author)
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Complexation of Copper(II) in Organic Soils and in Dissolved Organic Matter - EXAFS Evidence for Chelate Ring Structures
- 2006
-
In: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 40:8, s. 2623-8
-
Journal article (peer-reviewed)abstract
- Associations with functional groups of natural organic matter (NOM) are of great importance for bioavailability, toxicity, and mobility of trace metals in soils and waters. In this study, the coordination chemistry of copper, Cu(II), in organic soils and dissolved organic matter (DOM) from soils and streams was investigated by extended X-ray absorption fine structure (EXAFS) spectroscopy. In both soil organic matter (SOM) and DOM (990-11 000 g Cu g-1 dry weight, pH 2.8-6.3), Cu(II) was coordinated by 4 oxygen/nitrogen (O/N) atoms at a distance of 1.92-1.95 Å in the first coordination shell. These four atoms are positioned in the equatorial plane of a Jahn-Teller distorted octahedron. In samples with a pH of 4.8-6.3, a second coordination shell with 2.0-3.8 C atoms was located at a distance of 2.76-2.86 Å. A significant improvement (19-39%) of the fit was obtained by including a third coordination shell with 2.0-3.8 O/C atoms involved in single scattering at an average distance of 3.69 Å and multiple scattering at an average distance of 4.19 Å. Our results provide evidence for inner-sphere complexation of Cu(II) in NOM and suggest that Cu(II) is complexed by either one or two five-membered chelate rings involving possible combinations of amino, carboxyl, or carbonyl functional groups. Ion activity measurements showed that less than 0.2% of total Cu was in the form of free Cu2+ in our samples at pH 4.8-6.3.
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| 15. |
- Karlsson, Torbjörn, et al.
(author)
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Extended X-ray absorption fine structure spectroscopy evidence for the complexation of cadmium by reduced sulfur groups in natural organic matter
- 2005
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In: ENVIRONMENTAL SCIENCE & TECHNOLOGY. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 39:9, s. 3048-55
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Journal article (peer-reviewed)abstract
- It is widely accepted that the bioavaiiability, toxicity, and mobility of trace metals are highly dependent on complexation reactions with functional groups in natural organic matter (NOM). In this study, the coordination chemistry of Cd in NOM was investigated by extended X-ray absorption fine structure spectroscopy. Soil organic matter (SOM) from different types of organic soils and dissolved organic matter (DOM) from an organic and a mineral soil horizon of a Spodosol and aquatic DOM from Suwannee River were investigated. In SOM samples (1000-25000 mu g of Cd g(-1), pH 4.6-6.6), Cd was coordinated by 1.0-2.5 S atoms at a distance of 2.49-2.55 angstrom and by 3.0-4.5 O/N atoms at a distance of 2.22-2.25 angstrom. In DOM samples (1750-4250 mu g of Cd g(-1), pH 5.4-6.3), Cd was coordinated by 0.3-1.8 S atoms at a distance of 2.51-2.56 angstrom and 3.6-4.5 O/N atoms at a distance of 2.23-2.26 angstrom. In both SOM and DOM samples a second coordination shell of 1.7-6.0 carbon atoms was found at an average distance of 3.12 angstrom. This is direct evidence for inner-sphere complexation of Cd by functional groups in NOM. Furthermore, ion activity measurements showed that less than 1% of total Cd was in the form of free Cd2+ in our samples. Bond distances and coordination numbers suggest that Cd complexed in SOM and DOM is a mixture of a 4-coordination with S (thiols) and 4- and 6-coordinations with O/N ligands. Given that Cd-S associations on average are stronger than Cd-O/N associations, our results strongly indicate that reduced S ligands are involved in the complexation of Cd by NOM also at native concentrations of metal in oxidized organic-rich soils and in humic streams.
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| 16. |
- Karlsson, Torbjörn, et al.
(author)
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Modeling Copper(II) Complexation in a Peat Soil Based on Spectroscopic Structural Information
- 2008
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In: Soil Science Society of America Journal. - : American Society of Agronomy. - 0361-5995 .- 1435-0661. ; 72:5, s. 1286-1291
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Journal article (peer-reviewed)abstract
- The speciation of Cu in soils and surface waters is largely influenced by complexation reactions with natural organic matter (NOM). In this study, ion selective electrode data for the binding of Cu2+ to a forest peat soil were collected as a function of equilibration time, pH (2.4–6.6), and total Cu(II) concentration (1–54g Cu kg–1 dry soil). As a first step, a one-site Langmuir isotherm was successfully fitted to the Cu adsorption data for the complete concentration range at pH 4.6. In a second step, structural information extracted from extended x-ray absorption fine structure (EXAFS) spectroscopy, showing that Cu(II) forms five-membered rings with possible combinations of amine, carboxyl, and carbonyl functional groups in NOM, were used as input for chemical speciation calculations (using the chemical equilibrium model MINTEQA2). In agreement with the EXAFS results, a model consisting of one RNH2, forming monodentate complexes (Cu2+ + RNH2 RH2NCu2+; log stability constant KRH2NCu2+ = 9.2; –log acid dissociation constant [pKa] = 9.0 for RNH3+), and two adjacent RCOO– groups, forming bidentate complexes (Cu2+ + 2RCOO– Cu(OOCR)2; log stability constant β(RCOO)2Cu = 4.7; pKa = 4.5 for RCOOH), gave the best fit to the experimental data. Determined stability constants for Cu(II)–amine and Cu(II)–carboxyl complexes were in good agreement with well-defined Cu complexes with amino acids and carboxyls, respectively.
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| 17. |
- Karlsson, Torbjörn, et al.
(author)
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Characterization of iron(III) in organic soils using extended X-ray absorption fine structure spectroscopy
- 2008
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In: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 42:15, s. 5449-5454
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Journal article (peer-reviewed)abstract
- The distribution of different iron (Fe) species in soils, sediments, and surface waters has a large influence on the mobility and availability of Fe, other nutrients, and potentially toxic trace elements. However, the knowledge about the specific forms of Fe that occurs in these systems is limited, especially regarding associations of Fe with natural organic matter (NOM). In this study, extended X-ray absorption fine structure (EXAFS) spectroscopy was used to characterize Fe(III) in organic soils (pH 4.6-6.0) with varying natural Fe content. The EXAFS data were subjected to wavelet transform analysis, to facilitate the identification of the nature of backscattering atoms, and to conventional EXAFS data fitting. The collective results showed the existence of two pools of iron: mononuclear Fe(III)-NOM complexes and precipitated Fe(III) (hydr)oxides. In the soil with lowest pH (4.6) and Fe content mononuclear organic complexes were the completely dominating fraction whereas in soils with higher pH and Fe content increasing amounts of Fe (hydr)oxides were detected. These results are of environmental importance, as the different iron pools most likely have markedly different reactivities.
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| 18. |
- Skyllberg, Ulf, et al.
(author)
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Elevated Concentrations of Methyl Mercury in Streams after Forest Clear-Cut : A Consequence of Mobilization from Soil or New Methylation?
- 2009
-
In: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 43:22, s. 8535-8541
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Journal article (peer-reviewed)abstract
- Concentrations of inorganic, mercuric mercury (Hg-II), methyl mercury (MeHg) and ancillary chemistry measured in first-order streams draining 0-4 (N = 20) and 4-10 (N = 27) year-old clear-cuts of former Norway Spruce Picea abies (Karst.) forest stands were compared with concentrations in streams draining 70 year-old Norway Spruce reference stands(N = 10). Concentrations of MeHg, and ratios of MeHg TOC-1 and Hg-II TOC-1, were significantly (p 0.01)elevated in 0-4 year-old clear-cuts, as compared to references. The only ancillary variable showing a significant elevation for 0-4 year-old clear-cuts was Mn (P 0.02). The 4-10 year-old clear-cuts showed intermediate concentrations with nonsignificant differences as compared to references, pH, nitrate, sulfate, Ca, Fe, TOC, TON, and the aromaticity of TOC (SUVA(254 nm)) showed nonsignificant differences between clear-cut age classes and references, Assuming that MeHg and Hg-II are mobilized from soil to stream to a similar relative extent as a consequence of clear-cutting, a calculation showed that 1/6 of the elevated MeHg concentration was due to enhanced mobilization from soil and 5/6 was due to new methylation of Hg-II 0-4 years after clear-cut New methylation after clear-cut is suggested to be stimulated by an increased availability of electron donors for methylating bacteria, as a consequence of degradation of logging residue ("slash") and soil organic matter. A subdivision of sites situated above and below the highest postglacial coastline (HC) revealed a significant elevation of MeHg, MeHg TOC-1 and Hg-II TOC-1 (p 0.05) beyond their references in 0-4 year-old clear-cuts above (but not below) the HC. This suggests that postglacial deposits of FeS(s) and FeS2(s) were not an important factor for elevation of MeHg after clear-cut.
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| 19. |
- Skyllberg, Ulf, et al.
(author)
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Förbättrad riskbedömning av kvicksilverförorenade sediment
- 2006
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Reports (other academic/artistic)abstract
- Kunskapen om risker för miljö och människa i och i anslutning till lokalt gravt kvicksilverförorenade sediment och jordar är idag begränsad. Senare års forskning om kvicksilvers biogeokemi i sediment, jordar och vattendrag påverkade av mer diffusa utsläpp pekar entydigt på att bildning, tillgänglighet och spridning av organiska former av kvicksilver, i huvudsak metylkvicksilver (MeHg), är mest kritiskt för ackumulering av kvicksilver i biota. Med detta synsätt som utgångspunkt, har syftet med föreliggande projekt varit att identifiera de faktorer som styr bildning, ackumulering och löslighet av metylkvicksilver i förorenade sediment. Bildning av MeHg ombesörjs i första hand av s.k. sulfatreducerande bakterier. Nettoproduktion av MeHg ges av skillnaden mellan bildning och nedbrytning av MeHg. Dessutom bidrar bort- och tillförsel av MeHg till totalhalten i sedimentet. Baserad på rådande teoribildning, har vår arbetshypotes varit att de kemiska formerna av oorganisk kvicksilver (Hg) i porvattnet, främst halten av neutrala Hgsulfider, styr nettometyleringen medan löst organisk substans och lösta oorganiska sulfider avgör lösligheten av både Hg och MeHg. Sju olika objekt med kvicksilverhaltiga sediment inkluderades i studien. Sediment från Karlshäll, Turingen, Övre Svartsjön och Nötöfjärden har alla påverkats av utsläpp av fenylkvicksilverpreparat tillsammans med massafiber, medan sediment från Köpmanholmen, Skutskär och Marnästjärn i huvudsak är påverkade av utsläpp av Hg0(l) från kloralkaliindustrier och annan industriell verksamhet. Lokalerna täcker in en variation i såväl klimat, salinitet som produktivitet och halt av organiskt material. All provtagning av sediment och porvatten utfördes under reducerad miljö (kvävgas). En delstudie visade att halten av metylkvicksilver i porvatten kan underskattas mer än 100 gånger om extraktion och filtrering av porvatten inte sker i anaerob miljö. Förutom våtkemiska metoder användes röntgenspektroskopi för analys av den fasta fasen. I porvattnet analyserades Hg, MeHg, dominerande anjoner och katjoner, pH, löst sulfid och löst organisk substans. Den kemiska speciationen i porvattnet beräknades med modeller. Dessutom bestämdes metylerings- och demetyleringshastigheten i samtliga sedimentprover under 48 timmar vid 25°C. Resultaten visar att koncentrationen av neutrala Hg-sulfider, tillsammans med tillgången på energirika kolföreningar, bestämmer både metyleringshastighet och den långsiktiga ackumuleringen av metylkvicksilver. Baserat på de sju objekten i studien, visade sötvattenmiljöer med hög primärproduktion och höga halter av neutrala Hg-sulfider både den högsta metyleringshastigheten och den högsta %-andelen MeHg i sedimenten. Resultaten visar att, förutom totalhalter av Hg och MeHg, bör halten av lösta sulfider och en kvantifiering av primärproduktion och energirika kolföreingar ingå som en del i underlaget vid riskbedömning av kvicksilverhaltiga sediment.
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| 20. |
- Skyllberg, Ulf, et al.
(author)
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Net Methylmercury Production as a Basis for Improved Risk Assessment of Mercury-contaminated Sediments
- 2007
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In: AMBIO: A Journal of the Human Environment. ; 36:6, s. 437-42
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Journal article (peer-reviewed)abstract
- Sediments contaminated by various sources of mercury (Hg) were studied at 8 sites in Sweden covering wide ranges of climate, salinity, and sediment types. At all sites, biota (plankton, sediment living organisms, and fish) showed enhanced concentrations of Hg relative to corresponding organisms at nearby reference sites. The key process determining the risk at these sites is the net transformation of inorganic Hg to the highly toxic and bioavailable methylmercury (MeHg). Accordingly, Hg concentrations in Perca fluviatilis were more strongly correlated to MeHg (p < 0.05) than to inorganic Hg concentrations in the sediments. At all sites, except one, concentrations of inorganic Hg (2–55 μg g−1) in sediments were significantly, positively correlated to the concentration of MeHg (4–90 ng g−1). The MeHg/Hg ratio (which is assumed to reflect the net production of MeHg normalized to the Hg concentration) varied widely among sites. The highest MeHg/Hg ratios were encountered in loose-fiber sediments situated in southern freshwaters, and the lowest ratios were found in brackish-water sediments and firm, minerogenic sediments at the northernmost freshwater site. This pattern may be explained by an increased MeHg production by methylating bacteria with increasing temperature, availability of energy-rich organic matter (which is correlated with primary production), and availability of neutral Hg sulfides in the sediment pore waters. These factors therefore need to be considered when the risk associated with Hg-contaminated sediments is assessed.
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| 21. |
- Swarbrick, Janine C, et al.
(author)
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High energy resolution X-ray absorption spectroscopy of environmentally relevant lead(II) compounds
- 2009
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In: Inorganic chemistry. - : American Chemical Society (ACS). - 1520-510X .- 0020-1669. ; 48:22, s. 10748-10756
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Journal article (peer-reviewed)abstract
- The determination of the chemical environment of Pb in natural samples is a challenge of great importance in environmental and health physics. We report a high energy resolution fluorescence detection (HERFD) X-ray absorption near-edge spectroscopy (XANES) study at the Pb L(3) and L(1) absorption edges to determine the chemical environment of Pb in a series of model and environmentally relevant compounds. HERFD spectroscopy can reveal increased spectral detail due to an apparent reduction in the core hole lifetime broadening. HERFD spectra of model Pb(II) compounds were compared to FEFF 8.4 multiple scattering calculations with reduced peak broadening parameters, and density of state (DOS) simulations, to determine the origins of the spectral features. A pre-edge in the L(3) XANES is revealed which is shown to arise from hybridization between the Pb p and d states. HERFD spectra of Pb(II)-containing environmentally relevant solutions were compared to model spectra and calculations. The results presented in this paper show that the chemical environment of Pb can be identified from spectral features resolved in HERFD spectroscopy at the Pb L(3) edge. The technique provides information that is complementary to conventional extended X-ray absorption fine structure (EXAFS) spectroscopy.
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