| 1. |
- Dahlqvist, Ralf, et al.
(författare)
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Temporal variations of colloidal carrier phases and associated trace elements in a boreal river
- 2007
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Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 71:22, s. 5339-5354
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Tidskriftsartikel (refereegranskat)abstract
- Elemental size distributions, from truly dissolved through colloidal to particulate, have been studied in a subarctic boreal river. The measurements, carried out during 2002, ranged from winter to summer conditions, including an intense spring flood event. Results are reported for a total of 42 elements. Size distributions were characterised using a combination of cross-flow (ultra)filtration (CFF), flow field-flow fractionation (FIFFF), and diffusive gradients in thin-films (DGT). The three techniques showed similar trends, but quantitative comparisons reveal some important differences that warrant further investigation. Previous work has identified two colloidal carrier phases in fresh waters, dominated by iron and carbon, respectively. The majority of the elements studied are associated with one or both of these colloidal carrier phases. The exceptions are the alkali metals and several anions that are only very weakly associated with colloidal material, and which therefore occur mainly as truly dissolved material (< 1 kDa in molecular weight). We discuss the likely origin for the two colloidal carrier phases and consider how associated trace elements fit into the geochemical framework. The relative affinities of the elements for iron and carbon colloidal carrier phases are related to their chemistries, and are compared with earlier data from the Delsjo Creek in southern Sweden. Elemental colloidal concentrations show strong seasonal variations related to changes in the colloidal carrier phase(s) with which they associate. In particular, many elements show a strong spring maximum in colloidal concentrations associated with the strong maximum in colloidal carbon concentration during the spring flood.
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| 2. |
- Alasonati, E, et al.
(författare)
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Asymmetrical flow field flow fractionation - Multidetection system as a tool for studying metal-alginate interactions
- 2006
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Ingår i: Environmental Chemistry. ; 3:3, s. 192-198
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Tidskriftsartikel (refereegranskat)abstract
- The present study explores the potential use of asymmetrical flow field flow fractionation (aFlFFF) with a multidetection system for the study of metal-alginate interactions. aFlFFF, coupled on-line to a differential refractive index and seven angle laser light scattering detectors was used to provide information on the alginate size distributions. In parallel, the metal distributions of metal-alginate complexes were probed by aFlFFF-high resolution inductively coupled plasma-mass spectrometry. Average values and continuous distributions of molar masses, radiuses of gyration and hydrodynamic radiuses, which are critical for understanding the role of alginates as carriers of metal pollutants, were evaluated in presence of Pb or Cd and compared with those in metal-free solutions of alginate. The values of number average and weight average molar mass, weight average radius of gyration and shape factor for alginate were 150 and 188 kg mol(-1), 53 nm and 1.7, respectively. Alginate molar mass and radius of gyration distributions were slightly shifted to higher values by the addition of micromolar concentrations of Pb or Cd. The alginate size distribution in the presence of Cd was similar to the alginate-alone control, whereas in the presence of Pb the size distribution was broader with a shift of the maximum toward higher molar masses.
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| 3. |
- Andersson, K, et al.
(författare)
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Colloidal rare earth elements in a boreal river: Changing sources and distributions during the spring flood
- 2006
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Ingår i: Geochimica Et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 70:13, s. 3261-3274
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Tidskriftsartikel (refereegranskat)abstract
- Variations in the physico-chemical speciation of the rare earth elements (REE) have been investigated in a subarctic boreal river during an intense spring flood event using prefiltered (< 100 mu m) samples, cross-flow (ultra)filtration (CFF), flow field-flow fractionation (FIFFF), and diffusive gradients in thin films (DGT). This combination of techniques has provided new information regarding the release and transport of the REE in river water. The colloidal material can be described in terms of two fractions dominated by carbon and iron, respectively. These two fractions, termed colloidal carrier phases, showed significant temporal changes in concentration and size distribution. Before the spring flood, colloidal carbon concentrations were low, the colloids being dominated by relatively large iron colloids. Colloidal concentrations increased sharply during the spring flood, with smaller carbon colloids dominating. Following the spring flood, colloidal concentrations decreased again, smaller carbon colloids still dominating. The REE are transported mainly in the particulate and colloidal phases. Before the spring flood, the REE composition of all measured fractions was similar to local till. During the spring flood, the REE concentrations in the colloidal and particulate fractions increased. The increase was most marked for the lighter REE, which therefore showed a strong enrichment when normalized to local till. Following the spring flood, the REE concentrations decreased again and reverted to a distribution similar to local till. These changes in the concentration and distributions of carbon iron and REE are interpreted in terms of changing hydrological flow paths in soil and bedrock which occur during the spring flood. (c) 2006 Elsevier Inc. All rights reserved.
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| 4. |
- Dahlqvist, Ralf, 1973, et al.
(författare)
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Association of calcium with colloidal particles and speciation of calcium in the Kalix and Amazon rivers
- 2004
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Ingår i: Geochimica Et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 68:20, s. 4059-4075
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Tidskriftsartikel (refereegranskat)abstract
- A considerable amount of colloidally bound Ca has been detected in water samples from Amazonian rivers and the Kalix River, a sub-arctic boreal river. Fractionation experiments using several analytical techniques and processing tools were conducted in order to elucidate the matter. Results show that on average 84% of the total Ca concentration is present as free Ca. Particulate, colloidal and complexed Ca constitute the remaining 16%, of which the colloidal fraction is significant. Ultrafiltration experiments show that the colloidal fraction in the sampled Amazonian rivers and the Kalix River range between 1% and 25%. In both the Amazonian and the Kalix rivers the technique of cross-flow ultrafiltration was used to isolate particles and colloids. The difference in concentration measured with ICP-AES and a Ca ion-selective electrode in identical samples was used to define the free Ca concentration and thus indirectly the magnitude of the particulate, colloidal and complexed fractions. Results from the Kalix and Amazonian rivers are in excellent agreement. Furthermore, the results show that the colloidal concentrations of Ca can be greatly overestimated (up to 227%) when conventional analysis and calculation of ultrafiltration data is used due to retention of free Ca ions during the ultrafiltration process. Calculation methods for colloidal matter are presented in this work, using complementary data from ISE analysis. In the Kalix River temporal changes in the fractionation of Ca were studied before, during and after a spring-flood event. Changes in the size distribution of colloidally associated Ca was studied using FlFFF (Flow Field-Flow Fractionation) coupled on-line to a HR ICP-MS. The FlFFF-HR ICP-MS fractograms clearly show the colloidal component of Ca, supporting the ultrafiltration findings. During winter conditions the size distribution of colloidally associated Ca has a concentration maximum at similar to5 to 10 nm in diameter, shifting to smaller sizes (<5 mm) during and after the spring flood. This shift in size distribution follows a change in the river during this period from ironoxyhydroxy colloids being the most important colloidal carrier phase to humic substances during and after the spring flood. WHAM and NICA-Donnan models were used to calculate the amount of colloidally bound Ca. The results similar for both models, show that on average 16% of the Ca may be associated to a colloidal phase, which is in broad agreement with the measurements. Copyright (C) 2004 Elsevier Ltd.
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| 5. |
- Gelting, J., et al.
(författare)
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Fractionation of iron species and iron isotopes in the Baltic Sea euphotic zone
- 2009
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Ingår i: Biogeosciences Discuss.. ; 6, s. 6635-6694
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of the physiochemical speciation of Fe in the euphotic zone were performed at three different locations, over a well defined salinity gradient, during spring and summer in the Baltic Sea. The average of total Fe changed from 114 nM in the Bothnian Sea, 44 nM at Landsort Deep and 15 nM at Gotland Deep. Particulate Fe (PFe) was the dominating phase at all stations and on average accounted for 75–85% of the total Fe pool. At all three locations, a decrease in total Fe of 80–90% from initial measurements compared to the summer was found. A strong positive correlation between PFe and chl-a was observed. Hence, primary production strongly regulates cycling of suspended Fe. However, this relation is not dominated by active uptake of Fe in phytoplankton; instead this reflects cycling of phosphorus, growth of diatoms, and removal of PFe during phytoplankton sedimentation. The average colloidal iron fraction, CFe, showed decreasing concentrations along the salinity gradient; Bothnian Sea 15 nM; Landsort Deep 1 nM and Gotland Deep 0.5 nM. Field Flow Fractionation data indicate that the main colloidal carrier phase for Fe in the Baltic Sea is a carbon-rich fulvic acid associated compound, likely of riverine origin. The Fe isotope composition (δ56Fe) of the PFe showed constant positive values in the Bothnian Sea surface waters (+0.08 to +0.20‰). Enrichment of heavy Fe in the Bothnian Sea PFe is most likely associated to input of aggregated land derived Fe-oxyhydroxides and a rapid overturn of Fe(II). At the Landsort deep, the fractionation of PFe changed between −0.08‰ to +0.28‰. The negative values, in early spring, probably indicate exchange over the oxic-anoxic boundary at ~80 m depth.
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| 6. |
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| 7. |
- Kalmykova, Yuliya, 1981, et al.
(författare)
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Colloid-Facilitated Metal Transport in Peat Filters
- 2010
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Ingår i: Water Environment Research. - 1061-4303 .- 1554-7531. ; 82:6, s. 506-511
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Tidskriftsartikel (refereegranskat)abstract
- The effect of colloids on metal retention in peat columns was studied, with the focus on colloids from two sources-organic matter leached from peat, and introduced organic and hydrous ferric oxide (HFO) colloids. A significant fraction of metals was found to be associated with peat-produced organic colloids; however the concentrations of organic colloids leached are low (trace concentrations) and temporal and have a limited effect on the efficiency of peat filters. In contrast, the presence of organic and HFO colloids in the input water causes a significant decrease in the performance of peat filters. Organic colloids were identified as the main vector of cadmium, copper, nickel, and zinc, while lead is transported by both organic and HFO colloids. The colloidal distribution of metals obtained in this study has important implications for the mobility of trace metals in porous media. The occurrence of colloids in the input waters and their characteristics must be considered when designing water treatment facilities.
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| 8. |
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| 9. |
- Stolpe, Björn, 1974, et al.
(författare)
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Changes in size distribution of fresh water nanoscale colloidal matter and associated elements on mixing with seawater
- 2007
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Ingår i: Geochimica Et Cosmochimica Acta. - : Elsevier BV. - 0016-7037. ; 71:13, s. 3292-3301
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Tidskriftsartikel (refereegranskat)abstract
- Changes in size distribution and elemental composition of 0.5-50 nm fresh water colloids during estuarine mixing have been studied by in-laboratory mixing of natural creek water and synthetic seawater, followed by size fractionation with Asymmetrical Flow Field-Flow Fractionation, and online elemental quantification by High-Resolution ICPMS. At least two types of colloids were present in the studied size region; 0.5-3 nm fluorescent dissolved organic matter (FDOM), and >3 nm colloids that were rich in Fe and colored dissolved organic matter (CDOM). Most trace elements were associated in different proportions to these two populations of colloids. Following mixing with synthetic seawater, the >3 nm. Fe-rich colloids and CDOM were extensively removed from the studied size region by salt induced aggregation. The degree of removal with increasing salinity was greatest below 2.5 parts per thousand. salinity, continued to a lesser degree between 2.5%. and 15 parts per thousand. salinity, above which only very small additional removal could be distinguished. At 25 parts per thousand. salinity, the Fe concentration in the 0.5-50 size region had been reduced down to 15% of its original value in freshwater, while the amount of CDOM had been reduced to 55%. On the contrary, the concentration of the 0.5-3 run FDOM was unchanged by the increased concentration of sea salt. Therefore, colloidally associated Al, P, Co, Cu, Zn, Ce, Lu and Ph were removed from the 0.5-50 nm size region according to their relative distributions between the FDOM and the Fe-rich colloids. Consequently, at 25 parts per thousand. salinity, the 0.5-50 nm concentrations of Al, Mn, P and Pb, (mainly associated with the Fe-rich colloids) had been reduced down to 13-26% of their values in freshwater, while the concentrations of Co and Cu (with higher preferences for FDOM) were less reduced, down to 46% and 57%, respectively. Changes in the elemental composition of the remaining colloidal matter were observed, the most pronounced were increased contents of P, A] and Pb in Fe-rich colloidal matter of medium size (similar to 3-15 nm) and increased Pb content in Fe-rich colloidal matter of larger size (similar to 5-50 nm). (c) 2007 Elsevier Ltd. All rights reserved.
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| 10. |
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