| 1. |
- Bäckström, Mattias, et al.
(author)
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Diurnal variations of abiotic parameters in a stream, recipient for drainage water in Ranstad, southwest Sweden
- 2002
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In: Journal of Environmental Monitoring. - Cambridge : Royal Society of Chemistry. - 1464-0325 .- 1464-0333. ; 4:5, s. 772-777
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Journal article (peer-reviewed)abstract
- During 24 h, water samples were taken for determination of a number of key parameters in a water system containing high concentrations of FeII at circumneutral pH. None of the major constituents (Ca, Mg, Na, K and sulfate) showed diurnal variations, while dissolved oxygen and pH increased during the night. This increase could entirely be explained by the decrease in water temperature. However, the concentration of FeII slightly increased at constant concentration of total Fe during the night, opposite to earlier observations in other systems where the presence of FeII was shown to be controlled by photoreduction. Nocturnal peaks of FeII have also been observed in other systems with high iron concentrations, however, at acidic pH, but without obvious explanation. The mechanisms for this process therefore need further investigation.
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| 2. |
- Bäckström, Mattias, 1974-, et al.
(author)
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Effects of a fulvic acid on the adsorption of mercury and cadmium on goethite
- 2003
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In: Science of the Total Environment. - Amsterdam, Netherlands : Elsevier. - 0048-9697 .- 1879-1026. ; 304:1-3, s. 257-268
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Journal article (peer-reviewed)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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| 3. |
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| 4. |
- Bäckström, Mattias, et al.
(author)
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Metal leachability and anthropogenic signal in roadside soils estimated from sequential extraction and stable lead isotopes
- 2004
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In: Environmental Monitoring & Assessment. - 0167-6369 .- 1573-2959. ; 90:1-3, s. 135-160
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Journal article (peer-reviewed)abstract
- Several roadside soil samples were collected at two field sites in Sweden. They were analysed for total elemental content (using both ICP-MS and XRF) and stable lead isotopes. Extraction with deicing salt solution and sequential extraction were performed in order to elucidate the potential mobility due to the use of deicing agents. The total concentrations of elements, especially lead, have decreased and lead is presently almost at background concentrations (15–51 ppm for surface samples). However, the isotopic signature indicates that old gasoline lead still is left at the site constructed prior to 1975. The field site constructed in 1992 showed, however, no 206Pb/207Pb ratio below 1.14. Only minor amounts were leached using deicing salt solutions; for lead only 0.29%, on average, was extracted indicating that the mobile fraction already was released. Sequential extraction indicated that lead mainly was associated with reducible (34.4%) and oxidisable (35.4%) fractions. Exchangable and acid soluble fractions contained 20.3% while 10.0% was found in the residual fraction. The salt extraction released, however, very low concentrations indicating that most in fraction 1 is acid soluble (e.g. carbonates). Tungsten was also found at high concentrations indicating a possible impact from studded tires. For tungsten the following composition was obtained: residual (48.0%) > oxidisable (47.6%) > reducible (3.3%) > exchangeable/acid soluble (1.1%). From the isotopic studies it was also suggested that the order for incorporating anthropogenic lead into soils is exchangeable/carbonates > (hydr)oxides > organic matter > residual. The multivariate technique principal component analysis (PCA) seems promising for evaluating large sequential extraction datasets.
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| 5. |
- Bäckström, Mattias, et al.
(author)
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Mobilisation of heavy metals by deicing salts in a roadside environment
- 2004
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In: Water Research. - : Elsevier BV. - 0043-1354 .- 1879-2448. ; 38:3, s. 720-732
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Journal article (peer-reviewed)abstract
- The seasonal variations of some selected heavy metals (Cd, Cu, Pb and Zn) and principal anions in soil solutions were monitored as a function of distance from the road at two field sites in Sweden. During the winter, the conductivity, concentrations of dissolved sodium and chloride increased dramatically due to the application of deicing agents (i.e. NaCl). Due to ion exchange, the pH decreased one unit in the soil solutions, whereas the concentrations of total organic carbon decreased due to coagulation and/or sorption to stationary solids. The heavy metal concentrations increased during the winter, but through different mechanisms. Cadmium concentrations in the aqueous phase increased as a response to ion exchange, possibly also enhanced by the formation of chloride complexes. Similarly, the concentrations of zinc increased, due to ion exchange, with calcium and protons. The mechanisms of mobilisation for copper and lead were not that clear probably due to association with coagulated or sorbed organic matter in combination with colloid dispersion.
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| 6. |
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| 7. |
- Bäckström, Mattias, et al.
(author)
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Speciation of heavy metals in road runoff and roadside total deposition
- 2003
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In: Water, Air and Soil Pollution. - 0049-6979 .- 1573-2932. ; 147:1-4, s. 343-366
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Journal article (peer-reviewed)abstract
- The concentrations of Cd, Co, Cu, Pb, W and Zn were measured in road runoff and total deposition at two Swedish field sites during one year. It was found that the concentrations of most elements increased significantly during the winter, up to one order of magnitude. For cobalt and tungsten, it was found that around 90% of the total mass transport occurred during the winter, whereas for Cu, Pb, Cd, Zn and Na, the corresponding figures were 70–90, 40–80, 60–90, 50–70 and >99% depending on site specific conditions. The deicing salts (rock salts) did not significantly contribute to the increase in trace element concentrations. Instead, the increased concentrations were due to more intense wearing of the pavement during the winter because of the use of studded tires in combination with the chemical effects caused by the use of deicing salts. New potential elemental markers for roads and traffic are suggested.
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| 8. |
- Dahlén, Johan, et al.
(author)
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Analysis of low molecular weight organic acids in water with capillary zone electrophoresis employing indirect photometric detection
- 2000
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In: Fresenius' Journal of Analytical Chemistry. - : Springer Science and Business Media LLC. - 0937-0633 .- 1432-1130. ; 366:5, s. 488-493
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Journal article (peer-reviewed)abstract
- A capillary zone electrophoretic method for the analysis of low molecular weight carboxylic acids in water was developed. The application uses the chromophore trimellitic acid that allows for indirect photometric detection at 254 nm. Selectivity control by the addition of Ca2+ to the carrier electrolyte made possible a baseline resolved separation of 14 carboxylic acids. Good linearity and repeatability were obtained for both electrokinetic and hydrostatic injection modes. The usefulness of the method is demonstrated by the analysis of a snow sample.
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| 9. |
- Dahlén, Johan, et al.
(author)
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Determination of nitrate and other water quality parameters in groundwater from UV/Vis spectra employing partial least squares regression
- 2000
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In: Chemosphere. - : Pergamon Press. - 0045-6535 .- 1879-1298. ; 40:1, s. 71-77
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Journal article (peer-reviewed)abstract
- The use of UV/Vis spectroscopy in combination with partial least squares (PLS) regression for the simultaneous prediction of nitrate and non-purgeable organic carbon (NPOC) in groundwaters was evaluated. A model of high quality was obtained using first order derivative spectra in the range 200–300 nm. Inclusion of non-UV-absorbing constituents in the modeling procedure, i.e., chloride, sulfate, fluoride, total carbon (TC), inorganic carbon (IC), alkalinity, pH and conductivity was also evaluated. This model seemed to be useful for prediction of chloride, TC, IC, alkalinity and conductivity, while its ability to predict sulfate, fluoride and pH was poor. In conclusion, application of PLS regression, which requires neither filtration of samples nor addition of chemicals, is a promising alternative for fast interpretation of geochemical patterns of groundwater quality.
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| 10. |
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