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| 3. |
- Nordmyr, Linda, et al.
(författare)
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The influence of metal leakage from acid sulphate soils on estuarine sediments in western Finland.
- 2006
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Konferensbidrag (refereegranskat)abstract
- Acid sulphate soils (AS soils) release large amounts of acidity and chemical elements into the rivers in western Finland. A recent study by our research group showed that AS soils liberate more toxic metals into water courses than the whole Finnish industry together. The elevated concentrations of metals are transported to the estuary, where they are deposited as a result of higher salinity and pH, and slower water currents. The bottom sediments are therefore excellent tools to evaluate changes in element discharge into the environment over both temporal and spatial scales. The objective of this study was to track changes in sediment elemental distribution as a result of leakage from AS soil landscapes and to quantify the impact of AS soils from the drainage area to the sea. The Vörå River is one of the most strongly AS soil affected rivers in Finland. It has a low pH (occasionally down to 4.0) and carries high amounts of many metals, which as a result of increasing pH and salinity, are precipitated and deposited in the bottom sediments in the estuary. The coastal area adjacent to this river was therefore selected for a bottom sediment and suspended particulate matter study. This study comprises sampling of four sediment cores and collection of particular matter with sediment traps, in a profile extending from the river mouth out to the open sea. A selective chemical extraction procedure was used in order to identify the chemical speciation within the sediment.The results show that an appreciable amount of elements (e.g. Al, Cd, Co, Cu, La, Mn, Ni and Zn) are elevated in the surface and sub-surface of the sampled bottom sediments compared to the deeper sediment background levels. These elements are all known to be leached from AS soils. At a site, approximately 4 km from the river outlet the sediments had 5-100 times higher concentrations of Cd, Co, Mn, Ni and Zn compared to the background levels. These elevated concentrations are much higher than the corresponding concentrations in the sediment cores situated closer to the river mouth. The reason for this deposition pattern is that some elements like for example Al and Cu are pH sensitive, and are therefore deposited closer to the river mouth, while other elements like Cd, Co, Mn, Ni and Zn are transported further out in the estuary and are not deposited until the impact of sea water increases. In contrast, elements that are not abundantly leached from Finnish AS soils (e.g. Cr, Pb, Ti and V) display a consistent concentration pattern in all sediment cores. This leads to the conclusion that the elevated element concentrations in the surface layers are a result of leakage from AS soils.The elevated concentrations of Cd, Co, Mn, Ni and Zn pose a significant environmental problem since: 1) episodic pH declines in the shallow estuary, caused by strong runoff from the river, might cause sudden release and relocation of the metals; and 2) as a result of the isostatic land uplift of the region (0.9 cm/year), these bottom sediments are going to be new land in a near future and will then consist of metal-contaminated land. The elevated concentrations of these metals at such a distance from AS soil environments suggest that the environmental impact of metal leakage extends far beyond the geographically adjacent environment. This poses a significant issue for land management.
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- Åström, Mats E., et al.
(författare)
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Attenuation of rare earth elements in a boreal estuary
- 2012
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Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 96, s. 105-119
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Tidskriftsartikel (refereegranskat)abstract
- This study focuses on attenuation of rare earth elements (REE) when a boreal creek, acidified and loaded with REE and other metals as a result of wetland drainage, empties into a brackish-water estuary (salinity < 6 parts per thousand). Surface water was collected in a transect from the creek mouth to the outer estuary, and settling (particulate) material in sediment traps moored at selected locations in the estuary. Ultrafiltration, high-resolution ICP-MS and modeling were applied on the waters, and a variety of chemical reagents were used to extract metals from the settling material. Aluminium, Fe and REE transported by the acidic creek were extensively removed in the inner/central estuary where the acidic water was neutralised, whereas Mn was relatively persistent in solution and thus redistributed to particles and deposited further down the estuary. The REE removal was caused by several contemporary mechanisms: co-precipitation with oxyhydroxides (mainly Al but also Fe), complexation with flocculating humic substances and sorption to suspended particles. Down estuary the dissolved REE pool, remaining after removal, was fractionated: the < 1 kDa pool became depleted in the middle REE and the colloidal (0.45 mu m-1 kDa) pool depleted in the middle and heavy REE. This fractionation was controlled by the removal process, such that those REE with highest affinity for the settling particles became most depleted in the remaining dissolved pool. Modeling, based on Visual MINTEQ version 3.0 and the Stockholm Humic Model after revision and updating, predicted that the dissolved (< 0.45 mu m) REE pool in the estuary is bound almost entirely to humic substances. Acid sulphate soils, the source of the REE and other metals in the creek water, are widespread on coastal plains worldwide and therefore the REE attenuation patterns and mechanisms identified in the studied estuary are relevant for recognition of similar geochemical processes and conditions in a variety of coastal locations.
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- Åström, Mats E., et al.
(författare)
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Lanthanoid behaviour in an acidic landscape
- 2010
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Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 74:3, s. 829-845
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Tidskriftsartikel (refereegranskat)abstract
- Lanthanoids were studied in a boreal landscape where an abundance of acid sulfate soils and Histosols provide a unique opportunity to increase the understanding of flow these metals behave in acidic soils and waters and interact with soil and aqueous organic matter. In the acid sulfate soils lanthanoids are mobile as reflected in high to very high concentrations in soil water and runoff (typically a few mg 1(-1) but Lip to 12 mg 1(-1)) and abundant release by several relatively weak extractants (ammonium acetate EDTA, sodium pyrophosphate, hydroxylamine hydrochloride) applied on bulk soil. Normalisation with the lanthanoid pool in the underlying parent materials (sulphide-bearing sediments deposited in brackish-water) and soil water showed that the extensive release/retention in the acidic soil was accompanied by large, and variable, fractionation trends across the lanthanoid series. In low-order streams draining these soils, the lanthanoid concentrations were high and, as indicated by frontal ultrafiltration and geochemical modelling, largely dissolved (<1 kDa) in the form of the species LnSO(4)(+) and Ln(3+). In other moderately acidic stream waters (pH 4.3-4.6), organic complexation was predicted to be important in the <1 kDa fraction (especially for the heavy lanthanoids) and strongly dominating in the colloidal phase (1 kDa-0.45 mu m). Along the main stem of a stream in focus (catchment area of 223 km(2)), lanthanoid concentrations increased downstream, in particular during high flows, caused by a downstream increase in the proportion of acid sulfate soils which are extensively flushed during wet periods. The geochemical models applied to the colloidal Ln-organic phase were not successful in predicting the measured fractionation patterns.
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- Åström, Mats E., 1963-, et al.
(författare)
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Sources, transport and sinks of beryllium in a coastal landscape affected by acidic soils
- 2018
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Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier. - 0016-7037 .- 1872-9533. ; 232, s. 288-302
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Tidskriftsartikel (refereegranskat)abstract
- Beryllium (Be) sources, transport and sinks were studied in a coastal landscape where acidic soils (acid sulfate soils) have developed after drainage of fine-grained sulfide-bearing sediments. The study included the determination of total abundance and speciation of Be in a variety of solid and aqueous materials in both the terrestrial and estuarine parts of the landscape. A major feature was that despite normal (background) Be concentration in the sulfide-bearing sediments, the Be leaching from these sediments after O2-exposure and acid sulfate soil development were extensive, with concentrations up to 76 μg L−1 in soil water, 39 μg L−1 in runoff and 12 μg L−1 in low-order streams. These high Be concentrations were mainly in the solution form (i.e., passing a 1 kilodalton filter) and modelled to be dominated by free Be2+. The extensive Be release within, and leaching from the acid sulfate soils was controlled by pH, with a critical value of 4.0 below which the Be concentrations increased strongly. Although plagioclase and mica were most likely the main carriers of Be within these soils, it is suggested that other minerals such as Be hydroxides, Al hydroxides carrying Be, and Be sulfides are the main contributors of the abundance of dissolved Be in the acidic waters. When the acidic and Be-rich creek water was neutralized in the estuary of relatively low salinity, the dominating solution form of Be was removed by transformation to particles, reflected in the suspended particulate matter that had hydroxylamine hydrochloride extractable Be up to 17 mg kg−1 and ammonium acetate EDTA extractable Be up to 4 mg kg−1. In corresponding pristine materials (parent material of the acid sulfate soils) in the catchment, the median Be extractability with these reagents were only 0.3 and 0.05 mg kg−1, respectively. As the Be-rich suspended particulate matter ultimately became benthic sediment, the Be was preserved in terms of total concentrations but underwent to some extent changes in speciation, including release from hydroxides and concomitant scavenging by organic matter and particle surfaces.
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