Impact of acid sulfate soils on the geochemistry of rivers in south-western Finland

Nyberg, Maria E.; Österholm, Peter; Nystrand, Miriam

doi:10.1007/s12665-011-1216-4

Cited by 18 publications

(5 citation statements)

References 24 publications

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“…Coastal acid sulfate soils (CASS) form when sediments containing highly reduced monosulfide and disulfide minerals, such as mackinawite (FeS) and pyrite (FeS 2 ), are exposed to oxygen in the atmosphere, mainly during anthropogenic disturbances including soil excavation, water table drainage, and land disposal of sulfide-rich estuarine sediments . Acute acidification induced by oxidation of sulfide minerals at the source of the disturbance can mobilize drainage rich in iron, sulfate, and trace elements (including REEs) to receiving systems via surface water and groundwater discharge. − While REE abundance and fractionation has been widely investigated in soil and sedimentary systems affected by acid sulfate soil and/or drainage, these studies are typically based on analysis of chemical extractions of bulk solid phase samples, ,− which does not adequately capture specific REE–mineral associations at the micro- and nanoscale.…”

Section: Introductionmentioning

confidence: 99%

Micro- and Nanoscale Identification of Rare Earth Element–Mineral Associations in an Acidified Dredge Spoil and Adjacent Reduced Sediments

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Morgan

et al. 2018

ACS Earth Space Chem.

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Although rare earth element (REE) concentrations and speciation are often investigated by chemical extractions of bulk soils and sediments to elucidate site specific environmental processes and anthropogenic influences, micro- and nanoscale investigations provide more precise insights into the REE–mineral associations essential for understanding REE mobility in complex natural landscapes. In this study, we combine the high-resolution microscopic techniques of scanning electron microscopy energy dispersive spectroscopy (SEM-EDS), transmission electron microscopy (TEM), and electron energy-loss spectroscopy (EELS) to characterize micro- and nanoscale REE–mineral associations in an eutrophic estuarine system, specifically at a site containing (1) a coastal acid sulfate soil (CASS) and (2) adjacent estuarine sediments that have received acute acidic drainage from the CASS site for ∼20 years. This study revealed particles with a porous morphology that had a recurring association between Fe and the REE lanthanum (La/Fe/O = 1:1:3) in the sediments, indicating a presence of either a pure orthoferrite ABO3 compound (A = REE, B = metal), or a co-occurrence of REE and Fe minerals (i.e., La2O3 coprecipitated in 1:1 stoichiometry with Fe oxide). Fe(III) minerals are typical of CASS influenced sites and are likely to be essential REE sinks in this system. Additionally, micro- to nanoscale REE–phosphate particles were also widespread here, which may reflect an important REE sink in eutrophic sediments. Specifically, a REE–phosphate particle targeted by SEM was thin sectioned by focused ion beam (FIB) for TEM analysis, revealing a crystal structure (a = 6.6 Å, b = 6.9 Å, α = 90°) consistent with monazite ((REEs, Th)PO4). Usually, a positive Ce anomaly is found more in oxidized solid phase due to less soluble oxidized Ce(IV)O2. Interestingly, our EELS data revealed that Ce was only present as reduced Ce(III) in our solid sample, showing the possibility of Ce3+ incorporating into less soluble minerals such as REE–phosphate, which may explain the higher positive Ce anomaly observed in insoluble phases in reduced sediment. Microtubular cavities, consistent with abiotic processes in REE–phosphate precipitation, were also observed on the cross-sectioned monazite.

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Section: Introductionmentioning

confidence: 99%

Micro- and Nanoscale Identification of Rare Earth Element–Mineral Associations in an Acidified Dredge Spoil and Adjacent Reduced Sediments

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Morgan

et al. 2018

ACS Earth Space Chem.

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“…T his study examines the changes to soil porewater chemistry that occurred when previously desiccated active acid sulfate soils (ASS) with a sulfuric horizon (pH <3.5) (Soil Survey Staff, 2014) were rapidly submerged by a large freshwater body. Acidity, metals, and metalloids (Al, As, Fe, Mn, Ni, Zn) made available from the oxidation of pyrite contained in potential ASS with sulfidic material (pH >3.5) or subsequent processes, such as the acid dissolution of layer silicate clays, can be mobilized during rewetting and potentially result in damage to surrounding ecosystems (Astrom and Astrom, 1997; Dent, 1986; Macdonald et al, 2004; Nyberg et al, 2012; Nystrand and Osterholm, 2013). The most significant risks of environmental degradation usually occur following the rewetting of desiccated and acidified (pH <3.5) active ASS but before the reestablishment of reducing conditions where dilution and neutralization toward circumneutral pH can immobilize some metal species and encourage the reformation of sulfide minerals.…”

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confidence: 99%

Porewater Geochemistry of Inland Acid Sulfate Soils with Sulfuric Horizons Following Postdrought Reflooding with Freshwater

et al. 2015

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Following the break of a severe drought in the Murray-Darling Basin, rising water levels restored subaqueous conditions to dried inland acid sulfate soils with sulfuric horizons (pH <3.5). Equilibrium dialysis membrane samplers were used to investigate in situ changes to soil acidity and abundance of metals and metalloids following the first 24 mo of restored subaqueous conditions. The rewetted sulfuric horizons remained severely acidified (pH ∼4) or had retained acidity with jarosite visibly present after 5 mo of continuous subaqueous conditions. A further 19 mo of subaqueous conditions resulted in only small additional increases in pH (∼0.5-1 pH units), with the largest increases occurring within the uppermost 10 cm of the soil profile. Substantial decreases in concentrations of some metal(loid)s were observed with time most likely owing to lower solubility and sorption as a consequence of the increase in pH. In deeper parts of the profiles, porewater remained strongly buffered at low pH values (pH <4.5) and experienced little progression toward anoxic circumneutral pH conditions over the 24 mo of subaqueous conditions. It is proposed that low pH conditions inhibited the activity of SO-reducing bacteria and, in turn, the in situ generation of alkalinity through pyrite production. The limited supply of alkalinity in freshwater systems and the initial highly buffered low pH conditions were also thought to be slowing recovery. The timescales involved for a sulfuric horizon rewetted by a freshwater body to recover from acidic conditions could therefore be in the order of several years.

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“…Some agricultural land areas in the Eurajoki basin are classified as acid sulphate soils, which are highly productive. Periodically, high acidity and high concentrations of sulphate and metals are associated with stream waters affected by acid sulphate soils (Nyberg et al 2012). Vuorenmaa et al (2002) studied small agricultural catchments and found that losses of TP were lower from agricultural acid sulphate soils compared with clayey agricultural soils.…”

Section: Study Areasmentioning

confidence: 99%

High-frequency measured turbidity as a surrogate for phosphorus in boreal zone rivers: appropriate options and critical situations

Kämäri

Tarvainen

Kotamäki

et al. 2020

Environ Monit Assess

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In situ high-frequency measured turbidity can potentially be used as a surrogate for riverine phosphorus (P) concentrations to better justify the effectiveness of nutrient loss mitigation measures at agricultural sites. We explore the possibilities of using turbidity as a surrogate for total phosphorus (TP) and particulate phosphorus (PP) in four snowmelt-driven rivers draining agricultural clayey catchments. Our results suggest slightly stronger relationship between in situ measured turbidity and PP than between turbidity and TP. Overall, linear TP and PP regressions showed better error statistics in the larger catchments compared with their sub-catchments. Local calibration of the in situ sensors was sensitive to the number of high P concentration discrete water samples. Two optional calibration curves, one with and one without influential data, resulted in a 17% difference in the estimated mean TP concentrations of a snowmelt storm contributing 18% of the annual discharge volume. Accordingly, the error related to monthly mean TP estimates was the largest in spring months at all sites. The addition of total dissolved phosphorus (TDP) improved the model performance, especially for sites where the TDP/TP ratio is large and highly variable over time. We demonstrate how long-term discrete samples beyond sensor deployment can be utilized in the evaluation of the applicability range of the local calibration. We recommend analysing the validity of P concentration estimates, especially during high discharge episodes that contribute substantially to annual riverine nutrient fluxes, since the use of surrogates may introduce large differences into the P concentration estimates based on selected local calibration curves.

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Impact of acid sulfate soils on the geochemistry of rivers in south-western Finland

Cited by 18 publications

References 24 publications

Micro- and Nanoscale Identification of Rare Earth Element–Mineral Associations in an Acidified Dredge Spoil and Adjacent Reduced Sediments

Micro- and Nanoscale Identification of Rare Earth Element–Mineral Associations in an Acidified Dredge Spoil and Adjacent Reduced Sediments

Porewater Geochemistry of Inland Acid Sulfate Soils with Sulfuric Horizons Following Postdrought Reflooding with Freshwater

High-frequency measured turbidity as a surrogate for phosphorus in boreal zone rivers: appropriate options and critical situations

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