Enrichment of trace metals from acid sulfate soils in sediments of the Kvarken Archipelago, eastern Gulf of Bothnia, Baltic Sea

Virtasalo, Joonas J.; Österholm, Peter; Kotilainen, Aarno; Åström, Mats E.

doi:10.5194/bg-17-6097-2020

Cited by 13 publications

(10 citation statements)

References 77 publications

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“…Co transfer to particulate form was twice of that of Mn, which highlights Co complexation with flocs in addition to Mn oxyhydroxides. This interpretation is supported by the seaward enrichment patterns of Co and Mn in the front of Laihianjoki and Sulvanjoki, where both Co and Mn are strongly enriched up to 12 km distance, while a lower Co enrichment continues to at least 26 km distance (Virtasalo et al, 2020).…”

Section: Implications For Seaward Metal Transportmentioning

confidence: 78%

“…A previous geochemical study of seafloor sediments in the front of Laihianjoki and Sulvanjoki found that AS soil-derived metals such as Cu and Co are strongly positively correlated with organic matter, particularly in the 2-6 µm sediment grain size range (Virtasalo et al, 2020). Also Al showed a weak correlation with this grain size range.…”

Section: Implications For Seaward Metal Transportmentioning

confidence: 86%

“…Previous studies in the nearby Vöyrinjoki estuary have documented that Cu to a large part is deposited in association with POC close to the river mouth (Nordmyr et al, 2008a, b;Nystrand et al, 2016). However, minor Cu enrichment in sediments at least 26 km seaward from the Laihianjoki and Sulvanjoki river mouths require that some Cu is transported and deposited farther out at the sea (Virtasalo et al, 2020). Previous studies have concluded Cu binding to organic ligands to be a significant mechanism for Cu distribution in the Gulf of Bothnia and elsewhere (e.g., van den Berg et al, 1987;Bordin et al, 1988;Muller and Batchelli, 2013).…”

Section: Implications For Seaward Metal Transportmentioning

confidence: 95%

“…Specifically, it was concluded that Al, Fe and Cu are deposited with organic matter close to the Vöyrinjoki river mouth, whereas Cd, Co, Ni, and Zn are preferentially transported farther out at the sea, where they co-precipitate and are deposited with Mn oxyhydroxides (Nordmyr et al, 2008a, b;Nystrand et al, 2016). However, a recent study of seafloor sediments shows that Cu as well as Cd, Co, Ni, and Zn all are enriched at least 26 km away from the mouths of the nearby Laihianjoki and Sulvanjoki rivers, whereas the Mn enrichment extends less than 14 km from the river mouths (Virtasalo et al, 2020). This discrepancy between the observed seafloor metal distribution and the previously concluded seaward transport behaviour of the metals calls for further investigation of the flocculation process in boreal humicrich rivers that are strongly impacted by acidity and metal release from AS soils.…”

Section: Introductionmentioning

confidence: 99%

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Estuarine flocculation dynamics of organic carbon and metals from boreal acid sulphate soils

Virtasalo

Österholm

Asmala³

2023

Preprint

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Abstract. Flocculation of riverine dissolved organic matter to the particulate form in estuaries is an important mechanism for capturing dissolved metals to newly formed organic particles, regulating the metal transport to the sea. The process is particularly relevant for rivers draining boreal acid sulphate soils of western Finland, which are known to deliver large amounts of trace metals with detrimental environmental consequences to the recipient estuaries in the eastern Gulf of Bothnia, northern Baltic Sea. This is the first study to investigate dissolved metal (Al, Fe, Mn, Co and Cu) association with flocculating organic particles in the laboratory, by mixing of acidic metal-rich water from acid sulphate soil-impacted rivers and particle-free artificial seawater. Water samples were collected in April 2021 from the Laihianjoki and Sulvanjoki rivers in western Finland. Experiments with an in situ laser diffraction-based particle size distribution sensor and a multiparameter water quality sonde were run to continuously monitor the development of suspended particle pool over the salinity gradient from 0 to 6, corresponding the salinity range observed in these estuarine systems. Flocculator experiments with discrete salinity treatments were carried out to investigate metal behaviour with the collection of flocculated material on glassfibre filters. Filtrate was analysed for coloured dissolved organic matter absorbance and fluorescence for the characterization of potential changes in the organic matter pool during the flocculation process. Retentate on the filter was subjected to persulfate digestion of organic particles and metal oxyhydroxides (pH <2.3), and the digestion supernatants were analysed for metal concentrations. The laboratory experiments showed strong transfer of Al and Fe already at salinity 0–2 to newly formed organic-dominated flocs that were generally larger than 80 µm. Very strong coupling between the decrease in humic-like fluorescence and the increase in organic-bound Al demonstrated that Al transfer to the flocs was stronger than that of Fe. The flocs in the suspended particle pool were complemented by a smaller population of Al and Fe oxyhydroxide-dominated flocculi (median size 11 µm) after pH exceeded ca. 5.5. Cobalt and Mn transfer to the particle pool was weak, although some transfer to Mn oxyhydroxides as well as Co association with the flocs took place. Up to 50 % of Cu was found to be bound to humic substances in the flocs in the river waters and this proportion did not significantly change during mixing with seawater. The findings of this study demonstrate that salinity and pH are important independent but connected controls of the flocculation behavior of dissolved metals from boreal acid sulphate soils and the seaward transport and environmental consequences of the metals in the marine environment.

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Section: Implications For Seaward Metal Transportmentioning

confidence: 78%

Section: Implications For Seaward Metal Transportmentioning

confidence: 86%

Section: Implications For Seaward Metal Transportmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

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Estuarine flocculation dynamics of organic carbon and metals from boreal acid sulphate soils

Virtasalo

Österholm

Asmala³

2023

Preprint

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“…Specifically, it was concluded that Al, Fe, and Cu are deposited with organic matter close to the Vöyrinjoki river mouth, whereas Cd, Co, Ni, and Zn are preferentially transported farther out at sea, where they co-precipitate and are deposited with Mn oxyhydroxides (Nordmyr et al, 2008a, b;Nystrand et al, 2016). However, a recent study of seafloor sediments shows that Cu, Cd, Co, Ni, and Zn are all enriched at least 26 km away from the mouths of the nearby Laihianjoki and Sulvanjoki rivers, whereas the Mn enrichment extends less than 14 km from the river mouths (Virtasalo et al, 2020). This discrepancy between the observed seafloor metal distribution and the previously concluded seaward transport behaviour of the metals calls for further investigation of the flocculation process in boreal humus-rich rivers that are strongly impacted by acidity and metal release from AS soils.…”

Section: Introductionmentioning

confidence: 99%

Estuarine flocculation dynamics of organic carbon and metals from boreal acid sulfate soils

Virtasalo¹,

Österholm²,

Asmala³

2023

Biogeosciences

Self Cite

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Abstract. Flocculation of riverine dissolved organic matter to the particulate form in estuaries is an important mechanism for capturing dissolved metals to newly formed organic particles, regulating the metal transport from land to sea. The process is particularly relevant for rivers draining boreal acid sulfate soils of western Finland, which are known to deliver large amounts of trace metals with detrimental environmental consequences for the recipient estuaries in the eastern Gulf of Bothnia in the northern Baltic Sea. This is the first study to investigate dissolved metal (Al, Fe, Mn, Co, and Cu) association with flocculating organic particles in the laboratory, by mixing of acidic metal-rich water from acid-sulfate-soil-impacted rivers and particle-free artificial seawater. Water samples were collected in April 2021 from the Laihianjoki and Sulvanjoki rivers in western Finland. Experiments with an in situ laser-diffraction-based particle size distribution sensor and a multiparameter water quality sonde were run to continuously monitor the development of a suspended particle pool over the salinity gradient from 0 to 6, corresponding to the salinity range observed in these estuarine systems. Flocculator experiments with discrete salinity treatments were carried out to investigate metal behaviour with the collection of flocculated material on glass fibre filters. Filtrate was analysed for coloured dissolved-organic-matter absorbance and fluorescence for the characterization of potential changes in the organic matter pool during the flocculation process. Retentate on the filter was subjected to persulfate digestion of organic particles and metal oxyhydroxides (pH < 2.3), and the digestion supernatants were analysed for metal concentrations. The laboratory experiments showed strong transfer of Al and Fe already at a salinity of 0–2 to newly formed organically dominated flocs that were generally larger than 80 µm. Very strong coupling between the decrease in humic fluorescence and the increase in organically bound Al demonstrated that Al transfer to the flocs was stronger than that of Fe. The flocs in the suspended particle pool were complemented by a smaller population of Al- and Fe-oxyhydroxide-dominated flocculi (median size of 11 µm) after pH exceeded ca. 5.5. Cobalt and Mn transfer to the particle pool was weak, although some transfer to Mn oxyhydroxides as well as Co association with the flocs took place. Up to 50 % of Cu was found to be bound to humic substances in the flocs in the river waters, and this proportion did not significantly change during mixing with seawater. The findings of this study demonstrate that salinity and pH are important independent but connected controls of the flocculation behaviour of dissolved metals from boreal acid sulfate soils and the seaward transport and environmental consequences of the metals in the marine environment.

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Statistical approach to identify variables predicting sulphide clay occurrence in southern Finland

Saresma

Löfman

Kosonen

et al. 2023

Bull Eng Geol Environ

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Acid sulphate soil and sulphide-bearing sediments cause various challenges in construction projects and land use planning, as well as harmful environmental effects. Fine-grained sulphide sediments were mainly formed in coastal areas during the Litorina Sea water phase at approximately 7000 BP in the capital region of Finland, but not all these sediments contain sulphide clay. In this study, environmental and material property variables related to the depositional conditions of sulphide clay were selected for statistical analyses to find their association with the occurrence of sulphide. The datasets consisted of sulphide investigations by the City of Espoo, the City of Helsinki, and the Geological Survey of Finland. Statistically significant associations were found in the study area between the occurrence of sulphide and enumerative variables (i.e., sediment organic content, total clay depth, topographic class in the Litorina Sea phase, and water depth) in the Litorina Sea phase. Locations where sulphide clay is especially likely to occur consist of organic-rich (≥ 2%) thick clay (≥ 15 m) deposits in a topographically narrow depression with deep Litorina water (≥ 30 m), or where there is a moderate depth clay (3–5 m) in a local depression with shallow Litorina water (10–20 m). The best individual predictor for sulphide clay occurrence in the study area was found to be the sediment organic content, and, together with sediment water content, these variables very accurately predicted the occurrence of sulphide clay. In addition, clay depth is a very good predictor and, together with the topographic class narrow depression and the Litorina water depth or current elevation, can be used to predict sulphide occurrence.

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Enrichment of trace metals from acid sulfate soils in sediments of the Kvarken Archipelago, eastern Gulf of Bothnia, Baltic Sea

Cited by 13 publications

References 77 publications

Estuarine flocculation dynamics of organic carbon and metals from boreal acid sulphate soils

Estuarine flocculation dynamics of organic carbon and metals from boreal acid sulphate soils

Estuarine flocculation dynamics of organic carbon and metals from boreal acid sulfate soils

Statistical approach to identify variables predicting sulphide clay occurrence in southern Finland

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