The lake as an iron sink - new insights on the role of iron speciation

Björnerås, Caroline; Persson, Per; Weyhenmeyer, Gesa A.; Hammarlund, Dan; Kritzberg, Emma S.

doi:10.1016/j.chemgeo.2021.120529

Cited by 13 publications

(10 citation statements)

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“…We further observed clearly elevated S AR in the sediment record of Lake Bolmen during the period of elevated atmospheric S deposition in the region, and the presence of FeS in the sediments, demonstrating that conditions suitable for sulfide precipitation existed in the lake. Based on those results, and considering that around 70% of the Fe entering the lake is lost to the sediments (Björnerås et al, 2021), we suggest that formation of FeS of low solubility in the sediments is a potentially important Fe sink.…”

Section: The Role Of S Deposition As a Driver Of Increasing Lake Wate...mentioning

confidence: 71%

“…However, since only the most superficial sediment sample was strikingly enriched in Fe, we believe that the gradual increase in Fe AR in the upper part of the record—along with elements which are not redox sensitive, such as Si and Al—is mainly a result of increased loading of Fe from the catchment, rather than substantial upward migration of Fe in the sediments. Lake Bolmen has been demonstrated to be an efficient sink of inflowing Fe, with temporal variations in Fe concentrations mainly determined by catchment loads of Fe (Björnerås et al., 2021). Nevertheless, it is possible that conditions favorable for sediment release of Fe to overlying waters develop occasionally in the lake, and that high availability of organic matter for complexation potentially enables released Fe to be kept in solution in oxic lake water.…”

Section: Discussionmentioning

confidence: 99%

“…Fe originates primarily from sources in the catchment, and the association with DOM is a prerequisite for the transport of Fe from soils to waters, since DOM increases Fe solubility in oxic circum‐neutral waters (Stumm & Morgan, 1996). However, lake‐internal processes, such as aggregation and sedimentation, remove Fe from the water column (Neubauer et al., 2013; von Wachenfeldt et al., 2008) and are important in determining the distribution of Fe between the water column and the sediments (Björnerås et al., 2021; Nürnberg & Dillon, 1993). Hence, Fe accumulation in lake sediments are determined by both catchment supply and in‐lake processes (Engstrom & Wright, 1984).…”

Section: Introductionmentioning

confidence: 99%

“…In this study we investigated the role of declining S deposition as a driver of increasing lake water Fe concentrations in Lake Bolmen in southern Sweden, focusing on the importance of Fe binding by sulfides in sediments. Although Lake Bolmen is a major sink for Fe and DOM (Björnerås et al., 2021), a pronounced browning of the lake water has been observed during the last decades (Kritzberg, 2017). The browning poses a challenge to the production of drinking water from the lake, which provides water to more than half a million people.…”

Section: Introductionmentioning

confidence: 99%

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Sediment Records Shed Light on Drivers of Decadal Iron Concentration Increase in a Boreal Lake

et al. 2022

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Iron (Fe) concentrations are increasing in lakes and running waters over a broad geographical scale (Björnerås et al., 2017). Together with dissolved organic matter (DOM), Fe is contributing to an ongoing browning-that is, an increase in water color in freshwaters-with consequences for light penetration and thermal stratification, affecting ecosystem functions such as primary productivity, as well as for the ecosystem services that aquatic systems provide (Kritzberg et al., 2019). Fe originates primarily from sources in the catchment, and the association with DOM is a prerequisite for the transport of Fe from soils to waters, since DOM increases Fe solubility in oxic circum-neutral waters (Stumm & Morgan, 1996). However, lake-internal processes, such as aggregation and sedimentation, remove Fe from the water column (Neubauer et al., 2013;von Wachenfeldt et al., 2008) and are important in determining the distribution of Fe between the water column and the sediments (Björnerås Abstract Increasing iron (Fe) concentrations are found in lakes on a wide geographical scale but exact causes are still debated. The observed trends might result from increased Fe loading from the terrestrial catchment, but also from changes in how Fe distributes between the water column and the sediments. To get a better understanding of the causes we investigated whether there has been any change in the sediment formation of Fe sulfides (FeS) as an Fe sink in response to declining atmospheric sulfur (S) deposition during recent decades. For our study, we chose Lake Bolmen in southern Sweden, a lake for which we confirmed that Fe concentrations in the water column have strongly increased along with water color during 1966-2018. Our investigations showed that Fe accumulation and speciation varied independently of S accumulation patterns in the Lake Bolmen sediment record. Thus, we were not able to relate the positive trend in Fe concentrations to reduced FeS binding in the sediments. Furthermore, we found that Fe accumulation rates increased along with lake water Fe concentrations, indicating that increased catchment loading rather than a change in the distribution between the sediments and the water column has driven the increase in Fe concentrations. The increased loading may be due to land-use change in the form of an extensive expansion of coniferous forest during the past century. Altered forest management practices and increased precipitation may have led to enhanced weathering and erosion of organic soil layers under aging coniferous forest. Plain Language Summary Iron concentrations are increasing in freshwaters in the NorthernHemisphere. One possible explanation is a decline in sulfur deposition in recent decades, which may have led to lower iron sulfide formation in soils and sediments, and thus to increased lake water iron concentrations. We tested this hypothesis by exploring iron concentrations in water and sediments of Lake Bolmen in southern Sweden in relation to changes in sulfur deposition, climate and catchment land-use. We ...

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Section: The Role Of S Deposition As a Driver Of Increasing Lake Wate...mentioning

confidence: 71%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Sediment Records Shed Light on Drivers of Decadal Iron Concentration Increase in a Boreal Lake

et al. 2022

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“…This difference in oxidation state is likely a result of the targeting of Fe-rich particles for microXANES, which may have a slightly different speciation than particles in which iron is less concentrated than in oxides or sulfide. In lakes this could include clays with oxidized iron (Björnerås et al 2021). Mössbauer analyses of the sediment trap samples from Brownie Lake indicated that about 40% of iron in sediment traps was present in Fe(II) and Fe(III) bearing clays (Islam 2022).…”

Section: Assessmentmentioning

confidence: 99%

Evaluation of preservation protocols for oxygen-sensitive minerals within laminated aquatic sediments

Ledesma¹,

Islam²,

Swanner³

2022

Preprint

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Laminated sediments can record seasonal changes in sedimentation of material from anoxic waters, including minerals of the redox-sensitive elements Fe, Mn, and S that form under varying oxygen levels, mineral saturation conditions, and from microbial metabolism. However, preserving both the oxygen-sensitive minerals for identification is challenging when preservation of the spatial arrangement of laminae is also required. In this study, we compare methods for embedding sedimentary materials from anoxic waters and sediments from Brownie Lake, Minnesota, USA for analysis of the redox speciation for Fe, Mn, and S using synchrotron-based X-ray absorption near edge spectroscopy (XANES). We found that acetone dehydration and resin replacement in a 100% N2 glovebox successfully preserved the speciation of Fe and Mn minerals within laminated sediments. However, acetone removed some sulfur species from sediments, and epoxies contained sulfur species, which challenged identification of native sulfur species. Results from this study will aid researchers who are interested in spatial analysis of oxygen sensitive sediments, soils, or microbial mats in choosing a preservation method.

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Browning of boreal lakes: Do public perceptions and governance align with the biological foundations?

Albrecht

Hannonen

Palacín-Lizarbe

et al. 2023

Ecological Applications

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Browning of surface waters, also known as brownification, is a process of decreasing water transparency, particularly in boreal lakes surrounded by intensively managed forests and wetlands. In this paper, we review the ecological consequences and ecosystem-based management (EBM) of browning through a systematic review approach and adopt an interdisciplinary approach to formulating new governance of this complex phenomenon.To understand the effects of browning on the recreational value of freshwaters, we present primary survey data on public perceptions of recreational fishing tourists on water quality in Finland. We identify a need to develop EBM beyond the EU's Water Framework Directive (WFD) to fully account for the extensive implications of browning. We also highlight the need for a better understanding of the within-lake microbial processes to estimate the browning-associated changes in the greenhouse gas balance of lakes.Tourist perceptions of the quality of waterbodies in Finland were largely in agreement with the general proportion of waterbodies classified in a good or excellent ecological status class, but these perceptions may be detached from biological quality assessment criteria. Consequently, we suggest that the EBM of inland waters should improve the utilization of information on not only biogeochemical processes but also users' perspectives on aquatic ecosystems beyond the EU WFD.

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The lake as an iron sink - new insights on the role of iron speciation

Cited by 13 publications

References 80 publications

Sediment Records Shed Light on Drivers of Decadal Iron Concentration Increase in a Boreal Lake

Sediment Records Shed Light on Drivers of Decadal Iron Concentration Increase in a Boreal Lake

Evaluation of preservation protocols for oxygen-sensitive minerals within laminated aquatic sediments

Browning of boreal lakes: Do public perceptions and governance align with the biological foundations?

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