| 1. |
- Hogfors-Ronnholm, Eva, et al.
(författare)
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Gallionella and Sulfuricella populations are dominant during the transition of boreal potential to actual acid sulfate soils
- 2022
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Ingår i: Communications Earth & Environment. - : Springer Nature. - 2662-4435. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Acid sulfate soils release metal laden, acidic waters that affect the environment, buildings, and human health. In this study, 16S rRNA gene amplicons, metagenomes, and metatranscriptomes all demonstrated distinct microbial communities and activities in the unoxidized potential acid sulfate soil, the overlying transition zone, and uppermost oxidized actual acid sulfate soil. Assembled genomes and mRNA transcripts also suggested abundant oxidized acid sulfate soil populations that aligned within the Gammaproteobacteria and Terracidiphilus. In contrast, potentially acid tolerant or moderately acidophilic iron oxidizing Gallionella and sulfur metabolizing Sulfuricella dominated the transition zone during catalysis of metal sulfide oxidation to form acid sulfate soil. Finally, anaerobic oxidation of methane coupled to nitrate, sulfate, and ferric reduction were suggested to occur in the reduced parent sediments. In conclusion, despite comparable metal sulfide dissolution processes e.g., biomining, Gallionella and Sulfuricella dominated the community and activities during conversion of potential to actual acid sulfate soils.
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| 2. |
- Högfors-Rönnholm, Eva, et al.
(författare)
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Targeting oxidation sites on boreal acid sulfate soil macropore surfaces mitigates acid and metal release to recipient water streams
- 2023
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Ingår i: Applied Geochemistry. - : Elsevier. - 0883-2927 .- 1872-9134. ; 158
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Tidskriftsartikel (refereegranskat)abstract
- When reduced sulfidic parent sediments are oxidized, they become acid sulfate soils and discharge metal laden acidic solutions that can damage the environment, infrastructure, and human health. Consequently, methods to mitigate the effect of acid sulfate soils are a priority in affected areas. In this study, acid sulfate soil core samples, consisting of a natural network of preferential-flow soil macropores with defined macropore surfaces and inner cores of denser clay, were characterized and subjected to treatments with calcium carbonate and peat suspensions, or combinations thereof. The effects on the geochemistry and microbial communities were examined on both macropore surfaces and in inner cores. Although transport of treatment substances into the inner cores was demonstrated, no substantial effects were found on the geochemistry and microbial community that consisted of bacterial taxa commonly identified in acid mine drainage. In contrast, positive treatment effects were clearly detected on macropore surfaces and the most promising mitigation effects were detected for treatments combining calcium carbonate and peat suspensions. These treatments increased the pH of the macropore surfaces, added an electron donor in the form of peat, and significantly decreased the relative abundance of acidophilic bacterial populations while shifting the microbial community towards species typically growing at circumneutral pH values. These new environmental conditions were favorable for iron reduction that resulted in a positive effect on permeate quality. The study presents novel data regarding the important differences between acid sulfate soil macropore surfaces and inner cores, as well as their diverse biogeochemical characteristics. It further establishes that the major oxidation-reduction processes occur at the macropore surfaces, and that the combination treatment was the most effective at mitigating the negative environmental effects.
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| 3. |
- Johnson, Anders, et al.
(författare)
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Dredging and deposition of metal sulfide rich river sediments results in rapid conversion to acid sulfate soil materials
- 2022
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Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 813
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Tidskriftsartikel (refereegranskat)abstract
- Sediments along the Baltic Sea coast can contain considerable amounts of metal sulfides that if dredged and the spoils deposited such that they are exposed to air, can release high concentrations of acid and toxic metals into recipient water bodies. Two river estuaries in western Finland were dredged from 2013 to 2018 and the dredge spoils were deposited on land previously covered with agricultural limestone to buffer the pH and mitigate acid and metal release. In this study, the geochemistry and 16S rRNA gene amplicon based bacterial communities were investigated over time to explore whether the application of lime prevented a conversion of the dredge spoils into acid producing and metal releasing soil. The pH of the dredge spoils decreased with time indicating metal sulfide oxidation and resulted in elevated sulfate concentrations along with a concomitant release of metals. However, calculations indicated only approximately 5% of the added lime had been dissolved. The bacterial communities decreased in diversity with the lowering of the pH as taxa most similar to extremely acidophilic sulfur, and in some cases iron, oxidizing Acidithiobacillus species became the dominant characterized genus in the deposited dredge spoils as the oxidation front moved deeper. In addition, other taxa characterized as involved in oxidation of iron or sulfur were identified including Gallionella, Sulfuricurvum, and Sulfurimonas. These data suggest there was a rapid conversion of the dredge spoils to severely acidic soil similar to actual acid sulfate soil and that the lime placed on the land prior to deposition of the spoils, and later ploughed into the dry dredge spoils, was insufficient to halt this process. Hence, future dredging and deposition of dredge spoils containing metal sulfides should not only take into account the amount of lime used for buffering but also its grain size and mixing into the soil.
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