A1 Refereed original research article in a scientific journal
Sedimentary phosphorus burial in three contrasting boreal lakes in Finland
Authors: Laakso Johanna, Jilbert Tom, Saarinen Timo
Publisher: SPRINGER JAPAN KK
Publication year: 2023
Journal: Limnology
Journal name in source: LIMNOLOGY
Journal acronym: LIMNOLOGY
Number of pages: 13
ISSN: 1439-8621
eISSN: 1439-863X
DOI: https://doi.org/10.1007/s10201-023-00730-9
Web address : https://doi.org/10.1007/s10201-023-00730-9
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/181425445
Abstract
Permanent phosphorus (P) burial in sediment regulates lake trophic state over long timescales, but the controls on P burial are only partially understood. A diversity of biogeochemical settings may be found in lake sediments, which may have a strong impact on the processes controlling P burial from one location to another. Here, we investigate early diagenesis of P in three contrasting lakes in Southwest Finland. Eutrophic Lake Koylionjarvi and mesotrophic Lake Pyhajarvi have a history of nutrient loadings from agriculture, while Lake Vahajarvi is an oligotrophic small forest lake, leading to potentially contrasting sediment biogeochemical dynamics. We combined porewater data and solid-phase sediment geochemical data to identify P phases in each system and investigate the dominant processes controlling P burial. Porewater profiles showed opposite gradients between the oligotrophic and the mesotrophic/eutrophic systems, implying net diffusive fluxes into and out of the sediments, respectively. Furthermore, sediment P data showed contrasting P speciation. Reactive P is buried in all systems, but the role of reducible iron (Fe) oxides in P retention is greater in mesotrophic/eutrophic lakes. In the oligotrophic system, aluminium (Al) oxides controlled P sorption into the sediment after diffusion from lake water. Evidence for vivianite formation was found only in the mesotrophic Lake Pyhajarvi sediment, where 42-47% of total P was released in a Fe(II)-P specific extraction from the deeper part of the sediment column and vivianite crystals could be isolated from sediment samples.
Permanent phosphorus (P) burial in sediment regulates lake trophic state over long timescales, but the controls on P burial are only partially understood. A diversity of biogeochemical settings may be found in lake sediments, which may have a strong impact on the processes controlling P burial from one location to another. Here, we investigate early diagenesis of P in three contrasting lakes in Southwest Finland. Eutrophic Lake Koylionjarvi and mesotrophic Lake Pyhajarvi have a history of nutrient loadings from agriculture, while Lake Vahajarvi is an oligotrophic small forest lake, leading to potentially contrasting sediment biogeochemical dynamics. We combined porewater data and solid-phase sediment geochemical data to identify P phases in each system and investigate the dominant processes controlling P burial. Porewater profiles showed opposite gradients between the oligotrophic and the mesotrophic/eutrophic systems, implying net diffusive fluxes into and out of the sediments, respectively. Furthermore, sediment P data showed contrasting P speciation. Reactive P is buried in all systems, but the role of reducible iron (Fe) oxides in P retention is greater in mesotrophic/eutrophic lakes. In the oligotrophic system, aluminium (Al) oxides controlled P sorption into the sediment after diffusion from lake water. Evidence for vivianite formation was found only in the mesotrophic Lake Pyhajarvi sediment, where 42-47% of total P was released in a Fe(II)-P specific extraction from the deeper part of the sediment column and vivianite crystals could be isolated from sediment samples.
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