Impacts of a deep reactive layer on sedimentary phosphorus dynamics in a boreal lake recovering from eutrophication

Autor:	Jukka Horppila, Sami A. Jokinen, Asko Simojoki, Sarianna Salminen, Timo Saarinen, Tom Jilbert, Ulpu Mattus-Kumpunen, Saija Saarni, Juha Niemistö
Přispěvatelé:	Ecosystems and Environment Research Programme, Department of Agricultural Sciences, Sphagnum moss as a growing medium, Environmental Soil Science, Lake Ecosystem Dynamics, Helsinki Institute of Sustainability Science (HELSUS)
Rok vydání:	2020
Předmět:	0106 biological sciences Biogeochemical cycle 010504 meteorology & atmospheric sciences 119 Other natural sciences HYPOXIA Aquatic Science 01 natural sciences MANGANESE MEDIATED ANAEROBIC OXIDATION METHANE 1172 Environmental sciences 0105 earth and related environmental sciences RELEASE FRESH-WATER IRON 010604 marine biology & hydrobiology Hypoxia (environmental) Sediment Biogeochemistry Deoxygenation Authigenic 6. Clean water Diagenesis ORGANIC-MATTER 13. Climate action Restoration Environmental chemistry BALTIC SEA Environmental science Vivianite VIVIANITE FORMATION Eutrophication Remineralization
Zdroj:	Hydrobiologia. 847:4401-4423
ISSN:	1573-5117 0018-8158
DOI:	10.1007/s10750-020-04289-9
Popis:	Using biogeochemical analyses of sediments and porewaters, we investigate the legacy of a brief, intense period of eutrophication on sedimentary phosphorus (P) cycling in a boreal lake (Enonselkä basin, Lake Vesijärvi, Finland). Point-source sewage inputs in the twentieth century caused deoxygenation of the lake and accelerated the focusing of iron (Fe) and manganese (Mn) oxides into deeper areas. Early diagenesis under Fe–Mn-rich conditions now favors rapid burial of P in these areas, likely as a combination of both oxide-bound P phases and authigenic manganous vivianite. A new P budget for Enonselkä basin shows that P burial causes an annual drawdown of 1.2% (± 0.2%) of the surface sediment P inventory, supporting a long-term trend towards recovery since the construction of a wastewater treatment plant in the mid-1970s. However, remineralization of organic matter and associated dissolution of Fe–Mn oxides continues to regenerate P from a deep reactive layer (20–60 cm depth) deposited at the height of past eutrophication, leading to an upwards diffusive flux of dissolved phosphate towards the surface sediments. The magnitude of this flux is similar to that of external P loading to the lake. The combined incoming fluxes of P are likely to retard the complete recovery from eutrophication by decades, despite ongoing restoration actions.
Databáze:	OpenAIRE
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