Vivianite formation and its role in phosphorus retention in Lake Ørn, Denmark

O’Connell, David; Jensen, Marlene Mark; Jakobsen, Rasmus; Thamdrup, Bo; Andersen, Thorbjørn Joest; Kovács, András; Hansen, Hans Christian Bruun

doi:10.1016/j.chemgeo.2015.05.002

Cited by 60 publications

(27 citation statements)

References 71 publications

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“…7) likely represent freshly formed vivianite that has not been subject to major diagenetic alternation. Similar crystals were for instance observed in surface sediments in the Bothnian Sea (Egger et al, 2015a) and lake Ørn in Denmark (O'Connell et al, 2015). In contrast, the less crystalline aggregates at 12.7 m (Fig.…”

Section: Diagenesis and Vivianite Burial In The Landsort Deepsupporting

confidence: 51%

Vivianite is a key sink for phosphorus in sediments of the Landsort Deep, an intermittently anoxic deep basin in the Baltic Sea

2016

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a b s t r a c t Phosphorus (P) is an essential nutrient for marine organisms. Its burial in hypoxic and anoxic marine basins is still incompletely understood. Recent studies suggest that P can be sequestered in sediments of such basins as reduced iron (Fe)-P but the exact phase and the underlying mechanisms that lead to its formation are unknown. In this study, we investigated sediments from the deepest basin in the Baltic Sea, the Landsort Deep (site M0063), that were retrieved during the Integrated Ocean Drilling Project (IODP) Baltic Sea Paleoenvironment Expedition 347. The record comprises the whole brackish/marine Littorina Sea stage including past intervals of extensive hypoxia in the Baltic Sea that occurred during the Holocene Thermal Maximum (HTM HI ) and the Medieval Climate Anomaly (MCA1 HI and MCA2 HI ). Various redox proxies (e.g. the presence of laminations and high Mo contents) suggest almost permanent bottom water hypoxia during the Littorina Sea stage in the Landsort Deep. The bottom waters were likely even seasonally anoxic or sulfidic during the MCA1 HI and MCA2 HI , and permanently sulfidic during the HTM HI . With the use of micro-analysis of sieved minerals (SEM-EDS, XRD and synchrotron-based XAS), we show that Mn-and Mgrich vivianite crystals are present at various depths in the Littorina Sea sediments. We also have indications for vivianite in the MCA1 HI , MCA2 HI and HTM HI deposits. The formation of vivianite thus likely explains the high Febound P fraction throughout the whole Littorina Sea stage. Shuttling of Fe and Mn from the shelves into the basin and high inputs of P in settling organic matter are likely key drivers for vivianite formation. Our study shows that vivianite can likely form in near-surface sediments under a broad range of bottom water redox conditions, varying from hypoxic and anoxic to sulfidic.

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Section: Diagenesis and Vivianite Burial In The Landsort Deepsupporting

confidence: 51%

Vivianite is a key sink for phosphorus in sediments of the Landsort Deep, an intermittently anoxic deep basin in the Baltic Sea

2016

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“…In most marine sediments, Fe is mainly captured in Fe-sulfides and no Fe 2+ is left to precipitate with PO 4 , thereby preventing the precipitation of vivianite. In many lake sediments, in contrast, bottom water SO 4 2− concentrations are low and may allow for accumulation of Fe 2+ and PO 4 in the porewater and subsequent authigenic vivianite formation (Nriagu and Dell 1974;Rothe et al 2014;O'Connell et al 2015). In sediments of brackish/marine basins, an excess supply of reactive Fe-oxides may also act as a key driver of vivianite formation (Jilbert and Slomp 2013;Dijkstra et al 2016;Reed et al 2016).…”

Section: Communicated By David Reide Corbettmentioning

confidence: 99%

Holocene Refreshening and Reoxygenation of a Bothnian Sea Estuary Led to Enhanced Phosphorus Burial

Dijkstra

Krupinski

Yamane

et al. 2017

Estuaries and Coasts

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Salinity variations in restricted basins like the Baltic Sea can alter their vulnerability to hypoxia (i.e., bottom water oxygen concentrations <2 mg/l) and can affect the burial of phosphorus (P), a key nutrient for marine organisms. We combine porewater and solid-phase geochemistry, microanalysis of sieved sediments (including XRD and synchrotron-based XAS), and foraminiferal δ 18 O and δ 13 C analyses to reconstruct the bottom water salinity, redox conditions, and P burial in the Ångermanälven estuary, Bothnian Sea. Our sediment records were retrieved during the Integrated Ocean Drilling Program (IODP) Baltic Sea Paleoenvironment Expedition 347 in 2013. We demonstrate that bottom waters in the Ångermanälven estuary became anoxic upon the intrusion of seawater in the early Holocene, like in the central Bothnian Sea. The subsequent refreshening and reoxygenation, which was caused by gradual isostatic uplift, promoted P burial in the sediment in the form of Mn-rich vivianite. Vivianite authigenesis in the surface sediments of the more isolated part of the estuary ultimately ceased, likely due to continued refreshening and an associated decline in productivity and P supply to the sediment. The observed shifts in environmental conditions also created conditions for postdepositional formation of authigenic vivianite, and possibly apatite formation, at ∼8 m composite depth. These salinityrelated changes in redox conditions and P burial are highly relevant in light of current climate change. The results specifically highlight that increased freshwater input linked to global warming may enhance coastal P retention, thereby contributing to oligotrophication in both coastal and adjacent open waters.

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“…Additionally, the coupled biogeochemical cycles of other redox sensitive elements such as sulfur and carbon have been shown to play important and complex roles in phosphorus mobility (Gächter and Müller, 2003;Joshi et al, 2015;O'Connell et al, 2015). For example, high bottom-water sulfate concentrations have been shown to increase aqueous P in sediments by decreasing the permanent mineralogical removal of P within vivianite [Fe 3 (PO 4 ) 2(s) ] and by decreasing the abundance of iron(III) oxyhydroxides near to the SWI (Caraco et al, 1989).…”

Section: T Parsons Et Al: Sediment Phosphorus Speciation and Mobmentioning

confidence: 99%

Sediment phosphorus speciation and mobility under dynamic redox conditions

Parsons¹,

Rezanezhad²,

O’Connell³

et al. 2017

Biogeosciences

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Abstract. Anthropogenic nutrient enrichment has caused phosphorus (P) accumulation in many freshwater sediments, raising concerns that internal loading from legacy P may delay the recovery of aquatic ecosystems suffering from eutrophication. Benthic recycling of P strongly depends on the redox regime within surficial sediment. In many shallow environments, redox conditions tend to be highly dynamic as a result of, among others, bioturbation by macrofauna, root activity, sediment resuspension and seasonal variations in bottom-water oxygen (O 2 ) concentrations. To gain insight into the mobility and biogeochemistry of P under fluctuating redox conditions, a suspension of sediment from a hypereutrophic freshwater marsh was exposed to alternating 7-day periods of purging with air and nitrogen gas (N 2 ), for a total duration of 74 days, in a bioreactor system. We present comprehensive data time series of bulk aqueous-and solidphase chemistry, solid-phase phosphorus speciation and hydrolytic enzyme activities demonstrating the mass balanced redistribution of P in sediment during redox cycling. Aqueous phosphate concentrations remained low (∼ 2.5 µM) under oxic conditions due to sorption to iron(III) oxyhydroxides. During anoxic periods, once nitrate was depleted, the reductive dissolution of iron(III) oxyhydroxides released P. However, only 4.5 % of the released P accumulated in solution while the rest was redistributed between the MgCl 2 and NaHCO 3 extractable fractions of the solid phase. Thus, under the short redox fluctuations imposed in the experiments, P remobilization to the aqueous phase remained relatively limited. Orthophosphate predominated at all times during the experiment in both the solid and aqueous phase. Combined P monoesters and diesters accounted for between 9 and 16 % of sediment particulate P. Phosphatase activities up to 2.4 mmol h −1 kg −1 indicated the potential for rapid mineralization of organic P (P o ), in particular during periods of aeration when the activity of phosphomonoesterases was 37 % higher than under N 2 sparging. The results emphasize that the magnitude and timing of internal P loading during periods of anoxia are dependent on both P redistribution within sediments and bottom-water nitrate concentrations.

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Vivianite formation and its role in phosphorus retention in Lake Ørn, Denmark

Cited by 60 publications

References 71 publications

Vivianite is a key sink for phosphorus in sediments of the Landsort Deep, an intermittently anoxic deep basin in the Baltic Sea

Vivianite is a key sink for phosphorus in sediments of the Landsort Deep, an intermittently anoxic deep basin in the Baltic Sea

Holocene Refreshening and Reoxygenation of a Bothnian Sea Estuary Led to Enhanced Phosphorus Burial

Sediment phosphorus speciation and mobility under dynamic redox conditions

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