Hypoxia in the Holocene Baltic Sea : Comparing modern versus past intervals using sedimentary trace metals

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dc.contributor.author van Helmond, Niels A. G. M.
dc.contributor.author Jilbert, Tom
dc.contributor.author Slomp, Caroline P.
dc.date.accessioned 2020-08-20T00:38:31Z
dc.date.available 2021-12-17T22:02:50Z
dc.date.issued 2018-08-20
dc.identifier.citation van Helmond , N A G M , Jilbert , T & Slomp , C P 2018 , ' Hypoxia in the Holocene Baltic Sea : Comparing modern versus past intervals using sedimentary trace metals ' , Chemical Geology , vol. 493 , pp. 478-490 . https://doi.org/10.1016/j.chemgeo.2018.06.028
dc.identifier.other PURE: 115085492
dc.identifier.other PURE UUID: 84768f26-4913-4caa-96c7-d8e0d015b328
dc.identifier.other WOS: 000439574000039
dc.identifier.other Scopus: 85049443217
dc.identifier.other ORCID: /0000-0001-8165-0168/work/47429729
dc.identifier.uri http://hdl.handle.net/10138/318417
dc.description.abstract Anthropogenic nutrient input has caused a rapid expansion of bottom water hypoxia in the Baltic Sea over the past century. Two earlier intervals of widespread hypoxia, coinciding with the Holocene Thermal Maximum (HTMHI; 8-4 ka before present; BP) and the Medieval Climate Anomaly (MCA(HI); similar to 1200-750 years BP), have been identified from Baltic Sea sediments. Here we present sediment records from two sites in the Baltic Sea, and compare the trace metal (As, Ba, Cd, Cu, Mo, Ni, Pb, Re, Sb, Tl, U, V, Zn) enrichments during all three hypoxic intervals. Distinct differences are observed between the intervals and the various elements, highlighting the much stronger perturbation of trace metal cycles during the modern hypoxic interval. Both Mo and U show a strong correlation with C-org and very high absolute concentrations, indicative of frequently euxinic bottom waters during hypoxic intervals. During the modern hypoxic interval (Modern(HI)) comparatively less Mo is sequestered relative to C-org than in earlier intervals. This suggests partial drawdown of the water column Mo inventory in the modern water column due to persistent euxinia and only partial replenishment of Mo through North Sea inflows. Molybdenum contents in modern sediments are likely also affected by the recent slowdown in input of Mo in association with deposition of Fe and Mn oxides. Strong enrichments of U in recent sediments confirm that the Modern(HI) is more intense than past intervals. These results suggest that U is a more reliable indicator for the intensity of bottom water deoxygenation in the Baltic Sea than Mo. Sedimentary Re enrichment commences under mildly reducing conditions, but this element is not further enriched under more reducing conditions. Enrichments of V are relatively minor for the MCA(HI) and Modern(HI), possibly due to strong reservoir effects on V in the water column, indicating that V is unreliable as an indicator for the intensity of bottom water hypoxia in this setting. Furthermore, Ba profiles are strongly influenced by post-depositional remobilization throughout the Holocene. The strong relationship between C-org and Ni, Tl and particularly Cu suggests that these trace metals can be used to reconstruct the C-org flux into the sediments. Profiles of As, Sb and Cd and especially Pb and Zn are strongly influenced by anthropogenic pollution. en
dc.format.extent 13
dc.language.iso eng
dc.relation.ispartof Chemical Geology
dc.rights cc_by_nc_nd
dc.rights.uri info:eu-repo/semantics/openAccess
dc.subject Redox conditions
dc.subject Anthropogenic pollution
dc.subject Aqueous trace metal depletion
dc.subject Molybdenum
dc.subject Uranium
dc.subject LANDSORT DEEP
dc.subject PORE WATERS
dc.subject BLACK SHALE
dc.subject MOLYBDENUM
dc.subject 1171 Geosciences
dc.subject 1172 Environmental sciences
dc.title Hypoxia in the Holocene Baltic Sea : Comparing modern versus past intervals using sedimentary trace metals en
dc.type Article
dc.contributor.organization Helsinki Institute of Sustainability Science (HELSUS)
dc.contributor.organization Ecosystems and Environment Research Programme
dc.contributor.organization Marine Ecosystems Research Group
dc.contributor.organization Aquatic Biogeochemistry Research Unit (ABRU)
dc.contributor.organization Doctoral Programme in Interdisciplinary Environmental Sciences
dc.description.reviewstatus Peer reviewed
dc.relation.doi https://doi.org/10.1016/j.chemgeo.2018.06.028
dc.relation.issn 0009-2541
dc.rights.accesslevel openAccess
dc.type.version acceptedVersion

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