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| Titel |
Historical TOC concentration minima during peak sulfur deposition in two Swedish lakes |
| VerfasserIn |
P. Bragée, F. Mazier, A. B. Nielsen, P. Rosén, D. Fredh, A. Broström, W. Granéli, D. Hammarlund |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 2 ; Nr. 12, no. 2 (2015-01-19), S.307-322 |
| Datensatznummer |
250117774
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| Publikation (Nr.) |
 copernicus.org/bg-12-307-2015.pdf |
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| Zusammenfassung |
| Decadal-scale variations in total organic carbon (TOC) concentration in lake
water since AD 1200 in two small lakes in southern Sweden were reconstructed
based on visible–near-infrared spectroscopy (VNIRS) of their recent sediment
successions. In order to assess the impacts of local land-use changes,
regional variations in sulfur, and nitrogen deposition and climate
variations on the inferred changes in TOC concentration, the same sediment
records were subjected to multi-proxy palaeolimnological analyses. Changes
in lake-water pH were inferred from diatom analysis, whereas pollen-based
land-use reconstructions (Landscape Reconstruction Algorithm) together with
geochemical records provided information on catchment-scale environmental
changes, and comparisons were made with available records of climate and
population density. Our long-term reconstructions reveal that inferred
lake-water TOC concentrations were generally high prior to AD 1900, with
additional variability coupled mainly to changes in forest cover and
agricultural land-use intensity. The last century showed significant
changes, and unusually low TOC concentrations were inferred at AD 1930–1990,
followed by a recent increase, largely consistent with monitoring data.
Variations in sulfur emissions, with an increase in the early 1900s to a
peak around AD 1980 and a subsequent decrease, were identified as an
important driver of these dynamics at both sites, while processes related to
the introduction of modern forestry and recent increases in precipitation
and temperature may have contributed, but the effects differed between the
sites. The increase in lake-water TOC concentration from around AD 1980 may
therefore reflect a recovery process. Given that the effects of sulfur
deposition now subside and that the recovery of lake-water TOC
concentrations has reached pre-industrial levels, other forcing mechanisms
related to land management and climate change may become the main drivers of
TOC concentration changes in boreal lake waters in the future. |
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