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- Hansson, Sophia V., et al.
(författare)
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Evaluating paleoproxies for peat decomposition and their relationship to peat geochemistry
- 2013
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Ingår i: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 23:12, s. 1666-1671
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Tidskriftsartikel (refereegranskat)abstract
- The past decade has seen a rapid increase in interest in the biogeochemical record preserved in peat, particularly as it relates to carbon dynamics and environmental change. Importantly, recent studies show that carbon dynamics, that is, organic matter decomposition, can influence the record of atmospherically derived elements such as halogens and mercury. Most commonly, bulk density, light transmission, or carbon/nitrogen (C/N) ratios are used as a proxy to qualitatively infer the degree of decomposition in peat, but do these three proxies reflect the same patterns? Furthermore, how do each of these proxies relate to other geochemical data? To address these questions, we analyzed bulk density, light transmission, and C/N ratios, as well as multielement geochemistry (wavelength-dispersive x-ray fluorescence (WD-XRF)), in three hummock cores (70 cm in length, c. 500 years) from an ombrotrophic Swedish bog. To compare the proxies, we applied principal component analysis (PCA) to identify how the proxies relate to and interact with the geochemical matrix. This was coupled with changepoint modeling to identify and compare statistically significant changes for each proxy. Our results show differences between the proxies within and between cores, indicating each responds to a different part of the decomposition process. This is supported by the PCA, where the three proxies fall on different principal components. Changepoint analysis also showed that the inferred number of changepoints and their depths vary for each proxy and core. This suggests that decomposition is not fully captured by any one of these commonly used proxies, and thus, more than one proxy should be included.
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| 2. |
- Hansson, Sophia V., 1981-
(författare)
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Incorporation and preservation of geochemical fingerprints in peat archives
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The present status of the environment, including environmental problems such as heavy metal accumulation in aquatic and terrestrial ecosystems, is in part the consequence of long-term changes. Cores from peatlands and other natural archives provide us with the potential to study aspects of the atmospheric cycling of elements, such as metal pollutants, on timescales much longer than the decade or two available to us with atmospheric deposition monitoring programs. The past decade especially has seen a rapid increase in interest in the biogeochemical record preserved in peat, particularly as it relates to environmental changes (e.g. climate and pollution). Importantly, recent studies have shown that carbon dynamics, i.e., organic matter decomposition, may influence the record of atmospherically derived elements such as halogens and mercury. Other studies have shown that under certain conditions some downward movement of atmospherically deposited elements may also occur, which adds complexity to establishing reliable chronologies as well as inherent problems of estimating accurate accumulation rates of peat and past metal deposition. Thus, we still lack a complete understanding of the basic biogeochemical processes and their effects on trace element distributions. While many studies have validated the general temporal patterns of peat records, there has been a limited critical examination of accumulation records in quantitative terms. To be certain that we extract not only a qualitative record from peat, it is important that we establish a quantitative link between the archive and the few to several decades of data that are available from contemporary monitoring and research. The main objective of this doctoral thesis was to focus on improving the link between the long-term paleorecord and the contemporary monitoring data available from biomonitoring and direct deposition observations. The main research questions have therefore been: Are peat archives an absolute or relative record? And how are geochemical signals, including dating, incorporated in the peat archive? What temporal resolution is realistic to interpret by using peat cores?
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