umu.sePublications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Incorporation and preservation of geochemical fingerprints in peat archives
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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?

Place, publisher, year, edition, pages
Umeå: Umeå Universitet , 2013. , 36 p.
Keyword [en]
Peat, Beryllium, bulk density, C/N-ratio, decomposition, deposition, downwash, elemental mobility, geochemistry, humification, lead, light transmission, mercury, peat accumulation, precipitation
National Category
Environmental Sciences
Research subject
biology, Environmental Science
Identifiers
URN: urn:nbn:se:umu:diva-84161ISBN: 978-91-7459-779-0 (print)OAI: oai:DiVA.org:umu-84161DiVA: diva2:679766
Public defence
2014-01-24, KB3A9, KBC, Umeå University, Umeå, 10:00 (English)
Opponent
Supervisors
Available from: 2013-12-17 Created: 2013-12-16 Last updated: 2013-12-17Bibliographically approved
List of papers
1. Evaluating paleoproxies for peat decomposition and their relationship to peat geochemistry
Open this publication in new window or tab >>Evaluating paleoproxies for peat decomposition and their relationship to peat geochemistry
Show others...
2013 (English)In: The Holocene, ISSN 0959-6836, E-ISSN 1477-0911, Vol. 23, no 12, 1666-1667 p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Sage Publications, 2013
Keyword
bulk density, C, N ratio, decomposition, humification, light transmission, peat
National Category
Geochemistry
Identifiers
urn:nbn:se:umu:diva-84156 (URN)10.1177/0959683613508160 (DOI)
Funder
Swedish Research Council
Available from: 2013-12-16 Created: 2013-12-16 Last updated: 2017-12-06Bibliographically approved
2. Beryllium-7 as a natural tracer for short-term downwash in peat
Open this publication in new window or tab >>Beryllium-7 as a natural tracer for short-term downwash in peat
2014 (English)In: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 119, no 1-3, 329-339 p.Article in journal (Refereed) Published
Abstract [en]

Several factors can affect the integrity of natural archives such as peat records, e.g., decomposition and nutrient cycling, and it has also been hypothesized that some rapid downward transport of atmospherically derived elements may occur. We test this hypothesis by analyzing the short-lived, natural tracer beryllium-7 (tA1/2A = 53.4 days) in five cores from two peatlands. In triplicate hummock cores from a raised bog in southern Sweden, Be-7 could be measured to 20, 18 and 8 cm depth, and in a nutrient-poor mire in northern Sweden to a depth of 16 cm in a Sphagnum lawn core, but only 4 cm in the dominant, more-decomposed fen peat, indicating some spatial variability both within and between sites. Total Be-7 inventories were 320-450 Bq m(-2) in the bog, and 150 Bq m(-2) (lawn) and 240 Bq m(-2) (fen peat) in the mire. 25-79 % of the total inventory of Be-7 was located in the upper 2-cm layer. To further test downwashing, in the laboratory we applied a CuBr-solution to two cores and a Cu-solution to one core taken from the mire Sphagnum lawn, all with low water table conditions. About 50 % of the added Cu and similar to 35 % of the added Br were retained in the surface (2 cm) layer; 1-3 % of the Cu was found at 8-12 cm depth and similar to 1 % of the Br was measured in the lowest level (20-22 cm). Based on our novel approach using Be-7 and experimental work we show that short-term downwashing can occur in peatlands and we suggest the depth of this will depend on the properties of the peat, e.g., bulk density and decomposition, as well as hydrology.

Keyword
Beryllium, Downwash, Geochemistry, Peat
National Category
Geochemistry
Identifiers
urn:nbn:se:umu:diva-84158 (URN)10.1007/s10533-014-9969-y (DOI)000336028400021 ()
Available from: 2013-12-16 Created: 2013-12-16 Last updated: 2017-12-06Bibliographically approved
3. Testing the downwash of atmospherically deposited metals in peat and the influence of rainfall intensity
Open this publication in new window or tab >>Testing the downwash of atmospherically deposited metals in peat and the influence of rainfall intensity
(English)Article in journal (Refereed) Submitted
National Category
Geochemistry
Identifiers
urn:nbn:se:umu:diva-84159 (URN)
Available from: 2013-12-16 Created: 2013-12-16 Last updated: 2013-12-16Bibliographically approved
4. Incorporation of radiometric tracers in peat and implications for estimating accumulation rates
Open this publication in new window or tab >>Incorporation of radiometric tracers in peat and implications for estimating accumulation rates
2014 (English)In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 493, 170-177 p.Article in journal (Refereed) Published
Abstract [en]

Accurate dating of peat accumulation is essential for quantitatively reconstructing past changes in atmospheric metal deposition and carbon burial. By analyzing fallout radionuclides Pb-210, Cs-137, Am-241, and Be-7, and total Pb and Hg in 5 cores from two Swedish peatlands we addressed the consequence of estimating accumulation rates due to downwashing of atmospherically supplied elements within peat. The detection of Be-7 down to 18-20 cm for some cores, and the broad vertical distribution of Am-241 without a well-defined peak, suggest some downward transport by percolating rainwater and smearing of atmospherically deposited elements in the uppermost peat layers. Application of the CRS age-depth model leads to unrealistic peat mass accumulation rates (400-600 g m(-2) yr(-1)), and inaccurate estimates of past Pb and Hg deposition rates and trends, based on comparisons to deposition monitoring data (forest moss biomonitoring and wet deposition). After applying a newly proposed IP-CRS model that assumes a potential downward transport of Pb-210 through the uppermost peat layers, recent peat accumulation rates (200-300 g m(-2) yr(-1)) comparable to published values were obtained. Furthermore, the rates and temporal trends in Pb and Hg accumulation correspond more closely to monitoring data, although some off-set is still evident. We suggest that downwashing can be successfully traced using Be-7, and if this information is incorporated into age-depth models, better calibration of peat records with monitoring data and better quantitative estimates of peat accumulation and past deposition are possible, although more work is needed to characterize how downwashing may vary between seasons or years.

Keyword
Beryllium, Downwash, Lead, Mercury, Peat accumulation
National Category
Geochemistry
Identifiers
urn:nbn:se:umu:diva-84160 (URN)10.1016/j.scitotenv.2014.05.088 (DOI)2014 ()24946030 (PubMedID)493 (Scopus ID)
Available from: 2013-12-16 Created: 2013-12-16 Last updated: 2017-12-06Bibliographically approved

Open Access in DiVA

Kappan(1021 kB)815 downloads
File information
File name FULLTEXT01.pdfFile size 1021 kBChecksum SHA-512
bbe4762857228003c28112e4c1f239635e7f2e39120340d80d652aae26161723e6b2824ba364f85e797e107ac6deb1eca95768a2961d3749f585e9531f550e80
Type fulltextMimetype application/pdf
Spikblad(95 kB)7 downloads
File information
File name FULLTEXT02.pdfFile size 95 kBChecksum SHA-512
2000acb0132471953c80fd3ecfdb5d8097b367094964b3b3fb2c1b9eb93f15930630e856a9d1d3137c606ad92177ab512e6f135ced6b286548525125abe49ab2
Type spikbladMimetype application/pdf
Omslag(2451 kB)6 downloads
File information
File name FULLTEXT03.pdfFile size 2451 kBChecksum SHA-512
24eabc4e1616d3ca846bfd1775aa63716ff3a2992605c92c166cc1d51c3a3d3382be903650ece4e55fc4afd7609eb678b0a88fa5c202eff765e232f61d034b32
Type coverMimetype application/pdf

Authority records BETA

Hansson, Sophia V.

Search in DiVA

By author/editor
Hansson, Sophia V.
By organisation
Department of Ecology and Environmental Sciences
Environmental Sciences

Search outside of DiVA

GoogleGoogle Scholar
Total: 828 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 294 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf