| 1. |
- Chi Fru, Ernest, et al.
(författare)
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Cu isotopes in marine black shales record the Great Oxidation Event
- 2016
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 113:18, s. 4941-4946
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Tidskriftsartikel (refereegranskat)abstract
- The oxygenation of the atmosphere similar to 2.45-2.32 billion years ago (Ga) is one of the most significant geological events to have affected Earth's redox history. Our understanding of the timing and processes surrounding this key transition is largely dependent on the development of redox-sensitive proxies, many of which remain unexplored. Here we report a shift from negative to positive copper isotopic compositions (delta Cu-65(ERM-AE633)) in organic carbon-rich shales spanning the period 2.66-2.08 Ga. We suggest that, before 2.3 Ga, a muted oxidative supply of weathering-derived copper enriched in Cu-65, along with the preferential removal of Cu-65 by iron oxides, left seawater and marine biomass depleted in Cu-65 but enriched in Cu-63. As banded iron formation deposition waned and continentally sourced Cu became more important, biomass sampled a dissolved Cu reservoir that was progressively less fractionated relative to the continental pool. This evolution toward heavy delta Cu-65 values coincides with a shift to negative sedimentary delta Fe-56 values and increased marine sulfate after the Great Oxidation Event (GOE), and is traceable through Phanerozoic shales to modern marine settings, where marine dissolved and sedimentary delta Cu-65 values are universally positive. Our finding of an important shift in sedimentary Cu isotope compositions across the GOE provides new insights into the Precambrian marine cycling of this critical micronutrient, and demonstrates the proxy potential for sedimentary Cu isotope compositions in the study of biogeochemical cycles and oceanic redox balance in the past.
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| 2. |
- Diaz Somoano, Mercedes, et al.
(författare)
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Stable Lead Isotope Compositions In Selected Coals From Around The World And Implications For Present Day Aerosol Source Tracing
- 2009
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 43:4, s. 1078-1085
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Tidskriftsartikel (refereegranskat)abstract
- The phasing out of leaded gasoline in many countries around the world at the end of the last millennium has resulted in a complex mixture of lead sources in the atmosphere. Recent studies suggest that coal combustion has become an important source of Pb in aerosols in urban and remote areas. Here, we report lead concentration and isotopic composition for 59 coal samples representing major coal deposits worldwide in an attempt to characterize this potential source. The average concentration in these coals is 35 μg Pb g−1, with the highest values in coals from Spain and Peru and the lowest in coals from Australia and North America. The 206Pb/207Pb isotope ratios range between 1.15 and 1.24, with less radiogenic Pb in coals from Europe and Asia compared to South and North America. Comparing the Pb isotopic signatures of coals from this and previous studies with those published for Northern and Southern Hemisphere aerosols, we hypothesize that coal combustion might now be an important Pb source in China, the eastern U.S., and to some extent, in Europe but not as yet in other regions including South Africa, South America, and western U.S. This supports the notion that “old Pb pollution” from leaded gasoline reemitted into the atmosphere or long-range transport (i.e., from China to the western U.S.) is important. Comparing the isotope ratios of the coals, the age of the deposits, and Pb isotope evolution models for the major geochemical reservoirs suggests that the PbIC in coals is strongly influenced by the depositional coal forming environment.
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| 3. |
- 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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| 4. |
- He, Mao Qiang, et al.
(författare)
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Phylogenomics, divergence times and notes of orders in Basidiomycota
- 2024
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Ingår i: Fungal Diversity. - 1560-2745 .- 1878-9129. ; 126, s. 127-406
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Tidskriftsartikel (refereegranskat)abstract
- Basidiomycota is one of the major phyla in the fungal tree of life. The outline of Basidiomycota provides essential taxonomic information for researchers and workers in mycology. In this study, we present a time-framed phylogenomic tree with 487 species of Basidiomycota from 127 families, 47 orders, 14 classes and four subphyla; we update the outline of Basidiomycota based on the phylogenomic relationships and the taxonomic studies since 2019; and we provide notes for each order and discuss the history, defining characteristics, evolution, justification of orders, problems, significance, and plates. Our phylogenomic analysis suggests that the subphyla diverged in a time range of 443–490 Myr (million years), classes in a time range of 312–412 Myr, and orders in a time range of 102–361 Myr. Families diverged in a time range of 50–289 Myr, 76–224 Myr, and 62–156 Myr in Agaricomycotina, Pucciniomycotina, and Ustilaginomycotina, respectively. Based on the phylogenomic relationships and divergence times, we propose a new suborder Mycenineae in Agaricales to accommodate Mycenaceae. In the current outline of Basidiomycota, there are four subphyla, 20 classes, 77 orders, 297 families, and 2134 genera accepted. When building a robust taxonomy of Basidiomycota in the genomic era, the generation of molecular phylogenetic data has become relatively easier. Finding phenotypical characters, especially those that can be applied for identification and classification, however, has become increasingly challenging.
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| 5. |
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| 6. |
- Kylander, Malin E., et al.
(författare)
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A rapid and reliable method for Pb isotopic analysis of peat and lichens by laser ablation-quadrupole-inductively coupled plasma-mass spectrometry for biomonitoring and sample screening
- 2007
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670. ; 582:1, s. 116-124
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- An analytical protocol for rapid and reliable laser ablation-quadrupole (LA-Q)- and multi-collector (MC-) inductively coupled plasma-mass spectrometry (ICP-MS) analysis of Pb isotope ratios (207Pb/206Pb and 208Pb/206Pb) in peats and lichens is developed. This technique is applicable to source tracing atmospheric Pb deposition in biomonitoring studies and sample screening. Reference materials and environmental samples were dry ashed and pressed into pellets for introduction by laser ablation. No binder was used to reduce contamination. LA-MC-ICP-MS internal and external precisions were <1.1% and <0.3%, respectively, on both 207Pb/206Pb and 208Pb/206Pb ratios. LA-Q-ICP-MS internal precisions on 207Pb/206Pb and 208Pb/206Pb ratios were lower with values for the different sample sets <14.3% while external precisions were <2.9%. The level of external precision acquired in this study is high enough to distinguish between most modern Pb sources. LA-MC-ICP-MS measurements differed from thermal ionisation mass spectrometry (TIMS) values by 1% or less while the accuracy obtained using LA-Q-ICP-MS compared to solution MC-ICP-MS was 3.1% or better using a run bracketing (RB) mass bias correction method. Sample heterogeneity and detector switching when measuring 208Pb by Q-ICP-MS are identified as sources of reduced analytical performance.
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| 7. |
- Kylander, Malin E., et al.
(författare)
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Lead Penetration and Leaching in a Complex Temperate Soil Profile
- 2008
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Ingår i: Environmental Science and Technology. ; 42, s. 3177-3184
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Tidskriftsartikel (refereegranskat)abstract
- The documented loss of anthropogenic Pb from soil organic horizons and its migration into the mineral soil below has raised several environmental concerns, especially over the leaching of Pb into groundwater aquifers and subsequently into other environmental compartments of the ecosystem. Here, a complex colluvial soil formed over the last 10,000 years in NW Spain is studied. The objective is to evaluate the behavior of Pb in soils, including its migration rates and the potential use of complex soils as archives of atmospheric Pb pollution. To this end, Pb concentrations and Pb isotope ratios for total soil, and for acid-extractable (0.5 M HNO3) and residual fractions were determined. We show that the acid-extractable fraction is more radiogenic than the residual one in most of the soil profile and that this relationship is reversed in the surface layers (<15 cm) where pollution is greatest. Radiogenic Pb seems to have been leached out during rock weathering and pedogenesis of the soil. Comparison with a nearby peat record of atmospheric Pb deposition over the last 8 kyears demonstrates that though signals from pollution are detected in the soil record, the soil itself does not provide an accurate reconstruction of Pb deposition. On the basis of the history of soil formation the most likely Pb migration rate is estimated at approximately 0.01 cm year−1. At this migration rate Pb would be retained in the soil column for ~20 kyear. In other words, there is no evidence for the relatively rapid movement of Pb into the soil.
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| 8. |
- Kylander, Malin E., et al.
(författare)
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Rare earth element and Pb isotope variations in a 52 kyr peat core from Lynch’s Crater (NE Queensland, Australia): Proxy development and application to paleoclimate in the Southern Hemisphere
- 2007
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Ingår i: Geochemica et Cosmochimica Acta. ; 71:4, s. 942-960
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Tidskriftsartikel (refereegranskat)abstract
- Accurate prediction of future climate scenarios is contingent on our understanding of past and present climate mechanisms. This is done in part through the reconstruction of historical climate changes using proxy records from terrestrial and marine archives. Terrestrial archives covering the Holocene and late Pleistocene are limited, most acutely in the Southern Hemisphere. Here, Rare earth elements (REE) and Pb isotopes are developed as inorganic geochemical proxies of mineral dust source changes and, by extension, climate change. Using a peat core from Lynch’s Crater in NE Queensland, Australia, we present the first long-term (c. 52 kyr) terrestrial record of atmospheric REE and Pb deposition (with the exception of four wet events which represent periods of erosion from the crater itself) in the Southern Hemisphere covering both glacial and interglacial times. Based on a combination of correlation analyses, Al and Ti normalised profiles and elemental patterns, we establish REE are immobile within the peat deposit and not subject to significant post depositional diagenetic changes (important particularly for Ce). This is vital as REE can be mobile under acid and organic rich conditions like those that can occur during the development of a peat deposit. The volcanic provinces of eastern Australia have characteristic Eu anomaly signatures, which allowed their use in a novel way to detect changes in dust source to Lynch’s Crater. Between 41,095 and 52,505 BP the deposit was under the influence of dust carried by long distance transport (>1500 km) from SE Australia. From 8525 to 40,815 BP regional sources (100–1500 km) dominated the deposited signals while between 1740 and 8390 BP the dust signal was controlled by local sources (<100 km). These findings were also confirmed by Pb isotope data. Changepoint modelling refined the timing of these changes in dust source, recognizing concurrent shifts in our tracing tools ((Eu/Eu*)PAAS and 206Pb/207Pb). These changepoints were then compared to other palaeoenvironmental records (pollen, lake levels and dune building) from eastern Australia and found to be similar. Our results demonstrate that REE and Pb isotopes are effective tools for tracing past changes in atmospheric dust sources and to the study of climate change using minerotrophic peat deposits.
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| 9. |
- Kylander, malin, et al.
(författare)
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Lead Penetration and Leaching in a Complex Temperate Soil Profile
- 2008
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Ingår i: Environmental Science & Technology. ; 42:9, s. 3177-3184
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Tidskriftsartikel (refereegranskat)abstract
- The documented loss of anthropogenic Pb from soil organic horizons and its migration into the mineral soil below has raised several environmental concerns, especially over the leaching of Pb into groundwater aquifers and subsequently into other environmental compartments of the ecosystem. Here, a complex colluvial soil formed over the last 10,000 years in NW Spain is studied. The objective is to evaluate the behavior of Pb in soils, including its migration rates and the potential use of complex soils as archives of atmospheric Pb pollution. To this end, Pb concentrations and Pb isotope ratios for total soil, and for acid-extractable (0.5 M HNO3) and residual fractions were determined. We show that the acid-extractable fraction is more radiogenic than the residual one in most of the soil profile and that this relationship is reversed in the surface layers (
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| 10. |
- Kylander, Malin, 1977-, et al.
(författare)
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Natural lead isotope variations in the atmosphere
- 2010
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Ingår i: Earth and Planetary Science Letters. - : Elsevier BV. - 0012-821X .- 1385-013X. ; 290:1-2, s. 44-53
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Tidskriftsartikel (refereegranskat)abstract
- Stable lead (Pb) isotope data from pre-contamination peat sections has the potential to contribute to our understanding of earth system processes (e.g., atmospheric circulation, erosion, volcanic activity) in the past. Key questions arise however. Can the Pb isotopes archived in peat records be used for assessing aerosol dynamics on a hemispheric scale or do they mainly reflect inputs from local soils? What natural Pb sources are important and do contributions vary over time? In order to answer these questions we have synthesized all available Pb isotope data from pre-contamination peat sections in Europe, Australia, North America and South America. We specifically examine the spatial and temporal variability of the Pb isotope records and identify regionally important trends and Pb sources. A pooling of all available pre-contamination peat data generated an average natural 206Pb/207Pb background ratio of 1.21±0.05 (2σ, n=300)(206Pb/204Pb= 18.90±0.86, 207Pb/204Pb= 15.66±0.10 and 208Pb/204Pb= 38.74±0.57, n=207). The majority of the records showed limited temporal and compositional agreement, suggesting that the peat record receives mainly inputs from local (<10 km) and/or regional (10-500 km) sources. Three-isotope plots also support local and regional control and evidence a wide natural spread at some sites, particularly those located in radiogenic geological settings. A temporally synchronous isotope excursion to values between 1.16-1.18 at sites across Europe ca 4000-3000 B.C. was detected, however. While usually associated with anthropogenic sources, there are indeed natural aerosols having 206Pb/207Pb signatures as low as 1.16 as evidenced in several peat and ice core records globally. Three-isotope plots suggest that this unlikely to be a signal of mineral dust contributions, which tend to have 206Pb/207Pb ratios ≥1.19, but rather sourced to volcanic emissions. These results stress caution when using estimates of the upper continental crust to constrain natural Pb sources in, e.g., mixing equations. Considering the strong influence from local and regional sources on Pb-containing aerosols in the peat record, the assessment of aerosol dynamics at lower latitudes is likely best achieved using a compliment of archives rather than just polar ice cores, for example.
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