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Yu, C., Drake, H., Dideriksen, K., Tillberg, M., Song, Z., Mørup, S. & Åström, M. E. (2020). A Combined X-ray Absorption and Mössbauer Spectroscopy Study on Fe Valence and Secondary Mineralogy in Granitoid Fracture Networks: Implications for Geological Disposal of Spent Nuclear Fuels [Letter to the editor]. Environmental Science and Technology, 54(5), 2832-2842
Åpne denne publikasjonen i ny fane eller vindu >>A Combined X-ray Absorption and Mössbauer Spectroscopy Study on Fe Valence and Secondary Mineralogy in Granitoid Fracture Networks: Implications for Geological Disposal of Spent Nuclear Fuels
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2020 (engelsk)Inngår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 54, nr 5, s. 2832-2842Artikkel i tidsskrift, Letter (Fagfellevurdert) Published
Abstract [en]

Underground repository in crystalline bedrock is a widely accepted solution for long-term disposal of spent nuclear fuels. During future deglaciations, meltwater will intrude via bedrock fractures to the depths of future repositories where O2 left in the meltwater could corrode metal canisters and enhance the migration of redox-sensitive radionuclides. Since glacial meltwater is poor in reduced phases, the quantity and (bio)accessibility of minerogenic Fe(II) in bedrock fractures determine to what extent O2 in future meltwater can be consumed. Here, we determined Fe valence and mineralogy in secondary mineral assemblages sampled throughout the upper kilometer of fractured crystalline bedrock at two sites on the Baltic Shield, using X-ray absorption and Mössbauer spectroscopic techniques that were found to deliver matching results. The data point to extensive O2-consuming capacity of the bedrock fractures, because Fe(II)-rich phyllosilicates were abundant and secondary pyrite was dispersed deep into the bedrock with no overall increase in Fe(II) concentrations and Fe(II)/Fe(III) proportions with depth. The results imply that repeated Pleistocene deglaciations did not cause a measurable decrease in the Fe(II) pool. In surficial fractures, largely opened during glacial unloading, ferrihydrite and illite have formed abundantly via oxidative transformation of Fe(II)-rich phyllosilicates and recently exposed primary biotite/hornblende.

sted, utgiver, år, opplag, sider
American Chemical Society (ACS), 2020
HSV kategori
Forskningsprogram
Naturvetenskap, Miljövetenskap
Identifikatorer
urn:nbn:se:lnu:diva-92512 (URN)10.1021/acs.est.9b07064 (DOI)000518235100029 ()
Tilgjengelig fra: 2020-03-03 Laget: 2020-03-03 Sist oppdatert: 2020-03-26bibliografisk kontrollert
Shilei, Y., Qian, H., Wang, H., Van Zwieten, L., Yu, C., Liu, T., . . . Song, Z. (2020). A review of carbon isotopes of phytoliths: implications for phytolith-occluded carbon sources [Letter to the editor]. Journal of Soils and Sediments, 20(4), 1811-1823
Åpne denne publikasjonen i ny fane eller vindu >>A review of carbon isotopes of phytoliths: implications for phytolith-occluded carbon sources
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2020 (engelsk)Inngår i: Journal of Soils and Sediments, ISSN 1439-0108, E-ISSN 1614-7480, Vol. 20, nr 4, s. 1811-1823Artikkel i tidsskrift, Letter (Fagfellevurdert) Published
Abstract [en]

Purpose Phytolith-occluded carbon (PhytOC) is mainly derived from the products of photosynthesis, which can be preserved in soils and sediments for hundreds-to-thousands of years due to the resilient nature of the amorphous phytolith silica. Therefore, stable and radioactive carbon (C) isotopes of phytoliths can be effectively utilized in paleoecological and archeological research. However, there still exists debate about the applicability of C isotopes of phytoliths, as a “two-pool” hypothesis to characterize PhytOC sources has been proposed, whereby a component of the PhytOC is derived from soil organic matter (SOM) absorbed through plant roots. Therefore, it is necessary to review this topic to better understand the source of PhytOC. Materials and method We introduce the stable and radioactive C isotopic compositions of PhytOC, present the impacts of different extraction methods on the study of PhytOC, and discuss the implications of these factors for determining the sources of PhytOC. Results and discussion Based on this review, we suggest that organic matter synthesized by photosynthesis is the main source of PhytOC. However, it is important to make clear whether and how SOM-derived C present in phytoliths influence the controversial “too-old” skew and isotopic fractionation. Conclusions Though the two-pool hypothesis has been proved by many researches, the carbon isotopes of phytoliths still have potential in paleoecology and archeology, because the main source is photosynthesis and many previous studies put forward the availability of these parameters. This review also shows that phytolith C isotopes may vary with different organic C compounds within phytoliths, which needs further study at the molecular scale. Different phytolith extraction methods can influence 14C dating results.

sted, utgiver, år, opplag, sider
Springer, 2020
Emneord
C3 and C4 plants, δ13C, 14C dating, Phytolith extraction method
HSV kategori
Forskningsprogram
Naturvetenskap, Miljövetenskap
Identifikatorer
urn:nbn:se:lnu:diva-93196 (URN)10.1007/s11368-019-02548-4 (DOI)000520712100002 ()
Tilgjengelig fra: 2020-03-31 Laget: 2020-03-31 Sist oppdatert: 2020-04-28bibliografisk kontrollert
Yang, X., Song, Z., Yu, C. & Ding, F. (2020). Quantification of different silicon fractions in broadleaf and conifer forests of northern China and consequent implications for biogeochemical Si cycling. Geoderma, 361, 1-10, Article ID 114036.
Åpne denne publikasjonen i ny fane eller vindu >>Quantification of different silicon fractions in broadleaf and conifer forests of northern China and consequent implications for biogeochemical Si cycling
2020 (engelsk)Inngår i: Geoderma, ISSN 0016-7061, E-ISSN 1872-6259, Vol. 361, s. 1-10, artikkel-id 114036Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The terrestrial biogeochemical silicon (Si) cycle significantly contributes to maintaining the functions and sustainability of terrestrial ecosystems. Over the short term, the biogeochemical Si cycle can be strongly influenced by dissolved Si, organic bound Si, Si adsorbed to pedogenic oxides/hydroxides, and biogenic and pedogenic amorphous Si. However, quantitative studies about these relatively soluble Si fractions are rare. In this study, we quantified different Si fractions in the 0–10 cm, 10–20 cm, 20–30 cm, 30–40 cm and 40–50 cm soil layers of broadleaf forests (Betula forest and Quercus forest) and conifer forests (Larix forest and Pinus forest) in northern China using a sequential chemical extraction scheme optimized for these Si fractions. The results showed that the total Si (Sit) in the soil layers consisted of 97.7–98.5% crystalline Si (Sicry) and 1.5–2.3% non-crystalline Si (Sinoncry) fractions. Within the Sinoncry fraction, the proportions of dissolved Si (Sidis), organic matter bound Si (Siorg), pedogenic oxides/hydroxides chemisorbed Si (Sisorb), and amorphous Si (Siamor) were 3.4–6.7%, 5.5–8.9%, 6.3–8.5%, and 77.7–84.8%, respectively. Although the Sidis fraction was the least abundant component, it is at the center of the interconversion processes among the different Sinoncry fractions. The Siamor fraction was the largest component of Sinoncry and was composed of 37.7–71.9% biogenic amorphous Si (Sibio-amor) and 28.1–62.3% pedogenic amorphous Si (Siped-amor). Our study indicated that i) Siped-amor fraction is more easily influenced by soil pH comparing to Sibio-amor fraction; ii) the Sibio-amor fraction contributes more to the biogeochemical Si cycle in broadleaf forests, whereas the Siped-amorfraction contributes more in conifer forests; and iii) soil pH, soil organic matter, and plant community differences can influence the vertical distribution of the different Sinoncry fractions and thus affect the multiple transformation processes among these Si fractions in studied forests.

sted, utgiver, år, opplag, sider
Elsevier, 2020
Emneord
Sequential chemical extraction, Relatively soluble Si fractions, Si bioavailability, Biogenic amorphous Si, Pedogenic amorphous Si, Forest soils
HSV kategori
Forskningsprogram
Naturvetenskap, Miljövetenskap
Identifikatorer
urn:nbn:se:lnu:diva-90947 (URN)10.1016/j.geoderma.2019.114036 (DOI)000510804700034 ()
Tilgjengelig fra: 2020-01-16 Laget: 2020-01-16 Sist oppdatert: 2020-03-12bibliografisk kontrollert
Xia, S., Song, Z., Van Zwieten, L., Guo, L., Yu, C., Hartley, I. P. & Wang, H. (2020). Silicon accumulation controls carbon cycle in wetlands through modifying nutrients stoichiometry and lignin synthesis of Phragmites australis. Environmental and Experimental Botany, 175, 1-11, Article ID 104058.
Åpne denne publikasjonen i ny fane eller vindu >>Silicon accumulation controls carbon cycle in wetlands through modifying nutrients stoichiometry and lignin synthesis of Phragmites australis
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2020 (engelsk)Inngår i: Environmental and Experimental Botany, ISSN 0098-8472, E-ISSN 1873-7307, Vol. 175, s. 1-11, artikkel-id 104058Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Silicon (Si) is one of the most abundant elements in the Earth’s crust but its role in governing the biogeochemicalcycling of other elements remains poor understood. There is a paucity of information on the role of Si in wetlandplants, and how this may alter wetland C production and storage. Therefore, this study investigated Si distribution,nutrient stoichiometry and lignin abundance in Phragmites australis from a wetland system in China tobetter understand the biogeochemical cycling and C storage. Our data show that Si content (ranging between0.202% to 6.614%) of Phragmites australis is negatively correlated with C concentration (38.150%–47.220%).Furthermore, Si content was negatively antagonistically related to the concentration of lignin-derived phenols inthe stem (66.763–120.670 mg g-1 C) and sheath (65.400–114.118 mg g-1 C), but only a weak relationship wasobserved in the leaf tissue (36.439–55.905 mg g-1 C), which is relevant to the photosynthesis or stabilizationfunction of the plant tissues. These results support the notion that biogenic Si (BSi) can substitute lignin as astructural component, due to their similar eco-physiological functions, reduces costs associated with ligninbiosynthesis. The accumulation of BSi increased total biomass C storage and nutrient accumulation due togreater productivity of Phragmites australis. On the other hand, BSi regulated litter composition and quality (e.g.,nutrient stoichiometry and lignin) that provide a possibility for the factors affecting litter decomposition. Thuscompeting processes (i.e., biomass quantity vs quality) can be influenced by Si cycling in wetlands.

sted, utgiver, år, opplag, sider
Elsevier, 2020
Emneord
Blue Carbon, biogenic silica, lignin, Phragmites australis, litter composition and quality, wetland
HSV kategori
Forskningsprogram
Naturvetenskap, Miljövetenskap; Naturvetenskap, Miljövetenskap
Identifikatorer
urn:nbn:se:lnu:diva-93711 (URN)10.1016/j.envexpbot.2020.104058 (DOI)
Tilgjengelig fra: 2020-04-24 Laget: 2020-04-24 Sist oppdatert: 2020-05-05bibliografisk kontrollert
Zhang, X., Song, Z., Hao, Q., Yu, C., Liu, H., Chen, C., . . . Wang, H. (2020). Storage of soil phytoliths and phytolith-occluded carbon along aprecipitation gradient in grasslands of northern China [Letter to the editor]. Geoderma, 364, 1-9, Article ID 114200.
Åpne denne publikasjonen i ny fane eller vindu >>Storage of soil phytoliths and phytolith-occluded carbon along aprecipitation gradient in grasslands of northern China
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2020 (engelsk)Inngår i: Geoderma, ISSN 0016-7061, E-ISSN 1872-6259, Vol. 364, s. 1-9, artikkel-id 114200Artikkel i tidsskrift, Letter (Fagfellevurdert) Published
Abstract [en]

Climatic factors including mean annual precipitation (MAP) significantly influence the carbon (C) cycle interrestrial ecosystems and Earth overall. Phytolith-occluded carbon (PhytOC) is an important C sequestrationmechanism and as such plays a vital role in global long-term C sequestration. Understanding the spatialvariability in the storage of soil phytoliths and PhytOC and its relationship with climate is critical for evaluatingthe impact of global climate change on terrestrial ecosystem functions. However, little is known about theresponses of soil phytoliths and PhytOC to MAP in grassland ecosystems. This study sampled soil from 24natural, semi-arid steppe sites along a 2,500 km transect with a precipitation gradient of 243–481 mm yr−1 innorthern China. We investigated the influence of precipitation on the spatial distributions of soil phytoliths andPhytOC storage. Storage of soil phytoliths in bulk soil (0–100 cm depth) ranged from 21.3 ± 0.4 to88.4 ± 20.3 t ha−1 along the precipitation gradient. Amounts of soil phytoliths and PhytOC storage weresignificantly and positively correlated with MAP. Multiple regression analysis revealed that phytolith storage inbulk soil was best predicted by MAP (R = 0.5) and soil organic carbon (SOC, R = 0.4), with these two variablesaccounting for about 58% of the total variation observed. Considering the forecasted increase in MAP in theInner Mongolian steppe due to climate change, and the strong influence of MAP on the annual net primaryproductivity (ANPP) and related soil PhytOC input from litter decomposition in this region, we expect thatecosystem primary productivity will increase from deserts to meadow steppe and thereby promote soil PhytOCstorage. These findings have important implications for understanding the dynamics of soil phytoliths, andpredicting the impacts of global climate change on ecosystem functions and management practices in the EastAsian steppe ecosystems.

sted, utgiver, år, opplag, sider
Elsevier, 2020
Emneord
Soil phytolith, Mean annual precipitation, Stability, Mongolian Plateau
HSV kategori
Forskningsprogram
Naturvetenskap, Miljövetenskap
Identifikatorer
urn:nbn:se:lnu:diva-91381 (URN)10.1016/j.geoderma.2020.114200 (DOI)000517855200012 ()
Tilgjengelig fra: 2020-01-28 Laget: 2020-01-28 Sist oppdatert: 2020-03-19bibliografisk kontrollert
Christel, S., Yu, C., Wu, X., Josefsson, S., Lillhonga, T., Högfors-Rönnholm, E., . . . Dopson, M. (2019). Comparison of Boreal Acid Sulfate Soil Microbial Communities in Oxidative and Reductive Environments [Letter to the editor]. Research in Microbiology, 170(6-7), 288-295
Åpne denne publikasjonen i ny fane eller vindu >>Comparison of Boreal Acid Sulfate Soil Microbial Communities in Oxidative and Reductive Environments
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2019 (engelsk)Inngår i: Research in Microbiology, ISSN 0923-2508, E-ISSN 1769-7123, Vol. 170, nr 6-7, s. 288-295Artikkel i tidsskrift, Letter (Fagfellevurdert) Published
Abstract [en]

Due to land uplift after the last ice age, previously stable Baltic Sea sulfidic sediments are becoming dry land. When these sediments are drained, the sulfide minerals are exposed to air and can release large amounts of metals and acid into the environment. This can cause severe ecological damage such as fish kills in rivers feeding the northern Baltic Sea. In this study, five sites were investigated for the occurrence of acid sulfate soils and their geochemistry and microbiology was identified. The pH and soil chemistry identified three of the areas as having classical acid sulfate soil characteristics and culture independent identification of 16S rRNA genes identified populations related to acidophilic bacteria capable of catalyzing sulfidic mineral dissolution, including species likely adapted to low temperature. These results were compared to an acid sulfate soil area that had been flooded for ten years and showed that the previously oxidized sulfidic materials had an increased pH compared to the unremediated oxidizied layers. In addition, the microbiology of the flooded soil had changed such that alkalinity producing ferric and sulfate reducing reactions had likely occurred. This suggested that flooding of acid sulfate soils mitigates their environmental impact.

sted, utgiver, år, opplag, sider
Elsevier, 2019
Emneord
sulfide mineral; metal; sulfur; 16S rRNA gene; mitigation; wetland
HSV kategori
Forskningsprogram
Naturvetenskap, Miljövetenskap
Identifikatorer
urn:nbn:se:lnu:diva-77664 (URN)10.1016/j.resmic.2019.06.002 (DOI)000491121700006 ()
Tilgjengelig fra: 2018-09-10 Laget: 2018-09-10 Sist oppdatert: 2019-10-31bibliografisk kontrollert
Yu, C., Berger, T., Drake, H., Song, Z., Peltola, P. & Åström, M. E. (2019). Geochemical controls on dispersion of U and Th in Quaternary deposits, stream water, and aquatic plants in an area with a granite pluton. Science of the Total Environment, 663, 16-28
Åpne denne publikasjonen i ny fane eller vindu >>Geochemical controls on dispersion of U and Th in Quaternary deposits, stream water, and aquatic plants in an area with a granite pluton
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2019 (engelsk)Inngår i: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 663, s. 16-28Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The weathering of U and/or Th rich granite plutons, which occurs worldwide, may serve as a potentially important, but as yet poorly defined source for U and Th in (sub-)surface environments. Here, we assessed the impact of an outcrop of such granite (5 km in diameter) and its erosional products on the distribution of U and Th in four nemo-boreal catchments. The results showed that (i) the pluton was enriched in both U and Th; and (ii) secondary U and Th phases were accumulated by peat/gyttja and in other Quaternary deposits with high contents of organic matter. Movement of the ice sheet during the latest glaciation led to dispersal of U- and Th-rich materials eroded from the pluton, resulting in a progressive increase in dissolved U and Th concentrations, as well as U concentrations in aquatic plants with increasing proximity to the pluton. The accumulation of U in the aquatic plants growing upon the pluton (100–365 mg kg−1, dry ash weight) shows that this rock represents a long-term risk for adjacent ecosystems. Dissolved pools of U and Th were correlated with those of dissolved organic matter (DOM) and were predicted to largely occur as organic complexes. This demonstrates the importance of DOM in the transport of U and Th in the catchments. Large fractions of Ca2UO2(CO3)30(aq) were modeled to occur in the stream with highest pH and alkalinity and thus, explain the strongly elevated U concentrations and fluxes in this particular stream. In future climate scenarios, boreal catchments will experience intensified runoff and warmer temperature that favor the production of hydrologically accessible DOM and alkalinity. Therefore, the results obtained from this study have implications for predicting the distribution and transport of Th and U in boreal catchments, especially those associated with U and/or Th rich granite plutons.

sted, utgiver, år, opplag, sider
Elsevier, 2019
Emneord
Uranium, Thorium, Nemo-boreal catchments, Climate change, Weathering
HSV kategori
Forskningsprogram
Naturvetenskap, Miljövetenskap; Naturvetenskap, Miljövetenskap
Identifikatorer
urn:nbn:se:lnu:diva-80032 (URN)10.1016/j.scitotenv.2019.01.293 (DOI)000459858500002 ()30708213 (PubMedID)2-s2.0-85060730596 (Scopus ID)
Tilgjengelig fra: 2019-01-30 Laget: 2019-01-30 Sist oppdatert: 2020-05-08bibliografisk kontrollert
Yang, S., Hao, Q., Liu, H., Xiaodong, Z., Yu, C., Yang, X., . . . Song, Z. (2019). Impact of grassland degradation on the distribution and bioavailability of soil silicon: Implications for the Si cycle in grasslands [Letter to the editor]. Science of the Total Environment, 657, 811-818
Åpne denne publikasjonen i ny fane eller vindu >>Impact of grassland degradation on the distribution and bioavailability of soil silicon: Implications for the Si cycle in grasslands
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2019 (engelsk)Inngår i: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 657, s. 811-818Artikkel i tidsskrift, Letter (Fagfellevurdert) Published
Abstract [en]

Grassland ecosystems play an important role in the global terrestrial silicon (Si) cycle, and Si is a beneficial elementand structural constituent for the growth of grasses. In previous decades, grasslands have been degradedto different degrees because of the drying climate and intense human disturbance. However, the impact of grasslanddegradation on the distribution and bioavailability of soil Si is largely unknown. Here, we investigated vegetationand soil conditions of 30 sites to characterize different degrees of degradation for grasslands in the agropastoralecotone of northern China. We then explored the impact of grassland degradation on the distributionand bioavailability of soil Si, including total Si and four forms of noncrystalline Si in three horizons (0–10,10–20 and 20–40 cm) of different soil profiles. The concentrations of noncrystalline Si in soil profiles significantlydecreased with increasing degrees of degradation, being 7.35 ± 0.88 mg g−1, 5.36 ± 0.39 mg g−1, 3.81 ±0.37 mg g−1 and 3.60±0.26 mg g−1 in non-degraded, lightly degraded, moderately degraded and seriously degradedgrasslands, respectively. Moreover, the storage of noncrystalline Si decreased from higher than 40 t ha−1to lower than 23 t ha−1. The corresponding bioavailability of soil Si also generally decreased with grassland degradation.These processes may not only affect the Si pools and fluxes in soils but also influence the Si uptake in 

plants. We suggest that grassland degradation can significantly affect the global grassland Si cycle. Grasslandmanagement methods such as fertilizing and avoiding overgrazing can potentially double the content and storageof noncrystalline Si in soils, thereby enhancing the soil Si bioavailability by N17%.

sted, utgiver, år, opplag, sider
Elsevier, 2019
Emneord
Silicon cycle, Bioavailability, Grassland degradation, Agro-pastoral ecotone, Northern China
HSV kategori
Forskningsprogram
Naturvetenskap, Miljövetenskap; Naturvetenskap
Identifikatorer
urn:nbn:se:lnu:diva-79201 (URN)10.1016/j.scitotenv.2018.12.101 (DOI)000455903400079 ()30677946 (PubMedID)2-s2.0-85058244692 (Scopus ID)
Tilgjengelig fra: 2018-12-13 Laget: 2018-12-13 Sist oppdatert: 2019-08-29bibliografisk kontrollert
Yu, C., Drake, H., Lopez-Fernandez, M., Whitehouse, M., Dopson, M. & Åström, M. E. (2019). Micro-scale isotopic variability of low-temperature pyrite in fractured crystalline bedrock ― A large Fe isotope fractionation between Fe(II)aq/pyrite and absence of Fe-S isotope co-variation. Chemical Geology, 522, 192-207
Åpne denne publikasjonen i ny fane eller vindu >>Micro-scale isotopic variability of low-temperature pyrite in fractured crystalline bedrock ― A large Fe isotope fractionation between Fe(II)aq/pyrite and absence of Fe-S isotope co-variation
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2019 (engelsk)Inngår i: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 522, s. 192-207Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

This study assessed Fe-isotope ratio (56Fe/54Fe, expressed as δ56Fe relative to the IRMM-014 standard) variability and controls in pyrite that has among the largest reported S-isotope variability (maximum δ34S: 140‰). The pyrite occurs as fine-grained secondary crystals in fractures throughout the upper kilometer of granitoids of the Baltic Shield, and was analyzed here for δ56Fe by in situ secondary ion mass spectrometry (SIMS). Part of these pyrite crystals were picked from borehole instrumentation at depths of >400 m below sea level (m.b.s.l.), and thus are modern (known to have formed within 17 years) and can be compared with the δ56Fe of the source dissolved ferrous iron. The δ56Fe values of the modern pyrite crystals (−1.81‰ to +2.29‰) varied to a much greater extent than those of the groundwaters from which they formed (−0.48‰ to +0.13‰), providing strong field evidence for a large Fe isotope fractionation during the conversion of Fe(II)aq to FeS and ultimately to pyrite. Enrichment of 56Fe in pyrite relative to the groundwater was explained by equilibrium Fe(II)aq-FeS isotope fractionation, whereas depletion of 56Fe in pyrite relative to the groundwater was mainly the result of sulfidization of magnetite and kinetic isotopic fractionation during partial transformation of microsized FeS to pyrite. In many pyrite crystals, there is an increase in δ34S from crystal center to rim reflecting Rayleigh distillation processes (reservoir effects) caused by the development of closed-system conditions in the micro-environment near the growing crystals. A corresponding center-to-rim feature was not observed for the δ56Fe values. It is therefore unlikely that the groundwater near the growing pyrite crystals became progressively enriched in the heavy Fe isotope, in contrast to what has been found for the sulfur in sulfate. Other pyrite crystals formed following bacterial sulfate reduction in the time period of mid-Mesozoicum to Quaternary, had an almost identical Fe-isotope variability (total range: −1.50‰ to +2.76‰), frequency-distribution pattern, and relationship with δ34S as the recent pyrite formed on the borehole instrumentation. These features suggest that fundamental processes are operating and governing the Fe-isotope composition of pyrite crystals formed in fractured crystalline bedrock over large time scales.

sted, utgiver, år, opplag, sider
Elsevier, 2019
Emneord
Pyrite, Iron isotopes, Equilibrium Fe-isotope fractionation, Magnetite sulfidization, Partial pyritization, Fractured crystalline bedrock
HSV kategori
Forskningsprogram
Naturvetenskap, Miljövetenskap
Identifikatorer
urn:nbn:se:lnu:diva-84618 (URN)10.1016/j.chemgeo.2019.05.026 (DOI)000480330600016 ()2-s2.0-85066994013 (Scopus ID)
Forskningsfinansiär
Swedish Research Council, 2017-05186Swedish Research Council, 2014-4398Swedish Research Council Formas, 2017-00766
Tilgjengelig fra: 2019-06-05 Laget: 2019-06-05 Sist oppdatert: 2019-08-29bibliografisk kontrollert
Yu, C., Boily, J.-F., Shchukarev, A., Drake, H., Song, Z., Hogmalm, K. J. & Åström, M. E. (2018). A cryogenic XPS study of Ce fixation on nanosized manganite and vernadite: Interfacial reactions and effects of fulvic acid complexation. Chemical Geology, 483, 304-311
Åpne denne publikasjonen i ny fane eller vindu >>A cryogenic XPS study of Ce fixation on nanosized manganite and vernadite: Interfacial reactions and effects of fulvic acid complexation
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2018 (engelsk)Inngår i: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 483, s. 304-311Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

This study investigated interfacial reactions between aqueous Ce(III) and two synthetic nanosized Mn (hydr-) oxides (manganite: γ-MnOOH, and vernadite: δ-MnO2) in the absence and presence of Nordic Lake fulvic acid (NLFA) at circumneutral pH by batch experiments and cryogenic X-ray photoelectron spectroscopy (XPS). The surfaces of manganite and vernadite were negatively charged (XPS-derived loadings of (Na+K)/Cl > 1) and loaded with 0.42–4.33 Ce ions nm−2. Manganite stabilized Ce-oxidation states almost identical to those for vernadite (approximately 75% Ce(IV) and 25% Ce(III)), providing the first experimental evidence that also a Mn (III) phase (manganite) can act as an important scavenger for Ce(IV) and thus, contribute to the decoupling of Ce from its neighboring rare earth elements and the development of Ce anomaly. In contrast, when exposed to Ce (III)-NLFA complexes, the oxidation of Ce by these two Mn (hydr-)oxides was strongly suppressed, suggesting that the formation of Ce(III) complexes with fulvic acid can stabilize Ce(III) even in the presence of oxidative Mn oxide surfaces. The experiments also showed that Ce(III) complexed with excess NLFA was nearly completely removed, pointing to a strong preferential sorption of Ce(III)-complexed NLFA over free NLFA. This finding suggests that the Ce(III)-NLFA complexes were most likely sorbed by their cation side, i.e. Ce(III) bridging between oxide groups on the Mn (hydr-)oxides and negatively-charged functional groups in NLFA. Hence, Ce(III) was in direct contact with the oxidative manganite and vernadite but despite that not oxidized. An implication is that in organic-rich environments there may be an absence of Ce(IV) and Ce anomaly despite otherwise favorable conditions for Ce(III) oxidation.

sted, utgiver, år, opplag, sider
Elsevier, 2018
Emneord
Cryogenic XPS, Manganite, Vernadite, Oxidative scavenging, Ce anomaly
HSV kategori
Forskningsprogram
Naturvetenskap
Identifikatorer
urn:nbn:se:lnu:diva-72684 (URN)10.1016/j.chemgeo.2018.02.033 (DOI)000429492300027 ()2-s2.0-85042905870 (Scopus ID)
Tilgjengelig fra: 2018-04-13 Laget: 2018-04-13 Sist oppdatert: 2019-08-29bibliografisk kontrollert
Organisasjoner
Identifikatorer
ORCID-id: ORCID iD iconorcid.org/0000-0002-0635-3718