DOI: 10.1016/j.earscirev.2018.12.012
论文题名: Iron cycling and isotope fractionation in terrestrial ecosystems
作者: Wu B. ; Amelung W. ; Xing Y. ; Bol R. ; Berns A.E.
刊名: Earth Science Reviews
ISSN: 00128252
出版年: 2019
卷: 190 起始页码: 323
结束页码: 352
语种: 英语
中文关键词: Freshwater
; Iron cycle
; Iron isotope fractionation
; Plant
; Soil
; Terrestrial ecosystem
英文关键词: biogeochemical cycle
; biogeochemistry
; freshwater
; iron
; isotopic composition
; isotopic fractionation
; silicate mineral
; terrestrial ecosystem
英文摘要: The cycling of iron (Fe) is often closely linked with that of carbon, nitrogen, phosphorus and manganese. Therefore, alterations in the Fe cycle may be indicative of concurrent overall changes in the biogeochemistry of terrestrial and aquatic ecosystems. Biogeochemical processes taking part in the Fe cycle frequently fractionate stable Fe isotopes, leaving soil, plant and other compartments of the ecosystems with varied Fe isotopic signatures. In this work, we reviewed the Fe isotope fractionation processes that have been reported so far for terrestrial ecosystems. While parent materials vary in Fe isotope compositions, pedogenic processes can further fractionate Fe isotope signatures, resulting in soil profiles with δ 56 Fe values (relative to isotope standard IRMM-014) from −0.52 to +0.72‰. Different soil Fe pools, as a result of cycling processes, show an even broader range of δ 56 Fe values, with secondary Fe oxides being isotopically the lightest, and with Fe sequestered in silicate minerals being the heaviest, due to preferential release of light Fe isotopes during dissolution of minerals. Actually and potentially plant-available Fe in soil can be extracted by 0.5 M HCl, which includes pools of water-extractable and exchangeable Fe, organically bound or adsorbed Fe, and poorly crystalline Fe oxides, altogether showing a depletion of heavy Fe isotopes with δ 56 Fe values down to −1.08‰. Depending on the Fe speciation and concentration present in the growth medium, plants can adapt their uptake strategy for Fe. Plants of the strategy I type especially take up light iron isotopes, while strategy II plants fractionate less towards light isotopes. Aboveground tissues usually show lighter Fe isotope signatures than the roots, with flowers (δ 56 Fe: −2.15 to −0.23‰) being isotopically the lightest. In freshwater systems, the most distinct Fe isotope fractionation is usually found at the oxic-anoxic interface, where redox conditions change and thus Fe speciation controls the degree of Fe isotope fractionation. Similar to soils, the δ 56 Fe values of unfiltered water mainly reflect averaged Fe isotope compositions across fractions with different particle sizes. In filtered freshwater (<0.45 μm), isolated colloid-sized fractions can exhibit either positive or negative δ 56 Fe values, depending on the chosen size fraction and the origin of the (nano) particles, with δ 56 Fe values up to +2.79‰ for fractions smaller than 0.003 μm from an arctic stream or down to −1.73‰ for dissolved Fe (<0.02 μm) from a boreal forested catchment. Most freshwater studies showed that rivers with elevated contents of dissolved organic carbon (DOC) tend to be isotopically heavier than those with lower DOC contents, while some studies also showed that rivers with high DOC can display light Fe isotopic signatures owing to the input of groundwater- and/or soil water-derived Fe. Finally, anthropogenic impacts can contribute to Fe isotope fractionation in freshwaters and may widen the range of δ 56 Fe values in the environment, with the lowest records found down to −5.29‰. Overall, our compilation reveals that Fe pools in different terrestrial system compartments vary in stable Fe isotope compositions, although the current database is still small. In order to use stable Fe isotopes as proxies to reconstruct the biogeochemical processes, future works should not solely rely on bulk δ 56 Fe assessments, but also involve the assessment of different fractionation factors for all biogeochemical pathways, which includes isotopic analyses among various pools of the terrestrial Fe cycle. © 2018 Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165961
Appears in Collections: 气候变化与战略
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作者单位: Institute of Bio- and Geosciences: Agrosphere, Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße, Jülich, 52428, Germany; Soil Science and Soil Ecology, Institute of Crop Science and Resource Conservation, University of Bonn, Nussalle 13, Bonn, 53115, Germany
Recommended Citation:
Wu B.,Amelung W.,Xing Y.,et al. Iron cycling and isotope fractionation in terrestrial ecosystems[J]. Earth Science Reviews,2019-01-01,190