ANALYTICAL CHEMISTRY
·
2020
·
IF 6.785
Bo Wang,Shuai Zheng,Yan Huang,Ying Wang,Zhenyu Zhu,Ran Ma,Yu Zhao,Xijie Yin,Jing Su,Juan Xiong,Benli Zhang,Youping Zhou
The 18O/16O (and 15N/14N) ratio of natural nitrate (NO3–) and nitrite (NO2–) can be used to extract valuable information about their source and fate as environmental contaminants, their metabolism as macronutrients in plants and animals, and their behavior in the N biogeochemical cycle. We developed an accurate, precise, sensitive (minimum sample size: 0.2 μg NO3–-equivalent), and reliable (minimal oxygen exchange, loss, or gain) method to selectively isolate and purify nitrate and nitrite from natural water, soil, air, and plant materials by strong anion exchange (SAX) for low- to normal-salinity samples or strong cation exchange (SCX) for high-salinity samples, followed by quantitative conversion to their respective benzyl esters, which can be separated and individually analyzed for δ18O (and potentially δ15N) by gas chromatography (GC)/pyrolysis/GC/isotope-ratio mass spectrometry (IRMS). The method compares favorably with the currently popular bacterial denitrification and chemical reduction methods, in terms of sensitivity and reliability, and has the potential to simultaneously measure δ15N and δ18O of nitrate and nitrite from natural samples of various origins.
研究领域:
环境科学
·
生物地球化学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
CHINESE SCIENCE BULLETIN
·
2005
·Vol. 50
·期 23
·2765-2769
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IF 0.683
Xiuyang Jiang,Yongjin Wang,Xinggong Kong,Jiangying Wu,Xiaohua Shao,Zhifeng Xia,Hai Cheng
230 Th ages and oxygen isotope data of a stalagmite from Shanbao Cave in Hubei Province characterize the East Asian Monsoon precipitation from 133 to 127 ka. The decadal-scale high-resolution δ 18 O record reveals a detailed transitional process from the Penultimate Glaciation to the Last Interglaciation. As established with 230 Th dates, the age of the Termination II is determined to be 129.5±1.0 kaBP, which supports the Northern Hemisphere insolation as the triggers for the ice-age cycles. In our δ 18 O record, the glacial/ interglacial fluctuation reaches about 4‰, almost the same level as in other Asian Monsoon cave stalagmite δ 18 O records. The transition of the glacial/interglacial period in our record can be recognized as four stepwise stages, among which, a rapid rise of monsoon precipitation follows the stage of “Termination II pause”. The rapid rise is synchronous with the abrupt change of global methane concentration, which reflects that an increase in both Asian Monsoon precipitation and tropical wetland plays an important role in the global climate changes.
研究领域:
古气候学
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第四纪科学
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同位素地球化学
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气候变化
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季风动力学
✓ 已验证
DOI
高影响因子
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
·
2024
·Vol. 129
·期 3
·e2023JB027306
·
IF 3.9
Yanyan Zhou,Mingguo Zhai,Ross N. Mitchell,Peter A. Cawood,Guangyu Huang,Christopher J. Spencer,Mimi Chen,Yibing Li,Taiping Zhao,Tengfei Wu
The start of the Paleoproterozoic supercontinent cycle is typically taken as the initiation of orogenesis at ca. 2.1 Ga leading to the assembly of Earth's first supercontinent, Columbia. However, the dearth of ca. 2.5–2.2 Ga geological records makes it difficult to deduce tectonic factors during the onset of the Paleoproterozoic supercontinent cycle. The petrogenesis of tonalite–trondhjemite–granodiorite (TTG) provides useful proxies for tracing prevailing geodynamic regimes of early continental evolution. However, marked decreases of TTG and other magmatism occurred across the Archean–Paleoproterozoic transition and have previously precluded forming testable hypotheses. Early Paleoproterozoic TTGs have been identified in the North China Craton (NCC) and other cratons, which may represent the last major pulse of TTGs globally. Here we present low δ 18 O and δ 30 Si ca. 2.3 Ga TTGs from the NCC, together with thermodynamic modeling and compilation of stable O and Si isotopes for TTGs globally through time. The ca. 2.3 Ga TTGs were derived from the partial melting of Archean basaltic crust and give lighter average zircon δ 18 O (3.15 ± 0.35‰) and whole-rock δ 30 Si values (−0.17 ± 0.08‰) than most Archean TTGs. Considering coeval mafic-felsic igneous rocks, and lithospheric thinning since ca. 2.5 Ga based on estimated crustal thickness through the Neoarchean–Paleoproterozoic, we posit the onset of an intraplate rifting consistent with the anomalous low-δ 18 O magmatism. Continental rifting of Archean cratons/supercratons plausibly hints at the formation of rifts driving subduction initiation as the veritable onset of the Paleoproterozoic supercontinent cycle. Key Points Ca. 2.3 Ga tonalite–trondhjemite–granodiorite (TTG) in the North China Craton (NCC) shows the affinity of low-pressure (LP) TTGs and contains low zircon δ 18 O and bulk-rock δ 30 Si values Ca. 2.3 Ga low δ 18 O and δ 30 Si TTG and coeval low-δ 18 O magmatism herald the initiation of an intraplate rift setting Such intraplate rifting hints at the formation of rifts driving subduction as the real onset of the Paleoproterozoic supercontinent cycle Plain Language Summary The Earth's first supercontinent, Paleoproterozoic–Mesoproterozoic Columbia, likely began to form during ca. 2.1 Ga (billion years ago) orogenesis. However, the limited record of ca. 2.5–2.2 Ga magmatism makes it difficult to establish how exactly the Paleoproterozoic supercontinent cycle commenced. The tonalite–trondhjemite–granodiorite (TTG) series of felsic rocks forms the backbone of Archean cratons and can provide key constraints on the Earth's early tectonic evolution. Some early Paleoproterozoic TTGs occur in North China and other cratons, which may represent the last major TTG event globally, presenting the possibility to fulfill this role. Here we carry out zircon O and bulk-rock Si isotopic analyses and thermodynamic modeling for these ca. 2.3 Ga TTGs, together with Si-O-Hf data compilation of TTGs globally through time. These ca. 2.3 Ga TTGs show lighter zircon O and bulk-rock Si isotopes than those of Archean TTGs. They might be formed within-plate, associated with lithospheric thinning and mantle-crust remelting to form mafic-felsic magmatism. We propose an intraplate rift setting for this early ca. 2.3 Ga magmatism, which drove the mobilism that led to the subsequent 2.1–1.8 Ga orogenesis and should be posited as the real start of the Paleoproterozoic supercontinent cycle.
研究领域:
地质学
·
地球化学
✓ 已验证
DOI
高影响因子
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