Publications by authors named "Zhenbing She"

3 Publications

  • Page 1 of 1

Raman spectra and surface changes of microplastics weathered under natural environments.

Sci Total Environ 2020 Oct 5;739:139990. Epub 2020 Jun 5.

School of Environmental Studies, China University of Geosciences, Wuhan 430078, China. Electronic address:

Raman spectroscopy can be used to effectively analyze submicron- to microsized microplastics, but Raman spectra of weathered microplastics commonly show deviations from those of unweathered microplastics and are often affected by fluorescence. However, studies of weathering-induced surface changes in microplastics have been limited to laboratory simulations. To systematically study Raman spectra and surface changes of microplastics weathered under natural environments, we collected microplastics from sediments around waste plastics processing and recycling industries in Laizhou City, Shandong Province, East China. Raman spectra of weathered microplastics differ greatly from standard spectra of unweathered plastic material. Peaks in the Raman spectra of weathered microplastics are weakened and even invisible. A preliminary Raman database of weathered microplastics (RDWP) including 124 Raman spectra of weathered microplastics was built to accurately identify microplastics in natural environments, and it is open to all users. FTIR spectroscopy revealed the presence of oxygen-containing functional groups and CC bonds related to oxidation and chain scission. SEM showed that weathered microplastics had rough surfaces and that PP was more easily fractured than PE. Complementary C and O elemental maps suggested that the O/C ratio is a potential indicator of oxidation degree. EDS revealed titanium on PET and PVC surfaces, which is related to titanium dioxide typically used as a light-blocking aid. Our data document that Raman spectroscopy has great potential in the identification of naturally weathered microplastics and that combined spectral and elemental analyses can be useful in deciphering the degradation processes of microplastics under natural conditions. CAPSULE: Raman spectra of weathered microplastics differ greatly from standard spectra. A Raman database of weathered microplastics is established. Surface changes of weathered microplastics were systematically studied.
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http://dx.doi.org/10.1016/j.scitotenv.2020.139990DOI Listing
October 2020

Massive formation of early diagenetic dolomite in the Ediacaran ocean: Constraints on the "dolomite problem".

Proc Natl Acad Sci U S A 2020 06 8;117(25):14005-14014. Epub 2020 Jun 8.

Institute for Geology, Mineralogy, and Geophysics, Ruhr University Bochum, D-44801 Bochum, Germany.

Paleozoic and Precambrian sedimentary successions frequently contain massive dolomicrite [CaMg(CO)] units despite kinetic inhibitions to nucleation and precipitation of dolomite at Earth surface temperatures (<60 °C). This paradoxical observation is known as the "dolomite problem." Accordingly, the genesis of these dolostones is usually attributed to burial-hydrothermal dolomitization of primary limestones (CaCO) at temperatures of >100 °C, thus raising doubt about the validity of these deposits as archives of Earth surface environments. We present a high-resolution, >63-My-long clumped-isotope temperature (T) record of shallow-marine dolomicrites from two drillcores of the Ediacaran (635 to 541 Ma) Doushantuo Formation in South China. Our T record indicates that a majority (87%) of these dolostones formed at temperatures of <100 °C. When considering the regional thermal history, modeling of the influence of solid-state reordering on our T record further suggests that most of the studied dolostones formed at temperatures of <60 °C, providing direct evidence of a low-temperature origin of these dolostones. Furthermore, calculated δO values of diagenetic fluids, rare earth element plus yttrium compositions, and petrographic observations of these dolostones are consistent with an early diagenetic origin in a rock-buffered environment. We thus propose that a precursor precipitate from seawater was subsequently dolomitized during early diagenesis in a near-surface setting to produce the large volume of dolostones in the Doushantuo Formation. Our findings suggest that the preponderance of dolomite in Paleozoic and Precambrian deposits likely reflects oceanic conditions specific to those eras and that dolostones can be faithful recorders of environmental conditions in the early oceans.
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http://dx.doi.org/10.1073/pnas.1916673117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7321997PMC
June 2020

The onset of widespread marine red beds and the evolution of ferruginous oceans.

Nat Commun 2017 08 30;8(1):399. Epub 2017 Aug 30.

State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing, 100083, China.

Banded iron formations were a prevalent feature of marine sedimentation ~3.8-1.8 billion years ago and they provide key evidence for ferruginous oceans. The disappearance of banded iron formations at ~1.8 billion years ago was traditionally taken as evidence for the demise of ferruginous oceans, but recent geochemical studies show that ferruginous conditions persisted throughout the later Precambrian, and were even a feature of Phanerozoic ocean anoxic events. Here, to reconcile these observations, we track the evolution of oceanic Fe-concentrations by considering the temporal record of banded iron formations and marine red beds. We find that marine red beds are a prominent feature of the sedimentary record since the middle Ediacaran (~580 million years ago). Geochemical analyses and thermodynamic modelling reveal that marine red beds formed when deep-ocean Fe-concentrations were > 4 nM. By contrast, banded iron formations formed when Fe-concentrations were much higher (> 50 μM). Thus, the first widespread development of marine red beds constrains the timing of deep-ocean oxygenation.The evolution of oceanic redox state in the past is poorly known. Here, the authors present a temporal record of banded iron formations and marine red beds, which indicate deep-ocean oxygenation occurred in the middle Ediacaran, coinciding with the onset of widespread marine red beds.
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http://dx.doi.org/10.1038/s41467-017-00502-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5577183PMC
August 2017