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Hydrothermal (NN)-N-15-N-15 abundances constrain the origins of mantle nitrogen 期刊论文
NATURE, 2020, 580 (7803) : 367-+
作者:  Zhao, Steven;  Jang, Cholsoon;  Liu, Joyce;  Uehara, Kahealani;  Gilbert, Michael;  Izzo, Luke;  Zeng, Xianfeng;  Trefely, Sophie;  Fernandez, Sully;  Carrer, Alessandro;  Miller, Katelyn D.;  Schug, Zachary T.;  Snyder, Nathaniel W.;  Gade, Terence P.;  Titchenell, Paul M.;  Rabinowitz, Joshua D.;  Wellen, Kathryn E.
收藏  |  浏览/下载：14/0  |  提交时间：2020/05/13

Nitrogen is the main constituent of the Earth'  s atmosphere, but its provenance in the Earth'  s mantle remains uncertain. The relative contribution of primordial nitrogen inherited during the Earth'  s accretion versus that subducted from the Earth'  s surface is unclear(1-6). Here we show that the mantle may have retained remnants of such primordial nitrogen. We use the rare (NN)-N-15-N-15 isotopologue of N-2 as a new tracer of air contamination in volcanic gas effusions. By constraining air contamination in gases from Iceland, Eifel (Germany) and Yellowstone (USA), we derive estimates of mantle delta N-15 (the fractional difference in N-15/N-14 from air), N-2/Ar-36 and N-2/He-3. Our results show that negative delta N-15 values observed in gases, previously regarded as indicating a mantle origin for nitrogen(7-10), in fact represent dominantly air-derived N-2 that experienced N-15/N-14 fractionation in hydrothermal systems. Using two-component mixing models to correct for this effect, the (NN)-N-15-N-15 data allow extrapolations that characterize mantle endmember delta N-15, N-2/Ar-36 and N-2/He-3 values. We show that the Eifel region has slightly increased delta N-15 and N-2/Ar-36 values relative to estimates for the convective mantle provided by mid-ocean-ridge basalts(11), consistent with subducted nitrogen being added to the mantle source. In contrast, we find that whereas the Yellowstone plume has delta N-15 values substantially greater than that of the convective mantle, resembling surface components(12-15), its N-2/Ar-36 and N-2/He-3 ratios are indistinguishable from those of the convective mantle. This observation raises the possibility that the plume hosts a primordial component. We provide a test of the subduction hypothesis with a two-box model, describing the evolution of mantle and surface nitrogen through geological time. We show that the effect of subduction on the deep nitrogen cycle may be less important than has been suggested by previous investigations. We propose instead that high mid-ocean-ridge basalt and plume delta N-15 values may both be dominantly primordial features.


  
Wafer-scale single-crystal hexagonal boron nitride monolayers on Cu (111) 期刊论文
NATURE, 2020, 579 (7798) : 219-+
作者:  Luong, Duy X.;  Bets, Ksenia V.;  Algozeeb, Wala Ali;  Stanford, Michael G.;  Kittrell, Carter;  Chen, Weiyin;  Salvatierra, Rodrigo V.;  Ren, Muqing;  McHugh, Emily A.;  Advincula, Paul A.;  Wang, Zhe;  Bhatt, Mahesh;  Guo, Hua;  Mancevski, Vladimir;  Shahsavari, Rouzbeh
收藏  |  浏览/下载：80/0  |  提交时间：2020/07/03

Ultrathin two-dimensional (2D) semiconducting layered materials offer great potential for extending Moore'  s law of the number of transistors in an integrated circuit(1). One key challenge with 2D semiconductors is to avoid the formation of charge scattering and trap sites from adjacent dielectrics. An insulating van der Waals layer of hexagonal boron nitride (hBN) provides an excellent interface dielectric, efficiently reducing charge scattering(2,3). Recent studies have shown the growth of single-crystal hBN films on molten gold surfaces(4) or bulk copper foils(5). However, the use of molten gold is not favoured by industry, owing to its high cost, cross-contamination and potential issues of process control and scalability. Copper foils might be suitable for roll-to-roll processes, but are unlikely to be compatible with advanced microelectronic fabrication on wafers. Thus, a reliable way of growing single-crystal hBN films directly on wafers would contribute to the broad adoption of 2D layered materials in industry. Previous attempts to grow hBN monolayers on Cu (111) metals have failed to achieve mono-orientation, resulting in unwanted grain boundaries when the layers merge into films(6,7). Growing single-crystal hBN on such high-symmetry surface planes as Cu (111)(5,8) is widely believed to be impossible, even in theory. Nonetheless, here we report the successful epitaxial growth of single-crystal hBN monolayers on a Cu (111) thin film across a two-inch c-plane sapphire wafer. This surprising result is corroborated by our first-principles calculations, suggesting that the epitaxial growth is enhanced by lateral docking of hBN to Cu (111) steps, ensuring the mono-orientation of hBN monolayers. The obtained single-crystal hBN, incorporated as an interface layer between molybdenum disulfide and hafnium dioxide in a bottom-gate configuration, enhanced the electrical performance of transistors. This reliable approach to producing wafer-scale single-crystal hBN paves the way to future 2D electronics.


  
Automatic Correction of Contaminated Images for Assessment of Reservoir Surface Area Dynamics 期刊论文
GEOPHYSICAL RESEARCH LETTERS, 2018, 45 (12) : 6092-6099
作者:  Zhao, Gang;  Gao, Huilin
收藏  |  浏览/下载：4/0  |  提交时间：2019/04/09
Landsat  reservoir area  contamination  image enhancement  Google Earth Engine  
Impact of an historic underground gas well blowout on the current methane chemistry in a shallow groundwater system 期刊论文
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 2018, 115 (2) : 296-301
作者:  Schout, Gilian;  Hartog, Niels;  Hassanizadeh, S. Majid;  Griffioen, Jasper
收藏  |  浏览/下载：7/0  |  提交时间：2019/11/27
groundwater contamination  well blowouts  methane  isotopic fingerprinting  anaerobic methane oxidation  
Contamination of the Arctic reflected in microbial metagenomes from the Greenland ice sheet 期刊论文
ENVIRONMENTAL RESEARCH LETTERS, 2017, 12 (7)
作者:  Hauptmann, Aviaja L.;  Sicheritz-Ponten, Thomas;  Cameron, Karen A.;  Baelum, Jacob;  Plichta, Damian R.;  Dalgaard, Marlene;  Stibal, Marek
收藏  |  浏览/下载：4/0  |  提交时间：2019/04/09
metagenomics  cryosphere  contamination  Greenland ice sheet  microbial ecology  
Screening of UV chemicals, bisphenols and siloxanes in the Arctic 科技报告
来源：Center for International Climate and Environmental Research-Oslo (CICERO). 出版年： 2016
作者:  Lucia, Magali;  Gabrielsen, Geir W.;  Herzke, Dorte;  Christensen, Guttorm
收藏  |  浏览/下载：5/0  |  提交时间：2019/04/05
contamination  chemicals  
State of Europe's seas 科技报告
来源：European Environment Agency (EEA). 出版年： 2015
作者:  [null]
收藏  |  浏览/下载：6/0  |  提交时间：2019/04/05
eutrophication  seabed habitats  marine litter  turtles  eu marine strategy framework directive  marine mammals  marine food webs  marine ecosystems  water column habitats  seabirds  marine biodiversity  underwater noise  contamination  ecosystems  marine