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Rahman S, Trower EJ. Probing surface Earth reactive silica cycling using stable Si isotopes: Mass balance, fluxes, and deep time implications. SCIENCE ADVANCES 2023; 9:eadi2440. [PMID: 38055818 DOI: 10.1126/sciadv.adi2440] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Accepted: 11/07/2023] [Indexed: 12/08/2023]
Abstract
Geological reservoir δ30Si values have increasingly been applied as paleoclimate and paleoproductivity proxies. Many of these applications rely on the assumption that the surface Earth Si isotope budget is in mass balance with bulk silicate Earth, such that trends in δ30Si over time can be attributed to changes in flux to or from key silica reservoirs. We compiled δ30Si data from modern reservoirs representing the major sources and sinks of surface Earth reactive silica, to which we applied an inverse model to test assumptions about mass balance. We found that δ30Si values of reverse weathering products must closely match those of diatoms, conflicting with previous assumptions. Model results also revealed that of the 19 to 21 teramoles per year Si released during silicate mineral weathering, ~10 to 18 teramoles per year is stored in terrestrial silica sinks, consistent with assumptions of incongruent weathering reactions. Our results demonstrated that the modern silica cycle summary is in isotopic mass balance.
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Affiliation(s)
- Shaily Rahman
- Department of Geological Sciences, University of Colorado Boulder, Boulder, CO, USA
- Institute of Arctic and Alpine Research (INSTAAR), University of Colorado Boulder, Boulder, CO, USA
| | - Elizabeth J Trower
- Department of Geological Sciences, University of Colorado Boulder, Boulder, CO, USA
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2
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Cotroneo S, Kang M, Clark ID, Bataille CP. Applying Machine Learning to investigate metal isotope variations at the watershed scale: A case study with lithium isotopes across the Yukon River Basin. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 896:165165. [PMID: 37394077 DOI: 10.1016/j.scitotenv.2023.165165] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Revised: 06/14/2023] [Accepted: 06/25/2023] [Indexed: 07/04/2023]
Abstract
Constraining the multiple climatic, lithological, topographic, and geochemical variables controlling isotope variations in large rivers is often challenging with standard statistical methods. Machine learning (ML) is an efficient method for analyzing multidimensional datasets, resolving correlated processes, and exploring relationships between variables simultaneously. We tested four ML algorithms to elucidate the controls of riverine δ7Li variations across the Yukon River Basin (YRB). We compiled (n = 102) and analyzed new samples (n = 21), producing a dataset of 123 river water samples collected across the basin during the summer including δ7Li and extracted environmental, climatological, and geological characteristics of the drainage area for each sample from open-access geospatial databases. The ML models were trained, tuned, and tested under multiple scenarios to avoid issues such as overfitting. Random Forests (RF) performed best at predicting δ7Li across the basin, with the median model explaining 62 % of the variance. The most important variables controlling δ7Li across the basin are elevation, lithology, and past glacial coverage, which ultimately influence weathering congruence. Riverine δ7Li has a negative dependence on elevation. This reflects congruent weathering in kinetically-limited mountain zones with short residence times. The consistent ranking of lithology, specifically igneous and metamorphic rock cover, as a top feature controlling riverine δ7Li modeled by the RFs is unexpected. Further study is required to validate this finding. Rivers draining areas that were extensively covered during the last glacial maximum tend to have lower δ7Li due to immature weathering profiles resulting in short residence times, less secondary mineral formation and therefore more congruent weathering. We demonstrate that ML provides a fast, simple, visualizable, and interpretable approach for disentangling key controls of isotope variations in river water. We assert that ML should become a routine tool, and present a framework for applying ML to analyze spatial metal isotope data at the catchment scale.
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Affiliation(s)
- Sarina Cotroneo
- 25 Templeton Street, Department of Earth and Environmental Sciences, University of Ottawa, Ottawa, ON K1N 6N5, Canada.
| | - Myunghak Kang
- 25 Templeton Street, Department of Earth and Environmental Sciences, University of Ottawa, Ottawa, ON K1N 6N5, Canada
| | - Ian D Clark
- 25 Templeton Street, Department of Earth and Environmental Sciences, University of Ottawa, Ottawa, ON K1N 6N5, Canada
| | - Clément P Bataille
- 25 Templeton Street, Department of Earth and Environmental Sciences, University of Ottawa, Ottawa, ON K1N 6N5, Canada
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Alibakhshi A, Steffen J, Pinilla C, Hartke B. Comparison of Implicit and Explicit Solvent Approaches in Ab Initio Evaluation of Thermochemistry in Solution: Application in Studying Boron Isotope Fractionation in Water. J Phys Chem A 2023; 127:2503-2510. [PMID: 36917555 DOI: 10.1021/acs.jpca.3c00154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/16/2023]
Abstract
Evaluation of thermochemistry in solution plays a key role in numerous fields. For this task, the solvent effects are commonly included in theoretical computations based on either implicit or explicit solvent approaches. In the present study, we evaluate and compare the performance of some of the most widely applied methods based on these two approaches. For studying the solvent effect on thermochemistry with an explicit solvent, we demonstrate that partial normal mode analysis with frozen geometry of solvent molecules for multiple solute-solvent configurations can yield quite accurate and reliable results for a drastically reduced computational cost. As a case study, we consider the evaluation of the equilibrium constant for the boron isotope exchange between boric acid and borate (k3-4) in pure and saline water which is of high geochemical importance. Employing three different rigorous and high-precision theoretical approaches, we provide a reliable estimation of k3-4 which is a value within 1.028 to 1.030 for both pure and saline water which is in excellent agreement with experimental data.
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Affiliation(s)
- Amin Alibakhshi
- Theoretical Chemistry, Institute for Physical Chemistry, Christian-Albrechts-University, Olshausenstr. 40, 24118 Kiel, Germany
- Theoretical Chemistry, Ruhr-Universitaet Bochum, D-44780 Bochum, Germany
| | - Julien Steffen
- Theoretical Chemistry, Institute for Physical Chemistry, Christian-Albrechts-University, Olshausenstr. 40, 24118 Kiel, Germany
| | - Carlos Pinilla
- Departamento de Física y Geociencias, Universidad del Norte, Km 5 via Puerto Colombia, Barranquilla 080020, Colombia
- School of Chemistry, University of Bristol, Cantock's Close Road, BS8 1TS Bristol, U.K
| | - Bernd Hartke
- Theoretical Chemistry, Institute for Physical Chemistry, Christian-Albrechts-University, Olshausenstr. 40, 24118 Kiel, Germany
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Ganeshan K, Khanal R, Muraleedharan MG, Hellström M, Kent PRC, Irle S, van Duin ACT. Importance of Nuclear Quantum Effects on Aqueous Electrolyte Transport under Confinement in Ti 3C 2 MXenes. J Chem Theory Comput 2022; 18:6920-6931. [PMID: 36269878 DOI: 10.1021/acs.jctc.2c00771] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Protons display a high chemical activity and strongly affect the charge storage capability in confined interlayer spaces of two-dimensional (2D) materials. As such, an accurate representation of proton dynamics under confinement is important for understanding and predicting charge storage dynamics in these materials. While often ignored in atomistic-scale simulations, nuclear quantum effects (NQEs), e.g., tunneling, can be significant under confinement even at room temperature. Using the thermostatted ring polymer molecular dynamics implementation of path integral molecular dynamics (PIMD) in conjunction with the ReaxFF force field, density functional tight binding (DFTB), and NequIP neural network potential simulations, we investigate the role of NQEs on proton and water transport in bulk water and aqueous electrolytes under confinement in Ti3C2 MXenes. Although overall NQEs are relatively small, especially in bulk, we find that they can alter both quantitative values and qualitative trends on both proton transport and water self-diffusion under confinement relative to classical MD predictions. Therefore, our results suggest the need for NQEs to be considered to simulate aqueous systems under confinement for both qualitative and quantitative accuracy.
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Affiliation(s)
- Karthik Ganeshan
- Department of Mechanical Engineering, Pennsylvania State University, University Park, Pennsylvania16802, United States
| | - Rabi Khanal
- Computational Sciences and Engineering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Murali Gopal Muraleedharan
- Computational Sciences and Engineering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Matti Hellström
- Software for Chemistry and Materials B.V., Amsterdam1081HV, The Netherlands
| | - Paul R C Kent
- Center for Nanophase Materials Sciences and Computational Sciences and Engineering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Stephan Irle
- Computational Sciences and Engineering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Adri C T van Duin
- Department of Mechanical Engineering, Pennsylvania State University, University Park, Pennsylvania16802, United States
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Cendagorta JR, Shen H, Bačić Z, Tuckerman ME. Enhanced Sampling Path Integral Methods Using Neural Network Potential Energy Surfaces with Application to Diffusion in Hydrogen Hydrates. ADVANCED THEORY AND SIMULATIONS 2020. [DOI: 10.1002/adts.202000258] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
| | - Hengyuan Shen
- Department of Chemistry New York University Shanghai 1555 Century Avenue Pudong Shanghai 200122 China
| | - Zlatko Bačić
- Department of Chemistry New York University New York NY 10003 USA
- NYU‐ECNU Center for Computational Chemistry at NYU Shanghai 3663 Zhongshan Road, North Shanghai 200062 China
| | - Mark E. Tuckerman
- Department of Chemistry New York University New York NY 10003 USA
- NYU‐ECNU Center for Computational Chemistry at NYU Shanghai 3663 Zhongshan Road, North Shanghai 200062 China
- Courant Institute of Mathematical Sciences New York University New York NY 10012 USA
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Singha Deb AK, Sahu P, Boda A, Ali SM, Shenoy KT, Upadhyay D. DFT and MD simulation supplemented experiments for isotopic fractionation of zinc compounds using a macrocyclic crown ether appended polymeric resin. Phys Chem Chem Phys 2020; 22:14682-14693. [PMID: 32573611 DOI: 10.1039/d0cp01660h] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Isotope effect is a quantum mechanical phenomenon and thus poses a challenge for the separation of isotopes of an element of interest, especially for heavy elements. Isotopic fractionation of zinc is also quite difficult and challenging but is necessitated due to various applications of its isotopes ranging from nuclear medicine to nuclear power reactors. Here, we developed the dibenzo-18-crown-6 (DB18C6) ether-functionalized poly(methacrylic acid) (PMA) resin by exploiting the ion and isotope recognition ability of the crown ether using DFT/MD simulations followed by experiments for isotopic fractionation of zinc. The PMADB18C6 adsorbent was prepared and suitably characterized. Both computational and experimental findings demonstrate that the adsorption and isotope separation of zinc with PMADB18C6 are due to the molecular recognition effect of the "O" dipole of the crown ether. Furthermore, both MD simulations and experiments suggest Langmuir type adsorption isotherms. The adsorption of Zn2+ ions on the PMA resin is predicted to be endothermic, whereas it is exothermic on the PMADB18C6 resin, as revealed from the experimentally observed enthalpy change. A small scale fixed bed column study was demonstrated to test the scale-up application. The values of the experimental separation factors: 1.0013 for 66/64 and 1.0027 for 68/64 confirm the computationally predicted results of 1.00088 and 1.0010, respectively, thus establishing the combined strength of the theory and experiments for the identification of efficient fractionating agents for a complex quantum isotope effect which eventually helps in planning further experiments in view of medicinal and technological applications of zinc isotopes.
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Affiliation(s)
- A K Singha Deb
- Chemical Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai-400085, India.
| | - P Sahu
- Chemical Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai-400085, India.
| | - A Boda
- Chemical Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai-400085, India.
| | - Sk M Ali
- Chemical Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai-400085, India.
| | - K T Shenoy
- Chemical Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai-400085, India.
| | - D Upadhyay
- Homi Bhabha National Institute, Bhabha Atomic Research Centre, Trombay, Mumbai-400085, India and Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur, West Bengal 721302, India
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Karmakar S, Maji M, Mukherjee A. Modulation of the reactivity of nitrogen mustards by metal complexation: approaches to modify their therapeutic properties. Dalton Trans 2019; 48:1144-1160. [DOI: 10.1039/c8dt04503h] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Metal complexation of nitrogen mustards shows promise with an ability to control the mustards’ reactivity, perform selective hypoxia activation, overcome resistance, and control GSH deactivation.
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Affiliation(s)
- Subhendu Karmakar
- Department of Chemical Sciences
- Indian Institute of Science Education and Research Kolkata
- Mohanpur-741246
- India
| | - Moumita Maji
- Department of Chemical Sciences
- Indian Institute of Science Education and Research Kolkata
- Mohanpur-741246
- India
| | - Arindam Mukherjee
- Department of Chemical Sciences
- Indian Institute of Science Education and Research Kolkata
- Mohanpur-741246
- India
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Mallory JD, Mandelshtam VA. Nuclear Quantum Effects and Thermodynamic Properties for Small (H2O)1–21X– Clusters (X– = F–, Cl–, Br–, I–). J Phys Chem A 2018; 122:4167-4180. [DOI: 10.1021/acs.jpca.8b00917] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Joel D. Mallory
- Department of Chemistry, University of California, Irvine, California 92697, United States
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Poltavsky I, DiStasio RA, Tkatchenko A. Perturbed path integrals in imaginary time: Efficiently modeling nuclear quantum effects in molecules and materials. J Chem Phys 2018; 148:102325. [DOI: 10.1063/1.5006596] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Affiliation(s)
- Igor Poltavsky
- Physics and Materials Science Research Unit, University of Luxembourg, Luxembourg L-1511, Luxembourg
| | - Robert A. DiStasio
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA
| | - Alexandre Tkatchenko
- Physics and Materials Science Research Unit, University of Luxembourg, Luxembourg L-1511, Luxembourg
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Tuckerman M, Ceperley D. Preface: Special Topic on Nuclear Quantum Effects. J Chem Phys 2018; 148:102001. [DOI: 10.1063/1.5026714] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Affiliation(s)
- Mark Tuckerman
- Department of Chemistry, New York University, New York, New York 10003, USA
- Courant Institute of Mathematical Sciences, New York University, New York, New York 10012, USA
- NYU-ECNU Center for Computational Chemistry at NYU Shanghai, Shanghai 200062, China
| | - David Ceperley
- Department of Physics, University of Illinois Urbana-Champaign, Champaign, Illinois 61801, USA
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