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  • 更新日期:2018-01-18
  • 更新日期:2018-01-18
  • Iron and Arsenic Speciation during As(III) Oxidation by Manganese Oxides in the Presence of Fe(II): Molecular-Level Characterization using XAFS, Mössbauer, and TEM Analysis
    ACS Earth Space Chem. Pub Date : 2018-01-17
    Yun Wu, Ravi K. Kukkadapu, Kenneth J. T. Livi, Wenqian Xu, Wei Li, Donald L. Sparks

    The redox state and speciation of the metalloid arsenic (As) determine its toxicity and mobility. Knowledge of biogeochemical processes influencing the As redox state is therefore important to understand and predict its environmental behavior. Many previous studies examined As(III) oxidation by various Mn-oxides, but little is known concerning the environmental influences (e.g. co-existing ions) on the process. In this study, we investigated the mechanisms of As(III) oxidation by a poorly crystalline hexagonal birnessite (δ-MnO2) in the presence of Fe(II) using X-ray absorption spectroscopy (XAS), Mössbauer spectroscopy and transmission electron microscopy (TEM) coupled with energy-dispersive X-ray spectroscopy (EDS). The K-edge X-ray absorption near edge spectroscopy (XANES) analysis revealed that, at low Fe(II) concentration (100 μM), As(V) was the predominant As species on the solid phase, while at higher Fe(II) concentrations (200-1000 μM), both As(III) and As(V) were sorbed on the solid phase. As K-edge extended X-ray absorption fine structure spectroscopy (EXAFS) analysis showed an increasing As-Mn/Fe distance over time, indicating As prefers to bind with the newly formed Fe(III)-(hydr)oxides. As adsorbed on Fe(III)-(hydr)oxides as a bidentate binuclear corner-sharing complex. Both Mössbauer and TEM-EDS investigations demonstrated that oxidized Fe(III) products formed during Fe(II) oxidation by δ-MnO2 were predominantly ferrihydrite, goethite, and ferric arsenate like compounds. However, Fe EXAFS analysis also suggested the formation of a small amount of lepidocrocite. The Mn K-edge XANES data indicated that As(III) and Fe(II) oxidation occurs as a two electron transfer with δ-MnO2 and the observed Mn(III) is due to conproportionation of surface sorbed Mn(II) with Mn(IV) in the δ-MnO2 structure. This study reveals that the mechanisms of As(III) oxidation by δ-MnO2 in the presence of Fe(II) are very complex, involving many simultaneous reactions, and the formation of Fe(III)-(hydr)oxides plays a very important role in reducing As mobility.

  • Abundance and sources of phthalic acids, benzene-tricarboxylic acids and phenolic acids in PM2.5 at urban and suburban sites in Southern China
    ACS Earth Space Chem. Pub Date : 2018-01-11
    Xiao He, X. H. Hilda Huang, Ka Shing Chow, Qiongqiong Wang, Ting Zhang, Dui Wu, Jian Zhen Yu

    The organic composition of airborne fine particulate matter (PM2.5, aerodynamic diameter less than 2.5 micrometers) at a molecular level has yet to be achieved, hindering a full understanding of the climatic impacts and health effects of PM2.5. Compounds containing aromatic rings are closely associated with optically active brown carbon and toxicologically important quinones. In this work, a group of ten aromatic organic acids including three phthalic acids, four phenolic acids and three benzene-tricarboxylic acids (BTCAs) in PM2.5 were studied for their abundance and potential sources through quantifying their ambient concentrations at four sites in the Pearl River Delta (PRD) region in Southern China, where biomass burning and anthropogenic emissions are both significant PM sources. Average concentrations of individual aromatic acids in a total of 240 PM2.5 samples collected throughout 2012 were in the order of 0.1-20 ng/m3, with p-and o-phthalic acid being the most abundant. Inter-species correlation analysis with known PM source tracers reveals different source origins for the ten aromatic acids. The four phenolic acids, all possessing partial lignin structures, are highly correlated with levoglucosan, indicating their association with biomass burning emissions. Specific lignin tracer ratios characteristic of different types of biomass fuels (i.e., cinnamyl- to vanillyl-phenol ratio) revealed significant influence of crop burning emissions in the PRD region. The three BTCAs have moderate correlation with sulfate but no correlation with levoglucosan, suggesting a strong association with secondary formation origins while negating a strong link with biomass burning. The three phthalic acids are moderately correlated with sulfate, levoglucosan, and a number of polycyclic aromatic hydrocarbons (PAHs), indicating multiple significant sources. This study provides a valuable data set towards establishing quantitative links between molecular composition of organic matter and the optical and toxicological properties of PM2.5 as well as assisting identification of tracers for PM2.5 sources.

  • Phase transitions and hygroscopic growth of Mg(ClO4)2, NaClO4, and NaClO4∙H2O: implications for the stability of aqueous water in hyperarid environments on Mars and on Earth
    ACS Earth Space Chem. Pub Date : 2018-01-11
    Xiaohong Jia, Wenjun Gu, Yongjie Li, Peng Cheng, Yujing Tang, Liya Guo, Xinming Wang, Mingjin Tang

    In general pure liquid water is not thermodynamically stable on Mars due to the extremely cold and dry environment. The presence in the soil of perchlorates, which could lower the freezing point of water and form aqueous solutions by taking up water vapor even under subsaturated conditions, has been proposed to explain the possible existence of liquid water on Mars and in some hyperarid environments on Earth. In this work, the phase transitions and hygroscopic growth of Mg(ClO4)2, NaClO4, and NaClO4∙H2O were investigated between 278 and 303 K. In this temperature range, we found that anhydrous Mg(ClO4)2 was completely converted to Mg(ClO4)2∙6H2O at RH as low as <1%. In contrast, anhydrous NaClO4 was stable at RH below 20%, and NaClO4∙H2O was completely transformed to anhydrous NaClO4 at <1% RH; when RH was increased to 30%, anhydrous NaClO4 was transformed to NaClO4∙H2O. We also found that the deliquescence relative humidity (DRH) of NaClO4∙H2O decreased from ~51.5% at 278 K to ~43.5% at 303 K, exhibiting a negative dependence on temperature. In addition, the amounts of water in the NaClO4 solution were quantitatively determined as a function of RH at 278, 288, and 298 K. This work considerably furthers our understanding of the hygroscopic properties of perchlorates under different conditions, as well as the hydrological cycles on Mars and in other hyperarid environments, such as the Atacama Desert on Earth.

  • Isotopic Characterization of Mercury in Natural Gas via Analysis of Mercury Removal Unit Catalysts
    ACS Earth Space Chem. Pub Date : 2018-01-08
    Spencer J. Washburn, Joel D. Blum, Marcus W. Johnson, Jodie M. Tomes, Peter J. Carnell
  • Phase Diagram of the Ternary Water-Tetrahydrofuran-Ammonia System at Low Temperatures. Implications for Clathrate Hydrates and Outgassing on Titan
    ACS Earth Space Chem. Pub Date : 2018-01-05
    M. Victoria Munoz-Iglesias, Mathieu Choukroun, Tuan H. Vu, Robert Hodyss, Ahmed Mahjoub, William D Smythe, Christophe Sotin

    Titan’s icy shell is expected to contain predominantly methane clathrate hydrates, water ice Ih, and possibly ammonia hydrates, beneath a cover of diverse organics formed via atmospheric photochemistry. The dissociation of clathrate hydrates has long been inferred as a potential replenishment mechanism for atmospheric methane, however pure methane clathrates would be stable all the way to the surface. The melting of ammonia hydrates and subsequent interaction with methane clathrates could favor the dissociation of clathrates at much lower temperatures, due to the strong antifreeze effect of ammonia. In order to better understand the phase behavior of clathrate hydrates in presence of ammonia, we have developed phase diagrams for the ternary system water-ammonia-tetrahydrofuran at 1 bar and in the temperature range 77-280 K via differential scanning calorimetry and Raman spectroscopy. We have been able to determine how ammonia promotes the start of a partial dissociation of THF-clathrates at temperatures far colder than the liquidus. We have also established that this ternary system exhibits a complex chemistry, with multiple phases forming in thermodynamic equilibrium because of a phase separation between a THF-dominated liquid and a H2O-NH3 dominated liquid. In addition to the expected THF-clathrates, we report the formation of other mineral phases such as ammonia hydrates, a new THF-NH3-rich phase, and potentially mixed THF-NH3 clathrates. Partial dissociation of ~ 10% of the clathrate reservoir would release to Titan’s atmosphere methane amounts sufficient to sustain the hydrocarbon cycle for 650 My, which is commensurate with the age of the present atmosphere.

  • 更新日期:2018-01-05
  • Atmospheric Reactivity of Fullerene (C60) Aerosols
    ACS Earth Space Chem. Pub Date : 2018-01-05
    Dhruv Mitroo, Jiewei Wu, Peter F. Colletti, Seung Soo Lee, Michael J. Walker, William H. Brune, Brent J. Williams, John D. Fortner
  • 更新日期:2017-12-31
  • Binding geometries of silicate species on ferrihydrite surfaces
    ACS Earth Space Chem. Pub Date : 2017-12-29
    Xiaoming Wang, James David Kubicki, Jean-François Boily, Glenn Waychunas, Yongfeng Hu, Xionghan Feng, Mengqiang Zhu

    Silicate sorption on ferrihydrite surfaces, as monomers, oligomers, and polymers, strongly affects ferrihydrite crystallinity, thermodynamic stability, and surface reactivity. How these silicate species bind on ferrihydrite surfaces is, however, not well understood. We have determined silicate binding geometries using a combination of X-ray absorption spectroscopy (XAS), differential atomic pair distribution function (d-PDF) analysis, and density functional theory (DFT) calculations. Silicon K-edge absorption pre-edges and DFT-predicted energies indicate that silicate forms monomeric monodentate-mononuclear (MM) complexes at low silicate sorption loadings. With increasing silicate loading, the pre-edge peak shifts to higher energies, suggesting changes in silicate binding geometry towards multi-dentate complexation. The d-PDF analysis determines the Si–Fe interatomic distance to be ~ 3.25 Å for the high loading samples. The DFT calculations indicate that such distance corresponds to an oligomer in the bidentate-binuclear (BB) binding geometry. The transition of the silicate sorption geometry accompanied with polymerization can affect stability of ferrihydrite and its adsorption and redox reactivity, and increase the degree of Si isotopic fractionation upon silicate sorption on Fe oxides. Monodentate-mononuclear monomeric complexes and bidentate-binuclear oligomeric complexes should be used for surface complexation models predicting silicate sorption on Fe oxide surfaces.

  • Model Evaluation of New Techniques for Maintaining High-NO Conditions in Oxidation Flow Reactors for the Study of OH-Initiated Atmospheric Chemistry
    ACS Earth Space Chem. Pub Date : 2017-12-22
    Zhe Peng, Brett B. Palm, Douglas A. Day, Ranajit K. Talukdar, Weiwei Hu, Andrew T. Lambe, William H. Brune, Jose L. Jimenez
  • Small But Important: The Role of Small Floodplain Tributaries to River Nutrient Budgets
    ACS Earth Space Chem. Pub Date : 2017-12-22
    Indra S. Sen, Soumita Boral, Sudhakar Ranjan, Sampat K. Tandon
  • 更新日期:2017-12-22
  • Cohesive Vibrational and Structural Depiction of Intercalated Water in Montmorillonite
    ACS Earth Space Chem. Pub Date : 2017-12-19
    Merve Yeşilbaş, Michael Holmboe, Jean-François Boily
  • 更新日期:2017-12-20
  • Absorbing Refractive Index and Direct Radiative Forcing of Atmospheric Brown Carbon over Gangetic Plain
    ACS Earth Space Chem. Pub Date : 2017-12-12
    P. M. Shamjad, R. V. Satish, Navaneeth M. Thamban, N. Rastogi, S. N. Tripathi
  • Ozone Decomposition on Kaolinite as a Function of Monoterpene Exposure and Relative Humidity
    ACS Earth Space Chem. Pub Date : 2017-12-12
    Zoe L. Coates Fuentes, Theresa M. Kucinski, Ryan Z. Hinrichs
  • How Could a Freshwater Swamp Produce a Chemical Signature Characteristic of a Saltmarsh?
    ACS Earth Space Chem. Pub Date : 2017-12-11
    Terrence A. McCloskey, Christopher G. Smith, Kam-biu Liu, Marci Marot, Christian Haller
  • 更新日期:2017-12-10
  • Seasonal Characterization of Organic Nitrogen in Atmospheric Aerosols Using High Resolution Aerosol Mass Spectrometry in Beijing, China
    ACS Earth Space Chem. Pub Date : 2017-12-08
    Weiqi Xu, Yele Sun, Qingqing Wang, Wei Du, Jian Zhao, Xinlei Ge, Tingting Han, Yingjie Zhang, Wei Zhou, Jie Li, Pingqing Fu, Zifa Wang, Douglas R. Worsnop
  • Criegee Intermediate–Alcohol Reactions, A Potential Source of Functionalized Hydroperoxides in the Atmosphere
    ACS Earth Space Chem. Pub Date : 2017-12-07
    Max R. McGillen, Basile F.E. Curchod, Rabi Chhantyal-Pun, Joseph M. Beames, Nathan Watson, M. Anwar H. Khan, Laura McMahon, Dudley E. Shallcross, Andrew J. Orr-Ewing
  • Crystal-Chemical Composition of Dicoctahedral Smectites: An Energy-Based Assessment of Empirical Relations
    ACS Earth Space Chem. Pub Date : 2017-11-21
    Stephan Kaufhold, Alena Kremleva, Sven Krüger, Notker Rösch, Katja Emmerich, Reiner Dohrmann
  • Characterization of Light-Absorbing Oligomers from Reactions of Phenolic Compounds and Fe(III)
    ACS Earth Space Chem. Pub Date : 2017-11-21
    Avi Lavi, Peng Lin, Bhaskar Bhaduri, Raanan Carmieli, Alexander Laskin, Yinon Rudich
  • 更新日期:2017-11-21
  • 更新日期:2017-11-09
  • Characterization of light-absorbing oligomers from reactions of phenolic compounds and Fe (III)
    ACS Earth Space Chem. Pub Date : 2017-11-07
    Avi Lavi, Peng Lin, Bhaskar Bhaduri, Alexander Laskin, Yinon Rudich

    Phenolic compounds are common constituents of atmospheric aerosols. They form by pyrolysis of lignin and by bio-degradation of plant material and are commonly found in biomass burning plumes, re-suspended soil dust and in anthropogenic secondary organic aerosols (SOA). In this study, we show that reactions of Fe(III), a major constituent of mineral dust, with several phenolic compounds (guaiacol, catechol, syringol, o- and p-cresol) that are common in atmospheric aerosols, result in the formation of water insoluble light-absorbing compounds and reduced Fe(II). The study was conducted under acidic conditions (pH=1-2), relevant for areas impacted by biomass burning, anthropogenic emissions and mineral dust. The reaction products have been characterized using a high performance liquid chromatography coupled to photo diode array and high resolution mass spectrometry detectors , UV-visible spectroscopy, X-ray photoelectron spectroscopy and thermal gravimetric analysis. The major identified chromophores are oligomers of the reaction precursors that efficiently absorb light between 300nm and 500nm. The amounts of oligomers vary significantly between the systems studied. The highest amount was observed for guaiacol and catechol, and the least were detected in the syringol experiments, suggesting that the oligomerization proceeds through carbon-carbon coupling preferred at para- and ortho- positions, coupled to the reduction of Fe(III) to Fe(II). The results suggest that aqueous-phase radical reactions of phenolic compounds may be an efficient source of light-absorbing atmospheric organic compounds (Brown Carbon) that plays important roles in Earth’s radiative forcing on global and regional scales and of quinones that can affect health.

  • 更新日期:2017-11-05
  • Impact of Intrinsic Structural Properties on the Hydration of 2:1 Layer Silicates
    ACS Earth Space Chem. Pub Date : 2017-11-03
    Florian Schnetzer, Cliff T. Johnston, Gnanasiri S. Premachandra, Nicolas Giraudo, Rainer Schuhmann, Peter Thissen, Katja Emmerich
  • Cooperative and Inhibited Adsorption of d-Ribose onto Brucite [Mg(OH)2] with Divalent Cations
    ACS Earth Space Chem. Pub Date : 2017-11-03
    Charlene F. Estrada, Alyssa K. Adcock, Dimitri A. Sverjensky, Robert M. Hazen
  • Highly Time-Resolved Atmospheric Observations Using a Continuous Fine Particulate Matter and Element Monitor
    ACS Earth Space Chem. Pub Date : 2017-10-30
    Hitoshi Asano, Tomoki Aoyama, Yusuke Mizuno, Yukihide Shiraishi
  • Heterogeneous Ni- and Cd-Bearing Ferrihydrite Precipitation and Recrystallization on Quartz under Acidic pH Condition
    ACS Earth Space Chem. Pub Date : 2017-10-30
    Chong Dai, Mingxi Lin, Yandi Hu

    Ferrihydrite, as one of the most common naturally occurring iron oxides, can sequester toxic metals through coprecipitation. In this study, using grazing-incidence small angle X-ray scattering (GISAXS), the heterogeneous precipitation of pure, Ni-, and Cd- bearing ferrihydrite on quartz were quantified in 0.1 mM Fe3+ solutions in the absence and presence of 1 mM Ni2+ or Cd2+ (pH = 3.8 ± 0.1). Under acidic condition, the limited hydrolysis of metal ions resulted in their small amounts of incorporation in ferrihydrite lattices (< 0.1%), several orders of magnitude lower than those reported at neutral and alkaline pH conditions. The presence of Ni2+ or Cd2+ did not significantly affect the surface charges of either ferrihydrite pre-nucleation clusters (PNCs) or quartz surfaces. Therefore, with similar electrostatic interactions between PNCs and quartz, similar initial heterogeneous precipitation rates of pure, Ni-, and Cd- bearing ferrihydrite on quartz were observed. Later on, continuous heterogeneous nucleation and growth of ferrihydrite nanoparticles resulted in their increased polydispersity, and the size-dependent solubility of ferrihydrite nanoparticles caused the Ostwald ripening process. The presence of Ni and Cd was found to retard the recrystallization of ferrihydrite, probably due to their structural incorporation which could inhibit the dissolution of ferrihydrite. This study provided new kinetic and mechanistic insights for understanding the effects of metal ions on the heterogeneous precipitation and recrystallization processes of ferrihydrite nanoparticles on mineral surfaces, which can better predict the fate and transport of heavy metals.

  • Experiments on Condensation of Calcium Sulfide Grains to Demarcate Environments for the Formation of Enstatite Chondrites
    ACS Earth Space Chem. Pub Date : 2017-10-24
    Kaori Yokoyama, Yuki Kimura, Chihiro Kaito

    To achieve a better understanding of material evolution in the early solar system, experiments have been performed to constrain the environments in which many of the dust grains formed. Sulfur is an element whose chemical processes and mineralization of related grains are poorly understood. The high reactivity of sulfur makes it difficult to perform experiments in conventional metallic chambers, as these become heavily contaminated. Nevertheless, sulfur is expected to be a key element to understand processes in the early solar system. Here, we performed experiments on the condensation of calcium sulfide (CaS) in a glass chamber in an attempt to identify constraints on the possible formation environments of components of enstatite chondrites in terms of the effects of oxygen. Condensation experiments showed that calcium sulfate (CaSO4) or solid-solution particles of CaS and calcium oxide (CaO), i.e., [Ca(S,O)], were formed at various partial pressures of oxygen. Our results expand the range of possible conditions for the condensation of meteoritic CaS (oldhamite) from a nebula gas and extend the range of environments for the formation of the parent bodies of enstatite chondrites to include those more-oxidizing environments in the solar nebula where the atomic ratio of oxygen to sulfur was less than 6 and where CaS could have incorporated oxygen to form Ca(S,O) without formation of CaSO4.

  • Cooperative and Inhibited Adsorption of D-Ribose onto Brucite [Mg(OH)2] with Divalent Cations
    ACS Earth Space Chem. Pub Date : 2017-10-24
    Charlene Fae Estrada, Alyssa K Adcock, Dimitri A. Sverjensky, Robert M Hazen

    The adsorption and concentration of sugars onto mineral surfaces in geochemical environments, such as hydrothermal systems, may have influenced the evolution of early life on Earth. We conducted batch adsorption experiments between D-ribose and brucite [Mg(OH)2], a mineral produced from serpentinite-hosted hydrothermal systems, over variable initial ribose concentrations at four ionic strengths resulting from different Mg2+ and Ca2+ ion concentrations in the aqueous phase. Ribose adsorption generally increased with greater initial concentration, and up to 0.3 µmol•m-2 ribose attached onto brucite with 0.6 mM Mg2+ present. Ribose adsorption decreased over six-fold (4.9x10-2 µmol•m-2) when the total Mg2+ ion concentration increased to 5.8 mM. Ribose adsorption increased to 0.4 µmol•m-2 when 4.2 mM CaCl2 was added to the system. Substantial amounts (over 21 µmol•m-2) of dissolved Ca also attached to the brucite surface independent of ribose concentration. We characterized the interactions between ribose, Ca, and the brucite surface by fitting a surface complexation model to adsorption data. We propose three types of surface reactions that were consistent with the experimental data and involve 1) a bidentate outer-sphere or a “standing” ribose surface species, 2) a monodentate Ca-ribose outer-sphere species, and 3) a monodentate Ca outer-sphere species. Our model predicts brucite particle surface charge is negative at low Mg2+ concentrations and further decreases upon the addition of MgCl2, which may hinder our proposed surface complexation of the ribose species, Rib-. We predict that brucite becomes positively-charged with CaCl2 addition, which may be a consequence of the significant extent of Ca adsorption. The increase in ribose adsorption with CaCl2 is likely driven by Ca attachment and the formation of a positively-charged, cooperative Ca-ribose species that our model predicts will predominate over the “standing” ribose species on brucite. Our model of the ribose-brucite system, established by a combination of batch adsorption experiments and surface complexation modeling, has enabled predictions of ribose adsorption over a wide range of pH and complex environmental conditions.

  • Experimental Evidence for the Formation of Solvation Shells by Soluble Species at a Nonuniform Air–Ice Interface
    ACS Earth Space Chem. Pub Date : 2017-10-23
    Thorsten Bartels-Rausch, Fabrizio Orlando, Xiangrui Kong, Luca Artiglia, Markus Ammann
  • Impact of Secondary Organic Aerosol Tracers on Tracer-Based Source Apportionment of Organic Carbon and PM2.5: A Case Study in the Pearl River Delta, China
    ACS Earth Space Chem. Pub Date : 2017-10-18
    Qiongqiong Wang, Xiao He, X. H. Hilda Huang, Stephen M. Griffith, Yongming Feng, Ting Zhang, Qingyan Zhang, Dui Wu, Jian Zhen Yu
  • Crystal-chemical composition of dicoctahedral smectites: an energy-based assessment of empirical relations
    ACS Earth Space Chem. Pub Date : 2017-10-17
    Stephan Kaufhold, Alena Kremleva, Sven Krüger, Notker Roesch, Katja Emmerich, Reiner Dohrmann

    The experimental characterization of various dioctahedral smectites reveals weak correlations between the ratio of cis- and trans-vacant layer structures, the fraction of charge in the tetrahedral sheet, and the iron content. These correlations are demonstrated by two independent sample sets, examined in different laboratories, and hence are considered to be significant. To rationalize and corroborate these relations, accurate relative energies and ion exchange energies of a set of model minerals were determined by quantum chemical density functional calculations. Accordingly, one may trace these empirical correlations mainly back to energy relations and rationalize some deviating smectites by their particular history of formation.

  • Highly Time-Resolved Atmospheric Observations Using a Continuous PM2.5 and Element Monitor
    ACS Earth Space Chem. Pub Date : 2017-10-12
    Hitoshi Asano, Tomoki Aoyama, Yusuke Mizuno, Yukihide Shiraishi,

    We measured the PM2.5 and element (S, Pb, K, Si, Ca, Fe, Mn, and Zn) concentrations in March 2015 by using a continuous PM2.5 mass and element concentration monitor at Sanyo Onoda city, which is located in the western part of Japan. In addition to the PM2.5 concentration measurements, this instrument can continuously and automatically analyze the elements in the PM2.5 without sample pretreatment by using X-ray fluorescence at a high time resolution. The PM2.5 concentrations measured with our apparatus and the Yamaguchi Prefectural Government’s system had a good correlation, with a correlation coefficient of 0.931. The increase in the PM2.5 concentration in the case of the westerly wind indicates that the air mass includes a high concentration of particulate matter that is transported from the Asian continent. The anthropogenic components (S, Pb, and K) showed a strong correlation with the PM2.5. However, there was a moderate correlation between the crustal components (Si, Ca, and Fe) and the PM2.5. During a high PM2.5 concentration event, the results of the time lag in the peak between the anthropogenic components and the crustal components indicate that the distinct air masses were transported from different origins. The Pb/Zn ratio increased with the PM2.5, which might be a useful indicator for evaluating the long-range transport.

  • Impact of Secondary Organic Aerosol Tracers on Tracer-based Source Apportionment of Organic Carbon and PM2.5: A Case Study in the Pearl River Delta, China
    ACS Earth Space Chem. Pub Date : 2017-10-06
    Qiongqiong Wang, Xiao He, X. H. Hilda Huang, Stephen Miles Griffith, Yongming Feng, Ting Zhang, Qingyan Zhang, Dui Wu, Jian Zhen Yu

    Knowledge of the relative abundance of primary organic aerosol (POA) and secondary organic aerosol (SOA) forms an important scientific basis for formulating particulate matter (PM) control policies. Taking advantage of a comprehensive chemical composition data set of PM2.5 including both POA and SOA tracers (most notably SOA tracers of a few biogenic voltaic organic compound precursors), we investigate the impact of inclusion of SOA tracers on the source apportionment of organic carbon (OC) and PM2.5 in the Pearl River Delta (PRD) region of China using positive matrix factorization (PMF). In PMF runs incorporating SOA tracers (PMFw), ten PMF factors were resolved including four secondary factors: (1) SOA_I (α-pinene, β-caryophyllene and naphthalene derived SOA), (2) SOA_II (isoprene derived SOA), (3) a secondary sulfate factor, and (4) a secondary nitrate factor. In PMF tests without SOA tracers (PMFwo), the SOA_I and SOA_II factors could not be extracted while the remaining eight source factors were resolved. Among the eight common source factors, the industrial emission factor, identified by high loadings of Zn and Pb, showed the largest variations between PMFw and PMFwo solutions. The source contributions of SOA_I and SOA_II resolved in PMFw were largely shifted to the industry emission source in PMFwo. Secondary organic carbon (SOC) summed from the four secondary factors in PMFw contributed ~40% (4.47 μgC/m3) while the SOC estimate by PMFwo (3.51 μgC/m3) was 21% lower due to the inability in extracting SOA_I and SOA_II. Secondary PM2.5 by PMFwo was 6% lower than that by PMFw (23.7 vs 25.2 μg/m3). The PMFw results indicated that SOC from specific precursors may have different formation pathways than secondary sulfate and nitrate formation processes and their source contributions could not be properly resolved without the indicative tracers included in PMF. This study demonstrates the utility of biogenic SOA tracers in resolving isoprene-derived SOA and highlights the need for more SOA tracers, especially those specific to anthropogenic precursors, in improving the source apportionment for those broad OA sources such as industrial emissions.

  • Mercury Pollution in Amapá, Brazil: Mercury Amalgamation in Artisanal and Small-Scale Gold Mining or Land-Cover and Land-Use Changes?
    ACS Earth Space Chem. Pub Date : 2017-10-05
    Rebecca Adler Miserendino, Jean Remy Davée Guimarães, Gary Schudel, Sanghamitra Ghosh, José Marcus Godoy, Ellen K. Silbergeld, Peter S. J. Lees, Bridget A. Bergquist
  • Biological Impacts on Carbon Speciation and Morphology of Sea Spray Aerosol
    ACS Earth Space Chem. Pub Date : 2017-10-03
    Don Q. Pham, Rachel O’Brien, Matthew Fraund, Daniel Bonanno, Olga Laskina, Charlotte Beall, Kathryn A. Moore, Sara Forestieri, Xiaofei Wang, Christopher Lee, Camille Sultana, Vicki Grassian, Christopher D. Cappa, Kimberly A. Prather, Ryan C. Moffet
  • Impact of Intrinsic Structural Properties on the Hydration of 2:1 Layer Silicates
    ACS Earth Space Chem. Pub Date : 2017-10-03
    Florian Schnetzer, Cliff T Johnston, Gnanasiri S. Premachandra, Nicolas Giraudo, Rainer Schuhmann, Peter Thissen, Katja Emmerich

    Several 2:1 layer silicates comprising di- and trioctahedral smectites of different layer charge between 0.2 to 0.4 per formula unit and a trioctahedral vermiculite were studied by an in-situ method that allowed FTIR spectra and water vapor sorption isotherms to be obtained simultaneously. Particle size and shape of the selected materials were determined using X-ray diffraction (XRD) and gas adsorption analysis, which provided an estimate of the particle size with resulting edge site proportion. The aim of this study was to elucidate the hydration mechanism in 2:1 layer silicates during desorption and adsorption of water vapor. Domains in the de- and adsorption of water vapor of the smectite samples with a slightly increasing slope were explained by a heterogeneous layer charge distribution, which enables the coexistence of different hydration states even under controlled conditions. Whereas hysteresis was observed over the entire isothermal range of the smectites, the isotherm of the vermiculite sample only showed hysteresis in the transition from mono- (1W) to bi-hydrated state (2W). We also revealed that hysteresis is a function of the layer charge distribution, the achieved water content and the particle size with resulting edge site contribution. Increasing the edge site proportions led to an increased hysteresis. The findings from the experimental FTIR/gravimetric analysis showed that the transition from 2W to 1W and backward is visible using IR spectroscopy. The shifting of δ(H-O-H) was influenced by the layer charge and octahedral substitutions. As a final point, we use water as a sensor molecule to describe the OH groups of the octahedral sheet and show that the observed shifts result from a change in the tilting angle. Our experimental results were supported by ab initio thermodynamic simulations that revealed the different shifting behavior of δ(H-O-H) and δ(Mx+-OH-Ny+) related to the differences in surface charge density and octahedral compositions.

  • Molecular Evolution of N-Containing Cyclic Compounds in the Parent Body of the Murchison Meteorite
    ACS Earth Space Chem. Pub Date : 2017-10-02
    Hiroshi Naraoka, Yohei Yamashita, Mihoko Yamaguchi, François-Régis Orthous-Daunay
  • Experimental Evidence for the Formation of Solvation Shells by Soluble Species at a Non-Uniform Air – Ice Interface.
    ACS Earth Space Chem. Pub Date : 2017-09-29
    Thorsten Bartels-Rausch, Fabrizio Orlando, Xiangrui Kong, Luca Artiglia, Markus Ammann

    Soluble species induce surface pre-melting at the air – ice interface in the thermodynamic ice stability domain below the liquidus. This quasi-liquid layer is thought to increase in thickness with concentration of impurities and to represent a reservoir into which larger amounts of soluble species dissolve compared to a more rigid ice surface. To directly investigate the response of the quasi-liquid layer to increasing amounts of solutes and to clarify the distribution of these at the ice surface with depth, we use a combination of Auger electron yield X-ray absorption and photoelectron spectroscopies. We studied the adsorption of formic acid to ice at 251 K. These two complimentary methods allow concluding that solutes enter the air – ice interface, but do not necessarily induce a thicker quasi-liquid layer. Rather, modifications of the hydrogen bonding network seem to be linked to the formation of solvation shells and to long-range effects on the hydrogen-bonding network. We suggest that the flexibility of water molecules in the quasi-liquid layer is essential to form solvation shells and interpret the confinement of formic acid to the upper few ice bilayers to be linked with the structure of the hydrogen-bonding network getting more ice-like and rigid with depth at the air – ice interface.

  • 更新日期:2017-10-01
  • Optical Properties of Airborne Soil Organic Particles
    ACS Earth Space Chem. Pub Date : 2017-09-28
    Daniel P. Veghte, Swarup China, Johannes Weis, Libor Kovarik, Mary K. Gilles, Alexander Laskin
  • Photochemistry of Products of the Aqueous Reaction of Methylglyoxal with Ammonium Sulfate
    ACS Earth Space Chem. Pub Date : 2017-09-28
    Paige K. Aiona, Hyun Ji Lee, Renee Leslie, Peng Lin, Alexander Laskin, Julia Laskin, Sergey A. Nizkorodov
  • A Model for the Spectral Dependence of Aerosol Sunlight Absorption
    ACS Earth Space Chem. Pub Date : 2017-09-21
    August Andersson

    Sunlight-absorbing aerosols, e.g., black and brown carbon (BC and BrC), have a potentially large, but highly uncertain contribution to climate warming. The spectral dependence of the aerosol absorption in the visible and near-UV regime is almost universally well-described with a heuristic power law, where the exponent is termed the Absorption Ångström Exponent. However, the underlying physico-chemical causes for this relation are unknown. Here, a model is presented that predicts the emergence of the power law spectral dependence and unifies the absorption behavior of BC and BrC. Building on the theory of light-absorption in amorphous materials, the interaction between multiple functional groups upon absorption is predicted to be a key feature for this broad spectral dependence. This model is in agreement with recent empirical findings and provide a conceptual basis for the further research needed to better constrain the optical properties of light-absorbing aerosols and their environmental impact.

  • 更新日期:2017-09-20
  • Biological Impacts on Carbon Speciation and Morphology of Sea Spray Aerosol
    ACS Earth Space Chem. Pub Date : 2017-09-19
    Don Q. Pham, Rachel Elizabeth O'Brien, Matthew Fraund, Daniel Bonanno, Olga Laskina, Charlotte Beall, Kathryn A Moore, Sara Forestieri, Xiaofei Wang, Christopher Lee, Camille M Sultana, Vicki H. Grassian, Christopher David Cappa, Kimberly Ann Prather, Ryan C. Moffet

    Sea spray aerosol (SSA) can have complex carbon speciation that is affected by biological conditions in the seawater from which it originates. Biologically-derived molecules can also interact with other, longer-lived, organic and inorganic carbon species in the sea surface microlayer and in the process of bubble bursting. An isolated wave channel facility was used to generate sea spray aerosol during a one month mesocosm study. Two consecutive phytoplankton blooms occurred and sea spray aerosol were sampled throughout. Scanning Transmission X-Ray Microscopy coupled with Near Edge X-Ray Absorption Fine Structure (STXM-NEXAFS) spectroscopy was used to determine spatially resolved carbon speciation within individual particles from 0.18 to 3.2 µm. During phytoplankton blooms, coarse mode particles exhibited an increased abundance of carboxylic acid rich needle-like structures. The extent of organic enrichment in fine mode particles correlates with the occurrence of aliphatic-rich organic species as detected by an intense C1s→σ(C-H)* excitation. These aliphatic-rich species had a strong association with graphitic carbon, detected by a C1s→σ* exciton excitation. This enrichment was unique to particles collected in the aerodynamic size range 0.18-0.32 µm and corresponded with the decrease in hygroscopicity. Aliphatic organics can significantly suppress the particle hygroscopicity when they replace salt, thus influencing the effect sea spray aerosol has on light scattering and cloud formation. These results suggest that graphitic carbon is concentrated in the sea surface microlayer (SSML) during phytoplankton blooms and released through wave action. These results may have implications for radiative transfer and carbon cycling in the ocean-atmosphere system.

  • Mercury Pollution in Amapá, Brazil: Mercury Amalgamation in Artisanal and Small-Scale Gold Mining or Land-Cover and Land-Use Changes?
    ACS Earth Space Chem. Pub Date : 2017-09-19
    Rebecca Adler Miserendino, Jean Remy Davée Guimarães, Gary Schudel, Sanghamitra Ghosh, José Marcus Godoy, Ellen K. Silbergeld, Peter S.J. Lees, Bridget A. Bergquist

    Mercury (Hg) poses a public health burden in the Amazon and worldwide. Although usually attributed to Hg used in artisanal and small-scale gold mining (ASGM), the primary source of elevated Hg in Amazonian aquatic ecosystems is contested since there have not been tools to differentiate between Hg from ASGM and Hg from other sources such as increased soil erosion associated with land-cover and land-use change. To directly assess Hg contamination from ASGM, stable Hg isotope analyses were applied to sediment cores, surface sediments, and soils from two aquatic ecosystems in Amapá, Brazil, one downstream of ASGM activities and one isolated from ASGM. Downstream of the ASGM sites, the Hg isotope data is consistent with elevated Hg coming dominantly from increased erosion of soils and not from Hg used during gold extraction. Although these two sources represent different pathways of contamination to downstream ecosystems, ASGM may contribute to both land-cover and land-use change and local contamination of soils. Accordingly, these findings demonstrate that in some regions of the Amazon effective Hg mitigation strategies need to address land-use practices in addition to ASGM.

  • Effects of Pressure on Model Compounds of Meteorite Organic Matter
    ACS Earth Space Chem. Pub Date : 2017-09-13
    Christian Potiszil, Wren Montgomery, Mark A. Sephton
  • Optical Properties of Airborne Soil Organic Particles
    ACS Earth Space Chem. Pub Date : 2017-09-08
    Daniel P. Veghte, Swarup China, Johannes Weis, Libor Kovarik, Mary K. Gilles, Alexander Laskin

    The impact of water droplets on soils has recently been found to drive emissions of airborne soil organic particles (ASOP). The Chemical composition of ASOP include macromolecules such as polysaccharides, tannins, and lignin (derived from degradation of plants and biological organisms), which determine light absorbing (brown carbon) particle properties. Optical properties of ASOP were inferred from the quantitative analysis of the electron energy-loss spectra acquired over individual particles using transmission electron microscopy. The optical constants of ASOP are compared with those measured for laboratory generated particles composed of Suwanee River Fulvic Acid (SRFA) reference material, which is used as a laboratory surrogate of ASOP. The chemical composition of the particles was analyzed using energy dispersive x-ray spectroscopy, electron energy-loss spectroscopy, and synchrotron-based scanning transmission x-ray microscopy with near edge x-ray absorption fine structure spectroscopy. ASOP and SRFA exhibit similar carbon composition, with minor differences in other elements present. When ASOP are heated to 350 °C their absorption increases as a result of pyrolysis and partial volatilization of semi-volatile organic constituents. The retrieved refractive index (RI) at 532 nm of SRFA particles, ASOP, and heated ASOP were 1.22-0.07i, 1.29-0.07i, and 1.90-0.38i, respectively. Retrieved imaginary part of the refractive index of SRFA particles derived from EELS measurements was higher and the real part was lower compared to data from more common optical methods. Therefore, corrections to the EELS data are needed for incorporation into models. These measurements of ASOP optical constants confirm that they have properties characteristic of atmospheric brown carbon and therefore their potential effects on the radiative forcing of climate need to be assessed in atmospheric models.

  • Efficient Thermal Reactions of Sulfur Dioxide on Ice Surfaces at Low Temperature: A Combined Experimental and Theoretical Study
    ACS Earth Space Chem. Pub Date : 2017-09-06
    Jaehyeock Bang, Mahbubul Alam Shoaib, Cheol Ho Choi, Heon Kang

    The interaction of sulfur dioxide (SO2) gas with a crystalline ice surface at low temperature was studied by analyzing the surface species with low energy sputtering (LES) and reactive ion scattering methods, and the desorbing gases with temperature-programmed desorption mass spectrometry. The study gives direct evidence for the occurrence of efficient hydrolysis of SO2 with low energy barriers on the ice surface. Adsorbed SO2 molecules react with the ice surface at temperatures above ~90 K to form anionic molecular species, which were detected by OH–, SO2–, and HSO3– emission signals in the LES experiments. Heating the sample above ~120 K causes the desorption of SO2 gas from the surface-bound hydrolysis products. As a result, the hydrolysis of SO2 on an ice surface is most efficient at 100–120 K. The surface products formed at these temperatures correspond to metastable states, which are kinetically isolated on the cold surface. Quantum mechanical calculations of a model ice system suggest plausible mechanistic pathways for how physisorbed SO2 is transformed into chemisorbed HSO3– species. HSO3– is formed either by direct conversion of physisorbed SO2 or through the formation of a stable H2SO3 surface complex, both involving proton transfers on the ice surface with low energy barriers. These findings suggest the possibility that thermal reactions of SO2 occur efficiently on the ice surface of Jovian satellites, even without bombardment by high-energy radiation.

  • Photochemistry of Products of the Aqueous Reaction of Methylglyoxal with Ammonium Sulfate
    ACS Earth Space Chem. Pub Date : 2017-09-01
    Paige K Aiona, Hyun Ji (Julie) Lee, Renee Leslie, Peng Lin, Alexander Laskin, Julia Laskin, Sergey A. Nizkorodov

    Aqueous reactions of methyl glyoxal (MG) and glyoxal with ammonium sulfate (AS) produce light-absorbing compounds (chromophores) and may serve as a source of atmospheric secondary “brown carbon” (BrC). The molecular composition of these chromophores is ambiguous and their transformation due to exposure to solar UV radiation is not well understood. We examined the molecular composition, mass absorption coefficients, and fluorescence spectra of BrC samples produced by the evaporation of aqueous MG/AS solutions. Chromatograms of BrC produced by evaporation were different from those of BrC produced by slow MG/AS reaction in water, highlighting the substantial sensitivity of BrC to its formation conditions. The BrC samples were characterized before and after their exposure to broadband (270-390 nm) UV radiation. Irradiation led to rapid photobleaching, a decrease in the characteristic 280 nm absorption band, a complete loss of fluorescence, and a dramatic change in molecular composition. By comparing the composition before and after the irradiation, we identified several structural motifs that may contribute to the light absorbing properties of MG/AS BrC. For example, a family of oligomers built from an imidazole carbonyl and repetitive MG units was prominent in the initial sample, and decreased in abundance after photolysis. More complex oligomers containing both imidazole and pyrrole rings in their structures also appeared to contribute to the pool of BrC chromophores. The selective reduction of carbonyl functional groups by sodium borohydride diminished the absorption, but had little effect on the fluorescence of MG/AS BrC samples, suggesting that absorption in this system is dominated by individual chromophores as opposed to supramolecular charge-transfer complexes. Due to the efficient photolysis of the BrC chromophores, this MG/AS BrC system has limited impact on the direct radiative forcing of climate, but may have an effect on atmospheric photochemistry in aerosol particles.

  • The Effects of Pressure on Model Compounds of Meteorite Organic Matter.
    ACS Earth Space Chem. Pub Date : 2017-08-28
    Christian Potiszil, Wren Montgomery, Mark A. Sephton

    Extraterrestrial organic matter has been widely studied; however, its response to pressure has not. Primitive organic matter bearing meteorites, such as CI and CM carbonaceous chondrites, have experienced variable pressures, up to 10 GPa. To appreciate the effects of these pressures on the organic content of these bodies, the model compounds isophthalic acid, vanillin and vanillic acid were subjected to pressures of up to 11.5 GPa and subsequently decompressed. High resolution synchrotron source Fourier Transform Infrared (FTIR) was used to determine the effects of different benzene substituents at high pressure on both the vibrational assignments of the benzene core of the molecules and the ability of the aromatic compounds to form intermolecular hydrogen bonds. The presence of additional peaks at high pressure was found to coincide with molecules that contain carboxyl groups, these features are interpreted as C-H---O intermolecular hydrogen bonds. The formation of these hydrogen bonds has implications for the origination of macromolecular organic matter (MOM), owing to the importance of such attractive forces during episodes of cross linking, such as esterification. Pressure-induced hydrogen bond formation is a process by which aromatic MOM precursors could have cross linked to generate the organic polymers found within extraterrestrial bodies today.

  • High Abundance of Fluorescent Biological Aerosol Particles in Winter in Beijing, China
    ACS Earth Space Chem. Pub Date : 2017-08-25
    Siyao Yue, Hong Ren, Songyun Fan, Lianfang Wei, Jian Zhao, Mengying Bao, Shengjie Hou, Jianqiong Zhan, Wanyu Zhao, Lujie Ren, Mingjie Kang, Linjie Li, Yanlin Zhang, Yele Sun, Zifa Wang, Pingqing Fu
  • Fluid-Enhanced Coarsening of Mineral Microstructures in Hydrothermally Synthesized Bornite–Digenite Solid Solution
    ACS Earth Space Chem. Pub Date : 2017-08-23
    Jing Zhao, Joël Brugger, Benjamin A. Grguric, Yung Ngothai, Allan Pring
  • Microscopic and Spectroscopic Insights into Uranium Phosphate Mineral Precipitated by Bacillus Mucilaginosus
    ACS Earth Space Chem. Pub Date : 2017-08-22
    Wenbo Huang, Wencai Cheng, Xiaoqin Nie, Faqin Dong, Congcong Ding, Mingxue Liu, Zheng Li, Tasawar Hayat, Njud S. Alharbi
  • Thermodynamic Constraints on the Lower Atmosphere of Venus
    ACS Earth Space Chem. Pub Date : 2017-08-21
    Nathan S. Jacobson, Michael Kulis, Brandon Radoman-Shaw, Ralph Harvey, Dwight L. Myers, Laura Schaefer, Bruce Fegley
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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