scholarly journals Mass Transport of Condensed Species in Aerodynamic Fallout Glass from a Near-Surface Nuclear Test

2016 ◽  
Author(s):  
D Weisz
Keyword(s):  
Mass Transport ◽  
Nuclear Test ◽  
Near Surface ◽  
Condensed Species

scholarly journals Diffusive mass transport in agglomerated glassy fallout from a near-surface nuclear test

2018 ◽  
Vol 223 ◽  
pp. 377-388 ◽  
Author(s):  
David G. Weisz ◽  
Benjamin Jacobsen ◽  
Naomi E. Marks ◽  
Kim B. Knight ◽  
Brett H. Isselhardt ◽  
...  
Keyword(s):  
Mass Transport ◽  
Nuclear Test ◽  
Near Surface

Kinetic Studies of Adsorption-Desorption of Cd and Zn Onto Al2O3/Solution Interfaces

1993 ◽  
Vol 28 (7) ◽  
pp. 39-45 ◽  
Author(s):  
K. S. L. Lo ◽  
J. O. Leckie
Keyword(s):  
Mass Transfer ◽  
Mass Transport ◽  
Metal Ion ◽  
Internal Diffusion ◽  
Internal Mass ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Near Surface ◽  
Film Diffusion ◽  
Slow Stage

The effects of external and internal mass transport limitations on zinc and cadmium adsorption onto the porous amorphous aluminium oxide/solution interfaces were studied. A modified two-stage rate model was used to interpret the experimental results. The rapid stage results from external surface film diffusion and internal diffusion into the near surface pores. The slow stage results from internal mass transport and extends over several days. The mass transfer-adsorption coefficients of the rapid stage are almost two orders of magnitude larger than those of the slow stage. The external mass transfer coefficients show an increasing trend with increasing pH, and appear to be affected by the charge/potential condition of the oxide/solution interface. The internal mass transfer coefficients indicate a uniform trend for both the zinc and cadmium results. The desorption rates and final metal ion solution concentrations are affected by the bulk solution pH. Film diffusion and internal diffusion are affected by the higher relative ratio of metal ion concentration to adsorbent concentration.

Characterizing major and trace element compositions in fallout melt glass from a near-surface nuclear test

2022 ◽  
Vol 243 ◽  
pp. 106796
Author(s):  
Josh Wimpenny ◽  
Gary R. Eppich ◽  
Naomi Marks ◽  
Frederick Ryerson ◽  
Kim B. Knight
Keyword(s):  
Trace Element ◽  
Nuclear Test ◽  
Near Surface ◽  
Melt Glass

scholarly journals Deposition of vaporized species onto glassy fallout from a near-surface nuclear test

2017 ◽  
Vol 201 ◽  
pp. 410-426 ◽  
Author(s):  
David G. Weisz ◽  
Benjamin Jacobsen ◽  
Naomi E. Marks ◽  
Kim B. Knight ◽  
Brett H. Isselhardt ◽  
...  
Keyword(s):  
Nuclear Test ◽  
Near Surface

Mg Implantation and Characterization of Sapphire Surfaces

1986 ◽  
Vol 74 ◽  
Author(s):  
A. P. Jardine ◽  
S. Mitra Mukhopadhyay ◽  
J. M. Blakely
Keyword(s):  
Mass Transport ◽  
Decay Rate ◽  
Surface Segregation ◽  
Bulk Diffusion ◽  
Near Surface ◽  
Surface Mass ◽  
Surface Mass Transport ◽  
Crystal Wafer ◽  
Mg Doped

AbstractMg ion-implantation of A12O3 wafers followed by air annealing at high temperatures was investigated as a way to provide bulk doped samples for studies of Mg surface segregation and its effect on surface mass transport. SIMS was used to analyse Mg concentrations in implanted and unimplanted near-surface regions and in the bulk. It was found that the concentration of Mg decreases dramatically with depth from both surfaces of an annealed wafer and is also observed in the bulk. These observations are attributed to bulk diffusion of the Mg combined with equilibrium surface segregation. Surface mass transport associated with the (1120) surface of an A12 O3 single crystal wafer doped and equilibrated by such a method was studied by the grating decay method; the Mg doped sample showed a decay rate in air higher than that in the undoped wafer by a factor of ∼ 2.4 at 1500°C.

scholarly journals Year-round record of near-surface ozone and O<sub>3</sub> enhancement events (OEEs) at Dome A, East Antarctica

2020 ◽  
Vol 12 (4) ◽  
pp. 3529-3544
Author(s):  
Minghu Ding ◽  
Biao Tian ◽  
Michael C. B. Ashley ◽  
Davide Putero ◽  
Zhenxi Zhu ◽  
...  
Keyword(s):  
Mass Transport ◽  
Trajectory Analysis ◽  
Back Trajectory ◽  
Synoptic Scale ◽  
Dome A ◽  
Near Surface ◽  
Air Mass ◽  
Atmospheric Processes ◽  
Back Trajectory Analysis ◽  
Stratospheric Intrusion

Abstract. Dome A, the summit of the East Antarctic Ice Sheet, is an area challenging to access and is one of the harshest environments on Earth. Up until recently, long-term automated observations from Dome A (DA) were only possible with very low power instruments such as a basic meteorological station. To evaluate the characteristics of near-surface O3, continuous observations were carried out in 2016. Together with observations at the Amundsen–Scott Station (South Pole – SP) and Zhongshan Station (ZS, on the southeast coast of Prydz Bay), the seasonal and diurnal O3 variabilities were investigated. The results showed different patterns between coastal and inland Antarctic areas that were characterized by high concentrations in cold seasons and at night. The annual mean values at the three stations (DA, SP and ZS) were 29.2±7.5, 29.9±5.0 and 24.1±5.8 ppb, respectively. We investigated the effect of specific atmospheric processes on near-surface summer O3 variability, when O3 enhancement events (OEEs) are systematically observed at DA (average monthly frequency peaking at up to 64.5 % in December). As deduced by a statistical selection methodology, these O3 enhancement events (OEEs) are affected by significant interannual variability, both in their average O3 values and in their frequency. To explain part of this variability, we analyzed the OEEs as a function of specific atmospheric processes: (i) the role of synoptic-scale air mass transport over the Antarctic Plateau was explored using the Lagrangian back-trajectory analysis Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) method, and (ii) the occurrence of “deep” stratospheric intrusion events was investigated using the Lagrangian tool STEFLUX. The specific atmospheric processes, including synoptic-scale air mass transport, were analyzed by the HYSPLIT back-trajectory analysis and the potential source contribution function (PSCF) model. Short-range transport accounted for the O3 enhancement events (OEEs) during summer at DA, rather than efficient local production, which is consistent with previous studies of inland Antarctica. Moreover, the identification of recent (i.e., 4 d old) stratospheric-intrusion events by STEFLUX suggested that deep events only had a minor influence (up to 1.1 % of the period, in August) on deep events during the variability in near-surface summer O3 at DA. The deep events during the polar night were significantly higher than those during the polar day. This work provides unique data on ozone variation at DA and expands our knowledge of such events in Antarctica. Data are available at https://doi.org/10.5281/zenodo.3923517 (Ding and Tian, 2020).

Reviews on Modeling of Diffusion-Induced Mass Transportation in Functionally Graded Cemented Carbides

2018 ◽  
Vol 15 ◽  
pp. 65-96
Author(s):  
Kai Ming Cheng ◽  
Ji Xue Zhou ◽  
Hui Xia Xu ◽  
Li Jun Zhang ◽  
Yong Du
Keyword(s):  
Mass Transport ◽  
Functionally Graded ◽  
Cemented Carbide ◽  
Key Factors ◽  
Near Surface ◽  
Diffusion Controlled ◽  
Gradient Microstructure ◽  
Different Dimensions ◽  
Formation Section ◽  
Main Factor

Graded sintering is the fundamental process of fabricating functionally gradient cemented carbide (FGCC). The diffusion-induced mass transport in cemented carbide can result in the formation of gradient microstructure and thusly lead to gradual changes in micro property. So far, several types of FGCC have been developed, and the factors that can influence the gradient formation are complex. Section 2 introduces the process of forming diffusion-controlled near-surface layer in WC-Ti (C,N)-Co hardmetal as well as the kinetic modeling work that reveals the key factors for the layer formation. Section 3 reviews the dual properties carbide produced under carburization atmosphere, for which the carbon content is a main factor of the gradient thickness. There are two models describing this process, representing different mass-transport mechanism of the so-called liquid phase migration (LPM) process. In section 4, previous and new results of modeling LPM in different dimensions and scales are presented, and the diffusion-controlled nature of LPM are discussed.

scholarly journals Year-round record of near-surface ozone and “O<sub>3</sub> enhancement events” (OEEs) at Dome A ,East Antarctica

2020 ◽  
Author(s):  
Minghu Ding ◽  
Biao Tian ◽  
Michael C. B. Ashley ◽  
Davide Putero ◽  
Zhenxi Zhu ◽  
...  
Keyword(s):  
Mass Transport ◽  
Trajectory Analysis ◽  
Surface Ozone ◽  
Back Trajectory ◽  
Synoptic Scale ◽  
Dome A ◽  
Near Surface ◽  
Air Mass ◽  
Atmospheric Processes ◽  
Back Trajectory Analysis

Abstract. Dome A, the summit of the east Antarctic Ice Sheet, is an area challenging to access and is one of the harshest environments on Earth. Up until recently, long term automated observations from Dome A were only possible with very low power instruments such as a basic meteorological station. To evaluate the characteristics of near-surface O3, continuous observations were carried out in 2016. Together with observations at the Amundsen-Scott Station (South Pole – SP) and Zhongshan Station (ZS, on the southeast coast of Prydz Bay), the seasonal and diurnal O3 variabilities were investigated. The results showed different patterns between coastal and inland Antarctic areas that were characterized by high concentrations in cold seasons and at night. The annual mean values at the three stations (DA, SP and ZS) were 29.2 ± 7.5 ppb, 29.9 ± 5.0 ppb and 24.1 ± 5.8 ppb, respectively. We investigated the effect of specific atmospheric processes on near-surface summer O3 variability, when O3 enhancement events (OEEs) are systematically observed at DA (average monthly frequency peaking up to 64.5 % in December). As deduced by a statistical selection methodology, these O3 enhancement events (OEEs) are affected by a significant interannual variability, both in their average O3 values and in their frequency. To explain part of this variability, we analyzed the OEEs as a function of specific atmospheric processes: (i) the role of synoptic-scale air mass transport over the Antarctic Plateau was explored using the Lagrangian back-trajectory analysis – Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) method and (ii) the occurrence of “deep” stratospheric intrusion events was investigated using the Lagrangian tool STEFLUX. The specific atmospheric processes, including synoptic-scale air mass transport, were analysed by the HYSPLIT back-trajectory analysis and the potential source contribution function (PSCF) model. Short-range transport accounted for the O3 enhancement events (OEEs) during summer at DA, rather than efficient local production, which is consistent with previous studies of inland Antarctica. Moreover, the identification of recent (i.e., 4-day old) stratospheric intrusions events by STEFLUX suggested that “deep” events only had a minor influence (up to 1.1 % of the period, in August) on “deep” events during the variability of near-surface summer O3 at DA. The "deep" events during the polar night were significantly higher than those during the polar day. This work provides unique information on ozone variation at DA and expands our knowledge of such events in Antarctica. Data are available at https://doi.org/10.5281/zenodo.3923517 (Ding et al., 2020).

¡Cuba! New Chemical and physical denudation rates define source-to-sink mass transport and anthropogenic impacts on nutrient loads for the largest Caribbean nation

2020 ◽  
Author(s):  
Paul Bierman ◽  
Mae Kate Campbell1 ◽  
Amanda Schmidt ◽  
Rita Sibello Hernández ◽  
Alejandro García Moya ◽  
...  
Keyword(s):  
Mass Transport ◽  
River Water ◽  
Geochemical Data ◽  
Drainage Basins ◽  
Near Surface ◽  
Erosion Rates ◽  
Denudation Rates ◽  
Source To Sink ◽  
The Impact

&lt;p&gt;Measurements of chemical and physical rates of landscape change in the tropics are rare. To address this data gap, a joint US/Cuban science team has worked together for two years sampling across the island of Cuba. Here, we report long-term cosmogenic erosion rates inferred from river sand paired with rates of chemical denudation estimated from river water solute loads. Together, these data define source-to-sink mass transport in 45 drainage basins in western and central Cuba and allow us to speculate on the role of agriculture on nutrient and sediment fluxes.&lt;/p&gt;&lt;p&gt;Rates of erosion determined from in situ &lt;sup&gt;10&lt;/sup&gt;Be concentrations range from &lt;2 to ~80 m/My, are more varied in central than western Cuba, and do not correlate with chemical denudation rates. Comparison of cosmogenic erosion rates and sediment loads measured during the peak of industrial agriculture (1970s) suggests a modest increase in sediment yield likely reflecting intensive cultivation. Chemical denudation rates (n = 45) range from 42 to 302 tons/(km&lt;sup&gt;2&lt;/sup&gt; yr) in central Cuba and from 11 to 125 tons/(km&lt;sup&gt;2&lt;/sup&gt; yr) in western Cuba.&amp;#160; Chemical denudation rates and total dissolved solids are several times higher in central Cuba than western Cuba. River water is dominated by Mg, Ca, Na, K, and Si in both areas.&lt;/p&gt;&lt;p&gt;Although cosmogenic erosion rates are often interpreted as total landscape denudation, we find in some Cuban drainage basins that&amp;#160;&lt;sup&gt;10&lt;/sup&gt;Be-based erosion rates underestimate total landscape denudation. Considerable discordance (12-60X) between erosion rates and chemical denudation rates in five central Cuban basins suggests that significant mass loss by solution is not reflected by cosmogenic-based erosion rates. In 2 of these basins, erosion rates calculated from duplicate measurements of&amp;#160;&lt;sup&gt;10&lt;/sup&gt;Be (1.4 &amp; 2.5 m/My) and&amp;#160;&lt;sup&gt;26&lt;/sup&gt;Al (1.7 &amp; 2.9 m/My) were ~50X lower than chemical denudation rates (89 &amp; 108 m/My). Both&amp;#160;&lt;sup&gt;26&lt;/sup&gt;Al and&amp;#160;&lt;sup&gt;10&lt;/sup&gt;Be concentrations indicate long term, near-surface (&gt;&gt;100 ky) quartz residence; stream water geochemical data are consistent with the presence of evaporite deposits. We suspect that rapid chemical denudation enriches basin sediment in quartz, which lingers at or near the surface in these low slope (0.5&amp;#176;) basins.&lt;/p&gt;&lt;p&gt;Despite centuries of agriculture, the impact on Cuban river biogeochemistry is limited. Although river water in many central Cuban rivers has high levels of E. coli bacteria, likely sourced from livestock, concentrations of nitrate are far lower than other areas where intensive agriculture is practiced, such as the Mississippi River Basin. This suggests the benefits of Cuba&amp;#8217;s shift to conservation agriculture after 1990 and provides a model for more sustainable agriculture worldwide.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

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