scholarly journals Mechanical Behavior and Constitutive Model for Loess Samples under Simulated Acid Rain Conditions

2021 ◽  
Author(s):  
xia ye ◽  
Enlong Liu ◽  
Baofeng Di ◽  
yayang yu
Keyword(s):  
Mechanical Properties ◽  
Acid Rain ◽  
Mechanical Model ◽  
Ph Value ◽  
Simulated Acid Rain ◽  
Test Results ◽  
Hardening Model ◽  
Ph Values ◽  
Scanning Electron ◽  
Peak Value

Abstract In this paper, the sulfuric acid solution is diluted to pH 5.0, 4.0 and 3.0 to simulate the acid rain condition, and the triaxial compressional tests and scanning electron microscope are carried out to study the mechanical properties and evolution of the microstructure of the saturated loess samples. The results demonstrate that acid rain increases the porosity of loess samples, and the pore distribution is not uniform, so that the mechanical properties of loess samples change. With the decrease of pH value, the peak value of the deviatoric stress and the volumetric contraction of loess samples decreases, which causes the strength of soil to decrease. Furthermore, the framework of the chemical-mechanical model for loess under the action of acid rain is established, in which the loess is considered as porous medium material, and the variable of acid rain at different pH values through the degree of chemical reaction is taken into account in the double-hardening model, and the model is also verified by the triaxial test results finally.

scholarly journals Role of Charge Regulation and Fluctuations in the Conformational and Mechanical Properties of Weak Flexible Polyelectrolytes

2019 ◽  
Author(s):  
Pablo M. Blanco ◽  
Sergio Madurga ◽  
Claudio F. Narambuena ◽  
Francesc Mas ◽  
Josep L. Garcés
Keyword(s):  
Mechanical Properties ◽  
Electrostatic Interactions ◽  
Ph Value ◽  
Persistence Length ◽  
Excluded Volume ◽  
Average Charge ◽  
Zero Force ◽  
Charge Regulation ◽  
Ph Values

This work addresses the role of charge regulation (CR) and the associated fluctuations in the conformational and mechanical properties of weak polyelectrolytes. Due to CR, changes in the pH-value modifies the average macromolecular charge and conformational equilibria. A second effect is that, for a given average charge per site, fluctuations can alter the intensity of the interactions by means of correlation between binding sites. We investigate both effects by means of Monte Carlo simulations at constant pH-value, so that the charge is a fluctuating quantity. Once the average charge per site is available, we turn off the fluctuations by assigning the same average charge to every site. A constant charge MC simulation is then performed. We make use of a model which accounts for the main fundamental aspects of a linear flexible polyelectrolyte i.e. proton binding, angle internal rotation, bond stretching and bending. Steric excluded volume and differentiated treatment for short-range and long-range interactions are also included in the model. It can be regarded as a kind of "minimal'' model in the sense that contains a minimum number of parameters but still preserving the atomistic detail. It is shown that, if fluctuations are activated, gauche state bond probabilities increase, and the persistence length decreases, so that the polymer becomes more folded. Macromolecular stretching is also analyzed in presence of CR (the charge depends on the applied force) and without CR (the charge is fixed to the value at zero force). The analysis of the low force scaling behavior concludes that Pincus exponent becomes pH-dependent. Both with and without CR, a transition from 1/2 at high pH-values (phantom chain) to 3/5 to low pH-values (Pincus regime), is observed. Finally, the intermediate force stretching regime is investigated. It is found that CR induces a moderate influence in the force-extension curves and persistence length (which in this force regime becomes force-dependent). It is thus concluded that the effect of CR on the stretching curves is mainly due to changes in the average charge at zero force. It is also found that, for the cases studied, the effect of steric excluded volume is almost irrelevant compared to electrostatic interactions.

Influence of simulated acid rain on the flowering dogwood (Cornusflorida) leaf surface

1994 ◽  
Vol 24 (5) ◽  
pp. 1058-1062 ◽  
Author(s):  
Daniel A. Brown ◽  
Mark T. Windham ◽  
Robert L. Anderson ◽  
Robert N. Trigiano
Keyword(s):  
United States ◽  
Acid Rain ◽  
Leaf Surface ◽  
Simulated Acid Rain ◽  
Eastern United States ◽  
Flowering Dogwood ◽  
Simulated Rain ◽  
Decreasing Ph ◽  
One Year ◽  
Scanning Electron

Acidic rainfall has the potential to influence anthracnose incidence and severity in flowering dogwood (Cornusflorida L.) of the eastern United States. One-year-old, nursery-grown flowering dogwood seedlings were exposed to 1 cm of simulated rain 10 times over a 42-day period in 1990. Simulated rains were composed of a mixture of salts typical of ambient rainfall in the eastern United States and pH was adjusted to 5.5, 4.5, 3.5, and 2.5 with sulfuric and nitric acids. Samples were cut from the leaf tip, margin, and midvein of rain-treated trees and prepared for scanning electron microscopy. Cuticular cracking, desiccation, and erosion of trichome surfaces was observed in response to acid rain treatment. Increased degradation of dogwood trichomes was observed with decreasing pH for all samples. Cuticular erosion due to acid rain has the potential to predispose dogwoods in the eastern United States to anthracnose caused by Disculadestructiva sp.nov. (Red.) and an unnamed Discula sp.

Effect of VC and C Addition on Mechanical Properties and Microstructures of WC-Co Hardmetals Processed in Nitrogen-Based Atmosphere

2012 ◽  
Vol 59 (2) ◽  
Author(s):  
R. J. Talib ◽  
A. A. Mahaidin ◽  
S. A. Manaf ◽  
M. A. Selamat
Keyword(s):  
Mechanical Properties ◽  
Electron Microscope ◽  
Powder Metallurgy ◽  
Test Results ◽  
Powder Metallurgy Technique ◽  
Dense Structure ◽  
Mixed Powder ◽  
Vicker’S Microhardness ◽  
Scanning Electron ◽  
Microhardness Tester

The WC-Co, WC-Co-VC and WC-Co-C samples are fabricated using powder metallurgy technique. The mixed powder is compacted under the pressure of 625 MPa, cold-isostatic pressed at 200 MPa and sintered at temperature in the range of 1350 – 1450°C nitrogen-based atmosphere. The mechanical properties of the samples are analyzed using Vicker’s microhardness tester, universal tensile machine and scanning electron microscope. Test results reveal that WC-Co-C sample has better mechanical properties as compared to WC-Co and WC-Co-VC due to the formation of homogeneous and dense structure.

scholarly journals Role of Charge Regulation and Fluctuations in the Conformational and Mechanical Properties of Weak Flexible Polyelectrolytes

Polymers ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 1962 ◽  
Author(s):  
Pablo M. Blanco ◽  
Sergio Madurga ◽  
Claudio F. Narambuena ◽  
Francesc Mas ◽  
Josep L. Garcés
Keyword(s):  
Mechanical Properties ◽  
Electrostatic Interactions ◽  
Ph Value ◽  
Persistence Length ◽  
Excluded Volume ◽  
Average Charge ◽  
Zero Force ◽  
Charge Regulation ◽  
Ph Values

This work addresses the role of charge regulation (CR) and the associated fluctuations in the conformational and mechanical properties of weak polyelectrolytes. Due to CR, changes in the pH-value modifies the average macromolecular charge and conformational equilibria. A second effect is that, for a given average charge per site, fluctuations can alter the intensity of the interactions by means of correlation between binding sites. We investigate both effects by means of Monte Carlo simulations at constant pH-value, so that the charge is a fluctuating quantity. Once the average charge per site is available, we turn off the fluctuations by assigning the same average charge to every site. A constant charge MC simulation is then performed. We make use of a model which accounts for the main fundamental aspects of a linear flexible polyelectrolyte that is, proton binding, angle internal rotation, bond stretching and bending. Steric excluded volume and differentiated treatment for short-range and long-range interactions are also included. This model can be regarded as a kind of “minimal” in the sense that it contains a minimum number of parameters but still preserving the atomistic detail. It is shown that, if fluctuations are activated, gauche state bond probabilities increase and the persistence length decreases, so that the polymer becomes more folded. Macromolecular stretching is also analyzed in presence of CR (the charge depends on the applied force) and without CR (the charge is fixed to the value at zero force). The analysis of the low force scaling behavior concludes that Pincus exponent becomes pH-dependent. Both, with and without CR, a transition from 1/2 at high pH-values (phantom chain) to 3/5 at low pH-values (Pincus regime) is observed. Finally, the intermediate force stretching regime is investigated. It is found that CR induces a moderate influence in the force-extension curves and persistence length (which in this force regime becomes force-dependent). It is thus concluded that the effect of CR on the stretching curves is mainly due to the changes in the average charge at zero force. It is also found that, for the cases studied, the effect of steric excluded volume is almost irrelevant compared to electrostatic interactions.

Study of Electrochemical Behavior of the Transmission Tower Galvanized Layer in Simulated Acid Rain Solution

2013 ◽  
Vol 361-363 ◽  
pp. 1042-1045
Author(s):  
Hua Ling Deng ◽  
Qi Lei Sun
Keyword(s):  
Acid Rain ◽  
Electrochemical Behavior ◽  
Electrochemical Impedance ◽  
Ph Value ◽  
Low Ph ◽  
Simulated Acid Rain ◽  
Corrosion Products ◽  
Precipitation Process ◽  
Layer Surface ◽  
Transmission Tower

Using electrochemical impedance spectroscopy (EIS), polarization curve and X-ray diffraction technique, electrochemical behavior of the transmission tower material Q460 galvanized layer was studied in simulated acid rain solution. The results show that: galvanized layers take place local corrosion in simulated acid rain solution, the corrosion products will fill the hole, and cover on galvanized layer surface, the generated white corrosion products mainly ZnSO4 ·H2O.The current generate in the process of corrosion, galvanized layer surface take place electrochemical corrosion. Galvanized layer solution at pH 2.4 and 3.8 of the simulated acid rain in the corrosion process is controlled by the charge transfer process, with the decrease of solution pH value, the corrosion rate increases. Zinc are more sensitive to H+ in the solution, in low pH value of solution, due to the strong hydrogen precipitation process, the zinc surface adsorption of hydrogen bubble around, its dissolution rate is higher than the surface of the other part of the zinc, namely in low pH value of acid rain solution, H+ by depolarization process not only directly accelerate the corrosion of zinc, can through the strong hydrogen evolution process at the same time accelerate the dissolution of zinc.

Short-term acid damage to photosynthesis in corn and sugar maple leaves assessed by photoacoustic spectroscopy

1990 ◽  
Vol 68 (10) ◽  
pp. 2292-2300 ◽  
Author(s):  
C. N. N'soukpoé-Kossi ◽  
R. Bélanger ◽  
S. Keilani ◽  
H. Proteau ◽  
P. Boivin ◽  
...  
Keyword(s):  
Growth Rate ◽  
Acid Rain ◽  
Oxygen Evolution ◽  
Photoacoustic Spectroscopy ◽  
Sugar Maple ◽  
Photosynthetic Activity ◽  
Simulated Acid Rain ◽  
Acid Mixture ◽  
Photosynthetic Oxygen Evolution ◽  
Ph Values

Photoacoustic spectroscopy was used to monitor acid damage to photosynthesis by measuring photosynthetic O2 evolution in leaves from com and sugar maple plantlets. For 2 months the seedlings were treated with simulated acid rain either by spraying the leaves or by watering the soil at different pH levels. The results indicated a decline of photosynthetic oxygen evolution as the pH of the foliar application of simulated acid rain decreased. The reduced photosynthetic activity was sometimes followed by depigmentation (below pH 3.5). For plantlets treated by watering the soil with an acid mixture, the results showed an increase in the growth rate at higher acidity levels without effect on the photosynthetic activity. All corn seedlings from seeds that germinated in media of different pH levels showed the same photosynthetic activity regardless of the pH, as measured by photoacoustic spectroscopy, but the growth rate was higher at lower pH values than at higher pH values. These results clearly indicate the importance of acid damage to photosynthesis at the foliar level, and the ability of photoacoustic spectroscopy to assess forest decline in its early stages. Key words: photoacoustic spectroscopy, photosynthesis, corn, maple, acid rain, oxygen evolution.

Evaluation of the Influence of Acid Rain on the Property of Plant Mediums by Simulation

2011 ◽  
Vol 236-238 ◽  
pp. 2997-3000
Author(s):  
Jia Horng Lin ◽  
Jin Mao Chen ◽  
Ching Wen Lin ◽  
Wen Hao Hsing ◽  
Chen Fang Tsai ◽  
...  
Keyword(s):  
Acid Rain ◽  
Ph Value ◽  
Cotton Fibers ◽  
Ph Values ◽  
Weight Losses ◽  
Suitable Environment

Acid rain has drawn much attention recently. This study was about evaluating the acid-rain-resistant and eco wall which was made of cotton fibers and Tencel fibers. In the experiment, two types of fibers were immersed in stimulated-acid-rain solutions for a week and weighted respectively after drying. This same procedure was repeated weekly three times; meanwhile, the fibers’ pH values were measured daily. The result showed that cotton fibers surpassed Tencel fibers, demonstrating smaller weight losses and positive pH results. The cotton fibers were able to adjust its pH value to 6.8, which provided a suitable environment for plants.

scholarly journals Growth and Leaf Chlorophyll Content of Eucalyptus grandis W. Hill ex Maiden are Adversely Affected by Simulated Acid Rain

2020 ◽  
pp. 8-15
Author(s):  
Langmi Fabrice Buma ◽  
Titus Fondo Ambebe ◽  
Zephania Nji Fogwe
Keyword(s):  
Acid Rain ◽  
Chlorophyll Content ◽  
Tap Water ◽  
Harmful Effect ◽  
Eucalyptus Grandis ◽  
Simulated Acid Rain ◽  
Total Biomass ◽  
Leaf Chlorophyll Content ◽  
Ph Values ◽  
Leaf Chlorophyll

The study assessed the effects of different pH values of simulated acid rain on growth and leaf chlorophyll content of Eucalyptus grandis. The treatments comprised of two simulated acid rain solutions of pH 4.0 and 3.5, and unacidified water at pH 6.5. Place and Duration of Study was the National Forestry Development Agency, Humid Savannah Zone, Bamenda I Sub-Division, North West Region, Cameroon, between June and September 2019, respectively. The experiment was conducted under field conditions. Thirty 3-month-old seedlings were exposed to each pH level at 7-day intervals using a spray bottle. While two sets of thirty seedlings were administered sulphuric acid calibrated tap water with pH values of 4.0 and 3.5, the third set that constituted the control was sprayed with normal tap water. Data were collected on morphology, biomass, and leaf chlorophyll content at the end of the study and subjected to analysis of variance and Scheffé’s test. Results: The pH 3.5 treatment resulted in significantly lower responses of height (12.95 cm), number of leaves (15.28), leaf area (23.96 cm2) and total biomass (0.61 g) than the other two pH levels that did not differ for any of the traits. Average values between pH 4.0 and control were 20.39 cm, 22.00, 45.66 cm2 and 1.77 g. Stem diameter and root collar diameter declined from 2.87 mm and 4.14 mm at the control to 2.54 mm and 3.78 mm at pH 3.5, respectively. Leaves at pH 3.5 showed signs of necrosis, drying and curling. Leaf chlorophyll content was significantly greater in the control (45.30 SPAD units) than in the pH 4.0 (40.01 SPAD units) and pH 3.5 (39.82 SPAD units) treatments that displayed similar responses. Conclusion: The study reveals that simulated acid rain at pH 3.5 can have a harmful effect on chlorophyll content and growth of Eucalyptus grandis.

scholarly journals Selected properties of mahogany wood flour filled polypropylene composites: The effect of maleic anhydride-grafted polypropylene (MAPP)

BioResources ◽  
2020 ◽  
Vol 15 (2) ◽  
pp. 2227-2236
Author(s):  
Vedat Çavuş
Keyword(s):  
Mechanical Properties ◽  
Maleic Anhydride ◽  
Wood Flour ◽  
Zinc Stearate ◽  
Test Results ◽  
Composite Manufacturing ◽  
Polypropylene Composites ◽  
Tensile Impact ◽  
Interfacial Compatibility ◽  
Scanning Electron

The aim of this study was to produce mahogany (Swietenia macrophylla) wood flour filled polypropylene (both recycled and virgin) composites and to determine the effects of maleic anhydride-grafted polypropylene (MAPP) on the interfacial compatibility, density, and other mechanical properties of the resulting composites. Approximately 40 wt% of mahogany wood flour, and 60 wt% of polypropylene, 3 wt% of MAPP, 1.5 wt% of zinc stearate, and 1.5 wt% of wax were used during composite manufacturing. Test specimens were manufactured using extrusion and injection molding processes. The flexural, tensile, impact, and hardness properties of all specimens were determined. Scanning electron microscopy was used to study the morphology and interfacial compatibility of the filler in prepared composites. The test results showed that MAPP use and the filler rates affected the density and mechanical properties of test specimens.

scholarly journals Metal extraction from Cetraria islandica (L.) Ach. lichen using low pH solutions

2008 ◽  
Vol 73 (4) ◽  
pp. 405-413 ◽  
Author(s):  
Ana Cuculovic ◽  
Mirjana Pavlovic ◽  
Dragan Veselinovic ◽  
Scepan Miljanic
Keyword(s):  
Complex Formation ◽  
Acid Rain ◽  
Metal Ion ◽  
Metal Content ◽  
Ph Value ◽  
Low Ph ◽  
Metal Extraction ◽  
Ph Values ◽  
All Solutions ◽  
Extraction Of Metals

Extraction of metals (K, Al, Ca, Mg, Fe, Cu, Ba, Zn, Mn and Sr) from dry Cetraria islandica (L.) Ach. lichen was performed using solutions similar to acid rain (solution A H2SO4-HNO3-(NH4)2SO4 and solution B H2SO4- -HNO3-(NH4)2SO4-NH4NO3). The pH values of these solutions were 2.00, 2.58, 2.87, 3.28, and 3.75. Five consecutive extractions were performed with each solution. In all solutions, the extracted metal content, except Cu and Ca, was the highest in the first extract. The highest percentage of the metals desorbed in the first extraction was obtained using solutions with low pH values, 2.00, 2.58, and 2.87. The lowest percentage in the first extraction was obtained using solutions with pH 3.28 and pH 3.75, indicating influence of the H+ ion on the extraction. According to the results obtained, the investigated metals form two groups. The first group includes K, Al, Ca, Mg, and Fe. They were extracted in each of the five extractions at each of the pH values. The second group includes Ba, Zn, Mn, Cu, and Sr, which were not all extracted at each pH value. The first group yielded three types of extraction curves when the logarithms of extracted metal amounts were plotted as a function of the number of successive extractions. These effects indicate that three different positions (centers) of metal ion accumulation exist in the lichen (due to sorption, complex formation, or other processes present in the tissues).

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