Effect of soot on immersion freezing of water and possible atmospheric implications     

O. Popovicheva  E. Kireeva  N. Persiantseva  T. Khokhlova  N. Shonija  V. Tishkova  B. Demirdjian 《Atmospheric Research》2008,90(2-4):326-ICNAA07

More than 3000 water droplets with soot particles immersed were monitored individually to identify the effect of heterogeneous freezing and establish the link between soot properties and freezing efficiency. A set of soot samples from many combustion sources, including an aircraft engine combustor were examined. The list of key soot properties affecting freezing were determined. It appears that soot effectiveness in causing the droplets to freeze mainly depends on the soot behaviour in water defined by the mass density of soot agglomerates, size and wetting. When large mass particles were homogeneously distributed through droplets and were stable to sedimentation effects median freezing temperatures of such droplets were significantly warmer than pure water droplets. The long-term presence of large soot agglomerates in water leads to an increase in the freezing efficiency over time because of the slow kinetics of wetting. Small sizes of soot agglomerates stimulate aggregative instability in droplets with large soot mass which decreases the total soot surface area and the freezing temperature. The highest freezing efficiency is found for homogeneously distributed soot agglomerates of high porosity. A gradual increase of the freezing temperature in correspondence with number density of active oxygen-containing sites is observed for soots having surfaces of low or intermediate polarity. However, highly soluble surface compounds, such as sulfates, may be easily dissolved in water leading to a decrease in the potential freezing efficiency. This was the case found for aircraft engine combustor generated soot. Therefore relatively hydrophobic soot with a significant number of oxygen-containing functional groups but not covered totally by hydrophilic sites and soluble compounds is proposed to act as the most efficient immersion freezing nuclei in the atmospheric cloud droplets.  相似文献   

CO2 solubility in aqueous solutions containing Na+, Ca2+, Cl−, SO42− and HCO3-: The effects of electrostricted water and ion hydration thermodynamics     

《Applied Geochemistry》2016

Dissolution of CO₂ into deep subsurface brines for carbon sequestration is regarded as one of the few viable means of reducing the amount of CO₂ entering the atmosphere. Ions in solution partially control the amount of CO₂ that dissolves, but the mechanisms of the ion's influence are not clearly understood and thus CO₂ solubility is difficult to predict. In this study, CO₂ solubility was experimentally determined in water, NaCl, CaCl₂, Na₂SO_4, and NaHCO₃ solutions and a mixed brine similar to the Bravo Dome natural CO₂ reservoir; ionic strengths ranged up to 3.4 molal, temperatures to 140 °C, and CO₂ pressures to 35.5 MPa. Increasing ionic strength decreased CO₂ solubility for all solutions when the salt type remained unchanged, but ionic strength was a poor predictor of CO₂ solubility in solutions with different salts. A new equation was developed to use ion hydration number to calculate the concentration of electrostricted water molecules in solution. Dissolved CO₂ was strongly correlated (R² = 0.96) to electrostricted water concentration. Strong correlations were also identified between CO₂ solubility and hydration enthalpy and hydration entropy. These linear correlation equations predicted CO₂ solubility within 1% of the Bravo Dome brine and within 10% of two mixed brines from literature (a 10 wt % NaCl + KCl + CaCl₂ brine and a natural Na⁺, Ca²⁺, Cl⁻ type brine with minor amounts of Mg²⁺, K⁺, Sr²⁺ and Br⁻).  相似文献   

石门县上五通石膏矿区水文地质条件及其作用浅析     

董斌 《湖南地质》1990,9(2):62-67

石门县上五通石膏矿床是我省发现的大型优质石膏矿床之一。矿区水文地质条件比较简单,石膏矿体具有良好的隔水顶、底板,保存完整。但由于构造活动及地表风化作用的影响,矿层在地下水的作用下,其保存情况及矿石类型形成了明显的分带性。笔者以矿区水文地质条件为基础,将石膏矿的溶蚀带划分为淋滤带、溶滤水化带和水化带;并对矿区水文地质条件的成矿作用和地下水对早期形成的硬石膏矿床的改造和破坏作用进行了具体分析;提出了寻找隐伏石膏矿的水化学标志。这对研究石膏矿床的成因、指导找矿,以及加强矿山建设都是有益的。  相似文献   

硼酸对硫氧镁水泥力学性能的影响          下载免费PDF全文

安生霞  肖学英  李颖  文静  郑卫新  常成功  董金美  黄青 《盐湖研究》2017,25(4):72-78

硫酸浸出法制备硼酸的废弃母液经过浮选法分离产生的硫酸镁中通常含有硼酸等杂质,为了研究硼酸对硫氧镁水泥凝结硬化及力学性能的影响,以改性硫氧镁水泥(MOS)为基础体系,测试了硼酸含量对硫氧镁水泥凝结时间、抗压和抗折强度的影响,讨论了硼酸对硫氧镁水泥抗水性、水化产物及微观形貌的影响。结果表明:硫氧镁水泥的凝结时间随硼酸含量的增加而延长;硼酸可以明显降低硫氧镁水泥的早期强度,对后期强度的降低作用不及早期明显;试件浸水28 d后,较高含量的硼酸提高了试件抗压强度的软化系数,而降低了抗折强度的软化系数,因此硫酸镁中硼酸含量不应超过0.7%;硫酸镁中硼酸含量不影响硫氧镁水泥水化产物的组成,但降低了水化产物的结晶度并改变其显微结构。  相似文献   

Frost action and hydration as rock weathering mechanisms on schist: A laboratory study   总被引：1，自引：0，他引：1  

Barry D. Fahey 《地球表面变化过程与地形》1983,8(6):535-545

Recently it has been proposed that stress generated by the adsorption of water to clay surfaces in argillaceous rocks may be an important agent of mechanical weathering in polar and alpine environments, implying that long-held views on the status of frost action in these areas may be in need of revision. This study documents the response, under controlled experimental conditions, of aggregates of fresh and partlyweathered schist and fresh pre-cut schist blocks to 500 accelerated (12 hour) freeze-thaw and hydration-dehydration cycles. Aggregate samples subjected to freezing cycles produced the largest amounts of material in the less than 2 mm size range (an average of 8 per cent and 16 per cent for the fresh and partly-weathered aggregates respectively), whereas humidity cycles above and below freezing yielded lesser amounts (3 per cent and 4 per cent respectively). The fresh schist blocks were found to be highly resistant to both mechanisms; only those experiencing freeze-thaw oscillations produced measurable amounts of detritus. Although hydration effects were not as effective as frost action in causing particle size reduction in aggregates, the two mechanisms may well reinforce one another in periglacial environments, enhancing the ability of these areas to serve as source regions for loess.  相似文献   

Pressure-induced migration of zeolitic water in laumontite     

Y.?Lee  T.?VogtEmail author  J. A.?Hriljac 《Physics and Chemistry of Minerals》2004,31(7):421-428

A polycrystalline sample of natural laumontite (Pleasant Valley, Connecticut) was studied up to 6.8 (1) GPa at room temperature using monochromatic synchrotron X-ray powder diffraction and a diamond-anvil cell. A methanol: ethanol: water mixture was used as a penetrating pressure-transmitting fluid. A dry sample measured before adding the pressure fluid inside the diamond-anvil cell contained ~12 H₂O per formula unit, consistent with the water content of partially dehydrated laumontite. Upon increasing the pressure to 0.2 (1) GPa, fully hydrated laumontite with 18 H₂O per unit cell formed and the unit-cell volume expanded by 2.6%. Further pressure increase up to 2.4 (1) GPa resulted in a gradual contraction of the unit-cell volume and individual cell lengths. During this process, a successive order–disorder transition of hydrogen-bonded water molecules from their symmetry sites was observed, concomittent with an inflectional behavior of the monoclinic beta angle and the channel ellipticity. Above 3 GPa, a tripling of the b axis was detected. Thereafter, up to 6.8 (1) GPa, the compression behavior was reversed for the c axis length and the monoclinic beta angle which showed a gradual increase and decrease, respectively, without any apparent volume discontinuity. We suspect that different ordering of the water molecules or Ca cations inside the channels along the b axis may be responsible for the observed supercell transition above 3 GPa.  相似文献