Distribution and Controlling Factors of Dissolved Gaseous Mercury and Reactive Mercury in Seawater Near Yangtze River Estuary

Complex hydrocultural conditions in the estuary affect the migration and transformation of mercury.Using two voyages in July and October 2018,Dissolved Gaseous Mercury(DGM)and Reactive Mercury(RHg)were determined to explore the source,transformation and influence of DGM content in the adjacent waters of Yangtze River Estuary in summer and autumn.The results showed the contents of DGM and RHg in summer were higher than those in autumn,and both of them were higher than those in open sea.In summer and autumn,the Yangtze River brought a higher concentration of DGM,and different flow direction and runoff resulted in differences in the high value region of the surface.The emergence of low-oxygen zones in summer was conducive to the production of DGM.In autumn,windy weather allowed seawater disturbances to promote the release of mercury from the underlying sediments,especially in shallow sea in northwest.RHg showed a higher concentration in the offshore than in the open sea in summer,but there was no such trend in autumn,reflecting the influence of less runoff input.DGM is the main product of RHg reduction,and there was a significant positive correlation between DGM and RHg in summer(r=0.356,P<0.05),while the correlation between DGM and RHg was not significant in autumn due to the influence of light intensity,wind speed and nutrients.The exchange flux of mercury in the adjacent waters of the Yangtze River Estuary was higher than that in the open sea.There was no significant difference of the release flux of mercury in summer and autumn.This article highlighted that the input of mercury from the Yangtze River runoff promotes the release of mercury in seawater,and the hypoxic zone caused by eutrophication is conducive to the production of DGM.

Late Holocene glacier variations indicated by theδ18O of ice core enclosed gaseous oxygen in the central Tibetan Plateau

Theδ18O of ice core enclosed gaseous oxygen(δ18Obub)has been widely used for climate reconstruction in polar regions.Yet,less is known about its climatic implication in the mountainous glaciers as the lack of continuous record.Here,we present a long-term,continuousδ18Obub record from the Tanggula glacier in the central Tibetan Plateau(TP).Based on comparisons of its variation with regional climate and glacier changes,we found that there was a good correlation between the variation of theδ18Obub in this alpine ice core and the accumulation and melting of this glacier.The more developed the firn layer on glacier surface,the more positive theδ18Obub.Conversely,the more intense the glacier melting,the more negative theδ18Obub.Combined with the chronology of ice core enclosed gases,the glacier variations since the late Holocene in the central TP were reconstructed.The result showed that there were four accumulation and three deficit periods of glaciers in this region.The strongest glacier accumulation period was 1610-300 B.C.,which corresponds to the Neoglaciation.The most significant melting period was the last 100 years,which corresponds to the recent global warming.The Medieval Warm Period was relatively significant in the central TP.However,during the Little Ice Age,there was no significant glacier accumulation in the central TP,and even short deficit events occurred.Comparisons of the late Holocene glacier variation in the central TP with glacier and climate variations in the TP and the Northern Hemisphere showed that it was closely related to the North Atlantic Oscillation.

Gaseous elemental mercury concentration in atmosphere at urban and remote sites in China

An investigation of gaseous elemental mercury concentration in atmosphere was conducted at Beijing and Guangzhou urban, Yangtze Delta regional sites and China Global Atmosphere Watch Baseline Observatory （CGAWBO） in Mt. Waliguan of remote continental area of China. High temporal resolved data were obtained using automated mercury analyzer RA-915^＋. Results showed that the overall hourly mean Hg^0 concentrations in Mt. Waliguan were 1.7±1.1 ng/m3 in summer and 0.6±0.08 ng/m^3 in winter. The concentration in Yangtze Delta regional site was 5.4±4.1 ng/m^3, which was much higher than those in Waliguan continental background area and also higher than that found in North America and Europe rural areas. In Beijing urban area the overall hourly mean Hg^0 concentrations were 8.3±3.6 ng/m^3 in winter, 6.5±5.2 ng/m^3 in spring, 4.9±3.3 ng/m^3 in summer, and 6.7±3.5 ng/m^3 in autumn, respectively, and the concentration was 13.5±7.1 ng/m^3 in Guangzhou site. The mean concentration reached the lowest value at 14：00 and the highest at 02：00 or 20：00 in all monitoring campaigns in Beijing and Guangzhou urban areas, which contrasted with the results measured in Yangtze Delta regional site and Mr. Waliguan. The features of concentration and diurnal variation of Hg^0 in Beijing and Guangzhou implied the importance of local anthropogenic sources in contributing to the high Hg^0 concentration in urban areas of China. Contrary seasonal variation patterns of Hg^0 concentration were found between urban and remote sites. In Beijing the highest Hg^0 concentration was in winter and the lowest in summer, while in Mt. Waliguan the Hg^0 concentration in summer was higher than that in winter. These indicated that different processes and factors controlled Hg^0 concentration in urban, regional and remote areas.

Flow structures of gaseous jets injected into water for underwater propulsion

Gaseous jets injected into water are typically found in underwater propulsion, and the flow is essentially unsteady and turbulent. Additionally, the high water-to-gas density ratio can result in complicated flow structures; hence measuring the flow structures numerically and experimentally remains a challenge. To investigate the performance of the underwater propulsion, this paper uses detailed NavierStokes flow computations to elucidate the gas-water interactions under the framework of the volume of fluid （VOF） model. Furthermore, these computations take the fluid compressibility, viscosity, and energy transfer into consideration. This paper compares the numerical results and experimental data, showing that phenomena including expansion, bulge, necking/breaking, and back-attack are highlighted in the jet process. The resulting analysis indicates that the pressure difference on the rear and front surfaces of the propul- sion system can generate an additional thrust. The strong and oscillatory thrust of the underwater propulsion system is caused by the intermittent pulses of the back pressure and the nozzle exit pressure. As a result, the total thrust in underwater propulsion is not only determined by the nozzle geometry but also by the flow structures and associated pressure distri- butions.

Accelerated Corrosion of Pure Fe Induced by Gaseous ZnCl_2 at High Tempreratures

ZnCl2 is one of the dominant aggressive species in waste incinerators or other advanced combustion power generation systems. In this study, the influence of minor amount of gaseous ZnCl2 on the corrosion behavior of pure iron was examined at 600-800℃ in a pure oxygen environment. The corrosion rate usually increased markedly with increasing temperatures at a fixed ZnCl2 content or with increased ZnCl2 contents at a constant temperature. The corrosion products were composed of a thin outer layer of ZnFe2O4 spinel and an inner zone with a much thicker layer of Fe2O3, which exhibited a serious separation from the matrix. Moreover, a molten FeCl2 layer was observed at the scale substrate interface. The accelerated corrosion of pure iron was attributed to the existence of FeCl2 with low melting point on the metal surface, which destroyed the cohesion and adhesion of the oxide scale. The results are discussed in relation to the thermodynamic factors and the presence of volatile compounds in the reaction system.

High Temperature Gaseous Rare-Earth Permeation of Polyoxotungstates: An New Effective Method for the Preparation of Tungsten Bronzes

New polyoxometalate α-K 12H 3[Y(BW 11O 39) 2]·25H 2O was synthesized and treated by high temperature gaseous rare earth permeation to prepare tungsten bronze K 0.475WO 3. XRD, TG-DTA, XPS, 183W-NMR,CV and AC impedance spectra were used to characterize the resulting material. The results of XPS indicate that La has permeated and diffused into the body of the sample and exists in the forms of binding with other components. The crystal structure parameters of K 0.475WO 3 were obtained by the analysis of XRD, which shows tetragonal crystal system with lattice parameters: a=12 28 nm, c=3.833 nm, V=578.48 nm -3. The conductivities calculated from the results of AC impedance spectra of the material increase with the increasing of temperature, which shows a semiconductor character.

Heterogeneous Photocatalytic Degradation Kinetic of Gaseous Ammonia Over Nano-TiO_2 Supported on Latex Paint Film

Objective To investigate the photocatalytic degradation of gaseous ammonia in static state by using nano-TiO2 as photoeatalyst supported on latex paint film under UV-irradiation. Methods Experiments were conducted to study the relationship between the initial concentration of ammonia and the degradation products competing to be adsorbed on catalyst surface. Degradation of ammonia and its products were detected by spectrophotometry and catalytic kinetic spectrophotometry, respectively. Results On the one hand, TiO2 catalyst was excellent for degradation of ammonia, and the crystal phase of TiO2, anatase or ruffle, had little effect on degradation of ammonia, but the conversion of ammonia grew with the increase of catalyst content. On the other hand, apparent rate constant and conversion of ammonia decreased with the increase of initial concentration of ammonia, and the photocatalytic degradation reaction followed a pseudo-first-order expression due to-the evidence of linear correlation between -lnC/C0 vs. irradiation time t, but the relationship between initial concentration and the degradation products was not linear in low initial concentration. Conclusion Whether the photocatalytic degradation of ammonia in static state follows a first-order reaction depends on the initial ammonia concentration due to competition in adsorption between reactant and the degradation products.

Equilibrium Diagram in the Presence of a Gaseous Phase and Its Application(Overview Part Ⅰ)

T or logp1/T diagrams showing the influence of temperature and pressure in a gaseous phase were presented in part Ⅰ of the overview. In part Ⅱ, the relationship between ET and Kellogg diagrams or between ET and EPh diagrams is discussed. ET diagrams cover larger field of application than the other two. The practical use of ET or logp1/T diagrams is also investigated, which includes: the calculation of polycomponent equilibria in a gaseous phase, the prediction of corrosion products, the interpretation of catalytic mechanism, the exploration for the possibility of producing aluminum with carbothermic method, etc. The limitation of this kind of diagrams is also discussed.

Decomposition of gaseous CF_2CIBr by cold plasma method

The paper presented the results regarding the decomposition of gaseous CF_2ClB_r by cold plasma method.After two minutes discharge,the maximum decomposition rate of 2660 Pa CF_2ClB_r pure and 2660 Pa CF_2ClBr plus 7980 Pa O_2 reached 60% and 80%,respectively.The pa- per also studied the cold plasma gas phase chemistry reaction mechanism of CF_2ClBr at low pres- sure,and the pressure effects of CF_2ClBr and added gas(He,N_2,O_2 and dry air)on the CF_2ClBr decomposition respectively by cold plasma method.These studies will be helpful to application of cold plasma method in the treatment of hazardous gaseous wastes.

Influence of perfusion by gaseous oxygen persufflation on rat donor liver

BACKGROUND: Hepatic ischemia-reperfusion injury is one of the major problems in liver transplantation. This study aimed to investigate the possible improvement of aerobic metabolism of ischemic donor livers through systemic persufflation with gaseous oxygen in rinse solution. METHODS: Thirty rats were randomly divided into 3 groups. In group A (control, n = 10), the livers were perfused with 4 ℃ lactic acid ringer's solution through the can-nulated portal vein for 25 minutes soon after warm ischemia for 30 minutes. In group B (n =10), the livers were treated the same way as in group A except for addition of gaseous oxygen in the rinse solution. In group C (n =10), the livers were treated similarly as in group B except for addition of superoxide dismutase (SOD) in the rinse solution. RESULTS: In group B, the malondialdehyde(MDA)levels in hepatic tissues after perfusion were significantly increased (P< 0. 01), whereas the SOD levels were markedly decreased (P <0.01). After combined use with antioxidant in group C, the levels of MDA and SOD in hepatic tissues after perfusion recovered significantly (P<0.01). CONCLUSION: Perfusion by gaseous oxygen persufQation in combination with antioxidative agents is promising for resuscitating the ischemically altered livers for successful transplantation.

Removal of gaseous acetic acid using ionic liquid [EMIM][BF_4]

This work proposed to use the ionic liquid [EMIM][BF_4] as absorbent for the absorption of gaseous acetic acid. The feasibility of this technology was investigated from molecular level to industrial scale. The acetic acid absorption experiment was carried out using [EMIM][BF_4],and the removal ratio of acetic acid in the gas product can achieve 88.6% at 20C under atmospheric pressure at the laboratory scale. Based on the experimental results, a reliable strict equilibrium phase model embedding the parameters of the UNIFAC model was established. On this basis, the conceptual process design and optimization of acetic acid removal by [EMIM][BF_4] at an industrial scale was done, and the most suitable design and operation parameters were obtained. For a further step, the binding energy between [EMIM][BF_4] and acetic acid was calculated to give some insights into the separation mechanism, and the results indicate that the interaction between acetic acid and IL is much stronger than that between nitrogen and IL. Moreover, hydrogen bond can be formed between the cation-acetic acid as well as the anion-acetic acid.

Gaseous Penetration of Pr into PbTiO_3 Ceramics and Their Electric Properties

The gaseous Pr-penetration is a new method to modify ceramics, which is expected to be a promising method for producing new conductor ceramic materials. The gaseous penetration of Pr into PbTiO_3 ceramics and their improved electric properties were reported. Through XRD, EPMA and SEM analysis,it is confirmed that the gaseous penetration makes Pr enter into PbTiO_3 ceramics, and the new compound of Pr_2Ti_2O_7 is formed by the penetration of Pr in the gaseous state. The formed new Pr_2Ti_2O_7-PbTiO_3 ceramic materials have a significant change in electric properties. The room temperature resistivity decreases from 2.0×10^(10) Ω·m to 9.487 Ω·m. The grain resistance and the grain boundary resistance decrease with increase in temperature, and the PTCR effect disappears. The tendency of transition to a conductive body is manifest.

Allelopathy of Gaseous Volatiles of Eupatorium adenophorum on Seed Germination and Seedling Growth of Pinus yunanensis

[ Objective] The paper was to understand allelopathy of gaseous volatiles of Eupatorium adenophorum stems and leaves on seed germination and seedling growth of P/nus yunnanens/s. [ Method] P. yunnanens/s seeds were treated by fresh stems and leaves of E. adenophorum in translucent airtight container under high concentration （0.069 4 g/cm3 ）, middle concentration （0.023 1 g/cm3 ） and lower concentration （0. 007 7 g/cm3 ）, respectively. [ Result] Gaseous volatiles affected seed germination process; with the increasing processing concentration, the day on which seeds began to germinate and the day reaching germination peak were delayed, and the germination quantity on the day reaching germination peak was decreased ; the day on which the germination quantity began to significantly re- duce was delayed ; the process curve was developed from sudden increase and sudden decrease to gentle change, and nearly became a beeline at high concentration. The effects of gaseous volatiles on seed germination （ seed germination rate, germination potential, germination index） and seedling growth （fresh weight, dry weight, radicle length, hypceotyl length） of P. yunnanens/s were basically consistent, showing a regularity that high concentration had stronger inhibition effect and the inhibition effect became weaker with the decreasing concentration of E. adenophorum. E. adenophorum was widely distributed under P. yunnanens/s forests, and might affect natural regeneration and growth of P. yunnanens/s via allelopathy. [ Conclusion ] The paper provides reference for scientific management of P. yunnanens/s forests.

Forming Mechanism of Gaseous Defect in Ti-48Al-2Cr-2Nb Exhaust Valves Formed with Permanent Mold Centrifugal Casting Method

A method combining theoretical analysis with experiment is adopted and the flowing process of Ti-48A1-2Cr-2Nb alloy melt poured in a permanent mould during the centrifugal casting process has been analyzed. A mathematical model of the filling process is established and the forming mechanism of internal gaseous defect is summarized. The results of calculation show that the melt fills the mould with varying cross-section area and inclined angle. The filling speed of the cross-section is a function of filling time. The cross-section area is directly proportional to the filling speed and the inclined angle is inversely proportional to the filling speed at a given rotating speed of the platform. Both of them changes more obvious near the mould entrance. The gaseous defect can be formed in several ways and the centrifugal field has an important influence on the formation of the defect. In addition, the filling process in centrifugal field has been verified by wax experiments and the theoretical analysis are consistent with experimental results.

Annual Time-series Analyses of Total Gaseous Mercury Measurement and its Impact Factors on the Gongga Mountains in the Southeastern Fringe of the Qinghai-Tibetan Plateau

Long-term monitoring programs for measurement of atmospheric mercury concentrations are presently recognized as powerful tools for local,regional and global studies of atmospheric long-range transport processes,and they could also provide valuable information about the impact of emission controls on the global budget of atmospheric mercury,their observance and an insight into the global mercury cycle. China is believed to be an increasing atmospheric mercury emission source. However,only a few measurements of mercury,to our knowledge,have been done in ambient air over China. The highly-time resolved atmospheric mercury concen-trations have been measured at Moxi Base Station (102°72′E 29°92′N,1640 m asl) of the Gongga Alpine Ecosystem Observation and Experiment Station of Chinese Academy of Sciences (CAS) from May 2005 to June 2006 by using a set of Automatic Atmospheric Mercury Speciation Analyzers (Tekran 2537A). Measurements were carried out with a time resolution of every 15 minutes. The overall average total gaseous mercury (TGM) covering the measurement periods was 4±1.38 ng·m-3 (N=57310),which is higher than the global background level of approximately 1.5～2.0 ng·m-3. The measurements in all seasons showed a similar diurnal change pattern with a high concentration during daytime relative to nighttime and maximum concentration near solar noon and minimum concentration immediately before sunrise. The presence of diurnal TGM peaks during spring and summer was found earlier than that during autumn and winter. When divided seasonally,it was found that the concentrations of TGM were highest in winter with 6.13 ± 1.78 ng·m-3 and lowest in summer with 3.17 ± 0.67 ng·m-3. There were no significant differences in TGM among wind sectors during each season. Whereas Hg generally exhibited significant correlations with the parameters,such as temperature,saturated vapor pressure,precipitation,ultraviolet radiation (UV) and atmospheric pressure at the whole measurement stage,and the correlations varied seasonally. Our results suggest that the local or regional abundant geothermal activities,such as thermal spring,anthropogenic source processes and changes in meteorological conditions,regulate and affect Hg behavior in the study area.

No difference in activity of Sod-1 genotypes of Poa annua to short-term treatment of ambient gaseous organic pollution

Our previous studies indicated that genotypes at locus Sod-1 of Poa annua changed clinally along a gradient of gaseous organic pollution. In the present study, we aimed to know whether there were differential responses of activities of different superoxide dismutase （SOD） genotypes to short-term treatment of ambient gaseous organic pollution. Significant bias from Hardy-Weinberg equibrium was observed on locus Sod-1, and no genotype Sod- l-BB was found. Significantly increased activities were observed in most treatments for genotype Sod-1-AA and in one treatment for genotype Sod-1-AB. However, no significant difference in SOD activities was found between the two genotypes. It was interpreted that fitness difference between the two genotypes was small and treatment duration was too short or extent of ambient organic pollution was too low to lead to differential responses. Other environmental factor effects on activities of superoxide dismutases can also explain the results.

Characteristics of Gaseous Pollutants at a Regional Background Station in Southern China

Measurements of gaseous pollutants(O3, NOx, SO2, and CO) were conducted at Dinghushan background station in southern China from January to December 2013.The levels and variations of O3, NOx, SO2, and CO were analyzed and their possible causes discussed. The annual average concentrations of O3, NOx, SO2, and CO were 24.6 ± 23.9, 12.8 ± 10.2, 4.0 ± 4.8, and 348 ± 185 ppbv, respectively. The observed levels of the gaseous pollutants are comparable to those at other background sites in China. The most obvious diurnal variation of O3 was observed in autumn, with minima in the early morning and maxima in the afternoon. The diurnal variations of SO2 showed high values during the day. The diurnal cycles of NOx showed higher values in the morning and lower values during the night. Higher CO concentrations were observed in spring followed by winter, autumn, and summer. Biomass burning, in combination with the transport of regional pollution, is an important source of CO, SO2, and NOx in spring and winter. Backward trajectories were calculated and analyzed together with corresponding pollutant concentrations. The results indicate that air masses passing over polluted areas are responsible for the high concentrations of gaseous pollutants at the Dinghushan background station.

Studies of flow field characteristics during the impact of a gaseous jet on liquid–water column

Both experimental and numerical studies were presented on the flow field characteristics in the process of gaseous jet impinging on liquid–water column. The effects of the impinging process on the working performance of rocket engine were also analyzed. The experimental results showed that the liquid–water had better flame and smoke dissipation effect in the process of gaseous jet impinging on liquid–water column. However, the interaction between the gaseous jet and the liquid–water column resulted in two pressure oscillations with large amplitude appearing in the combustion chamber of the rocket engine with instantaneous pressure increased by 17.73% and 17.93%, respectively. To analyze the phenomena, a new computational method was proposed by coupling the governing equations of the MIXTURE model with the phase change equations of water and the combustion equation of propellant. Numerical simulations were carried out on the generation of gas, the accelerate gas flow, and the mutual interaction between gaseous jet and liquid–water column.Numerical simulations showed that a cavity would be formed in the liquid–water column when gaseous jet impinged on the liquid–water column. The development speed of the cavity increased obviously after each pressure oscillation. In the initial stage of impingement, the gaseous jet was blocked due to the inertia effect of high-density water, and a large amount of gas gathered in the area between the nozzle throat and the gas–liquid interface. The shock wave was formed in the nozzle expansion section. Under the dual action of the reverse pressure wave and the continuously ejected high-temperature gas upstream, the shock wave moved repeatedly in the nozzle expansion section, which led to the flow of gas in the combustion chamber being blocked, released, re-blocked, and re-released. This was also the main reason for the pressure oscillations in the combustion chamber.

Study on gaseous CS_2 using laser-induced fluorescence

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Equilibrium Diagram in the Presence of a Gaseous Phase and Its Application(Overview Part Ⅱ)

オhis paper is the first part of an overview to introduce ET or logP-1/T thermodynamic diagrams which show the chemical and electrochemical equilibria in the presence of a gaseous phase. The established principles and methods of these two types of diagrams are explained. Some examples are also discussed.