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1.
The diffusion coefficient of dissolved silica revisited   总被引：1，自引：0，他引：1  
The diffusion coefficient of dissolved silica was determined for two different salinities, 36 and 0, at temperatures ranging from 2 °C to 30 °C and at an average pH value of 8.1. Our results show limited influence of salinity and a variation by a factor of 2 to 3 of the silica diffusion coefficient within the temperature range considered in this study. The values obtained at 25 °C are in agreement with previous work carried out at room temperature for seawater and freshwater. The dependency on temperature and viscosity of the diffusion coefficient agrees well with the Einstein–Stokes equation. The composition of the solvent appears to be an important factor because it modifies the viscosity and allows for the complexation of the dissolved silica with less mobile ions, while its pH controls the dissolved silica speciation. In seawater, the higher viscosity and the presence of dissociated and polymeric species result in a decrease of the diffusion coefficient compared to freshwater systems.  相似文献   

2.
Human impact on adjacent coastal waters, leading to alteration in nutritional environment and hence affecting phytoplankton biomass (Chlorophyll a), will probably be enhanced by the nearby presence of ports. The main goal of this study is to assess the influence of nearby presence of port on phytoplankton biomass build-up and the physical–chemical environmental characteristics in two contrasting coastal systems (Otaru port, S-IN and an exposed coastal area, S-OUT) in the western Hokkaido coast off Otaru port, Japan. Sampling was conducted on “bi-weekly and monthly” basis during the period of September 2006–December 2007 and data comprising 11 pelagic variables were obtained. In most instance, phytoplankton biomass, nutrients' (NH4, NO3, PO4, and Si(OH)4) concentrations and nutrients' molar ratios were higher at the Otaru port location. Physical parameters (temperature, salinity, hydrogen ion concentration (pH), photosynthetically active radiation (PAR) and dissolved oxygen, (DO)) were not significantly different (P > 0.05) between the two locations. With the exception of salinity, pH and DIC, all variables measured showed significant variation (P < 0.05) with season. While the coefficient of variation (CV) of physical parameters and phytoplankton biomass were relatively higher in Otaru port location (S-IN), the exposed coastal location (S-OUT) showed a higher variation in chemical parameters. Other variables showed different patterns between the two locations. We conclude that ports, due to its activities and restricted circulation favour high nutrient loading and phytoplankton biomass build-up in adjacent coastal systems, thus, suggesting the need for continuous field observation data in order to advance our knowledge on possible future human impact on coastal environment and the need to monitor and control port activities.  相似文献   

3.
pH is a measure of the hydrogen ion activity in a solution, which is a function of temperature. Under normal seawater conditions, it is well constrained. Nowadays, with an increasing interest in complex environments(e.g.,sea ice), a better understanding of the temperature change on pH under extreme conditions is needed. The objective of this paper was to investigate the temperature coefficient of the seawater pH(?pH/?T) over a wide range of temperature, pH, dissolved inorganic carbon(DIC) and sa...  相似文献   

4.
On the basis of the data of hydrochemical investigations of waters of the Sevastopol Bay, we discuss the results of the analysis of the carbonate system and the total alkalinity of seawater obtained by using two methods. By using the linear method of least squares, we compare the results of the analysis of the carbonate system according to pH values and the total alkalinity and according to pH values and dissolved inorganic carbon. It is shown that, within the investigated range of pH values, Alk, and TCO2, the mean relative deviations of values of the fugacity of CO2 and the concentrations of dissolved CO2 and CO32− ions computed by using different input parameters are equal to 3.0, 1.0, and 9.6%, respectively.  相似文献   

5.
Various investigators reported a decrease in pH as seawater is concentrated. A similar phenomenon was reported for Dead Sea waters which are about ten times more saline than seawater. The reasons for the low pH values of Dead Sea waters (pH 5.9–6.5), which precipitate CaCO3, were investigated by determining the apparent dissociation constants of carbonic acid in these brines. A new method, based on alkalinity titration and least-squares fitting, was used to estimate the proton activity coefficient (γH+) and the first and second dissociation constants of carbonic acid (K1′, K2′) in natural and artificial Dead Sea waters. It was found that as the salt content increases, pK′1 and pK′2 values progressively decrease whereas γH+ sharply increase. At the highest salinity investigated (TDS = 330 gl?1) γH+ pK′1 and pK′2 values are 24.5, 5.09 and 6.23, respectively, as compared to about 0.8, 5.9, 9.1 respectively for normal seawater (19‰ chlorinity) at the same temperature (30°C).The implication of the results of this study regarding solubility of CaCO3 and the general behavior of the carbonate system in hypersaline solutions is discussed.  相似文献   

6.
We found a simple function of pH that relates to sea surface temperature (SST, K) and chlorophyll-a (Chl, µg l−1) using measured surface seawater pH, SST and Chl data sets over the North Pacific: pH (total hydrogen scale at 2°C) = 0.01325 SST − 0.0253 Chl + 4.150 (R2 = 0.95, p < 0.0001, n = 483). Moreover, evaluating the seasonal variation of pH based on this algorithm, we compared the measured pH with the predicted pH at the observational time series stations in subpolar and subtropical regions. The average of ΔpH (measured - predicted, n = 52) was 0.006 ± 0.022 pH. Therefore, the combination of SST and Chl can allow us to determine the spatiotemporal distribution of pH over the North Pacific. Using the climatological data sets of SST and Chl with our pH algorithms, we have described the seasonal distributions of pH at 25°C (pH(25)) and pH in situ temperature (pH(T)) over the North Pacific surface water.  相似文献   

7.
A study of the diurnal and seasonal variation in the physico-chemical conditions within intertidal rock pools on the West coast of Scotland was undertaken to provide data on the environmental conditions experienced by animals inhabiting these pools. The temperature, pH, partial pressure of oxygen (PO2) and salinity were measured every hour for 24 h and the total alkalinity, partial pressure of carbon dioxide (PCO2) and carbon dioxide content (CCO2) calculated. This sampling regime was carried out once a month for 12 months to determine the extent of seasonal variation in conditions within temperate pools.Large diurnal variations were recorded in nearly all the physico-chemical parameters measured. The greatest variation was recorded in the temperature and PO2 of the water but significant changes in pH and PCO2 were also recorded. Total alkalinity varied little during any 24 h period but carbonate alkalinity, which was always lower than total alkalinity, showed slightly greater variation. There was also considerable variation in the magnitude of these diurnal changes between pools at different heights on the shore.Diurnal variation in the physico-chemical conditions within the pools were observed throughout the year although the magnitude of these changes varied seasonally. Detailed studies on individual pools demonstrated that appreciable local variation existed in the physico-chemical conditions within each pool.  相似文献   

8.
李世娜  刘永 《海洋学报》2010,32(10):6882-6888
利用基于密度泛函理论的第一性原理全势线性缀加平面波方法,研究了立方反ReO3结构Cu3N在零温(0 K)零压下的平衡晶格常数、体弹模量及其对压强的一阶导数,计算结果与其他实验及理论结果基本相符. 同时得出Cu3N的弹性常数,Poisson比等,并分析出Cu3N在零温零压下是稳定的. 通过准谐Debye模型计算Cu3N的热力学性质,得到了Cu3N的晶格常数、等压比热容、等容比热  相似文献   

9.
中华乌塘鳢(Bostrychus sinensis)属于广盐广温、低氧耐受性强、药用价值高的鱼类,为我国东南沿海重要养殖对象。谷胱甘肽过氧化物酶(glutathione peroxidase,GPx)是生物体内重要的抗氧化酶,能够清除过氧化氢防止机体生物膜氧化受损,研究中华乌塘鳢GPx基因对其养殖及海洋生态研究具有重要意义。利用分子克隆技术获得了中华乌塘鳢GPx7和GPx8(分别命名为BsGPx7和BsGPx8)的cDNA序列。BsGPx7编码186个氨基酸,含有2个半胱氨酸(Cys56和Cys85)催化位点;BsGPx8编码210个氨基酸,含有1个半胱氨酸(Cys109)催化位点。利用RT-PCR方法研究了BsGPx7、BsGPx8基因在中华乌塘鳢组织中的分布表达,以及不同浓度镉离子(7.5,15,30 mg/L)胁迫下BsGPx7、BsGPx8基因的表达量变化。结果显示,BsGPx7和BsGPx8在组织中呈泛在性表达,其中肝脏的表达量最高,其次是鳃和皮肤。不同浓度的镉离子胁迫下,BsGPx7基因在鳃和皮肤中的表达量均显著上调(P<0.05),BsGPx8基因在肝脏、鳃和皮肤中的表达量均显著上调(P<0.05)。成功构建了原核表达载体,表达并纯化获得了BsGPx7重组蛋白(rBsGPx7)。对rBsGPx7在不同温度和pH条件下的酶活性进行了测定,表明rBsGPx7在35℃和pH 8条件下酶活性最高。综上提示,BsGPx7与BsGPx8参与了机体对抗镉离子诱导的氧化应激的过程,可能在抗氧化防御中起一定作用。  相似文献   

10.
Dissolved gaseous mercury (DGM) was measured continuously using two newly developed techniques and a manual technique. The continuous techniques were based on the equilibrium between the aqueous and gaseous phase (DGM = Hgextr / H', Hgextr is the measured mercury concentration in the gas phase, H' is the Henry's Law coefficient at the desired temperature). In order to calculate the annual mercury evasion from the Mediterranean Sea, diurnal and seasonal measurements of DGM, total gaseous mercury in air (TGM), water temperature and wind speed were performed. During August 2003, March–April 2004 and October–November 2004 measurements of these parameters were conducted on board the RV Urania. The continuous measurements of DGM showed a diurnal variation in concentration, at both coastal and off shore sites, with higher concentrations during daytime than nighttime. The concentration difference could be as large as 130 fM between day and night. The degree of saturation was calculated directly from the measurements, S = Hgextr / TGM and was found to vary between the different seasons. The highest average degree of saturation (850%) and the largest variation in saturation (600–1150%) was observed during the summer. The spring showed the lowest variation (260–360%) and the lowest average degree of saturation (320%). The autumn also showed a large variation in saturation (500–1070%) but a lower average (740%) compared to the summer cruise. This might be explained by the temperature difference between the different seasons, since that parameter varied the most. The flux from the sea surface was calculated using the gas exchange model developed by Nightingale et al. [Nightingale, P.D., Malin, G., Law, C.S., Watson, A.J., Liss, P.S., Liddicoat, M.I., Boutin, J., Upstill-Goddard, R. C., 2000. In situ evaluation of air–sea gas exchange parameterization using novel conservative and volatile tracers. Global Biogeochemical Cycles, 14(1):373–387]. The evasion varied between the different seasons with the highest evasion during the autumn, 24.6 pmol m− 2 h− 1. The summer value was estimated to 22.3 pmol m− 2 h− 1 and the spring to 7.6 pmol m− 2 h− 1. Using this data the yearly evasion from the Mediterranean Sea surface was estimated to 77 tons.  相似文献   

11.
Dissolved gaseous mercury (DGM) was measured continuously using two newly developed techniques and a manual technique. The continuous techniques were based on the equilibrium between the aqueous and gaseous phase (DGM = Hgextr / H', Hgextr is the measured mercury concentration in the gas phase, H' is the Henry's Law coefficient at the desired temperature). In order to calculate the annual mercury evasion from the Mediterranean Sea, diurnal and seasonal measurements of DGM, total gaseous mercury in air (TGM), water temperature and wind speed were performed. During August 2003, March–April 2004 and October–November 2004 measurements of these parameters were conducted on board the RV Urania. The continuous measurements of DGM showed a diurnal variation in concentration, at both coastal and off shore sites, with higher concentrations during daytime than nighttime. The concentration difference could be as large as 130 fM between day and night. The degree of saturation was calculated directly from the measurements, S = Hgextr / TGM and was found to vary between the different seasons. The highest average degree of saturation (850%) and the largest variation in saturation (600–1150%) was observed during the summer. The spring showed the lowest variation (260–360%) and the lowest average degree of saturation (320%). The autumn also showed a large variation in saturation (500–1070%) but a lower average (740%) compared to the summer cruise. This might be explained by the temperature difference between the different seasons, since that parameter varied the most. The flux from the sea surface was calculated using the gas exchange model developed by Nightingale et al. [Nightingale, P.D., Malin, G., Law, C.S., Watson, A.J., Liss, P.S., Liddicoat, M.I., Boutin, J., Upstill-Goddard, R. C., 2000. In situ evaluation of air–sea gas exchange parameterization using novel conservative and volatile tracers. Global Biogeochemical Cycles, 14(1):373–387]. The evasion varied between the different seasons with the highest evasion during the autumn, 24.6 pmol m− 2 h− 1. The summer value was estimated to 22.3 pmol m− 2 h− 1 and the spring to 7.6 pmol m− 2 h− 1. Using this data the yearly evasion from the Mediterranean Sea surface was estimated to 77 tons.  相似文献   

12.
The various assumptions implicit in the calculation of acid dissociation constants (based on ionic medium standard states) from potentiometric titrations using a cell with liquid junction (i.e. a pH measuring cell) have been examined. It was concluded that results can be obtained having an accuracy commensurate with the experimental precision. It has been shown that although the precise composition of the medium is a function of the hydrogen ion concentration (because of the protolytic nature of some of the ions in the media, e.g., sulphate and fluoride), the effect of such variations in the medium composition can be compensated for when defining the activity of hydrogen ion on an ionic medium standard state by defining the concentration of hydrogen ion as:
[H]SWS=h(1 + βHSO4ST + βHFET)
where βHSO4 and βHF are the relevant association constants and ST and FT are the total concentrations of sulphate and fluoride, respectively.This approach was used to obtain values for the ionic product of water (KW) in artificial seawater media at various temperatures and ionic strengths. These were fitted to give the equation (molal concentration units):
pKw= 3441.0T+2.256-0.709112 (rms deviation 0.01)
where I is the formal ionic strength of the artificial seawater medium and T is the absolute temperature. The values obtained are in reasonable agreement with those found by previous workers.  相似文献   

13.
A theoretical evaluation of basic thermodynamic relationships reveals that variation of activity coefficients, ion pairing and electrical interactions must be considered when modelling ionic diffusion in seawater. The contributions of ion-pair formation and change in activity coefficient along the diffusion path were studied experimentally by conducting diffusion experiments in which solutions of KCl, NaCl, MgCl2, Li2SO4, K2SO4, Na2SO4 and MgSO4, at an ionic strength of 0.7, were allowed to diffuse into distilled water. The study reveals that the thermodynamic factor, required to correct for changes in the activity coefficient along the diffusion path, is significant for all the salts studied. Agreement between a simple diffusion model, which does not include ion pairing, and observed data was good for completely dissociated salts, but poor for salts which are known to form ion pairs at the concentration levels studied. The diffusion of MgSO4, 0.425 of which is associated at I = 0.7, was successfully modelled by assuming that the diffusion coefficient of the MgSO40 ion pair is different from the diffusion coefficient of the dissociated salt. The diffusion coefficient of this ion pair is estimated to be 1.9 × 10−5 cm2 s−1 at 30°C, as compared to 0.49 × 10−5 cm2 s−1 for the dissociated salt. It is suggested that the high mobility of this ion pair could cause magnesium enrichment in pore water of sulfate depleted sediments.  相似文献   

14.
海底热液活动及其周边环境的调查研究是海洋科学领域的热点之一。海底热液喷口环境的物理化学参数,尤其是浅水型热液,会受到潮汐变化的影响。台湾龟山岛靠近冲绳海槽南端分布有多处浅水型热液喷口(30m)。2010年5月,浙江大学、杭州电子科技大学和台湾中山大学对该海域实施了联合考察,利用电化学传感器获得了低温热液喷口(24.834 14°N,121.961 91°E)连续87h的温度和pH现场观测数据。基于Morlet复小波变换方法,分析了浅水型热液喷口的温度和pH现场观测时间序列的变化周期,并通过与当地潮汐记录数据作比较,获得了其与潮汐信号之间的潜在关系,证实了潮汐变化是海底白色热泉喷口物理化学参数现场观测最主要的影响因素。温度和pH现场观测数据经Morlet复小波变换后的小波系数分别存在规律的12.9h和12.5h变化周期,并且温度的小波系数在准半日周期尺度与潮汐高度呈负相关变化,相关系数为-0.89;pH的小波系数情况相反,相关系数为0.76。  相似文献   

15.
Hydrodynamic model application to Buzzards Bay is performed using a three-dimensional Boundary-fitted Hydrodynamic model in this study. The model is forced with observed tidal harmonic constants along the open boundaries and winds on the surface. The main focus of the present study is to model the detailed wind and tide-induced circulation in Buzzards Bay. The observed surface elevations and currents given in [Butman, B., Signell, R., Shoukimas, P., Beardsley, R.C., 1988. Current Observations in Buzzards Bay, 1982–1986. Open File Report 88-5. United States Geological Survey] and the tide and current harmonics given in [Signell, R.P., 1987. Tide- and Wind-forced Currents in Buzzards Bay, Massachusetts. Technical Report WH-87-15. Woods Hole Oceanographic Institution, Woods Hole, Massachusetts] are used to validate the model predictions. The calibrated model is then used to study the relative contributions of tidal and wind forcing on the instantaneous and residual circulation in Buzzards Bay. The amplitudes and phases of the principal tidal constituents at 10 tidal stations in Buzzards Bay obtained from a harmonic analysis of a 60-day simulation compare well with the observed data. The predicted amplitude and phase of the M2 tidal constituent of surface elevations at these stations are, respectively, within 4 cm and 5° of the observed data. The errors in the model-predicted M2 harmonic principal current speeds are less than 6 cm/s, and the principal current directions and phases are within 14° of the observations. The observed surface elevations and currents given in [Butman, B., Signell, R., Shoukimas, P., Beardsley, R.C., 1988. Current Observations in Buzzards Bay, 1982–1986. Open File Report 88-5. United States Geological Survey] are used to validate the model-predicted low-frequency surface elevations and currents. The model predictions in low-frequency surface elevations at Woods Hole closely follow the trends seen in the observations with a correlation coefficient of 0.735, but fail to capture some of the peak surges seen in the observations. The model-predicted low-frequency currents in the east–west direction at stations in Buzzards Bay compare well with the observations with the correlation coefficient exceeding 0.811 and the model capturing the trends seen in the observations, for the most part. However, the model-predicted north–south velocities does not compare well with the observations. The model-predictions agree with the observations that the tidal currents in Vineyard Sound lagged the currents in Buzzards Bay by more than 3 h. The interaction of wind stress with large bathymetric gradients was shown to cause many vortices in Buzzards Bay, as seen from the model predictions. Model simulations show that the winds play a more dominant role than the tides in the generation of the barotropic residual currents in Buzzards Bay, while the model-predicted tide-induced residual current was seen to be small.  相似文献   

16.
Direct bed shear stress measurements in bore-driven swash   总被引：1，自引：0，他引：1  
Direct measurements of bed shear in the swash zone are presented. The data were obtained using a shear plate in medium and large-scale laboratory bore-driven swash and cover a wide range of bed roughness. Data were obtained across the full width of the swash zone and are contrasted with data from the inner surf zone. Estimates of the flow velocities through the full swash cycle were obtained through numerical modelling and calibrated against measured velocity data. The measured stresses and calculated flow velocities were subsequently used to back-calculate instantaneous local skin friction coefficients using the quadratic drag law. The data show rapid temporal variation of the bed shear stress through the leading edge of the uprush, which is typically two–four times greater than the backwash shear stresses at corresponding flow velocity. The measurements indicate strong temporal variation in the skin friction coefficient, particularly in the backwash. The general behaviour of the skin friction coefficient with Reynolds number is consistent with classical theory for certain stages of the swash cycle. A spatial variation in skin friction coefficient is also identified, which is greatest across the surf-swash boundary and likely related to variations in local turbulent intensities. Skin friction coefficients during the uprush are approximately twice those in the backwash at corresponding Reynolds number and cross-shore location. It is suggested that this is a result of the no-slip condition at the tip leading to a continually developing leading edge and boundary layer, into which high velocity fluid and momentum are constantly injected from the flow behind and above the tip region. Finally, the measured stress data are used to determine the asymmetry and cross-shore variation in potential sediment transport predicted by three forms of sediment transport formulae.  相似文献   

17.
Interannual variations of the air-sea CO 2 exchange from 1965 to 2000 in the Pacific Ocean are studied with a Pacific Ocean model.Two numerical experiments are performed,including the control run that is forced by climatological monthly mean physical data and the climate-change run that is forced by interannually varying monthly mean physical data.Climatological monthly winds are used in both runs to calculate the coefficient of air-sea CO 2 exchange.The analysis through the differences between the two runs shows that in the tropical Pacific the variation of export production induced by interannual variations of the physical fields is negatively correlated with that of the air-sea CO 2 flux,while there is no correlation or a weak positive correlation in the subtropical North and South Pacific.It indicates that the variation of the physical fields can modulate the variation of the air-sea CO 2 flux in converse ways in the tropical Pacific by changing the direct transport and biochemical process.Under the interannually varying monthly mean forcing,the simulated EOF1 of the air-sea CO 2 flux is basically consistent with that of sea surface temperature(SST) in the tropical Pacific,but contrary in the two subtropical Pacific Ocean.The correlation coefficient between the regionally integrated air-sea CO 2 flux and area-mean SST shows that when the air-sea CO 2 flux lags SST by about 5 months,the positive coefficient in the three regions is largest,indicating that in the tropical Pacific or on the longer time scale in the three regions,physical processes control the flux-SST relationship.  相似文献   

18.
We established a precise DeLIF (Dual Emission Laser Light Fluorescence) system for the instant measurement of the pH field in laboratory experiments. This method is very important in studies of the biological impacts of CO2 sequestration, i.e., effects of pH on organisms. The technique is demonstrated by applying it to the pH measurement around a liquid CO2 droplet, which has a large gradient of CO2 concentration near its interface, the concentration value on the boundary being known as the solubility of CO2. In the Laser Induced Fluorescence (LIF) method using quinine and an ultraviolet laser light source, the relatively unstable pulse of the laser source decreased the measurement reliability. We therefore investigated many kinds of fluorescent dye and demonstrated the DeLIF measurement, identifying a process for cancelling fluctuations of laser light intensity. Quinine and sulforhodamine were used as fluorescence dyes. The molar absorption coefficient and emission intensity of quinine depend on the pH of aqueous solutions, while those of sulforhodamine are not as much affected by pH. The ratio of these fluorescence intensities represents pH at each point of the image. As a result, the pH field was successfully measured with an uncertainty of only approximately ±0.005, for 3.0 < pH. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

19.
王晓坡  宋渤  吴江涛  刘志刚 《海洋学报》2010,32(10):7158-7163
采用反转法计算得到了O2-CO2混合气体新的势能参数.在此基础上,根据分子动力学理论,计算了混合气体在零密度下的输运性质,包括黏度系数、热扩散系数和热扩散因子,计算的温度范围为273.15—3273.15 K.与实验值比较表明,计算结果可以满足实际工程应用.  相似文献   

20.
Enzymatic properties of UFE, a novel marine fibrinolytic enzyme   总被引：2，自引：0，他引：2  
A novel potent protease, Urechis unicinctus fibrinolytic enzyme (UFE), was firstly discovered. The enzymatic properties of UFE were further investigated. As a low molecular mass protein, UFE appeared to be very stable to heat and pH. When temperature was below 50 ℃, the remnant enzyme activity remained almost unchanged, but when temperature was raised to 60 ℃, the remnant enzyme activity began to decrease rapidly. UFE was quite stable in the range of pH value from 3 to 12, especially in slightly alkaline pH value. Mn2 , Cu2 and Fe2 ions were activators of UFE, while Fe3 and Ag ions were inhibitors of UFE. Fe2 ion along with Fe3 ion might regulate UFE activity in vivo. The optimum pH and temperature of UFE were about 8 and 50 ℃, respectively. Other characteristics of this enzyme were also studied. Systematic research results are significant when UFE is applied for medical and industrial purposes.  相似文献   

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