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1.
The apparent ionization constants for silicic acid, k1 and k2, and the ionic product of water, kw, have been determined in 0.05, 0.1, 0.2, 0.4 and 2.0 M Na(CI) media at 25°C. The medium dependence of these constants was found to fit equations of the form where K1 is the ionization constant in pure water, αi and bi are parameters of which bi has been adjusted to present data. The following results were obtained (αi, bi): pK1 = 9.84, (1.022, ?0.11); pK2 = 13.43, (2.044, ?0.20); and pKw = 14.01 (1.022, ?0.22). ki values are collected in Tables I and II. Attempts have been made to explain the medium dependence of k1 and k2 with weak sodium silicate complexing according to the equilibria giving k11 = 0.37M?1 and k21= 3.0M?1. However, these weak interactions cannot be interpreted unambiguously from potentiometric data at different 1-levels. Probably the medium dependence could equally well be expressed by variations in the activity coefficients.The measurements were performed as potentiometric titrations using a hydrogen electrode. The average number of OH- reacted per Si(OH)4, Z, has been varied within the limits 0 ? Z ? 1.1 and B1, the total concentration of Si(OH)4, between 0.001 M and 0.008 M. k1 was evaluated from experimental data with B ? 0.003 M, and k2 with B ? 0.008 M and Z ? 0.95. 相似文献
2.
An investigation of ferric ion complexing has been conducted in synthetic media and seawater at 25°C. Formation constants were potentiometrically determined for the species FeCl2+, FeCl2+, FeOH2+, and Fe(OH)2+ at an ionic strength of 0.68 m. Formation constants for the ferric chloride complexes were determined as Clβ1 = 2.76 and Clβ2 = 0.44. In a study of the reaction Fe3+ + nH2O ? Fe(OH)n(3?n)+ + nH+ in NaClO4, NaNO3 and NaCl the formation constants were shown to be relatively independent of medium when the effects of nitrate and chloride complexing were taken into account. The average values obtained for these constants are . Reasonable agreement with these values was obtained when these constants were determined in seawater by accounting for the effects of chloride, fluoride and sulfate complexing. 相似文献
3.
Equilibrium constants for copper(II)-carbonate and -bicarbonate species have been determined at 25°C from consideration of malachite, Cu2(OH)2CO3(s), solubility in UV-photo-oxidized perchlorate solutions of 0.72 m ionic strength. The ratios of total dissolved copper, T(Cu), to free copper(II) ion, [Cu 2+], in 30 malachite saturated experimental solutions of 1–10 × 10?3eq kg?1 H2O initial total alkalinity (TAi in the pH range 5.0–9.3 were fitted to a copper(II)-ion speciation model. The experimental data indicate the existence of CuCO3+, CuHCO3+ and Cu(OH)CO3? in addition to the hydrolys and Cu(OH)CO3? in addition to the hydrolysis products in the range of conditions defined by this study. The stoichiometric equilibrium constants, applicable to seawater at 0.72 m ionic strength, 25°C and 1 atm are A speciation model employing the equilibrium constants determined in this study and copper(II) hydrolysis constants from previous work suggests that the inorganic speciation in seawater (pH = 8.2, TA = 2.3 meq kg ?1, 25°C) is dominated by the CuCO30 complex (82%) and that only 2.9% of the total inorganic copper exists as the free copper(II) ion. Hydrolysis products, CuOH+ and Cu(OH)20, account for 6.5% while CuHCO3+ and Cu(OH)CO3? species comprise 1.0 and 6.3% of the total inorganic copper, respectively. 相似文献
4.
The addition of various concentrations (1, 10 and 20 mM) of Group VI anions to sediment slurry resulted in inhibition of the rate of sulphate reduction at the two higher concentrations, the degree of inhibition being in the order of molyb-date . The addition of 20 mM concentrations of these inhibitors almost entirely eliminated sulphate reduction. Doubling the sulphate concentration while using the highest concentration of inhibitors (20 mM) led to the re-establishment of some sulphate reduction in the and treated slurries whereas no such reversal was noticed with . These observations suggested that and are competitive inhibitors of sulphate reduction, while is a non-competitive inhibitor. 相似文献
5.
Vertical measurements of , and N2O concentrations, and uptake, and oxidation rates were measured at 5 sites in western Cook Strait, New Zealand, between 31 March and 3 April 1983. Nitrate increased with depth at all stations reaching a maximum of 10.5 μg-atom at the most strongly stratified station whereas was relatively constant with depth at all stations (～0.1 μg-atom ). The highest rates of oxidation generally occurred in the near surface waters and decreased with depth. N2O levels were near saturation with respect to the air above the sea surface and showed no obvious changes during 24 h incubation. oxidation by nitrifying bacteria may account for about 30% of the total utilization (i.e. bacterial+agal) and, assuming oxidation through to , may supply about 40% of the algal requirements of in the study area. These results suggest that bacterial nitrification is of potential importance to the nitrogen dynamics of the western Cook Strait, particularly with respect to the nitrogen demands of the phytoplankton. 相似文献
6.
Iron solubility equilibria were investigated in seawater at 36.22‰ salinity and 25°C using several filtration and dialysis techniques. In simple filtration experiments with 0.05 μm filters and Millipore ultra-filters, ferric chlorides fluorides, sulfates, and FeOH2+ species were found to be insignificant relative to Fe(OH)2+ at p[H+] = ?log [H+] greater than 6.0. Hydrous ferric oxide freshly precipitated from seawater yielded a solubility product of . Solubility studies based on the rates of dialysis of various seawater solutions and on the filtration of acidified seawater solutions indicated the existence of the Fe(OH)30 species. The formation constant for this species can be calculated as . The Fe(OH)4? species is present at concentrations which are negligible compared to Fe(OH)2+ and Fe(OH)30 in the normal pH range of seawater. However, there is at least one other significant ferric complex in seawater above p[H+] = 8.0 (possibly with bicarbonate, carbonate, or borate ions) in addition to the Fe(OH)2+ and Fe(OH)30 species. 相似文献
7.
Peter Nielsen 《Coastal Engineering》1985,9(3):261-276
An empirical analysis is performed on the most detailed, recent measurements of turbulent oscillatory boundary layer flow. The measurements show that throughout elevations where the flow can be considered horizontally uniform, one deficit model is sufficient for describing the fundamental mode. Some general properties of the non dimensional velocity deficit D1(z) appear with striking consistency. First of all the identity , which is a theoretical result for smooth laminar flow, seems to hold with great accuracy for a large range of turbulent flow conditions as well. This is of principal theoretical interest because all previous analytical eddy viscosity models as well as numerical mixing length models predict a consistent and fairly large difference between Arg D1 and . If the identity between and Arg D1 extends all the way to the bed, it means that the bed shear stress leads the free stream velocity by 45 degrees. It is also found that the structure of smooth turbulent oscillatory flows as measured by Kalkanis (1964) corresponds to a sharp maximum in the normalized energy dissipation rate. 相似文献
8.
9.
R. Chester 《Marine Chemistry》1982,11(1):1-16
The atmospheric, primary down-column and sedimentary fluxes of particulate aluminium (Alp) have been calculated for a number of regions in the Atlantic Ocean.The vertical down-column flux of Alp from Atlantic surface waters exhibits a strong geographical variation, and its magnitude is influenced by supply mechanisms, which control the surface Alp concentrations, and primary production, which affects the rate of down-column transport. Overall, the down-column transport of Alp is greatest in the marginal regions of the Atlantic. In the eastern margins the highest surface water concentrations are found in the region lying between ～30°N and ～10°N, i.e. under the general path of the northeast trades. In this region there is excellent agreement between the dry (i.e. 1 cm?1 s?1 deposition velocity) atmospheric flux (～80 000 ng Alp cm?2 y?1), the primary vertical down-column flux () and the sediment flux (～90 000 ng Alp cm?2 y?1). In the regions to the north (i.e. ～40°N to ～30°N) and to the south (i.e. ～10°N to ～5°S) the primary down-column Alp flux decreases to an average of ～19 000 μg cm?2 y?1, which makes a direct maximum contribution of ～20% of the sediment Alp requirement. In the open-ocean South Atlantic the primary down-column flux of Alp is ～3300 μg cm?2 y?1, this is similar to the dry (i.e. 1 cm?1 s?1 deposition velocity) atmospheric flux, and contributes ～20% of the Alp required by the underlying deep-sea sediment. 相似文献
10.
Thomas G. Wolaver William Johnson Marvin Marozas 《Estuarine, Coastal and Shelf Science》1984,19(2):243-255
The daily concentrations of , , and within the North Inlet system are all negatively associated with tidal stage during the late summer, this association breaking down during the winter. The high concentrations of these constituents during low tide coupled with the lack of streamflow during the late summer suggests that there is an internal source for these species. Ammonium and orthophosphate most likely have their source in sediment diffusion from tidal creek sediments and/or seepage from the vegetated marsh surface during tidal exposure. It is hypothesized that high nitrate plus nitrite values at low tide are caused by nitrification within the tidal water or tidal creek sediments. During the summer there is evidence for a source of dissolved organic nitrogen and dissolved organic phosphorus within the North Inlet system, probably via diffusion from creek sediments. In general the main source of dissolved organic nitrogen is via stream-flow from the adjacent watershed. Particulate nitrogen and phosphorus concentrations are a function of: (1) wind and rain events which cause resuspension of particulate material from the tidal creek banks, (2) rain events which scour the marsh surface during tidal exposure, and (3) high tidal velocities which scour the creek bottoms. 相似文献
11.
Examination of the consequences of the stoichiometric association constant for MgSO4 in seawater as advocated by Johnson and Pytkowicz (1979) leads to a thermodynamic association constant Ka = 212.6, a value 32% greater than KA = 160 derived from conductance data. Use of Ka = 160 leads to a in essential agreement with the value of 10.2 reported by Kester and Pytkowicz (1969). 相似文献
12.
13.
The density of artificial seawater has been measured with a magnetic float densitometer at 1 atm. from 0 to 40°C (in 5° intervals) and from 0 to 21‰ chlorinity. The densities at each temperature have been fitted to a modified Root (1933) equation, and an equation based on the Debye-Hückel limiting law, where AV′, BV′, AV, BV and CV are temperature-dependent constants (related to the ion-water and ion-ion interactions of the major components), d0 is the density of pure water and ClV is the volume chlorinity — . The densities fit these equations to ±9 p.p.m. from 0 to 25°C and ±18 p.p.m. from 30 to 40°C. The densities for artificial seawater are in good agreement with our measurements of Copenhagen seawater and the results for natural seawater obtained from Knudsen's tables.The expansibilities of the artificial seawater mixtures have been calculated from the temperature dependence of the densities. The resulting expansibilities at each temperature were fitted to the equations and where AE′, BE′, AE, BE and CE are constants (related to the effect of temperature on the ion-water and ion-ion interactions of the major components) and α0 is the expansibility of pure water. The expansibilities fit these equations to ±1 p.p.m. and at 35‰ S agree within ±1 p.p.m. with the expansibilities obtained for natural seawater from Knudsen's tables.Theoretical density and expansibility constants have been determined from the apparent equivalent volumes and expansibilities of the major components of seawater by using the additivity principle. The average deviations of the calculated densities and expansibilities are, respectively, ±20 and ±3 p.p.m. over the entire temperature range. 相似文献
14.
Losses of 15N labelled nitrogen in a Spartina alterniflora salt marsh was measured over three growing seasons. Labelled equivalent to 100 μg 15N g?1 of dry soil was added in four instalments over an eight week period. Recovery of the added nitrogen ranged from 93% 5 months after addition of the to 52% at the end of the third growing season which represented a nitrogen loss equivalent to 3·4 gNm?2. The availability of the labelled incorporated into the organic fraction was estimated by calculation of the rate of mineralization. The time required for mineralization of 1% of the tagged organic N increases progressively with succeeding cuttings of the S. alterniflora and ranged from 152 to 299 days. Only 2% of the nitrogen applied as 15N labelled plant material to the marsh surface in the fall could be accounted for in S. alterniflora the following season. 相似文献
15.
Laboratory investigations were conducted on the formation of NaF° ion-pairs at the ionic strength of seawater using specific ion electrodes. Sodium and fluoride ion electrodes produced results which are consistent with the ion-pairing model for these ionic interactions. The stoichiometric association constant for NaF°, , was determined at 15, 25, and 35°C. It was assumed that was a function of temperature, pressure, and ionic strength but not of solution composition. The value for at 25°C and I = 0.7 m is 0.045 ± 0.006. increased with decreasing temperature. This result was used to recompute values of and accounting for the presence of NaF° ion-pairs. The value for indicates that 1.1% of the fluoride in seawater is ion-paired with sodium at 25°C and 35‰ salinity. This fraction increases to approximately 2% at the lower temperatures found in the deep ocean. The percentage of free fluoride in natural seawater was measured at 15, 25, and 35°C to verify the speciation calculated from equilibrium constants. 相似文献
16.
The photolysis of nitrate in seawater by sunlight has been re-examined using abiotic seawater and naturally occurring concentrations. Photochemical formation of nitrite from nitrate was observed. First-order nitrate photolysis rate coefficients calculated from nitrite appearance (corrected for concomitant nitrite photolysis) ranged from 0 to 2.3 yr?1, median 0.7 yr?1. The coefficients did not correlate well with water chemistry, but decreased with increasing light dose. A first-order rate coefficient of 0.4 yr?1 was calculated for the primary photochemical process under sea surface equatorial insolation and cloudiness conditions. However, no significant nitrate concentration decreases could be detected, suggesting an upper limit for the net first-order nitrate loss rate coefficient of 0.3 yr?1. The data thus imply some conversion in the reverse sense: NO2? + hυ →→ NO3?.If our median rate estimate applies to surface oceanic conditions, nitrate photolysis proceeds at roughly 0.02–0.5% of the rate of N incorporation during primary production. It is thus not a significant NO3-N sink. Since such reactive species as oxygen atoms, nitrogen dioxide, and hydroxyl radicals are produced, the reaction may have significant consequences in seawater. However, nitrite photolysis is almost certainly a more significant process.The results show internal inconsistencies and our rates are markedly different from those calculated using data from other studies. Nitrate photolysis rates are theoretically concentration- and light dose-dependent. Whether these dependencies explain the apparent discrepancies is unclear, as methodological effects may also be involved. The system requires further study. 相似文献
17.
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: 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): 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
18.
The apparent solubility product of aragonite in 32‰ seawater at 25.0°C is reported as K′sp = (0.869±0.049) × 10?6(mol2kgseawater?2) thus confirming the value of R.A. Berner, 1976 (Am. J. Sci., 276: 713–730). The apparent solubility product ratio for aragonite and calcite is reported as The deviation of this value from the thermodynamic ratio is atttributed to the formation of a stable low Mg-calcite coating on pure calcite in seawater measurements of solubility. 相似文献
19.
Paolo Boccotti 《Applied Ocean Research》1983,5(3):134-140
For wind waves modelled by a stationary Gaussian process ζ(t) (ζ = height above m.w.l. of one point of the free surface) it is shown that, in a time interval including an instant tm where a maximum ζm occurs, the ratio between ζ(t) and ζm tends with probability approaching one, to the ratio Ψ(t ? tm)/Ψ(O), as tends to infinity, Ψ(t) being the autocovariance of the process.Starting from this result, it is possible to find analytically the characteristic periods of the highest waves in a sea with a given energy spectrum. These periods, calculated according to period definitions of three methods of wave record analysis, are found to be in remarkably good agreement with data from Bretschneider1 and Svasek.2 相似文献
20.
The three dissociation constants of phosphoric acid have been determined in seawater media over the temperature and ionic strength ranges 5–30°C and 0.3-0.9 m. The results obtained fitted the equations (concentrations in mol per kg of solution): The results are only in moderate agreement with those of Kester and Pytkowicz (1967). The reason for this lies partly in differences between the pH scales adopted and partly in the poor precision inherent in their method. 相似文献