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1.
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
2.
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
3.
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
4.
The hydrolysis of silicic acid, Si(OH)4, was studied in a simplified seawater medium (0.6 M Na(Cl)) at 25°C. The measurements were performed as potentiometric titrations (hydrogen electrode) in which OH? was generated coulometrically. The total concentration of Si(OH)4, B, and log[H+] were varied within the limits 0.00075 ? B ? 0.008 M and 2.5 ? -log[H+] ? 11.7, respectively. Within these ranges the formation of SiO(OH)3? and SiO2(OH)22? with formation constants log β?11(Si(OH)4 ? SiO(OH)3? + H+) = ?9.472 ±0.002 and log β?21(Si(OH)4 ? SiO2(OH)22? + 2H+) = ?22.07 ± 0.01 was established. With B > 0.003 M polysilicate complexes are formed, however, with their formation does not significantly affect the evaluated formation constants. Data were analyzed with the least squares computer program LETAGROPVRID. 相似文献
5.
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
6.
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
7.
The choice of convenient basic constituents for evaluating pH stability of aqueous systems is discussed, and two useful interaction parameters are defined and related to the buffer capacity: the interaction capacity, , and the interaction intensity, ; for pH and TOTH, δ′H, H = ?βH?1, where βH is the pH buffer capacity. A method is presented for the computation of exact values of all interaction capacities and intensities through inversion of the Jacobian matrix of the system of non-linear equations describing the aqueous system. The major species of an aqueous system (H2O, H+, solid phases, gases, and the most abundant solute species) are shown to constitute a useful set of basic constituents for evaluation of approximate pH buffer capacities according to a simple rule: the major-minor species rule for zeroth order pH-TOTH interaction. The concepts of buffering and pH-statting are examined and contrasted; it is demonstrated that the buffer capacity of an aqueous system cannot be infinite: it is limited by the concentration of solutes in solution. The effect upon pH of variations in constituents other than H+ is described in terms of first order interactions via complex formation and solid formation; approximate formulas for calculation are derived. Higher order interactions are derived from combinations of first order ones. The pH stability of the ocean system is examined in terms of an aqueous phase model including ion-association reactions and a heterogeneous model incorporating CO2 in the gas phase, quartz, kaolinite, calcite, chlorite, and illite, in addition to the aqueous phase. There is an approximately three-fold enhancement of buffer capacity in the aqueous model as a consequence of ion-association. Only a few interaction pathways are of quantitative significance in establishing the buffer capacity. Results for the heterogeneous ocean model lend quantitative support to Sillén's notion of pH stability: the buffer capacity is about four hundred times greater than that of the aqueous phase model. 相似文献
8.
The apparent solubility product of calcite was measured by saturometry as a function of temperature and salinity. Simplified equations for the carbonic-acid dissociation constants of Mehrbach et al., 1973 (Limnol. Oceanogr., 18: 897–907) have been derived from their experimental data and used to calculate apparent solubility product, K′sp, K′sp at 25°C and 35‰ salinity, was found to be K′sp = 4.70 × 10?7(mol2kgseawater?2) An equation was fitted to the experimental data, resulting in pK′sp = 6.5795 ? 3.7159 × 105(TS) + 0.91056(T/S) ? 22.110(1.0/S)The mean activity coefficients, , were calculated at various temperatures and salinities, using the thermodynamic solubility product of Jacobson and Langmuir, 1974 (Geochim. Cosmochim. Acta, 38: 301–318) and the apparent solubility products quoted in their paper. The change in K′sp at each salinity, as a function of temperature, was used to calculate the apparent enthalpy of dissociation for calcite, ΔH′, and the extrapolated value of ΔH0 was in good agreement with that of Jacobson and Langmuir. Finally, this work was used to calculate saturation profiles for oceanic stations and as a basis for comment of the accuracy of in-situ saturometry, as well as the applicability of in-situ K′sp pressure corrections. 相似文献
9.
A widely used method for determining iodate in seawater involves reaction of the IO3? with excess I?, under acid conditions, to form I2 which is measured colorimetrically. It is known that when the acidification is by mineral acid, nitrite can interfere with the method by oxidising I? to I2 in an analogous way to IO3?. Some workers have used sulphamic acid for acidification since it is reported to destroy nitrite in solution.We have investigated the extent of nitrite interference in the colorimetric determination of iodate using both mineral acid and sulphamic acid for acidifying the reaction mixture. In seawater the extent of the interference is equivalent to 0.212 μM 1?1 IO3? per μM 1?1 NO2? with sulphuric acid, and 0.128 μM 1?1 IO3? per μM 1?1 NO2? with sulphamic acid. This means that for a seawater containing 0.31 μM 1?1 (39 μg 1?1) IO3?, the presence of 0.5 μM 1?1 NO2? will lead to an error of 25% in the iodate determined colorimetrically in methods using sulphuric acid, and 15% in methods in which sulphamic acid is used. 相似文献
10.
J.V. Leyendekkers 《Marine Chemistry》1974,2(2):89-110
A general equation is derived for predicting the partial molal volume (pmv) of an electrolyte in seawater, using binary solution data, and seawater density data. The composition of seawater need not be “average” - prediction can be made for any composition. Simpler equations are derived for “average” seawater. The ranges cover , t = 0–30°C and p = 1–1,000 bar, subject to the availability of binary solution data. Estimates of the pmv's of a number of electrolytes are made and compared with experimental values and the summed ionic values. 相似文献
11.
Self-diffusion coefficients of five major ions have been determined by a radioactive tracer method (capillary tube method) in seawater of salinity 34.86 at 25°C. Data are presented for Na+, Ca2+, Cl−, SO42, and HCO3−, which constitute about 95% by weight of sea salt. The influence of temperature and salinity on these coefficients has been studied for Na+ and Cl− which are the major components of sea salt: self-diffusion coefficients of these two ions have been measured in seawater, at different temperatures for a salinity of 34.86 and at different salinities for a temperature of 25°C. Diffusion coefficients of the same ions have been determined at 25°C by using another radioactive tracer method (quasi-steady cell method). In this experiment, seawater ions were allowed to diffuse from natural seawater into dilute seawater. Data have been obtained at 25°C for Na+, Ca 2+, Cl−, SO42− and HCO3−, corresponding to different salinity gradients. 相似文献
12.
Shinichiro Noriki 《Journal of Oceanography》1983,39(6):324-326
An improved Strickland and Parsons' method, in which silicate correction is made, is described for the colorimetric determination of phosphate in seawater. Silicate correction is made by subtracting the value of 0.025 (C/100)2, whereC is silicate concentration (µg atoms 1?1), from the observed phosphate concentration. The relative standard deviations are 2 % at the 1 µg atom PO 4 3? ?Pl?1 level and less than 1 % at the 3 µg atoms PO 4 3? ?Pl?1 level in seawater. 相似文献
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.
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
15.
P.N. Froelich L.W. Kaul J.T. Byrd M.O. Andreae K.K. Roe 《Estuarine, Coastal and Shelf Science》1985,20(3):239-264
Concentrations of dissolved nutrients (NO3, PO4, Si), germanium species, arsenic species, tin, barium, dimethylsulfide and related parameters were measured along the salinity gradient in Charlotte Harbor. Phosphate enrichment from the phosphate industry on the Peace River promotes a productive diatom bloom near the river mouth where NO3 and Si are completely consumed. Inorganic germanium is completely depleted in this bloom by uptake into biogenic opal. The ratio taken up by diatoms is about 0·7 × 10?6, the same as that provided by the river flux, confirming that siliceous organisms incorporate germanium as an accidental trace replacement for silica. Monomethylgermanium and dimethylgermanium concentrations are undetectable in the Peace River, and increase linearly with increasing salinity to the seawater end of the bay, suggesting that these organogermanium species behave conservatively in estuaries, and are neither produced nor consumed during estuarine biogenic opal formation or dissolution. Inorganic arsenic displays slight removal in the bloom. Monomethylarsenic is produced both in the bloom and in mid-estuary, while dimethylarsenic is conservative in the bloom but produced in mid-estuary. The total production of methylarsenicals within the bay approximately balances the removal of inorganic arsenic, suggesting that most biological arsenic uptake in the estuary is biomethylated and released to the water column. Dimethylsulfide increases with increasing salinity in the estuary and shows evidence of removal, probably both by degassing and by microbial consumption. An input of DMS is observed in the central estuary. The behavior of total dissolvable tin shows no biological activity in the bloom or in mid-estuary, but does display a low-salinity input signal that parallels dissolved organic material, perhaps suggesting an association between tin and DOM. Barium displays dramatic input behavior at mid-salinities, probably due to slow release from clays deposited in the harbor after catastrophic phosphate slime spills into the Peace River. 相似文献
16.
The stability constants of the ion pairs NaSO4?, KSO4?, MgSO4?, CaSO4, MgCl+ and CaCl+ were determined at 25°C and 0.7 M formal ionic strength, by measuring the solubility of gypsum (CaSO4 · 2H2O) in different media. The media used contained one or two of the following electrolytes: NaCl, KCl, MgCl2, NaClO4, Mg(ClO4)2, Na2SO4. Values for the stability constants are 1.22, 1.84, 12.3, 30.6, 0.48 and 1.20 M?1, respectively, and the solubility product for gypsum is 2.87 · 10?4M2. The distribution of the main constituents of seawater was calculated using these results and the values of the carbonate and bicarbonate constants given by Dyrssen and Hansson (1972–1973). The solubility of gypsum in seawater as calculated and determined experimentally was 21.43 mM and 21.10 mM, respectively. 相似文献
17.
John C. Ludwick 《Marine Geology》1975,19(1):19-28
Use of the quadratic shear-stress law for estimating boundary drag requires specific knowledge of the magnitude of a drag coefficient, CD, and sectional mean velocity, . In previous attempts to adapt the relationship for use in studies of marine-sediment transport, the flow measurement has been standardized at a level 100 cm above the bed. The particularized value of the drag coefficient has been designated as C100.In the entrance area to Chesapeake Bay, Virginia, C100 has been found to range through unacceptably wide limits. Two-thirds of the values obtained are between 3.5 · 10?3 and 5.4 · 10?2. Mean C100 for the area is 1.3 · 10?2 as compared to 3 · 10?3 for tidal channels within Puget Sound, Washington.Present data suggest that, given a moveable bed, a size hierarchy of mobile bed forms, time-varying flow, and a lack of equilibrium between flow and bed, C100 changes continuously with boundary shear stress.Accurate evaluation of boundary shear stress in tidal entrances with high flow rates and mobile beds presently requires measurement of velocity profiles. 相似文献
18.
The conditional stability constant of HSO4? has been determined at 25°C, 1 atm and a formal ionic strength of 0.7 M in solutions containing sodium, magnesium, chloride and sulphate. This was done spectrophotometrically (UV), using diphenylamine as indicator. The value obtained was 17.0 ± 0.1 (molar scale). Single ion activity coefficients for Na2SO4, K2SO4 and MgSO4 have been calculated according to the Bates et al. (1970) model, assuming that the sulphate ion is not hydrated. It was found that the single ion activity coefficient of sulphate changes very little between Na2SO4, K2SO4 and MgSO4 when the formal ionic strength is kept constant.These results have been used to obtain relations between the stability constants of NaSO4? and MgSO4 valid for seawater. 相似文献
19.
The Tait-Gibson parameter, , and the refractive index of seawater are estimated from binary solution data. The predicted and experimental values agree closely. The maximum deviations, at , are 1.7 bars for and 0.0001 for the refractive index. The results show that binary solution data, analysed on the basis of the Tammann-Tait-Gibson model for aqueous solutions, can be used to predict the properties of seawater of composition different to that of standard seawater. 相似文献
20.
M. Dileep Kumar 《Marine Chemistry》1981,10(6):475-486
Oxidation state diagrams have been constructed for different sulphur species. Sulphur oxyacids are stressed with respect to their key role in the cycling of inorganic sulphur species, besides sulphides and elemental sulphur. Following the stable sulphate species in seawater, metastable species are S4O62−, S2O32− and S0. Stability of different species found from these diagrams were compared with the earlier literature. A case study, from Solar Lake (Sinai) is inconcurrent with the results of the present diagrams. 相似文献