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1.
Measurements of 226Ra and 210Pb in barite samples separated from different depths of a piston core from the eastern equatorial Pacific are reported. 226Ra is enriched in the barite as would be expected from the chemistries of Ra and Ba; the ratio centers around 1.5 · 1014 atoms/mole. The results suggest that barite is concentrating Ra at a rate comparable to its decay rate, viz. 5.78 · 10?3 yr?1. The gross 210Pb depletion with respect to 226Ra is indicative of 222Rn loss due to the smallness of the barite crystals. 相似文献
2.
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
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.
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
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 nitrogen relations of Enteromorpha spp. growing on intertidal mud flats have been examined over a twelve-month period. Nitrogen assimilation rates using 15N have been used to calculate the production of the alga and were between 0·046 and 0·217 mg (g dry wt alga)?1 h?1 A considerable quantity of the alga was buried beneath the sediment over the growth season and was calculated to be equivalent to an input of up to 9·52 g N m?2 per month and 32 g N m?2 over one complete growth season. Based on carbon, this latter value represented an input of approximately 320 g C m?2 annually. Low rates of nitrogenase activity (acetylene reduction) were found to be associated with the Enteromorpha. The organisms responsible for the nitrogenase activity were probably heterotrophic bacteria but they did not contribute significant quantities of nitrogen to the alga. 相似文献
7.
Zena G. Kaufman John S. Lively Edward J. Carpenter 《Estuarine, Coastal and Shelf Science》1983,17(5):483-493
The uptake of urea, nitrate and ammonium by phytoplankton was measured using 15N isotopes over a one-year period in Great South Bay, a shallow coastal lagoon. The bay is a unique environment for the study of nutrient uptake since ambient concentrations of and urea remain relatively high through the year, and phytoplankton are probably never nutrient limited. Urea nitrogen averaged 52% of the total assimilated, while ammonium represented 33% and nitrate 13%. High rates of ammonium uptake occurred only at low urea concentrations (ca< 1-μg-atom urea l?1). Over the sampling period urea was present in relatively high concentrations, averaging 5·35 μg-atom N l?1, while means for ammonium and nitrate averaged 1·94 and 0·65 μg-atom N l?1, respectively. Total N uptake measured with 15N averaged about 3·3 times the calculated (from elemental ratios and 14C productivity measurements) N needs of the phytoplankton population. Highest nitrogen uptake occurred in the summer and coincided with the primary production maximum. 相似文献
8.
Björn Kjerfve 《Estuarine, Coastal and Shelf Science》1982,15(5):553-559
Tethered current crosses are simple, reliable tools in making measurements of estuarine currents in the absence of surface waves. The standard error of the estimate of current speed is less than 5 cm s?1 for the particular crosses and weights used in a calibration experiment. The useful velocity range of these current crosses was 8–147 cm s?1, corresponding to a measured angle, α, from 2° to 30°. Regression of the independently measured current speed on yielded coefficients of determination greater than 0·94, indicating that the drag coefficient is not a function of current speed. However, the calculated drag coefficients varied widely from 0·66 to 2·55, depending on the particular combination of cross and weight, varying drastically from the commonly assumed drag coefficient value of 1·12. Thus, in using current crosses, it is imperative to calibrate each cross against a current meter reading to determine an appropriate value for the drag coefficient for a particular current cross and weight. 相似文献
9.
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
10.
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
11.
Spectrophotometric measurements are reported for the first apparent dissociation constant of hydrogen sulfide in seawater over the temperature range 7.5–25°C and 2–35.8‰ salinity. These data are described by the expression . The second apparent dissociation constant in potassium chloride solution was estimated potentiometrically using a sulfide specific ion electrode. A value of ～13.6 was found for pK2′ at a KCl concentration of 0.67 M. It is suggested that explicit reference to the sulfide ion, S2?, in describing equilibria in marine waters be dropped in favor of a formulation involving the bisulfide ion, HS?. 相似文献
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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.
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
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16.
The concentrations of Ni, Mn, Cr, Cu, Co, Zn, Fe, Pb and organic carbon have been determined in sediments of the Pagassitikos Gulf. They vary with the ‘sand equivalent’ content, s′, characteristic of the grain size, and are related to it by the equation, in which the constants c1, k and d depend on the element. Consequently, since the metal concentrations in a sample are much less representative of the area from which it has been taken than its ‘sand equivalent’ content, a contour map of the latter constitutes a reliable guide to the general pattern of the elements. Superimposed on it, we detect isolated patches of moderate pollution close to the harbour of Volos and a few, slight, natural anomalies, such as increased Mn and Ni, the former in the east and the latter in the south of the Gulf. 相似文献
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19.
Jean Pierre Baudin 《Marine environmental research》1982,7(3):227-233
Uptake of 65Zn by Gammarus aequicauda results in a concentration factor of approximately 50 and it is characterised by a maximal accumulation level attained as early as the third day of the experiment. After ingestion by the gammarids of twenty contaminated meals which are distributed over a 45-day period, a transfer of 65Zn between the food and the consumer can be observed but there is no sign of the biomagnification phenomenon. The retention rate of the radionuclide is only about 1·5% and the 65Zn concentration in the gammarids remains markedly inferior to that of the ingested food.The elimination of the 65Zn fixed directly from water takes place according to an exponential model which corresponds to the existence of three biological half-lives of the radionuclide, . The excretion of 65Zn accumulated from food is a simple exponential phenomenon which corresponds to only one biological half-life of approximately 17 days. 相似文献
20.
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