Diffusion coefficients of major ions in seawater     

A. Poisson  A. Papaud 《Marine Chemistry》1983,13(4):265-280

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   

Formation and stability of mixed Mg/Ca/phytate species in synthetic seawater media: Consequences on ligand speciation     

Pasquale Crea  Concetta De Stefano  Demetrio Milea  Silvio Sammartano   《Marine Chemistry》2008,112(3-4):142-148

The results of a potentiometric investigation (by ISE-H⁺, glass electrode) on the speciation of phytate ion (Phy¹²⁻) in an ionic medium simulating the major components (Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻ and SO₄²⁻) of natural seawater, at different salinities and t = 25 °C, are reported. The work was particularly aimed at determining the possible formation of mixed Ca²⁺–Mg²⁺–phytate ion pairs, and to establish how including the formation of these mixed species would affect the speciation modeling in seawater media. After testing various speciation models, that considering the formation of the MgCaH₃Phy⁵⁻, MgCaH₄Phy⁴⁻, Mg₂CaH₃Phy³⁻ and Mg₂CaH₄Phy²⁻ species was accepted, and corresponding stability constants were determined at two salinities (S = 5, 10). A discussion is reported both on the choice of the experimental conditions and on the possibility to extend these results to those typical of real seawater. A detailed procedure is also described to demonstrate that the stability of these species is higher than that statistically predicted. As reported in literature, a parameter, namely log X, has been determined in order to quantify this extra stability for the formation of each mixed species at various salinities. For example, at S = 10, log X₁₁₃ = 2.67 and log X₁₁₄ = 1.37 for MgCaH₃Phy⁵⁻ and MgCaH₄Phy⁴⁻ (statistical value is log X_stat = 0.60), and log X₂₁₃ = 6.11 and log X₂₁₄ = 2.15 for Mg₂CaH₃Phy³⁻ and Mg₂CaH₄Phy²⁻ (log X_stat = 1.43), respectively. Results obtained also showed that the formation of these species may occur even in conditions of low salinity (i.e. low concentration of alkaline earth cations) and low pH (i.e., more protonated ligand).  相似文献   

Effect of changes in water salinity on ammonium, calcium, dissolved inorganic carbon and influence on water/sediment dynamics     

P. Lpez 《Estuarine, Coastal and Shelf Science》2003,56(5-6):943-956

The effect of a sudden increase in salinity from 10 to 37 in porewater concentration and the benthic fluxes of ammonium, calcium and dissolved inorganic carbon were studied in sediments of a small coastal lagoon, the Albufera d'Es Grau (Minorca Island, Spain). The temporal effects of the changes in salinity were examined over 17 days using a single diffusion-reaction model and a mass-balance approach. After the salinity change, NH₄⁺-flux to the water and Ca-flux toward sediments increased (NH₄⁺-flux: 5000–3000 μmol m⁻² d⁻¹ in seawater and 600/250 μmol m⁻² d⁻¹ in brackish water; Ca-flux: −40/−76 meq m⁻² d⁻¹ at S=37 and −13/−10 meq m⁻² d⁻¹ at S=10); however, later NH₄⁺-flux decreased in seawater, reaching values lower than in brackish water. In contrast, Ca-flux presented similar values in both conditions. The fluxes of dissolved inorganic carbon, which were constant at S=10 (55/45 mmol m⁻² d⁻¹), increased during the experiment at S=37 (from 30 mmol m⁻² d⁻¹ immediately after salinity increase to 60 mmol m⁻² d⁻¹ after 17 days).In brackish conditions, NH₄⁺ and Ca²⁺ fluxes were consistent with a single diffusion-reaction model that assumes a zero-order reaction for NH₄⁺ production and a first-order reaction for Ca²⁺ production. In seawater, this model explained the Ca-flux observed, but did not account for the high initial flux of NH₄⁺.The mass balance for 17 days indicated a higher retention of NH₄⁺ in porewater in the littoral station in seawater conditions (9.5 mmol m⁻² at S=37 and 1.6 mmol m⁻² at S=10) and a significant reduction in the water consumption at both sites (5 mmol m⁻² at S=37; 35/23 mmol m⁻² at S=10). In contrast, accumulation of dissolved inorganic carbon in porewater was lower in seawater incubations (−10/−1 meq m⁻² at S=37; 50/90 meq m⁻² at S=10) and was linked to a higher efflux of CO₂ to the atmosphere, because of calcium carbonate precipitation in water (675/500 meq m⁻²). These results indicate that increased salinity in shallow coastal waters could play a major role in the global carbon cycle.  相似文献   

Modelling of natural and synthetic polyelectrolyte interactions in natural waters by using SIT, Pitzer and Ion Pairing approaches     

Francesco Crea  Alba Giacalone  Antonio Gianguzza  Daniela Piazzese  Silvio Sammartano   《Marine Chemistry》2006,99(1-4):93

In this paper SIT and Pitzer models are used for the first time to describe the interactions of natural and synthetic polyelectrolytes in natural waters. Measurements were made potentiometrically at 25 °C in single electrolyte media, such as Et₄NI and NaCl (for fulvic acid 0.1 < I /mol L^− 1 < 0.75), and in a multi-component medium simulating the composition of natural waters at a wide range of salinities (for fulvic and alginic acids: 5 < S < 45) with particular reference to sea water [Synthetic Sea Water for Equilibrium studies, SSWE]. In order to simplify calculations, SSWE was considered to be a “single salt” BA, with cation B and anion A representing all the major cations (Na⁺, K⁺, Mg²⁺, Ca²⁺) and anions (Cl⁻, SO₄²⁻) in natural sea water, respectively. The ion pair formation model was also applied to fulvate and alginate in artificial sea water by examining the interaction of polyanions with the single sea water cation. Results were compared with those obtained from previous speciation studies of synthetic polyelectrolytes (polyacrylic and polymethacrylic acids of different molecular weights). Results indicate that the SIT, Pitzer and Ion Pairing formation models used in studies of low molecular weight electrolytes may also be applied to polyelctrolytes with a few simple adjustments.  相似文献   

The thermodynamics and kinetics of the hydrogen sulfide system in natural waters     

Frank J Millero 《Marine Chemistry》1986,18(2-4)

The thermodynamics and kinetics of the H₂S system in natural waters have been critically reviewed. Equations have been derived for the solubility and ionization of H₂S in water and seawater as a function of salinity, temperature and pressure. Pitzer parameters for the interaction of the major cations (Na⁺, Mg²⁺ and Ca²⁺) with HS⁻ have been determined to allow one to calculate values of pK₁^* in various ionic media. The limited data available for the interaction of trace metals for HS⁻ are summarized and future work is suggested.The kinetics of oxidation of H₂S have also been examined as a function of pH, temperature, and salinity. The discrepancies in the available data are largely due to the different [O₂]/[HS−] ratios used in various studies. Over a limited pH range (6–8) the pseudo first order rate constant for the oxidation is shown to be directly proportional to the activity of HS⁻. Further studies are suggested to examine the effect of ionic media and temperature on the rate of oxidation.  相似文献   

Influence of Salinity on pH and Aluminum Concentration on the Interaction of Acidic Red Soil with Seawater   总被引：1，自引：0，他引：1  

Mohamed?M.?Kombo  Said?A.?Vuai  Maki?Ishiki  Akira?TokuyamaEmail author 《Journal of Oceanography》2005,61(3):591-601

Contamination of acidic red soil in the coastal areas of Okinawa Islands is a serious environmental problem. This study was conducted to examine the effects of the salinity on pH and aluminum concentration when the acidic red soil interacts with seawater. Acidic red soil from Gushikawa recreation center was fractionated into bulk soil, coarse sand and silt + clay. Different weights of each fraction were equilibrated with seawater solutions. The pH and concentrations of Al³⁺, Na⁺, K⁺, Ca²⁺ and Mg²⁺ were then analyzed in the extracts. The results showed a decreasing trend of pH with increasing soil to solution ratio while the extracted Al³⁺ revealed an increasing trend. The lowest pH values were 3.85, 4.06, 4.41, 4.66 and their corresponding highest Al³⁺ concentrations were 2.50, 1.01, 0.062 and 0.036 mmolL⁻¹ in the seawater extracts, one-tenth seawater extracts, one-hundredth seawater extracts and one-thousandth seawater solution extracts, respectively. Mostly, the concentrations of Na⁺, Ca²⁺, Mg²⁺ and especially K⁺ decreased with increasing soil weight in the high salinities but showed the opposite trend in the low salinity samples. Potassium concentration decreased by 39%, 53% and 40% in the seawater extracts, one-tenth and one-hundredth seawater extracts but increased by 200% in one-thousandth seawater extracts. The coincidence of the increase in Al³⁺ and H⁺ concentrations, and the decrease of Na⁺, K⁺, Ca²⁺ and Mg²⁺ concentrations in the solutions suggests ion exchange/adsorption, while the increased patterns, particularly at low salinity could be attributed to the dissolution of the species from the soils.  相似文献   

Solubility of oxygen in the major sea salts as a function of concentration and temperature     

Frank J. Millero  Fen Huang  Arthur L. Laferiere 《Marine Chemistry》2002,78(4):125

  相似文献   

The speciation of Fe(II) and Fe(III) in natural waters     

Frank J. Millero  Wensheng Yao  Jennifer Aicher 《Marine Chemistry》1995,50(1-4)

The interactions of Fe(II) and Fe(III) with the inorganic anions of natural waters have been examined using the specific interaction and ion pairing models. The specific interaction model as formulated by Pitzer is used to examine the interactions of the major components (Na⁺, Mg²⁺, Ca²⁺, K⁺, Sr²⁺, Cl⁻, SO₄⁻, HCO₃⁻, Br⁻, CO₃²⁻, B(OH)₄⁻, B(OH)₃ and CO₂) of seawater and the ion pairing model is used to account for the strong interaction of Fe(II) and Fe(III) with major and minor ligands (Cl⁻, SO₄²⁻, OH⁻, HCO₃⁻, CO₃²⁻ and HS⁻) in the waters. The model can be used to estimate the activity and speciation of iron in natural waters as a function of composition (major sea salts) and ionic strength (0 to 3 M). The measured stability constants (K_FeX^*) of Fe(II) and Fe(III) have been used to estimate the thermodynamic constants (K_FeX) and the activity coefficient of iron complexes (γ_FeX) with a number of inorganic ligands in NaClO₄ medium at various ionic strengths: In(K_FeX/γ_Feγ_X) = InK_FeX − In(γ_FeX) The activity coefficients for free ions (γ_Fe, γ_x) needed for this extrapolation have been estimated from the Pitzer equations. The activity coefficients of the ion pairs have been used to determine Pitzer parameters (B_FeX, B_FeX⁰, C_FeX^φ) for the iron complexes. These results make it possible to estimate the stability constants for the formation of Fe(II) and Fe(III) complexes over a wide range of ionic strengths and in different media. The model has been used to determine the solubility of Fe(III) in seawater as a function of pH. The results are in good agreement with the measurements of Byrne and Kester and Kuma et al. When the formation of Fe organic complexes is considered, the solubility of Fe(III) in seawater is increased by about 25%.  相似文献   

Equilibrium and structural studies of silicon(IV) and aluminium(III) in aqueous solution. II. Formation constants for the monosilicate ions SiO(OH)₃ and SiO₂(OH)₂. A precision study at 25°C in a simplified seawater medium     

Staffan Sjberg  Agneta Nordin  Nils Ingri 《Marine Chemistry》1981,10(6)

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 -log[H⁺] 10.7 their formation does not significantly affect the evaluated formation constants. Data were analyzed with the least squares computer program LETAGROPVRID.  相似文献   

An improved model for the calculation of CO₂ solubility in aqueous solutions containing Na, K, Ca, Mg, Cl, and SO₄     

Zhenhao Duan  Rui Sun  Chen Zhu  I-Ming Chou 《Marine Chemistry》2006,98(2-4):131-139

An improved model is presented for the calculation of the solubility of carbon dioxide in aqueous solutions containing Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻, and SO₄²⁻ in a wide temperature–pressure–ionic strength range (from 273 to 533 K, from 0 to 2000 bar, and from 0 to 4.5 molality of salts) with experimental accuracy. The improvements over the previous model [Duan, Z. and Sun, R., 2003. An improved model calculating CO₂ solubility in pure water and aqueous NaCl solutions from 273 to 533K and from 0 to 2000 bar. Chemical Geology, 193: 257–271] include: (1) By developing a non-iterative equation to replace the original equation of state in the calculation of CO₂ fugacity coefficients, the new model is at least twenty times computationally faster and can be easily adapted to numerical reaction-flow simulator for such applications as CO₂ sequestration and (2) By fitting to the new solubility data, the new model improved the accuracy below 288 K from 6% to about 3% of uncertainty but still retains the high accuracy of the original model above 288 K. We comprehensively evaluate all experimental CO₂ solubility data. Compared with these data, this model not only reproduces all the reliable data used for the parameterization but also predicts the data that were not used in the parameterization. In order to facilitate the application to CO₂ sequestration, we also predicted CO₂ solubility in seawater at two-phase coexistence (vapor–liquid or liquid–liquid) and at three-phase coexistence (CO₂ hydrate–liquid water–vapor CO₂ [or liquid CO₂]). The improved model is programmed and can be downloaded from the website http://www.geochem-model.org/programs.htm.  相似文献   

The effect of ionic interaction on the rates of oxidation in natural waters     

Frank J Millero  Miguel Izaguirre  Virender K Sharma 《Marine Chemistry》1987,22(2-4)

The effect of ionic interactions on the kinetics of disproportionation of HO₂, and the oxidation of Fe(II) and Cu(I) has been examined. The interactions of O₂ with Mg²⁺ and Ca²⁺ ions in seawater increases the lifetime by 3–5 times compared to water. The effect of OH⁻ on the oxidation of Fe(II) in water and seawater shows a second degree dependence from 5 to 45°C. The effect of salinity on the oxidation of Fe(II) was found to be independent of temperature, while the effect of temperature was found to be independent of salinity. The energy of activation for the overall rate constant was found to be 7 ± 0.5 kcal mol⁻¹.The effect of pH, temperature, salinity and ionic composition on the oxidation of Cu(I) has also been examined. In NaCl solutions from 0.5 to 6 M, the log k for the oxidation was a linear function of pH (6–8) with a slope of 0.2 ± 0.05. The reaction was strongly dependent on the Cl⁻ concentration with variation of from 0.3 to 340 min from 0.5 to 6 M Cl⁻. The rates of oxidation of Cu⁺ and CuCl⁰ responsible for these effects are dependent upon ionic strength. The energy of activation for the reaction was 8.5–9.9 kcal mol⁻¹ from 0.5 to 6 M. Studies of the oxidation in various NaX salts (X = I⁻, Br⁻ and Cl⁻) give rates in the order Cl⁻ > Br⁻ > I⁻ as expected, due to complex formation of Cu⁺ with X⁻.  相似文献   

Effects of irradiance on benthic and water column processes in a Gulf of Mexico estuary: Pensacola Bay, Florida, USA   总被引：1，自引：0，他引：1  

Michael C. Murrell  Jed G. Campbell  James D. Hagy III  Jane M. Caffrey 《Estuarine, Coastal and Shelf Science》2009,81(4):501-512

We examined the effect of light on water column and benthic fluxes in the Pensacola Bay estuary, a river-dominated system in the northeastern Gulf of Mexico. Measurements were made during the summers of 2003 and 2004 on 16 dates distributed along depth and salinity gradients. Dissolved oxygen fluxes were measured on replicate sediment and water column samples exposed to a gradient of photosynthetically active radiation. Sediment inorganic nutrient (NH₄⁺, NO₃⁻, PO₄³⁻) fluxes were measured. The response of dissolved oxygen fluxes to variation in light was fit to a photosynthesis–irradiance model and the parameter estimates were used to calculate daily integrated production in the water column and the benthos. The results suggest that shoal environments supported substantial benthic productivity, averaging 13.6 ± 4.7 mmol O₂ m⁻² d⁻¹, whereas channel environments supported low benthic productivity, averaging 0.5 ± 0.3 mmol O₂ m⁻² d⁻¹ (±SE). Estimates of baywide microphytobenthic productivity ranged from 8.1 to 16.5 mmol O₂ m⁻² d⁻¹, comprising about 16–32% of total system productivity. Benthic and water column dark respiration averaged 15.2 ± 3.2 and 33.6 ± 3.7 mmol O₂ m⁻² d⁻¹, respectively Inorganic nutrient fluxes were generally low compared to relevant estuarine literature values, and responded minimally to light exposure. Across all stations, nutrient fluxes from sediments to the water column averaged 1.11 ± 0.98 mmol m⁻² d⁻¹ for NH₄⁺, 0.58 ± 1.08 mmol m⁻² d⁻¹ for NO₃⁻, 0.01 ± 0.09 mmol m⁻² d⁻¹ for PO₄³⁻. The results of this study illustrate how light reaching the sediments is an important modulator of benthic nutrient and oxygen dynamics in shallow estuarine systems.  相似文献   

Carbon cycling within the upper methanogenic zone of continental rise sediments; An example from the methane-rich sediments overlying the Blake Ridge gas hydrate deposits   总被引：1，自引：0，他引：1  

Walter S. Borowski  Charles K. Paull  William Ussler  III   《Marine Chemistry》1997,57(3-4)

Data from piston cores collected from Carolina Rise and Blake Ridge, and from many DSDP/ODP sites indicate that extreme ¹³C-depletion of methane and ΣCO₂ occurs within the uppermost methanogenic zone of continental rise sediments. We infer that ¹³C-depleted methane is generated near the top of the methanogenic zone when carbon of ¹³C-depleted ΣCO₂, produced by microbially-mediated anaerobic methane oxidation, is recycled back to methane through CO₂ reduction. Interstitial water and gas samples were collected in 27 piston cores, 16 of which penetrated through the sulfate reduction zone into methane-bearing sediments of the Carolina Rise and Blake Ridge. Isotopic measurements (δ¹³C_CH4, δ¹³C_CO2, δD_CH4, and δD_H2O) indicate that this methane is microbial in origin, produced by microbially-mediated CO₂ reduction. Methane samples form two distinct isotopic pools. (1) Methane from a seafloor seep site shows a mean δ¹³C_CH4 value of − 69 ± 2%., mirroring values found at ≥ 160 mbsf from a nearby DSDP site. (2) Twenty, areally-separated sites (sample depth, 10 to 25 mbsf) have δ¹³C_CH4 values ranging from −85 to −103%., and δ¹³C_CO2 as negative as −48%.. The very low δ¹³C values from the methane and CO₂ pools highlight the importance of carbon cycling within continental rise sediments at and near the sulfate-methane boundary.  相似文献   

Benthic fluxes of nitrogen in the tidal reaches of a turbid, high-nitrate sub-tropical river     

Perran L. M. Cook  Bradley D. Eyre  Rhys Leeming  Edward C. V. Butler   《Estuarine, Coastal and Shelf Science》2004,59(4):675-685

Benthic fluxes of dissolved inorganic nitrogen (NO₃⁻ and NH₄⁺), dissolved organic nitrogen (DON), N₂ (denitrification), O₂ and TCO₂ were measured in the tidal reaches of the Bremer River, south east Queensland, Australia. Measurements were made at three sites during summer and winter. Fluxes of NO₃⁻ were generally directed into the sediments at rates of up to −225 μmol N m⁻² h⁻¹. NH₄⁺ was mostly taken up by the sediments at rates of up to −52 μmol N m⁻² h⁻¹, its ultimate fate probably being denitrification. DON fluxes were not significant during winter. During summer, fluxes of DON were observed both into (−105 μmol m⁻² h⁻¹) and out of (39 μmol m⁻² h⁻¹) the sediments. Average N₂ fluxes at all sampling sites were similar during summer (162 μmol N m⁻² h⁻¹) and winter (153 μmol N m⁻² h⁻¹). Denitrification was fed both by nitrification within the sediment and NO₃⁻ from the water column. Sediment respiration rates played an important role in the dynamics of nitrification and denitrification. NO₃⁻ fluxes were significantly related to TCO₂ fluxes (p<0.01), with a release of NO₃⁻ from the sediment only occurring at respiration rates below 1000 μmol C m⁻² h⁻¹. Rates of denitrification increased with respiration up to TCO₂ fluxes of 1000 μmol C m⁻² h⁻¹. At sediment respiration rates above 1000 μmol C m⁻² h⁻¹, denitrification rates increased less rapidly with respiration in winter and declined during summer. On a monthly basis denitrification removed about 9% of the total nitrogen and 16% of NO₃⁻ entering the Bremer River system from known point sources. This is a similar magnitude to that estimated in other tidal river systems and estuaries receiving similar nitrogen loads. During flood events the amount of NO₃⁻ denitrified dropped to about 6% of the total river NO₃⁻ load.  相似文献   

δC and δN variations in Weddell Sea particulate organic matter     

G.H. Rau  C.W. Sullivan  L.I. Gordon 《Marine Chemistry》1991,35(1-4)

The δ¹³C and δ¹⁵N of particulate organic matter (POM) sampled from the Weddell Sea in 1986 and 1988 ranged from −30.4 to − 16.7%o and from −5.4 to +41.3%o, respectively. These large variations in POM δ¹³C and δ¹⁵N may reflect spatial/temporal changes in the concentrations and isotope abundances of CO₂(aq.) and NH₄⁺, respectively. Elevated isotope values were found exclusively in POM in or closely associated with sea ice, which may be the source of the ¹³C- and ¹⁵N-enriched sediments observed in this region.  相似文献   

Microbial photosynthesis in coral reef sediments (Heron Reef, Australia)     

Ursula Werner  Anna Blazejak  Paul Bird  Gabriele Eickert  Raphaela Schoon  Raeid M.M. Abed  Andrew Bissett  Dirk de Beer   《Estuarine, Coastal and Shelf Science》2008,76(4):876-888

We investigated microphytobenthic photosynthesis at four stations in the coral reef sediments at Heron Reef, Australia. The microphytobenthos was dominated by diatoms, dinoflagellates and cyanobacteria, as indicated by biomarker pigment analysis. Conspicuous algae firmly attached to the sand grains (ca. 100 μm in diameter, surrounded by a hard transparent wall) were rich in peridinin, a marker pigment for dinoflagellates, but also showed a high diversity based on cyanobacterial 16S rDNA gene sequence analysis. Specimens of these algae that were buried below the photic zone exhibited an unexpected stimulation of respiration by light, resulting in an increase of local oxygen concentrations upon darkening. Net photosynthesis of the sediments varied between 1.9 and 8.5 mmol O₂ m⁻² h⁻¹ and was strongly correlated with Chl a content, which lay between 31 and 84 mg m⁻². An estimate based on our spatially limited dataset indicates that the microphytobenthic production for the entire reef is in the order of magnitude of the production estimated for corals. Photosynthesis stimulated calcification at all investigated sites (0.2–1.0 mmol Ca²⁺ m⁻² h⁻¹). The sediments of at least three stations were net calcifying. Sedimentary N₂-fixation rates (measured by acetylene reduction assays at two sites) ranged between 0.9 to 3.9 mmol N₂ m⁻² h⁻¹ and were highest in the light, indicating the importance of heterocystous cyanobacteria. In coral fingers no N₂-fixation was measurable, which stresses the importance of the sediment compartment for reef nitrogen cycling.  相似文献   

Singe-ion activities in aqueous solutions analogous to seawater     

R. A. Robinson  R. G. Bates 《Marine Chemistry》1979,7(4):281-288

The method developed earlier, based on hydration numbers for individual ionic species, has been extended to aqueous systems of four electrolytes, MX, M₂Y, NX₂, and PX₂, with an unhydrated anion (X⁻). The procedure is used to calculate γ_Na, γ_Mg, γ_Ca, γ_Cl and γ_SO4 in a mixed electrolyte solution closely resembling seawater. Values of γ_K and γ_F in sea-water have also been estimated.  相似文献   

Effects of nitrogen and iron enrichments on phytoplankton communities in the Northwestern Indian Ocean     

Shigenobu Takeda  Akiyoshi Kamatani  Kyoko Kawanobe 《Marine Chemistry》1995,50(1-4)

Nutrient-enrichment bottle experiments in the northwestern Indian Ocean surface waters were conducted to investigate phytoplankton growth following enrichments with either NH₄⁺, NO₃⁻, Fe or Fe + NO₃⁻. Stimulation of phytoplankton growth could be achieved by the addition of either NH₄⁺ or NO₃⁻ under the ambient Fe concentrations, but the most significant increases in Chl a, POC, and cell densities were observed in the Fe + NO₃⁻-amended culture. Iron addition caused more rapid responses of phytoplankton growth in the Fe + NO₃⁻ treatment than those in the NO₃⁻ and NH₄⁻ treatment. However, the Fe-enrichment treatment revealed minimal growth of phytoplankton because of severe major nutrient deficiency and was similar to the control treatment. Increases in the cell density of diatoms and spherical phytoplankton cells (< 10 μm) were significant in the NH₄⁺-enriched samples, whereas NO₃⁻ enrichment alone had little effect on the diatoms. Simultaneous addition of Fe and NO₃⁻ stimulated maximal growth of phytoplankton, in particular in diatoms, coccolithophorids and Phaeocystis type colonies. However, the dominance of coccolithophorids and Phaeocystis type colonies in the Fe + NO₃⁻ treatment may be interpreted as resulting from Si-limitation. The high N/P ratio for phytoplankton nutrient uptake in the N-amended culture indicates the possibility of some P-limited growth. From these results, we conclude that in the northwestern Indian Ocean, Fe and major nutrients are co-limiting phytoplankton production during the northeast monsoon. Iron appeared to affect the ability of phytoplankton to respond quickly to transient nutrient inputs.  相似文献   

Nutrients (organic C, P, N, Si) in the eutrophic River Loire (France) and its estuary   总被引：2，自引：0，他引：2  

M. Meybeck  G. Cauwet  S. Dessery  M. Somville  D. Gouleau  G. Billen 《Estuarine, Coastal and Shelf Science》1988,27(6)

The Loire estuary has been surveyed from 1982 to 1985 by 13 isochronous longitudinal profiles realized at low tide. Nutrient (SiO₂, NO₃⁻, NH₄⁺, PO³⁻₄, particulate organic carbon or POC) patterns are very variable depending on the season, the estuarine section [river, upper-inner estuary, upstream of the fresh-water-saline-water interphase FSI, the lower-inner estuary characterized by the high turbidity zone (HTZ), the outer estuary] and the river discharge. Biological processes are dominant. In the eutrophied River Loire (summer pigment > 100 μg l⁻¹), the high algal productivity (algal POC > 3 mg l⁻¹) results in severe depletion of SiO₂, PO₄³⁻, NO₃⁻. The enormous biomass (55 000 ton algal POC/year) is degraded in the HTZ where bacterial activity is intense. As a result, there is generally a regeneration of dissolved SiO₂ and PO₄³⁻, a marked NH₄⁺ maximum, while NO₃⁻ is conservative or depleted when the HTZ is nearly anoxic. Other processes can be considered including pollution from fertilizer plans (PO₄³⁻, NH₄⁺) and from a hydrothermal power plant (NH₄⁺). In the less turbid outer estuary, nutrients are generally conservative. Major variations of concentrations are observed in the lowest chlorinity section (Cl⁻ < 1 g kg⁻) and also upstream the FSI, defined here as a 100% increase in Cl⁻. Nutrient inputs to the ocean are not significantly modified for SiO₂ and NO₂⁻, but are increased by 70% and 180% for PO₄³⁻ and NH₄⁺ and depleted by 60% for POC. Odd hydrological events, especially some floods, may perturbate or even mask the usual seasonal pattern observed in profiles.  相似文献   

海南省海岸带典型区域海水入侵现状评价     

杨坤  刘文全  徐兴永  陈广泉  刘衍君  付腾飞  王传珺  付云霞 《海洋科学》2019,43(5):57-63

基于海南省东部和南部海岸带地区地下水现场监测数据和室内水化学测定数据,研究了各水化学指标间的相关性,分析了区域海水入侵现状。研究结果表明地下水中Cl~–与Na~+的变异系数较高,与矿化度(TDS)具有强的相关性;以m(Cl~–)(m表示质量浓度)和TDS分别作为评价因子开展了海水入侵现状评价,结果表明研究区域内地下水未受到海水入侵的影响;m(Na~+)/m(Cl~–)、 m(Cl~–)/m(HCO_3~–)、m(Cl~–)/m(SO_4~(2–))、m(Ca~(2+))/m(Na~+)、m(Ca~(2+))/m(Mg~(2+))、钠吸附比(SAR)与m(Cl~–)的相关性分析结果表明m(Na~+)/m(Cl~–)、m(Ca~(2+))/m(Na~+)、m(Ca~(2+))/m(Mg~(2+))以及SAR4个参数可以作为海南省海水入侵判定的评价因子。研究结果对建设海南省"国际旅游岛"战略目标,指导当地合理利用地下水具有参考价值。  相似文献