Nitrogen and phosphorus concentrations within North Inlet,South Carolina—Speculation as to sources and sinks

The daily concentrations of $\text{NH}{}_4{}^{\mathrm{+}}$, $\text{NO}{}_3{}^{\mathrm{?}}$, and $\text{NO}{}_3{}^{\mathrm{?}}\text{+ NO}{}_2{}^{\mathrm{?}}$ 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.     

Nitrogen losses from a Louisiana Gulf Coast salt marsh

Losses of ¹⁵N labelled nitrogen in a Spartina alterniflora salt marsh was measured over three growing seasons. Labelled $\text{NH}{}_4{}^{\mathrm{+}}\text{N}$ 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 $\text{NH}{}_4{}^{\mathrm{+}}\text{N}$ 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 $\text{NH}{}_4{}^{\mathrm{+}}\text{N}$ 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.     

Nitrogen uptake,ammonium oxidation and nitrous oxide (N2O) levels in the coastal waters of western Cook Strait,New Zealand

Vertical measurements of $\text{NH}{}_4{}^{\mathrm{+}}$, $\text{NO}{}_3{}^{\mathrm{?}}$ and N₂O concentrations, $\text{NO}{}_3{}^{\mathrm{?}}$ and $\text{NH}{}_4{}^{\mathrm{+}}$ uptake, and $\text{NH}{}_4{}^{\mathrm{+}}$ 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 $\text{NO}{}_3{}^{\mathrm{?}}\text{N l}{}^{\mathrm{?1}}$ at the most strongly stratified station whereas $\text{NH}{}_4{}^{\mathrm{+}}$ was relatively constant with depth at all stations (～0.1 μg-atom $\text{NH}{}_4{}^{\mathrm{+}}\text{N l}{}^{\mathrm{?1}}$). The highest rates of $\text{NH}{}_4{}^{\mathrm{+}}$ 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. $\text{NH}{}_4{}^{\mathrm{+}}$ oxidation by nitrifying bacteria may account for about 30% of the total $\text{NH}{}_4{}^{\mathrm{+}}$ utilization (i.e. bacterial+agal) and, assuming oxidation through to $\text{NO}{}_3{}^{\mathrm{?}}$, may supply about 40% of the algal requirements of $\text{NO}{}_3{}^{\mathrm{?}}$ 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.     

Inhibition of sulphate reduction in anoxic marine sediment by Group VI anions

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 $\text{(MoO}{}_4{}^{\mathrm{=}}\text{)>selenate(SeO}{}_4{}^{\mathrm{=}}\text{)>tungstate(WO}{}_4{}^{\mathrm{=}}\text{)}$. 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 $\text{SeO}{}_4{}^{\mathrm{=}}$ and $\text{WO}{}_4{}^{\mathrm{=}}$ treated slurries whereas no such reversal was noticed with $\text{MoO}{}_4{}^{\mathrm{=}}$. These observations suggested that $\text{SeO}{}_4{}^{\mathrm{=}}$ and $\text{WO}{}_4{}^{\mathrm{=}}$ are competitive inhibitors of sulphate reduction, while $\text{MoO}{}_4{}^{\mathrm{=}}$ is a non-competitive inhibitor.     

Sodium fluoride ion-pairs in seawater

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°, $\text{K}{}^1{}_{\mathrm{<mtext>NaF</mtext>}}$, was determined at 15, 25, and 35°C. It was assumed that $\text{K}{}^1{}_{\mathrm{<mtext>NaF</mtext>}}$ was a function of temperature, pressure, and ionic strength but not of solution composition. The value for $\text{K}{}^1{}_{\mathrm{<mtext>NaF</mtext>}}$ at 25°C and I = 0.7 m is 0.045 ± 0.006. $\text{K}{}^1{}_{\mathrm{<mtext>NaF</mtext>}}$ increased with decreasing temperature. This result was used to recompute values of $\text{K}{}^1{}_{\mathrm{<mtext>MgF</mtext>}}$ and $\text{K}{}^1{}_{\mathrm{<mtext>CaF</mtext>}}$ accounting for the presence of NaF° ion-pairs. The value for $\text{K}{}^1{}_{\mathrm{<mtext>NaF</mtext>}}$ 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.     

The density and expansibility of artificial seawater solutions from 0 to 40°C and 0 to 21‰ chlorinity

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, $\text{d = d}{}^0\text{+}\text{A}{}_{\mathrm{V}}\text{′ Cl}{}_{\mathrm{V}}\text{+ B}{}_{\mathrm{V}}\text{′ Cl}{}_{\mathrm{V}}{}^{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ and an equation based on the Debye-Hückel limiting law, $\text{d = d}{}^0\text{+}\text{A}{}_{\mathrm{V}}\text{Cl}{}_{\mathrm{V}}\text{+ B}{}_{\mathrm{V}}\text{Cl}{}_{\mathrm{V}}{}^{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{+ C}{}_{\mathrm{V}}\text{Cl}{}_{\mathrm{V}}{}^2$ where A_V′, B_V′, A_V, B_V and C_V 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 Cl_V is the volume chlorinity — $\text{Cl}{}_{\mathrm{V}}\text{= Cl (‰) × density}$. 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 $\text{α = α}{}^0\text{+}\text{A}{}_{\mathrm{E}}\text{′ Cl}{}_{\mathrm{V}}\text{+ B}{}_{\mathrm{E}}\text{′ Cl}{}_{\mathrm{V}}{}^{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ and $\text{α = α}{}^0\text{+}\text{A}{}_{\mathrm{E}}\text{Cl}{}_{\mathrm{V}}\text{+ B}{}_{\mathrm{E}}\text{Cl}{}_{\mathrm{V}}{}^{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{+ C}{}_{\mathrm{E}}\text{Cl}{}_{\mathrm{V}}{}^2$ where A_E′, B_E′, A_E, B_E and C_E 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.     

Uptake of nitrogenous nutrients by phytoplankton in a barrier Island estuary: Great South Bay,New York

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 $\text{NO}{}_3{}^{\mathrm{?}}\text{NH}{}_4{}^{\mathrm{+}}$ 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.     

Landward migration of inner bars

A field investigation was carried out to collect data of inner bar migration. Profiles were measured once or twice a week for a two-year period at Naka Beach, Ibaraki Prefecture, Japan. It was found that the onshore migration of inner bars could be described by two dimensionless quantities as: $\text{5D}\text{(H}{}_{\mathrm{<mtext>b</mtext>}}\text{)}{}_{\mathrm{<mtext>max</mtext>}}\text{<}\text{(H}{}_{\mathrm{<mtext>b</mtext>}}\text{)}{}_{\mathrm{<mtext>max</mtext>}}\text{gT}{}^2{}_{\mathrm{<mtext>max</mtext>}}\text{<}\text{20D}\text{(H}{}_{\mathrm{<mtext>b</mtext>}}\text{)}{}_{\mathrm{<mtext>max</mtext>}}$ where (H_b)_max is the maximum value of daily average breaker height during one interval between surveys, T_max is the average wave period of the day giving (H_b)_max, D is the mean size of the beach sediment, and g is the acceleration due to gravity. Analyses based on surfzone sediment dynamics yields $\text{v}\text{?}\text{(}\text{wD}\text{b}\text{)}\text{= 2 × 10}{}^{\mathrm{?11}}\text{(}\text{(}\text{H}\text{?}{}_{\mathrm{<mtext>b</mtext>}}\text{D}\text{)}{}^3$, where $\text{v}\text{?}$ is the average speed of onshore bar-migration, b is the bar height, $\text{H}\text{?}{}_{\mathrm{<mtext>b</mtext>}}$ is the average breaker height, and w is the fall velocity of the beach sediment. Nomographs for the speed of landward migrating bars are also presented.     

Equilibrium and structural studies of silicon(iv) and aluminium(iii) in aqueous solution. V. Acidity constants of silicic acid and the ionic product of water in the medium range 0.05–2.0 M Na(CI) at 25°C

The apparent ionization constants for silicic acid, k₁ and k₂, and the ionic product of water, k_w, 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

$\text{log}\text{k}{}_{\mathrm{i}}\text{=}\text{log}\text{K}{}_{\mathrm{i}}\text{+a}{}_{\mathrm{i}}\text{I}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(1+I}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{)+b}{}_{\mathrm{i}}\text{I}$

where K₁ is the ionization constant in pure water, α_i and b_i are parameters of which b_i has been adjusted to present data. The following results were obtained (α_i, b_i): pK₁ = 9.84, (1.022, ?0.11); pK₂ = 13.43, (2.044, ?0.20); and pK_w = 14.01 (1.022, ?0.22). k_i 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

$\text{Na}{}^{\mathrm{+}}\text{+}\text{SiO(OH)}{}^{\mathrm{?}}{}_3\text{?}\text{NaSiO(OH)}{}_3\text{;k}{}_{11}$

$\text{Na}{}^{\mathrm{+}}\text{+}\text{SiO}{}_2\text{(OH)}{}^2{}_2\text{?}\text{NaSiO}{}_2\text{(HO)}{}^{\mathrm{?}}{}_2\text{; k}{}_{21}$

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.     

The significance of oxygen as oxides and hydroxides in controlling the abundance and residence times of elements in seawater

A model is presented which signifies the role of oxygen (as oxides and hydroxides) in controlling the composition of seawater. Using the regression equations

$\text{log}\text{K}{}_{\mathrm{SW}}\text{=-0.77+0.03ΔO}{}^{\mathrm{2-}}\text{M}\text{and}\text{[M]}{}_{\mathrm{SW}}\text{=K}{}_{\mathrm{SW}}\text{[M]}{}_{\mathrm{crust}}$

$\text{log}\text{t}\text{=4.73+0.04ΔO}{}^{\mathrm{2-}}\text{M}$

respective concentration and residence times for the unknown elements can be estimated. Geometric and statistical indices of Legget and Williams (1981) are used to evaluate the accuracy of the model. This reveals from the known values of ΔO^2?M that the present model estimates log $\text{t}{}_{\mathrm{y}}$ values within a factor of 1.77. The predicted oceanic residence times for Am, Ir, Ra and Rh are 3.6 × 10², 3.7 × 10², 2.2 × 10⁵ and 6.4 × 10² years, respectively.     

Copper(II) interaction with carbonate species based on malachite solubility in perchlorate medium at the ionic strength of seawater

Equilibrium constants for copper(II)-carbonate and -bicarbonate species have been determined at 25°C from consideration of malachite, Cu₂(OH)₂CO_3(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 (TA_i 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.     

Tracing flocculent industrial and domestic sewage transport on San Pedro Shelf,Southern California,by nitrogen and sulphur isotope ratios

Domestic and industrial sewage is discharged at a depth of 60 m near Whites Point on the San Pedro Shelf, Southern California borderland. A density-stratified thermocline, above the outfall at a depth of 20 to 30 m, is thought to prevent most effluent particles from reaching shallower depths and recreational facilities. In this investigation, measurement of the natural abundance of nitrogen isotopes (${}^{15}\text{N}{}^{14}\text{N}$) is used to determine the level of sewage contribution to flocculent suspended material persisting at water depths of 7, 13 and 20 m. Organic nitrogen at 20 m depth was shown to be predominantly of sewage-origin and at 7 m, predominantly of marine origin. Organic nitrogen at 13 m depth and within 3 km of the outfall pipes is predominantly sewage in origin.Stable isotope composition of sulphur (${}^{32}\text{S}{}^{34}\text{S}$) in the flocculent material indicates that the effluent particles contain metabolic sulphur, incorporated from dissolved seawater, as well as bacterially produced mineral sulphide.     

MgSO4 ION association in seawater

Examination of the consequences of the stoichiometric association constant $\text{K}{}^1{}_{\mathrm{<mtext>a</mtext>}}\text{= 41.7}$ for MgSO₄ in seawater as advocated by Johnson and Pytkowicz (1979) leads to a thermodynamic association constant K_a = 212.6, a value 32% greater than K_A = 160 derived from conductance data. Use of K_a = 160 leads to a $\text{K}{}^1{}_{\mathrm{<mtext>a</mtext>}}$ in essential agreement with the value of 10.2 reported by Kester and Pytkowicz (1969).     

A potentiometric study of ferric ion complexes in synthetic media and seawater

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 ${}^1\text{β}{}_1\text{and}{}^1\text{β}{}_2$ 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 ${}^1\text{β}{}_1\text{= 1.93 · 10}{}^{\mathrm{?3}}\text{and}{}^1\text{β}{}_2\text{= 8.6 · 10}{}^{\mathrm{?8}}$. 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.     

Nitrate photolysis in seawater by sunlight

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 $\text{NO}{}_3{}^{\mathrm{?}}\text{+}\text{h}\text{υ =}\text{NO}{}_2{}^{\mathrm{?}}\text{+ O(}{}^3\text{P)}$ 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.     

Characterisation of domestic and industrial sewage in Southern California coastal sediments using nitrogen,carbon, sulphur and uranium tracers

A degradation-mixing model has been developed to aid in the interpretation of geochemical processes occurring in sewage-contaminated marine sediment near San Pedro, California. The nitrogen isotope ratio (${}^{15}{}^{14}\text{N}$) is shown to be an effective tracer of sewage discharge-on the San Pedro Shelf. Isotopic fractionation of ${}^{15}\text{N}{}^{14}\text{N}$ during release of amino compounds or ammonia (as a consequence of bacterial degradation of organic detritus) appears to be negligible. The nitrogen isotope ratio, therefore, may be considered a conservative component for tracing the source of organic matter deposited in marine sediment.Uranium enrichment from seawater is shown not to occur in the highly reducing sewage-contaminated sediments. The content of uranium in the effluent particulates (18 ppm) is large compared with the content in the uncontaminated sediment (3 to 5 ppm). This allows the content of uranium to also be used as a tool for tracing the deposition of sewage particles in marine sediment. Uranium and nitrogen are shown to be incorporated in the organic fraction of sewage effluent and are released during bacterial degradation of the organic matter. Cadmium and sulphur are shown not to be mobilised during sewage deposition and degradation. The stable isotope ratio of sulphur (${}^{34}\text{S}{}^{32}\text{S}$) is used to demonstrate that sulphur enrichment occurs in the sediment by in situ reduction of seawater sulphate. The data summarised by Morel et al. (1975) are presented and discussed in accordance with the above model.     

Solubility of hydrous ferric oxide and iron speciation in seawater

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 ${}^1\text{K}{}_{\mathrm{<mtext>so</mtext>}}\text{=}\text{[Fe}{}^{\mathrm{3+}}\text{][H}{}^{\mathrm{+}}\text{]}{}^{\mathrm{?3}}\text{= 4.7 · 10}{}^5$. 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 ${}^1\text{β}{}_3\text{=}\text{[Fe(OH)}{}_3{}^0\text{] [H}{}^{\mathrm{+}}\text{]}{}^3\text{/[Fe}{}^{\mathrm{3+}}\text{] = 2.4 · 10}{}^{\mathrm{?14}}$. 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.     

The estimation of acid dissociation constants in sea-water media from potentiometric titrations with strong base. II. The dissociation of phosphoric acid

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):

$\text{pK}{}_{\mathrm{1P}}\text{=}\text{-75}\text{T}\text{+2.16-0.35I}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(}\text{rmsdeviation 0.034}\text{)}$

$\text{pK}{}_{\mathrm{2P}}\text{=}\text{737.6}\text{T}\text{++4.176-0.851I}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(}\text{rmsdeviation 0.015}\text{)}$

$\text{pK}{}_{\mathrm{3P}}\text{=}\text{2404}\text{T}\text{+1.31-0.87I}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(}\text{rmsdeviation 0.17}\text{)}$

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.     

Behaviour of no. 2 fuel oil in the water column of controlled ecosystems

Four experiments were carried out to determine the effect of different temperatures, light levels and biological activities on the residence times of petroleum hydrocarbons. No. 2 fuel oil was added as a seawater dispersion to give an initial concentration of 150 to 300 μg/litre in the water columns of large, outdoor marine microcosms. Hydrocarbons in water samples fractionated on passage through glass fibre filters (0·3 μm pore size) according to the solubilities, so that 80–90 % of the aromatics entered the filtrate while all of the saturates were trapped by the filter. The removal of oil compounds from the water columns was exponential, with rates which appeared to be determined chiefly by the temperature. The half life of total hydrocarbons varied from more than 10 days in March to ～30 h in July and September. Volatilisation was hypothesised to be an important removal mechanism for the 40–60% of the saturates which were not sedimented with suspended particulate matter. In warm water, the residence times of normal alkanes were increased up to 50 % by poisoning the water column, but no similar increase was noted for the bulk of the F₁ hydrocarbons. Aromatic (F₂) hydrocarbons appeared to be removed slowly volatilisation from cold water ($\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{> 200 h}$) and rapidly by biodegradation from warm water ($\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{< 40 h}$).