Wave setup/setdown and longshore current on non-planar beaches

Wave-induced setup/setdown and longshore currents are examined theoretically for non-planar, concave-up beaches. A beach profile in which the still-water-depth is proportional to the horizontal distance offshore raised to the $\text{2}\text{3}$ power is examined in detail. The total mean-water-depth, which includes the sum of the still-water-depth for this $\text{2}\text{3}$ power beach profile plus the wave-induced setup/setdown, may be approximated shoreward of the breaker line in a best least-squares sense by a profile that is proportional to the horizontal distance offshore raised to the $\text{1}\text{2}$ power. The longshore current profile for this non-planar beach is found to differ significantly from that predicted analytically for a planar beach. The longshore current velocity does not vanish at the shoreline as in the planar beach case. In addition, the peak velocities and the total longshore transport of water are found to be less than for the corresponding planar beach cases. For a given concave-up beach profile, the influence of the lateral mixing increases as the wave height decreases.     

Spectral characteristics of random wave run-up

The time series of shoreline variations (run-up variations) due to random waves have been measured on uniform sloping beaches with slopes ranging from $\text{1}\text{5}$ to $\text{1}\text{30}$ and the energy spectra of the variations (run-up spectra) have been examined. The main characteristics of run-up spectra obtained from the experimental results are as follows: (1) a phenomenon of energy saturation is seen in a high frequency region; and (2) the spectral energy densities are independent of offshore incident wave energy. In the saturation region, the run-up spectra show f⁻⁴ dependence and tan ⁴θ dependence (f: frequency, tanθ: beach slope). Only in a low frequency region, the energy densities increase with increasing incident wave energy. In addition to the experimental study, it is shown by numerical simulations that if run-up variations are formed by parabolas induced by bores running up and down on the beach surface, the spectra of the variations show f⁻⁴ dependence, and the low frequency run-up energy densities increase with increasing running-up velocities of bores.     

Preliminary investigation of the surficial sediments in the Cap-Breton Canyon (southwest France) and the surrounding continental shelf

A total of 120 grab samples of the surficial sediments in the Cap-Breton submarine canyon and surrounding continental shelf were collected and analyzed by grain-size sieving. A Q-mode Factor Analysis was made on the grain-size data in order to define the most meaningful facies types. Four distinct lithological facies were found to exist: silt and clay, very fine sand, fine sand, and coarse sand. Comparison with previous work and a ¹⁴C date on the silt and clay facies showed that the facies are not contemporaneous. The sands and coarse sands on the shelf were emplaced during the pre-Würm and Würm regressions, and later probably reworked during the Holocene (Flandrian) transgression. The silty clays found in the canyon and on the shelf to the south are younger and represent sediments brought in as suspended load by the Adour and other nearby rivers during the Holocene (Flandrian) transgression.     

Longshore sediment transport on non-planar beaches

For a concave-up $\text{2}\text{3}$ power Bruun beach profile, the following two energetics-based sediment transport models are developed: (1) a Bagnold-type model and (2) a combined wave-current stress model. The stress model is calibrated with the Bagnold model using observed transport rates on planar beaches. The sediment transport profiles for the two models are in agreement within the surf zone for the planar beach case; but the stress model is also applied seaward of the breaker line where the Bagnold model is not. A mean swash transport of sand is predicted by the Bagnold model for a $\text{1}\text{2}$ power least-squares approximation to total depth including setup/setdown on a Bruun beach profile. The total longshore transport of sand is determined for each transport model as a function of the turbulent lateral mixing strength. The total sand transport is found to be less on a concave-up beach profile than for the corresponding planar beach case.     

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 ($\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{< 40 h}$).     

山东半岛东部南北岸典型砂质海岸沉积、地貌的横向差异及成因分析———以海阳万米海滩岸段和威海国际海水浴场岸段为例

根据2011年在海阳万米海滩岸段与威海国际海水浴场岸段调查获得的夏、冬两季海岸实测地形剖面与沉积物粒度数据,并收集相关水文资料,对南北两海岸地貌与沉积差异性进行分析,探讨了半岛东部南北岸典型砂质海岸动力环境的差异。研究结果表明,南部海岸宽广平缓,发育滩脊、滩肩、沙波纹等地貌,沉积物在水下岸坡上段以中粗砂、中细砂为主,水下岸坡以下段以粉砂、黏土质粉砂为主;北部海岸地形陡,发育滩肩陡坎、水下沙坝等地貌,沉积物以砾质砂为主。导致这些差异的动力为风、波浪、潮汐及沿岸流堆积。     

Horizontal and vertical cylinders in waves

The present investigation examines a vertical cylinder and a horizontal cylinder in progressive waves. The physical differences between the flows are explored and experimental results are compared to previous planar harmonic flow measurements. It is found that modifications to the usual Morison approach are required in some cases to adequately account for the orbital motions of the fluid and to account for the orientation of the orbits with respect to the cylinder axis. The axial variations of the wave force on vertical cylinders are considered in order to evaluate the common practice of assuming constant values of $\text{C}{}_{\mathrm{m}}\text{and}\text{C}{}_{\mathrm{D}}$ over the entire span. Lastly, the methods of computing force transfer coefficients from a force record are examined and several sources of error are identified and briefly discussed.     

Deuterium content of humic acids from marine and non-marine environments

Deuterium values obtained for humic acids isolated from marine sediments from the NE Pacific are in the range of $\text{δ}\text{D}\text{= (?105 ± 5)‰}$, corresponding to values obtained for marine plankton from the same area. Soil humic acids have a much broader range of δD values (?57 to ?97‰), depending on the isotopic values of the precipitation and the isotopic composition of the parent plant precursor.Data obtained on hydrogen isotope distribution confirms previous hypotheses based on chemical analysis and on carbon isotopes, which indicated the authigenic nature of marine humates.     

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.     

Geochemistry of manganese deposits in relation to environment on the sea floor around southern Africa

Manganese deposits from the Madagascar Basin, the Crozet Basin and the basins west of the Madagascar Ridge around southern Africa differ chemically from one another. This appears to be largely because of differences in the degree of oxygenation of the environment; most highly oxidizing is the Madagascar Basin, where the $\text{Mn}\text{Fe}$ ratio is very low and where the manganese deposits probably consist largely of “birnessite”.Continental-margin samples differ from basin samples in having higher $\text{Mn}\text{Fe}$ ratios, probably because of diagenetic remobilization processes within the sediment column. The ratios of Mn and Fe to certain metals ($\text{Mn}\text{Ni}$, $\text{Mn}\text{Zn}$, $\text{Fe}\text{Co}$ and $\text{Fe}\text{As}$) are the opposites of those found in other continental-margin environments, suggesting either a difference in the diagenetic process, or an additional metal source, off southern Africa. Both seawater and bottom sediments of the southern African margin are metal-enriched, and could act as sources of metals for growing manganese nodules and encrustations.     

茅家港突堤工程建造前后滩面沉积物粒度变化及其原因分析

为研究茅家港附近岸滩面沉积物粒度的变化,在对茅家港近岸滩面沉积物粒度研究的基础上,于1993年9月、1994年1月进行了两次野外采样调查,在室内进行了粒度测量.通过测得的一手资料,绘出不同时间的粒度空间分布图和不同位置的剖面图,对茅家港滩面沉积物粒度的空间分布、季节变化及其反映的水动力变化和原因进行了分析研究,论述了茅家港工程建造前后滩面沉积物粒度变化的规律和原因.研究发现：工程建成后,因突堤内水动力减弱,突堤内滩面沉积物的粒度变细,且比突堤外的细,航道不再淤积,使航道的位置和深度稳定,有效地保护了航道;随着离岸距离增加,因水动力逐渐增强,滩面沉积物的粒径逐渐变粗;因冬季的水动力比夏季的水动力强,冬季滩面沉积物粒度比夏季粗.     

Tectonically induced deformation of deep-sea sediments off Washington and northern Oregon: Mechanical consolidation

Convergent motion of the North American and Juan de Fuca plates has resulted in deformation of Cascadia Basin sediments and accretion of these deposits to the North American continental margin. The accreted deposits, which occur as anticlinal ridges and thrust blocks, constitute the lower continental slope or borderland off Washington and northern Oregon. Over the past 2.0 m.y., approximately 30 km of this deformed material has been added to the lower slope, removing undeformed deposits from Cascadia Basin at a rate of 2.3–2.9 cm/yr.Near-surface sediments involved in this accretionary process are mechanically consolidated: muds?tones dredged from the lower slope exhibit physical properties (water contents, 20–47%; void ratios, 0.4–1.2; preconsolidation pressures, 0.8–8.2 MPa) which differ significantly from properties of similar, but undeformed sediments (water contents, 50–250%; void ratios, 1.1–1.9). While some consolidation may be attributable to prior burial ($\text{< 2.0}\text{MPa}$) or carbonate precipitation, neither mechanism can wholly account for the values observed. It appears that most of the consolidation has occurred in response to tectonically induced overpressures.Initial consolidation occurs rapidly across a narrow ($\text{< 3}\text{km}$) front, defined by the base of the continental slope. Further consolidation and dewatering appears to take place, at a much reduced rate, over the entire width of the lower slope.Development of foliation is nearly ubiquitous in the deformed mudstones. This property limits the strength of the deposits (shear strengths, 90–416 kPa) and movement along these planes probably accommodates much of the strain after initial consolidation.The physical properties characteristic of Washington—Oregon deformed sediments may represent limiting values for mechanical consolidation of near-surface terrigenous sediments under horizontal stress.     

淤泥质海床相邻的岬湾沙滩剖面特征研究

通过对浙江沿海岬角海湾沙滩多处典型剖面的调查,结果表明沙滩与淤泥质海床存在较明显的沙泥分界线,滩面物质自北至南,粒径差别不大,中值粒径在0.15~0.25mm之间,滩面基本呈现单一坡度,坡度为1∶15~1∶30,沙滩坡度与波浪动力相关,沙滩前沿波浪动力强,滩面较缓,反之滩面较陡。沙滩退化表现为滩面的截断、粗化和泥化,滩面截断导致沙滩面积减少,中、细沙供给不足;细沙采挖或局部工程导致的沿岸输沙动力条件的改变会使滩面物质变粗;岬湾的水动力条件减弱,易使沙泥分界线抬升,局部泥化;过度挖沙会导致沙滩消失成为泥滩。     

Composition of Pacific Ocean ferromanganese nodules

Bulk composition of ferromanganese nodules from the pelagic environment of the Pacific Ocean is apparently related to nodule-growth rate, sediment-accumulation rate, and biologic productivity in the overlying seawater. Nodules with a high $\text{Mn}\text{Fe}$ ratio and high Ni and Cu concentrations tend to occur in areas where primary productivity in the surface layer of the ocean is high and the sediment-accumulation rate low. Nodules with a low $\text{Mn}\text{Fe}$ ratio and low Ni and Cu concentrations occur in areas either where sediment-accumulation rate is high or biologic productivity is low. They may have a $\text{Mn}\text{Fe}$ ratio as low as one and accrete at rates as low as $\text{1}\text{mm}\text{10}{}^6\text{yrs}$. Nodules with a larger $\text{Mn}\text{Fe}$ ratio apparently have growth rates that are greater by as much as a factor of 10.     

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.