An automated photochemical method for the determination of dissolved organic carbon in sea and estuarine waters     

K.J. Collins  P.J. Le  B. Williams 《Marine Chemistry》1977,5(2):123-141

An improved version of Ehrhardt's (1969) method for the analysis of dissolved organic carbon is described. The method, which is automated, determines the carbon dioxide with a non-dispersive infra-red analyser. The conditions of photo-oxidation have been examined in order to achieve maximum performance. It was found that careful attention needed to be paid to U-V source, “oxygen source”, pH and time or irradiation. The completeness of the method was examined by three independent procedures. We concluded that in all cases the extent of oxidation of organic material was in excess of 98%. Typical performance figures were: precision ±2.5% above 2.0 mg C l^?1, approaching 0.03 mg C l^?1 below 1.0 mg Cl^?1; blank, equivalent to 0.3 mg C l^?1; sampling frequency, 10 samples per hour. The lower limit of sensitivity is mainly governed by the blank. The upper limit of the method is greater than 40 mg C l^?1.A wholly continuous modification of the method has been devised which permits on line analyses. An attentuated version of the method has been used for the analysis of total carbonate.The present and other published methods for the analysis of dissolved organic carbon in natural waters are discussed in relation to one another.  相似文献   

Initial grain motion under oscillatory flow: A comparison of some threshold criteria     

J. K. Rigler  M. B. Collins 《Geo-Marine Letters》1984,3(1):43-48

Experimental data are described on the threshold of transport of quartz, ilmenite, and cassiterite grains under oscillatory flow in a flume and the results are compared to those of other investigators. The results show that for a given particle size, critical shear stress (τ_crit) increases with increasing wave period and that τ_crit increases with both grain size and grain density. These data are compared with prediction equations.  相似文献   

Number of tracers required for the measurement of longshore transport distance on a shingle beach     

M.W.E. Lee  D.A. Sear  P.M. Atkinson  M.B. Collins  R.J. Oakey 《Marine Geology》2007,240(1-4):57-63

The aim of this study was to identify a method for determining the number of tracer particles required to define the mean longshore transport distance of indigenous littoral shingle with a particular level of precision. A method is presented which can be applied to existing tracer data to determine both the precision of the measurements collected and the number of tracers required to achieve a particular level of precision. The method, which utilises well established statistical relationships, is demonstrated by applying it to archive tracer data. The study demonstrates the sensitivity of the number of tracers to the variance of the transport distances of indigenous particles at the site and the precision with which the investigator wishes to define the mean. It is anticipated that application of the method by other practitioners, in the future, will allow a dataset to develop which can be used alongside the method presented here to allow the number of tracers required for a study to be estimated prior to entering the field. Results are presented to initiate the development of this dataset and a “look-up chart” derived using the method is given to aid its application.  相似文献   

Initial grain motion under oscillatory flow: A comparison of some threshold criteria     

J. K. Rigler  M. B. Collins 《Geo-Marine Letters》1983,3(1):43-48

Experimental data are described on the threshold of transport of quartz, ilmenite, and cassiterite grains under oscillatory flow in a flume and the results are compared to those of other investigators. The results show that for a given particle size, critical shear stress (τ_crit) increases with increasing wave period and that τ_crit increases with both grain size and grain density. These data are compared with prediction equations.  相似文献   

Ecosystem-based management of fisheries: is science limiting?   总被引：4，自引：0，他引：4  

Frid  Chris L.J.; Paramor  Odette A.L.; Scott  Catherine L. 《ICES Journal of Marine Science》2006,63(9):1567-1572

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Side-scan sonar investigation into temporal variation in sand wave morphology: Helwick sands,Bristol Channel     

P. T. Harris  M. B. Collins 《Geo-Marine Letters》1984,4(2):91-97

The morphology and mobility of bedforms within a sand wave field having a water depth of 30 to 40 m have been studied by side-scan sonar surveys at different tidal stages and under various wave climates. Large sand waves with heights of 4 to 7 m retained their orientation throughout the survey period, Small sand waves with heights less than 2 to 3 m changed their height over a tidal cycle and their location (relative to larger sand waves) between surveys. The maximum change appeared to be related to ebb current acceleration. Megaripple wavelengths were reduced under surface wave action.  相似文献   

Dispersion of bauxitic red mud in the Gulf of Corinth, Greece     

Soterios Varnavas  George Ferentinos  Michael Collins 《Marine Geology》1986,70(3-4):211-222

Bauxitic red-mud slurry, discharged by an aluminium processing factory on the shelf of the Gulf of Corinth, Greece, is used as a tracer to examine sediment transport and dispersion processes in a tectonically active deep basin.

The Gulf of Corinth is a silled elongate basin with a maximum depth of 860 m; it is characterised by high seismicity. The red mud is discharged through a pipeline at a depth of 100 m, where it forms an extensive deposit.

Grab sampling has shown that the red mud extends over the slope and the abyssal plain up to a distance of 17 km from the mouth of the pipeline. It forms small scattered sheet-like deposits of up to 3 cm in thickness. The structures observed in the scattered patches of the red mud, which in some places are overlain by a thin veneer of grey/olive green (natural) sediments, suggest that the red mud is transported from the shelf to the abyssal plain by gravitative sediment flows. The flows are triggered by earthquakes.

Granulometric and geochemical analyses of the red-mud samples show that the red mud, during its transport from the shelf to the abyssal plain, is subjected to mixing with the surrounding sediments. A different mixing ratio is determined, however, by reference to the various trace metals (Fe, Ni, Co, Pb).  相似文献   

Hydrography, nutrients and chlorophyll during El Niño and La Niña 1997–99 winters in the Gulf of the Farallones, California     

F. P. Wilkerson  R. C. Dugdale  A. Marchi  C. A. Collins 《Progress in Oceanography》2002,54(1-4)

Nutrient and chlorophyll concentrations were measured in January 1997, 1998 and 1999 in the Gulf of the Farallones, CA at locations stretching north/south from Point Reyes to Half Moon Bay, and seaward from the Golden Gate to the Farallon Islands. The cruises were all carried out during periods of high river flow, but under different climatological conditions with 1997 conditions described as relatively typical or ‘neutral/normal’, compared to the El Niño warmer water temperatures in 1998, and the cooler La Niña conditions in 1999. Near-shore sea-surface temperatures ranged from cold (9.5–10.5°C) during La Niña 1999, to average (11–13°C) during 1997 to warm (13.5–15°C) during El Niño 1998. Nutrients are supplied to the Gulf of the Farallones both from San Francisco Bay (SFB) and from oceanic sources, e.g. coastal upwelling near Point Reyes. Nutrient supplies are strongly influenced by the seasonal cycle of fall calms, with storms (commencing in January), and the spring transition to high pressure and northerly upwelling favorable winds. The major effect of El Niño and La Niña climatic conditions was to modulate the relative contribution of SFB to nutrient concentrations in the coastal waters of the Gulf of the Farallones; this was intensified during the El Niño winter and reduced during La Niña. During January 1998 (El Niño) the oceanic water was warm and had low or undetectable nitrate, that did not reach the coast. Instead, SFB dominated the supply of nutrients to the coastal waters. Additionally, these data indicate that silicate may be a good tracker of SFB water. In January, delta outflow into SFB produces low salinity, high silicate, high nitrate water that exits the bay at the Golden Gate and is advected northward along the coast. This occurred in both 1997 and 1998. However during January 1999, a La Niña, this SFB feature was reduced and the near-shore water was more characteristic of high salinity oceanic water penetrated all the way to the coast and was cold (10°C) and nutrient rich (16 μM NO₃, 30 μM Si(OH)₄). January chlorophyll concentrations ranged from 1–1.5 μg l⁻¹ in all years with the highest values measured in 1999 (2.5–3 μg l⁻¹) as a result of elevated nutrients in the area. The impact of climatic conditions on chlorophyll concentrations was not as pronounced as might be expected from the high temperatures and low nutrient concentrations measured offshore during El Niño due to the sustained supply of nutrients from the Bay supporting continued primary production.  相似文献   

An ecosystem model of food web and fisheries interactions in the Baltic Sea   总被引：8，自引：1，他引：8  

Harvey  Chris J; Cox  Sean P; Essington  Timothy E; Hansson  Sture; Kitchell  James F 《ICES Journal of Marine Science》2003,60(5):939-950

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Multigrain sedimentation/erosion model based on cross-shore equilibrium sediment distribution: Application to nourishment design     

Fangjun Li  Chris Dyt  Cedric Griffiths 《Estuarine, Coastal and Shelf Science》2006,67(4):664-672

In the light of global warming and sea level rise there are many coastal beaches that suffer from erosion. Beach nourishment has become a common practice to maintain the sediment balance on a shore-face. In this paper, a three-dimensional numerical model for evaluating long-term impact of beach nourishment projects has been developed. The model addresses the longstanding complex issue of coastal morphology and sediment grain size distribution from an unconventional angle, which exploits the strong links between grain size distribution and the prevailing transport direction of each sediment constituent under ‘average’ wave and storm action. The present model predicts the redistribution of nourished sediment according to the subtle clues implied by equilibrium distribution curves and latest coastal wave transformation theories. After verification against recent field observations in Terschelling, The Netherlands, the model was used to predict long-term effects of different beach nourishment strategies. It was found that: (a) given the source sediment available in Terschelling the tactics of large volume and less frequent implementation are better than otherwise; and (b) from a pure engineering point of view, waterline nourishment outperforms offshore trough nourishment.The model offers an additional tool for coastal engineers to evaluate the feasibility, effectiveness and the optimization of dumping locations for beach nourishment projects. It is also a useful tool for stratigraphic modelling of shallow-marine sedimentation in conjunction with sea level changes.  相似文献