Hydrocarbon concentrations in water and sediments from UK marine waters,determined by fluorescence spectroscopy

Between January 1978 and September 1979 samples of subsurface (1 m) water and surface sediment were collected from sites in the North Sea, English Channel, Irish Sea and a number of estuarine areas. These have been analysed by fluorescence spectroscopy (UVF) in order to provide information on the levels of hydrocarbons generally present in UK marine waters.Total hydrocarbon concentrations (THCs) of water samples ranged from 1.1–74 μg l.^?1 Ekofisk crude oil equivalents, all values greater than 3.5 μg l.^?1 occurring inshore. In offshore areas the mean THCs were: 1.3 μg l.^?1 in the northern North Sea, 1.5 μg l.^?1 in the western Channel, 2.5 μg l.^?1 in the eastern Channel and southern North Sea, and 2.6 μg l.^?1 in the Irish Sea.THCs of sediment samples ranged from 0.27–340 μ g^?1 dry weight Ekofisk crude oil equivalents, the highest concentration being in the Queen's Channel, the main entrance to the River Mersey.     

Trace metals in the northern North Sea

Cadmium, lead and copper have been determined in the dissolved and particulate phase for surface waters of the northern North Sea. Dissolved cadmium and copper show concentration gradients associated with salinity fronts which mark the boundary between coastal and ocean waters; lead does not. The particulate phase is shown to represent only a small fraction of the total metal concentration. Processes likely to be responsible for the observed distribution are discussed.     

Windscale radiocaesium in the Clyde sea area

Radiocaesium, introduced into coastal waters in the effluent from the B.N.F.L. nuclear fuel reprocessing plant at Windscale, is present at significant levels throughout the Clyde Sea Area. Concentrations reached maximum in April, 1977, and have recently declined. Around 30% of Windscale radiocaesium output passes through the Clyde Sea Area but less than 0.3% remains in sediments. There appears to be no major radiological safety hazard. The radiocaesium is, however, an excellent tracer species for both waters and sediments. The Irish Sea-derived component comprises over 90% of Clyde seawater and may well introduce major inventories of pollutants. The average water residence time in the Clyde system is 4.5 months, although significantly longer entrainment is evident in northern sea lochs. Study of radiocaesium variations has enabled improved assessment of the Clyde's response to marine pollution.     

Distribution and content of different artifical radio nuclides in the water of the North Sea during the years 1977 to 1981 (complemented with some results from 1982 to 1984)

Summary The measured concentrations of¹³⁷Cs in the water of the North Sea gained during the years 1977 to 1982 largely confirm the results found in the preceding years (Fig. 1). After a distinct maximum in 1978 — brought about by a particularly strong influx during 1977 — the total quantity of¹³⁷Cs present in the North Sea has reced, to around half of these peak values by the year 1982 (Table 1).On the way from the Sellafield Works near the Irish Sea as far as into the North Sea, a strong shift of the¹³⁷Cs:⁹⁰Sr ratio in favour of the⁹⁰Sr can be observed.By following the temporal course of that ratio at different measurement points, a transport time can be deduced of around 3 years between the Sellafield Works and the Pentland Firth; a further year would be needed to reach into the southeastern North Sea.The ratio Cs:Sr furthermore permits, in the southeastern North Sea, a good distinction between the watermasses comming from the north into the North Sea with respect to those that come through the Channel from the South. These masses practically flow side by side until about the entrance to the Skagerrak.The vertical distribution of the¹³⁷Cs shows, as is to be expected, seasonally conditioned differences. However, effects also occur, which — on the basis of the data available to date — do not yet permit a clear explanation.The⁹⁰Sr, as well as the^239+240Pu, present in the North Sea show an analogous distribution scheme compared with that of the¹³⁷Cs. Their concentrations lie far below that of the¹³⁷Cs (⁹⁰Sr 17.5%;^239+240Pu 0.03%).Tritium, on the other hand — with essentially higher concentrations — shows a completely different distribution, because it is principly introduced via the freshwater flowing in from the land.

---

Verteilung und Gehalt verschiedener künstlicher Radionuklide im Wasser der Nordsee in den Jahren 1977 bis 1981 (ergänzt durch einige Ergebnisse von 1982 bis 1984)

Zusammenfassung Die in den Jahren 1977 bis 1982 gewonnenen Meßdaten der Aktivitätskonzentrationen von¹³⁷Cs im Wasser der Nordsee bestätigen weitgehend die in den vorhergehenden Jahren gefundenen Ergebnisse (Fig. 1) Nach einem deutlichen Maximum im Jahre 1978 — hervorgerufen durch eine besonders starke Zufuhr im Jahre 1977 —ist die in der Nordsee insgesamt vorhandene Menge an¹³⁷Cs bis zum Jahre 1982 wieder auf rund die Hälfte zurückgegangen (Tab. 1).Auf dem Weg von den Sellafield Works an der Irischen See bis in die Nordsee ist eine starke Verschiebung des¹³⁷Cs:⁹⁰Sr Verhältnisses zugunsten des⁹⁰Sr zu beobachten.Aus dem zeitlichen Verlauf dieses Verhältnisses an verschiedenen Meßpunkten ergeben sich Transportzeiten zwischen den Sellafield Works und dem Pentland Firth von rund 3 Jahren; bis in die südöstliche Nordsee wird ein weiteres Jahr benötigt.Das Verhältnis Cs:Sr erlaubt außerdem in der südöstlichen Nordsee eine gute Unterscheidung der aus der Nordsee bzw. durch den Kanal von Süden kommenden Wassermassen, die praktisch nebeneinander her bis etwa zum Beginn des Skagerraks fließen.Die Vertikalverteilung des¹³⁷Cs zeigt, wie zu erwarten ist, jahreszeitlich bedingte Unterschiede. Es treten aber auch Effekte auf, die sich anhand der bisher vorliegenden Daten noch nicht eindeutig erklären lassen.Das in der Nordsee vorhandene⁹⁰Sr sowie das^239+240Pu zeigen ein analoges Verteilungsschema verglichen mit dem des¹³⁷Cs. Ihre Konzentrationen liegen weit unter der des¹³⁷Cs (⁹⁰Sr 17,5%,^239+240Pu 0,03%).Das Tritium zeigt bei wesentlich höheren Konzentrationen dagegen eine völlig andere Verteilung, da seine Hauptzufuhr im wesentlichen über das von Land her zufließende Süßwasser erfolgt.

---

Distribution et teneur de differents radionucleides artificiels, dans les eaux de la Mer du Nord entre les années 1977 et 1981 (completes par quelques résultats de 1982 à 1984)

Résumé Les mesures de concentration du Césium 137 dans les eaux de la Mer du Nord, acquises entre les années 1977 et 1982, confirment largement les résultats obtenus au cours des années précédentes. Après un net maximum en 1978 — occassionné par un apport particulièrement fort en 1977 — la quantité totale de Césium 137 présent en Mer du Nord a régressé,jusqu'en 1982, aux alentours de la moitié de ces valeurs maximales.Il a pu être observé une modification importante du rapport Césium 137/Strontium 90, en faveur du Strontium 90, sur le trajet de Sellafield Works prés de la Mer d'Irlande jusqu'à la Mer du Nord.En suivant l'évolution temporelle de la valuer de ce rapport en différents points de mesure, on peut en déduire une durée de transport d'environ 3 ans entre Sellafield Works et Pentland Firth; une année supplémentaire est ensuite nécessaire pour pénétrer en Mer du Nord Sud-orientale.En Mer du Nord Sud-orientale, le rapport Césium/Strontium permet en outre d'effectuer une nette distinction entre les masses d'eau pénétrant respectivement par le Nord dans la Mer du Nord et celles pénétrant par le Sud et venant de la Manche. Ces masses d'eau s'écoulent pratiquement côte à côte jusqu'à l'entrée du Skagerrak.Comme l'on pouvait s'y attendre, la distribution verticale du Césium est différente suivant les saisons. Cependant il apparaît également des effects qui, sur la base des données disponibles à ce jour, ne s'expliquent pas encore clairement.Le Strontium 90 aussi bien que le Plutonium 239+240 présent dans la Mer du Nord, montrent une distribution comparable, analogue à celle du Césium 137. Leurs concentrations sont bien inférieures à celle du Césium 137 (Strontium 90 17,5%; Plutonium 239+240 0,03%).Le tritium d'autre part, — avec des concentrations significativement plus fortes —montre une distribution complètement différente, due principalement au fait qu'il est introduit par l'intermédiaire de l'écoulement d'eau douce provenant de la terre.

     

Tidal currents,energy flux and bottom boundary layer thickness in the Clyde Sea and North Channel of the Irish Sea

A high-resolution three-dimensional model of the Clyde Sea and the adjacent North Channel of the Irish Sea is used to compute the major diurnal and semidiurnal tides in the region, the associated energy fluxes and thickness of the bottom boundary layer. Initially, the accuracy of the model is assessed by performing a detailed comparison of computed tidal elevations and currents in the region, against an extensive database that exists for the M₂, S₂, N₂, K₁ and O₁ tides. Subsequently, the model is used to compute the tidal energy flux vectors in the region. These show that the major energy flux is confined to the North Channel region, with little energy flux into the Clyde Sea. Comparison with the observed energy flux in the North Channel shows that its across-channel distribution and its magnitude are particularly sensitive to the phase difference between elevation and current. Consequently, small changes in the computed values of these parameters due to slight changes of the order of the uncertainty in the open-boundary values to the model, can significantly influence the computed energy flux. The thickness of the bottom boundary layer in the region is computed using a number of formulations. Depending upon the definition adopted, the empirical coefficient C used to determine its thickness varies over the range 0.1 to 0.3, in good agreement with values found in the literature. In the North Channel, the boundary layer thickness occupies the whole water depth, and hence tidal turbulence produced at the sea bed keeps the region well mixed. In the Clyde Sea, the boundary layer thickness is a small fraction of the depth, and hence the region stratifies.Responsible Editor: Phil Dyke     

Dissolved copper,zinc and cadmium in the Southern Bight of the North Sea

Concentrations of dissolved copper, zinc and cadmium have been measured in the Dutch and Belgian coastal and offshore regions of the Southern Bight (North Sea), with the aim to compare levels in the central, most saline part of the Bight with those in the coastal region that is under the influence of the rivers Rhine and Scheldt, as well as with those in open ocean surface waters.     

Cs baseline levels in the Mediterranean and Black Sea: A cross-basin survey of the CIESM Mediterranean Mussel Watch programme

The common mussel Mytilus galloprovincialis was selected as unique biomonitor species to implement a regional monitoring programme, the CIESM Mediterranean Mussel Watch (MMW), in the Mediterranean and Black Seas. As of today, and upon standardization of the methodological approach, the MMW Network has been able to quantify ¹³⁷Cs levels in mussels from 60 coastal stations and to produce the first distribution map of this artificial radionuclide at the scale of the entire Mediterranean and Black Seas. While measured ¹³⁷Cs levels were found to be very low (usually <1 Bq kg⁻¹ wet wt) ¹³⁷Cs activity concentrations in the Black Sea and North Aegean Sea were up to two orders of magnitude higher than those in the western Mediterranean Basin. Such effects, far from representing a threat to human populations or the environment, reflect a persistent signature of the Chernobyl fallout in this area.     

Quantitative assessment of dissolved radiotracers in the English Channel: Sources, average impact of la Hague reprocessing plant and conservative behaviour (1983, 1986, 1988, 1994)

Knowledge of long-term movements of water-masses in the English Channel has been substantially improved using hydrodynamic modelling coupled with radio-tracers studies; nevertheless, the precision of results so obtained is still largely dependent on measurement precision. New tools are now available to make more accurate determinations of radio-tracer distribution: (1) Repositioning of station locations at the same tide reference-time, giving a homogeneous spatial data set, coupled with the possibility of interpolating and quantifying the amounts of dissolved radioactivity flowing through the English Channel; (2) the first measurements of tritium (³H) in seawater on a large scale in the English Channel demonstrate that this fully conservative radionuclide is a clearly identifiable marker of industrial releases; (3) recent campaigns carried out during the FLUXMANCHE II CCE (1994) programme show the general distribution of dissolved radionuclides ¹³⁷Cs, ¹³⁴Cs, ⁶⁰Co, ¹²⁵Sb, ¹⁰⁶Ru and ³H in the English Channel and the Irish Sea; and (4) the re-utilisation of data from previous campaigns (1983, 1986, 1988) provides indications, at any given location in the English Channel, about the average dilution and distribution of releases derived from the La Hague reprocessing plant. Excesses and losses of radionuclides are now quantified with respect to known source terms; estimates of losses are provided for non-conservative radionuclides, while an excess of ¹³⁷Cs was observed in the English Channel during the period 1983–1994. This excess, which has the same order of magnitude as the quantities released from La Hague plant in the English Channel, could be explained by about 1% of the Sellafield reprocessing plant releases entering the Channel. These results confirm and give a more detailed picture of the previously known distribution of water masses in the English Channel. They lead to clear information about transit times and dilution at this scale, and provide directly comparable data for the validation of hydrodynamic models.     

Trace metals and radium in the Gulf of Mexico: An evaluation of river and continental shelf sources

Several studies have provided evidence for the enrichment of trace elements in coastal waters, particularly for copper. These enrichments have been attributed to diffusion from continental shelf sediments and to an influx of river water. We attempted to resolve between these sources by undertaking an extensive suite of measurements of trace metals (Cu, Ni, Cd), ²²⁶Ra and ²²⁸Ra in the surface waters of the Gulf of Mexico, along with trace metal profiles at 6 stations (April 1981 and December 1982). These data establish that enrichments of copper, nickel and cadmium occur in the shallow waters of the Gulf of Mexico. On the Mississippi continental shelf, high trace element concentrations (Cu, Ni: ～ 9 nmol/kg; Cd: ～ 200 pmol/kg) in lower-salinity waters (26‰) are similar to those observed in the Mississippi plume at the same salinity. This evidence suggests a river water source. On the other hand, trace element enrichments are also observed in the northern Gulf (Cu: +0.4 nmol/kg; Ni: +0.5 nmol/kg; Cd: +20 pmol/kg) which coincide with an increase in ²²⁸Ra but are not accompanied by decreased salinity. The excess of evaporation over precipitation in this region makes it possible that this water could be evaporated estuarine water; therefore, hydrographic observations cannot distinguish readily between river and shelf sources. A regional flux balance shows that most of the excess copper in the surface waters of the Florida Current can be supplied by the river-borne dissolved copper flux. Within the uncertainties of such calculations, the continental shelf copper flux must be less than or equal to the river flux.     

137Cs baseline levels in the Mediterranean and Black Sea: A cross-basin survey of the CIESM Mediterranean Mussel Watch programme

The common mussel Mytilus galloprovincialis was selected as unique biomonitor species to implement a regional monitoring programme, the CIESM Mediterranean Mussel Watch (MMW), in the Mediterranean and Black Seas. As of today, and upon standardization of the methodological approach, the MMW Network has been able to quantify ¹³⁷Cs levels in mussels from 60 coastal stations and to produce the first distribution map of this artificial radionuclide at the scale of the entire Mediterranean and Black Seas. While measured ¹³⁷Cs levels were found to be very low (usually <1 Bq kg⁻¹ wet wt) ¹³⁷Cs activity concentrations in the Black Sea and North Aegean Sea were up to two orders of magnitude higher than those in the western Mediterranean Basin. Such effects, far from representing a threat to human populations or the environment, reflect a persistent signature of the Chernobyl fallout in this area.     

The distribution of 137Cs in surface intertidal sediments from the Solway Firth

The distribution of ¹³⁷Cs from the Sellafield (Windscale) nuclear fuel reprocessing plant has been examined in detail in the surface intertidal sediments of the inner Solway Firth by means of a hovercraft-borne radiometric survey. With the exception of a belt of relatively active sands to the south of Silloth, caesium distribution is generally consistent with that of fine-grained sediment such that the highest concentrations occur in mud flat and salt marsh sediments which are most extensive in sheltered coastal embayments. ¹³⁷Cs activities in July 1980 were typically 2–30 pCi g^?1 but locally exceeded 50 pCi g^?1. These levels are considerably lower than those recorded in locations, such as the outer Solway and Ravenglass estuary, which are closer to the Sellafield outfall.     

Trace metal contamination of Beaufort's Dyke, North Channel, Irish Sea: a legacy of ordnance disposal

Beaufort’s Dyke is a disused ordnance disposal ground within the North Channel of the Irish Sea. Over 1 million tonnes of ordnance were disposed of in the dyke over a 40 year period representing a substantial volume of trace metal pollutants introduced to the seabed. Utilising particle transport modelling software we simulated the potential transport of metal particles from Beaufort’s Dyke over a 3 month period. This demonstrated that Beaufort’s Dyke has the potential to act as a source for trace metal contamination to areas beyond the submarine valley. Trace metal analysis of sediments from the Dyke and surrounding National Marine Monitoring Programme areas demonstrate that the Dyke is not the most contaminated site in the region. Particle transport modelling enables the transport pathways of trace metal contaminants to be predicted. Implementation of the technique in other munitions disposal grounds will provide valuable information for the selection of monitoring stations.     

Assessment of the historical trace metal contamination of sediments in the Elizabeth River, Virginia

Two sediment cores (Southern Branch, PC-1, and Western Branch, WB-2) were taken from the highly industrialized Elizabeth River, Virginia. The concentrations of trace metals cadmium, cobalt, chromium, copper, nickel, lead and zinc, major elements iron, manganese and aluminum, organic carbon content and the specific surface area of the sediments were determined in each of the cores. Down-core variations in metals varied significantly in each core with maximum contamination events occurring at different times in different portions of the river. In PC-1, maximum metal concentrations were seen after the appearance of (137)Cs. In contrast, the highest levels in WB-2 occurred well before the appearance of (137)Cs. Although stricter environmental regulations have caused a decrease in metal concentrations since the 1980s, the concentrations in the surface sediments of many trace metals were elevated to levels 2-5 times higher than the levels at the bottom of the cores in both the Southern and Western Branches of the river.     

Measurement of marine radionuclide distribution using a towed sea-bed spectrometer

The application of in situ gamma-ray spectrometry to the measurement of radionuclide concentration in sea water and sea-bed sediment is discussed with special reference to a towed sea-bed gamma-ray spectrometer survey of radio-effluent distribution in the Irish Sea. The sensitivity and accuracy of the method are established by comparing the spectrometer measurements with laboratory analyses of sediment samples. Contour maps produced from the spectrometer profiles are matched with the distribution of bottom sediment types and conclusions are drawn concerning the modes of transport and deposition of ¹³⁷Cs in the Irish Sea.     

(137)Cs baseline levels in the Mediterranean and Black Sea: a cross-basin survey of the CIESM Mediterranean Mussel Watch programme

The common mussel Mytilus galloprovincialis was selected as unique biomonitor species to implement a regional monitoring programme, the CIESM Mediterranean Mussel Watch (MMW), in the Mediterranean and Black Seas. As of today, and upon standardization of the methodological approach, the MMW Network has been able to quantify (137)Cs levels in mussels from 60 coastal stations and to produce the first distribution map of this artificial radionuclide at the scale of the entire Mediterranean and Black Seas. While measured (137)Cs levels were found to be very low (usually < 1 Bq kg(-1) wet wt) (137)Cs activity concentrations in the Black Sea and North Aegean Sea were up to two orders of magnitude higher than those in the western Mediterranean Basin. Such effects, far from representing a threat to human populations or the environment, reflect a persistent signature of the Chernobyl fallout in this area.     

Dissolved and particulate trace metals in a Scottish sea loch: an example of a pristine environment?

In the near pristine environment of a silled fjord on the west coast of Scotland samples were taken for the determination of dissolved and particulate trace metals (Fe, Mn, Cu, Ni, Cd, Zn and Pb), together with nutrient and hydrographic data, during 19 surveys carried out over a year. An indication of the pristine nature of the environment are the low concentrations of dissolved silicon, phosphate and nitrate which are considerably lower than those of coastal waters which are subject to larger anthropogenic burdens. Distributions of dissolved Cu, Ni and Cd were found to broadly reflect conservative mixing of freshwater and seawater with both end members having similar concentrations. The concentration of dissolved Cu and Ni in seawater entering upper Loch Linnhe (Cu 0.28 μg l⁻¹; Ni 0.26 μg l⁻¹) was consistent with the 1:1 conservative mix of Irish Sea water and North Atlantic surface water predicted from radio-caesium tracer experiments (Mackay & Baxter, 1985). Atmospheric input of trace metals to upper Loch Linnhe appeared to be a relatively minor term in the mass balance relative to fluvial inputs. Values of distribution coefficients Kd were similar to those previously reported for the coastal environment. Iron showed the strongest affinity for the suspended sediments; with particulate percentages of the total load usually greater than 80%. Lead and Mn showed a similar strong affinity to the particle phase. For Cu, Ni and Zn the mass of the element in the dissolved phase was generally greater than that in the particulate fraction. Cadmium, was least associated with the particles, with typically greater than 90% existing in the dissolved phase.     

Caesium-137: Its accumulation in a littoral community

The low-level radioactive liquid wastes which arise at the U.K. nuclear fuel reprocessing plant at Windscale on the Cumbria coast are discharged into the Irish Sea. These wastes are initially dispersed but they can also become reconcentrated in marine organisms. The present work discusses the concentrations of ¹³⁷Cs relative to those of potassium in the various stages of marine food chains and shows that discrimination occurs in favour of ¹³⁷Cs over potassium during the transfer between the different trophic levels.     

Cadmium,zinc, copper,and barium in foraminifera tests

The concentrations of cadmium, zinc, copper and barium have been determined on 2-mg samples of single-species foraminifera populations. Cleaning techniques were tested using North Atlantic core tops, and followed by a detailed downcore study for the last 30,000 years in South Atlantic core V22-174. Raw foram tests cleaned by crushing followed by ultrasonic removal of fine-grained material, and dissolved in a pH 5.5 acetate buffer, contain appreciable amounts of trace elements associated with ferromanganese and alumino-silicate contaminants. A reductive/complexing cleaning treatment reduces ferromanganese contamination by 1–2 orders of magnitude. Acetate buffers at pH 5.5 complex iron and raise the solubility of ferromanganese oxides; these buffers are unsuitable for separating carbonate lattice-bound trace elements from the fraction associated with ferromanganese phases. Improved mechanical and ultrasonic reductive cleaning combined with a mild dissolution in distilled water under 1 atm.P_CO2 reduces contaminant levels another order of magnitude. The Cd and Zn concentrations (order 10^?8 mole Cd/mole Ca and 10^?5 mole Zn/mole Ca) of species with low surface area show an increase with decreasing isotopic temperatures. This increase is consistent with the increasing concentrations of these metals from low values in surface waters to higher values at depth. The variance of Cd and Zn over the last 30,000 years in the central South Atlantic is consistent with the probable variability of the dissolved trace elements at the calcification levels of the species analyzed. Cu and Ba are irreproducible and probably sensitive to residual contaminant phases. The trace element content of the tests differs from levels observed in a recent coprecipitation study. Foraminifera may be a significant vector in zinc cycling in the ocean.     

An analogue model study of electromagnetic induction in the British Isles region

The behavior of electric- and magnetic-field variations over the British Isles region is studied using a scaled laboratory analogue model. The model source frequencies used simulate periods of 20 min to 2 h in the geophysical scale. The results indicate that conductive channelling of induced electric current by the English Channel is important for both E- and H-polarization, while channelling through the North Channel, the Irish Sea, and the North Sea is particularly important for the E-polarization. The funnel shape of the North Sea, leading to the relatively narrow English Channel, results in diffusion of current into the continent and the east coast of the British Isles, contributing to highly frequency-dependent horizontal electric- and vertical magnetic-field coastal anomalies. The model results also give ample evidence of current deflection at the complex coastlines.The model results for simulated $\text{1}\text{2}$ h period variations indicate vertical magnetic-field values changing by as much as a factor of five or six between certain coastal locations, and at least by a factor of two or three between interior locations. The horizontal electric- and magnetic-field components also show almost equally large changes, with particularly large enhancements near narrow ocean channels and irregular coastlines, responding to channelled and deflected current. With the relatively close proximity of the coasts for essentially all locations on the British Isles, the coast effects associated with the very complex coastlines can be expected to play a major role in the behavior of the electromagnetic fields over the British Isles.     

An intercomparison of seawater filtration procedures

Filtration systems, used for the preparation of coastal seawater samples for trace analysis, have been intercompared to determine the extent of contamination arising during the filtration process. The results show that all the systems intercompared are able to provide uncontaminated filtrates for copper, nickel, cobalt and manganese and, with two exceptions, for cadmium and iron, at levels that would be encountered in uncontaminated coastal waters.