Results of two bilateral comparisons of the determination of hydrocarbon concentrations in coastal seawater by fluorescence spectroscopy

During two recent research cruises, comparisons were made of measurements of hydrocarbon concentrations in seawater by fluorescence spectroscopy. Participants used their own samplers and methods to collect and analyse duplicate samples of subsurface water; 21 stations were sampled during the first cruise and 15 during the second. When samples containing hydrocarbons at concentrations of 1–2 μg l⁻¹ Ekofisk crude oil equivalents were extracted using solvents of similar polarity, i.e. pentane or hexane, results on average varied by 22% and 23% in the two exercises. Use of dichloromethane as an extraction solvent gave results around 2× higher; the reasons for this are discussed.     

Petroleum hydrocarbons in the arctic ocean surface water

The concentration of petroleum hydrocarbons in Arctic surface water under the ice north of Svalbard has been determined by fluorescence spectrofluorometry using three different excitation/emission wavelength combinations. With Kuwait crude oil as a reference, the concentration range is 0.1–0.6 μg l^?1 crude oil equivalents with respect to light molecular weight components and 0.05–0.2 μg l^?1 heavy molecular weight components.     

Dispersion of dissolved trace metals from the Irish Sea into Scottish coastal waters

An investigation has been undertaken into the dispersal of contaminants from the Irish Sea into coastal waters of Scotland via the North Channel. A total of 97 surface samples have been analysed for dissolved copper, cadmium and lead. Salinity and reactive phosphate have also been determined. Evidence is presented to suggest that copper, cadmium and reactive phosphate behave essentially conservatively on mixing into Scottish coastal waters. This behaviour is likened to the dispersal of¹³⁷Cs from the Sellafield nuclear fuel reprocessing plant. It is suggested that this simple mechanism is inadequate to account for the lead distribution. It is proposed that this element is partly taken up by suspended particulates and sediments in the well-mixed turbid waters of the North Channel.It has been demonstrated elsewhere that contaminants from the Irish Sea, such as¹³⁷Cs enter the Firth of Clyde from the North Channel. In the present study North Channel waters are demonstrated to be an important source of trace metals to the Firth of Clyde. At the time of this survey however high concentrations of trace metals were not entering the Firth of Clyde from the North Channel. This is principally attributed to a salinity front associated with the entrance of the Firth which hinders transport across the sill.     

Trace metal levels in coastal sea water investigation of Danish waters

The concentration levels of Cd (25 ng l^?1), Cu (0.45 μg l^?1), Ni (0.48 μg l^?1), Fe (0.2–7.0 μg l^?1), Pb (40 ng l^?1) and Zn (0.80 μg l^?1) have been determined in the Danish Sounds and in the Kattegat. Different sampling techniques have been used and analyses have been carried out separately by two different investigators, both using freon-extraction followed by determination by atomic absorption spectrometry (a.a.s.). Except for iron, found mainly in the particulate phase, the metals are found predominantly in a dissolved and labile (extractable) form. The results are compared with trace metal levels found in the two main water masses entering the Kattegat—the North Sea and the Baltic Sea.     

Present state of oil pollution in the northern Indian Ocean

A consolidated picture of oil pollution for the northern Indian Ocean is presented. Oil slicks were sighted on 5582 observations, about 83.5% of the total observations of 6689. The range of concentrations, of the floating tar balls, is 0–6.0 mg/m² in the Arabian Sea. Similarly, the oil tanker route in the Bay of Bengal has the range of 0–69.75 mg/m². North of this route, the Bay of Bengal is comparatively free from this floating tar. Mean concentrations of dissolved and dispersed hydrocarbons for 0–20 m are 32.5 and 24.1 μg kg^?1, respectively, in the Arabian Sea and the Bay of Bengal.     

Increased levels of petroleum hydrocarbons in the surface sediments of Swedish coastal waters

Petroleum hydrocarbons in the sediments of the Bothnian Bay, Baltic proper, Öresund, Kattegatt and Skagerrak were analysed in a survey of oil pollution along the Swedish coast in 1974 and 1975. Sixty-one of these sediment stations were revisited in 1982 and analysed with the methods used in the first survey. The mean content of petroleum hydrocarbons (paraffin-naphthene fraction) in the sediment surface showed a statistically significant increase from 199 to 252 μg g^?1 dry wt. The main increase had taken place in the coastal areas. Within 0–20 km distance of urbanized areas (>20 000 inhabitants) petroleum hydrocarbons had increased from 371 to 447 μg g^?1. Sediment levels increased from 76 to 117 μg g^?1, 20–50 km from urbanized areas. The increase in these areas was equivalent to 0.119 g m^?2 yr^?1.     

Untersuchungen zur Bestimmung und zum Vorkommen des Thiocyanats im Wasserkörper der westlichen Ostsee

For the gas-chromatographic determination of thiocyanate in waters two enrichment processes were used: 1) the evaporation of the water sample on the water bath and 2) the adsorptive enrichment on Wofatit EA 60. As the example of the investigation of water samples from the Baltic Sea has shown, the less selective process 1 gave higher results of measurements than the adsorptive method 2. As compared with the GDR's coastal region of the Baltic (0.4 … 5.2 μg/l), the SCN^? concentrations (1986) in the western offshore region (0.1 … 2.1 μg/l) are considerably lower. With increasing depth and growing salt content the SCN^? concentration in the Baltic decreases. Anthropogenic influences, such as the input of residual products of sewage works effluents, can be inferred from the relatively increased SCN^? concentrations in the coastal region.     

Lead and copper in the waters of Raritan and Lower New York Bays

A survey of waters adjacent to this heavily urbanized and industrialized region showed concentrations of copper, 65 μg l.^?1 to be the highest reported to date for estuarine waters, and lead up to 13.9 μg l.^?1 Correlations between distributions of dissolved and total metal concentration in the water column, hydrography, and metal in the sediment were related to benthic studies in this area. Laboratory studies are cited which show the potential for adverse effects on marine animals at these metal concentrations.     

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.     

Cultivable bacteria from bulk water,aggregates, and surface sediments of a tidal flat ecosystem

Most-probable-number (MPN) dilution series were used to enumerate and isolate bacteria from bulk water, suspended aggregates, the oxic layer, and the oxic–anoxic transition zone of the sediment of a tidal flat ecosystem in the southern North Sea. The heterotrophic aerobic bacteria were able to grow on agar-agar, alginate, cellulose, chitin, dried and ground Fucus vesiculosus, Marine Broth 2216, palmitate, and starch. MPN counts of bulk water and aggregate samples ranged between 0.18?×?10¹ and 1.1?×?10⁶ cells per milliliter and those of the sediment surface and the transition zone between 0.8?×?10¹ and 5.1?×?10⁷ cells per gram dry weight. Marine Broth and F. vesiculosus yielded the highest values of all substrates tested and corresponded to 2.3–32% of 4,6-diamidinophenyl indole cell counts. Strains of seven phylogenetic classes were obtained: Actinobacteria, Bacilli, α- and γ-Proteobacteria, Sphingobacteria, Flavobacteria, and Planctomycetacia. Only with agar-agar as substrate could organisms of all seven classes be isolated.     

Oil pollution on the Egyptian Red Sea coast

A simple weighing method using carbon tetrachloride as solvent was used to survey the dissolved hydrocarbon and tarball levels in the area of the Egyptian Red Sea coast. The area of investigation covers the coastal area from Ras-Gharib down to the port of Qosier during the period from September 1979 to February 1981. This survey confirms the presence of extensive oil pollution in the area, especially at Ras-Gharib and Ras-Shukhair. Minimum concentrations were obtained at Ghardaqa where no dissolved hydrocarbons were detected (i.e. less than 10 μg l^?1) in 1979–1980 but an increase to 20 μg l^?1 in 1981 was recorded. The high levels of pollution recorded in the southern part of the Gulf of Suez are related to the presence of the offshore oil fields, most of which are located at Ras-Gharib.     

A rapid field method for detecting oil in sediments

A rapid thin-layer chromatographic technique for estimating the relative concentration of crude oil in sediments has been developed. The limit of detection on the chromatogram is 2 μg of Empire Mix or Saudi Arabian crude oil. The technique has been tested on 335 sediment samples collected from 67 stations in the Gulf of Mexico and has been utilized in assessing the location of oil entering the sediments from the Argo Merchant spill incident.     

Photo-induced toxicity of north sea crude oils toward bacterial activity

Toxicity of photolysis products from Ekofisk and Statfjord crude oils toward natural assemblages of marine bacteria was investigated. Incorporation of ¹⁴C-glucose, ¹⁴C-amino acids or ³H-thymidine were used as indicators of microbial activity. While none of these measurements revealed any significant effects of non-illuminated oil, a toxic effect was found after a few hours illumination of an oil slick.     

North American microtektites from the Caribbean Sea and their fission track age

Over 6000 microscopic glass spherules between 125 μm and 1 mm in diameter were found in a sediment core (RC9-58) from the Caribbean Sea. These glassy objects are mostly confined to a zone ～ 40 cm thick at a depth of ～ 250 cm. We believe that the microscopic glass objects are microtektites belonging to the North American strewnfield, based on their geographical location, appearance, physical properties, stratigraphic age (middle Upper Eocene), fission track age (～34.6 my) and major element compositions. The occurrence of North American microtektites in the Caribbean Sea indicates that the North American strewnfield is two to three times larger than previously indicated. An estimate on the abundance of microtektites in core RC9-58 indicates that the North American strewnfield may contain greater than 10¹⁷ g of tektite material.     

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 petroleum hydrocarbons in some regions of the northern Indian ocean

Dissolved petroleum hydrocarbons were measured in some parts of the Northern Indian Ocean using UV absorbance technique with a clean up step. The concentration of oil ranged from 0.6 to 26.5 μg l^?1. Higher values were recorded along the oil tanker route compared with the coastal region From surface to about 10 m depth the oil appeared to be well mixed with water.     

The nature and transport of the fine‐grained component of Swift Creek Landslide,Northwest Washington

Extreme sedimentation in Swift Creek, located in the Cascades foothills in NW Washington (48°55′N, 122°16′W), results from erosion of the oversteepened, unvegetated toe of a large (55 hectares) active landslide. Deposition of landslide‐derived sediment has necessitated costly mitigation projects in the channel including annual dredging and temporary sediment traps in an attempt to reduce the risk of flooding and damage to man‐made structures downstream. This study attempts to understand the process of sediment production along with the corresponding erosion rates of the sediment source to help with the development of mitigation plans and construction of optimal sediment reservoirs. The bedload and suspended sediment in the creek are a direct result of the weathering process of the serpentinitic bedrock underlying the landslide. The serpentinite does not weather to smectite clay, as previously thought. Instead, it weathers to asbestiform chrysotile with minor amounts of chlorite, illite and hydrotalcite, all of which occur in clay seeps on the unvegetated surface of the landslide. The chrysotile fibers average 2 µm in length and make up at least 50%, by volume, of the suspended load transported in Swift Creek. This study does not address the environmental or health implications of the asbestiform chrysotile transport or deposition. During the sampled time between February 2005 and February 2006, 127 discrete suspended sediment samples were collected and discharge was measured 66 times. The suspended sediment concentrations ranged from 0·02 g L^?1 to 41·6 g L^?1 and the discharge ranged from 0·0 m³ s^?1 to 0·5 m³ s^?1. A nonlinear functional model estimated the total suspended sediment flux from detailed precipitation records and discrete suspended sediment concentration and discharge measurements to be 910 t km^?2 yr^?1. When the suspended sediment flux is coupled with estimates of downstream deposition of coarse sediment, the estimated erosion rate for the entire Swift Creek landslide is 158 mm yr^?1. The majority of the material entering Swift Creek is presumed to originate on the unvegetated toe of the landslide, for which the erosion rate is thus approximately 1 m yr^?1. Copyright © 2010 John Wiley & Sons, Ltd.     

Correlation of dispersant effectiveness and toxicity of oil dispersants towards the alga Chlamydomonas reinhardti

Using synchronous cultures of the unicellular green alga Chlamydomonas reinhardti, the toxicities of mixtures of Ekofisk crude oil and oil dispersants were measured. Sixteen so-called concentrates and 10 solvent-based dispersants were tested. The dispersing effectiveness of these compounds with respect to the Ekofisk crude oil was also measured. The concentrates were tested undiluted as well as diluted using algal growth medium (2‰ salinity) and artificial sea water (33‰ salinity) as dispersing liquid. The solvent-based compounds were tested in algal medium. For all compounds we found significant correlations between their toxicity and their effectiveness in dispersing the Ekofisk oil, such that the more effective the compound, the more toxic it was.     

Shell thickening in Crassostrea gigas: Organotin antifouling or sediment induced?

Crassostrea gigas spat were cultured for 8 weeks in the presence of a mixed algal diet in experimental tanks containing bis (tributyl tin) oxide (TBTO) alone, TBTO and a marine sediment, or a marine sediment alone. Growth measurements taken on a weekly basis showed enhanced weight gain in oysters exposed to nominal 50 and 100 mg l^?1 concentrations of marine sediment alone. Spat in low level TBTO treatments (0.15 μg l^?1) grew less well than the controls and showed pronounced thickening of the upper shell valve. High levels of TBTO (1.6 μg l^?1) severely inhibited oyster growth. Tissue concentrations of TBT compounds were measured at the end of the experiment. Bio-concentration factors of 3000- and 10000-fold were demonstrated for the high and low TBTO treatments respectively.     

Sediment PAH: Contrasting levels in the Caspian Sea and Anzali Wetland

A comparative study of 23 PAH congeners in sediment of the Caspian Sea coast and Anzali Wetland was conducted in 2010. Surface sediment was analyzed using chromatography and mass spectrometry. Total PAH concentrations ranged between 212 and 9009 ng g⁻¹ dw. Spatial distribution maps revealed that PAH levels were higher in the coastal areas of the Caspian Sea where oil related activities have been common since 1800’s. Diagnostic ratios analysis indicated that PAHs largely originated from petrogenic processes. PAH toxicity level was assessed using sediment quality guidelines and toxic equivalent concentrations to determine toxic effects on marine organism. Based on these investigations, in our study areas, the probability of toxicity for benthic organisms is “low to medium”. The toxic equivalent concentrations of carcinogenic PAHs varied between 11 and 231 ng TEQ/g; higher total toxic equivalent concentrations values were found in the coastal areas of the Caspian Sea.