Oil and Chemical Pollution最新文献

Dispersants have been used with mixed success since the Torrey Canyon incident in 1967. Although in recent years the use of mechanical recovery methods has been increasing, dispersants still continue to be the main method ofpollution control in many countries. This paper presents a discussion on the limitations of dispersants and provides criteria for determining whether the dispersant approach will provide an acceptable means of treating a particular spill. It concludes that, non-spreading high viscosity oils, water-in-oil emulsions and oil slicks in the final phases of spreading, i.e. very thin slicks, are effectively non treatable with dispersants. It also suggests that as an alternative to dispersant treatment for dispersible oils, consideration should be given to increasing natural dispersion rates by agitation from the passage of boats through the slicks.

Planktonic organisms from natural estuarine waters were allowed to settle in tanks floored with autoclaved natural sediment mixed with oil-based drill-muds to give an initial oil concentration of 1000 × the background total hydrocarbon content. Over the 200 days of the experiment, there was a marked difference between the biota developing in tanks containing oil-based drill-muds, and in the control tank, which received drill-mud solids only, without any oil. Differences in effect werefound between two drill-muds, based on alternative oils of moderate and low aromatic hydrocarbon content, but there was a greater difference between these two muds and a diesel-based mud. Biota developed, even in the diesel-mud tank, when surficial sediment oil concentrations fell, despite high oil concentrations remaining in the subsurface sediments.

The environmentally relevant properties of 99 hydrocarbons, namely vapour pressure, water solubility, octanol—water partition coefficient, and Henry's Law Constant, are reviewed and tabulated. Simple correlations for these properties of aromatic and alkane hydrocarbons are derived as a function of carbon number and molar volume. Although the correlated values may contain errors exceeding an order of magnitude in 5% of the cases, the values will often be sufficiently accurate for environmental assessment purposes and can be used to check the reasonableness of reported experimental values.

A fluorescence spectroscopic method for identifying the sources of spilled oils is described. Bird feathers collected after various oil spill incidents were analysed. Comparison of the total fluorescence spectra showed that fluorescence spectroscopy could rapidly provide a fingerprint which would allow identification of the spilled oil by comparing its spectrum with spectra of possible sources. Weathering does not affect the spectra of crude and heavy fuel oils.

Studies on the response of fauna to natural disturbances indicate that disturbance events may be important in structuring marine benthic communities. Benthic populations in the Santa Barbara Channel off Isla Vista, California are regularly subjected to natural disturbances by chronic petroleum seepage in the area. It has been suggested that these populations show enhanced dispersal abilities when compared to populations that are not disturbance-adapted. Our study compared the rate of meiofaunal colonization into azoic sediment trays buried at an oil seep site with a nearby comparison site free of fresh oil. At the comparison site, for all taxa examined, meiofaunal abundances in the colonization trays did not reach ambient (surrounding sediments) levels at any time during the 23-h experiment. At the seep site, meiofaunal abundances in the trays reached ambient levels in 6 to 23 h, depending on taxa. Thus, the rate ofmeiofaunal colonization was faster at the seep site than at the comparison site. Enhanced susceptibility to passive transport or active water column entry by some species was most likely responsible for the enhanced colonization rate at the seep site.

A single channel profiling oil in-situ fluorometer has been constructed and tested in the marine environment as well as during controlled conditions in the laboratory. Its performance range for oil was shown to lie between 5 ppb up to 100 ppm (5 × 10⁻⁹ and 100 × 10⁻⁶, respectively) assuming no so-named fluorescent contaminants such as dissolved organic, inorganic and planktonic material.

The fluorescent contaminants are generally of importance in coastal waters like the Baltic, the North Sea and the Norwegian Coastal Current. Steps taken to correct the total fluorescent signal for these contaminants in order to obtain thefluorescent signal due to oil are described and discussed. It is suggested that single channel oil fluorometry in the sea preferably should be combined with auxilliary optical measurements in order to arrive at reliable quantifications of spatial distribution of oil spills in the sea especially in the vicinity of land, oceanic fronts and pycnoclines, respectively.

A laboratory simulation of an oil spill was used to monitor the effect of microbial alteration on crude oil molecular, bulk and carbon isotopic compositions. The rate of microbial alteration of alkanes decreased with increasing carbon number. Straight-chain alkanes were more rapidly removed than branched (isoprenoid) hydrocarbons though ultimately even the isoprenoids were degraded. Aromatic compounds were also altered. Isomer specific degradation was observed within a given aromatic alkylation (i.e. methylphenanthrenes). The most stable properties, under the given conditions, were carbon isotopic composition, Ni/V ratios, total scanning fluorescence spectra, and various molecular distributions. Aromatics with two or more rings and more than a two carbon substitution, triterpanes and steranes were relatively stable. Mono- and tri-aromatized steranes were substantially altered. These stable chemical properties or fingerprints are suggested as unique and sensitive indicators that can be used to determine the source of microbially altered hydrocarbons in the environment.

Four different oil-based drilling fluids were microencapsulated in a acacia/ gelatine structure. The microcapsules (size 1–10 μm) are dispersed in natural seawater in different concentrations, and fed to mussels in a running seawater system. One water-based drilling fluid was dispersed in seawater without microencapsulation. The growth in length of the exposed mussels was measured every 24 h for five days. Among the oil-based drilling fluids, the EC₅₀ (5d) varied from < 1 to 66 ppm, and for the water-based drilling fluid EC₅₀ ≫ 1000 ppm. There is no correlation between toxicity of the drilling fluids and their oil/water ratio, or between toxicity and the total content of aromatics in the base oils. The mussel test shows a markedly lower toxicity threshold than other tests with the same drilling fluids (Balanus-test, Microtox, Skeletonema-test). The results show that ingestion and digestion of the microencapsulated non-water soluble components of the drilling fluids may have a large impact on the overall toxicity, and that realistic estimates of specific toxicity have to include the effect of both particulate and dissolved fractions.