Oil and Petrochemical Pollution最新文献

Pollution by petroleum itself is very largely confined to the contamination of water—sea water or fresh water—usually caused by accidents, and is a local problem. On the other hand, air pollution by products of combustion occurs whereever petroleum products are used for the production of heat or power. Normally, the natural dispersion processes in the atmosphere are sufficient to prevent the concentrations of pollutants exceeding sale limits, but if emissions are too great for this to occur they are subject to legal regulations. Examples are emissions of sulphur dioxide from power station chimneys were ground level concentrations are controlled by the height at of the chimney, and emissions from motor engines in districts such as Los Angeles where they would cause photochemical smog. In recent years, in Great Britain, there has been growing public disquiet about another aspect of motor exhaust emissions, namely lead, which is added to petrol to improve performance. This issue has become highly emotive as it has been linked with the possibility that the intelligence of young children may be adversely affected by exposure to lead from motor exhaust. This paper has been written to provide background information to the facts and guess work in this field.

A chemical dispersant concentrate was aerially applied, at a rate of approximately 2 gal/acre (19 1 ha⁻²) to a crude oil slick emanating from the Ixtoc 1 well blowout.

Chemical analyses of dispersant collected on pans at the sea surface beneath the swath of aerially-applied dispersant, showed no appreciable change in chemical composition from that of dispersant samples taken from holding tanks in the spray plane.

Comparisons between oil concentrations in water at varying depths under the stick, determined before and approximately one hour after cispersant application, showed elevated concentrations of hydrocarbons in the water column.

Photographs and visual observations from the research vessel and the two aircraft involved in the test indicated that application of dispersant did not cause ‘herding’ (lateral displacement) of the crude oil slick.

Toxicity tests were conducted with Daphnia magna exposed to refinery effluents and reference toxicants in order to compare inter- and intralaboratory variation in acute toxicity test results, and to evaluate the utility of conducted 24 h screening tests on effluents. Significant differences in dose-response curves and EC50 for animals exposed to reference toxicants occurred within and among laboratories.

The 48-h EC50s and dose response slopes obtained within laboratories for any effluent sample were reproducible; however, variability among laboratories was considerable and dose-response slopes were not comparable. Analysis of screening test data using a fixed criterion, e.g., 80% survival after 24-h, indicated that survival proportions as low as 62.5% and as high as 92.5% were not significantly different from an 80% criterion.

The effects of crude oil pollution on the seedling and subsequent growth phases of Zea mays Var. F27, (Corn) Abeimoschus esculentus (Okro) and Capsicum frutescens (Pepper) were investigated. Zea mays seedlings and Capsicum plants were most susceptible to crude oil spillage at 31 m⁻². Mature Z. mays and Abelmoschus esculentus were fairly tolerant to crude oil doses of 31 m⁻² and 61 m⁻². In the spraying experiments crude oil was found to be a potent contact herbicide. Z. mays and Abelmochus esculentus were completely destroyed in one or two weeks by death and maceration of vegetation or by defoliation. Capsicum frutescens rapidly recovered from defoliation with a flush of new leaves and branches 3 weeks after oil treatment.

Among other factors, the phytotoxic, hydrophobic and other stress imposing properties of crude oil were suggested as causes of death to plants.

During the period 1975 through 1978 sampling for tar balls was undertaken at 1473 oceanographic stations situated around southern Africa. While negligible concentrations of tar balls were measured at the majority of the stations, 21% of samples were in excess of 0.1 mg m⁻² with the highest recorded value being 232 mg m⁻². The extensive tar ball sampling programme undertaken around the Cape of Good Hope during 1977 and 1978 coincided with a study of surface currents in the area using plastic drift cards. Analysis of the drift-card returns from batch releases at stations where the tar ball concentrations exceeded 0.1 mg m⁻² has provided a conceptual image of the probable movement of the tar balls in the system and an indication of the vulnerability of some areas of the cost to chronic pollution.

The main features and conclusions are as follows:

• (a)

  Tar balls are moved southwards and westwards off the east coast from a probable formations zone in the western part of the Mozambique Channel north of 27°S by the swiftly flowing Mozambique/Agulhas Current.

• (b)

  Although the majority of the tar balls are probably carried offshore into the West Wind Drift area via the retroflexion of the Agathas Current south of South Africa, some tar balls appear to be advected onto the Agulhas Bank by the shear-edge eddies associated with the Agulhas Current.

• (c)

  As a result of oceanographic and meteorological influences, the breaches of northern Natal and the areas east of Cape Agulhas are very vulnerable to chronic tar ball pollution.

• (d)

  In view of the divergent nature of the Benguela Current system off the west coast and lower levels of tar balls in the region, beaches on this coast are not very vulnerable to pollution during summer, although during winter, when the upwelling relaxes, there is an increased risk.

Field studies directed towards evaluating the toxicity of dispersant-treated and untreated fresh and weathered Maui ‘D-sand’ condensate to intertidal invertebrates were conducted at Anawhata, on the west coast of North Island of New Zealand. Observations were concentrated on the barnacles Chamaesipho columna and Epopella plicata and the bivales Xenostrobus pulex and Perna canaliculus. The field studies continued for 83 days after treatment. Two dispersants were tested, Shell SD LTD and BP1100 WD (Synperonic OSD 20).