Oil and Chemical Pollution最新文献

The effect of Qatar Light crude oil on the saltmarsh crab Sesarma catenata was investigated. These crabs are well adapted to the estuarine environment and mainly occur in the zone dominated by the saltmarsh grass Spartina maritima. They have an excellent aerial respiration and water-saving system and their burrows do not penetrate to water level. Static bioassays conducted showed that adult crabs are fairly resistant to the water-soluble fraction (WSF) of the crude oil, but that larval survival is affected at a much lower WSF concentration. Many of the crabs were, however, affected during the bioassays and may be considered as ‘ecologically’ dead.

In the event of spilled oil entering the estuary it is predicted that oil would form a layer over the water contained in the burrows. Although oil initially evaporates quickly, the layer of oil would drastically retard the diffusion of oxygen into the water, while some of the oil would dissolve into the water. It is estimated that the concentration reached at the end of a tidal cycle would not produce mortality, but would affect the crabs' respiration. Because of the small burrow volume, the crabs would be expected to utilize all the oxygen in the burrows before the next high tide. However, before that occurred, and at a critical oxygen saturation, the crabs would be expected to leave the water and climb through the layer of oil. Most crabs that return to clean water immediately, would probably not be further affected, except that the oil in their branchial chambers would reduce the area available for oxygen exchange. In some crabs, carapace contamination induces moulting, which in turn would make them more sensitive to oil pollution. The crabs would avoid polluted sediment, but might be attracted to very low and very high concentrations. Crabs remaining in the oil would clearly soon die of the combined effect of toxicity and oxygen depletion. Oil occurring on the saltmarsh surface would be degraded relatively fast, but once it seeps into the anaerobic mud, degradation virtually ceases. Experimentally, the hatching success ofgravid females, normal development and size of larvae spawned is not affected by Qatar Light crude oil, but their photopositive response is affected. The dangers of transferring oil from damaged tankers in Algoa Bay is discussed and recommendations made.

A sampling survey was carried out to measure the concentrations of certain chemicals which are discharged into the North Sea from chemical tankers following tank cleaning operations. The survey was carried out some 18 months after the implementation ofAnnex II of MARPOL and the results are compared with those obtained during a survey carried out before Annex II implementation.

The measured concentrations were found to be extremely low and in many cases were below the limits of detection of the analytical technique. No evidence has been found to suggest that the North Sea needs to be declared a ‘Special Area’ for the purposes of Annex II. If chemical tankers comply with the provisions of Annex II, harmful concentrations of chemicals should not arise in the North Sea as a result of tank washing discharges.

An experimental procedure is described to estimate the extent of evaporative weathering experienced by crude oils spilled in the marine environment. The essence of the procedure is the division of the crude oil into a series of pseudo-fractions by boiling point, and the subsequent modelling of the evaporative behaviour of each with the appropriate n-paraffin. The n-paraffin distributions of a number of naturally weathered crude oils were determined by capillary gas-liquid chromatography using fused silica columns. The actual extents determined by this procedure were compared with those generated by a computer simulation of the weathering, where the evaporative losses were modelled using film thickness, film temperature and weather data. Excellent results were obtained for oil film thicknesses between 10 μm and 1 mm, weathered for periods of up to 4 weeks.

In continuation of efforts to estimate oil inputs from coastal refineries to the marine environment in different regions, the present work concerns the Omanian refinery (Omanian Refinery Company) and its adjacent waters in the Gulf of Oman, Arabian Gulf.

It is estimated that the refinery adds 160·4 tons (}-163 t) of Omanian crude oil wastes and refined products annually to Mina Al Fahal waters where it is situated. This is additional to the 140 tons (}-142 t) discharged annually in the same area from the tank drains of a neighbouring tank farm. Analysis of dissolved/dispersed petroleum residues in the receiving waters of the main oily water outfall indicates a high factor of dilution: more than 200 times less than the concentration of oil in the discharge itself (67 μg litre⁻¹ in the receiving waters against 14·7 mg litre⁻¹ in the outfall waters).

ELSA is a new diagnostic system to support decision-making in respect of accidental spills in the marine environment. This paper describes the newly developed methodology, intended to analyse and to characterize the gravity of an accident, which matches in an adequate way the needsfor simplicity, speed and completeness in the initial stages of an accident. By this approach the gravity of an accident is presented in an overall scale of value which is easy to interpret. The overall gravity is the sum of the subscale value(s) for hazards such as toxicity in air, bioaccumulation, persistence, flammability, explosiveness, toxicity in water, corrosiveness, carcinogenicity or radioactivity. The approach is based on criteria such as practicality, acceptability, accuracy and completeness, and is intended for operational use in the initial stage of an accident. The methodology is therefore implemented on a computer model to describe and quantify, as fast as possible, the gravity of an accident which involves substances that have the potential to produce adverse effects on the marine environment, users of the sea or response personnel. Such a diagnostic system is necessary for appropriate decisions on the cautionary response (the protection of human life and health, and the protection of the natural environment) and the corrective response (recovery and containment or control of the pollution). This model may assist responsible authorities in judging the gravity of an accident at sea and will provide a means whereby the general public and the press will more easily reach a reasonable assessment of the true nature of accidents to which the authorities are responding.

A modelling study of transport of vinyl chloride monomer in the sea following a leakage from the sunken ship B. Montanari is presented to help evaluate the impact of several strategies to save the environment from a leakage of the substance and to assess the area affected by concentrations that are considered harmful. As a first step, parameters of a stationary and a nonstationary leakage were estimated. The parameters included the discharge rate, the mean sea current vector, an extinction coefficient and the horizontal dispersion coefficient. The estimation was necessary since the complete behaviour of the substance in real conditions was not known. Upon completion of the estimation procedure, simulation of several cases was attempted. Firstly, results are presented concerning a transient concentration field in an unbounded environment following possible releases. Secondly, the results of the stationary leakage are compared for different current fields in the Bay of Remetic where the ship was taken for unloading.