Oil and Chemical Pollution最新文献

Various petroleum distillates differing mainly in their aromatic content were photo-oxidized in the solar UV range and analysed by FTIR and UV spectrophotometry. It appeared that mononuclear alkyl aromatics play a key role owing to the high reactivity of their a carbon in the radical propagation of oxidation chains. They are transformed into phenones whose high molar absorptivities in the UV range explain the observed spectral changes.

One year of weathering effects on oil on rock surfaces has been studied on four different shores in the archipelago of Stockholm, northern Baltic Proper (non-tidal). The test shores are exposed in different ways to waves and drift-ice and their slopes are either flat or steep. In order to study the natural weathering, spots of heavy fuel oil (No. 5) were applied at different levels above the mean water level. After 12 months of weathering, the moderately high and the highly exposed rocks were almost free from oil between the mean water level and 5 m above. In contrast, significant weathering only occurred up to 0·5 m above the mean water level on the less exposed and flat sloping rock. Furthermore, the less exposed rock with high inclination was free of oil only at the mean water level.

The results from this study show that natural weathering can remove oil from certain levels on rocky shores in less than a year even in non-tidal areas like the Baltic.

The report describes an exercise to compare two techniques for the continuous measurement of sub-surface concentrations of oil in sea water. One uses a flow-through fluorometer calibrated by collecting discrete water samples and determining their oil content, whilst the other uses a towed, submersible fluorometer calibrated by homogenising a known quantity of oil in sea water. The performance of the two instruments was compared during a field trial carried out by Warren Spring Laboratory and the MAFF Fisheries Laboratories. Both instruments were found to give very similar outputs beneath both non-dispersed and chemically dispersed oil slicks and this suggests that the sensitivities of the two instruments are similar.

The structure of benthic biocenosis of the estuarine mangroves of the Mahakam delta (East Kalimantan, Indonesia), is relatively uniform and dominated by polychaeta worms and crabs. The most important environmental variables determining dominant benthic species are salinity, emersion degree (intertidal zone), granulometry and redox potential. Generally speaking, a community's reaction to pollution variesfrom decrease in diversity and total numbers to complete azoic conditions. The demographic structure of Nereis sp. has been shown to evolve in this way along the oil pollution gradient in an experimental oil pollution location and in areas of chronic pollution. After 3 months the largest size categories are first eliminated, while the number of small individuals increases significantly. Then total numbers suddenly drop. The examination of redox profiles enables effects of chronic oil nuisances to be distinguished from effects due to experimental spills. In experimentally polluted zones profiles show low redox values just below the surface of sediment, while in chronically polluted zones the profile is uniformly low. After 1 year, re-colonization is achieved for the total number of individuals but destabilization within the population structure still persists. Puliella sp. is also very abundant. Its average biomass per station is very much weaker in a polluted than in a non-polluted area. Thus this organism also appears to be a suitable pollution indicator. Only very strong pollution can eliminate this species.

Models of the diffusion from a continuous source in the sea often make use of the diffusion velocity concept which relates diffusivity linearly to the diffusion time, estimates of the diffusion velocity being obtained by field trials. The weakness of the approach is that it is not clear how data collected during calm conditions can be used to predict the spreading during rough weather. To overcome this, a diffusion model has been developed that isolates the spreading due to wind and waves so that the effects of weather can be quantified. This technique should lead to improved predictions of plume spreading during a range of weather conditions.

Samples of subsurface water and surface sediments, collected from the north-eastern Irish Sea in 1982–3 before development of the Morecambe Bay gas field, have been analysed for hydrocarbons and metals. Total hydrocarbon concentrations were determined in both water and sediments by fluorescence spectroscopy; specific aliphatic and aromatic hydrocarbons were also determined in sediment samples from selected stations by computerised gas chromatography—mass spectrometry. At selected stations, concentrations of metals (Cr, Ni, Cu, Zn, Cd, Ba, Hg and Pb) were determined in whole surface sediments and of these metals, with the exception of barium, in the sediment fine fraction (< 90 μm). The results of these analyses show widespread contamination of the north-eastern Irish Sea by both metals and hydrocarbons, particularly in the south of the survey area, close to the Rivers Mersey, Dee and Ribble, and in Liverpool Bay, but extending through the area around the gas field. Estimates are made of the magnitude of the input of certain metals that may result from cuttings discharge during the development of the gas field, and these are compared with the inputs to the area from other sources including sea disposal and river inputs.

A sampling survey in the North Sea has measured the concentrations of certain chemicals which are discharged into the sea from chemical tankers as a result of tank cleaning operations. The results obtained show that the concentrations of these chemicals are very low and many times less than their 96-h LC₅₀ values. The measured concentrations are of a similar order of magnitude as those calculated from a procedure based on estimated inputs and the turn-over time of the North Sea. It is concluded that because the implementation of Annex II of MARPOL 73/78 should further reduce the amount of chemicals discharged into the sea it does not appear to be necessary for the North Sea to be declared a Special Area for the purposes of Annex II.

Standard tracer techniques, known from work with radioactive tracers and fluorescent dyes, have been applied for full scale studies of the distribution of oil in the water column. The study was part of oil spill experiments conducted off the coast of Norway in June 1985 under the research program ‘Dispersion of Oil on Sea’ Light scattering of oil droplets in water and UV-fluorescence of dissolved oil components were used for in-situ detection of oil in water. By UVfluorescence measurements, being the more sensitive of the two methods, it was demonstrated that dissolved components of oil were present 15 m below the slick less than one hour after the surface release of 10 tonnes of Statfford crude oil (premixed with 2% dispersant). By tracking a submerged UV-fluorimeter through the elongated oil patch it wasfound that the maximum concentration of dissolved components occurred below the central part of the slick. It was experienced that in-situ UV-fluorimeter recordings provide detailed information on the relative distribution of dissolved oil compounds in the water column below a slick.

By laboratory calibration of the UV-fluorimeter it is possible to establish a reliable estimate on the physical dilution of the released oil within a working range of 5 to about 10 000 μl m⁻³ oil in water. However, at the present state of work, the working range is only tested on oil with a residence time of less than six hours in sea water.