Oil and Chemical Pollution最新文献

The impacts of oil and dispersed oil on freshwater ecosystems were examined in afield experiment conducted as part of the Freshwater Oil Spill Research Program. In July 1985, 3 m³ of Normal Wells crude oil were spilled on each of two fen lakes. The slick on one lake was treated with the dispersant Corexit 9550. Corexit 9550 was effective in removing the oil from the water surface even though wave energy was very low. The oil or dispersed oil had little detectable short or long term impact on all water quality parameters measured, or on the microbial populations and activities in the water column and sediments of both lakes. Untreated oil caused more damage than the dispersed oil to floating aquatic plants and the shoreline vegetation, but new growth within the affected areas was observed one month after treatment. Seasonal regrowth of vegetation in all areas affected by the treatments appeared normal. Our results suggest that the best response to oil contamination in isolated fen lakes is no action at all. However, floating oil or oil washed ashore could pose a significant threat to indigenous wildlife or its habitats. Under these conditions, chemical dispersion may prove to be an effective alternative when conventional control and recovery measures are not feasible.

The abundance and production of pelagic bacteria, phytoplankton primary production and chlorophyll content were studied in coastal waters receiving the effluent from an oil refinery in the Arabian Gulf. The area also receives unknown amounts of other effluents rich in organic matter and nutrients. The abundance of bacteria was measured by epifluorescent direct counts, and productivity was estimated by ³H-thymidine uptake measurements. The results showed a clear stimulation of the primary productivity as well as elevated amounts of chlorophyll a in the area receiving the effluent. Both bacterial abundances and production were an order of magnitude higher in a small area close to the refinery outlet, but dropped rapidly and reached background values outside an impacted area of c 10 km². The increased bacterial production in this area corresponded to a substrate demand of 4 to 11 tonnes of carbon per day, 4 to 12 times the daily discharge of some 0·9 tonnes of carbon in the form of petroleum hydrocarbons from the oil refinery. These data, plus the low petroleum hydrocarbon concentrations found in the sediments and in bivalves outside the impacted area, suggest that bacterial degradation of the petroleum hydrocarbons from the refinery could be a major process restricting the area impacted by oil pollution.

The Minerals Management Service estimates the likelihood of oil spills of 1000 barrels and greater occurring in association with the production and transportation of offshore oil on the US Outer Continental Shelf (OCS). The estimation process uses a spill rate constant, based on historical accidents, expressed in terms of number of spills per 10⁹ barrels of oil produced or transported. The mean spill occurrence estimate is obtained by multiplying the rate constant by the volume of oil projected to be handled. The probability of one or more spills occurring in a given production period is then estimated by using the mean number of spills in a Poisson process. The calculated occurrence rates of 0·60 spills per 10⁹ barrels produced on US OCS platforms and 0·67 spills per 10⁹ barrels transported in US OCS pipelines represent a decline of 40 and 58%, respectively, since last evaluated in 1983. Spill occurrence rates for worldwide tanker transport remained unchanged, since last evaluated in 1983, at 0·90 for ‘at-sea’ spills and 0·40 for ‘in-port’ spills.

Potential environmental impacts of materials discharged from oil and gas development and production platforms off the coast of southern California (Santa Maria Basin) are being monitored during an ongoing, long-term (fiveyear) field program. The study combines hypothesis testing of platform effects with basic research on the structure and dynamics of the regional ecosystem over a time series encompassing both seasonal and repeated annual scales. Oceanographic features and processes that are being measured focus on the benthos and include biological community indices and species abundances for hard-bottom and soft-bottom (macroinfauna and meiofauna) assemblages; levels and distributions of trace metals and hydrocarbons in bottom sediments, suspended particulates, animal tissues, and pore waters; water currents and otherphysical-oceanographicfeatures; various sedimentological properties (sediment grain size, total organic carbon, shear strength, distribution of mineral types, radioisotope profiles, and degrees of sediment mixing as a result of bioturbation); sediment and pollutant-transport processes; and animal-sediment-pollutant interactions. Synoptic measurement of these different environmental variables over the extended sampling period provides an opportunity to examine long-term variability in the benthic environment with respect to both natural and anthropogenic causes. Efforts to distinguish between natural variability and low-level cumulative impacts of drilling are given special attention.

Results obtained during the first two years of sampling provide a basis for beginning to understand environmental processes and relations important in detecting and interpreting any subsequent impacts caused by drilling activities in this complex and productive region of the California outer continental shelf and slope. Background chemical, physical, and biological data generated during this period demonstrate that impacts of discharges from oil and gas operations should be detectable, if they occur, and should be distinguishable from natural environmental variability. Small inputs of barium and petroleum hydrocarbons have been detected and appear to be associated with the minor drilling activities that have occurred in the area thus far, however, these initial inputs have not led to any noticeable biological impacts. These initial results are hopefully of value for two reasons: (1) in providing a summary of basic chemical, physical, and biological features of the benthic environment within the Santa Maria Basin; and (2) in presenting information on research strategies that should be considered in designing studies dealing with similar resource-management problems in other parts of the world.

Laboratory effectiveness tests are described for four classes of spill-treating agents; solidifiers, demulsifying agents, surface-washing agents and dispersants. Many treating agents in these four categories have been tested for effectiveness and the results are presented here.

Solidifiers orgelling agents solidify oil, requiring a large amount of agent to solidify oil—ranging between 16% by weight, to over 200%. Emulsion breakers prevent or reverse the formation of water-in-oil emulsions. A newly-developed effectiveness test shows that only one product is highly effective: however, many products will work, but require large amounts of spill-treating agent.

Surfactant-containing materials are of two types, surface-washing agents and dispersants. Testing has shown that an agent that is a good dispersant is conversely a poor surface-washing agent, and vice versa. Tests of surfacewashing agents show that only a few agents have effectiveness of 25–40%, where this effectiveness is the percentage of heavy oil removed from a test surface. Results using the ‘swirling flask’ test for dispersant effectiveness are reported. Heavy oils show effectiveness values of about 1%, medium crudes of about 10%, light crude oils of about 30% and very light oils of about 90%.

A vertical selective migration of low and medium molecular weight hydrocarbons is demonstrated in the depth of a tropical forest soil heavily impacted by a crude oil spill. An identical pattern of horizontal migration is observed in the lateral zone of the polluted area and in the sediments of a shallow river which received the contaminated water runoff of the forest. The differential migration, which is attributed to the chromatographic properties of the media, resulted in the formation of a residual contaminant similar in composition to a gas-oil cut. The environmental contamination by this fraction extended far beyond the area initially polluted by the crude oil.

Plaice (Pleuronectes platessa), dab (Limanda limanda) and sole (Solea solea), caught by netting in the vicinity of selected Southern North Sea gas production platforms, were assessed by an expert sensory panel for possible tainting (atypical flavour). Selected samples offish tissue and sediment were analysed for n-alkanes.

Any atypical flavours detected were classed as ‘slight’ on the scale used and were found in fish from both platform and reference sites. The incidence of these flavours, but not the mean intensity in affected fish differed between platform sites. When selected fish were assessed specifically for ‘oily’ flavour, only onefish was considered to have a ‘slight’ oily flavour. The levels offlavour detected by the expert panel were close to the detection threshold; it is unlikely they would be detected by the untrained consumer. None of the flavours detected were attributable directly to platform operations. Increased levels of petrogenic hydrocarbons in fish from platform sites were found but these levels were not associated with any impairment offlavour.

The contents of polycyclic aromatic hydrocarbons (PAH) were examined in surface sediments from the open Adriatic Sea. UV-fluorescence spectroscopy was used for the analysis, and continued emission spectra were scanned for the lower and higher aromatic fractions. The samples were collected in three seasons, December 1986, May 1987 and September 1987 on two transects between Yugoslavia and Italy. Higher values were found near the Italian coast. From spectral line shapes it is evident that there was no local source of pollution and that PAH are of petrogenic and pyrolytic origin. The spatial distribution of PAH contents is in good agreement with the dispersion pattern of recent sediments of the Adriatic Sea.

Comparative study of oil biodegradation in clayey and sandy mangrove soils shows that, during their emergence period, microorganism activity is related to the soil water content. Drying beyond a certain point prevents good nutrient circulation which may lead to a lack of nutrients at the soil-oil interface. An oleophilic fertiliser supplies nutrients which stimulate the biodegradation process. When the soil is swamped, oxygen is the main limiting factor for biodegradation. Thus, water level variation and soil porosity determine conditions which control the biodegradation activity of aerobic microorganisms.