Oil and Chemical Pollution最新文献

The distribution of oil degrading bacteria (ODB) and its ratios to viable heterotrophic bacteria (CFU) and direct counts (AODC) were examined in relation to the surface currents of the western Caribbean Sea. High ODB/CFU and ODB/AODC ratios were found, suggesting that chronic sources of hydrocarbons in the region may have a larger impact than those in the southern Gulf of Mexico, where previous studies have been performed. It was concluded that, in western Caribbean waters, the distribution of oil degrading bacteria, or its ratios to CFU or AODC, could be useful indicators of chronic oil inputs originating at the east of the Caribbean Sea, as well as their motions afterwards.

Previous long-term tank experiments on the effects of oil-based drill-muds in sediments on the settlement and development of biota (Blackman, et al, 1983, Blackman, et al, 1988) are suspected to have suffered from container effects, reducing interstitial water exchange and promoting anaerobiosis. To counteract this, a system has been developed which allows vertical movement of a small proportion of the water entering the tank through the experimental sediments and substrate. An experiment lasting 130 days, with this system showed less evidence of anaerobiosis and confirmed results from previous experiments that there are differences in effect between diesel-based mud and alternative-based muds. A new type of alternative mud formulation, using an oil-in-water emulsion with a much lower base-oil content, was also tested and found to be intermediate in behaviour and effect between the control and conventional muds. To distinguish between toxic effects and those of organic enrichment, the control tank was treated with an artificial drill-mud formulated on medicinal, liquid paraffin. This developed a faunal assemblage different from that in other experimental tanks.

Oil spill trajectory and fates models typically follow a surface slick until it contacts a coastline, at which time the simulation ceases. The coastal zone oil spill (COZOIL) model described here is designed to simulate oil spill fates both before and after a coastal contact. Multiple discrete batches of oil (spillets) are used to represent the surface slick. Spillets are circular while offshore but become elliptical upon contact with the shoreline. Onshore-offshore foreshortening is governed by a balance between wind stress and gravity spreading forces, and results in alongshore spreading of the spillet. Evaporated hydrocarbons are accumulated from all sources during the simulation, with no spatial representation. Entrained oil offshore is represented by discrete particles which maybe advected by the local currents. Inside the surf zone, entrained oil takes on a continuous representation, discretized within individual alongshore grid cells. Transport in the surf zone is governed by a classical radiation stress formulation. Incorporation of water into surface oil (emulsification) is simulated offshore. De-emulsification (de-watering) is allowed to occur for oil which is on the foreshore or backshore. Oil coming ashore may be deposited on the foreshore or the backshore, or carried into coastal indentations (lagoons, ponds, or fjords). Each of the seven shoreline types represented in COZOIL is characterized by a unique set of parameters, including grain size, porosity, and a maximum oil thickness which the foreshore can retain. Oil on the foreshore penetrates into the underlying sediments at a rate dependent on sediment grain size and oil viscosity. Oil may also be carried into the beach groundwater system by wave overwash. Reflotation of surface oil occurs during rising tides. The model is inherently deterministic with respect to results of any single simulation. Stochastic oil distribution estimates are produced by combining the results of multiple simulations, each of which may be driven by a separate weather scenario.

The intense development of marinas, especially within estuaries on the coastline of southern England, has led to major inputs of potentially toxic organic compounds. During a research programme on the occurrence, transport and fate of volatile organic compounds within the estuarine water and sediments of Southampton Water, we discovered massive inputs of hydrocarbons, both during and after construction phases. In one instance, measurements made before development and at 3-monthly intervals over a 3-year period showed a 10-fold increase of a range of aromatics, alkanes cycloalkanes and organohalogens. Our investigations show that, during construction phases, the local aquatic environment becomes a major sink for anthropogenic wastes relating to construction activities. At post-construction phases, yachts and small boats continue to act as major sources of hydrocarbons to the estuary.

A study of the marine environment off a major oil refinery in the Arabian/ Persian Gulf was carried out in 1986. The study covers an area of some 100 km² and abundance and biomass of benthic fauna as well as oil content of sediments and bivalves were investigated. In addition some physicochemical parameters of water and sediments were measured. The distribution of the fauna corresponds well with the concentrations of oil in the sediment, and an area of 1 km² was considered severely contaminated while about 10 km² was moderately contaminated. This is a considerably smaller area than that found to be contaminated in a similar study in 1981, 5 years earlier. The reason for this is probably decreased quantities of petroleum hydrocarbons released via the effluent.

This paper describes the details of the physical fates submodel of a natural resource damage assessment model system for marine and coastal areas. The submodel computes the dynamic distribution of a spilled substance in three spatial dimensions using a combination of analytic and discrete numerical representations. The user inputs information to characterize the spill and the environment. The submodel then draws additional parameters from a chemical database, and proceeds to compute the dynamic distribution of the spilled substance in the environment. The results of the computations are shown on the computer terminal, and are written to an output file for subsequent input to the biological submodel.

The natural resource damage assessment model for coastal and marine environments (NRDAM/CME) provides a methodology for assessing natural resource damages following spills of toxic substances. The NRDAM/CME contains physical fates, biological effects and economic damages components. The biological effects submodel is described herein.

The biological effects submodel estimates direct mortality resulting from toxic concentrations of the spilled substance and lost production of organisms in the marine food web resulting from loss of food resources. Mortality and reduced productivity, are functions of concentration, time of exposure and temperature. Long-term losses include lost recruitment of larvae and juveniles into the adult population and lost future growth of adults. Using accepted fisheries models, catch losses at the time of the spill and into the future are estimated and passed to the economic damages submodel for valuation. For birds and mammals, both viewing and hunting losses are similarly calculated, as appropriate.

A system of coupled numerical models has been developed to supply natural resource damage assessments for spills of oil and hazardous substances in coastal and marine environments in the United States. The system, which operates on a microcomputer, is composed of physical fates, biological effects and economic damages submodels connected through intermediate data files. The system requests specified inputs from the user, and supplies additional detailed information from chemical, biological, and economic databases. Each submodel produces output describing the results of computations with in the submodel, the final output being a damage assessment (in US $) for a specific spill event.