Oil and Chemical Pollution最新文献

This paper discusses the economic damages submodel of the natural resource damage assessment model for coastal and marine environments (NRDAM/CME). The economic damages submodel uses the output of the biological effects submodel and information provided by the user to measure damages, which are defined as the in-situ lost use value of the injuries to the specific categories of publicly controlled natural resources included in the model. Damages are measured for injuries to (1) lower trophic biota, (2) commercial and recreational fisheries, (3) waterfowl, shorebirds and seabirds, (4) marine mammals (fur seals) and (5) public beaches. The measurement of damages includes those resulting from short-term, long-term, direct and indirect injuries to natural resources. The paper develops the concepts underlying the measurement of damages and explains the data sources and methodology used to implement the economics submodel. Example applications of use of the economics component to generate pollution damage functions are presented in a companion paper in this issue.

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.

A chemical database (PHYSCHEM) was created to supply parameters to a natural resource damage assessment model for marine and coastal environments. The database contains 18 parametric entries for each of 469 substances, including 9 crude oils and petroleum products. Sources of parameters are also coded into the database. Procedures for selecting parameters from databases or estimating parameter values were quasi-automated through a classification coding system, such that chemicals could be automatically keyed to the correct estimation procedures. Quality control of physical/chemical parameters was achieved by comparing parameters contained in reference databases and literature with values obtained through various estimation procedures. Toxicological parameters were drawn from databases using an automated decision tree, based on levels of quality control applied to the original data. The final database is available to the public in hard copy and on floppy disk.

Mass transfer coefficients of the soluble volatile portion of crude oils from distilled and saline (44 g litre⁻¹) waters to the atmosphere were determined at 25, 35 and 45°C. The crude oils used were of API° ranging from 11–28. The calculated activation energies of crude volatilization from solutions were in the range of 10 kcal. A linear relationship between mass transfer coefficients in both distilled and saline waters was obtained. In addition, a regression model was presented for the calculation of the mass transfer coefficient in terms of API° of the crude, as the only characterization parameter of the oil, temperature and ionic strength of the salt. The model has a powerful predictive capability with an average absolute deviation of 3·2% in the range studied.

There are many sources of oil pollution in the Red Sea and, therefore, a considerable potential for damage to coastal systems where spilled oil tends to accumulate. Seagrasses are very common in the shallow, sheltered areas along the shorelines, and the seagrass beds can thus be classified as highly vulnerable. Depending on the degree of oiling, short-term effects on the seagrass plants can be expected, particularly when the above-ground plant parts (the leaves and leaf sheaths) are in direct contact with floating oil. However, there is no evidence of significant long-term or persistent effects, unless the beds are completely covered with oil or below-ground plant parts are affected by oil penetration into the sediment.

As a consequence of the sensitivity of specific algal and faunistic components of the seagrass system to acute and long-term exposures to oil, adverse population changes may persist for long periods of time. The ultimate effects on the seagrass system largely depend on its complexity and the vulnerability of the habitat. The complexity of the system is determined by the number of vertically arranged vegetation layers, each characterized by its own specific floral and faunal assemblages. The number and characteristics of these layers are generally related to the seagrass growth form, rather than to the seagrass species. In the intertidal zone the complexity of the system increases with percentage water coverage and in the sublittoral with increasing depth; a maximum usually occurs a few metres below extreme low water level. Thus, the most complex and susceptible part of the system tends to be situated at depths where the likelihood of serious long-term exposure to spilled oil and subsequent damage is small.

Seagrass in the intertidal area forms a definite buffer between floating oil and the community components under the leaf canopy. Acute exposure incidents will lead to a simplification of the community structure. Chronic exposure will lead to a gradual modification of the structure and basic processes. However, as long as the frame of the community, i.e. the seagrass itself, is not seriously affected, the system is able to regain stability more easily than other, unvegetated parts of the coast. Recovery times are estimated to be one to a few years. Where the seagrass itself is damaged recovery may last several decades.

Proper selection of spill-combat methods may effectively prevent oil from reaching the vulnerable shorelines. Usage of dispersants offshore and mechanical clean-up on- and near-shore are discussed in view of their potential for additional damage to the seagrass system.

This paper describes a preliminary effort to validate the Natural Resource Damage Assessment Model for Coastal and Marine Environments (NRDAM/ CME). After describing the general requirements that the model should meet, the problems inherent in validating the NRDAM/CME by a retrospective comparison with the results of field studies are reviewed. Due to these problems, an order-of-magnitude standard of accuracy is argued to be appropriate. Comparisons of the model results with those of selected, field studies suggest that the NRDAM/CME provides reasonable results given this standard. In light of the fact that this preliminary validation effort is based on the use of only readily available information for a few studies, additional efforts are in order to validate the model and refine it, as appropriate.

When oil is discharged into sea-water, it is subject to several processes including spreading, drifting, evaporation, dissolution, photolysis, biodegradation and formation of both oil-in-water and water-in-oil emulsions. Our present understanding of these processes, individually and in models, and our ability to express their rates quantitatively are reviewed, and suggestions are made for future research. Emphasis is placed on developing a deeper understanding of oil-water partitioning in dilute oil-in-water emulsions with a view to improving estimations of oil toxicity to marine biota.

Scientific monitoring of oil spills is required to provide information for the effective planning of countermeasures. In the past, lack of integration of the monitoring effort has made the correlation and interpretation of data difficult. We reviewed (through interviews and questionnaires) the methodology of shipboard monitoring of oil spills to help in an evaluation of whether a fully integrated oil monitoring system is necessary and feasible. Most scientists required 2–3 days to mobilize their equipment for monitoring accidental oil spills. A major problem was acquisition of an appropriate vessel. Little experience with monitoring of hydrocarbons in air was described. There were very diverse approaches to slick observation and sampling. Slick sampling was ineffective in many cases. There was generally poor documentation of weather and sea state during accidental spills and therefore difficulty in the interpretation of oil observations. Fewer than half of the respondents had used in situ methodsfor monitoring oil in the water column. Most relied on discrete sampling, with subsequent analysis ashore. In situ methods are now more popular, but require more rigorous quality control programs than those used during past spill responses. Although computerized sensor systems have been developed for water column monitoring, the data from these systems are not integrated in real time with observations on the location and thickness of the slick and other data on sea state. Depending on the objectives of oil spill monitoring, a fully integrated shipboard oil monitoring system may reduce or eliminate many of the problems currently experienced by scientists working on oil spills.