RIASSUNTO
Abstract
Decisions about using dispersants are made in the context of reasons for treating spilled oil which threats to valuable habitat and nursery areas or to vulnerable early stages of marine life. The potential use of chemical dispersants raises some primary questions, principally: Are they effective? Do they reduce the potential damaged caused by spilled oil. What factors affecting toxicity of Chemical Dispersants and Dispersed Oil?
The present paper explains factors affecting the effectiveness and toxicity of oil spill dispersants using a case study of four different chemical dispersants recently used in Indonesia. Chemistry and physics of the dispersants are also presented in order to support evaluation of their effectiveness and toxicity properties.
Introduction
Decisions about using dispersants are made in the context of reasons for treating spilled oil. The image of a black, sticky mass covering a clean shore is dramatic enough, but there are often less visible incentives to respond to a spill, such as threats to valuable habitat and nursery areas or to vulnerable early stages of marine life.
Introduction of petroleum into the marine environment is a direct consequence of the production and transportation of crude oil and refined products. Even though natural seeps of crude oil occur in areas of the ocean floor and stable biotic communities are associated with them, the sudden introduction of high concentrations of hydrocarbon can kill or cause sublethal effects in some marine organisms. Nearshore marine waters and shallow fishing banks are also rich in a variety of less visible organisms. In addition to aesthetic and ecological concern, coastal regions can suffer economically from damage done by oil spills to recreation areas, harbor and vessels, commercial shellfish grounds, and intake sources for desalination and power plants.
In Indonesia the use of. oil spill dispersants is controlled by the Directorate General of Oil and Gas by which all dispersants produced or marketed should undergo the toxicity test. This toxicity test is conducted with regard to certain type of fish to determine the threshold limit, LC-50 of dispersants (PRASETYO, 1990). It is assumed generally, however, that the criteria for good oil dispersants are not only determined solely by their toxicity properties to marine species. Oil dispersants can be considered effective if they also have adequate dispersing quality. The dispersing quality of dispersants will also determine the rate of crude oil biodegradation which has been transform into micro droplets throughout the water column, since hydrocarbon-degrading microorganisms act mainly at the oil-water interface. The finer the droplets, means more effective the dispersants, the greater the surface area of oil available for microbial colonization. Availability of increase surface area by dispersing the oil throughout the water column should, therefore, accelerate crude oil biodegradation.
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