Factors Causing Environmental Changes After an Oil Spill
Authors: Straughan Dale 
Published: December 2007

There are many and varied factors related to oil, biota, and the environment. And because individually or in combination those factors produce a highly complex situation, it is impossible to predict, except in produce a highly complex situation, it is impossible to predict, except in a general way, the impact of an oil spill.

Introduction

There is a widespread belief among a large portion of the population that after an oil spill the area will become desolate - never to recover again. When it does not happen, there is often an air of disbelief and confusion. This is partly because of apparently conflicting reports after oil spills. There is a demand for a cut-and-dried answer to problems - a "yes" or "no" - without any regard for the complexity of the matter. However, while general predictions can be made, there is no answer yet to the question, "What will be the environmental impact of an oil spill?" I plan to discuss what I consider to be the nine most plan to discuss what I consider to be the nine most important factors that individually and in combined interaction result in the recording of different changes after different oil spills.

The biological damage caused by an oil spill will be governed by a combination of several factors including:

(1) the type of oil spilled, (2) the dose of oil, (3) the physiography of the area of the spill, (4) weather conditions at the time of the spill, (5) the biota of the area, (6) the season of the spill, (7) previous exposure of the area to oil, (8) exposure to other previous exposure of the area to oil, (8) exposure to other pollutants, and (9) the treatment of the spill. pollutants, and (9) the treatment of the spill.

As will become obvious in the discussion that follows, even these categories are not cut and dried.

Type of Oil Spilled

This is probably the most important factor. Table 1 gives a summary of the circumstances and documented damage after six oil spills. The immediate damage was recorded as greatest after the two spills that involved diesel oil. The heavier oils had a smothering rather than a toxic effect in the intertidal zone. They also resulted in greater sea-bird mortality than the lighter diesel oils. Part of these differences are due to differences in composition of the oils involved and part to the differences in behavior of the oils. For example, Santa Barbara crude oil tends to float on the surface of the water and is relatively insoluble in water, but the No. 2 diesel oil spilled from the Florida spread rapidly through the water column. In the former instance, organisms at the water surface - the neuston and pelagic birds - and intertidal organisms are the main groups exposed to the oil whereas in the latter case the surface-dwelling organisms received relatively less exposure to oil, but the whole environment was exposed to the oil. The No. 2 fuel oil contained 41 percent aromatic hydrocarbons and no asphaltenes. The Santa Barbara crude is low in aromatic hydrocarbons" and is asphaltic.

Composition of the oil also governs any visible residue left after a spill. In June, 1970, oil was not immediately visible on the mud flats in Wilde Harbor, which was polluted by No. 2 diesel in Sept., 1969. However, when water accumulated in fresh footprints in the mud. an oil film was visible. In Santa Barbara, on the other hand. asphaltic deposits remain in crevices on the beaches not cleaned by Union Oil Co. of California and from natural seepage.

JPT

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