Oil droplets may adhere to particulate matter in the water column according to equilibrium partitioning between the water and particles. Particulate matter bound with oil can penetrate deeper into the water column, carrying specific toxic components directly to sediments. The sources of both oil and the particulate materials affect the interaction, while the density of the combined particles ultimately determines the position of oil-sediment particles in the water column. Eventually, oil-sediment agglomerates and particles bound with oil settle out to bottom sediments. The oil-sediment agglomerate may be disturbed when large currents occur. Animals living in or near sediments may also mix them while burrowing, feeding, and passing water above the sediment layer.
Oil is usually spilled over an extended period of time and into a current of water. The transport and weathering mechanisms described above are usually in effect simultaneously. Physical-chemical forces determine oil distribution such as on a water surface, along a shoreline, within the water column, or in the sediment. Chemical and biological reactions further change the composition of spilled oil. Ultimately, both the distribution and composition of spilled oil determine the impacts observed for different species and their habitats.
Was this article helpful?