Petroleum hydrocarbon contaminations in the intertidal seawater after the Hebei Spirit oil spill – Effect of tidal cycle on the TPH concentrations and the chromatographic characterization of seawater extracts

Abstract

In December 2007, the oil tanker Hebei Spirit released approximately 12,547,000 L of crude oil off the west coast of Korea, impacting more than 375 km of coastline. The seawater TPH concentrations immediately after the spill ranged from 1.5 to 7310 μg L−1, with an average of 732 μg L−1. The concentrations appeared to decrease drastically to 2.0–224 μg L−1 in one month after the spill. The TPH concentrations in seawater fluctuated with time thereafter because of the remobilization of oil by continuing shoreline cleanup activities and subsequent wave/tidal actions. Seawater TPH concentrations were much higher during high tide than during low tide due to the resuspension of stranded oil. The variation of TPH levels in seawater also matched the spring-neap tidal cycle in the study areas for the first three weeks of the study. Comparisons of the gas chromatograms of the seawater with the water accommodated fraction and the cargo oil indicated that seawater samples were contaminated mainly by the dispersed droplets of spilled oil. One year of monitoring revealed that the oil content in seawater had clearly decreased at most sites, although some regional fluctuations of oil contamination were noted until June 2008.