EVALUATION OF OIL CONTAMINATION AT A SANDY SHORELINE ?A NOVEL FLUOROMETRIC ON-SITE ANALYSIS METHOD FOR OIL IN PORE WATER

Abstract

An estimated 12,547 kilo liters (10,900 M/T) of crude oil was spilled in December 2007 after the collision between the oil tanker Hebei Spirit and a barge carrying a crane, heavily impacting more than 70 km of western coastline of Taean, Korea. It was somewhat problematic, however, to evaluate chemically oil contamination of coarse shoreline sediment, such as sand or pebble beaches. This is because quantification of oil in sediment is highly dependent on grain size and on the weight of sediment itself. The contamination level and extent at the impacted shorelines could not be clearly characterized by conventional quantification methods due to the varying size of sediment grains in the area, ranging from clay/silt to pebble. We found that, as an alternative, contamination at a sandy shoreline can be better evaluated by measuring the oil content of pore water than by measuring oil concentrations in sediments. In this presentation, a novel fluorometric on-site analysis method for oil in pore water is introduced. The contamination level and temporal variation of dissolved/dispersed oil in pore water was investigated on site using a portable fluorometer after hexane extraction of oil. The oil content of pore waters at 28 beaches exposed to the oil spill was measured monthly or in a seasonal basis until January 2010. More comprehensive examination of oil contamination of pore water was conducted at selected beaches. The fluorescence detection method was also compared with the conventional laboratory technique of total petroleum hydrocarbon analysis using gas chromatography (GC). The fluorescence method for detection of oil was capable of generating data comparable to that of GC, but more rapidly and cost-effectively.