On January 31, 2014, oil spill accident occurred in Yeosu, South Korea. By the accident, total 800-899 ㎘ of oil from the pipeline was spilled into the sea. PAHs(Polycyclic aromatic hydrocarbons) are one of the most widespread organic pollutants. Although they represent less than 2% of oil bulk composition, they can affect marine environment due to their persistency and toxicity. Through emergency marine pollution impact assessment, KIOST(Korea Institute of Ocean Science & Technology) reported PAHs and TPH(Total Petroleum Hydrocarbon) in seawater, porewater and marine organisms collected from the surrounding area. But sedimentary PAHs was not reported regardless their longer persistency rather than PAHs in seawater and marine organisms. Thus this study is carried to know how much the spilled oil remain through monitoring the residual level of PAHs in intertidal sediments around Gwangyang bay.
The surface sediments were collected at 40 sites with stainless spoon on May 29-30, Aug 11-12, Nov 8-9, 2014 and Feb 5-6, May 16-17, 2015. Sixteen and alkyl PAH concentrations during five investigation period ranged from 137 to 216 ng/g dw with a mean value of 178 ng/g dw and 101 to 134 ng/g dw with a mean value of 119 ng/g dw respectively. This values are median level compared to those in Korean coastal area. Sites adjacent the accident area were less contaminated excluding site 12 and 25 on every survey. High PAH concentrations were reported at the southern sites of Yeosu.
From principal component analysis, the southern Namhae and Yeosu area showed high loading value in high molecular weight PAHs, whereas Hadong and Gwangyang area showed in alkyl PAHs especially naphthalene and flourene. Through the analysis of PAH source recognition using Flr/Pyr and Phe/Ant ratio, most of sites showed pyrolytic origin and several sites showed both of pyrolytic and petrogenic source. However, there was no petrogenic source among all sites. Furthermore PAH oil fingerprinting analysis was carried out with D2/P2(C2-DBT/ C2-Phe) and D3/P3(C3-DBT/C3-Phe) ratio. Stranded oil collected in SINDUK 5 days after the accident and Basrah light crude oil known as spilled oil in this accident seemed to be same through the double ratio value. However, all samples showed the index value out of the ranges between SINDUK stranded oil and Basrah light crude oil, which indicated that the spilled oil was removed.
Meanwhile, total PAH concentrations in all samples did not exceed ERL and ERM values, so the biological effects by PAHs were little in this area.