The distribution of and biodegradation impact on spilled oil in sediments from Dalian Bay, NE China

Highlights: • Oil spill contamination in Dalian Bay is controlled by wind direction. • Spilled oil has migrated downward to 16 cm in last 3 years. • Extractable Organic matter content indicates four ranks of contamination. • Biomarker similarity between sediments and oil is correlated to contamination levels. • Biomarker compositions are partially affected by ongoing biodegradation. - Abstract: Three cores collected in the area of 16th July 2010 oil spill by box crab in May 2013 and July 2014 at the Dalian Bay have been geochemically characterized to investigate the fate of chemical components in sediments. The total organic carbon, extractable organic matter contents and biomarker compositions have been applied for the differentiation of alien organic matters from in situ ones and evaluation of the biodegradation impact. Multivariate statistical analysis suggests four groups of sediments. Except a few samples at deepest part of BQ050, majority samples have certain affinity with the spilled oil. The most contaminated sediments occur at site BQ050 and the spilled oil has migrated to 8–12 cm depth. The degree of contamination can be ranked by the similarity of molecular compositions with spilled oil. Variable biomarker components in sediment extracts were also altered by ongoing biodegradation.