Fig. 4. Gas chromatograph–mass spectrometry (GC–MS) data of oil residue extracted from sediment before experiment on Day 0 and the control and six treated sediments on Day 45. Peak identification of hydrocarbon components is shown in GC–MS data of oil residue on Day 0. The y axes of all graphs are in the same range. C, control; Ip, Inipol; Os, Osmocote; SN, soluble nutrients.