Chemical evolution of Macondo crude oil during laboratory degradation as characterized by fluorescence EEMs and hydrocarbon composition

► The chemical evolution and degradation pathways of Macondo crude oil were examined. ► Variations in fluorescence EEMs, n-alkanes and PAHs were quantified. ► Major oil components had their Ex/Em maxima at 226/328, 262/315, and 244/366 nm. ► Average degradation half-life of oil components was 3-20 d. ► Dispersant appeared to change the chemical characteristics of oil and its degradation.