Abstract

Bioremediation is a promising technique for reclamation of oil polluted soils. In this study, six methods for
enhancing bioremediation were tested on oil contaminated soils from three refinery areas in Iran (Isfahan,
Arak, and Tehran). The methods included bacterial enrichment, planting, and addition of nitrogen
and phosphorous, molasses, hydrogen peroxide, and a surfactant (Tween 80). Total petroleum hydrocarbon
(TPH) concentrations and CHEMometric analysis of Selected Ion Chromatograms (SIC) termed
CHEMSIC method of petroleum biomarkers including terpanes, regular, diaromatic and triaromatic steranes
were used for determining the level and type of hydrocarbon contamination. The same methods
were used to study oil weathering of 2 to 6 ring polycyclic aromatic compounds (PACs). Results demonstrated
that bacterial enrichment and addition of nutrients were most efficient with 50% to 62% removal
of TPH. Furthermore, the CHEMSIC results demonstrated that the bacterial enrichment was more efficient
in degradation of n-alkanes and low molecular weight PACs as well as alkylated PACs (e.g. C3–C4
naphthalenes, C2 phenanthrenes and C2–C3 dibenzothiophenes), while nutrient addition led to a larger
relative removal of isoprenoids (e.g. norpristane, pristane and phytane). It is concluded that the CHEMSIC
method is a valuable tool for assessing bioremediation efficiency.