Polycyclic aromatic hydrocarbons concentrations in the original (untreated) column soil and in samples collected from Port A of the control and biostimulated columns at day 534. Note that phenanthrene concentration is plotted separately. Error bars represent one standard deviation. The letters above the bars represent the results of significance analyses using the Tukey-Kramer Honestly Significant Difference (HSD) test. For each analyte, conditions sharing a common letter are not significantly different. Abbreviations: NAP – naphthalene, ACE – acenaphthene, FLU – fluorene, PHN – phenanthrene, ANT – anthracene, FLA – fluoranthene, PYR – pyrene, BaA – benz[a]anthracene, CHR – chrysene, BbF – benzo[b]fluoranthene, BkF – benzo[k]fluoranthene, BaP – benzo[a]pyrene, BgP – benzo[ghi]perylene.