The effectiveness of in-situ
bioremediation of
polycyclic aromatic hydrocarbons (
PAHs) may be inhibited by their low
aqueous solubility and strong absorption to soil constituents. The aim of this research was to evaluate the effect of water-extractable
organic matter (WEOM) from
manure compost on the biodegradation of various
PAHs. The
aqueous solubilities of
PAHs including
phenanthrene,
pyrene and
benzo[a]
pyrene under different concentrations of WEOM from
cow manure compost were initially evaluated. The contribution of WEOM on the degradation of
PAHs by
Sphingomonas sp. was then investigated.
Dissolution results confirmed the ability of WEOM to increase the apparent
solubility of the 3PAHs. Time course of biodegradation also revealed its positive contribution to their removal. For example, the degradation of
pyrene was 118% higher in the presence of 1000 mg-C L(-1) WEOM as compared to the
mineral salt medium (MSM) alone after 48 h incubation. In addition, degradation was 12% higher with WEOM than with Glucose-Ammonium
nitrate despite the more than 6 times higher cell concentration in the latter. WEOM from other
manure composts such as
chicken and pig were found to have the same effect. Finally, additional tests confirmed that high molecular weight WEOM (>1000 Da) contributed mainly to
solubility and biodegradation enhancements. On the basis of these results, the increase in apparent
solubility of
PAHs in WEOM
solutions may have a significant impact on their biodegradation. It is postulated that the application of WEOM-rich
manure composts may be extended in the in-situ
bioremediation of PAHs-polluted soil.
