Variations in the bioavailability of polycyclic aromatic hydrocarbons in industrial and agricultural soils after bioremediation

- Variation of PAH bioavailability in original and post remediated soils was studied.
- Bioavailability of 3- and 4-ring PAHs were decreased in MPG and agricultural soils.
- Rapidly desorbing fractions of 5- and 6-ring PAHs changed little in MGP soil.
- Tenax was proved to be a more sensitive method than SPME in agricultural soil.
- Tenax and SPME have the potential to assess bioavailability of PAHs in MGP soil.

The aim of this study was to demonstrate the variations in bioavailability remaining in industrial and agricultural soils contaminated by polycyclic aromatic hydrocarbons (PAHs) after bioremediation. After inoculation of Mycobacterium sp. and Mucor sp., PAH biodegradation was tested on a manufactured gas plant (MGP) soil and an agricultural soil. PAH bioavailability was assessed before and after biodegradation using solid-phase extraction (Tenax-TA extraction) and solid-phase micro-extraction (SPME) to represent bioaccessibility and chemical activity of PAHs, respectively. Only 3- and 4-ring PAHs were noticeably biodegradable in the MGP soil. PAH biodegradation in the agricultural soil was different from that in the MGP soil. The rapidly desorbing fractions (Frap) extracted by Tenax-TA and the freely dissolved concentrations of 3- and 4-ring PAHs determined by SPME from the MGP soil decreased after 30 days biodegradation; those values of the 5- and 6-ring PAHs changed to a lesser degree. For the agricultural soil, the Frap values of the 3- and 4-ring PAHs also decreased after the biodegradation experiment. The Tenax-TA extraction and the SPME have the potential to assess variations in the bioavailability of PAHs and the degree of biodegradation in contaminated MGP soils. In addition, Tenax-TA extraction is more sensitive than SPME when used in the agricultural soil.