Bioavailability of tri-CBs were increased by RAMEB or mechanical mixing.
Non-bioavailable tri-CBs could transform into bioavailable tri-CBs.
Degradation of tri-CBs could be enhanced by RAMEB or mechanical mixing.
Total amount and bioavailability of PCBs (Cl ≥ 4) were kept stable in all mesocosms.
Soil/slurry bacterial richness and diversity presented an overall downward trend.