Biochar-mediated remediation impacts on nitrogen cycling bacteria and ammonia monooxygenase activity in crude oil polluted soil

This study adopted an ecosystem services approach to pollution management by investigating the impact of biochar-mediated remediation on soil nitrogen, abundance of nitrogen cycling bacteria and the activity of ammonia monooxygenase (AMO) enzyme in petroleum-polluted soil using two biochar types applied at two treatment levels with monitoring over 15 weeks. The corn cob-derived biochar (CDB), generally, had a stronger restorative effect on soil ammonium nitrogen, nitrate and total organic nitrogen concentrations than the bone-derived biochar (BDB). Both biochar types had a more robust impact on restoration of Nitrosomonas, Nitrobacter and Azotobacter abundance (with the re-establishment of pre-pollution levels) than on Rhizobium and Pseudomonas aeruginosa. Biochar amendment restored the activity of AMO enzyme in the soil by week 15. The CDB (72.4% – 73.7%) showed more effective total petroleum hydrocarbon (TPH) elimination capacity than the BDB (51.1% – 57.7%). Biochar amendments exhibited great potential for restoration of nitrogen cycling while facilitating remediation of petroleum-polluted soils.