Effects of H<sub>2</sub>O<sub>2</sub>-modified Rice Husk-Derived Biochar on Nitrification and N<sub>2</sub>O Emission from Water by an Isolated Heterotrophic Nitrifying Bacterium

In order to explore the effect of biochar on nitrification and N 2 O emission from water, the indoor incubation experiment was carried out after incorporating the pristine biochar (BC) or H 2 O 2 -modified rice husk-derived biochar (20% H 2 O 2 -BC and 30% H 2 O 2 -BC) combined with the screened heterotrophic nitrifying bacterium into the simulated wastewater.The dynamic changes of inorganic nitrogen contents, pH, bacterial amount, and N 2 O emission of the incubation system were analyzed.Results showed that compared with BC, the amount of acidic oxygen-containing functional group of H 2 O 2 -modified biochars increased by 24.24%~26.98%,while the amount of alkaline oxygen-containing functional group, pH, and the specific capacitance significantly decreased by 22.16%~27.29%,2.54~2.68,and 15.90%~30.94%,respectively.H 2 O 2 -modified biochars significantly inhibited nitrification driven by heterotrophic nitrifying bacterium compared with BC.Moreover, the 16-h cumulative N 2 O emission of the treatments with 20% H 2 O 2 -BC or 30% H 2 O 2 -BC addition (0.0516 and 0.0525 μg N 2 O/100 mL solution, respectively) were significantly higher than that with BC addition (0.0355 μg N 2 O/100 mL solution).Correlation analysis showed that the cumulative N 2 O emission of the treatments with 20% H 2 O 2 -BC or 30% H 2 O 2 -BC addition was significantly positively correlated with NH 2 OH concentration in incubation system (r = 0.455 and 0.497, respectively), and showed no significant correlation relationship with NO 2 --N (p<0.05).