The effect of modified biochar on methane emission and succession of methanogenic archaeal community in paddy soil.

Modified biochars have been widely applied in ameliorating environmental problems. However, the effect of modified biochar on suppressing CH emission in rice paddy soil is not fully understood. In order to further study CH regulation in paddy soil via the modification of biochar and explore its influence on key archaeal communities, two modified biochars were generated with the pre-treatment of nitric acid (NBC) and hydrogen peroxide (OBC), respectively, and a control group was setup with water-washed biochar (WBC). Results showed that NBC significantly suppressed CH emission, followed by OBC and WBC, while NBC promoted the CO emission. Besides, the addition of biochars inhibited the accumulation of acetate and H in rice paddy soil, especially in the NBC treatment. 16S rRNA gene sequencing revealed that biochars amendment increased α-diversity of archaeal community and the modified biochars could mitigate the loss of α-diversity in the early stage of anaerobic incubation. Additionally, NBC amendment largely declined the relative abundance of methanogens (especially Methanosarcina) in archaeal community, while OBC and NBC promoted the relative abundance of Candidatus_Methanoperedens. Via Spearman's correlation coefficient analysis, NBC had positive correlations with Methanosaeta, and OBC showed a negative correlation with Methanocella. Overall, this study provided a practical way to regulate the CH emission and associated methanogenic archaea via the amendment of different modified biochars in rice paddy soil.