Abstract
Wetlands are an important carbon sink for greenhouse gases (GHGs), and embedding microbial fuel cell (MFC) into constructed wetland (CW) has become a new technology to control methane (CH(4)) emission. Rhizosphere anode CW-MFC was constructed by selecting rhizome-type wetland plants with strong hypoxia tolerance, which could provide photosynthetic organics as alternative fuel. Compared with non-planted system, CH(4) emission flux and power output from the planted CW-MFC increased by approximately 0.48 ± 0.02 mg/(m(2)·h) and 1.07 W/m(3), respectively. The CH(4) emission flux of the CW-MFC operated under open-circuit condition was approximately 0.46 ± 0.02 mg/(m(2)·h) higher than that under closed-circuit condition. The results indicated that plants contributed to the CH(4) emission from the CW-MFC, especially under open-circuit mode conditions. The CH(4) emission from the CW-MFC was proportional to external resistance, and it increased by 0.67 ± 0.01 mg/(m(2)·h) when the external resistance was adjusted from 100 to 1000 Ω. High throughput sequencing further showed that there was a competitive relationship between electrogenic bacteria and methanogens. The flora abundance of electrogenic bacteria was high, while methanogens mainly consisted of Methanothrix, Methanobacterium and Methanolinea. The form and content of element C were analysed from solid phase, liquid phase and gas phase. It was found that a large amount of carbon source (TC = 254.70 mg/L) was consumed mostly through microbial migration and conversion, and carbon storage and GHGs emission accounted for 60.38% and 35.80%, respectively. In conclusion, carbon transformation in the CW-MFC can be properly regulated via competition of microorganisms driven by environmental factors, which provides a new direction and idea for the control of CH(4) emission from wetlands.