Effects of plant species on CH4 emission from integrated vertical subsurface flow constructed wetlands

Methane (CH4) emission from constructed wetlands (CWs) has increased the amount of greenhouse gases (GHG) and raised environmental concerns. The plant species could significantly affect the CH4 emission in integrated vertical subsurface flow constructed wetlands (IVSSF CWs). This study evaluated the removal efficiency of water pollutants and determined the influence of plant species on CH4 fluxes in IVSSF CWs planted with Cyperus alternifolius, Canna indica, Acorus calamus, and Scirpus tabernaemontani. Result indicated that the pollutant removal efficiency in IVSSF CWs planted with C. alternifolius was apparently higher than that in the wetlands planted with the three other plants. The mean removal efficiencies in CWs planted with C. alternifolius were 84.46% for chemical oxygen demand (COD), 85.80% for NH4-N, 82.94% for total nitrogen, and 94.87% for total phosphorous. The average CH4 fluxes were 5.45 mg m(-2) h(-1) (A. calamus), 2.49 mg m(-2) h(-1) (S. tabernaemontani), 9.26 mg m(-2) h(-1) (C. indica), and 3.25 mg m(-2) h(-1) (C. alternifolius). The CH4 fluxes in IVSSF CWs planted with C. alternifolius, C. indica, and S. tabernaemontani were significantly correlated with temperature (P < 0.05). Moreover, the CH4 fluxes in IVSSF CWs planted with C. indica and A. calamus significantly differed between up-flow and down-flow chambers (P < 0.05). The relationship between CH4 flux and removal loading of COD was also analyzed. S. tabernaemontani and A. calamus were found to be the optimal plants for COD removal in IVSSF CWs in summer and winter, respectively. The results can be helpful for plants optimization in CWs and provide the data support for the control of GHG emission.