Effect of Cipangopaludina chinensis and diversity of plant species with different life forms on greenhouse gas emissions from constructed wetlands

Greenhouse gas emissions (GHG) from Constructed wetlands (CWs) for treating wastewater have been largely focused on. Previous studies have demonstrated that plant species diversity significantly affects GHG. However, the effect of the diversity of plant species with different life forms and benthic organisms on GHGs from CWs remains unclear. In this study, we selected three common aquatic plant species with different life forms (submerged, free-floating, emergent) for diversity configuration (one, two, three species richness and all seven combinations; six replicates), with C. chinensis added to half the replicates. Results showed that: (1) in systems without C. chinensis, high plant species richness significantly increased CO2 emissions and GWPCH4+N2O+CO2, as well as CO2 emissions per unit N removal and GWPCH4+N2O+CO2 per unit N removal, the presence of Acorus calamus increased CO2 emissions by 77 % and GWPCH4+N2O+CO2 by 72 %, respectively, while the presence of Pistia stratiotes significantly reduced N2O emissions by 41 %; (2) in systems with C. chinensis, the presence of P. stratiotes significantly reduced N2O emissions by 73% and GWPnon-CO2 by 68 %, respectively; (3) plant species identify did not affect GWPCH4+N2O+CO2 per unit N removal and GWPnon-CO2 per unit N removal in systems with or without C. chinensis. In summary, adding C. chinensis affected the effect of plant species identity on GHGs from CWs. Thus, we suggested that establishing communities with low plant species richness and proper species (such as P. stratiotes) could improve pollutant removal rate (TIN) and reduce GHGs in CWs.