Study On The Changes And Mechanisms Of Greenhouse Gas Emissions At The Water-air Interface During Plant Purification Of Black-odorous Water

The greenhouse effect and water pollution are relatively serious ecological and environmental issues in China’s urbanization process.The synergistic mechanism of"pollution reduction and carbon reduction"in the ecological restoration of black-odorous water has attracted widespread attention from scientists.In this study,three kinds of black-odorous water with low concentration,medium concentration and high concentration were simulated by adding carbon（glucose）,nitrogen（urea）and phosphorus（Monopotassium phosphate）of different mass,and four treatments were set,namely Vallisneria natans（Lour.）H.Hara,Iris pseudocorus L.,Vallisneria natans（Lour.）H.Hara+Iris pseudocorus L.（intercropping）and control treat（no plant）,Analyze the dynamic changes and influencing factors of three greenhouse gases（CO₂,CH₄,and N₂O）at the water air interface during the purification of black and odorous water bodies with different plant treatments;Simultaneously analyze the cumulative emissions of three greenhouse gases（CO₂,CH₄,and N₂O）and their global warming potential（GWP）.The main conclusions are as follows:（1）The effectiveness of different plant treatments in purifying black-odorous water varies,and Vallisneria natans（Lour.）H.Hara treatment has the best purification effect among the four treatments,especially when purifying high concentration black-odorous water.After the complete elimination of black-odor in high concentration black-odorous water（on the 24th day of purification）,the dissolved organic carbon（DOC）,ammonium nitrogen（NH₄⁺-N）,and available phosphorus（AP）concentrations in the water treated with Vallisneria natans（Lour.）H.Hara were lower than those in the Iris pseudocorus L.treatment,Vallisneria natans（Lour.）H.Hara+Iris pseudocorus L.（intercropping）,and control treatment.（2）During the 24 daies purification experiment,the cumulative greenhouse gas emissions and GWP of different plant treatments were different.The cumulative CH₄emissions and GWP of the Vallisneria natans（Lour.）H.Hara+Iris pseudocorus L.（intercropping）were lower than those of the Vallisneria natans（Lour.）H.Hara and Iris pseudocorus L.treatments,while the CO₂ and N₂O cumulative emissions of the Vallisneria natans（Lour.）H.Hara treatment were the lowest.（3）The degree of water pollution varies,and the cumulative emissions and GWP of greenhouse gases also vary.Overall,the cumulative emissions of CO₂,CH₄,N₂O and GWP at the water-air interface of low,medium,and high concentration black-odorous water are in the order of high concentration>low concentration and medium concentration.The CH₄ cumulative emissions and GWP are the lowest in the medium concentration treatment,while the CO₂ and N₂O cumulative emissions are the lowest in the low concentration treatment.Indicating that inputs with high levels of pollution correspond to high greenhouse effects,"reducing pollution and carbon emissions"can synergistically increase efficiency.（4）The results of correlation analysis showed that the main factors affecting the three greenhouse gas emission fluxes of the four treatments were reaction substrates and redox conditions,but different treatments had different influencing factors.These factors mainly included carbon and nitrogen nutrients,chlorophyll a（Chl-a）concentration,dissolved oxygen（DO）concentration,oxidation reduction potential（ORP）,and p H.