Study on the mitigation effect of submerged vegetation on greenhouse gases emission from rivers

In order to reveal the role of ecological restoration of submerged plants in slowing down the release of greenhouse gases (GHGs) from rivers, the two rivers of Shengjiawan (with submerged plants growing) and Donglonggang (without submerged plants growing) were selected in Jiashan County, Zhejiang Province, and the fluxes of CO₂, CH₄ and N₂O were continuously monitored for 24 hours by the diffusion models. The results showed that except for the CO₂ absorption occurrence in Shengjiawan at 16:00, the three gases were supersaturated during the rest of the monitoring time, showing the release of GHGs to the atmosphere. In comparison, within 24 hours, the release of GHGs from Shengjiawan with submerged plants could be reduced by 89%. Based on the correlation analysis between gas release flux and environmental factors, it was found that in Shengjiawan, CO₂ emission flux was significantly negatively correlated with water temperature, pH and dissolved oxygen concentration, and positively correlated with redox potential. N₂O emission flux was positively correlated with water temperature, pH and dissolved oxygen concentration, and negatively correlated with redox potential. In Donglonggang, there was a significant positive correlation between CO₂ release flux and water temperature, a significant positive correlation between CH₄ release flux and water temperature and dissolved oxygen concentration, and a significant positive correlation between N₂O emission flux and water temperature.