清淤和曝气对城市黑臭河流生态系统温室气体排放影响的机理研究

The impact of human activities on greenhouse gas emissions from urban rivers has attracted wide attention. However, the impact of human activities on greenhouse gas emissions from urban rivers has not been quantitatively verified in the field experiment. In addition, the contribution of anthropogenic disturbances to greenhouse gas emissions from urban river ecosystems is not clear. We will conduct this project in urban black-odor river ecosystem, which is the most widely distributed in subtropical China. We will change sludge dredging and aeration in the control experiments. We will measure physicochemical properties of water and sediment, microbial communities in sediment, and CO2, CH4 and N2O fluxes to study the effects of human disturbance on greenhouse gas emissions and discuss their contribution to different greenhouse gas emissions from different levels of sludge dredging and aeration in black-odor river ecosystems. The objectives of this project are to investigate the response of the greenhouse gases to sludge dredging and aeration in the black-odor river, reveal the contribution and differences of sludge dredging and aeration and their combined effects on greenhouse gas emissions in the black-odor river, which are crucial to understanding the mechanisms of anthropogenic disturbances to carbon cycles greenhouse gas emissions in urban river ecosystems, estimating greenhouse gases emissions in global urban ecosystem, improving the treating effects of the black-odor river.

人类活动对城市河流生态系统温室气体排放研究受到广泛关注。然而，人类活动对城市河流温室气体排放的影响程度并未得到定量验证。此外，关于人类活动干扰对城市河流生态系统温室气体排放量的贡献也不清楚。本研究拟以城市黑臭水体生态系统为例，通过控制不同清淤水平和曝气强度，测定水体和底泥的理化性质及底泥微生物群落变化，监测黑臭河道CO2、CH4和N2O三种温室气体通量，从不同清淤水平和曝气强度探讨人为干扰程度对黑臭河道温室气体排放的影响，揭示清淤和曝气及其共同影响对黑臭河道不同温室气体排放量的贡献。本项目旨在阐明清淤和曝气等人为干扰对黑臭河道温室气体通量影响的内在机制，揭示清淤和曝气及其共同影响对黑臭河道温室气体排放量的贡献及其差异，为估算全球城市生态系统温室气体排放量提供理论基础，为提高黑臭河道治理效果提供数据支撑。

30min、60min曝气不影响水-气界面的气体交换，曝气前后通量变化不显著。清淤0.5-4 cm后，三种温室气体通量先增加后减小。清淤和曝气后，各处理在净化第15天已经把水体净化完全。在富营养化水体净化过程中，水-气界面CO2净排放通量最小的为铜钱草处理，为-44.09 mg·m-2·h-1；水-气界面CH4净排放通量最小的为铜钱草处理，为-0.01mg·m-2·h-1；水-气界面N2O净排放通量最小的为水竹、竹叶眼子菜和黑藻组合的处理，为-0.03mg·m-2·h-1。水-气界面GWP最小的为铜钱草处理，为38906.89 mg/m2。清淤曝气后水-气界面CO2 、CH4、N2O比净化前降低，水-气界面CO2排放通量在36.58-257.28 mg.m-2.h-1之间，呈现先下降后上升的变化趋势。水-气界面CH4、N2O平均排放通量在0.02-0.42 mg.m-2.h-1、0.06-2.7 mg.m-2.h-1之间，都呈现先上升后下降再上升的变化趋势。在植物净化过程中，水、土理化性质与温室气体排放通量构建的相关分析表明，水体底泥溶解性有机碳和藻蓝蛋白与CO2排放通量呈显著正相关，溶解氧、 pH 底泥NH+ 4-N、底泥TN和CO2排放通量呈显著负相关；水温、底泥NH+ 4-N、底泥速效磷、底泥DOC 与CH4排放通量呈显著正相关；Chla和底泥DOC与N2O排放通量呈显著正相关，水体NH+ 4-N和底泥总氮与其呈显著负相关。多元逐步回归方程结果表明，底泥溶解性有机碳（DOC）、底泥铵态氮（NH+4-N）、水体pH、水体溶解氧（DO）、水体叶绿素（Chla）影响着水-气界面CO2 、CH4、N2O排放通量，每个因子对三种温室气体通量的影响程度不同。其中底泥溶解性有机碳（DOC）对水-气界面CO2 、CH4、N2O排放通量都存在显著的促进作用。