不同水生植物对富营养化水体释放气体的影响

摘要

Denitrification and emission of greenhouse gases and oxygen are all important biochemical processes occurring in aquatic ecosystems. To define extent of the impact of aquatic plants, relative to type, on these processes, dynamics of N2 , CH4 , O2 , CO2 and N2 O emissions from eutrophic waters in Caohai of Lake Dianchi, rank with emergent plants ( Acorus calamus) , floating⁃leaved plants ( Nymhaea tetragona, Nelumbo nucifera) , floating plants ( Eichhornia crassipes) and submerged plants ( Myriophyllum verticillatum, Hydrilla verticillata) and in control ( waters without plants) were stud⁃ied in July and August, 2012. Gases released from the waters were in⁃situ collected using a self⁃developed bubble trapping device, while water temperature, dissolved oxygen (DO), oxidative redox potential (ORP) and pH were also measured. Results show that the gas emitted from the waters with or without aquatic plants, were composed mostly of N2 , CH4 and O2 , and the rest of CO2 and N2 O. The submerged plants obviously improved O2 releasing process via photosynthesis, resul⁃ting in higher gas emission rate and higher emission fluxes of various fractions of gases. The leaves of Nymhaea tetragona, Nelumbo nucifera, and Eichhornia crassipes created shadow over the water surface, thus decreasing photosynthetic capacity of algae in the water, and consequently the gas emission rate of the water, with its median being even lower than that in the control. Moreover, the shadow also reduced emission fluxes of various fractions of gases. No significant difference was found in CH4 concentration in emitted gas between the experimental plots, while the concentration of N2 in the gas emitted from the waters grown with Acorus calamus or Nymhaea tetragona was significantly higher than that from the control. The study provides a new method and idea for studying how different aquatic plants affect the gas releasing process in waters.%水体反硝化脱N、温室气体排放以及O2释放过程均是水体生态系统中发生的重要生化反应过程。为了明确不同类型水生植物对这些过程的影响程度，采用自主研发的原位收集水体释放气体装置，于2012年7—8月对滇池草海中自然生长的挺水植物〔菖蒲（ Acorus calamus）〕、浮叶植物〔睡莲（ Nymhaea tetragona）和荷花（ Nelumbo nucifera）〕、漂浮植物〔凤眼莲（ Eichhornia crassipes）〕、沉水植物〔狐尾藻（ Myriophyllum verticillatum）和轮叶黑藻（ Hydrilla verticillata）〕及对照（无植物）区域内释放的N2、CH4、O2、CO2和N2 O的规律进行研究。结果表明，各种水生植物生长区及对照区释放气体主要由N2、CH4和O2组成，其余成分主要是CO2和N2 O。沉水植物通过光合作用明显促进了水域内O2释放过程，进而提高了水体释放气体的速率及各气体成分通量值。而睡莲、荷花和凤眼莲由于叶片覆盖水面的影响，降低了水体藻类的光合能力，造成该区域水体释放气体的速率中值低于对照区，且各气体成分释放通量值也较低。各区域释放气体中CH4浓度无显著差异（ P＞0�05），菖蒲区释放的气体中N2浓度显著高于对照区（ P＜0�05）。