湿地植物供碳功能与优化

尾水湿地氮的反硝化去除往往受限于碳缺乏。综述了湿地植物供碳促反硝化的主要途径与影响因素,构建了华东地区典型冷、暖季型湿地植物供碳的一般性季节动态模式,以期为发挥湿地植物稳定高效供碳功能、缓解尾水湿地碳缺乏问题提供解决思路。湿地植物的主要供碳途径包括根系分泌、地下有机质分解和地上有机质分解(淋溶)等,湿地植物的供碳动态是物种和环境因子综合影响的结果,存在极大的时空异质性。湿地植物具有很强的供碳促反硝化潜力,地上最大生物量为5 kg/m~2的芦苇全年脱氮潜力可高达0.57 kg N/m~2。在构建的湿地植物生物质积累量和供碳量的一般性模式中,冷、暖季型湿地植物无论是生物质积累量(总生物量)和还是供碳量(分解部分+根系分泌物)均存在显著的季节性差异,以及季节间的互补特征。因此,冷、暖季型湿地植物间进行合理的配置,是发挥湿地植物供碳功能且避免生物质分解引起二次污染的可行性措施。今后在湿地植物供碳定量化研究方法、多种供碳途径的定量化监测、供碳功能调控策略,以及稳定高效供碳促反硝化人工湿地构建等方向需做进一步研究。

The carbon source function of constructed wetland macrophytes and its improvement strategy

Constructed Wetlands (CWs) have been widely used for the advanced treatment of the secondary wastewater from Waste Water Treatment Plant (WWTP). However, the pollutant, especially nitrogen, removal efficiency is greatly limited by the lack of carbon sources in the secondary effluent treatment of CWs because most Biochemical Oxygen Demand (BOD) matter has been removed in WWTP. The main pathway of carbon source supplied from CW macrophytes and its main influencing factors were reviewed in this paper. Furthermore, the universal seasonal dynamics and modes of organic matter supply quantities were established for CW macrophytes in East China. The main objective was to develop a novel strategy to stabilize the carbon-supply function of CW macrophytes for the improvement of pollutant removal efficiency and avoidance of secondary pollution in the decomposition process of macrophyte litter by the configuration of warm-season cold-season macrophyte species. The main pathway of carbon source supplied from CW macrophytes included root exudates, decomposition of under-ground biomass, and the decomposition (and leaching) of above-ground biomass. The CW macrophytes have a relatively high carbon supply for denitrification, which is closely correlated with macrophyte species and numerous environmental factors, and thus varies substantially in both time and space. As an example, Phragmites australis with a maximum above-ground biomass of 5.0 kg/m² potentially supports a nitrate removal rate of 0.57 kg N/m² in one year, which is much larger than the values estimated by the previous studies because most previous studies only accounted for the above-ground biomass and ignored other carbon-supply paths of CW macrophytes. Because of the seasonal variation of CW macrophyte carbon-supply function, the universal seasonal models of Biomass Accumulation (BA, the un-decomposed CW macrophyte biomass) and Organic Matter Supplied Quantity (OMSQ, the decomposed CW macrophyte biomass plus the root exudates) were established for representative warm-season and cold-season macrophytes species in East China, respectively. Warm-season and cold-season macrophytes showed significant seasonal complementarity characteristics in both BA and OMSQ. Therefore, the proper configuration of warm-season and cold-season macrophytes in a CW system can greatly stabilize the carbon-supply function of CW macrophytes and thus avoid the secondary pollution by the simultaneous decomposition of most macrophytes litter. The above-ground biomass harvest and return to CW after pretreatment can further improve the artificial management of the carbon-supply function and thus increase the denitrification stimulation function of CW macrophytes. In the future, the related research should be focused on (1) development of the quantitative analysis methodology of OMSQ supplied from CW macrophytes, (2) monitoring the dynamics of the OMSQ quantity and its possible regulation strategies and, (3) design of CW with the ability of supplying stable and high quantity carbon sources from itself as planted macrophytes for improving pollutant efficiency.