人工湿地处理渗滤液N2O的释放规律及控制

Control and Pattern of N2O Emissions from Constructed Wetlands Treating Landfill Leachate

采用培养试验和现场研究，考察了垃圾填埋场渗滤液经人工湿地系统处理过程中N2O的释放规律．在投加同等质量浓度渗滤液条件下，碱性黏土样Soil 1中N2O释放通量为酸性砂土样Soil 2的近18倍（P〈0．01），与孔隙含水率为46％时相比，投加蒸馏水的土样Soil 1，投加渗滤液的土样Soil 1和投加渗滤液的土样Soil 2在孔隙含水率为70％的条件下，其N2O释放通量平均值分别提高了6．5（P〉0．05），1．8（P〉0．05）和2．2倍（P〈0．05）．选用9种土壤投加渗滤液培养后统计分析表明：N2O释放通量与土壤pH，w（有机质）和碳氮比[（w（C）／w（N）]呈显著正相关，而与土壤中w（砂粒）呈显著负相关，3种湿地处理渗滤液后，夹竹桃（Nerium indicum Mill）湿地中N2O释放通量最高，其年均值（以MO2-N计）为（298±234）μg／（m^2·）（P〈0．05），分别比高羊茅（Festuca arundinacea Schreb）和狗牙根（Cynodon daetylon）湿地N2O年均释放量高出0．5（P〉0．05）和6．6倍（P〈0．05）．在关注去除污水中氮元素的同时，也要重视由此引发的二次污染问题，建议人工湿地系统采用酸性砂土，种植的植物采用阳光穿透性强的针叶类植物，以减少处理污水过程中N2O的释放．

N2O emissions from constructed wetlands being used to treat landfill leachate were investigated through laboratory incubation and field experiments. After adding the same amount of leachate, N2O emissions from alkaline clay soil （named Soil 1） were approximately 17-fold more than acidic sandy soil （named Soil 2）. Compared with soil moisture content at water-filled pore space （WFPS） of 46 %, N2O fluxes were elevated by 6.5 times, 1.8 times, and 2.2 times for distilled water with added Soil 1 （ P 〉 0.05）, leachate with added Soil 1 （ P 〉 0.05）, and leachate with added Soil 2 （P 〈 0.05） at 70% WFPS, respectively. Among the physiochemical characteristics of nine soil samples, statistical analysis showed that soil pH, organic matter content, and the ratio of C to N were significantly positively correlated with N2O fluxes, while sandy content was negatively correlated with N2O fluxes. As for the site investigation, the Nerium indicum Mill constructed wetland exhibited the strongest N2O emissions among the three selected plants, with an annual average N2O flux of （298 ±234）μg/（m^2·h） （P〈0.05）, which was nearly 0.5 times and 6.6 times more than those of the Festuca arundinacea Schreb （ P 〉 0.05） and the Cynodon dactylon constructed wetlands （P 〈 0.05）, respectively. Thus, secondary pollution to the atmospheric environment must be considered when constructed wetland is used to remove nitrogenous pollutants from treated waste water. Constructed wetlands composed with acidic sandy soil and planted with conifer plants are beneficial to decreasing N2O emission when they are used to treat waste water.