不同植物组合人工湿地中磷去向特征研究

人工湿地技术是农业面源污染治理的重要技术措施，而磷的去除是污水治理的主要难点。以亚热带丘陵区为研究区域，以农村养殖废水、生活污水及农田排水混合形成复合污水为治理对象，通过野外小区试验，研究了浮水植物绿狐尾藻（Myriophyllum elatinoides）与挺水植物黄菖蒲（Iris pseudacorus）、水生美人蕉（Canna glauca）、梭鱼草（Pontederia cordata）所构建的浮水植物+不同挺水植物种植模式人工湿地，以探讨不同植物组合模式对人工湿地磷的处理效果与去除途径的影响特征。3—9月结果表明：植物组合湿地对于农村污水中磷素具有显著的处理效果，以无机磷的去除为主。湿地进水总磷（TP）浓度为2.16~5.93 mg·L^-1，各植物组合出水TP浓度为0.34~0.48 mg·L^-1，低于城镇污水排放一级A标准（0.5 mg·L^-1），以绿狐尾藻+梭鱼草湿地的除磷效果最好；不同组合模式人工湿地总磷负荷变化范围为45.50~47.13 g·m^-2·a^-1，绿狐尾藻+梭鱼草组合湿地达47.13 g·m^-2·a^-1，显著高于对照湿地中的39.62 g·m^-2·a^-1；底泥吸附与沉淀是植物组合湿地磷素去除的主要途径，其占湿地除磷总量的72.44%~75.62%。水生植物TP积累量9.65~12.51 g·m^-2·a^-1，占湿地除磷总量的21.00%~26.54%；试验中，植物组合人工湿地比绿狐尾藻湿地底泥吸附占除磷总负荷的比例减少1.71%~4.89%，增加植物吸收比例0.97%~6.28%。较对照湿地底泥吸附占除磷总负荷的比例减少18.11%~21.29%。植物组合有利于延缓底泥吸附饱和时间和提高植物对磷的吸收率。

Characteristics of phosphorus fate in constructed wetlands with different plant combinations

Constructed wetland(CW) technology is an important method of agricultural non-point source pollution treatment, and phosphorus removal is the main source of difficulty in sewage treatment. This study used a subtropical hilly region as the research area and combined rural farming wastewater, domestic sewage, and farmland drainage to form compound sewage as the treatment object. Through field experiments, wetlands were constructed with floating water plants(Myriophyllum elatinoides)alone or M. elatinoides in combination with different emergent aquatic plants(Iris pseudacorus, Canna glauca, or Pontederia cordata), to explore the influence of different plant combinations on the effectiveness of phosphorus treatment and removal in the CWs. The results from March to September showed that the plant combination wetland had a significant effect on phosphorus in rural sewage, and this effect was mainly seen in the removal of inorganic phosphorus. Total phosphorus concentration in wetland inlet water ranged from 2.16~5.93 mg·L^-1, and the outlet water concentration ranged from 0.34~0.48 mg·L^-1 among the different plant combinations; these values were lower than urban sewage discharge standard Grade A(0.5 mg·L^-1). The phosphorus removal effect was greatest in the M. elatinoides + P. cordata wetland. Total phosphorus load of the CWs varied from 45.50~47.13 g·m^-2·a^-1 among the different plant combinations, and the wetland composed of M. elatinoides + P. cordata had a total phosphorus load of 47.13 g·m^-2·a^-1, which was significantly higher than the 39.62 g·m^-2·a^-1 value measured in the control wetland. Sediment adsorption and precipitation were the main phosphorus removal mechanisms in the CWs, accounting for 72.44%~75.62% of total phosphorus removal. Total phosphorus accumulation of aquatic plants ranged from 9.65~12.51 g·m^-2·a^-1, and this accounted for 21.00%~26.54% of total phosphorus removal. In the experiment, compared to the M. elatinoides wetland, the proportion of total phosphorus removed from plant combination CWs through sediment adsorption decreased by 1.71%~4.89%, and phosphorus adsorption by plants increased by 0.97%~6.28%. Compared to the control wetland, the proportion of total phosphorus removed decreased by 18.11%~21.29%. Utilizing plant combinations in CWs can delay the adsorption saturation time of the sediment and increase the phosphorus absorption rate of plants.