根表铁膜在人工湿地磷去除中的作用及基质的影响

本研究构建了基质铁含量分别为10.68％、23.52％、44.20％和pH分别为7.0、7.3、7.9的3个水平潜流人工湿地实验系统,在对污水进行5个月处理后,分析了各系统不同区域植物根表铁膜形成量及植物、基质、根表铁膜中磷的分配量,以期阐明植物根表铁膜在人工湿地磷去除中的作用及基质的影响.结果表明,经过5个月的污水处理,3个系统植物根表都出现了明显的铁膜,形成量在15 ～35 g·kg-1(以根干重计)之间,铁膜的形成量受到基质铁含量和pH共同影响,基质铁含量的增加,同时pH不增加或增加幅度较小时,铁膜形成量会相应增加;但若含铁基质材料碱性较强时,基质铁含量增加导致pH大幅增加时,根表铁膜形成量则不随基质铁含量增加而增加3个系统铁膜中磷含量都在20g·kg-1(以根干重计)左右,相差不大,铁膜磷含量受基质对磷的竞争和植物吸收转移影响.各系统中,铁膜单位磷含量远高于植物和基质,并且分配在铁膜中的磷总量既高于植物地上部分也高于地下部分,甚至与植物地上和地下部分总和接近,表明铁膜在人工湿地中是一个重要的磷吸附截留部位,对人工湿地磷的去除具有重要作用.

The role of root iron plaque in phosphorus removal of constructed wetland and the effect of medium on iron plaque

In order to investigate the role of root iron plaque in phosphorus removal and the effect of medium iron content and pH on iron plaque, three laboratory-scale constructed wetlands with horizontal sub-surface flow were built in this study. The media used in these wetlands had different iron contents and pH. The root iron plaque of Typha latifolia and distribution of phosphorus in different parts of each wetland were measured after five-month operation.The results showed that a lot of iron plaque formed on the surface of plant root in each wetland. The Fe contents of these iron plaque were about 15~35 g·kg^-1 dry root weight. The amount of iron plaque was affected by both Fe contents and pH of medium in the wetlands. When the medium Fe contents increased without significant pH changes, the amount of iron plaque increased with the increase of medium Fe contents. However, the increase of medium Fe contents resulted in its pH increasing greatly, while the amount of iron plaque did not increase with the increase of medium Fe contents. The concentration of phosphorus in iron plaque of each wetland was about 20 g·kg^-1 dry root weight, and no significant difference was observed among three wetlands. The phosphorus contents of iron plaque were affected by both the competition with the medium to adsorb phosphorus of wastewater and the transference of phosphorus in iron plaque into plant biomass. The iron plaque had strong capacity in adsorbing phosphorus so that the phosphorus concentration in it was far higher than in biomass and medium. The amount of phosphorus in root iron plaque was also higher than the ones in above- and belowground plant biomass in all three wetlands. Moreover, it was even near to the amount of phosphorus in the whole plant biomass. These indicated that the root iron plaque was an important part for phosphorus retention in the constructed wetland.