Effect of Water Level Fluctuation on Purification of Iris tectorum

Indoor experiment，using Iris tectorum as a study subject，was done to research purification effect of NH3-N，COD and TP in 20 days at different water levels（10，30，and 50 cm）.Results showed that at 10 cm water depth，purification effect of the Iris tectorum for COD and TP reached 88.4% and 95.4%，which was better than plant group of 30 and 50 cm.Compared to 50 cm water depth condition，TP removal contribution of the Iris tectorum was higher.As water level increased，time of more than 50% pollutants removal contribution of Iris tectorum gradually moved backward and shortens.At 10-30 cm water level，Iris tectorum responded more rapidly to COD and TP，and concentration reduction effect was better than the high water level conditions.Under different water levels，effect of Iris tectorum on soil total nitrogen was not obvious，but effect of Iris tectorum on soil phosphorus fixation was obvious compared with blank group.This experiment aims to provide more choice and better location in selection and planting of aquatic plants in ecological engineering.