The Comparison Of Physio-ecological Characteristics And Nitrogen/Phosphorus Removal Capacity Of Reed And Gaintreed Under Two Types Of Constructed Wetlands

Over the last two decades,constructed wetland systems have been studied and used widely because they perform good function in treatment of wastewater.Plants were the important components in constructed wetlands and played an important role in constructed wetlands for the treatments of wastewater.There were many studies on the principle of plants to treat wastewater,and many researches compared different plants physio-ecological characteristics under same wetlands condition.But there are few papers referring to the effects of plants pbysio-ecological characteristics under different types of constructed wetlands.It is necessary to study the influence on plant induced by different types of constructed wetlands in order to select appropriate plant species.In order to assess the growth situation of plants in the different types of constructed wetlands,the differences of physio-ecological characteristics of two species of plants under constructed surface flow wetland(SFW)and constructed subsurface flow wetland(SSFW) were studied.Two species of plants(Phragmites communis and Arundo donax)were planted in two types of constructed wetlands The net photosynthetic rate(P_n),stomatal conductance(g_s),transpiration rate(T_r)under a series of photosynthetically active radiation(PAR) and CO₂ concentration were measured.The chlorophyll content and water potential of leaf were measured,too.At the same time,the plant growth indices(fresh weight,dry weight,stem height,root length)were measured to estimate the plant growth situation under two types of constructed wetlands.The results showed that no significant differences were found on leaf water potential for two species of plants under the two types of wetlands.However,there were significant differences of the characteristics indices(including relative growth rate, chlorophyll concentration,net photosynthesis rate,transpiration rate and the stomatal conductance)of giantreed under SFW and SSFW. The root growth and leaf water potential indicated that water was not the limiting factor that affects plant physiological characteristics.The positive correlation between chlorophyll concentration and photosynthesis showed that chlorophyll was the most important factor.From the experiment of Nitrogen/Phosphorus Removal,it was found that the Nitrogen/Phosphorus removal efficiency of reed were 2 and 3 times higher than giantreed respectively.Due to the difference of biomass aroused by different wetland types,the accumulation of Nitrogen/Phosphorus by giantreed were 3.5 times and 3.8 times of reed in the SSFW,whereas giantreed owning to the poor growth had the same accumulation of Nitrogen/Phosphorus as reed in the SFW.The result revealed that 80-85%of TN and 50-70%of TP in plant were untaken by aboveground biomass,and which implied that plant uptake was an important pathway for nutrient removal in the constructed wetland for treating eutrophic water.The results showed that the reed was adaptable to cultivate in both kinds of wetlands while the giantreed was more suitable to grow in SFW.