Studies On Screening、Root Inducing And Adaptive Mechanism Of Woody Plants With Subsurface Flow Constructed Wetlands

Plants play an important part of constructed wetlands system. In order to increases the cold hardiness of subtropical constructed wetlands plant species and biodiversity, common woody plant in subtropical area of this study was tested in constructed wetlands sewage treatment system.24woody plant was screened and evaluated; root induction was made through orthogonal design; and also woody plant adaptive mechanism was investigated. The main findings are as follows:(1) To establish a scientific system for screening wetland plants and evaluating their purification potential, cluster analysis was conducted on common plant indexes, combined with adverse circumstance enzyme and matrix enzyme activities from17species of wetland plants, The17plants differed in their root quantities, root length, vigor, leaf peroxide enzyme activity, biomass quantity, average concentration of nitrogen and phosphorus, and ability to accumulate nitrogen and phosphorus. Also, the matrix urease activities and phosphoric acid enzyme activities from the17plants’ root systems were different. The17wetland plants were clustered into3groups according to the synthetic purification potential evaluation system. The1st group, including Canna indica, Phragmites australis, Cyperus alternifolius, Scirpus validus, Thalia dealbata, Lythrum salicaria, and Variegated canna had strong purification potential. The2nd group, which included Acorus calamus, Arundo donax, Typha angustifolia, and Pontederia cordata, had medium purification ability; and the3rd group which included Colocasia antiquorum Schott, Iris pseudoacorus, Juncus effuses, Zephyranthes candida, Alisma plantago-aquatica, and Iris ensata Thunb. was weak.(2) In order to make woody plants more widely used in subsurface flow constructed wetland, the experiment was investigated with single factor tests and orthogonal design according to4factors (root cutting effect, substrate forms, hormone density, aeration time)and5levels orthogonal table with4woody plants(Nerium oleander, Hibiscus syriacus, Gardenia jasminoides, Ligustrum lucidum). The results indicated that the best response level have same differences between single factor tests and orthogonal design. The most appropriate root cutting for Nerium oleander was1/4, Hibiscus syriacus and Gardenia jasminoides were1/8, Ligustrum lucidum was1/2.The most appropriate substrate for Nerium oleander was the peaty soil, Hibiscus syriacus and Gardenia jasminoides were the vermiculite, Ligustrum lucidum was the perlite. The most appropriate rooting of hormone density for Nerium oleander and Hibiscus syriacus were1000mg/kg, high hormone density was not appropriate for Gardenia jasminoides and Ligustrum lucidum. The most appropriate aeration time for Nerium oleander was8h/d, Hibiscus syriacus and Ligustrum lucidum were16h/d, and Gardenia jasminoides was12h/d.(3)4woody plants were used in the SFCW in this study. Through the analysis of the net photosynthetic rate, stomatal conductance, the concentration of intercellular CO2, transpiration rate and other indicators, we determine whether or not these plants adapt to the undercurrent constructed wetlands. In order to reveal the adaptation mechanism of woody plant constructed wetlands, the following researches were done. We elaborated the changes of root system changes by ntuitive and microscopic changes through the root system frozen section woody plants induced by the root frozen section of the root and microscopic changes of woody plants induced by the root, detected the content of chlorophyll content and MDA, the accumulation of plant nitrogen and phosphorus, the activity of urease and phosphatase in plant roots systems, measured the removal rate of TN、TP、CODCr、NH4+-N in constructed wetlands. The results showed that:view from the net photosynthetic rate and stomatal conductance of woody plant, diurnal variation of net photosynthetic rate of Oleander, Gardenia, Ligustrum lucidum showing as the double peak type, and Hibiscus is unimodal type; diurnal variation rule of plant intercellular CO2concentration is basically similar, it reached the minimum value in14:00and then increased; different plant transpiration rate reached the peak at noon, the lowest in the evening; photosynthetic active radiation effects on transpiration rate of Hibiscus has a stronger effect than Oleander and Gardenia, and weaker correlation of Ligustrum lucidum. View from ligneous plants root Frozen section,4woody plant can adapt to the SFCW. Experimental results indicated that Nitrogen phosphorus accumulation are stronger and mechanism of enzyme activity is higher, which illustrated that these four species of ligneous plants has good prospects for decontamination applications. Woody plant water quality of SFCW shows that the average TN removal efficiency is40.2%; the removal rate of TP reached80.8%; the removal rate of CODCr was15.4%; the average NH4+-N removal rate is61.8%.