Effects Of UVB Enhanced Intensity On Enzyme Activity Of Substrate And Plants In Constructed Wetland

At present, global ozone layer was destructed due to reaching the earth’s surface enhanced UV-B, which influenced terrestrial and aquatic ecosystem. Wetland system has some common characteristics between terrestrial and aquatic ecosystem. Constructed wetland ecosystem is treatment system, which was used to purifying wastewater based on interaction between substrate, microorganism and plants. Constructed wetland was widely used because of its low cost operation and management. The effect of the enhanced UV-B intensity on plants and microbial growth was researched in this thesis. The main results were shown as the following.(1) The bacteria, fungi and actinomycetes in surface and vertical flow constructed wetland were inhibited by enhanced UV-B. The total number of bacteria by enhanced UV-B strength was more sensitive to fungi and actinomycetes. Catalase and sucrase in the substrates was decreased in the surface flow and vertical flow constructed wetland by the enhanced UV-B radiation. Average catalase in furface flow constructed wetland were decreased by23.3%and51.3%by enhanced UV-B radiation at10%and20%, respectively, similarly, its decreased sucrase enzyme by10.8%and17.7%, respectively. However, urease and cellulase increased by62.9%and95.2%, and19.1%and38.8%in the surface flow constructed wetland under enhanced radiation at UV-B10%and20%, respectively. Average catalase and sucrase in vertical flow constructed wetland decreased by14.9%and20.2%by enhance the radiation at UV-B10%, respectively. However, urease and cellulase increased by53.4%and27.4%in the vertical flow constructed wetland under enhanced radiation at UV-B10%, respectively.(2) The chlorophyll content of wetland plants by enhanced UV-B radiation were significantly decreased in surface and vertical flow constructed wetlands, and changed with different plants. In spring, the content of chlorophyll of Canna, cattail and reed in surface flow constructed wetland were decreased by16%and31.7%,19.4%and44.6%, and22.5%and51%by enhanced UV-B radiation of10%and20%, respectively. In spring, the content of chlorophyll of Canna, cattail and reed in vertical flow constructed wetland decreased by21.6%,22.6%, and17.1%by enhanced UV-B radiation of10%, respectively.(3) The MDA content of wetland plant was influenced by enhanced UV-B radiation. In spring, the content of MDA of reed, cattail, Canna in surface flow constructed wetland increased by31.7%and78.7%,11%and25.7%, and26.3%and42.6%under enhanced UV-B radiation at10%and20%level, respectively. In spring, the content of MDA of reed, cattail, Canna in vertical flow constructed wetland increased by47.2%,9.8%, and45.1%under enhanced UV-B radiation at10% level, respectively.(4) Catalase, peroxidase and superoxide dismutase activity increased under enhanced UV-B radiation. Under enhanced UV-B radiation at10%and20%level, catalase activity of reed, cattail, Canna in Spring in surface flow constructed wetland increased by7.1%and14%,26.5%and37%, and7.1%and20.9%, respectively; its increased peroxidase activity by11.5%and23.1%,20%and50%, and9.1%and27.3%, respectively. Similarly, its increased superoxide activity by6.7%and20.9%,4.7%and32.7%, and16.8%and37.8%, respectively. In spring, catalase activity of reed, cattail, Canna in vertical flow constructed wetland increased by12.6%,19.5%, and29.9%under enhanced UV-B radiation at10%level, respectively; its increased peroxidase activity by33.3%,37.5%, and21.1%, respectively; its increased superoxide activity by13.1%,63.8%, and18%, respectively.(5) The nitrogen and phosphorus uptake by wetland plants in surface and vertical flow constructed wetland was inhibited under enhanced of UV-B, which influenced by type of constructed wetlands. In the spring, nitrogen uptake by Canna, cattail, reed in surface flow constructed wetland under natural light conditon was1.65times,2.21times,1.53times as much as under enhanced UV-B10%, respectively; similarly, its absorbed nitrogen natural light conditon was4.12times^4.22times and9.46times as much as under enhanced UV-B20%, respectively; phosphorus uptake was2.78times,2.73times,9.98times as much as under enhanced UV-B10%, respectively; similarly, its absorbed phosphorus natural light conditon was10.39times、9.15times and12.52times as much as under enhanced UV-B20%, respectively. nitrogen uptake by Canna, cattail, reed in vertical flow constructed wetland under natural light conditon was3.27times,1.38times,1.27times as much as under enhanced UV-B10%; phosphorus uptake was2.3times,1.65times,2.07times as under enhanced UV-B10%.