Screening Duckweed(Lemnaceae)Species for Efficient Removal of Water-Body''s Nitrogen in the Tai Lake Region and Preliminary Study on Nitrogen Removal Mechanism
太湖地区高效除氮浮萍品种的筛选及其除氮机理的初步研究

Non-point agricultural sources are the major cause of water eutrophication in Tai Lake. Phyto-remediation techniques are playing an increasingly important role in non-point pollution research. This study compared nitrogen removal efficiency among different duckweed species growing in paddy field drainage water with low nitrogen concentrations in the Tai Lake region. Nitrogen removal efficiency declined in the order of Spirodela polyrrhiza > Spirodela oligorrhiza, Lemna perpusilla > Lemna minor, total nitrogen removal efficiency among the duckweed species in this study ranged from 57.3% to 85.2%. The removal efficiency in 15 days of HZ1 was highest (85.2%) while WX3 was 57.3%. The biomass production rates of WX3 were higher than that of HZ1, the doubling time of fresh and dry weights were 5.20 days and 4.73 days for WX3 but 7.96 days and 7.82 days for HZ1, respectively. The nitrogen contents were 4.9% and 5.7% in HZ1 and WX3, respectively, however the nitrogen removal efficiency of HZ1 was significantly higher than that of WX3. It suggests that nitrogen removal from water is due to microbial or chemical processes rather than bioaccumulation.