| Lake eutrophication and heavy metal pollution are the major environmental problems in the world today. The technology exists shortcomings in tradition of large investment, complex equipment and so on. It must find a new method that is simple and effective, economical and practical. In recent years, the subject related to environmental governance has been got into the phytoremediation boom. The removal of heavy metal and nitrogen and phosphorus of water by aquatic plants has a very good effect.This paper first had surveyed sedimentnutrition status of the four typical lakes at Wuhan City, then studied the effect of removing nitrogen and phosphorus by the macrophyte Phragmites australis and submerged plant Potamogeton crispus and removing heavy metals by P. crispus., The work includes studying the effects of on pH, DO, TP, TN, ammonia nitrogen and nitrate nitrogen content, the effect on Cd, Cr, Cu, Mn, Ni, Zn content of overlying water by P. crispus, and distribution of heavy metal in plants and sediments. We also explored the mechanism on absorption and release of heavy metal by roots and stems and leaves of P. crispus. The main conclusions are as follows:1. Lake Donghu, Lake Liangzihu, Lake Yuehu, and Lake Tangxunhu showed the different characteristics of particle size distribution, the average particle size from order of Lake Liangzihu> Lake Tangxunhu> Lake Donghu> Lake Yuehu;Lake Donghu, Lake Liangzihu, Lake Yuehu, and Lake Tangxunhu had different phosphorus forms in different particle sizes and each kind of lake had its own unique distribution characteristics of phosphorus content;In addition to phosphorus forms such as Fe-P in the sediment of Lake Yuehu and Ca2-P in the sediment of Lake Liangzihu, a linear relationship between the different forms of phosphorus and particle size was not determined. And comprehensively, not all the forms of phosphorus had highest content in the smallest size.2. Different species of aquatic plant had different effects on the enclosure environment change, P. australis had the ability of consumping dissolved oxygen with decreased pH trend, and P. crispus increased DO and pH in the overlying water;In the enclosure, the removal on TP, TN, ammonia nitrogen, nitrate nitrogen by the aquatic plants compared with blank had higher rate, which provides a strong basis for the treatment of eutrophic water;Different aquatic plants had different nutrient removal rates, the removal rates of TP, TN and ammonia nitrogen by P. australis were higher than that by P. crispus, and nitrate removal rate by P. crispus was higher than that by P. australis;On a condition of P. crispus, the removal effect of heavy metals in water was better than that of no P. crispus.3. P. crispus had different absorption capacity of heavy metals, it has a super enrichment of Cd, Mn, Ni, especially Mn. P. crispus was a kind of manganese-liking aquatic plant;Heavy metal accumulations in different parts of P. crispus were not same. P. crispus leaves had very strong enrichment capability of Cd. New leaves of P. crispus had higher Cr, Cu, Zn, Ni, Mn content than roots, stems and old leaves.4. Root or leaf of P. crispus had the ability of absorption and release of zinc;In root environment of4.5mg/L Zn, the amount of total zinc released by P. crispus leaves were higher than that in1.5mg/L. As the environmental Zn reaches6.5mg/L, the amount of total zinc released by P. crispus leaves started lower than as1.5mg/L and4.5mg/L Zn, but after ld culturing, the amount as6.5mg/L Zn in root environment was significantly more than that as other two concentrations;With the concentration of Zn in the leaf environment increased from1.5mg/L to4.5mg/L (there were no Zn in the root environmental on initial condition), the zinc ammount released by root of P. crispu also increased gradually. As6.5mg/L Zn in leaf environment, Zn release rate of P. crispus root was lower than the other two concentrations after3rd d. |
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