Study On Distribution Of Aquatic Macrophytes And Its Purification Effects On Eutrophicated Water Body Of Hongfeng Reservoir

Hongfeng reservoir is the most important water resource of Guiyang.But the water quality of Hongfeng reservoir had become deteriorated in recent years.There was low transparence,turbid and fishy water in the reservoir and it had been an eutrophicated reservoir.That could cause some serious problems:polluted water could not be used as the drinking water and daily used water for denizen,and it also destroyed the development of economy of Guiyang.On the basis of investigating the resource of aquatic macrophytes in Hongfeng reservoir,the paper selected some aquatic macrophytes to study their purification effect of nutrition and organism in the water.Experiments were carried out in indoor and outdoor natural condition by the water of Hongfeng reservoir.Experiment results were summarized as follows:1.Investigation result indicated that there are rich resources of aquatic macrophytes in Hongfeng reservoir basin.45 species of aquatic macrophytes,belonging to 22 families 32 genus were found.Among them, Hydrilla verticillata,Myriophyllum spicatum,Ceratophyllum demersum, Potamogeton malaianus,Sagittaria sagittifolia,Vallisneria natans, Nuphar pumilum,Polygonum hydropiper,Alternanthera philoxeroides and Azolla imbricata were common species.2.Growth situation of Hydrilla verticillata,Myriophyllum erticillatum, Cyperus alternifolius,Acrous calamus,Ipomoea aquatica and Canna indica show that aquatic macrophytes could grew well at prophase of indoor experiment.The increase rate of The biomass of Ipomoea aquatica is the most fast,Canna indica is slower than Ipomoea aquatica, Myriophyllum verticillatum is the slowest.Cyperus alternifolius,Acrous calamus and Hydrilla verticillata have no obvious difference.Because of the lack of nutrition,some leaves of Ipomoea aquatica,Canna indica and Cyperus alternifolius became withered at the end of experiment.But Hydrilla verticillatajvlyriophyllum verticillatum and Acrous calamus were not.On the contrary,there were few withered leaves because of rich nutrition in the water at the outdoor experiment.The results of preliminary experiment shows that purifying eutrophic water body of Hongfeng reservoir with aquatic macrophytes is viable and effective.3.It could be seen from the results that the aquatic macrophytes selected in this test decrease the concentration of total nitrogen(TN),total phosphorus(TP),chemical oxygen demand(COD),NH₃-N and biomass of phytoplankton in the water.The removal rates of TN,TP,COD,and NH₃-N with Myriophyllum erticillatum,Hydrilla verticillata,Cyperus alternifolius,Acrous alamus,Ipomoea aquatica and Canna indica was 49.7～59.9%,39.9～57.9%,43.9～56.4%and 38.0～60.2%,respectively. Purification effect between different aquatic macrophytes had no significant differences.The correlation between the biomass increase rate and the removal rate is not obvious.The rate may relate to absorption characteristic and micro-ecosystem activity of root.4.Result of polycyclic aromatic hydrocarbons(PAHs) experiment indicated these six kinds of aquatic macrophytes had good abilities to get rid of naphthalene and phenanthrene.During the 40 days experimental period,removal rate of naphthalene and phenanthrene was 44.07～73.49%,54.24～77.19%,respectively.Removal rate of fluorene,anthrace-ne and pyrene was 29.45～45.11%,27.74～47.64%,29.84～45.32%, respectively.Acrous calamus had the best effect for naphthalene, phenanthrene and anthracene.Cyperus alternifolius was worse than other aquatic macrophytes.Myriophyllum verticillatum and Hydrilla verticillata are better choices to adsorb PAHs.5.Considering various factor,Myriophyllum verticillatum,Hydrilla verticillata and Acrous calamus had both good and stable purifying effect.They have potential utilization value.Ipomoea aquatica can remove the TN and TP in the water body quickly.The advantage will be exhibited if harvest or replace them in time.Purifying effect of Cyperus alternifolius and Canna indica inferior to others in general.However,an increasing number of researchers play an interested in them because of their ornamental and environmental value.Therefore,we could try to use them in ecological restoration engineering of Hongfeng reservoir.