Study On The Effect Of Five Aquatic Plants On The Purification Of Eutrophic Water

Eutrophication of water is one of the most recognized water pollution problems in the 21 st century.Therefore,how to repair eutrophic water bodies and restore the ecological environment has become the focus of global environmental issues.At present,there are mainly physical,chemical,microbial and other restoration methods for eutrophic water,but all of them have more or less shortcomings.Compared with other methods,phytoremediation technology has the advantages of less investment,better purification effect and lower operating cost,and is being widely applied to the treatment of eutrophic water.In recent years,many scholars have used a variety of aquatic plants to repair the eutrophic water body,but most of the experiments only study the purification effect of aquatic plants,and the research on the relationship between aquatic plant root system and eutrophic water body is relatively few.This test by static hydroponic experiments of five kinds of common aquatic plants(iris,willow,crassipes,water lily,arrowhead),respectively study under the condition of mild,moderate,severe eutrophication's ability to remove nutrients and root length,root activity and catalase in different concentration of the root nutrition conditions change.In order to provide a theoretical basis for the selection of aquatic plants for the restoration of eutrophic water bodies.The research results show that:(1)all the five aquatic plants selected in the experiment have better purification effect on nitrogen elements in water,with significant difference from the control group(P<0.05).Under different eutrophication conditions,the water hyacinth and chelidonia have the best purification effect,and the removal rate of other aquatic plants is from large to small,including ciguatera edodes,iris and water lily.With the increase of eutrophication degree,the removal rate of the same aquatic plant first increases and then decreases,indicating that nitrogen at the appropriate concentration can promote the purification effect of aquatic plant,while too high concentration will inhibit the purification effect.In the three eutrophicated water bodies with different degrees,the phosphorus removal effect of the five aquatic plants is better and increased with the increase of nutrient concentration.The removal ability is from strong to weak,such as fleeceflower,water lily,ciguatera,iris and water lily.Among the plants with the best COD removal effect in eutrophicated water,the COD concentration in water decreased from 43.143 ? 113.09mg/L to 12.92 ? 18.11mg/L,and the removal rate is 63.7% ? 83.99%,which is significantly different from that in the plant treatment group(P<0.05).The COD removal rate of other plants is from large to small,such as salicydes edodes,iris,water lily and water lily.(2)with the progress of the experiment,the root length of the five aquatic plants keep growing.Under the three nutrient-rich conditions,the root growth rate of all the five aquatic plants is the highest,followed by fleur-de-lis,iris,water lily and salicydes edodes.Under the condition of the same rich nutrition,into the water plant root activity after all to change,and all is the largest with crassipes,respectively under the low level of eutrophication of 347.69 mu g/g FW * hr,moderate eutrophication level 415.64 mu g/g FW * hr,high eutrophication level 235.65 mu g/g FW * hr,secondly,arrowhead,fresh mushroom willow times,minimum irises and water lily,showed that purification ability is the root,crassipes > arrowhead,fresh mushroom kind vegetables > iris > water lily.The catalase activity is measured at the beginning and the end of the experiment.Under the condition of low eutrophication,the enzyme activity of aquatic plants in the later stage of the experiment is decreased in the early stage.Under the conditions of moderate and severe eutrophication,the enzyme activity of aquatic plants is higher at the later stage than at the early stage of the experiment,and the enzyme activity of water hyacinth is the highest,followed by chelidonium,followed by water lily,and ciguatera and irises are the lowest.The results showed that the water hyacinth is the most tolerant to high nutrient load.To sum up,the absorption and purification effect of nitrogen,phosphorus and COD in eutrophicated water bodies of chelidonium and water hyacinth are better than those of the other three plants,which can better absorb and purify nutrients and repair water ecological environment.