| Heavy metal pollution in water is becoming more and more serious,and the problem of heavy metal pollution in rivers and lakes has attracted worldwide attention.When the concentration of heavy metals exceeds a certain range,it will have toxic effects on the whole water environment.It makes the biology’s physiology blocked,development stagnated and even died,and further threatens human health directly or indirectly through the food chain.It is urgent to control the water polluted by heavy metals.With the progress of science and technology,plant restoration method has become a hot research topic in recent years.People use aquatic plants to repair heavy metal pollution water,which is low in cost,simple and convenient to operate,and minimizes the risk to the environment,so as to achieve green governance.To study the removal effect of heavy metals by aquatic plants,this paper used Ceratophyllum demersum,Canna indica L,I.pseudacorus,Pistia stratiotes,Myriollum Spicatum Linscras,Eichhomia crassipes.The removal rate,enrichment and transfer characteristics and physiological indexes of heavy metals in water by aquatic plants were determined.The aquatic plants suitable for river and lake purification were selected and applied to the design of ecological floating bed.Specific conclusions are as follows:(1)Through the hydroponic test of 70 d,the concentrations of five heavy metals Cd,Cr,Pb,Ni and Zn in the aquatic plant group were lower than those in the blank control group.Among the single aquatic plant groups,Eichhornia crassipes has the highest removal efficiency for heavy metals Cd,Pb,Ni and Cr,and Pistia stratiotes has the highest removal efficiency for heavy metal Zn.(2)The highest removal efficiency of heavy metal Cd in the combined aquatic plant group is:B6(Myriophyllum spicatum Linn.+Canna indica L+Eichhornia crassipes).The highest removal efficiency of heavy metal Pb、Cr is B8(Myriophyllum spicatum Linn+I.pseudacorus+Eichhornia crassipes),the removal rate reached 100%.The most efficient removal of heavy metal Ni is B4(Ceratophyllum demersum+I.pseudacorus+Eichhornia crassipes).The most efficient removal of heavy metal Zn is B1(Ceratophyllum demersum+Canna indica L+Pistia stratiotes).(3)Six aquatic plants show different enrichment ability for different heavy metals.The content of heavy metals in low concentration plants is higher,and the plant roots have the strongest ability to enrich heavy metals.Among them,the highest enrichment coefficients of Cd,Pb,Ni,Cr,Zn in the roots were Pistia stratiotes(1967.63),Pistia stratiotes(1035.2),Eichhornia crassipes(1535.6),Eichhornia crassipes(1543.62),Pistia stratiotes(1612.69).On the other hand,Ceratophyllum demersum has the strongest comprehensive enrichment ability for these five heavy metals,and the comprehensive enrichment coefficients for Cd,Pb,Ni,Cr and Zn are 2660.66,2858.43,2706.1,1535.82 and 1820.29 respectively.(4)Six aquatic plants showed different transfer ability to different heavy metals.The four emergent and floating plants have weak transfer ability to Pb,and the transfer coefficient is mostly less than 1.Eichhornia crassipes has the strongest ability to transfer Cd,Cr and Zn,followed by Pistia stratiotes.Eichhornia crassipes has the strongest ability to transfer Ni,followed by Canna indica L,and I.pseudacorus has the worst ability to transfer Ni.(5)Heavy metal stress inhibited the accumulation of biomass and nutrient elements in aquatic plants.The medium concentration was the turning point of stress,and the stress points were lmg/L and 5mg/L.In addition,the stress concentration of heavy metals in roots and leaves of aquatic plants was negatively correlated with the contents of P and K in plants(n=64),and the heavy metals were negatively correlated with nutrient elements(n=224).Figure[53]table[16]reference[97]... |
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