The Tolerance And Phytoremediation Potential Of Three Kinds Of Aquatic Plants On Lead Tailings Liquid

This thesis takes Canna glauca,Nuphar pumilum,and Hydrocotylevulgaris as experimental materials and research objects.The leachate of plumbum tailings in the mining area of Dexing plumbum tailings was used as the test medium.This study was investigated in single and compound potted plants,which focuses on the growth index,physiological index,concentration and transfer coefficient of metal ion in these three kinds of aquatic plants were influenced by the stress of plumbum tailings leachate?PbL?.Meanwhile,the restoration of water quality in the leachate of plumbum tailings was discussed in this paper.It provides a theoretical foundation for the research of phytoremediation technology in water pollution caused by heavy metals like plumbum.The major findings are as follows:?1?The growth index,enrichment and transfer coefficient of metal ion in Canna glauca under the stress of different concentrations of plumbum tailings leachate?Pb L?were studied in this thesis.The results showed that the growth index of Canna glauca's seedlings rises first and descends later with the increasing concentration of Pb L.The plant height,root length,number ofleaves,overground part of dry weights of stem and tolerance index will reach its maximum level under the stress of 25%Pb L.However,the growth index of Canna glauca will reach its minimum level under the stress of 100%PbL.The plant height,number of root,overground and underground part of dry weights of stem have significant difference in contrast to the control,which shows its value at 85.67%,75.1%,75.38%and 50%of the control group respectively.According to the research results of heavy metal enrichment under the stress of 100%PbL,the amount of enrichment of Pb²⁺in overground and underground parts of Canna glauca will reach its maximum,which displays its value at 110.58?g/g and241.92?g/grespectively.The enrichment amount of Cu²⁺,Zn²⁺and Cd²⁺in all treatment groups were higher than those in the control groups.The content of Ca²⁺shows a decreasing trend with the increasing concentration of Pb L.The transfer coefficient of Canna glauca was lower than that of the control groups,which indicates that most of the Pb²⁺was enriched in the underground part of Canna glauca.?2?The physiological index of Canna glauca under the stress of different concentrations of plumbum tailings leachate?PbL?was studied in this thesis.The results showed that with the increasing concentration of PbL,the content of chlorophyll in the seedlings of Canna glauca displays a downward trend.However,with the increasing concentration of PbL,the relative electrical conductivity and content of MDA in the overground and underground parts of the Canna glaucadisplaysan increasing trend.Meanwhile,the relative electrical conductivity of the overground and underground parts of Canna glauca were 123.26%and 110.23%of the CK respectively under the treatment of 100%PbL,while the content of MDA was 144.19%and 149.02%of the control groups respectively.Therefore,the content accumulation of MDA in Canna glauca under the stress of high concentrations of PbL.The content of Pro in the overground parts of Canna glauca increased suddenly under the treatment of 100%PbL,but changes in low concentration of the treatment of PbL was not obvious.The activity of SOD in the overground parts of Canna glauca showed a tendency of rising first and then decreasing,while the activity of POD in the overground and underground parts of Canna glauca showed a tendency of rising first and then decreasing.Low concentration of PbL has a certain role in promoting the activity of SOD and POD,while high concentration of Pb L is quite harmful to Canna glauca and the resistance to the stress of Pb²⁺begins to decline.With the increasing concentration of PbL,the content of AsA and GHS in the overground parts of Canna glauca's seedlings showed an upward trend,while that in the underground part displayed a trend of rising first and then decreasing.High concentrations of Pb L will injure the roots in the seedlings of Canna glauca at first,which leads to decreasing in the content of AsA and GHS in the underground part.The content of GSH in the Canna glauca's leaves was much greater than those in the roots,which indicates that Canna glauca's leaves played a significant role in resisting the damage of reactive oxygen caused by Pb²⁺.The test results showed that Canna glauca has certain tolerance under the stress of PbL,which establishes the foundation for the further exploration in the remediation function of Canna glauca in water pollution caused by heavy metals like plumbum.?3?A number of growth indexes showed a downward trend in the combined cultivation of Canna glauca,Nuphar pumilum,and Hydrocotyle vulgaris compared with the control groups.The plant height,number of root,fresh weight,and dry weight of Canna glauca declined significantly when they are in the mixed planting,which was quite different from the control groups?P<0.05?.In the mixed cultivation of Canna glauca and Hydrocotyle vulgaris,the plant height,number of leaves,number of roots and fresh weight of the overground part increased slightly compared with the control groups.Under the condition of mixed planting,the growth indexes,fresh weight,dry weight,and tolerance index of Nuphar pumilum has a tendency of decreasing compared with that of single cultivation.Therefore,Nuphar pumilum was not suitable for mixed cultivation.However,In the mixed planting of Nuphar pumilum and Hydrocotyle vulgaris,the number of leaves and root,root length,fresh weight of the underground part and tolerance index of Hydrocotyle vulgaris has a tendency of increasing compared with the control groups.All indexes showed a downward trend in the other conditions of mixed planting,which shows that Nuphar pumilum can promote the growth of Hydrocotyle vulgaris.The test results indicated that Nuphar pumilum is suitable for block planting,while Canna glauca and Hydrocotyle vulgaris can be mixed planting,and collocation of plants must be taken into account when they are mixed.?4?The ability to repair the quality of plumbum tailings leachate?PbL?in the single and compound planting of Canna glauca,Nuphar pumilum,and Hydrocotyle vulgaris was studied in this thesis.The results showed that the value of pH in each treatment group was higher than the control groups,and the pH values of PPbL,TPb L,P+TPbL,and M+P+TPbL treatment groups were all weakly alkaline,while electrical conductivity?EC?of the single and compound cultivation groups was lower than that of the control groups.Oxidation-reduction potential?ORP?did not change much or even decreased in single planting of each plant.The content was higher than that of the control in compound cultivation.It was increased by 31.79%in the M+P+TPb L treatment groups compared to the control groups.Meanwhile,the content of dissolved oxygen?DO?has a tendency of increasing compared to the control groups.The change of biological oxygen demand?BOD?in each treatment group was small,but it has a significant difference in the treatment of M+P+TPbL in contrast with the control groups,which shows its demand for 98.25%of CK.The content of phosphoric acid and ammonia nitrogen in each treatment group has a tendency of decreasing compared with the control groups,but the purifying effect of Nuphar pumilum on ammonia nitrogen was not obvious.For the purification ability of heavy metals,the contents of Pb²⁺,Zn²⁺,and Cu²⁺have a tendency of decreasing compared with the control groups.Therefore,it shows that Canna glauca,Nuphar pumilum,and Hydrocotyle vulgaris have a strong ability to purify PbL.