Study On Tolerance And Phytoremediation Potential Of Several Floating Plants To Leachate From Lead Tailing

In this paper,Salvinia cuccullata,Pistia stratiotes and Salvinia natans were selected as experimental materials to study their tolerance to lead tailings leaching?LTL?and their ability to repair leachate quality from lead tailings.The results are as follows:?1?The treatment of leachate from lead tailings with different concentrations has different effects on the growth and metal ion enrichment of Salvinia cuccullata and Salvinia natans.Low concentration LTL treatment could promote the accumulation of biomass of Salvinia cuccullata and Salvinia natans.The number of leaves,axillary buds and fresh weight of Salvinia cuccullata increased first and then decreased with the increase of the concentration of leachate from lead tailings.The number of leaves and axillary buds of Salvinia cuccullata and Salvinia natans reached the maximum under25%LTL treatment,and the fresh weight of Salvinia cuccullata reached the maximum under 25%LTL treatment,which was 1.3 of the control.The fresh weight of Salvinia natans treated with 50%LTL was 1.12 times higher than that of the control.High concentration of LTL could inhibit the growth of Salvinia cuccullata and Salvinia natans.The transport coefficients of Salvinia cuccullata for each metal ion are Zn²⁺?29?Cd²⁺?29?Cu²⁺?29?Ca²⁺?29?Pb²⁺,and those of Salvinia natans for each metal ion are Zn²⁺?29?Pb²⁺?29?Ca²⁺?29?Cu²⁺?29?Cd²⁺.Under 100%LTL treatment,the enrichment coefficients of Cu²⁺in Salvinia cuccullata and Salvinia natans were 1.92 and 1.78 times higher than those in the control,respectively.Under 25%LTL treatment,Salvinia cuccullata and Salvinia natans had the strongest enrichment ability of Zn²⁺.?2?Lead tailings leachate with different concentration of lead tailings effluent treatment had inhibitory effect on photopigments of Salvinia cuccullata and Salvinia natans,Salvinia cuccullata chlorophyll a,chlorophyll b and carotenoids were negatively correlated with LTL treatment concentration(r=-0.6250^?9?,r=-0.3674,r=-0.5871),Salvinia natans chlorophyll a,chlorophyll a,chlorophyll b and carotenoids were negatively correlated with LTL treatment concentration(r=-0.9251^?9??9?,r=-0.8570^?9??9?,r=-0.5890).The integrity of cell membrane permeability in the leaves of Salvinia cuccullata was better under LTL treatment of different concentrations.With the increase of LTL treatment concentration,the conductivity of Salvinia cuccullata leaves showed a downward trend,which was 103%,69.70%,69.70%and 72.73%of the control,respectively.The MDA content in the submerged leaves of Salvinia cuccullata and Salvinia natans was higher than that in submerged leaves under low concentration treatment.With the increase of LTL concentration,the MDA content in submerged leaves of Salvinia cuccullata and Salvinia natans increased gradually.The activities of SOD,POD,CAT and glutathione in the floating leaves of Salvinia cuccullata and Salvinia natans were higher than those in the submerged leaves,reflecting that the antioxidant capacity of cells in the floating leaves of Salvinia cuccullata and Salvinia natans was stronger than that in the submerged leaves.There was a negative correlation betweenthecontentofsolubleproteinandtheconcentrationofLTL(r=-0.9785^?9??9?,r=-0.9692^?9??9?),and there was a significant difference among the treatments?p?27?0.01?.?3?Salvinia cuccullata and Salvinia natans can improve the quality of leachate from lead tailings with different concentration.Under 100%LTL treatment,the conductivity of the treated liquids decreased 26.59%and 27.46%.The redox potentials of the solutions of Salvinia cuccullata and Salvinia natans were positively correlated with the LTL concentration(r=0.9684^?9??9?,r=0.9426?9??9?);the dissolved oxygen content of the solutions of Salvinia cuccullata and Salvinia natans increased by 0.4%,0.6%,0.9%and 1.3%respectively compared with the control;and the oxygen demand of the solutions of Salvinia cuccullata and Salvinia natans was positively correlated with the LTL concentration(r=0.6437^?9?,r=0.9042^?9??9?).Salvinia cuccullata and Salvinia natans can effectively remove ammonia nitrogen and phosphate from sewage treated with low concentration LTL.The contents of Ca²⁺,Cd²⁺,Pb²⁺and Zn²⁺in the treatment solution of cultivated Salvinia cuccullata were positively correlated with the LTL treatment concentration(r=0.9204^?9??9?,0.9320^?9??9?,0.9394^?9??9?,0.9366^?9??9?).The contents of Ca²⁺,Cd²⁺,Pb²⁺and Zn²⁺in the treatment solution of cultivated Salvinia natans were positively correlated with the LTL treatment concentration(r=0.9084^?9??9?,0.9701^?9??9?,0.9597^?9??9?,0.9829^?9??9?).?4?Under non-adversity stress,Salvinia cuccullata and Salvinia natans had significant effects on improving the pH value of water body.There was a positive correlation between substrate pH and days of treatment under the treatments of Pistia stratiotes+Salvinia cuccullata,Pistia stratiotes+Salvinia natans and Pistia stratiotes+Salvinia cuccullata+Salvinia natans.(r=0.3371,r=0.4342,r=0.4880,r=0.6819^?9?).Under the treatment of three floating plants,and the effect of improving LTL water pH was the best.Under LTL treatment,the electrical conductivity of single plant of Pistia stratiotes,Salvinia cuccullata and Salvinia natans was negatively correlated with the treatment days(r=-0.9085^?9??9?,r=-0.9036^?9??9?,r=-0.8122^?9??9?),Pistia stratiotes+Salvinia cuccullata,Pistia stratiotes+Salvinia natans and Salvinia cuccullata+Salvinia natans combined cultivation under LTL treatment,the electrical conductivity of the treatment solution was negatively correlated with the treatment days(r=-0.7754^?9??9?,r=-0.9218^?9??9?,r=-0.9242^?9??9?).Pistia stratiotes+Salvinia natans and Salvinia cuccullata+Salvinia natans,the decrease of conductivity in the treatment solution was more obvious under the compound cultivation.Under non-adversity stress,Salvinia cuccullata and Salvinia natans.consumed more dissolved oxygen in the water,Pistia stratiotes had no significant effect on improving dissolved oxygen in the water.Pistia stratiotes+Salvinia cuccullata,Pistia stratiotes+Salvinia natans and Salvinia cuccullata+Salvinia natans combined cultivation under LTL treatment,the total biological oxygen demand?BOD?increased first and then decreased.The correlation coefficient between BOD content and treatment days was not significant?r=-0.0119,r=-0.0068,r=0.3090?.Pistia stratiotes+Salvinia cuccullata+Salvinia natans combined cultivation,there was a positive correlation between BOD content and treatment days?r=0.2646?.The ammonia nitrogen content in the treatments of Pistia stratiotes+Salvinia cuccullata,Pistia stratiotes+Salvinia natans,Pistia stratiotes+Salvinia cuccullata+Salvinia natans decreased 36.38%,37.71%and 32.95%respectively compared with the control group.The combination of Salvinia cuccullata+Salvinia natans combined cultivation had the best effect on water phosphate removal,followed by Pistia stratiotes+Salvinia cuccullata+Salvinia natans,the three floating plants compound cultivation of Pistia stratiotes+Salvinia cuccullata,Pistia stratiotes+Salvinia natans had the best effect on phosphate removal,Salvinia cuccullata,Pistia stratiotes and Salvinia natans can also effectively reduce the content of phosphate in LTL solution.The enrichment of Ca²⁺,Zn²⁺by Salvinia cuccullata,Pistia stratiotes and Salvinia natans is not obvious,and the enrichment effect of Cu²⁺is the best.The enrichment effect of Cd²⁺in water was better under the combined cultivation of Pistia stratiotes and Salvinia natans.The effects of combined cultivation on the absorption of Pb²⁺in water were better.Generally speaking,the metal ion enrichment ability of Pistia stratiotes was the strongest under LTL treatment compared with that of Salvinia cuccullata and Salvinia natans.