The Studies On Phytoremediation Of Lead Tailings With Iris Halophila And I. Lactea Var. Chinensis And Their Tolerant Response

1. Effects of different portions of the lead tailings from Dexing, Jiangxi and garden soil on the growth and metals accumulation of Iris halophila Pall and I. lactea var. chinensis seedlings were studied by the pot experiment. The results show that the dry weights of I, halophila and I. lactea var. chinensis growing in the different portions of the lead tailings and garden soil were lower than the control, especially under the stress of pure lead tailings. dry root weights of I. halophila significantly decreased24.6%compared with the control and the dry shoot and root weights were lower22%and10.%than those of control showing that I. halophila was more tolerant than I. lactea var. chinensis. The absorption of Pb, Cu; Zn, Cd ions of two Iris species under the treatments with different portions of the lead tailings were higher than those of control and the absorption of K I. lactea var. chinensis was suppressed. Pb contents in the aboveground and underground parts were64.75and751.75μg/g. respectively and Pb contents in I. lactea var. chinensis were93.83and989.42μg/g under pure lead tailings. The absorption ability of Pb, Cu, Zn, Cd in aboveground of two species of Iris L. were lower than those in the control which indicated that those metals were mainly concentrated in the underground parts. The results indicated that I. halophila and I lactea var. chinensis have the potential for the remediation of lead tailings and Pb polluted environments and the I. halophila was more tolerant to Pb than I. lactea var. chinensis.2. The pot experiment was conducted on the effects of different concentrations of nitrogen (N) on the growth and accumulation of Pb and other metal ions in the seedlings of I. halophila and I. lactea var. chinensis. The results show that the aboveground dry weight of I. halophila at0.5g/kg N treatment was4.46times of control. N treatments could promote the aboveground growth significantly higher than the underground part. The role of higher N concentrations on plant growth was not significantly higher then lower N concentration treatment.I. lactea var. chinensis in0.25g/kg treatment achieved the greatest shoot growth. The tolerant index of I. halophila and I. lactea var. chinensis treated with N were higher than that of the control. N treatments significant inhibited on the the Pb and Zn accumulation of I.halophila and I. lactea var. chinensis. Absorption of Pb in aboveground and belowground parts of I.lactea var. chinensis in the high concentration of1g/kg N treatment decreased by15%and6.8%compared with the control. The accumulation of Pb and Cd in aboveground part of I.lactea var. chinensis at higher N treatment have a certain degree of inhibition, but these two ions in I. halophila had improved to some extent.3. The effects of organic acids on the growth and accumulation of Pb and other metal in the seedlings of I.halophila and I. lactea var. chinensis growing in the lead mine tailings were studied by pot experiment. The results show that EDTA, especially in high concentrations were producing certain adverse effects on the growth of I. halophila and I.lactea var. chinensis. The aboveground and underground dry weight of I. halophila at2mmol/kg citric acid (Tc) treatment were increased44.3%and54%of the control, respectively, indicating that Tc have a certain role to improve the tolerant and promote the growth of I.halophila. However, the growths of I. lactea var. chinensis were adverse effected by organic acids, especially2mmol/kg EDTA on the inhibition of I. lactea var. chinensis nearly30%compared with the control. Tc had a certain inhibitory effect on the Pb accumulation in aboveground part of I.halophila and EDTA could enhance Pb, Cd and Zn absorption in the aboveground and underground part. Tc and EDTA could improve the accumulation of Pb and Zn of I, lactea var. chinensis and promoting the role of EDTA was stronger. EDTA on the promotion of lead absorption of two species of Iris species and could improve the phytoremediation effect of lead tailings.4. Pot experiment was conducted by applying different organic acids in the lead mine tailings to examine anatomical structures and physiological indicators of I. halophila and I. lactea var. chinensis. The results show that the integrity of cell wasfound in the Tc treatment than the EDTA treatment which indicated Tc treatment was better for the protection of plant cells and better resistance to damage caused by the heavy metal pollution. Tc treatment was significantly enhanced the photosynthetic pigments formation of I. halophila, especially in the low concentration of0.5mmol/L Tc treatment and the chla, chlb, Cxc contents were increased18%,57%,62%, respectively than those of the control. However, photosynthetic pigments content of I. halophila decreased significantly in the treatment of2mmol/L EDTA. The changes of photosynthetic pigments contents in I. lactea var. chinensis were similar with I. halophila. the content changes of MDA in Tc and0.5mmol/L EDTA treatment were not obviously, while the high concentration of EDTA increases the content of MDA in I. halophila. AsA and GSH contents in I. halophila and I. lactea var. chinensis were enhanced by Tc treatments and improved the damage of oxidation resistance of the heavy metals. Lower EDTA treatment was as good as Tc treatments for increasing significantly the AsA and GSH contents, while, high concentration of EDTA played the contrary role and inhibited the production of AsA and GSH in the plants.