| Taking the phytoremediation of Hunan manganese ore slag as the research object,this paper aims to explore the phytoremediation effect and preliminary mechanism of manganese ore slag.In the first stage,woody plants Paulownia and Nerium indicum were used as the material of test.Under the condition of improving the manganese slag(Control CK:100%manganese slag + 0.1Kg phosphate fertilizer;Improved A:95%manganese slag+0.1 Kg phosphate fertilizer;Improved B:90%manganese slag +10%peat soil +0.1 Kg phosphate fertilizer;Improved C:85%manganese slag + 15%peat soil+0.1Kg phosphate fertilizer),it not only analyzed the plant height and biomass growth of woody plant in the improved manganese slag,but also the matrix cation exchange and organic matter content,and then analyzed the tolerance and accumulation characteristics of woody plants to complex heavy metals;In the second stage,a kind of herb,Boehmeria nivea,was added in the test based on the woody plants Paulownia and Nerium indicum for contrast.Under the condition of optimized and improved manganese slag(Control CK:100%manganese slag+0.1 Kg phosphate fertilizer;Improved A:90%manganese slag + 10%peat soil +0.1 Kg phosphate fertilizer;Improved B:80%manganese slag +20%peat soil +0.1Kg phosphate fertilizer;Improved C:70%manganese slag +30%peat soil +0.1 Kg phosphate fertilizer),it compared the plant root structure in the improved manganese slag,the plant height and biomass growth,the matrix cation exchange and organic matter content and the soil urease and catalase activity,analyzed the tolerance and accumulation characteristics of woody plants to complex heavy metals,and then tested and analyzed the distribution of manganese subcellular in the plant,the characteristics of chemical form as well as the relationship between tolerance mechanism.This research aims to provide new theoretical basis and practical parameters for phytoremediation of heavy metal contaminated soil.The main results of research are as follows:1.Research on the phytoremediation effect of the woody plants after the improvement of manganese slag(1)Plant height increment and biomass increment of Paulownia and Nerium indicum present a trend of "Improved C>Improved B>Improved A>Control CK".In the Control CK,Improved A and B,Paulownia plant height increment were higher than Nerium indicum;The biomass increment of Nerium indicum in the improved groups were higher than that of Paulownia.(2)After Paulownia and Nerium indicum grow,Mn content in the matrix were presented a trend of "Control CK>Improved A>Improved B>Improved C";At the same time,organic matter content and cation exchange capacity in the matrix both increased,and it showed a significant positive correlation.And they were basically present a trend of"Improved C>Improved B>Improved A>Control CK",especially the improved groups of cation exchange capacity are significantly higher than the CK group.(3)In addition to Zn,the contents of Mn,Pb and Cu in Paulownia and Nerium indicum underground part were higher than that in the ground,and the contents of Mn,Zn,Pb and Cu in each CK group were higher than that in improved groups;Pb,Cu enrichment coefficient in Paulownia and Zn,Cu enrichment coefficient in Nerium indicum were presented a trend of "Control CK>Improved A>Improved B>Improved C";the transfer coefficient of Mn,Pb and Cu was low,and there was no significant difference in transfer coefficient between different treatments;the coefficient of transfer quantity was generally presents improved groups>CK group,but the difference in improved groups was not significant.2.Research on the repair effect and preliminary mechanism of the woody plants after the improvement and optimizztion of manganese slagwith(1)To add modifier can not only effectively reduce the content of heavy metal of matrix,but also improve the content of organic matter in the matrix and cation exchange.What’s more,the content of organic matter and cation exchange were gradually increased with the increase of modifier concentration,representing the rule of "Improve C>Improve B>Improved A>Control CK".(2)To add modifier can also improve the activity of urease and catalase,which were gradually increased with the growing concentration of modifier.These two indexes had a significant negative correlation with the heavy metal Mn,Zn and P,while the two enzymes had a significant positive correlation with the organic matter.Besides,the catalase showed a positive correlation with cation exchange volume.All of these results indicated that the organic matter in the soil is the main factor affecting the activity of soil enzyme.(3)The determination result of physiological indicators of plants showed that,the root of plant after improvement was more developed,and both the biomass and plant height were dramatically improved.Although the biomass and plant height varies among different species,all the plants basically represented the trend of "Improved C>Improved B>Improved A>Control CK".It can be clearly seen that,improvement has a significant effect on the growth of plants.From which,the change of plant height increase of Boehmeria nivea was most prominent,which was about the double of Paulownia and Nerium indicum.However,there was no obvious advantage on the growth of biomass.(4)There was a highest content of Mn in the plant,while the content of Zn,Pb and Cu was lower.In general,the content of heavy metal of plant underground is higher than that of the upper part of the ground,and the transfer factor was not more than 1.The content of heavy metal of each position followed the rule of "Control CK>Improved A>Improved B>Improved C",which was lower than the content of heavy metal in the matrix,the concentration coefficient was not greater than 1.Meanwhile,the addition of modifier can obviously improve the transfer coefficient of heavy metal,representing the rule of"Improved C>Improved B>Improved A",i.e.the increase of modifier concentration is helpful to improve the turn-over capacity of plant to the heavy metal,which can increase the amount to transfer the heavy metal from the underground to the overground part.The result indicated that the transfer coefficient of Paulownia and Nerium indicum was higher than that of Boehmeria nivea.(5)Mn in Paulownia is mainly stored in cell wall.Mn in the root and stem of the Nerium indicum is also mainly stored in cell wall.In the leaves,as the concentration of the modified agent increases,the manganese in some soluble components is transferred to the cell wall.The soluble components of Boehmeria nivea root,stem and leaf were higher than those of the other two plants,indicating that vacuole can also be used to isolate Mn.However,in general,different treatments did not change the distribution pattern of Mn distribution in the dominant position of cell wall.(6)Mn in Paulownia is mainly NaCl extraction state and deionized water extraction state.Mn in Nerium indicum is mainly NaCl extraction.Mn in Boehmeria nivea is mainly deionized water extraction state and NaCl extraction state.It can be seen that the heavy metal Mn exists mainly in the form of protein binding state or adsorption state and pectinate. |
