Diversity And Metal Ion Tolerance Of Microbial From Lead-zinc Mine Tailings In The Qinling Mountains

Lead-zinc mines have important value in modern industry,especially in chemical industry and electronics industry.Lead-zinc mines in Qinling Mountains area are more frequently mined,and a large amount of remaining tailings after refining are accumulated in nature.Metal lead and zinc are all heavy metals.After extraction,tailings contain a large amount of heavy metals,acids and alkalis,which cause serious environmental pollution.At present,physical isolation control,natural accumulation and degradation,chemical treatment and plant adsorption are mainly used,but all have certain limitations.In this study,the microbial diversity of lead-zinc tailings soils in three mines in Ningqiang and Lueyang in the Qinling Mountains was analyzed using culture method and high-throughput sequencing method,from the certain concentration of heavy metal elements,screen out functional microorganisms with tolerance,andconductenvironmental remediation experiments on the selected microorganisms.This study willrestore lead-zinc tailings contamination from a microbial perspective and provide experimental basis and theoretical support.The main conclusions obtained are as follows:?1?Separation,purification and cultivation of soil microorganisms from lead-zinc mine tailings in three places were conducted using six kinds of separation media,a total of 5phylum,12 genus and 27 species were obtained,it was found that 1/10 ATCC-172 medium is more prominent in the separation of lead-zinc tailings microorganisms,and can be used as the optimum medium for the separation of lead-zinc tailings soil microorganisms,in the five kinds of actinomycetes isolation medium.The microbial diversity and genetics of the three mines were analyzed.It was found that the Ningqiang Yanzibian tailing soil bacteria species of the diversity,it were better than the other two tailing soil samples.A total of 25 bacteria were isolated from 5 phylum and 8 genus,among them.The second is the diversity of bacteria in soils of lead-zinc tailings in Lueyang Jianchaling,and 25 strains of bacteria belonging to 7genera in 2 gates were isolated.In Ningqiang Shanping lead-zinc mine tailings,35 strains of cultivable bacteria in 5 genera of 2 gates were isolated.High-throughput sequencing of the16S rDNA metagenomes of three lead-zinc tailings soils revealed that the richness of microorganisms in the Ningqiang Yanzibian lead-zinc tailings was the highest.There are 26phylum,40 classes,60 orders,118 families,and 233 genus bacteria.Followed by a total of 18gates,37 classes,55 orders,123 families,and 260 genus bacteria in the tailing soil of the Shanping lead-zinc mine area in Ningqiang.In Jianchaling lead-zinc mine area in Lueyang,there are 13 gates,21 classes,44 orders,81 families and 135 genera in the tailing soil.Among the three lead-zinc mine tailings,the dominant phylums are Proteobacteria,respectively accounted for 65.32%,74.03%and 59.31%.The Actinomycetes in the three tailings soils all became the second excellent gates,which also accounted for a certain proportion,which were7.91%,21.87%and 35.43%respectively.Subsequently,the humidity,pH,and six metal element contents of the three lead-zinc mine tailings were analyzed.The results showed that the soil moisture in the tailings of the three areas was between 5.55%and 6.95%,and the pH was slightly acidic,ranging from 5.01 to 6.77.The content of Pb²⁺in the three regions was7.61,28.83 and 136.47 times of the maximum range of normal soil in China.It has even exceeded 1.90,7.21,and 34.12 times the maximum standard of contaminated soil in China,respectively.The contents of Zn²⁺and Cu²⁺are also higher than the national three-level pollution standards,and the contents of metal ions Pb²⁺in the three places are approximately similar to that of Jianchaling>Shanping>Yanzibian.?2?For the tolerance of metal ions,all the isolated strains were screened for metal ion tolerance,and a total of 15 strains with high tolerance were screened out,after screening,the highest tolerance of some strains showed Pb²⁺2200mg/L,Zn²⁺2400mg/L,and Cu²⁺700mg/L.Liquid fermentation and adsorption experiments were performed on the selected two actinomycetes.The results showed that under the same culture conditions,when the initial concentration of Pb²⁺ions was 350 mg/kg,the initial concentration of Zn²⁺ions was 300mg/kg,and the initial concentration of Cu²⁺ions was 100mg/kg.Strain LJL24 has better adsorption effect on metal ions Cu²⁺and Zn²⁺than strain NSC1,but its adsorption effect on Pb²⁺is slightly lower than that of strain NSC1.The adsorption percentage of metal ion Cu²⁺by strain LJL24 reached 92.67%,which was nearly 1 times higher than that of strain NSC1.The adsorption percentage of strain LJL24 to metal ion Zn²⁺was 9.09%,while the adsorption percentage of strain NSC1 was 1.73%.?3?In terms of environmental remediation,the selected strains were liquid-fermented and then metal ions contaminated the soil.It was found that the growth status of the indicator plant cucumbers was improved to varying degrees,compared with the original contaminated soils.The cucumber seedlings added with the fermentation product of the test strain grow well.From the data of cucumber plant height,root and stem ratio,and dry and wet weights,the results showed that the selected fermentation products of NSC1 and LJL24 actinomycetes were treated with three heavy metal ions:Pb²⁺,Zn²⁺,and Cu²⁺.There was a significant effect on the growth of cucumber seedlings planted in soil.The study found that the root length of cucumber seedlings was significantly increased after adding NSC1 fermentation product to Pb²⁺-contaminated soil,while the root length of cucumber seedlings grown in Zn²⁺-contaminated soil was significantly increased by the addition of LJL24 fermentation product.When the final metal ion content of cucumber seedlings was examined,it was found that the contents of heavy metal ions in the cucumber seedling plants that were partially added to the fermentation product of the strain were reduced.For example,the fermentation product of strain NSC1 had a significant inhibitory effect on the absorption of Pb,Zn and Cu elements in cucumber seedling plants grown in soil contaminated with Pb²⁺,Zn²⁺and Cu²⁺.There are also some cases of increased,such as strain LJL24 fermentation products on the Pb²⁺,Zn²⁺and Cu²⁺soil after the growth of cucumber seedling plants grown in the Pb,Zn and Cu elements have a significant role in promoting the absorption.