| Bryophytes have strong functions of water absorption and retention,and their special physiological characteristics are conducive to the enrichment of heavy metal(HMs)in the environment.Bryophytes have excellent resistance to stress,and it plays an irreplaceable role in the ecological restoration of mining area.Up to now,many scholars are interested in bryophytes and most of the researches on bryophytes are concentrated in the northwest desert area and karst rocky desertification area,and the researches mainly focused on bryophyte species diversity and HMs monitoring in mining areas.The HMs biogeochemical characteristics in the system of manganese slag-bryophytes-water and the influence mechanism is very important,it can provide theoretical basis for bryophytes as the pioneering plant in the mining area.In this study,the typical manganese mine residue in eastern Guizhou was the research object.Bryophytes species in manganese slag(MS)and electrolytic manganese slag(EMS)were investigated.In this paper,the absorption characteristics of dominant bryophytes to HMs,effects of bryophytes on HMs migration in manganese ore residues and water,physiological response and tolerance mechanism of bryophytes about HMs,and the effects of bryophytes on microbial community structure and vascular plant colonization in manganese ore residues were systematically studied.The aim of this study is to reveal HMs biogeochemical characteristics in the system of manganese slag-bryophytes-water and the influence mechanism.It will provide scientific basis for bryophyte as the pioneering plant of vegetation ecological restoration in mining area.The main results of this study are as follows:(1)There were bryophytes growing on the waste residue of manganese mine.There were 32 species of mosses in MS,and there were 21 species of mosses in EMS.The dominant families in the two kinds of slag yard all was Pottiaceae.The dominant bryophytes in MS were Campylopus schmidii,Gymnostomum subrigidulum,Pohlia gedeana,and Bryum atrovirens,while the dominant bryophytes in EMS were Funaria microstoma,G.subrigidulum,P.gedeana,and B.atrovirens.(2)The bryophytes had a strong cumulative effect on Mn and Cd in the waste slag area of manganese ore.In MS,the content of Mn in bryophyte was 6047.43mg·kg-1,followed was Cd,the content of Cd was 5.78 mg·kg-1.In EMS,The maximum content of Mn and Cd was 6947.43 mg·kg-1and 3.22 mg·kg-1,respectively.In two spoil area,the enrichment coefficients of bryophytes for Cd were 5.35 and 2.05,respectively.Bryophytes showed strong enrichment ability for Cd.The contents of Mn,Cr,Cu and Pb of bryophytes in the manganese mine waste residue area were significantly positively correlated with the contents in the growth matrix,with the correlation coefficients being 0.834,0.947,0.797 and 0.968,respectively.(3)Bryophytes have reduced the proportion of weak acid dissolved Mn and Cd in MS,and the reduction rates were 5.20%and 1.80%,respectively.In EMS,bryophytes decreased the proportion of residual Mn,Cd,Pb and Zn,while increased the proportion of weak acid dissolved Mn,Cd and Zn,which increased by 18.81%,9.05%and 4.51%,respectively.Bryophytes can effectively reduce the concentration of HMs in the leachate,and the concentration of Mn in the leachate is reduced by98.92%in MS.In EMS,the concentration of Cd decreased by 86.45%,followed by the concentration of Mn decreased by 61.39%.The concentration of Mn and Cd in leachate was decreased by bryophytes absorption.(4)Bryophytes increased the deposition of HMs by increasing the thickness of cell wall.The content of Mn was the highest in bryophytes,the leaf surface had highest percentage of Mn atoms with 3.83%,followed by chloroplast and cell wall,and the percentage of Mn atoms was 0.12%and 0.11%,respectively.Cd is mainly distributed in vacuoles with an atomic percentage of 0.82%,followed by cell wall with an atomic percentage of 0.63%.Pb and Cu were mainly deposited on the cell walls of bryophytes with atomic percentages of 5.74%and 7.22%,respectively.At the same time,bryophytes can reduce the damage of HMs by increasing the activity of antioxidant enzymes and the content of metallothionein.(5)Bryophytes significantly increased the content of available nutrients in the waste residue.In MS,the content of AN,AP and AK increased by 88.00%-540.00%,82.00%-133.00%and 49.97%-207.00%,respectively.The content of AP increased by70.94%in EMS.Bryophytes significantly increased the p H value of waste residue in EMS,and increased by 20.19%?51.08%.At the same time,bryophytes significantly increased the diversity of bacterial community structure in the manganese mine waste residue area.In MS,the Shannon index and Chao index of bacterial community increased 1.07%-9.27%and 29.28%-53.22%,respectively.In EMS,Shannon index increased by 73.28%?112.21%,Chao index increased by 20?21 times.Bryophytes provided well conditions for germination,growth and development of ryegrass seeds in the waste residue area,and promoted the absorption and transport of heavy metals in ryegrass.Bryophytes can be used as the pioneer plants for ecological restoration in the waste residue area of manganese ore. |
PDF Full Text Request