| The waste yard of the mercury and thallium mine area in the southwest of Guizhou province was characterized by low nutrient content,strong acidity,and rich in various toxic elements such as Tl,Hg,As and Sb.Currently,researches had shown that a large amount of metal sulfides in the waste of the mercury and thallium mine area had been exposed and stored for a long time.After natural weathering and rainfall washing,heavy metals such as Tl,Hg,As and Sb were continuously released and migrated into the surrounding soil,rivers and crops,causing environmental pollution and health risks of residents.Therefore,it is of great significance to carry out research on source control and ecological restoration of waste pollution release in mercury and thallium mine areas to improve the ecological environment quality of waste dumps in mercury and thallium mine areas and to protect residents’ health.Therefore,according to the pollution characteristics and bad environment characteristics of mercury and thallium mine waste,this research innovatively adopted fish manure with rich in various nutrients and red mud with strong heavy metal fixation effect,according to local conditions,combined with two typical herbaceous plants(ryegrass and jujuncao)with good climate adaptability and strong tolerance in the research area,six experimental groups were set up,namely: CK group(mercury and thallium mine waste),FY group(mercury and thallium mine waste +fish manure),FC group(mercury and thallium mine waste + red mud),FYC group(mercury and thallium mine waste + fish manure + red mud),FYCJ group(mercury and thallium mine waste + fish manure + red mud + jujuncao)and FYCH group(mercury and thallium mine waste + fish manure + red mud + ryegrass).By investigating the pollution control effect of red mud and fish manure combined with pioneer plants on the leachate of different batches of mercury and thallium mine waste within 150 days,the habitat improvement effect and biological effect of mercury and thallium mine waste,and investigated the corresponding impact mechanism.The discussion provided an important theoretical basis for the scientific guidance of typical polymetallic mine mining,beneficiation,and smelting effluent tailings waste disposal,the pollution in-situ control of the release and migration of compound pollutants in the storage yard and the ecological restoration of the mining environment.The main findings obtained are as follows:(1)The coupling effect of modifiers and plants can significantly improve the physical and chemical properties of different batches of mercury and thallium mine waste leaching liquids and effectively control the release of characteristic pollutants.Compared with the control group,the p H value of each treatment group gradually increased from acidic to near neutral,and the combined addition of fish manure-red mud modifier had a better effect on p H value than the single addition,and Eh,EC decreased to varying degrees.Compared with the control group,the dissolved amounts of Tl and Sb in the leaching fluid of mercury and thallium mine waste treated by combined restoration were obviously decreased.Compared with the CK group,the dissolution rate of As and Sb in the FYCH group decreased by 21.28%～51.94% and32.20%～34.20%,respectively,in the five leaching experiments.(2)The coupling of the modifier and the plant can significantly reduce the biological toxicity of the mercury and thallium mine waste leachate.In the germination toxicity test of ryegrass seeds,the FYCJ and FYCH groups had the best effect on improving the germination of ryegrass seeds,which increased the germination rate of ryegrass seeds from 17.78% in the control group to 77.78%～83.33%;FYCH group elongation of the leachate buds was 3.56～5.55 times that of the CK group in the five leaching times.In the zebrafish toxicity experiment,the CAT activity valued of zebrafish in the FYC and FYCH groups had been increasing,among which,compared with the leachate L1,the leaching solution L5 increased by 356.70%and 254.92%;The FYCJ and FYCH groups in each treatment groups POD activity were the highest,1.77～2.40 and 1.68～2.23 times that of the CK group,respectively.(3)The coupling of modifiers and plants can improve the physical and chemical properties of mercury and thallium mine waste at different depths.The p H of mercury and thallium mine waste at different depths in each treatment group increased from the acidity of the control group to near neutral;in each treatment group,on the whole,the Eh at the depth of 0-8 cm was higher,and the depth at the depth of 16-24 cm was lower.The Eh of CK,FC,FYCJ and FYCH groups decreased gradually with the increasing depth of mercury and thallium mine waste.(4)The coupling of modifier and plant can improve the nutrient content of mercury and thallium mine waste at different depths.Among the treatment groups,the content of available potassium at the depth of 0-8 cm was the highest;the FY group had the highest available phosphorus content at different depths of mercury and thallium mine waste,which was 3.36～4.37 times that of the CK group;the organic matter content of each treatment group was the highest.The variation range was2.50～3.56 g/kg,and the maximum value appeared at the depth of 16-24 cm in the FY group;the content of alkaline hydrolyzable nitrogen in the CK,FY and FC groups showed a continuous increasing trend with the increase of mercury and thallium mine waste depth.(5)The bacterial community richness in the FYCH group was the highest in each treatment group after the modifier was coupled with plants,and the Chao1,Ace indices were 18.45 and 18.74 times that of the CK group,respectively;the Shannon index of each treatment group was 2.11～3.10 times that of the CK group,indicating that amendments combined with phytoremediation can not only increase the community species richness in the mercury and thallium mine waste dump,but also improve the diversity of community species in the dump.In summary,aquaculture waste(fish manure)rich in nitrogen,phosphorus,potassium,carbon and other nutrients and industrial waste(red mud)rich in iron,aluminum and alkaline substances were discarded as mercury and thallium mine through resource utilization.On this basis,combined with the local warm-season large herb jujuncao and cool-season suitable plant ryegrass for ecological restoration,it can significantly control the pollution release of mercury and thallium mine waste and effectively improve mercury and thallium mine nutrient characteristics of mine waste and yard habitat conditions.Therefore,the combined remediation of modifiers and plants can comprehensively realize the in situ ecological control,habitat improvement and significant improvement of biological vegetation of mercury and thallium mine waste pollution. |
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