| Environmental pollution caused by abandoned mine becomes increasingly serious,while corresponding treatment measures couldn't achieve significant results.Tailings,formed during mining and processing,still threaten local environment.A typical abandoned alunite mine in Lujiang county was selected as the research area.The negative effect of this abandoned mine on surrounding environment was analyzed,in order to provide a systematic management countermeasure.The ecological environment has been destroyed to a certain degree until the mine was closed after a long-term mining history.Especially,serious phenomena such as acidification of water body and heavy metals(HMs)pollution of soils,are the currently important issues which should be solved as soon as possible.Hence,samples of soil,water and plant were collected.The distribution and enrichment characteristics of typical HMs in the soils around mining area were ascertained,and the water acidification mechanism was illuminated.Meanwhile,the adsorption and enrichment capacity of dominant plant on typical HMs was still analyzed.The main conclusions are as follows:(1)The pH test results of the pit water samples in the mining area are all greater than5,while the pH test results of the effluent water from the subsidence pond and the east and west mountains are only about 3,which is caused by the different contact reaction time between the pit water and the surface ore.The strong acidity of the effluent from the east to the west is due to the large amount of rainfall infiltrating into the underground through the internal cracks in the mine.During the infiltration process,it fully contacts and reacts with the ore inside the mine,and due to the connectivity of the roadway,the leaching waste water and groundwater are in the two flats The mouth pooled out,causing the water in this area to acidify.From the analysis of acid ions of different types of water samples,it is confirmed that the phenomenon of ionization of alum in water does exist,and from the XRD results of slag samples taken at different depths,it can be seen that the alum content of the deep slag and the alum under the surface and water immersion conditions The huge difference in the content directly confirms that the alum in the slag is the main reason for the formation of water acidification.XRF analysis results show that there is another important reason for the acidification of water quality is the oxidation of sulfide ore contained in the mine.(2)The soil in the mining area is generally acidic,and the content of HMs elements in agricultural land decreases with the increase of soil depth,which may be due to theinfluence of the soil redox potential changes.The content of HMs has a relatively obvious upward trend.The results of single factor pollution index,geo accumulation index and potential ecological risk coefficient show that As and Cd pollution are the most serious in the study area,followed by Cu and Pb.The highest single pollution risk index is also the As and Cd elements,which is also the dominant factor in the potential ecological risk of soil in the region.The comprehensive potential ecological risk index shows that,except for a small part of the high potential ecological risk,most soil samples have a RI significantly greater than 600,which is at a very high potential ecological risk.(3)The 17 species of plants sampled around the mining area all grew well,indicating that they have a certain tolerance to these eight heavy metals.As the pollution of As and Cd in the soil of the study area is the most serious,the survey results show that Ophiopogon bodinieri Levl?Haloragis micrantha(Thunb.)R.Br and Viola philippica have good absorption and transport capacity for As and Cd in the soil.The enrichment coefficients and transport coefficients of As along Ophiopogon bodinieri Levl and Haloragis micrantha(Thunb.)R.Br are both greater than 1;The enrichment coefficient of Viola philippica to As is less than 1,but the transfer coefficient reaches 2.5;However,the enrichment coefficients of Cd along with Ophiopogon bodinieri Levl and Haloragis micrantha(Thunb.)R.Br are less than 1,and the enrichment coefficient of Viola philippica for Cd is 1.79,which indicates that Viola philippica has a better enrichment effect for the element Cd.The Cd transfer coefficients of these three plants are all greater than 1,which can be used as dominant plants to provide support for the remediation of heavy metal pollution in the soil of the abandoned alum mining area.According to the characteristics of acid-mine drainage and the HMs pollution in the mining area,the AMD treatment technical measures and soil remediation technical schemes were generated.Hence,the research poses relatively practical significance and predictable application prospect.Figure [15] Table [25] Reference [137]... |
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