Research On The Release Of Antimony And Its Hydrogeochemical Behavior In Karst Underground Rivers In Qinglong Antimony Mine Area

The tailings pond generated by the Qinglong antimony mine has accumulated millions of tons of tailings and smelting slag.Unburocked slag is stacked directly in the open air.After weathering,natural rainfall,and flushing of surface water,the heavy metal elements such as Sb contained in it are exposed or scrubbed on the surface and underground,and accompanied by runoff,it flows into the karst water environment in the area,it has greatly threatened the ecological environment and human health.In this paper,the physical and chemical properties of Qinglong antimony tailings were analyzed.A self-designed multi-layer leaching experimental device was used to simulate the static/dynamic leaching and multi-layer leaching experiments of natural rainfall on antimony tailings.At the same time,based on the field monitoring results,the hydrogeochemical behavior of Sb in the karst underground river system in the Qinglong antimony mine area is explored,and the migration,transformation,and release mechanism of Sb are mutually verified.The main research results are as follows:（1）The main mineral components in the Qinglong antimony tailings obtained through testing include fluorite,pyrite,quartz,calcite,gypsum,stibnite,etc.The characteristics of Sb release in antimony tailings with different particle sizes were explored by static leaching experiment,when the particle size was d₁<1.18mm,the release concentration of Sb in static leachate could reach up to 326.1μg/L,that is,the smaller the particle size（larger the specific surface area）in the tailings,the greater the concentration of Sb release in the static leachate.（2）In the dynamic leaching experiment,three rainfall intensities（25,50,100 mm/h）were used to continuously leach the antimony tailings for 36 hours.The effects of rain intensity on the relevant indexes of antimony tailings leachate were as follows:p H increased with the increase of rain intensity,and EC decreased with the increase of rain intensity,among which the cumulative range of rainfall leaching Sb release of I=100 mm/h,I=50 mm/h and I=25 mm/h were 4.88～5096.06μg/kg,5.60～2646.00μg/kg,2.97～1076.67μg/kg,respectively.that is,within the same time,the cumulative release of Sb increases with the increase of rain intensity;Interval rainfall leaching simulates the process of soaking and dynamic leaching of antimony tailings in rainwater,using rainfall intensity I=100 mm/h for leaching for 2 hours,with an interval of 4 hours,and a total rainfall duration of 12 hours.Compared with continuous rainfall leaching,the impact of various indicators in the leaching solution is as follows:with each cycle,the p H decreases and the release concentration of EC and Sb increases,especially after the fifth interval,the Sb release concentration can increase from 422.8μg/L to 532.0μg/L.The cumulative release of Sb from intermittent rainfall eventually reached 3511.85μg/kg.This is an increase of 942.72μg/kg compared with continuous rainfall,which proves that the release of Sb will increase and enhance under intermittent rainfall conditions.（3）The multilayer leaching experiment simulated the transport characteristics of Sb in carbonate rocks in the leachate of antimony tailings.The cumulative release range of single-layer leaching Sb is:5.60～2646.00μg/kg,and the cumulative release of multi-layer leaching Sb after carbonate rock addition in the lower part is 2.42～1575.51μg/kg,which is a year-on-year decrease of 1070.49μg/kg.The heavy metal Sb ion reacts with calcite in carbonate rock,which reduces the release concentration of Sb.The curves of different stages of Sb release in static leaching experiments,different rainfall intensities,and multilayer leaching experiments were mathematically fitted.The curve of the separation of antimony release concentration with time was well fitted by the modified Elovich equation,which could reveal the mechanism of Sb release under different conditions.（4）Different karst underground river systems in Qinglong antimony tailings area were sampled,and the test showed that the heavy metal content in different karst underground river systems was different,and the highest concentrations of Sb in the sampling points of Duck underground river and Longpengwei underground river were 5.54μg/L and 14.35μg/L,respectively.Among them,Sb,As and Fe are the landmark pollutants in the study area.The relationship between the concentration of Sb along the underground river and the flow distance was inversely proportional,and the change characteristics of the water chemical type along the runoff path of the karst underground river system were revealed,and the HCO₃-Ca types water were gradually changed to SO₄-Ca types water.The PCA method was used to indicate the influence of various indexes in the regional karst underground river system.Common ions and carbonate rocks in karst groundwater systems have a certain effect on the migration and transformation of Sb,such as the adsorption of Sb by HCO₃^-and Fe³⁺.The hydrogeochemical behavior characteristics of Sb in the regional karst groundwater system were revealed,which could be verified with indoor experiments.