Abstract: Lead-zinc slag is prone to heavy metal migration in an acidic environment,posing potential ecological risks to the mine and the surrounding geological environment. The study took the waste slag from a lead-zinc mining area in the western section of the Qinling Mountains in Shaanxi Province as the object,carried out static immersion tests in different initial acidic environments,and conducted mechanism analysis. The results showed that:① The pH of the soaking solution increases slowly at first and then tends to stabilize with the extension of soaking time. With the extension of soaking time,the electrical conductivity (EC) of the soaking solution firstly decreased and then tended to be stable when the initial pH was 1 and 2;It firstly decreased significantly and then increased significantly when the initial pH was 3;And it rose and then tended to be stable when the initial pH was 4,5,6 and 7. ② The release rates of the five heavy metal elements,Zn,Pb,Cu,Cd,Cr,all showed an overall downward trend with the increase of the initial pH and the extension of the soaking time. Under the condition that other factors are the same,the differences in the release rates of the five heavy metal elements may be related to the different dissolution and displacement rates of each heavy metal element. In the environment with an initial pH of 1 and 2,the release amounts of the five heavy metal elements are relatively large,showing the characteristics of increasing slowly at first and then decreasing. Under the same initial pH environment,the release amounts of heavy metal elements Pb and Zn are significantly larger,which is related to the content of heavy metal elements in the slag and the activity of related minerals. ③ With the continuous soaking, the distribution of pore size D increases more significantly in the environment with a lower initial pH,and the size and connectivity of the pore size are significantly higher than those in the environment with a higher pH. ④ The acid dissolution process of carbonate minerals such as dolomite in the ore sample is the fundamental cause affecting the electrical conductivity,pH of the soaking solution,pore structure,etc. The acid dissolution of heavy metal minerals is the fundamental cause of the release of heavy metal ions. The adhesion of weakly dissolved substances generated during the acid dissolution process to the surface of the slag leaching particles and their pores and fissures is an important reason that hinders the development of pores and fissures and the dissolution of heavy metal ions. Therefore,to control the release of heavy metal ions from ore piles into the environment,the focus should be on the factors of the accumulation environment and the accumulation duration.

Key words: lead-zinc slag,acidic environment,heavy metal,release migration,acid etching mechanism ,