Abstract: In order to investigate the effects of biochar and cyanobacterial crust on the leaching and migration behavior of
soil cadmium (Cd) in mining areas subjected to freeze-thaw cycles,soil column leaching experiments were conducted using indoor
freeze-thaw cycles and simulated precipitation. The analysis included pH,electrical conductivity,cumulative release,vertical
migration rate,and vertical migration amount of Cd2+ in the soil leachate. Additionally,Hydrus-1D was employed to simulate
the long-term migration of Cd2+ in the soil. The results show that freeze-thaw can increase the pH and Cd2+ cumulative release
of soil leaching solution during leaching. The freeze-thaw cycle increased the vertical migration rate of Cd2+ ,and the Cd2+ content
of CK,B,C and CB in 10~20 cm soil layer increased by 9. 90%,6. 94%,5. 49% and 3. 97%,respectively,compared with
that before freeze-thaw cycle. The synergistic use of biochar and cyanobacterium crust could alleviate the adverse effects of
freeze-thaw cycle. In the next 20 years,the synergistic use of biochar and cyanobacteria crust before freeze-thaw cycle can effectively
inhibit the downward migration of Cd2+ under the action of leaching. After the freeze-thaw cycle,the control of the CB
group to Cd2+ decreased. Following more than four years of leaching,the concentration of Cd2+ exceeded the standard limit for
Class Ⅲ water quality as stipulated in the Groundwater Quality Standard. Therefore,it is imperative to establish a long-term
monitoring system.