Abstract: Freezing-thawing alternation is an important factor affecting the stabilization and remediation of heavy metals in contaminated soils in northern China, but few studies are available at present. In this study, 19 kinds of common heavy metal stabilized materials were used to explore the effects of freeze-thaw alternation on soil physicochemical properties and stabilization of As and Cd with 15 freezing-thawing cycles. The results showed that the stabilized materials increased pH and electric conductivity of compound contaminated soil. The application of six materials, including clay minerals (SL), amendment (MCA, SA2), biochar (MBC, FBC1, FBC2), stabilized 15.0%-32.0% As and 14.0%-33.0% Cd simultaneously, with MCA having the best stabilization effect, followed by MBC. The stabilization effect on As and Cd was significantly affected by freeze-thaw alternation. After 15 cycles of freeze-thaw, the pH of stabilized soil showed a rising trend. Under such environment, biochar (MBC, FBC1, FBC2) addition further reduced the availability of heavy metals in soil. MBC addition increased the stabilization effect on As and Cd by 14.2% and 12.5%, respectively. In general, biochar (MBC) befits the remediation of As and Cd contaminated soil in the cold northern China.

Key words: soil, freeze-thaw alternation, remediation effect, cadmium, arsenic.