Utilization of recycled solid waste as ecological reclamation materials based on plant growth experiments and soil quality analysis

During the highway construction, a large number of spoil areas will be generated while a large amount of waste slag and soil could not be rationally utilized. Besides, the vegetation recovery is slow in the spoil areas due to the soil depletion. Aiming at recycling the solid waste, the sieved engineering waste slag with local red clay and corn straw biochar was supplied to solve the problem of insufficient nutrients in engineering waste slag and soil. In addition, planting experiments of alfalfa (Medicago sativa L.) and Amorpha fruticosa L. combined with physical and chemical experiments were carried out to prove the feasibility of the novel improved substrate for the reclamation of spoil areas. The results show that the substrate's improvement effect is mainly affected by the soil to slag ratio and the biochar content. The improvement effect of soil matrix in highway spoil area decreases with the increase of the waste slag content, especially when the soil-slag ratio is less than 3, and the promotion of plants is limited. On the contrary, the improvement effect is proportional to the biochar content (3%-8%). But it is noted that the Cu and Pb in the soil will exceed the clean limit corresponding to the Nemero soil pollution index level when the biochar content is 8%. Therefore, it is recommended that the soil-slag ratio should be ≥3, and the biochar content should reach 3%-5%. This research provides experimental basis and technical support for utilizing solid waste resources in the reclamation of highway spoil areas.