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.

Nutrient status and pollution levels in five areas around a manganese mine in southern China

Nutrient status and pollution levels are the main factors affecting soil restoration.The nutrient status and pollution levels in five areas,an unexplored mine area(UA),an explored mine area(EA),a tailings area(TA),a reclamation area(RA)and an agricultural area(AA),around the Pingle manganese mine in Guangxi,China,were assessed in this study.The results showed that the average total phosphorus in these five areas ranged from 1.05 to 1.57 mg/kg,corresponding to grades of extremely high and high.The average total nitrogen values were 0.19,0.69,0.93,1.24 and 1.67 mg/kg in EA,TA,RA,UA and AA,corresponding to grades of very low,low,medium-low,medium-high and medium-high,respectively.The average organic matter values were 12.78,8.92,22.77,21.29 and 29.11 mg/kg in EA,TA,RA,UA and AA,which corresponded to grades of medium-low,low,medium-high,medium-high and medium-high,respectively.All these results indicated that the total phosphorus was sufficient in these areas,while the total nitrogen and organic matter were insufficient in EA,TA and RA.The available concentrations of Mn and Zn corresponded to the intermediate grade,while the values for Cu corresponded to the very low grade;these might be another factor restricting ecological reclamation.Contamination and ecological risk assessments based on the single contamination index,Nemerow multi-factor index and potential ecological risk index showed that the five tested areas around the Mn mine were considered heavily polluted and presented high ecological risk.Mn and Cd were the dominant pollutants.