无害化污泥对沙性土即时团聚体稳定性及黏聚力影响的研究

Study on short-term effects of harmless sludge on aggregate stability and soil cohesion of sandy soil

为了解决我国土壤沙化严重以及大量污泥处理处置的问题,研究了不同种类与比例的无害化污泥对沙性土团聚体稳定性及土壤黏聚力的影响。通过将堆肥污泥(CSS)、干化污泥(DSS)、炭化污泥(BSS)分别以质量分数为5%、10%、15%、20%、25%和30%的添加量与沙性土复配,并测定土壤的pH值、电导率、有机质、水稳性大团聚体和抗剪强度,来探究3种无害化污泥对沙性土团聚体稳定性及土壤黏聚力的影响。结果表明:无害化污泥的颗粒粒径分布和保水性为改善沙性土的结构与持水性能提供了有利条件,即随污泥添加量增加,土壤pH值降低,电导率、有机质增加;添加污泥使得水稳性大团聚体含量增加,水稳性来自于稳固的颗粒大小和污泥的团聚作用;添加污泥使得土样黏聚力增加,污泥添加质量分数为30%时,CSS复配土黏聚力为10.97 kPa,改良效果最佳。综上,添加无害化污泥能有效改善沙性土的团聚体稳定性与黏聚力,其中CSS复配土最接近种植土的水平,改良效果显著。无害化污泥的投加比例要根据目标土壤的需求来进行优化,其有效性和对土壤可能造成的其他影响需要通过长期试验来进一步探究。

In previous studies,there was not any systematic comparison among composted sewage sludge(CSS),dried sewage sludge(DSS),and sewage sludge biochar(BSS) derived from the same type of municipal sludge.Therefore,the sandy soil improvement experiment of the three sludge products was carried out to provide a reference for solving the serious problems of soil desertification and the treatment and disposal of a large amount of municipal sludge in our country.CSS,DSS,and BSS were added to the sandy soil at mass ratios of 5%,10%,15%,20%,25%,and 30% respectively.The pH,conductivity,organic matter,water-stable macroaggregates,and shear strength of compound soil samples were determined to explore the effects of three harmless sludges on the stability of sandy soil aggregates and soil cohesion.The results show that the particle size distribution and water retention of the harmless sludge provide favorable conditions for improving the structure and water-holding properties of sandy soil.CSS has a greater impact on soil moisture than DSS and BSS.As the amount of sludge increases,the soil pH decreases,and the conductivity and organic matter increases.Adding sludge increases the content of water-stable large aggregates,and water stability comes from the solid particle size and the agglomeration of sludge.Adding sludge increases the cohesion of the soil samples.When the amount of sludge added is 30%,the value of the cohesive force of CSS compound soil is 10.97 kPa,and the improvement effect is the best.When the amount of sludge is at a relatively high level,the increase in the cohesion value decreases with the growth of the amount of sludge added,which indicates that the improvement effect of sludge does not continue to increase with increasing added amount,and there is a threshold value.In summary,the addition of harmless sludge can effectively improve the stability and cohesion of aggregates in sandy soil.Among them,the CSS compound soil is closest to the level of planting soil,and the improvement effect is remarkable.The dosage of harmless sludge should be determined according to the demand of the target soil.The duration of the effectiveness of harmless sludge on sandy soil improvement and whether it will exert other influences requires further investigation.