海藻多糖抗蚀剂对土壤抗剪与入渗特性的影响

施用土壤抗蚀剂是提升土壤流失治理效果的有效途径之一，现有材料生态效益不能满足耕地的使用需求，寻找生态效益优良的新型土壤抗蚀材料是目前的研究热点与关键。该研究以土壤内源性多糖为基材制得的土壤抗蚀材料为对象，通过直剪试验、土壤崩解试验与变水头入渗试验分析施用量、养护时间对土壤抗剪、入渗等特性的影响，以探讨其防治耕地水土流失的潜质。试验结果表明，海藻多糖抗蚀剂可以在较大程度上提升土壤内聚力，在相同养护时间下，土壤内聚力与其施用浓度呈正相关，在施用浓度1%时4种养护时间下平均提升3.33倍；在同一施用浓度下，土壤内聚力随养护时间延长而增加，短时养护就能取得较好效果。施用浓度与养护时间对内摩擦角的影响较小，施用海藻多糖抗蚀剂后内摩擦角仅小幅增加。土壤抗崩解性随施用浓度的增加而增加，少量施用就能取得良好效果，在施用浓度0.25%时，土壤崩解系数减少66.1%，当施用浓度达到1%时，试验条件下没有崩解发生。渗透系数随施用浓度增加先增加后减小，于0.25%时达到最大值2.86×10-5 cm/s，于1%时达到最小值0.91×10-5 cm/s，都属中等透水层。对固土机理进行了探讨，并通过扫描电镜测试进行验证，结果表明海藻多糖抗蚀剂可通过土壤孔隙渗透扩散到土体内部，包裹土壤颗粒，进而利用自聚交联、凝胶固结在土壤表面和孔隙形成网状膜结构，增强土壤颗粒间的连接，提升土体强度，可拓宽坡耕地土壤侵蚀防治材料的选择范围。

Effects of seaweed polysaccharide-based materials on shear strength and permeability characteristics of soils

Abstract: Soil fertility decline is caused by loss of fertile top soil due to water or wind erosion. The decreasing of cultivated land may be caused by urbanization, industrialization, land abuse, soil pollution, salinization and improper agricultural cultivation. The deterioration of soil in the cultivated land has posed a serious threat on the productivity of the land and the food security. The control of soil erosion in the cultivated land is strongly related to the agricultural, environmental, economic and social concerns. New technologies are highly demanding to develop for the control of soil erosion in cultivated land. In the present, chemical measures represented by soil anti-erosion material are the focus of current research. However, the ecological benefits of previous materials are not enough to meet the requirements in the environmentally sensitive areas, such as cultivated land. Seeking new feasible materials with excellent soil anti-erosion and ecological benefits has become the great issue in the key investigation of soil anti-erosion materials. As endogenous substances in soil, the soil polysaccharides have excellent ecological benefits, indicating perfect needs of cultivated land. In this study, a novel kind of soil polysaccharide-based material was added into the soil, thereby to investigate the influence on soil strength and water cycle, with emphasis on its application possibility to prevent and control soil erosion in the sloping farmland. The material was also cheap easy to be industrial produced. The direct shear, disintegration, and permeability tests were selected to explore the relationship between addition amount, curing age, shear strength, permeability, and anti-disintegration effect in soil. The results indicated that the material can be used to enhance the cohesion, indicating that the cohesion was positively correlated with the amount of material addition under the same curing time. The cohesion of 1% concentration treated group was average 3.33 times of control group under four kinds of curing age. At the same addition amount, the cohesion increased with the curing age, where the increase was mainly distributed in the early stage of curing. The internal friction angle increased slightly after the application of materials under different addition amount and curing time, where the increasing of internal friction angle ranged between 5.42% to 7.29%. The anti-disintegration effect was improved with the increase of addition amount, indicating that a small amount addition can achieve excellent performance. The disintegration rate of 0.25% concentration treated group decreased 66% of control group after 1-hour curing, and the 1% concentration treated group had no disintegration during 30 min test. The permeability of soil samples first increased and then decreased, with the increasing of material application concentration. The permeability coefficient of soil samples was achieved the maximum at 0.25% concentration treated group (2.86×10-5 cm/s), the minimum at 1% concentration treated group (0.91×10-5 cm/s). All the samples belonged to the medium permeable layer, where to ensure the exchange of water and air for the crop growth. Furthermore, all the experiments demonstrated that the short-term and simple curing can be used to achieve excellent anti-corrosion effect after the application of materials, while, the easy application suitable for the sloping farmland. The Scanning Electron Microscopy (SEM) images showed the materials can form the hydrogel on soil particles surfaces and pores, indicating that the materials can wrap the soil particles in the form of a hydrogel network structure, thereby to enhance resistance to soil corrosion.