【作者】 陈俊英；

【导师】 汪志农；

【作者基本信息】 西北农林科技大学 ， 农业水土工程， 2010， 博士

【摘要】 水资源是人类社会生存和发展中不可替代的重要战略性资源,但水资源短缺已经成为21世纪全世界的最大危机,人口的增加和国民经济的发展,加剧了水资源短缺,农业用水矛盾日益突出,干旱缺水成为制约农业发展的主要因素之一。因此人类走资源节约型的节水发展道路刻不容缓。在农业方面,将污水再生回用灌溉是一个有效的途径,目前,在美国、澳大利亚、以色列、俄罗斯等国已经有很多成功经验,但是污水回用灌溉的同时也会带来新问题的产生,其中土壤产生斥水性是主要的不良影响之一。土壤斥水性是指水分不能或很难湿润土壤颗粒表面的物理现象,具有斥水性的土壤称为斥水性土壤。斥水性土壤很容易形成优先流,导致土壤持水能力降低,土壤水分分布不均匀,使水中携带的溶质更快地进入地下水,导致种子不能发芽,影响农作物生长,使得农作物减产,不利于农业生产和水土环境的可持续利用与发展。因此,本文在综合分析国内外研究成果的基础上,通过室内、田间试验及其分析,较为系统地研究了土壤含水量、有机质含量、不同灌溉水质,以及烘干温度和时间等因素对污灌土壤斥水性机理方面的影响,得出以下主要结论:(1)土壤斥水持续时间随土壤含水量的变化关系符合Lorentzian模型。本文选用3种类型土壤10种不同斥水性的土壤样品,测定这些土壤在不同含水量下的斥水性持续时间,得到了不同土壤斥水持续时间随含水量变化的规律,通过Gaussian模型、Lorentzian模型和Lognormal模型对这种规律进行回归分析,最终得出了土壤斥水持续时间随含水量的变化规律符合Lorentzian模型。(2)粘性土、壤土的斥水持续时间与生活污水水质呈显著线性正相关关系,砂质土斥水持续时间与生活污水水质无显著关系。本文选用和配置不同污染程度的生活污水12种,化验其主要水质指标值,并用这些水测定不同斥水性的土壤,再分析不同水质与5种土壤的斥水持续时间的关系,得出了不同污染程度的生活污水用于测定土壤斥水性时,粘性土和壤土的斥水持续时间与生活污水水质呈显著线性正相关关系,其中,化学需氧量(COD)是影响土壤斥水持续时间的最主要因素;但砂质土斥水持续时间与生活污水水质无显著关系。(3)粘性土斥水持续时间与有机质含量呈线性正相关关系,砂质土和壤土斥水持续时间与有机质含量呈单峰曲线关系。本文采用3种土壤即粘性土、壤土和砂质土,在田间实测其土壤斥水持续时间,并测得其土壤含水量和有机质含量,绘制斥水持续时间与有机质含量和含水量的等值线图;同时在室内,对粘性土和砂质土采用25°C和65°C烘干处理后,测定其斥水持续时间,绘制斥水持续时间与有机质含量关系图。经试验结果分析得出,不同的土壤,斥水持续时间随有机质含量的变化是不同的,对于粘性土斥水持续时间与有机质含量呈线性正相关关系,对于砂质土和壤土斥水持续时间与有机质含量呈单峰曲线关系。(4)对物理方法消除斥水性的土壤进行污灌时,土壤斥水性重现与灌溉时长和水质呈显著正相关关系。本文针对以物理方法消除斥水性的土壤进行污水灌溉后,土壤斥水性是否会很快重现的问题,采用自来水和3种不同生活污水,对壤土进行滴灌,在灌溉4个月和8个月后分别进行了斥水持续时间的测定及其差异显著性分析。得出对于用物理方法消除斥水性的土壤,其土壤斥水性会在灌溉一段时间后重新出现,并且与灌溉时长和水质呈显著正相关关系。(5)测定土壤潜在斥水性的最佳烘干温度为45℃~65℃,最佳烘干时间为24小时。本文对2种粘性土和2种砂质土在测定潜在斥水性时,采用4种不同烘干温度和6种不同烘干时间的组合进行处理,比较不同处理对潜在土壤斥水持续时间测定结果的差异,得出了对潜在土壤斥水持续时间测定结果无显著差异影响的最佳烘干温度为45℃~65℃,最佳烘干时间为24小时。通过以上的研究,可对污灌引起土壤斥水性的成因、特性及规律有更深入的认识,为进一步防范、改进和减小污灌引起土壤斥水性问题及改良措施提供科学的理论依据。本文主要创新点为:(1)提出了土壤斥水持续时间随土壤含水量的变化关系符合Lorentzian函数模型;(2)得出了污水的化学需氧量(COD)是影响土壤斥水性大小的主要指标;土壤斥水性是一个非常复杂的问题,本论文从机理上研究了污灌土壤斥水性的影响因素,但对于结果如何在实际中应用,以及有机质含量如何影响斥水性、不同水质的其他灌水方法对土壤斥水性的影响、同一种土壤在不同初始含水量的情况下烘干温度及时间对斥水性的影响、以及其他类型土壤的含水量与斥水持续时间的关系等,还有待进一步研究。更多还原

【Abstract】 Water recourses are one of the most important strategic resources in human being’s life. But the shortage of water resources is the serious crisis in 21 century. Since the population is becoming much larger and economy develops much faster than before, the shortage of water resources has become even more serious. And the contradiction of water resources and water requirements in agriculture become more aggravated. The shortage of water resources is one factor that restricts the development of agriculture. So the economic water saving for human beings is no time to delay. The treated waste water for agriculture irrigation was used to solve the problem. It is an effective action taken successfully in America, Australia, Israel and Russian. However, another new problem of water repellency occurs after using waste water for irrigation is implemented.Soil water repellency is defined as the situation that the soil is not wet spontaneously when water is applied. That kind of soil is named as water repellent soil. The main impacts of soil water repellency are easy to development of finger flow in structural or textural preferential flow paths. Finger flow can lead to significant variations of the soil water content in the soil profile, reduce the infiltration capacity, resulting in poor seed germination, plant growth and yield, accelerating the agrochemicals and salts leaching. Soil repellency has some disadvantages of the sustainable development for agriculture and its environment. Therefore after analyzing the result of all researches and the affecting factors of soil water repellency, this thesis got some results after doing mechanism researches such as soil moisture, organic matter, different types of irrigation water and different drying temperature and time etc. on water repellency of sewage irrigated soil. The results of this thesis are as follows:(1)The relationship between Water Drop Penetration Time (WDPT) and soil moisture accords Lorentzian model.The present research work studied the relationships between the soil water repellency and soil moisture by measuring WDPT using 10 different water repellent soils collected from Israel. Three mathematic models, namely Gaussian, Lorentzian and lognormal distributions, which were used for fitting the models by regression analysis, and the Lorentzian distribution was found to be the best model for the practical use. (2)The relationship between WDPT and the quality of domestic sewage is positive linear correlation for clay and loam, but there is no significant relationship for sandy soils.The present study investigated the effects of twelve different types of water with different contaminated levels on soil water repellency by measuring WDPT using of the twelve types of water on two clay soils and one loam and two sandy soils collected from Israel. The main affected parameters of the water quality were released by using principal component analysis. The results showed a positive linear relationship between soil water repellency and the integrated water quality value (F) for clay soils The multiple regression analysis exhibited that organic matter expressed as COD is the main factor affecting the soil water repellency. But there is no significant difference among the twelve types of water for sandy soil.(3)The relationship between WDPT and soil organic matter is positive linear correlation for clay, and a single peak curve correlation for sandy soil and loam.This thesis got the contour of WPDT for three kinds of soils namely clay, loam and sandy soil, by measured WDPT in the field and soil moisture and organic matter in the lab. Meanwhile the relationship between WDPT and soil organic matter was got by measuring WDPT after drying soil samples in 25°C and 65°C for clay and sandy soil in the lab. The relationship between WDPT and organic matter shows difference between soils. It is a positive linear correlation for clay, and a single peak curve correlation for sandy soil and loam.(4)The relationship between the reappearance of water repellency for soil which water repellency was eliminated by the physical method and the quality of irrigation water and irrigation is positive.This paper mainly discussed whether soil water repellency will reappear or not shortly after the soil is irrigated with sewage, which the water-repellency soil is eliminated by the physical method. Drip irrigation is adapted for the water-repellency soil with tap water and other three domestic wastewaters. The significance of WDPT was checked after irrigated in 4 and 8 months. The result shows that soil water repellency will appear again after drip irrigation at a certain intervals. Meanwhile, it has a significant positive correlation between irrigation time and water quality.(5)The optimal temperature is 45℃~65℃and the time is 24 hours for measuring potential water repellency.This thesis concerns how to get potential water repellency after drying in four temperatures and six times in the oven for two clay and two sandy soils. The result shows that the optimal temperature is 45℃~65℃and the time is 24 hours for measuring potential water repellency after analyzing the different WDPT among the treatment for each soils.After doing the research, the soil water repellency which caused by sewage irrigation and its character and regulation will be further understood. It will offer the scientific theory for avoiding and ameliorating and reducing soil water repellency caused by sewage irrigation.The innovative points of this paper are proposing that the Lorentzian distribution was the best one to describe the relationship between WDPT and soil moisture. Chemical oxygen demand (COD) is the main factor which affects the soil water repellency when using different kinds of contaminated water to measure the WDPT.Water repellency is too complex. So this thesis only studies mechanism on water repellency of sewage irrigated soil. The further researches include how to use the theory to practice, the effects on the soil water repellency by the soil organic matter, other irrigation with different water, different temperature and time for the same soil with different initial soil moisture drying in the oven, and the relationship between soil moisture and WDPT of other type soil.更多还原