基于短链DNA示踪技术的干旱区灌溉农田水转化过程研究

深刻认识旱区农田灌溉水、土壤水和地下水转化关系，对提高农田水的利用效率，防治土壤次生盐渍化和地下水面源污染具有重要理论和现实意义。传统的水量平衡方法和土壤水动力学方法均基于平移流概念和完全混合理论。然而，近年来研究发现多源水分在土壤孔隙中存在不完全混合的现象，称为“土壤水分流运动”。传统的示踪技术很难提供三种及以上可辩别但在土壤中运移性质相同的示踪剂，且在环境中的背景值时空分布复杂分析时难以完全去除。新兴的人工合成DNA示踪技术提供了辩别不同来源的土壤水分流运动的可能。本研究拟应用新兴DNA示踪技术研究旱区农田水转化过程，探究农田土壤水分流运动现象的发生条件，揭示农田灌溉水-土壤水-地下水转化规律，提出采用不同序列DNA在土壤中的时空和孔隙分布特征表征灌溉入渗和潜水蒸发过程的方法，为研究农田水转化过程提供新的科学手段。本研究对于深入认识农田土壤水分流运动及伴生的水土环境过程具有重要的意义。

In arid irrigated croplands, it is of great theoretical and practical significance to understand the conversion between irrigation water, soil water and groundwater. Because this understanding can greatly improve the utilization efficiency of cropland water and prevent secondary soil salinization and groundwater non-point source pollution. Both the traditional water balance method and the soil water dynamics method are based on the translation flow concept and the well mixing theory. However, in recent years, it was found that water from different sources is not well mixed in the soil pores (referred to as "the separately flowed soil water"). The traditional tracing techniques can hardly provide three or more tracers that can be discerned but have the same transport properties in the soil. And the tracers have complex temporal and spatial background distributions in the environment, which are difficult to completely eliminate in the analysis. The emerging synthetic DNA tracer technique provides the possibility to discern soil water from different sources. This study intends to apply the emerging DNA tracer technique to study the processes of arid cropland water conversion, to explore the occurrence conditions of “the separately flowed soil water” in croplands, and to reveal the irrigation water-soil water-groundwater conversion law. We propose to use the spatial, temporal and pore distribution characteristics of different DNA sequences in the soil to interpret the infiltration and phreatic water evaporation processes. We provide a new scientific method for studying the processes of cropland water conversion. This study is of great significance for understanding the “the separately flowed soil water” in croplands and the associated soil and water environmental processes.