土壤中优势流的几个基本问题研究

Study on Foundational Problems on Preferential Flow in Soils

优势流是指土壤在整个入流边界上接受补给,但只通过少部分土体的快速运移。优势流是一种普遍存在的现象,而不是一种特例。它受许多因素的控制,如土壤中的大空隙、土壤结构、土壤质地、土壤水分含量、土壤初始水分含量、水和溶质的施加速率及溶质的施加方法等。优势流的产生机理主要有2 种:一种是由土壤介质的非均质性所驱动的优势流;另一种是由湿润锋的不稳定性所驱动的优势流。目前,优势流的监测方法主要有取土壤原状土、实验室内的土柱出流试验及染色示踪试验。尽管优势流的模拟非常困难,但人们仍提出了许多模型来描述它。今后优势流研究的重点应放在进行大量的综合性野外试验,以获取足够的数据资料来确切地刻划优势流;发展新的观测技术以便在时间和空间上监测优势流;建立新的模型来模拟优势流,从而进一步解决与土壤和地下水污染有关的环境问题。

Preferential flow refers to the rapid transport of water and solute through some small portion of the soil volume which is receiving input over its entire inlet boundary. It is a general phenomena but not exception. Preferential flow is confined to many factors, such as macropore in soil, structure, texture, water content, initial water content, application rate of water and solute as well as application method of solute etc.. There are two mechanisms causing preferential flow: one is heterogeneity driven, another is wetting front instabilities driven. At present, the most reliable methods observing preferential flow are soil coring, soil column effluent experiment and dye tracers. Although it is very difficult to simulate preferential flow, many models were still suggested. The focus of preferential flow research should be put on doing a number of field experiment, so as to obtain enough data to describe preferential flow, developing new observation techniques to monitor preferential flow and suggesting new models to simulate preferential flow. Furthermore, the environmental problems associated with soil and ground water contamination could be solved.