银北地区土壤盐渍化形成机理与模拟研究

Simulation model for soil salinization in the northern region of the Yinchuan Plain

银北地区位于干旱、半干旱气候带,降水稀少,蒸发强烈,导致本地区土壤盐渍化严重。近年来,由于黄河来水量的逐年减少,引黄灌溉不能满足农业灌溉需求,逐渐开始开采利用地下水。由于银北地区浅层地下水矿化度较高,利用地下水灌溉可能引起次生土壤盐渍化。本文运用PHREEQC模型软件模拟灌溉水与土壤之间的相互作用过程,探讨了土壤盐渍化的形成机理。通过模拟分析得到以下结论：（1）地表水和地下水联合运用是解决银北灌区土壤盐渍化的关键,不同地区采取不同的混合比例,可以实现水资源的高效利用。（2）银北地区灌溉淋洗期间存在蒸发浓缩叠代在2-4次,说明存在轻微蒸发。（3）INVERSE模拟结果说明,银北地区灌溉淋洗期间存在轻微蒸发,水相和固相的相互作用,石膏、白云岩和盐岩溶解,Na^＋、Ca^2＋和Mg^2＋吸附交换,渠水下渗转化为地下水;非灌水期地下水通过毛细管作用强烈蒸发,水相和固相的相互作用,石膏、白云岩和盐岩沉淀,Na^＋、Ca^2＋和Mg^2＋解吸附,使有害盐分氯化物、硫酸盐存留在土壤层中,形成土壤盐渍化。

Soil salinization is extremely serious in the northern Yinchuan Plain of Ningxia since it is in an arid environment. Recently, shallow groundwater is used for agricultural irrigation because the runoff of the Yellow River water decreases from year to year. However, the utilization of groundwater may accelerate the process of soil salinization. In this paper, simulation model for soil salinization analysis is developed by using the PHREEQC software. The geo-chemistry processes of irrigation water and soil interaction are analyzed to understand the principle of soil salinization under various conditions of water resources development and utilization in the plain.