高矿化度土壤水分特征曲线及拟合模型适宜性

Soil-water characteristic curves of high-TDS and suitability of fitting models

为分析高矿化度对土壤水分特征曲线的影响,以淡水及矿化度分别为30、100和250g/L的水样对土体进行饱水处理(简称TDS-F、TDS-30、TDS-100和TDS-250处理),测定脱湿过程的土壤水分特征曲线。结果显示,试验吸力变化过程中,各处理比水容量相近,局部存在差异:TDS-100及TDS-250处理土体对水分的吸持能力明显小于TDS-30及TDS-F处理。分析表明:TDS-30处理使土体中等孔隙体积变小、TDS-100处理使土体较小孔隙体积变小、TDS-250处理使土体较大孔隙体积变小,进而影响土壤水分特征曲线形态。利用RETC软件结合统计分析确定,TDS-F、TDS-30、TDS-100及TDS-250处理土壤水分特征曲线的最优拟合模型分别为:vanGenuchten-Mualem、Dual-porosity-Mualem、Lognormaldistribution-Mualem及Dual-porosity-Mualem模型;各处理最优模型的非饱和导水率模式均为Mualem模型;从机理上解释各拟合模型优劣还较为困难。研究结果为干旱区高矿化度土壤水、盐运移计算提供一定参考。

Four soil treatments with different TDS water（freshwater,30,100 and 250 g/L） were prepared and their soil-water characteristic curves of drying processes were obtained based on the measured soil water content and soil hydraulic pressure.The results showed that the specific water capacities of these treatments was similar in the whole drying process with partly different.However,compared with the freshwater and the water with TDS of 30 g/L,scenarios of the higher TDS（100 and 250 g/L） water possessed a remarkably weaker ability of the water retention.Further analysis indicated that four scenarios had different soil-water characteristic curves in the different TDS background.During the variation of soil suction of the four treatments,which ranged from 0 to 1 00 kPa water column,median pore size of soil dealt by 30 g/L-water,small pore size of soil dealt by 100 g/L-water and large pore size of soil dealt by 250 g/L-water diminished.RETC software and mathematical statistics method were adopted for getting the optimum model that described soil-water characteristic curves of the four dealt soils.For the treatments with freshwater,30 g/L-water,100 g/L-water and 250 g/L-water,the optimum models were van Genuchten-Mualem model,Dual-porosity-Mualem model,Log normal distribution-Mualem model and Dual-porosity-Mualem model,respectively,and Mualem model was the best one to describe the unsaturated hydraulic conductivity of the all soils.On the other hand,it’s difficult to explain the inherent mechanism of the best model for different TDS.The research results are useful for analysis of soil water and salt transport under high-TDS condition in arid areas.