2.1 Soil and NaCl solution
The soil used in this study was collected near a coastal area in Tianjin, China. After the air drying of the soils, the blocks were crushed and then screened by 1-mm sieve and mixed uniformly afterwards before the experiment. And 10 g/L NaCl (99.5%, Tianjin Yuanli chemical co. LTD, China) solution was prepared with deionized water to simulate groundwater.
Table 1 Physico - chemical properties of the soil