Effects of high-TDS on capillary rise of phreatic water in sand soil

Capillary rise is a significant contributor of soil salinity in extremely arid areas and is highly dependent on soil grains and total dissolved solids (TDS) in phreatic water. In this paper, experiments about effects of different grains of sand soil and TDS of phreatic water (1, 30, 100, 250 g/L) on capillary rise were conduced. The results showed that the height of capillary rise was steadily increasing in later stage of experiments and TDS had significant effects on capillary rise. For coarse sand, the higher TDS made the lower height of capillary rise. But for fine sand, the height of capillary rise of 1g/L was obviously larger than others. The sequence of height from lower to larger of capillary rise in silt was 30, 100, 250 and 1g/L. At the beginning of experiments about coarse sand, the higher TDS made the lower velocity of capillary rise, but other soil groups were not. Compared to high-TDS condition, the grain of sand soil was a more primary controlling factor of capillary rise. The research indicates that high-TDS not only changes the gravity of capillary water but also the pore size of soil during the period of capillary rise in fine sand.