The migration of total dissolved solids during natural freezing process in Ulansuhai Lake

 High total dissolved solids (TDS) content is one of the most important pollution contributors in lakes in arid and semiarid areas. Ulansuhai Lake, located in Urad Qianqi, Inner Mongolia, China, was selected as the object of study. Temperatures and TDS contents of both ice and under-ice water were collected together with corresponding ice thickness. TDS profiles were drawn to show the distribution of TDS and to describe TDS migration. The results showed that about 80% (that is 3.602×108 kg) of TDS migrated from ice to water during the whole growth period of ice. Within ice layer, TDS migration only occurred during initial ice-on period, and then per-ished. The TDS in ice decreased with increasing ice thickness, following a negative exponential-like trend. Within under-ice water, the TDS migrated from ice-water interface to the entire water column under the effect of concentration gradient until the water TDS content was uniform. In winter, 6.044×107 kg (16.78% of total TDS) TDS migrated from water to sediment, which indicated that winter is the best time for dredging sediment. The migration effect gives rise to TDS concentration in under-ice water and sediment that is likely to affect ecosystem and water quality of the Yellow River. The trend of transfer flux of ice-water and water-sediment interfaces is similar to that of ice growth rate, which reveals that ice growth rate is one of the determinants of TDS migration. The process and mechanism of TDS migration can be referenced by research on other lakes with similar TDS content in cold and arid areas.