Changes of Salinity and Alkaline in the Coastal Heavy Viscosity Saline Soil in Leaching Processes over the Bohai Bay Coast

In order to obtain characteristics of coastal heavily saline soil in leaching processes under controlled conditions, a method of soil column was adopted in the study. Different amount of water was used in the soil column experiment to leach salt from the saline soil. For increasing the experiment efficiency and simulating the outdoor soil structure, the experiment was carried out under the conditions of air-drying and absence of crushing of soil. Certain reeds were put into the saline soil to make the density of the experimental soil similar to that of the outdoor soil, which could make water horizontally go through the soil columns to accelerate the experimental processes. The experiments on indoor imitating processes of soil column leaching for desaltification were conducted on heavily saline soil over the west of the Bohai Bay coast. The results showed that in the leaching process, with decreases in soil salinity, the amount of Na+ and Cl-, the primary contents of the soil salt, would decrease during the whole process whereas the amount of K+, Ca2+, Mg2+ and SO42-, the subordinate contents of the soil salinity, would decrease with increases in the amount of leaching water due to the initial concentration of salt ions and varied migration ability. However, their amount would be steady when the quality of the leaching water approached the quality of the soil. The amount of HCO3-would increase slowly with increases in the amount of the leaching water. With the migration of soil salt ions, the soil pH values would increase progressively. The pH values would increase from 8.50 initially to 9.86 when the soil salinity decreased to 1.6g/kg. The pH values of the soil would decrease slowly when the soil salinity reduced to 1g/kg. The study showed that soil alkalization could be caused by desalination when the saline soil was ameliorated to certain degree. As such, measures should be taken to decrease the soil alkalization and the amount of the leaching water should be controlled as well. The leaching water was found to be a leading factor affecting soil alkalization. Due to the lack of groundwater in the east of Hebei province near the Bohai Bay, water from deep wells have become a primary water source for drinking and irrigation. The deep groundwater is generally considered high in alkaline and contains higher amount of fluoride; hence the long-term utilization of groundwater for drinking and irrigation would result in a series of adverse effects on the health of people and soil. It is suggested that utilization of sea ice water be a promising alternative to substitute groundwater in the future because of its neutral quality, low fluoride and huge amount.