Effect of reclamation projects on the salt ion migration process in the saline-alkali soil of tidal flats

Abstract The estuarine and tidal flat silt-promoting project and enclosure project have increased the land supply, but the soil salinization is serious, and the research on the driving mechanism of soil salinity and nutrients in reclamation projects is relatively few. To understand the migration law and major factors influencing saline-alkali ions in soil after reclamation projects, six reclamation areas on Hengsha Island from 2003 to 2018 were used as research locations, and 55 investigation sites were set up to monitor and analyze the saline-alkali ions and physical and chemical indexes in soil and water. The results showed that the reclamation areas in the Yangtze River estuary were all chloride-type saline alkali areas. Among them, the saline-alkali ions in the soil in the reclamation area were significantly higher than those in the old reclamation area within five years. Na+, K+ and Cl- were higher in areas with low moisture content, while Ca2+, SO42- and HCO3- were higher in soil with vegetation. The soil salt ions and physical and chemical indexes in the reclamation area appeared stratified. Correlation analysis showed that organic matter, moisture content and phosphorus were the major factors affecting soil salt ions and pH in the reclamation area.