The researchers studied how salt levels in soil change in coastal wetlands in Tianjin. They looked at four different wetlands at varying distances from the sea. They found that salt content in the soil decreased as you moved further inland. The type of ions in the soil also changed with distance, with sodium being the main ion closer to the sea and calcium becoming more dominant further inland. The soil in the wetlands closer to the sea was weakly alkaline, while those further inland were mildly alkaline.