leach in
To enter (some substance or material) through percolation. Rising seas have allowed high concentrations of salt to leach in across these coastal farmlands. After the spill, acids and other toxins began leaching in on the cliffsides.
leach in (to something)
[for a substance] to seep or penetrate into something. The salt leached into the soil and ruined it. A tremendous amount of salt leached in.