I always understood it as: if a substance is dissolved into solution, and carried away by water/the solution (say nitrate fertiliser from a farmland, dissolved in rainwater, and carried to a nearby lake causing eutrophication).
However when googling leaching, it comes back with a definition involving infiltration (so leaching is rather when a substance is infiltrated).
So my question is, does leaching HAVE to involve the substance being infiltrated?
This is for A2 environmental studies
What do you think?