Seepage, runoff, and direct discharge are all ways that acids and heavy metals can pollute what?

Seepage refers to the process of something leaking, usually from below ground. It can originate from natural or man-made sources, such as material dripping from a tank crack, or from more natural sources (I think stalactites are a type of seepage, where water filled with minerals slowly seeps into a cavern from above it).

The process by which precipitation travels along the ground and into streams and rivers is known as runoff.

The act of pumping waste water straight into a waterway is known as direct discharge.

Waterways themselves will transport the heavy metals and acids to bodies of water (lakes and oceans), and since all of these bodies of water are sources of water for the animals and plants they touch, they can all become contaminated with the heavy metal and acid materials. All of these various ways that water can run to a waterway (such as a stream or river) can carry heavy metals and acids into those waterways.

Seepage, runoff, and direct discharge are all ways that acids and heavy metals can pollute water bodies, such as rivers, lakes, and oceans.