A leaking underground storage tank or wastewater pouring into a river from a pipe would be examples of

Water pollution.

Explanation:

This is because water pollution refers to the release or disposal of harmful substances called contaminants which contaminate water bodies which include rivers, oceans, lakes e.t.c.. These harmful substances affect aquatic organisms and make water unfit for good use. This can lead to the death if aquatic lives in the water bodies, release of bad smells and make the water bad . A leaking underground storage tank or wastewater pouring into a river from a pipe can be a source of water pollution.

1. they vary with a higher number because boiling is way hotter than melting