Explanation:

- Bioremediation is an environmentally-friendly technology that uses microorganisms or plants to detoxify and restore polluted environments.

- Option 1: Global warming - Bioremediation is not directly used to control global warming.

- Option 2: Melting of glaciers - Bioremediation does not address glacier melting.

- Option 3: Ozone depletion - Bioremediation is not used for fixing or preventing ozone layer depletion.

- Option 4: Heavy metal pollutions - Correct. Bioremediation is extensively used to address heavy metal pollution, employing organisms that can absorb, concentrate, or transform heavy metals into less harmful forms.