The nitrogen cycle is very important for maintaining ecosystems on Earth.

Liquid nitrogen is very cold, so care must be taken when handling it.

The air in this area is greatly affected by pollutants emitted from factories.

This polluted water could potentially harm our health.

Soil pollution in this area has become serious due to years of industrial activity.

Chemical pollution has a serious impact on the health of the Earth.

Marine pollution is a global issue, and all countries should cooperate to find a solution.

We should seriously address the issue of water pollution.

Genetic contamination may have serious impacts on biodiversity in the natural world.

This area is affected by multiple contamination.