Substances in Water from Natural Sources

We use water in many aspects of our everyday life:

• Domestic uses: for drinking, cooking, gardening and general sanitation 

• Agricultural uses: as a drink for animals and watering crops

• Industrial uses: as a solvent, as a coolant and heated to make steam used to generate electricity

Water is found in natural sources such as lakes, rivers and underground water sources (groundwater)

A rock that stores water is known as an aquifer

Water from natural sources may contain a variety of different substances, including:

• Dissolved oxygen

• Metal compounds

• Plastics

• Sewage

• Harmful microbes

• Nitrates from fertilisers

• Phosphates from fertilisers and detergents

Many of these substances enter water sources when rain falls and washes them into lakes, rivers or groundwater

Some of these substances are naturally occurring but many are a direct result of human activities

Some of the substances which may be found in natural water sources are beneficial and others may have harmful effects

Beneficial substances include:

• Dissolved oxygen - essential for aquatic life

• Metal compounds - some provide essential minerals which are necessary for life, such as calcium and magnesium

Potentially harmful substances include:

• Metal compounds - some are toxic like aluminium and lead

• Some plastics - these may be harmful to aquatic life in many ways, e.g. getting trapped in plastic waste, dying of starvation as their stomach is filled with plastic

• Sewage - contains harmful microbes which can cause disease 

• Nitrate & phosphates from fertilisers - these can promote the growth of aquatic plant life which leads to deoxygenation of water. Ultimately, this can cause damage to aquatic life in a process called eutrophication (you do not need to know the details of this process)