Common pollutants and effects
The following substances are just some of the substances that have negative impacts on the environment. They affect the plants and animals that live in our streams, beaches and Lake Pupuke. Environmental effects include the removal of oxygen from the water, water discolouration and smothering of habitat. Find out how each substance damages the environment by using the links below.
Cement and concrete
Chlorine and other cleaning agents - including “bio-degradable” or “environmentally friendly” products.
Corrosives
Fuels and solvents
Food and drink
Heavy metals
New and used oil
Nutrients
Paint, ink and dye
Sediment
Cement and concrete
The lime found in cement and concrete products easily dissolves in water, just like sugar. Lime is alkaline, so as a result concrete slurry and any water that comes into contact with cement or concrete becomes strongly alkaline (pH11-13). This is deadly to aquatic life.
Plants, insects and animals can be burnt or killed by high pH water. High pH substances such as slurry or concrete washwater will attack the sensitive membranes of fish and eels, including the gills and the skin, effectively burning them much the same way acid burns us.
Often fish and eels try to jump out of the stream to escape the burning water resulting in death by suffocation. Thirty per cent of all the fish kills reported in Auckland streams are due to cement and concrete wastewater.
All life in a stream can be wiped out by a concrete or cement slurry or washwater discharge, and will take years to fully recover.
Photo gallery of concrete pollution
Chlorine and other cleaning agents
Chlorine (used in treatment of drinking water and in pool chemicals) and cleaning agents such as detergents, degreasers and disinfectants, can cause significant changes to aquatic habitats including:
- Destroying the sensitive membranes of fish, making them susceptible to bacteria and parasites.
- Lowering the surface tension of the water, making it easier for harmful chemicals to be absorbed by fish.
- Depositing extra phosphate and nitrates in the water, which encourages plant growth. When the plants die, bacteria breaking down the plants remove oxygen from the water, making it difficult for other plants and animals to survive.
Fragrances in cleaning agents can cause long-term damage to aquatic life by interfering with animals' natural ability to eliminate toxins from their system.
Washwater used to wash machinery and other items contains cleaning agents and also dirt, oil, fuel residues, metals and paint washed from the surface. The biochemical process that breaks down washwater in the environment uses up oxygen in the water, so plants and animals living there cannot breathe. On average, one litre of washwater needs the oxygen from 70 litres of stream, lake or seawater to break down completely.
Biodegradable or “environmentally friendly” products break down faster than standard cleaning agents but this does not make them better for the environment. As they break down they will cause rapid oxygen depletion and result in the death of plants and animals, just as standard cleaning agents would over a long period.
Photo gallery of detergent pollution
Nutrients
Corrosives
Corrosives refer to substances such as battery acid, vinegar, some cleaning agents and cement wastes.
When corrosives enter a waterway they change the pH (acidity/alkalinity) of the water by either increasing or decreasing the pH depending on the corrosive. Levels of pH between 1 – 5 (acid) and 9-14 (alkaline) can drastically harm aquatic life by killing or burning fish, plants and insects.
Corrosives damage the sensitive tissues of fish such as eyes, gills and skin, making it difficult for animals to see, eat food and swim effectively.
Fuels (e.g. petrol and diesel) and solvents (e.g. nail polish remover, turpentine and degreasers) are devastating if they are allowed to enter an aquatic environment or contaminate land.
These substances can poison and burn aquatic life. Some chemicals found in fuels and solvents dissolve in water and can build up in the bodies of plants and animals, causing long-term health effects.
Land that has been contaminated with fuels or solvents generally requires the soil to be removed and disposed of through a registered waste contractor. If contaminated soil is left in place, the groundwater below may also become contaminated.
Although food products are safe for humans, in an aquatic environment they can be disastrous.
When food and drink begin to break down, oxygen is taken out of the water and will result in suffocation of the plants and animals that live there. When oxygen is taken out of the water, the water becomes black and smells a little like sulphur. Once food products enter a waterway they can be difficult and costly to remove.
Heavy metals
Heavy metals is a general term given to metallic elements such as zinc, copper, nickel, lead, mercury and aluminium.
When heavy metals are discharged into the environment they can become ‘locked-up’ in the stream sediments where they can remain for long periods of time. As they do not break down, they continue to cause ongoing problems in the environment, destroying aquatic life.
Heavy metals can poison plants and animals, causing downstream effects on species that rely on them for food or habitat. Life cycles can be altered resulting in entire generations being lost.
New or used oil can partially dissolve in water, introducing toxic substances into the environment. These include heavy metals and hydrocarbon compounds that are a by-product of vehicle operation. Impacts on a waterway include:
- Poisoning animals and plants. Some chemicals found in oil dissolve in water and can build up in the bodies of plants and animals, potentially causing long-term health effects
- Forming a layer or film on the surface of water and preventing oxygen and sunlight from entering the water. This makes it difficult for animals to breathe and find food, and for plants to get energy through photosynthesis
- Contaminating the land and underlying groundwater.
Just one discharge of a very small quantity of oil product can drastically alter the quality of a stream, lake or beach. Fish, insects and plant life can be killed, habitats destroyed, with a stream taking up to 10 years to recover.
Photo gallery of oil pollution
Heavy metals section
Nutrients such as nitrogen and phosphorus are elements that are considered essential to supporting life. In healthy water environments, these two nutrients are present in small amounts and aid plant growth. However, excess nutrients (or nutrient loading) can cause algae blooms (20 per cent of which can be toxic to humans) and rapidly increased plant growth, disturbing the natural balance of the stream.
When this high number of plants and algae blooms die and begin to decompose, large amounts of bacteria are needed to break down the plants/algae. These bacteria take the oxygen out of the water, making it impossible for fish and other plant and animal species to survive. Excess nutrients can start a chain reaction that has very serious downstream effects. Life cycles can be altered and entire generations can be lost.
When oxygen is taken out of the water, the water becomes black and smells a little like sulphur. In calm, hot weather we see this happen at some of our East Coast Bays streams. In these cases seaweed has usually been washed up into the mouth of the stream where it has been trapped by low water flow and the narrowing of the entrance channel, and has decomposed. This decomposition causes deoxygenation of the water, and due to the increased temperatures and low water flow, the stream may be unable to naturally re-oxygenate itself.
Paints, inks and dye contain toxic substances that can pollute our environment. These substances include heavy metals and suspended solids. If they enter a waterway they will cause harm to fish and plant life and can result in the contamination of the food chain. Other effects include:
- Preventing light from entering the water, making it difficult for animals to find food and for plants to get energy through photosynthesis.
- Irritating, clogging or destroying the gills of fish.
- Poisoning animals and plants. Some chemicals found in paints, dyes and inks dissolve in water and can building up in the bodies of plants and animals potentially causing long-term health effects.
- Contaminating soil and groundwater (if paint, ink and dyes are discharged onto land).
- Smothering of small animals and destroying their habitat (if solids enter a waterway).
Photo gallery of paint pollution
Heavy metals section
Sediment (i.e. clay and dirt) is a natural substance, but too much in the wrong place can have a catastrophic impact on our aquatic environment. The effects can be far reaching. Uncontrolled sediment run-off can affect offshore fisheries, enjoyment of our beaches and streams, and can also cause flooding problems.
When clay, silt and sand are washed from building sites or unsealed ground, they often end up in sensitive stream environments causing many problems including:
- Reducing the amount of light entering the water, which is needed by plants and animals to survive. If plants cannot grow then some aquatic animals cannot feed.
- Clogging and damaging sensitive tissues of animals, such as the mouth and gills of fish. If they cannot breathe or feed they will die.
- Starving aquatic animals that are unable to feed, as they cannot see their food through the sediment filled water.
- Suffocating plants and animals that live on or in the bed of streams, the lake and estuaries, by smothering them when the sediment settles out. Even thin layers of sediment can have long-lasting adverse effects.
- Destroying the natural balance of the aquatic habitats and impacting the food chain and life cycles.
Sediment particles often have other pollutants attached e.g. heavy metals such as zinc and copper. When the sediment settles out, these attached pollutants can cause severe long-term health effects in the environment.
Sediment pollution can also occur due to bank or stream erosion, caused by the loss of streamside vegetation or an increase in the amount or speed of water flowing through the stream.
Pollution prevention