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How does contaminated land affect our environment?

Land can be contaminated by a number of substances, each of which comes with their own dangers and long-term consequences. Here at Drain Depot we provide advice on how to carry out drainage projects safely with protecting the environment in mind, which is why in this blog we delve deeper into how contaminated land effects our environment.

Remember, when undergoing any type of drainage project it is your responsibility to make sure you don’t adversely affect the environment around you, so if you are ever unsure make sure you contact your local authority or environment agency before starting any work.

Contaminated Land in General Terms

Firstly, it’s good to know what the term “contaminated land” means so that you can make sure your work is in-line with government regulations. Essentially, contaminated land is an area of land that has historically been used for industrial purposes and as a result has been polluted with one of the following substances:

• Heavy metals e.g. arsenic, cadmium and lead
• Oils and tars
• Chemical substances and preparations e.g. solvents
• Gases
• Asbestos
• Radioactive substances

Contaminated land – a legal definition

Contaminated land is legally defined as land where substances could cause:

• Significant harm to people or protected species
• Significant pollution of surface waters or groundwater

Effects of contaminated land on building land availability

Unless treated, contaminated land takes land out of circulation meaning there is less to be developed upon. Given the UK government’s current targets for brownfield site development, this means we must clean up our contaminated land so that we can continue to develop these sites rather than greenfield sites. The effect on the environment here is that if we were to continue to develop on greenfileld sites we would be destroying many established green areas, including plants and trees along with many creatures’ natural habitats. On the other hand, if contaminated brownfield sites are treated suitably they can then be reused without causing an environmental impact.

Water pollution and the effect on humans

In some areas of the UK people could potentially be getting their water from rivers which have been supplied by contaminated groundwater. Illnesses such as cancer develop over long periods of time and for many reasons, which means it’s still very difficult to prove these diseases have been caused by pollution. No one knows how much land has been contaminated and the levels vary hugely from one location to another, so the scale of the issue and its effects are impossible to determine on human health.

Water pollution and the effect on marine life

Water pollution can also occur from land run-off: this is when rainwater falls onto the land and due to the volume that has fallen, eventually has nowhere to go but the sea. This water often picks up contaminates from the land in the form of petrol, oils, fertilizers and pesticides. These run-offs enter the ocean at consistent places and can create “dead zones” where no marine life or living corals can survive. Oil leaked into the ocean from contaminated land is dangerous to marine life in several ways; for example it can get onto the gills or feathers of marine animals, making it difficult for them to move, fly or feed their young. The long term effects on marine life can include cancer, failure of the reproductive systems, behavioral changes, and even death. Industrial and agricultural wastes include various poisonous chemicals that are considered hazardous for marine life. Chemicals from pesticides can accumulate in the fatty tissue of animals, leading to failure in their reproductive systems.

Benefits of woodlands on contaminated land

‘Phytoremediation’ and ‘phytostabilisation’ (literally meaning "plants restoring balance"), describes the treatment of environmental problems through the use of plants that mitigate an environmental problem without the need to excavate contaminated material and dispose of it elsewhere. Conventional ‘clean-up’ methods generally involve the removal of contaminated soil but are very expensive. Phytoremediation and phytostabilisation using trees are comparatively inexpensive and do not rely on the removal of contaminated material to other sites. Furthermore, trees have the potential for restricting or preventing wind erosion, leaching, surface water runoff and erosion thus weakening pollutant outflow between woodland areas and humans or animals. Please see below diagram for further information.

Woodlands on Contaminated Land

(Image courtesy of Forestry Commission/Crown copyright)

Can woodlands help reduce contaminates in water?

The potential contamination of controlled waters is a major issue when dealing with contaminated land (DETR, 2000). Compared to most vegetation types, trees have both a high transpiration rate (how water moves through a plant) and biomass production. Where the water table is close to the soil surface the uptake of water causes contaminated groundwater to move into the aerobic rhizosphere (area directly next to the roots) where contaminants can be absorbed by the tree or soil particles. Once immobilised, the threat of more widespread contamination is reduced.

Woodland Conclusion

Land defined as being “contaminated” may also be suitable for woodland establishment if this will aid the remediation of the site. Trees have the potential to restrict, prevent or enhance contaminant transport pathways. The balance between these benefits and risks depends on the location, contamination status and soil and groundwater properties of the site.

Conclusion

In summary, contaminated land that is not treated can have a hugely detrimental effect on our environment and health; it can destroy marine life and potentially cause human disease as well as force us to develop on ‘greenfield’ areas. Therefore, we must continue to treat and reuse our brownfield sites for development and ensure we protect both ourselves and our environment by treating our contaminated land on an ongoing basis.

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