Signs of Soil Contamination

On this blog, we often discuss environmental contamination on the chemical or microbial level, but not all forms of contamination are invisible to the human eye, and soil contamination is one of them. This week, we take a look at six visible signs that there may be contamination present in a soil environment.


Discoloured and stained soil

Soil staining and discolouration as well as ‘slimy’ or ‘oily’ patches are generally a sign that there is an abundance of a substance that does not naturally occur in the soil. Soil is a complex mixture of plant and animal decay, minerals, nutrients and when this balance is thrown off through an excess of heavy metals, industrial waste, pesticides or herbicides, it is reflected in the colour and consistency of the soil.



When there is an abundance of a foreign substance trapped in the soil, it can sometimes (but not always) produce a distinctive odour. For example, a clear sign of petroleum contamination is the smell of oil whilst soils contaminated with a heavy metal like lead will not smell any different.


Absence of birds/animals

Soil contamination alters the metabolism of microorganisms and arthropods living in the soil and the chemicals they consume become more concentrated as they move up the food chain. The result of this is that soil contamination often wipes out predator or consumer species. For example, soil containing DDT is consumed by worms and insects, which are a primary food source for birds. Once the birds consume these life forms, the DDT chemicals affect their systems, leading to weakening egg shells and increased chick mortality.


Minimal plant life

Unsurprisingly, soil contamination also alters the plant metabolism, causing plants to weaken, wither and die.



If a previously vegetated area is cleared through contamination, it has a secondary effect of soil erosion, as the vegetation is no longer present to protect the soil from being blown or washed away.


Paint chips

A classic and obvious sign of lead contamination due to paint is the presence of paint chips in the soil around a building.


No signs at all

Sometimes, contaminated soil has no visible symptoms and the only way to definitively tell if soil is contaminated is to have samples collected and tested by certified professionals. Alpha Environmental offer soil assessment services for businesses, local government, and private land owners. To learn more about our capabilities, please don’t hesitate to get in touch with us by calling 1300 039 181.