URBAN AG
What are soil contaminants?
And how did the soil get contaminated? Soil is a complex mixture of minerals,
Heavy car and truck traffic can contaminate soil, and so can a single car. Have you ever noticed a shiny puddle under your car in the driveway? That’s oil - a petroleum product - and when it rains, that oil will end up in the soil!
organic material, water, and various lifeforms. In its original state, soil was an uncontaminated substance covering the earth. But humans have intentionally and accidentally poured harmful products onto it in some areas. The waste can hurt the soil and possibly human, plant, and animal health.
UAC MAGAZINE | SPRING 2019
This article covers the most common soil contaminants, how they got there, and how they can pose problems for human health.
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By definition, any substance in the soil that exceeds naturally-occurring levels and poses human health risks is a soil contaminant. As a quick example, arsenic naturally occurs in some soils. But if a person sprays certain pesticides on their yard, that could cause soil contamination. Lead is also very dangerous but occurs naturally in some soils. It was used in gasoline until 1989 and can still be found contaminating soils today. The biggest risks for soil contamination are in urban areas and former industrial sites. If you are unsure about the condition of the soil near your home or property, it’s best to have a soil test done to be sure about its safety. Of course, most soil is perfectly safe for play, gardening, and recreation, but it’s best to be safe. Common contaminants in urban soils include pesticides, petroleum products, radon, asbestos, lead, chromated copper arsenate, and creosote. In urban areas, soil contamination is largely
caused by human activities. Some examples are manufacturing, industrial dumping, land development, local waste disposal, and excessive pesticide or fertilizer use. Heavy car and truck traffic can contaminate soil, and so can a single car. Have you ever noticed a shiny puddle under your car in the driveway? That’s oil - a petroleum product - and when it rains, that oil will end up in the soil! When soil is contaminated with these substances, it can hurt the native environment. Many of these substances are just as toxic to plants as they are to humans. In addition, since soil is the “earth’s kidney,” contaminants can trickle through the soil and get to our water supply. You can see why soil contamination is such an important topic! Where and how much contamination is added to soils will largely determine how that contamination spreads throughout an area. The type of soil will also play a role in its distribution. For example, certain contaminants may reach groundwater sources more easily in sand than clay. This is because of faster infiltration rates of coarse-grained sandy soil types. Fine-grained clay soils or organic material in surface soils can hold contaminants tightly, which means the contaminants will accumulate if left undisturbed (that is, no excavation or tillage). Some human activities may occur at the same time. For example, some new housing areas are built on old industrial sites. Those soils may have buried soil contaminants that are brought to the surface when the houses – or roads to support them – are put in. Newly resurfaced contaminants may then be redistributed throughout the urban environment by wind (as
