Understanding Soil Pollution: Testing Methods And Techniques

Soil pollution can be caused by a number of factors, including petroleum products, heavy metals, industrial solvents, pesticides, salts, fertilisers and plant nutrients. Testing for these pollutants can be complicated and there is no home test that can detect all possible pollutants. However, there are some home test kits available that can test for nutrients, salts and pH. These kits can cost between $20 and $150, but results can be unreliable. Alternatively, you can contact your county's Cooperative Agriculture Extension Service, a state university or a private soil testing company to test your soil for primary nutrients, heavy metals and hydrocarbon contamination.

Testing for heavy metals

Soil test kits can be purchased for $20 to $150, but they are often unreliable because they test very small amounts of soil and are vulnerable to user error. If you do decide to use a kit, follow the instructions provided. Most likely, you will be instructed to put a marked volume of soil into a container and add a certain chemical. Some kits will have the proper quantity in individually wrapped packages, or will tell you how many drops of liquid to add. Most kits give results based on an optical comparison of the solution's colour to a chart of nutrient values.

Alternatively, you can contact your county's Cooperative Agriculture Extension Service, the nearest state university or a private soil testing company. Searching "cooperative extension" and your state's name on the Internet should yield results. Whoever you contact, tell them you want to test your soil for primary nutrients, heavy metals and hydrocarbon contamination.

To collect a sample, use an uncontaminated tool, such as a clean garden spade, or scoop the soil with the container itself. Collect a small soil sample from 2 to 6 inches below the surface and put it into a container. Add water to the container – just enough to make a liquid mixture but not so much that it's clear.

Testing for hydrocarbon contamination

Home testing kits are available for around $20 to $150, but they are not always reliable. They test very small amounts of soil and are vulnerable to user error. The actual methods and procedures of different kits vary widely, but most will instruct you to put a marked volume of soil into a container and add a certain chemical. Some kits will have the proper quantity in individually wrapped packages, or will tell you how many drops of liquid to add. Most kits give results based on an optical comparison of the solution's colour to a chart of nutrient values.

If you are taking a sample to test for petroleum hydrocarbons, make sure to protect yourself from exposure to harmful chemicals by wearing gloves and possibly a mask.

A professional lab can analyse a single sample for PAHs and PCBs, two common petroleum hydrocarbon contaminants in soils. This costs $200-300. You can also just test for "total petroleum hydrocarbons" (TPH), which gives you a general sense of whether there are significant levels of petroleum hydrocarbons worthy of investigating more but does not give you specificity.

There are also portable kits that can be used on-site, such as PetroFLAG, which environmental professionals can use to determine hydrocarbon contamination levels at a fraction of the cost of laboratory analysis.

Using a soil test kit

Testing soil pollution can be complicated, and there is no way to detect all possible pollutants with a home test. The most common pollutants are petroleum products, heavy metals, industrial solvents, pesticides, salts and fertilisers or plant nutrients in high concentrations. Only nutrients, salts and pH can be tested at home with a soil test kit, which costs from $20 to $150. Results from these kits are often unreliable because they test very small amounts of soil and are vulnerable to user error.

To use a soil test kit, you will need to collect a small soil sample from 2 to 6 inches below the surface. Use an uncontaminated tool, such as a clean garden spade, or scoop the soil with the container itself. Avoid contaminating the sample, and place it in a clean container. Mix the soil with two parts water for every part soil. Add just enough water to make a liquid mixture but not so much that it's clear.

Follow the instructions in the soil test kit. The actual methods and procedures of different kits vary widely. Most likely, your kit will instruct you to put a marked volume of soil into a container and add a certain chemical. Some kits will have the proper quantity in individually wrapped packages, or will tell you how many drops of liquid to add. Most kits give results based on an optical comparison of the solution's colour to a chart of nutrient values. Compare the tested values to the requirements of your particular crop. Different fertilisers offer varying ratios of these chemicals.

Write down your soil's pH value. A pH meter will give a two-digit digital readout of pH. A pH stick will change colours, and will also come with a chart indicating which colours correspond to which pH. Repeat the test with a similar soil sample for additional accuracy. Soil can vary widely from one area to the next, and different plants have different pH requirements.

If you want to test your soil for primary nutrients, heavy metals and hydrocarbon contamination, contact your county's Cooperative Agriculture Extension Service, the nearest state university or a private soil testing company. Searching "cooperative extension" and your state's name on the Internet should yield results.

Testing pH levels

To test pH levels, you will need to collect a small soil sample from 2 to 6 inches below the surface. Avoid contaminating the sample, and place it in a clean container. Mix the soil with two parts water for every part soil. Add just enough water to make a liquid mixture, but not so much that it's clear.

You can use a pH meter to get a two-digit digital readout of pH, or a pH stick, which will change colour to indicate the pH level. You can then compare this to a chart indicating which colours correspond to which pH levels. For additional accuracy, you can repeat the test with a similar soil sample.

It's important to note that soil can vary widely from one area to the next, and different plants have different pH requirements. If you are testing the soil for a specific crop, be sure to compare the tested pH values to the requirements of that crop.

Contacting a private soil testing company

Testing soil pollution can be complicated, and there is no way to detect all possible pollutants with a home test. The most common pollutants are petroleum products, heavy metals, industrial solvents, pesticides, salts and fertilisers or plant nutrients in high concentrations.

If you want to test for primary nutrients, heavy metals and hydrocarbon contamination, you can contact a private soil testing company. You can find one by searching "cooperative extension" and your state's name on the Internet.

When you contact a private soil testing company, they will likely instruct you to collect a small soil sample from 2 to 6 inches below the surface. You should use an uncontaminated tool, such as a clean garden spade, or scoop the soil with the container itself. Place the sample in a clean container and mix it with two parts water for every part soil.

The company will then provide you with specific instructions on how to test the soil. This may involve adding a certain chemical to the soil sample and comparing the colour of the solution to a chart of nutrient values.

It is important to note that results from home test kits can be unreliable, as they test very small amounts of soil and are vulnerable to user error.

Frequently asked questions