Chemists Help Protect Our Soil And Water From Contamination

It is not uncommon, actually not uncommon at all for the soil that are food is grown in and the water that is used to irrigate it to become contaminated with low levels of contamination. What type of contamination? Well, there are many types. Too many to mention in a short article, but an example is leaking storage tanks. For years, environmental chemists have been analyzing soil samples near and around underground gasoline storage tanks so as to make sure that they are not leaking and contaminating our water supply. How is this testing done?

Generally, the process follows a simple format. Small soil samples are collected, usually around a hundred grams. These samples which cover all sides of the storage tanks are then sent to a lab that performs a series of steps in order to determine whether or not there is contamination.

The first step a chemist is to perform is to remove a portion of the soil sample and record it's weight. This is necessary because the final calculation of the potential contamination amount will be a function of the total amount of sample used. Once a known amount is weighed, an organophilic solvent is added to the sample to begin dissolving any potential organics that may be in the soil. In many cases, the water/soil mixture is aggravated by ultrasonic waves. This helps break the bond between the soil and the hydrocarbon contaminating it.

Once the petroleum based hydrocarbons have dissolved into the solvent, the sample is then filtered and concentrated to a known volume. Standards are then prepared with known amounts of THC in solvent so as to prepare both a baseline and curve for instrumental analysis. The instrument used in this case is an infrared spectrophotometer. An infrared spectrophotometer detects the presence of the carbon-hydrogen bond. The more C-H in the sample, the more of the IR radiation is absorbed which can then be correlated to an amount.

Extracted samples are then run and compared to the curve revealing the concentration of the total hydrocarbons in the sample. Concentration is then back calculated, via the sample volume and grams of soil weighed to yield the milligrams of hydrocarbons per kilogram of soil or parts per million by weight.

If contamination by gasoline or other hydrocarbon based fuels is detected, a new set of samples is generally taken further out systematically until the extent of the contamination is discovered. In most cases, any contaminated soil found must be extracted and incinerated so as to remediate it.

Freshly remediated soil will no longer leach petroleum based hydrocarbons into groundwater which can potentially contaminate drinking water or well water.