Common soil minerals might mop up pesticides

New research suggests that dousing soils with solutions that are rich in everyday minerals and salts might help soils more effectively soak up pesticides and other organic contaminants. The work, detailed in a recent issue of the journal Environmental Science & Technology, shows that sponge-like properties of soil clays can be changed, especially by tweaking concentrations of naturally occurring potassium.

From Michigan Agricultural Experiment Station :

MSU study shows how common soil minerals might mop up pesticides

New research at MSU suggests that dousing soils with solutions that are rich in everyday minerals and salts might help soils more effectively soak up pesticides and other organic contaminants.

The work, detailed in a recent issue of the journal Environmental Science & Technology, shows that sponge-like properties of soil clays can be changed, especially by tweaking concentrations of naturally occurring potassium.

The new findings by Stephen A. Boyd, MSU professor of crop and soil sciences and a Michigan Agricultural Experiment Station (MAES) scientist, and colleagues at MSU and Purdue University, may help build models that better explain the role of basic minerals in the spread of pollutants in soils. These, in turn, may lead to more effective phytoremediation — the use of plants to remove contaminants from the soil.

”This chemistry provides the basis to reliably and inexpensively control the leaching of important classes of contaminants and to improve the effectiveness of bioremediation technologies such as phytoremediation,” Boyd said.

This is how it works: The minerals in the soil initially soak up the pollutants. However, over time, the minerals slowly release their grip on the pollutants. This slow release makes it easier for the plants used in phytoremediation to remove the contaminants from the soil.

In their research, Boyd and colleagues mixed common clay with varying potassium and calcium concentrations and then tested how the various recipes responded to three pesticides. Soil minerals interact with and bind to all sorts of chemicals, so it was no surprise that the soils with more ions did a better job soaking up the contaminants.

What was surprising, Boyd said, were the differences between potassium and calcium in holding contaminants. Depending on the pesticide, potassium-soaked soil proved to have between four and 75 times the sponge-like ability of soil soaked with calcium.

”A little potassium goes a long way,” Boyd said. ”Small increases in potassium concentration made the soil sample significantly more absorptive.”

X-ray diffraction helped explain why, he said. X-ray images show that, at low concentrations, potassium ions aren’t distributed evenly through the soil. When the concentration gets high enough, the miniscule spaces between soils’ basic building blocks become potassium-saturated, and soon the entire soil cross-section starts soaking up pesticide.

In their paper, the authors also describe several potential applications of their findings, including more environmentally friendly techniques to apply pesticides and more effective ways to clean up contaminated soil.

The Environmental Science & Technology paper is available at: on the Web.

The Michigan Agricultural Experiment Station is one of the largest research organizations at MSU. Founded in 1888, the MAES funds the work of nearly 400 scientists in five colleges at MSU to enhance agriculture, natural resources and families and communities in Michigan.