UD Soil Student “Mines” with a Microscope

Chances are that when David McNear looks at a flower, he’s not just admiring its color or delicate petals. McNear is mining. Although he doesn’t have a pick or a flashlight, he is searching for traces of minerals and metals.

McNear is a University of Delaware doctoral student in soil chemistry. He has spent the past three years researching how certain plants can be used to clean up polluted soil beds, especially in the beds of former refineries. Leftover metal in the soil of these polluted sites is absorbed through the plant’s roots and stored in the leaves. The theory is that if metal-absorbing plants can be better understood, they could remedy ground pollution without extensive excavation. Then the plants could be harvested for their valuable metal contents.

McNear hopes his research can help do more than cleaning polluted soils. “There are some humanitarian applications for this technology, too,” he says, “which is pretty cool.” Many societies throughout the world suffer from a short supply of necessary dietary minerals such as zinc, he explains. If a plant, such as corn or wheat, could be bred to absorb zinc from the soil, the crop could offer a solution to malnutrition. Before this can happen, however, some concerns must be addressed with research, such as if a plant that can absorb zinc is developed, could it also absorb arsenic or other harmful materials. And that is what McNear hopes to understand.

For his research, McNear uses one plant, Alyssum murale, which is capable of moving metal from the soil to its leaves. He is trying to identify how this species absorbs nickel in neutral soils. When soil has a more acidic pH, typically nutrients are mobilized and absorbed through plant systems at a faster rate, he says. However, alyssum species do the opposite. They function at a more efficient rate in a neutral pH soil. No one knows why. McNear hopes to change that.

Alyssum plants are capable of absorbing metal—a rare phenomenon in the plant world. If McNear can determine just how this diminutive plant does it, the knowledge could be applied to breeding the mechanism into a larger plant such as corn. Since metals are stored in the stalks and leaves of plants, the more biomass a species has, the more metal it can absorb.

“Right now, we’re trying to understand alyssum,” he says, “with the expectation that our results will enlighten us as to what’s going on in other plants.”

While alyssum, a tiny, flowering groundcover, is perfectly suited for the climate in its home in northern Turkey, the 1 ½ -inch tall alyssum plant is too small for McNear’s ultimate purposes. He hopes that one day his research can be applied to much larger plants. Until that happens, McNear plans to keep mining with his microscope.