Qiang He

UTK civil and environmental engineering

When we turn on our faucets here in the United States, we expect to get water that’s safe to drink.

How long this will be true depends, in part, on research by JDRD team leader Qiang He and his LDRD partner project leader Christopher Schadt to determine what goes on between microbes and organic matter in our soils.

Research shows that microbes feeding on the secretions from nearby roots or dead plants alter the composition and characteristics of organic compounds dissolved in the soil. As a result dissolved nitrogen, phosphorous, sulfur, and other organic matter may be more or less likely to biodegrade, react with minerals in the soil, form carcinogenic byproducts during water-treatment disinfection, or become a food source for microbes and biofilms in water distribution systems, not to mention transporting contaminants to groundwater, lakes, and streams.

But exactly how microbial communities and dissolved organic material influence each other is unclear. To find some answers, Qiang He and doctoral graduate student Yan Zhang are studying the dissolved organic material and microbial communities in the soil surrounding decaying switchgrass roots, one of the crops being considered for renewable biofuel production.

The team’s LDRD counterpart grows traceable, carbon-labeled switchgrass in the lab and uses it to study how the substances released into the soil by the roots influence surrounding microbial community structure and carbon cycling in the soil. JDRD first-year results show that fermentative microorganisms increase during root decay and the dissolved organic compounds produced early in the process are predominantly acidic.

JDRD Project: Linkage between soil microbial activities in the rhizosphere and functional characteristics of dissolved organic matter;
LDRD project: Carbon drivers of the microbe-switchgrass rhizosphere interface, Christopher Warren Schadt.

Information from this project served as key preliminary results for a successful National Science Foundation project beginning May 2009.

The JDRD team also found that dissolved organic carbon concentrations in runoff from the Beaver Creek watershed steadily increased during intense storms, but held to a near-constant rate in storms of less intensity, suggesting a different mechanism is at play in each. Runoff patterns are especially important because dissolved carbon can form compounds with toxic heavy metals, such as arsenic, cadmium, cobalt, and lead, and transport them into nearby lakes and streams.