Pollution-Fighting Plants

Reprinted with permission from UC Davis Magazine Spring 2002
Editor's Note: Teresa Fan is affiliated with the Ecotoxicology Lead Campus Component of the TSR&TP

One day California farmers may grow crops in contaminated soils, and wastelands may become lush Edens of fertility - thanks to the plants themselves.

Teresa Fan is studying how plants can be used to remove toxic wastes from soil.

Plants can rid soils of pollutants or at least render the pollution harmless, believes Teresa Fan, an environmental biochemist in the Department of Land, Air and Water Resources at UC Davis. With Richard Higashi, an environmental chemist at the UC Davis Crocker Nuclear Laboratory, Fan is working on two projects to learn more about how plants can clean contaminated soils.

In one project, funded by the US Department of Energy, Fan is studying how plants can be used to bind up soil pollution found at national nuclear laboratories and nuclear power plants, where radioactive and other toxic wastes may reach groundwater. Plants, soil, and microbes in the soil somehow work together to determine which metals and nutrients plants take up from the soil. For example, plants excrete a variety of different chemicals into the soil, some of which act as signals to soil organisms. The challenge now, according to Fan, is to find out how plants release these chemicals and how these chemicals interact with microbes and soil. Eventually, she said, scientists may be able to induce plants to release the chemicals that immobilize wastes in the soil.

In her second project, sponsored by the state Department of Water Resources and UC's agricultural drainage research programs, Fan is investigating the use of algae to minimize the effects of the soil nutrient selenium, found in excessive amounts in San Joaquin Valley farmland. The valley is a vast tub without a drain; farm water has nowhere to go, and soil nutrients and pollutants alike build up in the soil and collect in toxic reservoirs where they can kill plants and wildlife when accumulated in high levels. The wastes also endanger farmers, who face ever-stiffer environmental regulations on how much waste they're allowed to discharge from their fields.

Fan's research into algae and how they process selenium may provide a clearer picture about how much selenium reaches birds and wildlife. Scientists know that algae take up soluble selenium from soil and water and volatize some of the selenium into the air (where it probably poses no threat), but they don't know how or how much. Once they find out, the restrictions may be able to be refined, reducing the burden on farmers.

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