Tacoma Smelter Plume - Dirt Alert
Chinese Brake Ferns Phytoremediation Study
December 2005 Update

Introduction
Summary of Results
Frequently Asked Questions
What’s Next

Introduction

Summary of Results

	Chinese Brake Ferns (Pteris vittata) grown in arsenic-containing soil in western Washington do take a lot of arsenic into their fronds (hyper-accumulate or bio-concentrate arsenic).
	Brake ferns do not seem to take up lead and cadmium.
	Brake ferns seem to absorb large amounts of arsenic whether the soil contains 30 or 160 parts per million (ppm) arsenic.
	Fronds from brake ferns grown in arsenic containing soil are a dangerous waste at the end of the growing season.
	Brake ferns seem to do best with one-half to two-thirds of a day of full sun, and moderately heavy watering during the growing season.
	Brake ferns do not grow vigorously in shady or cool areas, or when soils become dry.
	We can not yet determine, based on soil sample results, how much arsenic the ferns have removed from the soil. This is probably because of soil contaminant variability.
	Brake ferns developed mature spores in one plot of the seven plots planted. We do not know if these spores can develop into new plants in this climate.
	We do not know if the brake ferns will survive the winter.

For more details and a summary table of the data click here.

Frequently Asked Questions

Answers to frequently asked questions

1. Phyto-WHAT???? What is “Phytoremediation”?

   Phytoremediation (phyto= plant, remediation = contamination “remedy” or cleanup) is the use of plants to remove contaminants from the environment. In this case, using Chinese Brake Ferns to remove arsenic contamination from soil.
    

2. Are Chinese Brake Ferns invasive?

   Ecology has consulted with the Washington Department of Agriculture and the California Noxious Weeds Commission. Experts in both agencies believe the ferns are not likely to be invasive in western Washington. We are, nonetheless, watching careful to see if there are any indications the plants will reproduce and spread. Careful plant counts are made in each plot. To date, 2-8 plants have died in each plot, indicating something around 5% mortality in the plots this year. In one plot, ferns were observed with mature spore bodies under the frond leaflets. Mature spores did not form on plants in any other plot this year. We will continue to monitor for signs of possible invasiveness for the duration of the study.
    

3. What is “hyper-accumulation”?

   Literally translating to extra-accumulating, an organism that concentrates anything from the environment, and maintains a higher concentration in it’s body than in the surrounding environment or food it eats. So you and I are also hyperaccumulaters, at least of calcium (bones), phosphorous (muscle), and other “normal” nutrients. Most plants more complex than algae also hyper-accumulate phosphorous, nitrogen and other essential nutrients. Arsenic, however, isn’t a nutrient that’s needed in large quantities, so the brake fern’s hyper-accumulation, or extreme gathering of arsenic is unusual. This characteristic may be helpful for environmental cleanups, however. We do not know why brake ferns hyper-accumulate arsenic.
    

4. Did you clean up any of the test plots you grew the ferns in?

   Soil sampling results show that none of the plots we grew ferns in this year had the arsenic reduced below the cleanup standard of 20 ppm.

What’s Next

After harvesting the fronds, we covered the ground with a mulch layer to protect the root balls from frost. Late winter we will check to see if the plants are putting out new fronds. If the plants survived the winter, we will continue care for the plants (watering and weeding), and sample the soil, and fronds every again next year. If you are interested in helping tend the plots, please contact Norm Peck, Department of Ecology, by phone at (425) 649-7047 or email: nope461@ecy.wa.gov