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Using Super Plants to Clean the Environment. Radin, J.W. June 2000. Agricultural Research. 48(6):2. (Journal article)

Certain plants can detoxify the soil. Plants described in this article are virtual vacuums for cleaning up chemicals and harmful nutrients that pose health threats to humans and the environment. The act of using nature to detoxify, called phytoremediation, can be an effective way for the system to be rehabilitated. For the backyard gardener, a number of plants have been suggested to purify your soil. Alpine pennycress (Thlaspi caerulescens) has been reported to accumulate excesses of zinc and cadmium — as much as 10 times more than normal, and plants in the Brassica family, like mustard and canola, thrive on selenium and boron-laden soils. The finish to the short article is a disclaimer that research in phytoremediation is slow and complicated. Eight years later, the research provides much more and we invite you to visit the Missouri Botanical Garden website (www.mobot.org/jwcross/phytoremediation/) for more current information on ferns accumulating arsenic and cottonwoods accumulating mercury and more.  You can also access complete articles at this website.

Microbial Immobilization of Cadmium Released From CdO in the Soil. Kurek, E. and J. Bollag. 2004. Biogeochemistry. 69(2):227-239. (Journal article)

Cadmium is a heavy metal known to have harmful effects on soil microorganisms. The writers provide us with the basics on cadmium and its presence in the soil, and explain that synthetic fertilizers are the primary source to spreading this toxin in the environment. Traditional solutions to resolving most forms of soil poisoning include costly soil replacements or chemical treatments, but detoxifying the soil is possible, only recently, as this article suggests, with various specialized microbes. We caution that this is a technical article but mention it because the toxicity and the understanding of the fate of cadmium metal (or any other metal for that matter) in the soil are important. The first step for us, as homeowners, is to know what chemicals reside in our soils. This may involve reflective thinking about our properties as historic urban places that most likely included multiple owners and chemical usage at a time when application was more acceptable than it is today.

Evaluation of Extraction Procedures for Removing Lead from Contaminated Soil. Tawinteung, N., P. Parkpian, R. Delaune, and A. Jugsujinda. 2005. Journal of Environmental Science and Health. 40(2):385-407. (Journal article)

Lead is another metal known to be harmful to humans. The researchers of this article chose to clean lead-contaminated soils that were collected from sites located near an abandoned battery factory and a secondary lead-smelting factory. Complicating their clean up is the fact that lead is very difficult to remove once it is present in the soil. Identification, sampling, transport, and extraction methods, including soil washing and flushing are all documented as well as a good discussion of how lead interacts with the soil, and where it might be found in our yards.

Graphs and tables show the soil washing process, distributions of lead in the soil at the study area, and soil flushing. The tables show certain soil types and physical characteristics of contaminated soil samples. What are their conclusions? Soil farther from a lead source is less contaminated, and soil flushing and washing are both effective in removal of lead from the soil.

Improvement of Degraded Physical Properties of a Saline-Sodic Soil by Reclamation with Kallar Grass. Akhter, J., R.Murray, K.Mahmood, and K.A. Malik. 2004. Plant and Soil. 258(1):207-216. (Journal article)

While soil with salt build up may not be a problem in the Portland area, salt-tolerant plants can improve the physical characteristics of saline soil around your home. Just what saline soil is and why it is a growing concern, is addressed in this Journal article. Akhter et al. recommend kallar grass for better water-retention capabilities in your soil. Where to plant the grass, how much to plant, and in what soil types, are covered in this issue of Plant and Soil. The conclusion is that, over time, with age and maturity, kallar grass improved soil’s ability to retain water along with soil porosity, which allows salts to leach from the topsoil.

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Cover:  Illustration by Dianne Tolman, a small business owner of Big Pine Native Plants.

© 2008 Deborah Tolman, Ph.D., Michelle Lasley, and Joe Parker