More on Use of CCA-Treated Wood in Gardens

Larry London london at sunSITE.unc.edu
Fri Dec 18 00:32:51 EST 1992


In article <99.2b305654 at ivgate> bob.batson at mtask.omahug.org writes:
>                More on Use of CCA-Treated Wood in Gardens
>
>  On page 91 of the August 1992 _HortIdeas_, we reported that researchers
>in New Zealand have suggested that sawdust from preservative-treated wood
>(CCA: copper/chromium/arsenic) might be suitable for use as an amendment
>for garden soils, despite evidence the roots of some plants growing in
>contact with such sawdust can concentrate copper, chromium, and arsenic
>"to high levels." But what about the safety of placing CCA-treated
>"landscape timbers" in close proximity to food plants? Master Gardeners in
>Bexar County, Texas, took soil samples six inches deep and one inch
>laterally from CCA-treated timbers in several gardens, old and new; they
>compared arsenic levels in those samples to levels in samples taken 12
>inches laterally from the timbers. The results: between 1.1 and 1.4 parts
>per million of arsenic, regardless of whether the samples were taken near
>treated timbers or not. Arsenic often occurs naturally in soils at levels
>up to 20 parts per million; experts consider dangerous levels to be in
>the 200-300 parts per million range. The Master Gardeners concluded (in
>agreement with the U.S. Environmental Protection Agency) that CCA-treated
>timbers are acceptable for use in vegetable gardens.
>  The Master Gardeners also tested for creosote in garden soil near used
>railroad ties; none was detected down to the limits of the testing
>apparatus (660 parts per billion).
>  Reference: Calvin Finch, "Can I Use That Wood? Railroad Ties and
>Landscape Timbers Are Safe," THE GARDEN GATE, October 1992, 5. (Lane
>County Extension Service, 950 W. 13th Ave., Eugene, OR 97402.)
>--------------------------------------------------------------------------
>Reprinted with permission from the November 1992 _HortIdeas_. Copyright
>1992 by Greg and Pat Williams. HortIdeas is $15 (2nd class mail within the
>USA) for one year (12 issues). For more information or a subscription,
>write: HortIdeas, 460 Black Lick Road, Gravel Switch, KY 40328, USA. 
>*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
>Bob Batson
>bob.batson at mtask.omahug.org



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