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Removing arsenic and other wood chemicals from soil

Posted by cynbin z6 CT (My Page) on
Tue, Feb 22, 05 at 19:18

I have designed a garden in my backyard where my shed currently is. The shed has been there for 20 years. The platform around it is made of pressure treated wood (probably 4x8's), and the floor is some unknown thin wood (I think it is from England!) I was thinking of removing 4 inches of the top soil that is below the shed and replacing it with new soil. (Additionally, each bush/plant would have its own new dirt around it)Will this be good enough? How far out would I have to dig?

I am planting blueberries, raspberries, strawberries, grapes and watermelons.

I heard that the arsenic levels don't rise over the years, but because it has been 20 years, has the arsenic been diluted, washed away or gone deep into the ground?

Follow-Up Postings:

RE: Removing arsenic and other wood chemicals from soil

As far as I know any arsenic in soil will not usually have any effect on plants. It does break down and will not affect the quality of any plants

RE: Removing arsenic and other wood chemicals from soil

  • Posted by EricWI Dane County WI (My Page) on
    Wed, Feb 23, 05 at 16:15

My suggestion is to keep the pH neutral, or slightly above 7, in the part of your garden where the shed was located. Alkaline soils tend to sequester, or trap, metal contaminants. If there is any arsenic in the soil, it should remain in the soil & not affect the plant, or the fruit. Since blueberries do best with soil pH between 4 and 5, they will have to be planted somewhere else.

RE: Removing arsenic and other wood chemicals from soil

Arsenic is a heavy metal and will come from soil to plants to berries to you. You can replace soil or (I have read on Internet or some magazine) you can plant special fern that will remove arsenic from soil and then you need to dig and dispose these ferns. Just to be on safe side, you always can test level of arsenic in soil in labs.

RE: Removing arsenic and other wood chemicals from soil

Another plant you can try for removing the arsenic is datura. It's used often to remove metals from the soil, and it's easy to grow, too.

RE: Removing arsenic and other wood chemicals from soil

Hi guys,

I contacted a chemist in my state's agricultural experiment station who had done arsenic tests. I wanted to post his answer in case anyone else was interested in this subject. He said digging deeper into the soil than what I planned to, going out more than one foot, combined with the fact that the feeder roots of the items I am planting will be in the new soil, was "sound". He said he would be more concerned if I was planting, say lettuce, where the leaf itself is the edible. He also gave me some examples of studies using different vegetables growing in arsenic soil and what their arsenic levels in the edible parts would be.

Now if I could just get the snow to melt so I can start digging out all this icky dirt!

By the way, where can I get "datura"? Is it a perennial in our zone?

Thanks guys for taking the time to answer me.

RE: Removing arsenic and other wood chemicals from soil

Daturas can be annuals or perennials, depending on the climate. Zone 6 they might regrow from roots. They reseed prolifically, and they are considered a weed, but they have beautiful flowers that release a sweet scent at night. I have grown them just because I like them. They're easy to grow. Datura stramonium (Jimsonweed) is the easiest, but lots of the studies of metal uptake were with D. innoxia, which the Army has even been used to remove TNT from the soil.

RE: Removing arsenic and other wood chemicals from soil

From my experience with a lumber mill & yard and a shallow bored well...arsenic was undetectable despite yearly samples from a certified laboratory. Heavy metals do not migrate easily. I'd analyze the soil before going to any great effort for treatment. You might find that arsenic is in greater quantity (naturally) in the subsurface anyhow.

RE: Removing arsenic and other wood chemicals from soil

The pressure treating was probably CCA, copper-chromium-arsenic.

Unless the shed was extraordinarily leaky it is likely the only place that any leaching of arsenic from wood took place was at the edges where the footing got rained on, or especially at any footing or posts on or into the ground, but only where the ground could get wet. Thus the interior area may be fine. It might be worth your while just to dig up where soil was in contact with, say, a post, or just beneath the exposed (rained on) outer edge of the flooring/footing.

However, arsenic is a lot worse than we often credit to be (arsenic in food and drinking water has triggered the research). The foods are mostly animal though, I believe, or marine plants.

There is a lot of interest in this now: I'll bet a fair amout of information is posted on the Net.

In city gardening where lead is a big problem it is said that an superabundance of organic matter helps inhibit uptake, but I haven't seen a scientific study.

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