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Tips for the Compleat Gardener: Phytoremediation review and action


You have determined the soil or water is contaminated and how you approach amelioration depends on the nature of the contaminant, the time frame, level of commitment and ultimate goal. In so many places lately rivers have flooded towns, factories, sewage plants, washing the land with many kinds of contaminants, each with its own impact on the well being of a community.

We know from the recent experience in Michigan that lead can be invisibly present and we also know an excess of lead in the body can cause anemia, weakness, brain and kidney damage and damage to the developing nervous system of the unborn.

Lead has been lingering in our environment on the walls of old houses, in the soil from when it was in gasoline, and in old plumbing among other places.

Several other heavy metals, arsenic, copper, cadmium, chromium, nickel, silver and zinc for example, have been left around for various other reasons from fertilizer to factory.

One way to pull the heavy metals from the soil is with plants known to naturally draw them up during growth into their biomass call phytoaccumulators. Some plants can take in a 100% more than others and these are called hyperaccumulators.

It has been determined that members of the mustard family, the Braissicas, specifically B. juncea, ragweed, hemp dogbane are the latter while lettuce, carrots, radishes and turnips do their part as does Alpine pennycress. When these plants come to maturity they need to be harvested and incinerated which allows the heavy metal to be retrieved from the ash. If they are unharvested the metals just return to the soil.

This sort of remediation is fairly shallow but can rid the soil of metals after a season or two. It seems to me that following every flood the Department of Public Works ought to spread mustard seeds in all untended land with the intent to harvest and burn.

I have read that enough of the metals can be retrieved to pay for the process. If any of those vegetables are frequently on your plate it is good to know where they grew. The thing about heavy metals is they cannot be destroyed, only moved around.

If aluminum is your contaminant hairy goldenrod (Solidago Canadensis), barley (Hordeum vulgare), highland bent grass (Agrostic castellana) and Blue-tongue grass are at your service.

Some plants like the tall reeds one sees in basins by shopping centers are phytostabilizers, they trap pollutants in their root systems. This is a way to deal with petro-pollutants that come from cars. Some times these plants release an enzyme that actually makes the solvent less toxic. Water hyacinths absorb the contaminant into roots and duckweed removes copper, cadmium and zinc.

Man-made pollution can often be metabolized by plants and released as non-toxic things through the process of phytodegration. In some cases nutrients are given to the microorganisms to encourage the process.

Cannas through their metabolism can render pesticides, explosives industrial chemical and solvents non-toxic so it would seem appropriate to plant a line or row of cannas between a property where chemicals are often applied and one where they aren’t.

What it gets down to is our personal commitment to heal the earth and our willingness to work with plant solutions. It would be difficult for an individual to plant phytoaccumulators then allow to mature, harvest and incinerate and go on to harvest the metals from the ash, full circle, but your local government can be encouraged to plant any fallow township property that may have been polluted, then harvest and incinerate.

Go to your township and borough meetings and suggest the idea, you have only heavy metals to lose.