Wednesday, April 24, 2013

Cleaning your soil

Westport (in Baltimore) is ripe with empty yards ready for gardeners to invade. It's also an incredibly filthy city. And these yards often attract dumping. So eating that stuff may not be the best idea. But how to improve the soil? I've heard good things about sunflowers removing heavy metals. But what else? What do I even need to worry about?

I'll be calling extension offices in Maryland and DC for soil testing kits. But it looks like Maryland mostly tests for soil condition, not toxins. At least not lead. I'll have to find out about cadmium, arsenic, mercury, zinc, nickel, selenium, PCBs, etc. DC includes a heavy metal test. Probably because the whole "state" is urban.

The term for these plants is "hyperaccumulator". They suck up metals and store them in the stems, shoots, and leaves. Then you can harvest the plant for safe disposal.

Alpine pennycress (Thlaspi caerulescens or Noccaea caerulescens) thrives on zinc and cadmium. Also takes up chromium, copper, molybdenum, lead, zinc, nickel. It soaks up 7-8% of it's dry weight in metals.
Barley (salt tolerant varieties) extract salt.
Canna neutralizes pesticides, solvents, explosives, industrial chemicals, and other xenobiotic substances.
Chinese brake ferns gobbles arsenic. Other ferns are good at other metals.
Dogbane (Apocynum cannabinum) likes lead, but is very invasive and can cause blisters with it's sap.
Hemp should be good. And I can use the ATF to clear the lot for me!
Iberis intermedia soaks up 7-8% of it's dry weight in metals.
Indian Mustard (Brassica juncea) likes lead, manganese, selenium, zinc, cadmium, cesium.
Kidney vetch (Anthyllis vulneraria) soaks up 7-8% of it's dry weight in metals.
Poplar trees like lead. They also break down toxic organic chemicals.
Ragweed (Ambrosia artemisiifolia) likes lead.
Sugar beets will extract salt.
Sunflowers soak up arsenic, cesium-137, strontium-90, chromium, copper, manganese, lead, zinc, nickel, cadmium, uranium, and many organic chemicals.
Wheat takes up lead.
Willows are good at surviving in polluted soil, and gather cadmium, zinc, and copper.
Yellow lupine modified with the bacteria Burkholderia cepacia likes toluene and will break it down within the plant. Other plants will pull out toluene, but let it out into the air.

A pigweed called Amaranthus retroflexus was up to 40 times more effective than others tested in removing radiocesium. So, in ONLY 15 years the soil is clean. GAH!
Adding an organic acid called citrate to soil increases how much uranium that area plants gobble up. God help me if I even have to consider this.

Compost is good for neutralizing some stuff and diluting the concentration of other stuff. If your problem is minor this may just do the trick.

And after writing all that I found these tables. Pick your toxin and it'll name you a plant. [table 1] [link] [link]

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