Enhancing lead phytoextraction

10 years ago

I recently bought a home in the Boston area and my young children are excited to use the yard--but I suspect the soil is heavily contaminated with lead. We have removed all the siding with its lead paint, but I continue to find (and remove by hand) paint chips all around the skirt of the house. Also, the home is on a relatively busy street, so I suspect it received substantial lead contamination from leaded gasoline pre-1989.

I suspect that the only way to effectively remove lead from the soil will be to remove the soil, but we will not be able to do this for at least a year due to ongoing renovations--and anyway it would be great if we could keep the existing soil. So I've planted sunflowers in the hope these can absorb lead; I intend to discard them (roots and all) as hazardous waste in the fall.

I doubt sunflowers will do much to reduce lead levels, but I'd like to give them their best shot. I understand lead is mobilized and taken up by sunflowers most effectively when soil is acidic (and preferably when treated with a chelating agent like EDTA). The soil is currently full of dead roots from bushes we've cut down; my concern on the one hand is that the soil food web will sequester all nitrogen while it breaks those roots down, limiting the ability of the sunflowers to grow, and on the other hand, the resulting organic matter will buffer the soil and limit its acidity. I don't want to apply compost to enhance nitrogen levels for this very reason.

So I'd like to know--what would be the best approach to fertilizing the soil for the sunflowers while making it as acidic as possible? And do folks have experience treating soil with EDTA? Is EDTA available for this? Would doing any of this be dangerous?

Featured Answer

theparsley

10 years ago

Phytoremediation only works under very controlled conditions, with lots of testing, with specific plant species that have been studied for the ability to sequester the thing you need to remove from the soil, and with a well-executed plan for doing the remediation (including controlling access to the site while remediation is under way, which may take years) and then properly disposing of the contaminated plants afterward. And even when done at scale by professional outfits, it doesn't always work.

You have kids. Get your soil tested and get proper advice for what actions you need to take.

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Comments (7)

j_r_natter71
10 years ago
Likely you have a municipal agency (start with City Hall) or Extension Service office where informed persons can tell you the local practices for managing lead in soil. For one thing, growing veggies in raised beds with imported clean soil -- or soilless planting mix -- avoids removing soil and disposing of it as hazardous waste.

To locate your county's Extension Service office, use this interactive map:
http://npic.orst.edu/pest/countyext.htm
toxcrusadr
10 years ago
City or County Health Department.

As an env. specialist working in this exact field, I can recommend a couple things. First you will get a lot more bang for your buck TESTING your soil - both out in the yard and right near the house - than spending time and $$ tweaking your soil trying to suck up lead that may or may not be present into sunflowers and disposing of them. I mean it's a cool idea but....read on.

The soil near the house will likely be much higher than out in the yard. It doesn't migrate far from where it falls. So find out from the health dept how to get soil tested and collect composite samples in both areas. It should not cost much and may actually be free.

Finally if you want to prevent exposure to your kids, once you know what is there, covering the soil works just as well as remediating it. If it's hot near the house, consider mulch, pavers, etc. Or just remove soil in that area. Even with gardening, most of the exposure is from particles of soil stuck to vegetables (root crops, lettuce etc. are the worst) rather than actual uptake into the plant. Minimize exposure to affected soil: playing on it, digging in it. Make sure hands are washed. Simple things like that cost very little and make a big difference.
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theparsley
10 years ago
Information for the state of Massachusetts:

http://www.mass.gov/eea/agencies/massdep/recycle/reduce/lead-contamination-in-your-yard.html
toxcrusadr
10 years ago
theparsley makes a very good point. You really don't have time to wait. The biggest effect of Pb on the nervous system occurs before age 6. Adults are much less susceptible. There can also be fetal exposure. Get some tests done first and go from there.
User
10 years ago
I would also recommend getting the soil tested before you freak out.

Then pave over or remove dirt from the "hot spots" and have your kids wash their hands after playing in the dirt. Use raised beds for vegetables.

The REALLY bad lead poisoning comes from children with "pica", eating chips of lead paint off the woodwork in their crumbling slum. Because of the pica, they tend to eat a LOT of paint for its faintly sweet taste, much more than a kid playhing in the dirt would ever consume.
toxcrusadr
10 years ago
Lead dust in older houses is also a problem. Old paint gives off dust particles as it degrades, which collect in window wells and sills, and in carpets and cracks in wood floors. Not to freak you out but there are other sources besides soil and kids can have high blood lead levels without actually eating paint chips. If you have an old house with lead paint inside - even if it's covered with new paint - you might consider a wipe test of the floors and window wells. Pretty cheap to do I think.