Lead carriers

[OP]

I'm about to take up a new allotment with a friend, but it's very near the M25 (No. I mean really near. look here.  It's the one in the middle.)

Obviously lead levels are going to be pretty high, but I've carried out soil samples in the area and the levels aren't prohibitive.  However, we still reckon it can be improved on and being biologically minded it occurs to us that there must, somehere, be a plant that preferentially removes lead from the soil.  Because it's a natural toxin a lot of plants have natural barriers to it, leading to things like potatos and carrots with very high lead levels in their skin.  

 Because it's late in the season, we were wondering whether it's worth trying to get a late crop of something in that might draw out some of the lead that we can then harvest and remove from the site.

Has anyone tried anything similar, or know of any lead reducing tactics other than simply bulking up the soil with plenty of earth and compost from elsewhere?

[OP]

[gavin]

Sorry, OP (organo phosphate?  And you're worried about lead?!?!? <grin>) - not something I know about at all, so I'm not much use.  

You've probably already found this - but if not, is it useful?
http://www.hdra.org.uk/factsheets/gg3.htm

Good luck ---- and when do you ever get to sit and talk to your potatoes with the M25 roaring along so near?

All best - Gavin

[OP]

Yeah found that, but thanks anyway.  It's not a massive problem really, as most is going to be polytunnelled by the winter hopefully.  The real problem is the marestail.  Grrrrr.

(OP - OrbitalPete.  A username I share on many BB's from a long ago time when I edited a magazine called The Orbital.  It just stuck.  Organophosphates nasty and bad.)

[ZeB]

This may help...or bore you to death. Lead will be taken up by plants when the lead is bio availiable. Because lead and all other heavy metals have several states (there is a proper chemical name for it that I can't remember) that are determined by the pH.  The art/ alchemy of removing the lead would be to adjust the soil pH so that the lead is in an aqueous solution and therefore bio availiable. The problem with this is while it is in an aqueous state it would be taken up by all the plants and your vege will be slightly toxic. There were some studies done on allotments in the East End of London by Prof Alloway at QMW which looked at lettuce as a way of taking lead out of the soil. I don't know if they changed the pH B4hand.
The good news is that lead from cars shouldn't be too much of a problem with the use of unleaded petrol. Also particulate lead only travels about 50m before dropping out ..........are you still awake?