arsenic and lead in soils

Hello all

Just wondering if anyone has any tips/experience in bioremediation of soils contaminated with arsenic and lead? I have read about sunflowers and indian mustard, any other thoughts/suggestions?

Cheers!

Bron

Chinese Brake fern (Pteris vittata) also accumulates arsenic, and ragweed will accumulate lead. Remember, when sucking up heavy metals the plants have to be pulled up roots and all and disposed of off of your property. Ideally the lead and arsenic should be recycled, but I don't know that facilities for that are common.

supposedly , having lots of bio in the soil causes plants to uptake less heavy metals.
if you are trying to "cleanse", do it before you pump up the ground.
that way the plants are less picky, and will have to suck up everything with the water.

Naomi, my soil's very lead-contaminated. I'm totally unfamiliar with arsenic, which I think is worse.
I'm just trying to feed as much OM into the soil as possible, and always keep a thick layer of mulch on it.
I'm confident that heavy metals basically don't move through plant tissue; the danger's in ingesting or inhaling contaminated soil.
I'll happily eat stuff from out the front, but I wouldn't grow root crops...
From what I've researched, we're talking decades, more like centuries to remove heavy metals using phytoremediation.
Fungi looks much more...fun...and I understand they actually break down the metals, rather than just 'suck them up': you don't have to dump them, in fact they can be harvested!
These old threads might be helpful:
lead thread
heavy metal thread

According to Paul Stamets... There are a great many species of fungi that are dynamic accumilators of various heavy metals, toxins and radiations... Do NOT eat them if used for bioremediation! Dispose of them as toxic waste, in one fashion or another. The mushroom fruitbodies must be harvested and disposed of, if wishing to successfully remove a toxin in question.

According to Paul Stamets in "Mycelium Running", shaggy mane mushrooms (Coprinus comatus) are strong bioacumulaters of both lead and arsenic, so they can probably be used as part of a bioremediation plan. Shaggy manes can be grown on sawdust/woodchips, freshly seeded new lawns or on compost. Like David said, just don't eat any of the mushrooms!

Oh dear, here I am recommending someone eat lead
I confused my science. I know people using fungi to break down compounds like DDT, but it's impossible to break down elements, ie heavy metals.
I 'd look into mycoremediation, but please don't eat the mushrooms!

http://www.nytimes.com/2011/07/21/science/earth/21fishbones.html?pagewanted=all
The fish bones are full of calcium phosphate, he said. As they degrade, the phosphates migrate into the soil. The lead in the soil, deposited by car exhaust from the decades when gasoline contained lead or from lead-based paint residue, binds with the phosphate and transforms into pyromorphite, a crystalline mineral that will not harm anyone even if consumed

Maybe monitor your ph levels too.
I have heard, on his latest video, Geoff Lawton say that if ph drops below 4.5 then uptake of the heavy metals by the plants can occur.
He also said that large amounts of mulch will buffer acid rain events which might drop the ph of the soil to dangerous levels.
That is what I gleaned from listening to this
Ask an Expert in Permaculture

this says the phosphate isn't doing just that.

tabacco turns out to be a good catch crop...

http://www.wired.com/wiredscience/2012/12/so-about-that-glowing-cigarette/

true, higher Ph is better for keeping the metals put. I wonder if a lower pH would be what is wanted if attempting biomediation. The water acts as a solvent.

Tom Davis wrote:http://www.nytimes.com/2011/07/21/science/earth/21fishbones.html?pagewanted=all
The fish bones are full of calcium phosphate, he said. As they degrade, the phosphates migrate into the soil. The lead in the soil, deposited by car exhaust from the decades when gasoline contained lead or from lead-based paint residue, binds with the phosphate and transforms into pyromorphite, a crystalline mineral that will not harm anyone even if consumed

Maybe monitor your ph levels too.
I have heard, on his latest video, Geoff Lawton say that if ph drops below 4.5 then uptake of the heavy metals by the plants can occur.
He also said that large amounts of mulch will buffer acid rain events which might drop the ph of the soil to dangerous levels.
That is what I gleaned from listening to this
Ask an Expert in Permaculture

Fungus/Mushroom can breakdown compounds like oil or even plastic.
However they can not breakdown Carbon/Lead/Oxygen/Arsenic aka heavy metals into something simpler
such as protons/quarks/etc.

Whatever organism you use dont eat it or move it to another part of your property move it to a land fill.
Leaves and Nuts have high levels of minerals/heavy metals, So I would be very cautious about eating any.
Alot of people in cities (due to lead paint contamination) plant in containers/raised bed with imported soil for this reason.
You could always go the aquaponic route too.

Can somoene clarify this? Isn't this apples and oranges? phosphorous from fertilizers used on teh fields increased concentraiosn of lead in the plant, but phosphorous from bones is supposedly in a different form that binds the lead in a non-bioavailable, inert form that you can eat and not be affected by. Is there something I'm missing? Thanks!!!

Morgan Morrigan wrote:this says the phosphate isn't doing just that.

tabacco turns out to be a good catch crop...

http://www.wired.com/wiredscience/2012/12/so-about-that-glowing-cigarette/

Joshua, what you are missing is that lead has a wide range of bioavailability, depending on what it is complexed with. When gasoline was made with tetra-ethyl lead, that lead went through the engine where it was oxidized to lead oxide and was then shot out the exhaust pipe. Net result was lots of lead oxide being deposited in the soils along heavily traveled highways. Now while lead oxide is a stable compound, it can be attacked and dissolved by acids, including humic acids in the soil. So that was bioavailable lead. Contrast that with the mineral galena, which is lead (II) sulfide. Galena is insoluble in water and is resistant to attack by mineral acids. You need to use an oxidizing acid like nitric acid to attack the mineral and get the lead into solution.

The pyromorphite that was mentioned is another complex of lead that is practically insoluble. Table 1 in this reference has the solubility product of some common lead compounds. Notice that lead oxide is fairly high, consistent with that I said about leaded gasoline exhaust. And pyromorphite is quite negative, meaning that if you swallowed it, it is going to pass right through and not be absorbed.

Also complicating things is that there is not just one complex of lead to consider, but many minerals that can bind it and keep it bound. Bottom line for Permies? Lead gets irreversibly bound up in soils with appreciable amounts of iron, aluminum and phosphate -- just the things that a clay soil that has compost added to it is going to be rich in.

John Elliott wrote:

Also complicating things is that there is not just one complex of lead to consider, but many minerals that can bind it and keep it bound. Bottom line for Permies? Lead gets irreversibly bound up in soils with appreciable amounts of iron, aluminum and phosphate -- just the things that a clay soil that has compost added to it is going to be rich in.

Perhaps I am being a bit paranoid, but if I had some lead polluted soil to grow a garden in and someone, even someone as knowledgable as you, told me that by adding some extra minerals, the lead would chemically bond with said minerals into harmless compounds, I don't know that I could bring myself to eat the crops from that soil. It feels about the same as my friend telling me "take this gun, put it to your head and pull the trigger. Don't worry. It isn't loaded".

There are many questions that come to mind. Perhaps you can answer them. How much of each mineral must be added to the soil to counteract (x amount) of lead? What conditions need to be present for the lead to bond to these minerals? I'm not a chemist but i know that certain reactions only happen at certain temperature ranges or in the presence of certain enzymes. How long does it take for these bonds to form? Explosions are an instantaneous reaction whereas iron bonding with oxygen (rust) happens over a long period of time. I would have to ascertain how deep down in the soil the lead has reached and ensure that appropriate quantities of these remediating minerals get down there. Otherwise deep tap roots might bring those heavy metals up into their edible leaves and ultimately end up in my body.

You seem pretty knowledgable in this aspect. Can you answer any of these questions? Are these concerns legitimate or are the quantities, conditions, time and depth negligible?

I guess the quantity of heavy metals in your soil is relevant too. We are exposed to heavy metals every day and a lot of conventionally grown crops and animal products have "acceptable" amounts of heavy metals present as well. If the soil contamination is not REALLY heavy, your still probably better off growing your food there than you are buying it from the store.

dan long wrote:
Perhaps I am being a bit paranoid, but if I had some lead polluted soil to grow a garden in and someone, even someone as knowledgable as you, told me that by adding some extra minerals, the lead would chemically bond with said minerals into harmless compounds, I don't know that I could bring myself to eat the crops from that soil. It feels about the same as my friend telling me "take this gun, put it to your head and pull the trigger. Don't worry. It isn't loaded".

I can understand the source of your paranoia. When you know a little about something, that it has the potential to be dangerous, you want to keep it as far away as possible. However, the more you learn, about the extent of the dangers, where the boundaries are, how it can be safely handled, what makes it unsafe, then you can go from paranoia to healthy respect. I have a healthy respect for heavy metals, radionuclides, poisonous fungi, etc.

There are many questions that come to mind. Perhaps you can answer them. How much of each mineral must be added to the soil to counteract (x amount) of lead? What conditions need to be present for the lead to bond to these minerals? I'm not a chemist but i know that certain reactions only happen at certain temperature ranges or in the presence of certain enzymes. How long does it take for these bonds to form? Explosions are an instantaneous reaction whereas iron bonding with oxygen (rust) happens over a long period of time. I would have to ascertain how deep down in the soil the lead has reached and ensure that appropriate quantities of these remediating minerals get down there. Otherwise deep tap roots might bring those heavy metals up into their edible leaves and ultimately end up in my body.

You seem pretty knowledgable in this aspect. Can you answer any of these questions? Are these concerns legitimate or are the quantities, conditions, time and depth negligible?

The first question to address is "is this heavy metal a problem in your area?" If you live in Leadville, Colorado, then yes, you ought to be reading up on the subject of lead as well as getting your soil tested by the county agriculture extension. If you live in Georgia, then heavy metal accumulation is really not something to worry about. This alluvial plain and the heavy clay that washed down from the Appalachians over millions of years long ago covered over any ores of lead, arsenic and mercury. Of course, there could be an industrial plant that re-contaminated a certain locale, there is one of those across the river in South Carolina. What do you know about hard rock mines in your area and the industrial processes that were carried out since the Industrial Revolution started? What is your evidence that you have a problem with your soil?

Precipitation and chelating reactions are closer to the explosion timescale than they are to the rusting timescale. Suppose you take a sample from a wetland and it has 30 ppb of lead in it. That would be twice the EPA limit for lead in drinking water. If you apply a chelating or precipitation agent and come back a week later, you should see a marked reduction in the level of lead you can measure, and that will help to calibrate you on just how much more remediation is required. It also makes a difference if it is naturally occurring or if it was the case of an industrial chemical spill. In the former, you might need to do some long term phyto- or myco-remediation to sequester the metals. In the case of the latter, you have a better idea of the source -- maybe you can even map it -- and you can perform chemical treatments designed to bind with the pollutants and remove them from the biosphere.

I should make an aside here that parts-per-million (ppm) and parts-per-billion (ppb) are the way that EPA communicates with the permies, but to do real chemistry, you are going to have to convert these units to something that chemists use, molarity. The solubility products in the reference I gave in my last post are calculated using the molar concentration of lead and its counter ion.

Your concerns are legitimate. One of the things that makes me cringe is the way that China has developed its industry over the last 30 years, largely without paying attention to these issues. There are places in China with naturally high levels of arsenic in the soils. There are other places with naturally high levels of fluoride. What they have done is go for all out development without asking questions like "if we mine X here, how much pollution will that cause and what do we have to do to mitigate it?" If you ask questions like that, you can plan for how it is going to affect the food you grow.

On edit: I'd like to add this USGS map of surface arsenic concentrations. For those of you that are wondering whether you should be concerned.

Wow! Thank you. So are you saying you yourself eat food you grew in soil that had had bioavailable lead and which you then bound up with compost? is anyone doing this? The argument makes logical sense, but direct experience trumps that for me. Thanks so much. I think I'm getting a chemistry degree just by poking around on this website!

John Elliott wrote:Joshua, what you are missing is that lead has a wide range of bioavailability, depending on what it is complexed with. When gasoline was made with tetra-ethyl lead, that lead went through the engine where it was oxidized to lead oxide and was then shot out the exhaust pipe. Net result was lots of lead oxide being deposited in the soils along heavily traveled highways. Now while lead oxide is a stable compound, it can be attacked and dissolved by acids, including humic acids in the soil. So that was bioavailable lead. Contrast that with the mineral galena, which is lead (II) sulfide. Galena is insoluble in water and is resistant to attack by mineral acids. You need to use an oxidizing acid like nitric acid to attack the mineral and get the lead into solution.

The pyromorphite that was mentioned is another complex of lead that is practically insoluble. Table 1 in this reference has the solubility product of some common lead compounds. Notice that lead oxide is fairly high, consistent with that I said about leaded gasoline exhaust. And pyromorphite is quite negative, meaning that if you swallowed it, it is going to pass right through and not be absorbed.

Also complicating things is that there is not just one complex of lead to consider, but many minerals that can bind it and keep it bound. Bottom line for Permies? Lead gets irreversibly bound up in soils with appreciable amounts of iron, aluminum and phosphate -- just the things that a clay soil that has compost added to it is going to be rich in.

Close to the house there would be as well lead from paint which is another lead than from car exhausts and another one which comes from mining and industry - am I right?
What I would do is to follow what John says get a proper soil test done if you haven't done that already. Grow some crops and test the crops especially those which are known to uptake lead.

Joshua Myrvaagnes wrote: So are you saying you yourself eat food you grew in soil that had had bioavailable lead and which you then bound up with compost?

Oh no. I'm retired and no longer have access to a fully instrumented chemical laboratory. I just have to wing it and go on my best gut feeling without the benefit of laboratory data with known error bars.

Like the map shows, the southeast is very low in soil arsenic (for the reasons I mentioned) -- so I don't worry about it. Same with lead. On the other hand, the soils here are low in boron (for pretty much the same reason, it gets leached away), so I have an ongoing program to add boron to my compost teas, mulches. I spray my fruit trees in late winter to get some boron on the buds where it will do some good. I think I hit it right this year, because this is the first year the apple trees have had a decent crop. But I have no quantitative data to back up what I am doing. For all I know, the patron saint of arachnids is smiling down on me for my husbandry of garden spiders and rewarding me with some apples.

Great questions, Dan!

Raises more questions, if you're willing. If you write an ebook on this, I'd buy it, it's definitely important info and something that's held LOTS of people back, I am pretty sure, from gardening or getting started in permaculture, even if they weren't fully conscious of it, just that thought in the back of the mind "but what about lead paint?" Any barriers that can be removed, it's good.

So, here's my situation. I have what Umass lab tells me is 454 ppm "_soluble_" lead, and they say that that indicates over 2,000 ppm of total lead. I am in an urban, urban, suburban area (Somerville has the highest population density of any city, I've heard(?)). The City of Cambridge next door puts out a flier that says "if you have a house older than 1985, get your lead levels tested or garden in raised beds, don't grow in soil above I think it was 400 ppm" --something I was definitely way over the limit for. The lead ironically is HIGHER farther away from the house in the back yard than in the front bed. Someone MAY have had an apple tree there years ago and MAY have had hte bright idea, "let's spray lead-arsenic pesticide on this sucker. What could possibly go wrong?" even though they KNEW back then that lead was poisonous, this didn't just get discovered in the 80s when kids had been eating paint chips and pencils for decades. Mmmmm, that sweet sweet taste of lead. I don't have any proof of this, but I am not near a major highway or even that big a road, there's a whole mini-park between my back yard and the small road. The road in front is a dead end and narrow narrow, so hardly anyone ever drives on it. I know, I'm spoiled silly, right? I have the quietest place to live in Somerville.

SO:

--do I pay attention to what the lab says is "soluble"? does "soluble" mean anything? does it have any correlation to bioavailability? does their estimate of total lead mean anything?
--what chelating agent would you say to apply in my case? is calcium phosphate chelating or just "binding"? is compost an acceptable one? can "apply" mean just put it on top (of my mulch) and let it gradually work in over the course of a year? how much compost per "ppm" or per mole of lead--ballpark high figure?
--will the lead test tell me how much is now bioavailable? do I need to just do a plant tissue sample? if I use a home lead-test kit with a leaf will that give me an accurate enough test that you'd trust it?
--if I test a leaf of, say a sunflower and of a raspberry plant and a comfrey, will that give me a sense of the range of what's getting into a leaf?
--what's a genuinely safe level of lead in a plant tissue for human consumption, in your opinion?


One more clue--there was a weird bumpy area of land my landlord (who's blind, but probably correct) says was pushed over from the neighbors and dumped on her yard when there wa sconstrustion years ago. That part tested separately (I spent a good deal of money on lead tests) had LOWER lead than the back yard--450 instead of 700.

And yes, I followed the instructions for the lead test, 12" deep samples, mixed around, dried them out, kept them separate and not in a lead or kryptonite container.


Thanks so much!!! really, I'm blown away by the freakin USEFULNESS of this website! I am pinching myself in wonder.

John Elliott wrote:

dan long wrote:
Perhaps I am being a bit paranoid, but if I had some lead polluted soil to grow a garden in and someone, even someone as knowledgable as you, told me that by adding some extra minerals, the lead would chemically bond with said minerals into harmless compounds, I don't know that I could bring myself to eat the crops from that soil. It feels about the same as my friend telling me "take this gun, put it to your head and pull the trigger. Don't worry. It isn't loaded".

I can understand the source of your paranoia. When you know a little about something, that it has the potential to be dangerous, you want to keep it as far away as possible. However, the more you learn, about the extent of the dangers, where the boundaries are, how it can be safely handled, what makes it unsafe, then you can go from paranoia to healthy respect. I have a healthy respect for heavy metals, radionuclides, poisonous fungi, etc.

There are many questions that come to mind. Perhaps you can answer them. How much of each mineral must be added to the soil to counteract (x amount) of lead? What conditions need to be present for the lead to bond to these minerals? I'm not a chemist but i know that certain reactions only happen at certain temperature ranges or in the presence of certain enzymes. How long does it take for these bonds to form? Explosions are an instantaneous reaction whereas iron bonding with oxygen (rust) happens over a long period of time. I would have to ascertain how deep down in the soil the lead has reached and ensure that appropriate quantities of these remediating minerals get down there. Otherwise deep tap roots might bring those heavy metals up into their edible leaves and ultimately end up in my body.

You seem pretty knowledgable in this aspect. Can you answer any of these questions? Are these concerns legitimate or are the quantities, conditions, time and depth negligible?

The first question to address is "is this heavy metal a problem in your area?" If you live in Leadville, Colorado, then yes, you ought to be reading up on the subject of lead as well as getting your soil tested by the county agriculture extension. If you live in Georgia, then heavy metal accumulation is really not something to worry about. This alluvial plain and the heavy clay that washed down from the Appalachians over millions of years long ago covered over any ores of lead, arsenic and mercury. Of course, there could be an industrial plant that re-contaminated a certain locale, there is one of those across the river in South Carolina. What do you know about hard rock mines in your area and the industrial processes that were carried out since the Industrial Revolution started? What is your evidence that you have a problem with your soil?

Precipitation and chelating reactions are closer to the explosion timescale than they are to the rusting timescale. Suppose you take a sample from a wetland and it has 30 ppb of lead in it. That would be twice the EPA limit for lead in drinking water. If you apply a chelating or precipitation agent and come back a week later, you should see a marked reduction in the level of lead you can measure, and that will help to calibrate you on just how much more remediation is required. It also makes a difference if it is naturally occurring or if it was the case of an industrial chemical spill. In the former, you might need to do some long term phyto- or myco-remediation to sequester the metals. In the case of the latter, you have a better idea of the source -- maybe you can even map it -- and you can perform chemical treatments designed to bind with the pollutants and remove them from the biosphere.

I should make an aside here that parts-per-million (ppm) and parts-per-billion (ppb) are the way that EPA communicates with the permies, but to do real chemistry, you are going to have to convert these units to something that chemists use, molarity. The solubility products in the reference I gave in my last post are calculated using the molar concentration of lead and its counter ion.

Your concerns are legitimate. One of the things that makes me cringe is the way that China has developed its industry over the last 30 years, largely without paying attention to these issues. There are places in China with naturally high levels of arsenic in the soils. There are other places with naturally high levels of fluoride. What they have done is go for all out development without asking questions like "if we mine X here, how much pollution will that cause and what do we have to do to mitigate it?" If you ask questions like that, you can plan for how it is going to affect the food you grow.

On edit: I'd like to add this USGS map of surface arsenic concentrations. For those of you that are wondering whether you should be concerned.

I know that I might get heckled as being a shill for Coca-Cola, but this paper suggests that drinking cola with your paint chips or lead contaminated foods might just do the trick by forming insoluble pyromorphite in vitro.

And you thought all it was good for was rotting your teeth.


To do list: Calculate amount of Coca-Cola needed to precipitate 454 ppm of soluble lead.

Hmpf. I am NOT pouring coke on my garden. It might cure the disease but it will most certainly kill most of the patients. But is there a form of phosphoric acid available that's not in a soft drink? Thanks!

John Elliott wrote:I know that I might get heckled as being a shill for Coca-Cola, but this paper suggests that drinking cola with your paint chips or lead contaminated foods might just do the trick by forming insoluble pyromorphite in vitro.

And you thought all it was good for was rotting your teeth.


To do list: Calculate amount of Coca-Cola needed to precipitate 454 ppm of soluble lead.

Joshua Myrvaagnes wrote: But is there a form of phosphoric acid available that's not in a soft drink? Thanks!

Two possibilities: 1) If you make your own biochar, put bones in with the biomass that you are charring. By having bone char in with your biochar, you have a source of phosphate ion that can leach into the soil and bind up any soluble lead.

2) If you think that is too slow, because leaching the phosphate out of the bone char is a slow process, you can get the phosphate into solution as phosphoric acid by soaking the bones in vinegar:

Ca3(PO4)2 + 6CH3COOH -----> 3 Ca(CH3COO)2 + 2 H3PO4

bones + vinegar -----> calcium acetate + phosphoric acid

John Elliott wrote:

Joshua Myrvaagnes wrote: But is there a form of phosphoric acid available that's not in a soft drink? Thanks!

Two possibilities: 1) If you make your own biochar, put bones in with the biomass that you are charring. By having bone char in with your biochar, you have a source of phosphate ion that can leach into the soil and bind up any soluble lead.

2) If you think that is too slow, because leaching the phosphate out of the bone char is a slow process, you can get the phosphate into solution as phosphoric acid by soaking the bones in vinegar:

Ca3(PO4)2 + 6CH3COOH -----> 3 Ca(CH3COO)2 + 2 H3PO4

bones + vinegar -----> calcium acetate + phosphoric acid

I like that chemistry...not sure if it's correct, but it sounds good.

I remember using a 'jelly' paint stripper that was phosphoric acid based. Not that you want to pour that on your garden...You could maybe dilute it tho.

THE RESULTS ARE IN--and here are the nominations for lowest lead levels....

I got plant tissue results back for sunchokes (leaves) and collards (leaves)

I chose these because

collards: I want to eat them, and they are a worst-case scenario as they are brassicas; maybe not the most accumulating brassicas, but the ones I like best to eat.
results: lead 0.00 ppm. (at most that could possibly be 4.9 parts per billion, within the range I think FDA has for lead of 1,000 parts per billion in foods).
!!! woohoo!

sunchokes (Jerusalem artichoke): for biomass, and to get a read on the soil's current lead-supplying propensity
results: 2.20 ppm.
Now, that's not good for eating, 2,209 pp billion ostensibly. BUT people are always saying "just add biomass" and this quantifies that. Imagine I had soil that had 2ppm of lead, then I wouldn't even be blabbing on this thread here. I'd be completely carefree about lead. So, if I put my sunchoke leaves back in as compost I'm golden. the biomass is good enough for soil by far. And so whatever other lead is in there is either a) not bioavailable b) not interesting to plants because they have enough of other better material to work with or c) some other how not an issue, even to a lead accumulator like a sunchoke.
I don't know how their roots are doing for lead, but a) I figure I'd eat them only in an emergency, for a short time-period, if I need to and b) the lab doesn't accept root samples, only leaf, so Idk what i'd do. But I can use the home lead-test kit I suppose to find out if there are egregious concentrations of lead in it.

What was also fascinating:
sunchokes were really lacking in molybdenum, almost got none!
and low in nitrogen, despite having compost put down and a couple of nitrogen fixers (legumes) planted in there
while the collards (this is all in the same tiny tiny front yard area, about 6' x 25' between the house and the sidewalk) had sufficient molybdenum--in healthy range--and decent nitrogen.

Both had elevated zinc and calcium.

Joshua Myrvaagnes wrote:Great questions, Dan!

Raises more questions, if you're willing. If you write an ebook on this, I'd buy it, it's definitely important info and something that's held LOTS of people back, I am pretty sure, from gardening or getting started in permaculture, even if they weren't fully conscious of it, just that thought in the back of the mind "but what about lead paint?" Any barriers that can be removed, it's good.

So, here's my situation. I have what Umass lab tells me is 454 ppm "_soluble_" lead, and they say that that indicates over 2,000 ppm of total lead. I am in an urban, urban, suburban area (Somerville has the highest population density of any city, I've heard(?)). The City of Cambridge next door puts out a flier that says "if you have a house older than 1985, get your lead levels tested or garden in raised beds, don't grow in soil above I think it was 400 ppm" --something I was definitely way over the limit for. The lead ironically is HIGHER farther away from the house in the back yard than in the front bed. Someone MAY have had an apple tree there years ago and MAY have had hte bright idea, "let's spray lead-arsenic pesticide on this sucker. What could possibly go wrong?" even though they KNEW back then that lead was poisonous, this didn't just get discovered in the 80s when kids had been eating paint chips and pencils for decades. Mmmmm, that sweet sweet taste of lead. I don't have any proof of this, but I am not near a major highway or even that big a road, there's a whole mini-park between my back yard and the small road. The road in front is a dead end and narrow narrow, so hardly anyone ever drives on it. I know, I'm spoiled silly, right? I have the quietest place to live in Somerville.

SO:

--do I pay attention to what the lab says is "soluble"? does "soluble" mean anything? does it have any correlation to bioavailability? does their estimate of total lead mean anything?
--what chelating agent would you say to apply in my case? is calcium phosphate chelating or just "binding"? is compost an acceptable one? can "apply" mean just put it on top (of my mulch) and let it gradually work in over the course of a year? how much compost per "ppm" or per mole of lead--ballpark high figure?
--will the lead test tell me how much is now bioavailable? do I need to just do a plant tissue sample? if I use a home lead-test kit with a leaf will that give me an accurate enough test that you'd trust it?
--if I test a leaf of, say a sunflower and of a raspberry plant and a comfrey, will that give me a sense of the range of what's getting into a leaf?
--what's a genuinely safe level of lead in a plant tissue for human consumption, in your opinion?


One more clue--there was a weird bumpy area of land my landlord (who's blind, but probably correct) says was pushed over from the neighbors and dumped on her yard when there wa sconstrustion years ago. That part tested separately (I spent a good deal of money on lead tests) had LOWER lead than the back yard--450 instead of 700.

And yes, I followed the instructions for the lead test, 12" deep samples, mixed around, dried them out, kept them separate and not in a lead or kryptonite container.


Thanks so much!!! really, I'm blown away by the freakin USEFULNESS of this website! I am pinching myself in wonder.

John Elliott wrote:

dan long wrote:

Editing to add:

first year, soil test: 600+ppm; planted sunflowers (Russian Mammoth) every 2 feet, some died so replaced with sunchokes. sunflowers (sunchokes are close relative) are used for lead or arsenic or other heavy metal remediation--they accumulate lead from the soil. We cut the sunchokes down and uprooted the sunflowers and put them in the landfill (sadly).

second year--practice garden, planted some collards and a few other veggies and fruits. Sunchokes grew back (and were fruitful and multiplied).

was going to do another soil test BUT with the discussion of binding lead in an inert form--lead apatite, lead+calcium phosphate--and "just add compost, it'll be fine"--I thought well the lead number in the soil means nothing. What's the lead level in the plant tissue itself, the part that we actually care about because we're going to eat? So I tested the brassica (they're lead accumulators) that we want to eat, and the sunchokes (we'd like to eat the root but the lab would only test leaf, and this was useful since it lets me know if they should be thrown in the landfill or can be useful biomass--compost. Biomass by a long shot!)

the test results are attached at the bottom of the post here.

Joshua Myrvaagnes wrote:THE RESULTS ARE IN--and here are the nominations for lowest lead levels....

I got plant tissue results back for sunchokes (leaves) and collards (leaves)

I chose these because

collards: I want to eat them, and they are a worst-case scenario as they are brassicas; maybe not the most accumulating brassicas, but the ones I like best to eat.
results: lead 0.00 ppm. (at most that could possibly be 4.9 parts per billion, within the range I think FDA has for lead of 1,000 parts per billion in foods).
!!! woohoo!

sunchokes (Jerusalem artichoke): for biomass, and to get a read on the soil's current lead-supplying propensity
results: 2.20 ppm.
Now, that's not good for eating, 2,209 pp billion ostensibly. BUT people are always saying "just add biomass" and this quantifies that. Imagine I had soil that had 2ppm of lead, then I wouldn't even be blabbing on this thread here. I'd be completely carefree about lead. So, if I put my sunchoke leaves back in as compost I'm golden. the biomass is good enough for soil by far. And so whatever other lead is in there is either a) not bioavailable b) not interesting to plants because they have enough of other better material to work with or c) some other how not an issue, even to a lead accumulator like a sunchoke.
I don't know how their roots are doing for lead, but a) I figure I'd eat them only in an emergency, for a short time-period, if I need to and b) the lab doesn't accept root samples, only leaf, so Idk what i'd do. But I can use the home lead-test kit I suppose to find out if there are egregious concentrations of lead in it.

What was also fascinating:
sunchokes were really lacking in molybdenum, almost got none!
and low in nitrogen, despite having compost put down and a couple of nitrogen fixers (legumes) planted in there
while the collards (this is all in the same tiny tiny front yard area, about 6' x 25' between the house and the sidewalk) had sufficient molybdenum--in healthy range--and decent nitrogen.

Both had elevated zinc and calcium.

Joshua Myrvaagnes wrote:Great questions, Dan!

Raises more questions, if you're willing. If you write an ebook on this, I'd buy it, it's definitely important info and something that's held LOTS of people back, I am pretty sure, from gardening or getting started in permaculture, even if they weren't fully conscious of it, just that thought in the back of the mind "but what about lead paint?" Any barriers that can be removed, it's good.

So, here's my situation. I have what Umass lab tells me is 454 ppm "_soluble_" lead, and they say that that indicates over 2,000 ppm of total lead. I am in an urban, urban, suburban area (Somerville has the highest population density of any city, I've heard(?)). The City of Cambridge next door puts out a flier that says "if you have a house older than 1985, get your lead levels tested or garden in raised beds, don't grow in soil above I think it was 400 ppm" --something I was definitely way over the limit for. The lead ironically is HIGHER farther away from the house in the back yard than in the front bed. Someone MAY have had an apple tree there years ago and MAY have had hte bright idea, "let's spray lead-arsenic pesticide on this sucker. What could possibly go wrong?" even though they KNEW back then that lead was poisonous, this didn't just get discovered in the 80s when kids had been eating paint chips and pencils for decades. Mmmmm, that sweet sweet taste of lead. I don't have any proof of this, but I am not near a major highway or even that big a road, there's a whole mini-park between my back yard and the small road. The road in front is a dead end and narrow narrow, so hardly anyone ever drives on it. I know, I'm spoiled silly, right? I have the quietest place to live in Somerville.

SO:

--do I pay attention to what the lab says is "soluble"? does "soluble" mean anything? does it have any correlation to bioavailability? does their estimate of total lead mean anything?
--what chelating agent would you say to apply in my case? is calcium phosphate chelating or just "binding"? is compost an acceptable one? can "apply" mean just put it on top (of my mulch) and let it gradually work in over the course of a year? how much compost per "ppm" or per mole of lead--ballpark high figure?
--will the lead test tell me how much is now bioavailable? do I need to just do a plant tissue sample? if I use a home lead-test kit with a leaf will that give me an accurate enough test that you'd trust it?
--if I test a leaf of, say a sunflower and of a raspberry plant and a comfrey, will that give me a sense of the range of what's getting into a leaf?
--what's a genuinely safe level of lead in a plant tissue for human consumption, in your opinion?


One more clue--there was a weird bumpy area of land my landlord (who's blind, but probably correct) says was pushed over from the neighbors and dumped on her yard when there wa sconstrustion years ago. That part tested separately (I spent a good deal of money on lead tests) had LOWER lead than the back yard--450 instead of 700.

And yes, I followed the instructions for the lead test, 12" deep samples, mixed around, dried them out, kept them separate and not in a lead or kryptonite container.


Thanks so much!!! really, I'm blown away by the freakin USEFULNESS of this website! I am pinching myself in wonder.

John Elliott wrote:

dan long wrote:

Here is an article with some good recommendations for removing lead:
http://www.examiner.com/list/7-plants-that-naturally-remove-lead-from-your-soil

Thanks John.

Here's an idea: put in raised beds, with spaces among them of just a few inches (maybe 4-6) and plant sunflowers there. The roots of the sunflower spread out pretty good. The other accumulators don't do nearly as much "rooting about" in the soil as sunflowers (giant/mammoth russian especially). These guys make a root ball kind of thing at least 6" long and 3" thick, and then rootlets extend all around from there.



The article is good, nothing shocking--they have the usual suspects: sunflowers, grains, mustard greens, brassicas; one for wetlands; and, new to me, ragweed!

John Polk wrote:Here is an article with some good recommendations for removing lead:
http://www.examiner.com/list/7-plants-that-naturally-remove-lead-from-your-soil

Quoted from link: Ragweed is considered by many to be the single best plant that exists for removing lead from contaminated soil.

That, in itself makes it a powerful contender for lead mitigation.
Just try to terminate it before it goes to flower or else it becomes 'sneeze weed'.
Its allergic nature does not manifest itself until it produces pollen.

I've been toying with doing a soil test for lead, etc.  But they all seem to be really pricey.

A bit of searching took me to https://www.vox.com/a/lead-exposure-risk-map, which charts U.S. lead-in-soil risk by almost a per-neighborhood level.  Naturally it is worst in the inner cities (lead paint was not banned 'til 1978).  Here's a sample:



But my piece of suburbia turned out to be low-risk and the houses were built in the '90s.  So I think I'll skip the test and just put the $200 into organic matter and good plants.  

I do have concerns about eating crops from polluted soil... but in the end I have to think my own garden, managed by me, is overall going to be a lot less risky than what comes from supermarket.

Here also is a U.S. map for arsenic, though not as granular: https://pubs.acs.org/doi/full/10.1021/acs.est.7b02881