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"...far cheaper strategy: capping current soils with clean soils and/or mulch" Oh yes, cover the thing up and let someone else deal with it. The same strategy

"...far cheaper strategy: capping current soils with clean soils and/or mulch" Oh yes, cover the thing up and let someone else deal with it. The same strategy employed for years with lead paint. We can either spend billions covering it up over and over again, or we can deal with it once and be done.

JumpCrisscross 2y ago
> or we can deal with it once and be done What does this mean? Dismantling the community and replacing everything above the bedrock?
- maxbond 2y ago
  You could probably decontaminate the soil in place by cultivating plants that bioaccumulate the lead, harvesting them, burning them, and then disposing of a relatively small volume of ash into which the lead had been concentrated. There's sure to be complications, I can think of a few and I'm not an expert, but you wouldn't necessarily have to rip out everything.
  - JumpCrisscross 2y ago
    > could probably decontaminate the soil in place by cultivating plants that bioaccumulate the lead, harvesting them, burning them, and then disposing of a relatively small volume of ash into which the lead had been concentrated Is this a random guess or based on anything? What rate does it remove at? You’ll need to depopulate a quarter of American housing during that period. Are we sure none of the lead will emerge in the volatiles from burning?
    - maxbond 2y ago
      Based on coursework I did years ago. I could've given you more information back then but it's been a while. You would definitely need to look into the lead coming out the chimney; if it does, you just dry the material and accept less concentration. (Or use a more complex technology like a molten salt reactor to keep it from escaping the chimney, but if it's eg concentrating in the leaves, drying it out is probably almost as effective as burning it.) You only need to kick people out of their homes if the soil is so dangerous they can't live there anyway. You're not disturbing the soil more than gardening would. There would definitely be huge challenges, my main point is that it's a naive assumption that you necessarily have to relocate people to remediate the soil. It doesn't necessarily have to work quickly as much as steadily. If you can do it in 10 years by relocating people and 100 years without, it probably makes sense to go the slow route and the soil will get less and less dangerous all the time. If you're curious, you might look up bioremediation and biomining.
      - JumpCrisscross 2y ago
        > only need to kick people out of their homes if the soil is so dangerous they can't live there anyway The article is specifically about unsafe lead levels. > If you can do it in 10 years by relocating people and 100 years without, it probably makes sense to go the slow route and the soil will get less and less dangerous all the time Versus just covering it up? What kind of cost-benefit analysis does that pass? All kinds of toxic substances exist below the top soil. I agree it would be nice if we could poof away the problem. But given its scale, that’s not a real option. (For context, if we can do this we can solve the housing crisis.)
        maxbond 2y ago
        The context is that someone suggested that covering it up is only temporary, right? That would depend on local conditions, but presumably in some places it's true (due to eg how the topsoil is eroding in that area). You suggested that the cost would be basically infinite because of how many people it displaces. I'm pointing out that your assumptions may have been too conservative, and that it's probably merely hundreds of billions spread over decades. Is that a good use of resources? I don't have the data to form that opinion, and I'm not going to gather it for a casual Internet conversation, so I just don't know.
    - onlypassingthru 2y ago
      Plant lots and lots of sunflowers. Sunflowers will remove all sorts of metals from the soil.[0] Then you just have to dispose of them like regular garbage. [0]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5402931/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5402931/
zdragnar 2y ago
Poorly remediating lead paint is more dangerous than just painting over it. Same thing is true with asbestos. Capping leaded soil isn't great, in that you can't look at dirt and guess that it's old enough to probably be bad the way you can with paint or tile, and many plants tend to have deep roots that'll suck the lead right back up to the surface. That said, so long as it is disclosed properly to future occupants, it's better than doing a bad job (accidentally or otherwise) and telling everyone it's been taken care of.
_heimdall 2y ago
This is likely an over simplification. Adding healthy soil, compost, and/or wood chips promotes bacterial and fungal activity. I'd rather people didn't bury garbage, and bacteria won't eat glass anytime soon, but it isn't as simple as assuming that covering waste in wood chipsakes it someone else's problem.
marklubi 2y ago
> Oh yes, cover the thing up and let someone else deal with it. The same strategy employed for years with lead paint. If lead paint is sequestered, it poses no threat. When you start trying to scrape all of it off and replace it is the point at which you've now exposed yourself and everyone that might inhale some of that dust. Same thing with asbestos. As long as it's somewhere that you won't inhale/ingest it, there isn't a problem. Asbestos brake pads, problem. Asbestos siding on a house, only a problem if you're doing construction that disrupts it. Similarly, if you have a location with high levels of lead in the dirt or are concerned about it, perhaps you should import soil and do some raised bed planting.

JumpCrisscross 2y ago

> or we can deal with it once and be done What does this mean? Dismantling the community and replacing everything above the bedrock?

maxbond 2y ago
You could probably decontaminate the soil in place by cultivating plants that bioaccumulate the lead, harvesting them, burning them, and then disposing of a relatively small volume of ash into which the lead had been concentrated. There's sure to be complications, I can think of a few and I'm not an expert, but you wouldn't necessarily have to rip out everything.
- JumpCrisscross 2y ago
  > could probably decontaminate the soil in place by cultivating plants that bioaccumulate the lead, harvesting them, burning them, and then disposing of a relatively small volume of ash into which the lead had been concentrated Is this a random guess or based on anything? What rate does it remove at? You’ll need to depopulate a quarter of American housing during that period. Are we sure none of the lead will emerge in the volatiles from burning?
  - maxbond 2y ago
    Based on coursework I did years ago. I could've given you more information back then but it's been a while. You would definitely need to look into the lead coming out the chimney; if it does, you just dry the material and accept less concentration. (Or use a more complex technology like a molten salt reactor to keep it from escaping the chimney, but if it's eg concentrating in the leaves, drying it out is probably almost as effective as burning it.) You only need to kick people out of their homes if the soil is so dangerous they can't live there anyway. You're not disturbing the soil more than gardening would. There would definitely be huge challenges, my main point is that it's a naive assumption that you necessarily have to relocate people to remediate the soil. It doesn't necessarily have to work quickly as much as steadily. If you can do it in 10 years by relocating people and 100 years without, it probably makes sense to go the slow route and the soil will get less and less dangerous all the time. If you're curious, you might look up bioremediation and biomining.
    - JumpCrisscross 2y ago
      > only need to kick people out of their homes if the soil is so dangerous they can't live there anyway The article is specifically about unsafe lead levels. > If you can do it in 10 years by relocating people and 100 years without, it probably makes sense to go the slow route and the soil will get less and less dangerous all the time Versus just covering it up? What kind of cost-benefit analysis does that pass? All kinds of toxic substances exist below the top soil. I agree it would be nice if we could poof away the problem. But given its scale, that’s not a real option. (For context, if we can do this we can solve the housing crisis.)
      - maxbond 2y ago
        The context is that someone suggested that covering it up is only temporary, right? That would depend on local conditions, but presumably in some places it's true (due to eg how the topsoil is eroding in that area). You suggested that the cost would be basically infinite because of how many people it displaces. I'm pointing out that your assumptions may have been too conservative, and that it's probably merely hundreds of billions spread over decades. Is that a good use of resources? I don't have the data to form that opinion, and I'm not going to gather it for a casual Internet conversation, so I just don't know.
  - onlypassingthru 2y ago
    Plant lots and lots of sunflowers. Sunflowers will remove all sorts of metals from the soil.[0] Then you just have to dispose of them like regular garbage. [0]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5402931/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5402931/

zdragnar 2y ago

Poorly remediating lead paint is more dangerous than just painting over it. Same thing is true with asbestos. Capping leaded soil isn't great, in that you can't look at dirt and guess that it's old enough to probably be bad the way you can with paint or tile, and many plants tend to have deep roots that'll suck the lead right back up to the surface. That said, so long as it is disclosed properly to future occupants, it's better than doing a bad job (accidentally or otherwise) and telling everyone it's been taken care of.

_heimdall 2y ago

This is likely an over simplification. Adding healthy soil, compost, and/or wood chips promotes bacterial and fungal activity. I'd rather people didn't bury garbage, and bacteria won't eat glass anytime soon, but it isn't as simple as assuming that covering waste in wood chipsakes it someone else's problem.

marklubi 2y ago

> Oh yes, cover the thing up and let someone else deal with it. The same strategy employed for years with lead paint. If lead paint is sequestered, it poses no threat. When you start trying to scrape all of it off and replace it is the point at which you've now exposed yourself and everyone that might inhale some of that dust. Same thing with asbestos. As long as it's somewhere that you won't inhale/ingest it, there isn't a problem. Asbestos brake pads, problem. Asbestos siding on a house, only a problem if you're doing construction that disrupts it. Similarly, if you have a location with high levels of lead in the dirt or are concerned about it, perhaps you should import soil and do some raised bed planting.