3 ms·

There was no widespread soil remediation so if you live near any road at all (that would be everyone) you are still affected by this. No need to be near an airp

There was no widespread soil remediation so if you live near any road at all (that would be everyone) you are still affected by this. No need to be near an airport

throwaway0a5e 4y ago
Yeah, but you won't get internet virtue points, likes, retweets and shares screeching about the dirt the way you will complaining that general aviation still uses leaded gas hence why you never hear about it but you always hear about avgas which would be a solved problem if the FAA would just do their jobs.
kragen 4y ago
How mobile is the lead today? There are a number of extremely insoluble lead salts, such as the sulfide, the phosphate, the chromate, the titanate, some of the oxides, and even the carbonate and the sulfate. My mental model is that lead metal and the above-mentioned salts are basically immobile in the soil: you can have all the lead sulfide or metallic lead you want in your soil without it leaching into the groundwater or contaminating the tomatoes you grow in it. And lead ions (in the form of the acetate, for example) are only mobile until they bump into one of the anions mentioned above, at which point they get locked up for geological periods of time. Organic lead compounds like tetraethyllead are a much scarier problem, but they also get broken down into ionic lead over a period of years. Is that right? Am I misunderstanding the dynamics?
- hammock 4y ago
  Lead in soil gets stirred up by wind, rain, humans and animals into the air all day long. Of particular risk as far as food contamination is concerned are leafy vegetables and shrubby fruits that grow near the ground (surface contamination, eventually binding to the food - not internal uptake necessarily). There are studies measuring these effects, you don’t have to take my word for it. Here is what the CDC has to say https://www.cdc.gov/nceh/lead/prevention/sources/soil.htm https://www.cdc.gov/nceh/lead/prevention/sources/soil.htm
  - kragen 4y ago
    Thank you! This CDC page seems to say that swallowing or breathing lead-contaminated soil is a problem (most of the minerals I mentioned won't withstand strong solutions of hydrochloric acid, such as stomach acid) but it doesn't even suggest that lead-contaminated soil is a potential source of groundwater contamination or contamination of plants grown in it. Nor does it suggest that soil being stirred up by wind and rain is a significant danger, though presumably a sufficiently strong windstorm would be. It links an EPA page https://www.epa.gov/sites/default/files/2020-10/documents/lead-in-soil-aug2020.pdf https://www.epa.gov/sites/default/files/2020-10/documents/le... which does talk about "eating fruits or vegetables grown in contaminated soil". More specifically it recommends not growing root crops such as potatoes in soil with over 100 ppm lead, low-growing leafy vegetables in soil with over 400 ppm lead, or fruits and vegetables in soil with over 1000 ppm lead. It still doesn't mention anything about groundwater. Unfortunately it doesn't cite any of the studies so we can find out what levels of lead contamination occur in crops grown in contaminated soil or to what degree they're dependent on lead not being locked up in the mobile forms I described (can potato roots digest galena?), nor to what degree lead-compound dust on poorly washed lettuce results in human lead poisoning. Since the CDC didn't link any, which studies would you most recommend reading?

There was no widespread soil remediation so if you live near any road at all (that would be everyone) you are still affected by this. No need to be near an airport

throwaway0a5e 4y ago

Yeah, but you won't get internet virtue points, likes, retweets and shares screeching about the dirt the way you will complaining that general aviation still uses leaded gas hence why you never hear about it but you always hear about avgas which would be a solved problem if the FAA would just do their jobs.

kragen 4y ago

How mobile is the lead today? There are a number of extremely insoluble lead salts, such as the sulfide, the phosphate, the chromate, the titanate, some of the oxides, and even the carbonate and the sulfate. My mental model is that lead metal and the above-mentioned salts are basically immobile in the soil: you can have all the lead sulfide or metallic lead you want in your soil without it leaching into the groundwater or contaminating the tomatoes you grow in it. And lead ions (in the form of the acetate, for example) are only mobile until they bump into one of the anions mentioned above, at which point they get locked up for geological periods of time. Organic lead compounds like tetraethyllead are a much scarier problem, but they also get broken down into ionic lead over a period of years. Is that right? Am I misunderstanding the dynamics?

hammock 4y ago
Lead in soil gets stirred up by wind, rain, humans and animals into the air all day long. Of particular risk as far as food contamination is concerned are leafy vegetables and shrubby fruits that grow near the ground (surface contamination, eventually binding to the food - not internal uptake necessarily). There are studies measuring these effects, you don’t have to take my word for it. Here is what the CDC has to say https://www.cdc.gov/nceh/lead/prevention/sources/soil.htm https://www.cdc.gov/nceh/lead/prevention/sources/soil.htm
- kragen 4y ago
  Thank you! This CDC page seems to say that swallowing or breathing lead-contaminated soil is a problem (most of the minerals I mentioned won't withstand strong solutions of hydrochloric acid, such as stomach acid) but it doesn't even suggest that lead-contaminated soil is a potential source of groundwater contamination or contamination of plants grown in it. Nor does it suggest that soil being stirred up by wind and rain is a significant danger, though presumably a sufficiently strong windstorm would be. It links an EPA page https://www.epa.gov/sites/default/files/2020-10/documents/lead-in-soil-aug2020.pdf https://www.epa.gov/sites/default/files/2020-10/documents/le... which does talk about "eating fruits or vegetables grown in contaminated soil". More specifically it recommends not growing root crops such as potatoes in soil with over 100 ppm lead, low-growing leafy vegetables in soil with over 400 ppm lead, or fruits and vegetables in soil with over 1000 ppm lead. It still doesn't mention anything about groundwater. Unfortunately it doesn't cite any of the studies so we can find out what levels of lead contamination occur in crops grown in contaminated soil or to what degree they're dependent on lead not being locked up in the mobile forms I described (can potato roots digest galena?), nor to what degree lead-compound dust on poorly washed lettuce results in human lead poisoning. Since the CDC didn't link any, which studies would you most recommend reading?