#soilposting

I did some informal soil expiriments a while ago (partly because nothing was growing around the buildings near me, and found that the sandy stuff around where i live fizzed and frothed up, and made a terrible smell when i mixed it with water (unusual for this soil because there is p much no precipitation and no groundwater).

After experimenting with sand/silt/clay separation, the water that remained was murky reddish brown, (visibility of maybe 2 cm), stinky, and could be frothed.

In the non-landscape areas, (the places under concrete and below the surface,), i mixed the soil from there with water, and it behaved without any fizzing, frothing, or stink. In addition during the sand/silt/clay seperation, there was much more organic material, and much more clay. Most shocking was tHe clarity of the water after seperation; the post-mix-subsoil water was near crystal clear after being mixed and seperated, whereas the surface-soil-water remains dark reddish brown with low visibility. Clearly, there was chemical reaction with the water that could not Be seperated like particulate matter.

For a year i wonder(ed) what could be in the surface sand that contaminated the water so much. No other dirt id ever worked with produced such chemistry. (Nor was any so hostile to life (it killed all plants and seeds i tried to grow from it))

I only just learned that a possible cause of this is a chemical added to/mixed with the soil during contruction/landscaping that is supposed to prevent weeds from growing (which, evidently means to prevent all life from growing)

My questions are: What is the cause of this toxic soil? Is it from initial construction or introduced afterward? If it is an additive, what are the probable/possible additives? How would one reclaim/seperate the soil/toxin mixture? How could such a toxin be made inert, or if thats impossible, what should be done to lessen its danger?

Some of these questions are secondary to questions of certain property relations which are the source of practices of poisoning land and water, etc, and any methods to fight back against these relations and practices are appreciated.