From industrial sources, in some cases, no less. Paper mills, tanneries, etc. Silver lining is that these farms are solar PV installations of the future, when possible, to give the land a few decades to recover from contamination. I presume you can pair this solar in an agrivoltaics model with grasses or other flora they can absorb and remediate subject contamination, but do not know enough to speak with authority on that.

Maine farmers impacted by PFAS pivot to harvesting solar power - https://www.newscentermaine.com/article/tech/science/environ... - August 22nd, 2024

> Maine farmland made worthless by PFAS chemicals could be put back into production again through harvesting the power of the sun.

> Last month, regulators approved new rules following 2023 state legislation that calls for renewable energy generated on contaminated land, clearing the way for the development of thousands of megawatts of new clean power.

(brownfields are a great place to cite solar generation)

EPA Brownfields Renewable Energy Siting - https://www.epa.gov/system/files/documents/2024-08/brownfiel...

NREL Solar Development on Contaminated and Disturbed Lands - https://web.archive.org/web/20250218192949/https://www.nrel....

Plant-based material can remediate PFAS, new research suggests - https://www.niehs.nih.gov/news/factor/2022/9/science-highlig...