I found a old metal dump on my property about 30ft by 35ft. Most of the metal has crumbled into flakes so I think it might be from the early 1900s. Burying it under 3ft of dirt and going to densely plant trees over it. What trees like heavy partial shade to sun from conifer trees and polluted (high iron) soil ? Also would it be safe for me or my livestock to eat food from these trees ?
Zone 8b, Pacific northwest
What types of metals were left there to rot? Do not forget that in the early 1900's lead was still a widely used metal in paints as well as plumbing pipes.
If it was all steel or iron then no worries and just about any of the berry bushes will love that spot, for cattle you might want to go with service berry and let them get fairly large before you let the browsing begin so they will survive the pruning.
Conifers do have allopathic properties, and most will acidify the soil at least a little (pH around stands is usually lower than 6.3).
Do add mycorrhizae to the soil when you do your plantings.
I've found tin cans, bits of wire, paint or oil cans, gears and a couple large soild pieces of mining / farm machines.
There is ocean spray growing on part of it, 6 large Douglas Firs on one edge, I can add lime to the soil. Hazelnuts I know don't mind growing under the Firs, as well as other natives, red alder grows anywhere with water. I just wondering about other trees.
Most importantly can lead , mercury, arsenic, etc can travel from ground into plant and into fruits, leaves and nuts? Maybe the last question is off topic for this subforum.
Yes, those heavy metals can and will move up into the trees and fruits (or nuts) of those trees.
If there are paint cans, you most likely have lead contamination, and possibly others.
Take a soil sample of that area (at least the 4 corners and the center) to your extension service and ask for a metals test.
Far better to know than just guess.
For most of the heavy metals, fungi will do a lot of remediation for you.