Just to support your claim: http://soils.wisc.edu/facstaff/barak/poster_gallery/minneapolis2000a/ http://soils.wisc.edu/facstaff/barak/poster_gallery/minneapo.

Just to support your claim: http://soils.wisc.edu/facstaff/barak/poster_gallery/minneapolis2000a/ http://soils.wisc.edu/facstaff/barak/poster_gallery/minneapo... (The link doesn't mention copper in particular)