Researchers compared two methods of cleaning up soil contaminated with heavy metals: one using a plant called Thlaspi caerulescens that naturally absorbs zinc and cadmium, and the other using maize treated with a chemical called EDTA. They found that the Thlaspi plant removed more cadmium and zinc from the soil compared to the maize + EDTA method. However, the high copper levels in the soil limited the Thlaspi plant's effectiveness. The EDTA treatment increased the solubility of heavy metals in the soil, but did not significantly increase metal concentrations in the maize plants. The study suggests that using Thlaspi plants may be more effective for cleaning up industrially contaminated soil, while the maize + EDTA method may not be as efficient.