Chromium Absorption by Plant Roots. Formation of Long-Lived Cr(V) Species. An Ecological Hazard?

The adsorption of either chromiumOID or chromate(VI) by plan~ has been investigated by means of ESR spectroscopy. Cr(IH) absorption yielded complexes, in part immobilized, of O-donor ligand~g in the roots. The adsorption of chrominm(Vl) produced first mobile Cr(V) species, where the metal ion was bound to low-molecular weight ligand% and then also Cr(IID species. The intensity ratio between the ESR signals of Cr(V) and Cr(m) species became almost constant with elapsing contact time, but decreased as the Cr(VD concentration in solution was lowered. Noticeably, Cr(V) species were detected even at chromium concentration in solution as low as 1 ppm. The formation of stable Cr(V) species in plants, could produce dangerous effects to ecological cyctes, because, accordin~ to literature data, Cr(V) may be involved in the mutagenic and carcinogenic properties of the element.