ZINC AND CADMIUM UPTAKE BY HYPERACCUMULATOR THLASPI-CAERULESCENS AND METAL-TOLERANT SILENE-VULGARIS GROWN ON SLUDGE-AMENDED SOILS

Two metal tolerant plants, Thlaspi caerulescens J. and C. Presl. (hype raccumulator), and Silene vulgaris L. (indicator) were grown with ''Pa ris Island Cos'' Romaine lettuce (Lactuca sativa var. longifolia) on l ongterm sewage sludge plots. Metal uptake patterns by plants in relati on to total soil metal and soil pH were examined. The 2-year study use d four treatments and two pH levels. Zinc and Cd uptake were measured. Zinc and Cd for Silene and lettuce were as expected with increasing p lant concentration in the more contaminated treatments and lower pH le vels. Thlaspi followed the same pattern for Cd but not for Zn. Concent rations of Cd were not significantly different between Thlaspi and the other plants. Zinc concentrations in Thlaspi (2000 and 4000 mg kg(-1) ) were 10-fold greater than in Silene. They showed no relation to avai lable soil Zn. Although Thlaspi appears to hyperaccumulate Zn on mildl y contaminated soils, Cd uptake follows predictable patterns.