PHYTOREMEDIATION POTENTIAL OF THLASPI-CAERULESCENS AND BLADDER CAMPION FOR ZINC-CONTAMINATED AND CADMIUM-CONTAMINATED SOIL

Metal-tolerant hyperaccumulator plants may be useful to phyto-remediat e contaminated soils. To evaluate agronomic management practices to ma ximize phytoremediation, two metallophytes, Thlaspi caerulescens J. an d C. Presl (Zn hyperaccumulator) and bladder campion [Silene vulgaris (Moench) Garcke L.] (an indicator) were compared to 'Rutgers' tomato ( Lycopersicon esculentum L.) in a pot study to assess Zn and Cd uptake patterns in relation to soil pH. Soils used for the study were gathere d at three different sites in the vicinity of an old Zn smelter in Pal merton, PA, and contained 48 000, 4100, and 2100 mg kg(-1) Zn and 1020 , 37.4, and 35.2 mg kg(-1) Cd, respectively . Each soil was adjusted t o three pH levels ranging from 5.06 to 7.04. Thlaspi caerulescens show ed much greater tolerance to the metals than the other plants (up to 1 8 455 mg kg(-1) Zn and 1020 mg kg(-1) Cd dry shoots without yield redu ction) with metal stress apparent only in the low pH treatments of the two most contaminated soils. In all treatments except for the farm so il (least contaminated) at pH 5.06, T. caerulescens had higher concent rations of both Zn and Cd than bladder campion and tomato. Thlaspi cae rulescens was also more effective at translocating both Zn and Cd from soil to plant shoots. A variety of soil extractions were used to eval uate the correlation of shoot metal concentrations with quantitative m easures of ''available'' soil metals. Concentrations of Cd measured in several common extractants (DTPA, water, 0.01 M Ca(NO3)(2), and 1.0 M NH4NO3) were significantly correlated with Cd concentrations in tissu e of each plant. Shoot Zn concentrations of bladder campion and tomato were significantly correlated with Zn extracted by the neutral salt e xtractants for all soils. For T. caerulescens, the neutral salt extrac table Zn was significantly correlated with shoot Zn only in the two mo re contaminated soils. No extractant predicted shoot Zn concentration for T. caerulescens in the least contaminated soil.