Phytoremediation Potential of Thlaspi caerulescens and Bladder Campion for Zinc‐ and Cadmium‐Contaminated Soil

Abstract

AbstractMetal‐tolerant hyperaccumulator plants may be useful to phytoremediate contaminated soils. To evaluate agronomic management practices to maximize phytoremediation, two metallophytes, Thlaspi caerulescens J. and 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 gathered at three different sites in the vicinity of an old Zn smelter in Palmerton, 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 to three pH levels ranging from 5.06 to 7.04. Thlaspi caerulescens showed much greater tolerance to the metals than the other plants (up to 18 455 mg kg−1 Zn and 1020 mg kg−1 Cd dry shoots without yield reduction) with metal stress apparent only in the low pH treatments of the two most contaminated soils. In all treatments except for the farm Soil (least contaminated) at pH 5.06, T. caerulescens had higher concentrations of both Zn and Cd than bladder campion and tomato. Thlaspi caerulescens was also more effective at translocating both Zn and Cd from soil to plant shoots. A variety of soil extractions were used to evaluate the correlation of shoot metal concentrations with quantitative measures 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 tissue of each plant. Shoot Zn concentrations of bladder campion and tomato were significantly correlated with Zn extracted by the neutral salt extractants for all soils. For T. caerulescens, the neutral salt extractable Zn was significantly correlated with shoot Zn only in the two more contaminated soils. No extractant predicted shoot Zn concentration for T. caerulescens in the least contaminated soil.