Fate of Heavy Metals in an Abandoned Lead‐Zinc Tailings Pond: I. Vegetation

Abstract

A 50‐yr‐old abandoned tailings pond from a Pb‐Zn processing mill was studied to determine relationships among depositional processes, physical and chemical properties of surface soils, vegetation development, and plant foliar concentrations of Zn, Cd, Cu, and Pb. Five soil/vegetation types were identified ranging from loamy sand with arid land species and 14% aerial vegetation cover at the upper (north) end of the pond to clay loam with wet meadow species and 61% cover at the lower (south) end of the pond. Foliar concentrations of Cd, Zn, Cu and Pb in blue grama [ Bouteloua gracilis (H.B.K) Lag.] and creeping bentgrass ( Agrostis stolonifera L.) showed no significant differences among the soil/vegetation types in which they dominated. Concentrations of Cd and Pb in foliage of alkali muhly [ Muhlenbergia asperifolia (Nees & Meyen) Parodi], a ubiquitous grass species, were higher at the south than the north end of the pond. Metal concentrations in alkali muhly showed significant linear relationships to soil concentrations of metals in the five soil/vegetation types for total Cd ( r 2 = 0.97; P ≤ 0.001) and Zn ( r 2 = 0.70; P ≤ 0.05), but exhibited negative exponential relationships for total Cu ( r 2 = 0.99; P ≤ 0.001) and Pb ( r 2 = 0.99; P ≤ 0.001). Lead concentrations in grasses within the lower meadows (37.6–69.0 mg kg −1 dry mass) exceeded levels known to be toxic to plants. The results were evaluated in terms of tailings pond reclamation.