Evaluating the phytotoxicity of Pb-Zn tailings to big bluestem (Andropogongerardii Vitman) and switchgrass (Panicum virgatum L.)

The TriState Mining District of southeast Kansas, northeast Oklahoma, and s outhwest Missouri was an area of intensive Pb and Zn mining for more than 1 00 years. Consequently, large quantities of Pb-Zn tailings (chat) were prod uced by milling operations and discarded throughout the area. The objective of this study was to implement a phased approach to assess the potential f or metal phytotoxicity of the chat to two native grasses. First, metal conc entrations in chat and shoot tissues of big bluestem (Andropogon geraudii V itman) and switchgrass (Panicum virgatum L,) were measured and the shoot ti ssues were examined for visual signs of trace element toxicity. Phytotoxic effects could not be assessed accurately, however, because phytotoxicity st udies of native perennial species are limited, Therefore, an early seedling growth test and a 101-day controlled growth study were implemented to exam ine directly the effects of high metal concentrations in chat on the growth of big bluestem and switchgrass. The early seedling growth test showed tha t percent survival, biomass, and root plus shoot growth were not significan tly different for seedlings that germinated in chat compared with those gro wing in the control medium. The 101-day controlled growth study showed that there were few differences in root and shoot biomass produced by big blues tem and switchgrass growing in chat compared with the control medium, There fore, there was little indication of metal phytotoxicity to big bluestem an d switchgrass based on the similarities in root and shoot biomass productio n of plants growing in chat compared with a noncontaminated medium.