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

The TriState Mining District of southeast Kansas, northeast Oklahoma, and southwest Missouri was an area of intensive Pb and Zn mining for more than 100 years. Consequently, large quantities of Pb-Zn tailings (chat) were produced by milling operations and discarded throughout the area. The objective of this study was to implement a phased approach to assess the potential for metal phytotoxicity of the chat to two native grasses. First, metal concentrations in chat and shoot tissues of big bluestem (Andropogon gerardii Vitman) and switchgrass (Panicum virgatum L.) were measured and the shoot tissues were examined for visual signs of trace element toxicity. Phytotoxic effects could not be assessed accurately, however, because phytotoxicity studies of native perennial species are limited. Therefore, an early seedling growth test and a 101-day controlled growth study were implemented to examine directly the effects of high metal concentrations in chat on the growth of big bluestem and switchgrass. The early seedling growth test showed that percent survival, biomass, and root plus shoot growth were not significantly different for seedlings that germinated in chat compared with those growing in the control medium. The 101-day controlled growth study showed that there were few differences in root and shoot biomass produced by big bluestem and switchgrass growing in chat compared with the control medium. Therefore, there was little indication of metal phytotoxicity to big bluestem and switchgrass based on the similarities in root and shoot biomass production of plants growing in chat compared with a noncontaminated medium.