PASSIVE REMEDIATION OF ACID MINE DRAINAGE BY VETIVER GRASS (CHRYSOPOGON ZIZANIOIDES L.) UNDER GREENHOUSE HYDROPONIC CONDITIONS

Mining operations can produce acid mine drainage (AMD), which presents dangers to the environment through soil and water contamination. We are investigating vetiver grass (Chrysopogon zizanioides L.) to passively remediate AMD from the abandoned Tab-Simco mining site near Carbondale, IL. There are unique characteristics that identify vetiver as a good candidate, such as tolerance to climatic stresses (i.e. extreme temperatures, draughts) and other inhospitable conditions (i.e. acidic or saline soils), as well as the ability to withstand and rapidly absorb heavy metals. Our objectives are to observe the effect vetiver has on AMD, determine metal uptake and translocation, and estimate optimal planting density under hydroponic conditions. The hydroponic study setup included planting densities of 2-4 plants per hydroponic container with ~3.3 L Tab-Simco AMD (media for control). Replicates were prepared with Bermuda grass (Cynodon dactylon) for comparison. AMD samples were analyzed for pH, electric conductivity (EC), dissolved oxygen, alkalinity, sulfate and total dissolved metals (Fe, Al, Mn, and the 8 Resource Conservation and Recovery Act metals), where uptake and translocation will be determined from plant accumulation. Vetiver survived in AMD for 30 days with very mild toxicity symptoms (i.e. slight browning, leaf curling). Moreover, a majority of vetiver under AMD-stress showed clear development of fresh roots. Gradual increase in pH and decrease in EC of the AMD over time from initial 2.67±0.141 (average±SD, N=9) and 3297±141.2 μS, respectively was observed. The 4- and 3-plant treatments showed the greatest change in pH by 30 days, where 4-plant treatments showed greater changes in EC. Single-factor ANOVAs detected significant difference across planting densities for both pH and EC (0.025 < P < 0.01), including no plant containers. This suggests that the 4-plant treatments are more effective for remediating Tab-Simco AMD. Further experiments on sulfate and metal content in AMD and vetiver plants are in progress and will be discussed.