SOIL TOXICITY AT THE SKYTOP ROAD-CUT ON INTERSTATE I-99: PLANT GERMINATION AND GROWTH EXPERIMENTS

The Skytop road-cut on Interstate I-99 near State College, Pennsylvania has proven to be an environmental disaster. During construction, immense quantities of pyritic rock were unearthed, then crushed to stabilize hillsides and to create a roadbed. Subsequently, acidic drainage has been noted in runoff from the construction site, in nearby domestic wells, and in tributaries to Buffalo Run. If left untreated, this rock will continue to drain acidic waters with a pH around 2 into the watershed. At present, the proposed remediation strategy involves the use of Bauxsol ™ (the treated residue of aluminum mining) to neutralize the acid rock in situ. We conducted a series of growth experiments and toxicity assays to determine Bauxsol's effect on seed germination and plant growth. Preliminary results from these studies indicate that seed germination is strongly effected in certain species of plants (Lactuca sativa, lettuce, r = 0.93; Schizachyrium scoparius, Little Bluestem, r = 0.94) by the percentage of Bauxsol in the substrate. Bauxsol was found to neutralize acid rock drainage from pyritic rock substrates when present in a 1:3 ratio (1g Bauxsol neutralized 3g of pyritic rock). At concentrations higher or lower than this, plant germination and subsequent growth was severely retarded. Plant growth with Bauxsol alone was not observed to occur in this study. We have therefore determined that a layer of topsoil will be necessary if any plant growth is to succeed.