METAL AND ARSENIC IMPACTS TO SOILS, VEGETATION COMMUNITIES AND WILDLIFE HABITAT IN SOUTHWEST MONTANA UPLANDS CONTAMINATED BY SMELTER EMISSIONS .2. LABORATORY PHYTOTOXICITY STUDIES

Vegetation communities on metal- and arsenic-contaminated uplands surr ounding a smelter in southwest Montana have been eliminated or highly modified. Laboratory toxicity tests were performed using site soils fr om the impacted areas to determine whether the soils limit the ability of plants to establish and grow. The germination and growth of alfalf a, lettuce, and wheat in impacted area soils was compared to germinati on and growth of the three species in reference soils. The degree of p hytotoxicity was quantified using a species-endpoint toxicity score ca lculated on the magnitude of difference between germination and growth of plants in impacted and reference soils. The impacted soils exhibit ed substantial toxicity to plants: 5% of the sites were severely phyto toxic, 55% were highly phytotoxic, 10% were moderately phytotoxic, 20% were mildly phytotoxic, and 10% were nontoxic. Root growth was consis tently the most affected endpoint (18 of 20 impacted soils) and reduct ion in root length and mass was observed. Correlation and partial corr elation analysis was used to evaluate the causes of phytotoxicity. Con centrations of As, Cu, and Zn and, to a lesser extent, Pb and Cd were found to be positively correlated with phytotoxicity.