Monitoring bioremediation in creosote-contaminated soils using chemical analysis and toxicity tests

Three soils with a history of creosote contamination (designated NE, TI and AC) were treated in bench-scale microcosms using conditions (nutrient amen dment, moisture content and temperature) which had promoted mineralization of C-14-pyrene in a preliminary study. Bioremediation was monitored using t he solid-phase Microtox test, seed germination and earthworm survival assay s, SOS-chromotest, Toxi-chromotest and a red blood cell (RBC) haemolysis as say. Contaminant concentrations in the AC soil did not change after 150 day s. Polycyclic aromatic hydrocarbon (PAH) concentrations decreased in the NE soil, and toxicity decreased overall according to the earthworm, seed germ ination and Microtox tests. Although total petroleum hydrocarbons (TPHs) in the TI soil were reduced following treatment, results of the earthworm, se ed germination, RBC and Microtox tests suggested an initial increase in tox icity indicating that toxic intermediary metabolites may have formed during biodegradation. Toxicity testing results did not always correlate with con taminant concentrations, nor were the trends indicated by each test consist ent for any one soil. Each test demonstrated a different capacity to detect reductions in soil contamination.