A comparison of five bioassays to monitor toxicity during bioremediation of pentachlorophenol-contaminated soil

Five bioassays were used to measure toxicity during bioremediation of a soil contaminated with pentachlorophenol (PCP; 335 ppm), polycyclic aromatic hydrocarbons (PAHs; 1225 ppm) and petroleum hydrocarbons (19 125 ppm). Different bioremediation treatments were tested in soilmicrocosms including amendment with phosphorus and/or PCP-degrading Pseudomonas sp. UG30, either as free cells or encapsulated in k-carrageenan. Soil toxicity was monitored using the solid-phase Microtox test, SOS-chromotest, lettuce seed germination, earthworm survival and sheep red blood cell (RBC) haemolysis assays. PCP levels were reducedin all treatments after 210 days. The RBC lysis assay, Microtox testand SOS-chromotest indicated reduced toxicity in most of the microcosms by day 210. Trends depicted by lettuce seed germination and earthworm survival LC50 values varied with each treatment. For example, insoil amended with phosphorus, both the seed germination and earthworm survival LC50 data suggested increased soil toxicity. However, for soil treated with encapsulated Pseudomonas sp. UG30 cells, the earthworm survival LC50 data indicated reduced toxicity while seed germination LC50 values showed little change from values obtained prior to bioremediation. Our results show that toxicity trends in a contaminatedsoil during bioremediation differ according to the assay used. [ABSTRACT FROM AUTHOR]