Bioremediation in field box plots of a soil contaminated with wood-preservatives: A comparison of treatment conditions using toxicity testing as a monitoring technique

A soil contaminated with polycyclic aromatic hydrocarbons, petroleum hydroc arbons and chlorophenols was bioremediated in field box plots. Three differ ent bioremediation treatments (tillage and irrigation alone (box plot 2) or in addition to amendment with nitrogen and phosphorus (box plots 3 and 4) and additional organic amendment composed of agricultural crop residues (bo x plot 4)) were compared using chemical analysis for target contaminants an d six toxicity tests (seed germination, earthworm survival, SOS Chromotest, Toxi-Chromotest, solid-phase Microtox(R) and red blood cell (RBC) haemolys is assay). Degradation was enhanced, and toxicity was generally the most re duced, in box plots 3 and 4. Although chemical analysis indicated that the two amendment protocols were equally effective, soil toxicity was generally the most reduced in box plot 4. The earthworm survival and seed germinatio n assays were the most reliable and relevant toxicity tests. Difficulties a rising with the other tests included insensitivity to changes in soil conta minant levels, inconsistency and interference by soil particles and other s oil constituents. Because of the lack of agreement between toxicity tests, these results support the use of a battery of toxicity tests in conjunction with chemical analysis, when assessing the efficacy of bioremediation.