EFFECTS OF BIOREMEDIATION ON RESIDUES, ACTIVITY AND TOXICITY IN SOIL CONTAMINATED BY FUEL SPILLS

Triplicate outdoor lysimeters were contaminated by 2.3 ml cm-2 spills of jet fuel, heating oil and diesel oil, respectively. One of each set of triplicates was left untreated, one was tilled only, and one received complete bioremediation treatment consisting of liming, fertilization and weekly tilling. For 20 weeks during summer, hydrocarbon residues were monitored by quantitative gas chromatography. Microbial activity was measured by fluorescein diacetate hydrolysis. Toxicity was assessed by Microtox measurements, seed germination and plant growth bioassays. Persistence and toxicity of the fuels increased in the order of jet fuel < heating oil < diesel oil. In each case, bioremediation treatment strongly decreased fuel persistence and toxicity and increased microbial activity as compared to contaminated but untreated soil. Tilling alone had a favorable but more limited effect. Good correlations were found between residue decline, microbial activity and toxicity reduction. Persistence and toxicity also correlated with the hydrocarbon composition of these three fuels. Our findings indicate that bioremediation treatment can restore fuel spill contaminated soils in 4-6 weeks to a degree that they can support plant cover. Recovery of the soil is complete in 20 weeks. © 1990.