PARENT SESSION
02 - Soil and Sediment Contamination
8:30 AM to 12:20 PM, Monday, 13 May 2002
Session Chair: Boudou, Alain ¹, Gyori, Zoltan ², ^{1 2} .
Stolz B

(02-05) Implications of sequestration on the bioavailability and toxicity of motor gasoline to Eisenia andrei in soil.

Princz, Juliska^*,1, Stephenson, Gladys², Feisthauer, Natalie², Solomon, Keith¹, Miasek, Peter³, ¹ University of Guelph, Guelph, Ontario, Canada² ESG International Inc., Guelph, Ontario, Canada³ Imperial Oil, North York, Ontario, Canada

ABSTRACT- Sequestration is the incorporation of a compound into the soil matrix without chemical alteration, thereby reducing its biological availability. The chemical concentration in the soil remains unchanged, but the bioavailability, and hence the toxicity of the contaminant, decreases as its residence time in soil increases. A series of tests was initiated to determine to what extent the sequestration of motor gasoline (mogas) in soils is influenced by soil type, the presence of microbial organisms, and soil-contact time. The effect of sequestration on the bioavailability and toxicity of mogas to the earthworm, Eisenia andrei, was evaluated over time in three irradiated and non-irradiated soil types (artificial soil, and field-collected clay loam and sandy loam soils). Gamma-irradiation of the soils was used to assess the extent to which sequestration was influenced by microbial activity. Initial tests were conducted to determine the toxicity of mogas to Eisenia andrei in the three types of soil. The 14-d LC50s were 1146, 1072, and 399 mg mogas/kg soil dry weight (d.w.) for the artificial, the clay loam, and the sandy loam soils, respectively. Following these initial tests, soils were gamma-irradiated. The irradiation process depressed microbial populations with minimal changes to the physico-chemical properties of the soil. Earthworm behaviour and survival were not compromised in the irradiated soils relative to non-irradiated soils. The irradiated and non-irradiated soils were amended at a nominal concentration of 3000 mg mogas/kg soil d.w., and the toxicity of the contaminated soil was assessed by conducting acute earthworm toxicity tests at discrete time intervals. Toxicity values were examined relative to the measured concentrations of mogas constituents present in the soils at the time of testing. These data will aid in understanding the fate and effects of the inadvertent release of gasoline in soil environments and could contribute to more realistic estimates of the associated ecological risks.

Key words: Motor gasoline, Soil, Toxicity, Sequestration