Ecotoxicological and chemical evaluation of motor gasoline and BTEX compounds in soil
The toxicity of motor gasoline, benzene, toluene, ethylbenzene, and xylenes (collectively referred to as BTEX compounds), to terrestrial organisms (plants, soil invertebrates) in various soils (artificial sandy-loam soil, and field-collected clay loam and sandy-loam soils) was examined. As these compounds are highly volatile, sub-samples of the spiked soils were collected along a concentration gradient and the measured concentrations were used to derive estimated effect concentrations (EECs) to better reflect the concentrations to which the organisms were actually exposed. Adverse effects were most pronounced in the acute toxicity tests. Acute effects were generally predictive of longer-term effects. Reproduction and growth were unaffected in adults that survived initial acute exposures (<=75 and <=400 mg mogas/kg soil d.w. for earthworms and Collembola, respectively). The toxicity of the individual BTEX compounds was greatest for ethylbenzene xylenes > toluene > benzene. Long-term (234 days) studies of the fate and effects of motor gasoline on earthworms demonstrated no toxicity following one month of exposure in the clay loam soil, and two months following exposure in the sandy-loam soils. The decline in toxicity was a function of reduced bioavailability as a result of aging (sequestration), biodegradation, and volatilization. The derived data will contribute to the understanding of the fate and effects of fresh or weathered gasoline spill events to terrestrial ecosystems.