Toxicity of gasoline aqueous‐leachate through sand‐clay columns

Abstract

The objective of this study was to understand the effect clay type and clay concentration may exert on the toxicity of the percolating water around a leaking underground gasoline storage tank. This situation in the laboratory was simulated using sand‐clay columns. The experiment was conducted with two types of clays (kaolinite and illite) and three clay concentrations (0, 5 or 10%). The gasoline (0, 0.2, 0.5 or 0.8 mL) was injected through a hole in the middle of the column. After 24 hours of gasoline injection 100 mL of deionized water was added to the column and the leachate was tested for toxicity (E₀) using the marine luminescent bacteria (Photobacterium phosphoreum). Leachate from the pure sand column was less toxic than the control but was more toxic than from the columns with clay. The addition of clay significantly reduced both the toxicity and the hydraulic conductivity. The toxicity increased significantly with the increase in gasoline concentration up to 0.5 mL but decreased with 0.8 mL gasoline. Using the concentrations of clay and the gasoline and the hydraulic conductivity a regression equation ( = 0.77) was calculated to predict the toxicity of the gasoline aqueous leachate.