Experimental assessment of the adequacy of clayey soils in Irbid to retard lead from aqueous solutions and leaded gasoline

Abstract.

Lead is a well-known chemical that is harmful to humans and the environment and can be spread widely, among other sources, by emissions from vehicles that still use leaded gasoline, leaks and spills of leaded gasoline and waste gasoline. Lead that reaches the ground surface may then migrate through the soil and reach groundwater aquifers. This, however, depends on many factors, including the soil type and properties. The ability of clayey soils to retard lead movement from aqueous solutions and leaded gasoline in the subsurface have been explored experimentally in this study. The experimental program conducted included experiments designed to estimate the sorption capacity of natural clayey soils in the Irbid area for lead from both aqueous solutions and leaded gasoline. Two major types of sorption experiments were carried out, namely, sets of experiments to obtain the sorption isotherms for a predetermined dose of soil added to a given aqueous solution and leaded gasoline and sets of experiments based on the Distributed Reactivity Model (DRM), in which lead concentrations varied over orders of magnitude. The results indicate that lead from leaded gasoline is not available for sorption and thus may migrate through soils and hazardous waste dump sites using clayey liners without experiencing retardation, while lead from aqueous solutions is retarded. This is because lead is present in gasoline as a non-polar complex compound called tetraethyl lead. This complex is then subject to biodegradation and may degrade after it penetrates clayey soils or clay liners and reaches the groundwater table to produce water soluble lead cations.