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Summary
The soil-bentonite (SB) slurry-based barrier technology is successfully used to isolate the heavy metal contaminants at sites. While the heavy metal-induced deterioration effects arouse the urgent need for assessment of the barrier performance. In this study, experimental investigation and theoretical work were performed for quantitative analysis of the deterioration effects. Test results showed that the incorporation of bentonite significantly enhanced the hydraulic conductivity and contaminant retention performance of the barrier system. The hydraulic conductivity decreased from 9E-8 m s-1 to 1E-9 m s-1, the hydrodynamic dispersion coefficient reduced from 3E-8 m2 s-1 to 7E-10 m2 s-1, and the retardation factor tested under effect of 3000 mg L-1 Cu(II) improved around 24.65%. However, the barrier performance was rapidly deteriorated and failed to meet the requirement after heavy metal contamination, especially for scenarios with Cu(II) concentrations higher than 500 mg L-1. On this basis, two deterioration parameters were successfully proposed for quantitative analysis of this deterioration effect from the viewpoints of hydraulic conductivity and contaminant retention. In a further step, an optimal design method of a barrier system was established and confirmed using the proposed deterioration parameters, for a given service life of the barrier system and Cu(II) concentration at contaminated site.
