Using Ternary Diagrams to Characterize Transport and Attenuation of BTX

Abstract

During the past decade or longer, large amounts of data on the concentrations of dissolved aromatic hydrocarbons have been obtained from routine monitoring of leaky underground storage tanks (USTs). Commonly, aromatic hydrocarbon concentration data is interpreted only within the context of regulatory maximum allowable concentration levels. We show in this paper how ternary diagrams can clearly characterize the physical and chemical controls governing the fate and transport of aromatic hydrocarbons in ground water from routine monitoring data. The results of type mathematical modeling experiments for BTX solute transport show that changes in BTX concentrations, when plotted as proportions on ternary diagrams, form clear “trajectories” documenting major attenuation or transport processes. For example, BTX concentrations affected by biodegradation form a trajectory from the source BTX location on the ternary diagram to the benzene apex. In contrast, BTX concentrations affected by volatilization form a trajectory trending from the source to the xylene apex. Ternary diagrams are easy and effective tools to determine from routine monitoring data (1) whether proposed natural attentuation processes are in fact present, and (2) the efficiency of different remediation efforts used to clean up UST sites.