The effect of nonideal sorption on contaminant transport in groundwater and vapor: Statistical and modeling tools

Abstract

The objective of this dissertation was to develop statistical and modeling tools that can support the analysis of subsurface remediation applications characterized by nonideal sorption. These tools included methods for simulating contaminant transport in groundwater affected by pore diffusion and/or nonlinear and dual mode sorption isotherms. The statistical tools included new methods for the interpretation of soil vapor data, with a focus on newly available data from Manufactured Gas Plant sites in New York State.

The statistical tools developed in this dissertation address datasets characterized by a high degree of data censoring and possible artifacts related to uneven distributions of samples across multiple sites and buildings. In addition to the methods for calculating population percentiles and associated confidence intervals, hypothesis testing methods for comparing the population of vapor data with a reference population were also developed and evaluated via illustrative comparisons with the published 2001 EPA Building Assessment Survey and Evaluation (BASE) study of industrial buildings. The new methods were based on new modifications of the Kaplan Meier method and Maximum Likelihood methods commonly applied to the censored data.

The groundwater modeling tools emphasized numerical algorithms to support nonideal sorption processes, with a focus on recent developments in the conceptualization of "dual mode" isotherms and intraparticle pore diffusion model. Both mechanisms were incorporated into contaminant models utilizing a split-operator numerical approach that could be readily extended to three-dimensional transport; all algorithms were developed for efficient implementation in parallel computing environments. Numerical experiments and comparisons with other algorithms confirmed the accuracy and efficiency of the new procedures for several applications of interest. The main advantages of the modeling tools were in the flexibility to accommodate any isotherm equation and the ease of adapting existing grid-based transport models of any dimensionality to include nonlinear equilibrium sorption and/or intraparticle pore diffusion.