Feenstra Thesis

Aqueous Concentration Ratios to Estimate Mass of Multi-Component NAPL Residual in Porous Media

by S d e y Feensa

A thesis presented to the University of Waterloo

in fbKiment of the

thesis requirement for the degree of Doctor of Philosophy

in Earth Sciences

Waterloo, Ontario, Canada, 1997

Ostadey Feenstra 1997

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A method was developed and evaluated for estimating the mass of chernicals contained in NAPL residual zones based on temporal changes in the ratios of the dissolved contaminants derived fIom the dissolution of multi-component NAPL residual.

The Effective Solubility Mode1 (ESM) was developed as a tool to describe the changes in aqueous concentration ratios of organic contaminants emitted h m the dissolution of a multi-component zone of NAPL residual. The modd is based on the prinaple &hat temporal changes in the ratios of aqueous-phase concentrations in groundwater can be related to the degree of chemical mass depletion of NAPL residual. The ESM utilizes a series of linked equilibration cells to calculate the dissolution of multi-component NAPL according to Raoult's Law.

ESM simulations compared favourably to the results of three published laboratory dissolution experiments and two controlled field experiments. A method was developed using the ESM, together with groundwater monitoring data, to estimate the quantity of chemical mass contained in NAPL zones at sites of NAPL contamination. As an example application, monitoring results of the groundwater pump-and-treat system at the Emplaced-Source experiment were used to estirnate the mass of the NAPL source. The NAPL mass estimated using the ESM method was within 20% of the actual NAPL mass. The mass estimate was made using only the measwd aqueous concentrations in extraction weil PW-2, and the physical and chemical properties for the NAPL components and aquifer. No specific assumptions were required regarding the dimensions or geometry of the source zone, groundwater flow conditions, or dissolution mass transfer coeffiaents. This research has illustrated the potential for the ESM method to provide useful estimates of the chemical mass contained in multi- component NAPL residual zones in porous media.

Our present ability is determine the mass of chemicals contained in NAPL source zones in the subsurface was described succinctly by Jennifer Warnes, in her song - The Hunter:

YOU never know,

you never know,

you never know when, you never know.

(Attic Records Limited, 1992)

It is hoped that the work described here wiU improve this ability.

This research was supported financiaily by the University Consortium Solvents-in-Groundwater Research Program at the University of Waterloo which was funded by The Boeing Company, Ciba-Geigy, Dow Chemical Company, Eastman Kodak Company, General Electric, Laidlaw, Inc., Mitre Corporation, Motorola, PPG Industries, United Technologies, the Natural Saence and Engineering Research Cound (NSERC), and the Ontario University Research Incentive Fund (URIF).

Many individuals at the University of Waterloo also contributed to the completion of the two controlied field experiments at the Borden site. Dr. Michael Rivett, post-doctoral feilow from the UK, was instrumental in the design and implementation of the Emplaced-Source experiment. Field activities s u d i as the installation of monitoring devices, the collection of cores and plumbing of the groundwater treatment system could not have been completed without the efforts of Bob ngleton and Paul Johnson. Installation of the source zone was far more chailenging than antiupated, and the contributions of Mette Brohoim and Sam Vales are gratefully

acknowledged. Doug Morton provided many days of effort in sarnpling and analysis of groundwater samples from the experiment.

The opportunity to use information from the Free-Release expriment was provided by Dr. Kim Broholm, post-doctoral fellow from Denrnark, who was assisted in the irnplementation of the experiment by Mette Brohoim, Paul Johnson, Bert Habicher, Andre Unger, Scott Vales, Sam Vales, Dave Baerg and Jeff Murphy.

Mary Feenstra coded the Excel macro for the Effective olubility Mode1 and assisted in preparation of the cornputer graphio.

This thesis has benefted from the review and suggestions of my thesis examination committee of Drs. Jim Barker, Ri& Devlin, Doug Madtay and Neil Thomson of the University of Waterloo, and Dr. David Burris of the US Air Force.

Of most significance, 1 am grateful to my thesis advisor Dr. John Cherry for the opportunity to have pursued this research on a part-time basis, in an unorthodox marner, over an extended period of t h e , at the University of Waterloo.

This thesis is dedicated to the memory of ~ o b Farvolden. In 1973, it

was the enthusiasm of his lectures on introductory geology at Waterloo that

woke me, figuratively (and in dass on one occasion - literdly), to the many fascinating challenges to be found in the study of earth saences. A s 1

proceeded through my years of undergraduate study at Waterloo, it was he that encouraged me and guided me to graduate work in hydrogeology at

Waterloo. Although the hydrogeology program was smailer in 1978-1980

than it is today, it was a stimulatng place to study, and the timing was perfect

to be among the first wave of hydrogeologists that focused on groundwater

contamination. Since then, 1 have had the opportunity to be involved in consulting on groundwater contamination problems throughout Canada and

the United States, and the privilege of pursuing my doctoral studies at

Waterloo. These endeavours have been as fdfdling and rewarding as c m be

hoped for in one's professional career. For Bob's encouragement and

direction in leading me to this path, I will be always grateful.

Page

Chapter 1. Introduction

1.1 Objective 1.2 Existing Methods for Esmation of NAPL Mass

1.3 Aqueous Concentration Ratios for Estimation of NAPL Mass

1.4 Conceptual Models for NAPL Source Zones

1.5 Chemical Composition of NAPLs

Chapter 2. Detennination of Effective Solubility

Introduction

Solubility of a SingleComponent NAPL

Effective Solubility of Multi-Component NAPLs

2.3.1 Ideal Behaviour

2.3.2 Non-Ideal Behaviour

Solubility of Solid-Phase Organic Compounds

Applicability of Raoult's Law for Simple NAPLs

2.5.1 Chlorinated Solvent Mixtures

2.5.2 Chlorinated Benzene Mixtures

2.5.3 Petroleum Hydrocarbon Mixtures

2.5.4 Condusions on Raodt's Law for Simple NAPLs

ApplicabiLity of Raoult's Law for Cornplex NAPLs

2.6.1 Gasoline

2.6.2 Diesel Fuel

2.6.3 Creosote and Cod Tar

Page

2.6-4 Effect of Uncharacterized Portion of NAPL

2-6.5 Condusions on Raouit's Law for Cornplex NLWLS

2.7 Prediction of Effective Solubility using UNIFAC

2-7-1 Chlorinated Solvent Mixtures

2.7.2 Chlorinated Benzene Mixtures

2.7.3 Petroleum Hydrocarbon Mixtures

2.7.4 Gasoline

2.7.5 Diesel Fuel

2-7.6 Creosote and Coal Tar

2.7.7 Conclusions on UNIFAC for NAPL Mixtures

2.8 Other Factors Influencirtg Solubility

2.8.1 Tempera ture

2.8.2 pH

2.8.3 Dissolved Inorganics

2.8.4 Miscible Co-Solvents

2.8.5 Surfactants

2.8.6 Dissolved Organic Matter

2.9 Overail Conclusions Regarding Effective Solubiiity

Chapter 3. Principles for Dissolution of Multi-Component NAPL

3.1 Introduction 167

3.2 Dissolution of NAPL Residual 167

3.2.1 Pore-Scale Mass Trans fer Models 167

3.2.2 Laboratory -Scale Mass Trans fer Models 172

Non-Equilibrium Mass Trawfer for MultiComponent NAPL

Chromatographie Effect in MultiComponent NAPL Zones

Dissolution of NAPL Pools

Conceptual Models for Dissolution of Multi-Component NAPL

Chapter 4. Description of Effective Solubility ModeI (ESM) 4.1 Prinuples

4.2 Calcuiation Method

4.2.1 Input Parameters

4.2.2 Iterative Calculations

4.2.3 Output

4.3 Sensitivity Analyses

4.3.1 Overview

4.3.2 Effect of Solubility of Components

4.3.3 Effect of Number of Ceils

4.3.4 Effea of Soi1 Organic Carbon

4.3.5 Effect of Porosity

4.3.6 Effect of Initiai NAPC Content

4.4 Error Analyse