Fate and Transport of Select 

Compounds of Interest in Fracing

Fluids

Angus E. McGrath, Ph.D.

March 28, 2011
Overview

• Overview of Compounds of Interest (COIs) 

in Fracing Fluids

• COIs

– Properties of Selected COIs

– Fate and Transport of COIs

• Implications for Drinking Water Quality
Taken From: Canadian Society of Unconventional Gas

Composition of Fracing Fluids
COIs in Fracing Fluid

Product Chemical Composition

Linear gel 

delivery system

Guar gum derivative

Diesel

Water gelling 

agent

Guar gum

Water

Fumaric acid

Linear gel 

polymer

Fumaric acid

Adipic acid

Linear gel 

polymer slurry

Diesel oil #2

Cross-linker Boric acid

Ethylene Glycol

Monoethanolamine

Cross-linker Sodium tetraborate

decahydrate

Product Chemical Composition

Biocide 2,2-dibromo-3-nitrilopropionamide (DBNPA)

Foaming agent Isopropanol

Salt of alkylamines

Diethanolamine

Foaming agent Ethanol

2-Butoxyethanol

Ester salt

Polyglycol ether

Water

Acid treatment Hydrochloric acid

Acid treatment Formic acid

Breaker fluid Diammonium

peroxodisulfate
Common COIs

• Muriatic acid or hydrochloric acid;

• Guar gum;

• Diesel (BTEX);

• Ethanol and isopropanol;

• Sodium chloride;

• Formic acid, Fumaric and adipic acids;

• Boric acid.
Unconventional COIs

• Ethylene glycol (EG);

• Diethanolamine (DEA);

• 2,2-Dibromo-3-nitrilo-propionamide 

(DBNPA);

• 2-Butoxy ethanol; and

• Diammonium peroxosulfate (ammonium 

persulfate).
Ethylene Glycol (EG)

• Liquid miscible in water

• Low Kow and Henry’s constant

• Common laboratory reagent – common 

contaminant in analyses – reason for 

elevated detection limits, 10 mg/L, 

detection limit actually ~0.2 mg/L or lower 
• Anaerobic biodegradation pathway (Dwyer, 

1983, Huang, 2005):

• Nitrate electron 

donor (Schramm 

and Schink, 1991).

Ethylene Glycol (EG)
• Aerobic biodegradation pathway (Gruden

et al., 2001):

EG  glycolic acid  oxalic acid  CO2

• Persistence is moderate to low depending 

on microbial activity

Ethylene Glycol (EG)
• Polar, colorless liquid, infinite solubility in 

water

• Low Kow and Henry’s constant

• DEA is considered mobile by EPA (2006)

• EPA (2006) classified DEA as nonpersistent in soil and groundwater (half-life 

of days to weeks)

Diethanolamine (DEA)
• In the presence of nitrite, DEA forms Nnitrosodiethanolamine (NDELA):

DEA + NO2

-  NDELA

• EPA (2006) notes that NDELA persists in 

the environment but formation depends on 

NO2

-

concentration.

Diethanolamine (DEA)
2,2-Dibromo-3-nitrilo-propionamide

• Solid – solubility 15 g/L at 25o C

• Low Kow and Henry’s constant 

• Nucleophilic substitution (with reducing agents, I-, HS-, 

HSO3

-

, S2O3

2-

, and SO3

2-

) forms cyanoacetamide and 

bromide (Exner et al., 1973) – short half-life (hours)
2,2-Dibromo-3-nitrilo-propionamide

• DBNPA hydrolysis reaction has a half-life 

of 21 hr pH 7.4 and > 155 hr below pH 6, 

reaction as follows:

DBNPA  dibromoacetonitrile + NH3 

dibromoacetoamide  dibromoacetic acid 

 glyoxylic acid + Br-  oxalic acid + CO2

 CO2
• Exner et al. (1973) reacted DBNPA with 

soil and soil extract (particle free) at pH 

4.8 to 7.5 only ammonia and Br observed.

• Reaction has a half-life of 4 to 25 hr. 

Fastest rate observed at highest pH.

• Reaction attributed to microbial 

degradation.

• Surface catalyzed hydrolysis also possible 

mechanism.

2,2-Dibromo-3-nitrilo-propionamide
• DBNPA interacts with mineral surfaces 

retarding transport, but still a mobile 

compound

• Not a persistent compound due to 

hydrolysis and microbial degradation

2,2-Dibromo-3-nitrilo-propionamide
• Colorless liquid, miscible in water and 

most organic solvents, ether like odor

• Low Kow and Henry’s constant

• Considered mobile, but not persistent

• Beihoffer and Ferguson (1994) observed 

that it has been detected in groundwater 

near US solid waste landfills (<0.4 to 84 

ug/L)

2-Butoxyethanol
• Howard et al. (1991) estimated half-lives 

of 2-butoxyethanol of 2–8 weeks in 

groundwater and 1–4 weeks in soil, based 

on unacclimated aqueous aerobic 

biodegradation

• IUCLID (2000) reports 95% 

biodegradation in 28 days

• Hydrolysis unlikely in aqueous 

environment

2-Butoxyethanol
• Soluble, strong oxidant

• Dissociates into ammonium and persulfate

ions

• Persulfate reacts readily with organic 

matter and reduced inorganic species

• Activated to form persulfate radical by heat 

and ferrous iron

Ammonium Persulfate
• Persulfate degrades to form sulfate ions

• Half-life in the order of minutes to days 

depending on reaction conditions

• Considered a mobile ion although will 

adsorb and react with both inorganic and 

organic surfaces

• Short persistence decreases potential for 

mobility

Ammonium Persulfate
Summary

• Ethylene glycol poses a potential risk for 

mobility and false positive detections but is 

not persistent

• DEA mobility is retarded by mineral 

adsorption, but is not persistent

• DBNPA mobility is retarded by mineral 

adsorption, but is not persistent 

• 2-Butoxyethanol is mobile with limited 

retardation, but is not persistent
• Ammonium persulfate is mobile but not 

persistent

• Monitoring for any of these compounds 

may only be warranted if impacts from 

more concentrated reagents in fracing

fluids are detected in wells

• Other geochemical considerations...

Summary
Questions?