Natural soil attenuation potential of hydraulic fracturing chemicals
and their transformation products following leaks and spillages
1211
1Dirk Mallants , Jirka Simunek , Andrew Taylor , Rai Kookana , Mike Williams
1 CSIRO Australia, 2 University of California Riverside

CSIRO LAND AND WATER

Fate pathway analysis for coal seam gas (CSG) chemicals

Parameter

Detection ratio

TPH

Detection ratio

Benzo(k)fluoranthene

1/5

C6‐C9

1/5

Benzo(a)anthracene

1/5

C10‐C14

2/5

Chrysene

1/5

C15‐C28

3/5

Dibenz(ah)anthracene

1/5

C29‐C36

2/5Fluoranthene

1/5

Indeno(1,2,3‐cd) pyrene

1/5

BTEX

 Demonstrating safe use of unconventional natural gas
extraction requires detailed impact assessments of themanagement of produced waters and wastes (e.g. brines).
Science underpinning such assessments involves fatepathway analysis for drilling, hydraulic fracturing andcoal‐associated naturally occurring chemicals.

Parameter

Benzene0/5Naphthalene

1/5

Toluene

0/5

Phenanthrene

1/5Ethylbenzene

0/5

Pyrene

1/5

Xylene

0/5

PHENOLS

PAHPhenol

1/5

3‐Methylcholanthrene

0/5Bisphenol A1/5Acenaphthene

0/5

4‐Nonyphenol

1/5

Benzo(b)fluorathene

1/5Benzo(ghi)perylene

1/5TOX

1/5

 Detection ratios for organic chemicals in CSG produced water
across major developments in Queensland (Australia). Monitoring
period 2011‐ 2014. TOX = total organic halides.

 Potential fate pathways for CSG chemicals. Review ofinternational literature shows major risks are linked tosurface activities including leaks and spills.

Numerical simulation of soil attenuation: coupled biotransformation, sorption and migration
Selected organics and their transformation
products Current study evaluated several possible organics in CSG produced

Transformation pathways, chemical half‐lifeand organic carbon sorption
 Example transformation pathway 1: Aerobic degradation pathwayof phenol in soil environment (simplified) (Omokoko et al. 2008)

water (coal‐derived & hydraulic fracturing chemicals). All selectedtransformation products are included in the simulations (Mallants et al.
2015)
CAS No.

Chemical StructureGroup

Chemical nameChemicalIUPAC nameformulaOHOH

Parentcompound (P)/transformationproducts (D)Phenolic compounds

108‐95‐2

C6H6O

C6H6O2

PhenolPhenolBenzene‐1,2‐diolP

1,2‐Catechol(1,2‐dihydroxybenzene)

120‐80‐92‐hydroxymuconic
acid‐6‐semialdehyde(HMSA)

3270‐98‐2

C6H6O4(3E,5E)‐6‐hydroxy‐2‐oxohexa‐3,5‐
dienoic acidD22‐methylphenol

95‐48‐7C7H8O

Other name:

POH
COOH
CHO

Coal‐derived naturally occurring organics
PhenolOHCathchol

HMSA(2‐hydroxymuconate‐6‐semialdehyde)

D1

 Example transformation pathway 2: Aerobic degradation

Numerical simulation of soil attenuation
Chemicals
PhenolCatecholHMSA
2‐methylphenol
3‐methylcatechol
Naphthalene
Cis‐1,2‐dihydroxy
1,2dihydronapthalene
2‐butoxyethanol
Limonene
Bronopol2‐bromo‐2‐nitroethanol (BNE)
Bromonitromethane (BNM)
Formaldehyde

Retardation factor, Rmean
minmax
541473
527
1009551
1
1291939112
112
112
1292
165
3334
5541605
302
216
5551
854
2
2
2
2

558
3957
1172
230
7mean
7274
551242

Half‐life (days)
min0.1
183
1
2
9
9max
23
365
9715
80

9610304
28
18
6

2
0.3
360
11
9
115
1718548
51
30
14 Retardation factor (R) and half‐life used in numerical simulation of

coupled degradation, sorption and migration. Simulations based on
HYDRUS‐1D (Simunek et al. 2006). R values based on literature KOC andmeasured organic carbon (OC) in Vertosols (Mallants et al. 2015).

pathway of bronopol in natural waters (Cui et al. 2011)

PAHo‐cresol

3‐
methylcatechol

488‐17‐5

C7H8O23‐Methylbenzene‐
1,2‐diol

DNaphthalene

91‐20‐3

C10H8

Bicyclo[4.4.0]deca‐
1,3,5,7,9‐penteneP

cis‐1,2‐dihydroxy‐1,2‐dihydronaphthalene51268‐88‐3

C10H10O2(1R,2S)‐1,2‐dihydronaphthalen
e‐1,2‐diol

DWetlands along river Murray(post‐drought conditions). Falling
groundwater
2007‐2009
Chemicallevels
additivesfrom
in hydraulicfracturing
2‐butoxyethanol 111‐76‐2C H inorganic
O2‐Butoxyethanol
led to oxidation of reduced(surfactant)
Other name:sulfide minerals, generating acid ethylene
glycol monobutyl
sulfate soils.
6 14 2

 Simulated soil attenuation of phenol and degradation products

catechol and HMSA using HYDRUS‐1D. Fate pathway assumes 30‐year
long leak of CSG‐containing fluids (hypothetical C = 1 mg/L) underconditions of low flow rate (35 mm/year). All chemicals almost
completely degrade within top 10 cm of the soil profile; leakage togroundwater did not occur for the conditions tested.

P

Hydraulic fracturing additives

ether

Limonene(solvent)

138‐86‐3

C10H16

1‐Methyl‐4‐(1‐methylethenyl)‐
cyclohexene

P

Bronopol(biocide)

52‐51‐7

C3H6BrNO42‐bromo‐2‐
nitropropane‐1,3‐
diol

P

2‐bromo‐2‐
nitroethanol

5437‐60‐5

C2H4BrNO32‐bromo‐2‐
nitroethanol

D

Bromonitro‐
methane563‐70‐2

CH2BrNO2

Bromonitro‐
methaneDNitromethane

75‐52‐5CH3NO2

Nitromethane

DFormaldehyde

50‐00‐0CH2O

Methanal

D

Mathematical model for 2‐component (C1, C2) transformation applied to 2‐
methylphenol and naphthalene: Coupled 1st‐order degradation (µ1, µ2 ), linear
equilibrium sorption on soil organic carbon (R1, R2) and migration (D, q) invariably‐saturated (ϴ) soil profile. µ = ln2/half‐life; R=1+(ρb×Kd)/ϴ. A 3‐
component model was used for phenol and a 4‐component model for bronopol.

R1C1  C1  qC1 µ1 R1C1 Dx
tx x  Calculated Dilution Attenuation Factors at 2 cm soil depth as

R2C 2 C 2  qC 2
 µ2 R2C 2  1 R1C1
 D
tx x xfunction of attenuation parameters {µ, Kd}. A = phenol, B = catechol, C= HMSA; D = 2‐methylphenol, E = 3‐methylcatechol; F = naphthalene,
G = DHDHN; H = 2‐butoxyethanol; I = bronopol, J = formaldehyde; K =limonene.

FOR FURTHER INFORMATIONREFERENCESSOFTWAREDirk Mallants
CSIRO Land and Water
Waite Campus
Adelaide, South Australia
Dirk.Mallants@csiro.au

Cui N. et al. 2011. Toxicity profile of labile preservative bronopol in water: The role of more persistent and toxic transformation
products. Environmental Pollution 159: 609-615.
Mallants D. et al. 2015. Natural soil attenuation of organic compounds associated with coal seam gas extraction. CSIRO. 47 pp.
Omokoko B.U.K.J. et al. 2008. Isolation of the phe-operon from G. stearothermophilus comprising the phenol degradative metapathway genes and a novel transcriptional regulator. BMC Microbiology 8: 197.
Šimůnek, J. et al. 2006. The HYDRUS software package for simulating two- and three-dimensional movement of water, heat, andmultiple solutes in variably saturated media. Technical manual, Version 1.0. PC Progress, Prague, Czech Republic.

HYDRUS: http://www.pc‐progress.com