Journal of Contaminant Hydrology 199 (2017) 14–23

Contents lists available at ScienceDirect

Journal of Contaminant Hydrology
journal homepage: www.elsevier.com/locate/jconhyd

Batch soil adsorption and column transport studies of 2,4-dinitroanisole(DNAN) in soils
Jennifer D. Arthur a,⁎, Noah W. Mark a, Susan Taylor b, J. Šimunek d, M.L. Brusseau a,c, Katerina M. Dontsova a,ea

Soil, Water and Environmental Science Department, University of Arizona, United States
U.S. Army Engineer Research and Development Center, United States
Hydrology and Atmospheric Sciences Department, University of Arizona, United StatesdUniversity of California, Riverside, United StateseBiosphere 2, University of Arizona, United Statesbca r t i c l e

i n f oArticle history:
Received 16 July 2016
Received in revised form 2 February 2017
Accepted 21 February 2017
Available online 1 March 2017
Keywords:
2,4-Dinitroanisole (DNAN)
2-Amino-4-nitroanisole (2-ANAN)
4-Amino-2-nitroanisole (4-ANAN)
Soil adsorption
Organic carbon (OC)Cation exchange capacity (CEC)a b s t r a c t
The explosive 2,4,6-trinitrotoluene (TNT) is currently a main ingredient in munitions; however the compoundhas failed to meet the new sensitivity requirements. The replacement compound being tested is 2,4dinitroanisole (DNAN). DNAN is less sensitive to shock, high temperatures, and has good detonation characteristics. However, DNAN is more soluble than TNT, which can inﬂuence transport and fate behavior and thus bioavailability and human exposure potential. The objective of this study was to investigate the environmental
fate and transport of DNAN in soil, with speciﬁc focus on sorption processes. Batch and column experiments
were conducted using soils collected from military installations located across the United States. The soils werecharacterized for pH, electrical conductivity, speciﬁc surface area, cation exchange capacity, and organic carbon
content. In the batch rate studies, change in DNAN concentration with time was evaluated using the ﬁrst orderequation, while adsorption isotherms were ﬁtted using linear and Freundlich equations. Solution mass-loss
rate coefﬁcients ranged between 0.0002 h−1 and 0.0068 h−1. DNAN was strongly adsorbed by soils withlinear adsorption coefﬁcients ranging between 0.6 and 6.3 L g−1, and Freundlich coefﬁcients between 1.3 and34 mg1 − n Ln kg−1. Both linear and Freundlich adsorption coefﬁcients were positively correlated with theamount of organic carbon and cation exchange capacity of the soil, indicating that similar to TNT, organic matterand clay minerals may inﬂuence adsorption of DNAN. The results of the miscible-displacement column experiments conﬁrmed the impact of sorption on retardation of DNAN during transport. It was also shown that
under ﬂow conditions DNAN transforms readily with formation of amino transformation products, 2-ANAN
and 4-ANAN. The magnitudes of retardation and transformation observed in this study result in signiﬁcant attenuation potential for DNAN, which would be anticipated to contribute to a reduced risk for contamination ofground water from soil residues.
© 2017 Elsevier B.V. All rights reserved.

1. Introduction
The United States military uses the high explosive compound 2, 4, 6trinitrotoluene (TNT) as one of the main ingredients in munitions. TNT
is sensitive to shock and temperature, presenting a signiﬁcant danger
for unintended detonation. The Department of Defense is transitioning
to so-called insensitive munitions (IM) to increase soldier safety(Jurgensen, 2000). This effort has resulted in the replacement of TNT
with 2,4-dinitroanisole (DNAN) a compound that meets sensitivity requirements (Boddu et al., 2009). DNAN is a nitrated aromatic compound
similar to TNT in composition and structure (Fig. s1). It is much less
⁎ Corresponding author at: 429 Shantz Bldg, Tucson, AZ 85721, United States.
E-mail address: jarthur1@email.arizona.edu (J.D. Arthur).

http://dx.doi.org/10.1016/j.jconhyd.2017.02.004
0169-7722/© 2017 Elsevier B.V. All rights reserved.

sensitive to stimuli than TNT and, as its melting point is similar to thatof TNT, it can replace TNT in melt cast munitions (Davies and Provatas,
2006).
Limited information is available regarding DNAN's environmental
fate and potential impact on humans and the environment. BothDNAN and its transformation products exhibit microbial toxicity (withamino products being less toxic than DNAN) (Liang et al., 2013); as
well as toxicity to higher organisms (Dodard et al., 2013). However,
DNAN toxicity is comparable to or less than that of TNT (Dodard et al.,2013; Stanley et al., 2015).
Incomplete or low-order detonations that scatter explosives on
training ranges is one of the main ways explosives enter the environment. IMs containing DNAN are more likely to result in incomplete detonations than traditional explosives (Walsh et al., 2013). DNAN is also

J.D. Arthur et al. / Journal of Contaminant Hydrology 199 (2017) 14–23

more soluble than TNT in water, 276.2 mg L−1 (Boddu et al., 2008) versus 103.1 (Ro et al., 1996) at 25 °C, and laboratory studies show that
DNAN is readily dissolved from IM formulations when exposed towater (Taylor et al., 2013; Taylor et al., 2015).
Like TNT, DNAN can transform in the environment via reduction of
nitro groups to amino groups and form a series of products, such as 2amino-4-nitroanisole (2-ANAN), 4-amino-2-nitroanisole (4-ANAN),
and 2,4-diaminoanisole (DAAN) (Olivares et al., 2013; Hawari et al.,2015). While transformation pathways have been determined, transformation rates in soils have not been measured.
DNAN's adsorption behavior is less well known. DNAN reactions
with lignin may remove DNAN from contaminated water (Saad et al.,2012) by H-bonding. The effectiveness of lignin as a DNAN sorbent suggests that soil organic matter may adsorb DNAN. It was also observedthat cellulose can weakly adsorb DNAN through H-bonding (Shukla
and Poda, 2016). Mesocosm studies, using an insensitive formulation
containing DNAN, in the presence of plants reported no DNAN in drainage nor in plant biomass, indicating soil retention, adsorption and/ortransformation (Braida et al., 2011).
Hawari et al. (2015) investigated the environmental fate of DNAN
and its reduced products, 2-ANAN, 4-ANAN, and DAAN. These researchers conducted batch adsorption studies for these compoundswith two sterilized soil materials. Their ﬁndings showed that DNAN
was reversibly adsorbed by the soils, while 2-ANAN and 4-ANAN sorbed
both reversibly and irreversibly, and DAAN sorbed irreversibly. This behavior is similar to that of TNT, which becomes easily reduced in the environment (nitro to amino groups) with resulting compounds
adsorbing both reversibly (Dontsova et al., 2006) and irreversibly(Thorn and Kennedy, 2002; Thorn et al., 2002) to the organic matterin the soils. Reversible adsorption of TNT can happen through several
mechanisms, depending on polarity of organic matter, including hydrophobic interactions mediating association with particulate organic carbon and polar interactions with dissolved organic carbon (Eriksson
and Skyllberg, 2001).
Since environmental behaviors of DNAN and TNT are similar, we can
expect that DNAN would interact with the same soil components as
TNT. In general, organic carbon is often the best predictor of adsorption
behavior of organic compounds, particularly non-ionic ones like DNAN
(e.g., Site, 2001). However, TNT is adsorbed by both OC andphyllosilicate clays (Haderlein et al., 1996; Dontsova et al., 2009) suggesting that DNAN may also be adsorbed by clays. This was conﬁrmed
by Linker et al. (2015). The sorption is inﬂuenced by the type of exchangeable cation, similar to other nitroaromatic compounds(Haderlein et al., 1996), with DNAN interacting directly with the cation.
Given the paucity of information concerning the sorption and transport behavior of DNAN, the main objective of the present work is to: examine the fate of DNAN in soils; quantify the extent of DNAN reversible
adsorption; quantify mass loss through other mechanisms related to thechemical and physical properties of the soils; and assess relationships
between DNAN adsorption and soil properties. Batch and column experiments were conducted using soils collected from military installations located across the United States. The 11 soils were characterized
for pH, speciﬁc surface area (SSA), electrical conductivity (EC), OC content, and cation exchange capacity (CEC) to help understand the interactions between DNAN and soils.

15

Table 1
Soils used to study interaction with DNAN. Soil names, classiﬁcation according to US Taxonomy, and location where collected is listed.
Soil nameSoil classiﬁcation

Location

CatlinCatlin silt loam, mixed, mesic, superactive
Oxyaquic Argiudoll
Musselshell sandy loam, carbonatic, frigid
Aridic Calciustepts
Captina silt loam, siliceous, mesic, typic
Fragiudults
Plymouth loamy sand, mesic, coated Typic
Quartzipsamment

Urbana, IL

Fort
HarrisonArnold AFB
PlymouthCamp
ButnerLimestone
Hills
Sassafras

Helena sandy loam, mixed, semiactive,
thermic Aquic Hapludults
Musselshell sandy loam, carbonatic, frigid
Aridic Calciustepts
Sassafras loam, siliceous, mesic Typic
Hapudult
Camp
Verdigris silt loam, mixed, superactive,
Gruberthermic Cumulic HapludollsCamp
Keeline-Turnercrest loam, mixed,
Guernsey superactive, calcareous, mesic Ustic
Torriorthents
Florence
Cherioni loam, mixed, superactive,MRhyperthermic, shallow Typic Haplodurids
Camp Swift Bergstrom sandy clay loam, mixed,
superactive, thermic Cumulic Haplustolls

Fort William Henry
Harrison, MT
Arnold Air Force
Base, TN
Massachusetts
Military Reservation,
MA
Camp Butner, NC
Limestone Hills, MT
Aberdeen Proving
Ground, MD
Camp Gruber, OKCamp Guernsey, WY

Florence Military
Reservation, AZ
Camp Swift, TX

Entisols, Inceptisols, Mollisols, Aridisols, and Ultisols. Soils in the text are
identiﬁed by location where they were collected except Plymouth, Catlin, and Sassafras, which are identiﬁed by series name.
Collected soils were air dried, sieved (b 2 mm), and characterized before the experiments. Soil OC content was measured using a Shimadzu
SSM-5000A Solid Sample Combustion Unit following pretreatment
with 5% phosphoric acid (H3PO4) to ensure a complete removal of inorganic carbon (U.S. Environmental Protection Agency, 2010). Cation exchange capacity was determined using the sodium acetate method (U.
S. Environmental Protection Agency, 1986). A VWR SympHony SB70P
Benchtop Digital pH and EC Meter was used to measure pH and EC ina 1:1 soil to solution mixture. Particle size was determined using a
Beckman Coulter LS 13320 Laser Diffraction Particle Size Analyzer. A
Beckman Coulter SA 3100 was used to measure SSA by N2 adsorption
applying Brunauer-Emmett-Teller theory (Brunauer et al., 1938). The
mineralogy of the clay fraction in the soils was analyzed by X-ray diffraction for the following samples: Mg-exchanged, Mg-exchanged glycerol solvated, K-exchanged at 25, 300 and 550 °C.
2.2. DNAN stock solutions
DNAN was provided by Picatinny Arsenal. Stock solution of
10 mg L−1 DNAN was prepared by dissolving solid DNAN in deionizedwater on a magnetic stir plate for 24 h. The stock solution was then diluted to a ﬁnal concentration of 0.5 mg L−1 with 0.005 M CaCl2. All prepared solutions were wrapped in aluminum foil to prevent
phototransformation and sealed with Paraﬁlm. Samples and stock solutions were stored in a refrigerator at approximately 4 °C.

2. Methods
2.3. Analytical methods
2.1. Soil collection and characterization
Surface soils (0–20 cm depth) were collected from uncontaminatedsites on ten U.S. Army National Guard training ranges and one from the
University of Illinois farm. Soil series names and classiﬁcations for all
soils are listed in Table 1. The selected soils represent a range of climatesand conditions on military ranges where live ﬁre training occurs. Thesesoils span several soil orders with different moisture regimes, including

2,4-Dinitroanisole samples were analyzed using a Dionex Ultimate
3000 high performance liquid chromatograph (HPLC) equipped with adiode array detector (ThermoFisher, MA). The running method wasadapted from Olivares et al. (2013). The parameters used for analyzing
DNAN samples were the following: a mobile phase ratio of 43:57 methanol and water; the Thermo Scientiﬁc Acclaim reversed phase column
C-18 with 5-μm particle size; and a ﬂow rate of 1 mL min−1. The

16

J.D. Arthur et al. / Journal of Contaminant Hydrology 199 (2017) 14–23

wavelengths used for detection and quantiﬁcation were 300 nm for
DNAN, 254 nm for 2-ANAN, 4-ANAN, and 210 nm for DAAN.
2.4. Batch soil adsorption
Batch adsorption methods were adapted from Roy et al. (1992). Preliminary studies were performed to determine soil solution ratios thatwould result in adsorption of 10 to 30% of added solute, a range
shown to minimize error of determined adsorption coefﬁcients (Royet al., 1992; McDonald and Evangelou, 1997). A series of soil to solution
ratios ranging from 1:4 to 1:60 were tested. Aliquot of 20 mL of solution
was added to each 30 mL borosilicate glass centrifuge tube containing
varying amounts of soil, from 0.33 to 5 g. Non-sterilized soil was used
for all experiments except where speciﬁcally noted.
Blanks and samples containing soil were continuously agitated on areciprocating shaker at 110 rpm for 24 ± 0.5 h at room temperatureaway from light. After agitation, the samples were centrifuged for
20 min at 4700 rpm (4816 relative centrifugal force). A minimum of
3 mL of supernatant was ﬁltered with a 0.45 μm Millex-HV PVDF ﬁlter
and placed in 4 mL amber vials. All samples were analyzed using highperformance liquid chromatography as described above. The pH and
EC of each sample was determined on an aliquot using a SympHony
SB70P Benchtop Digital pH and EC Meter.
We used soil to solution ratios determined in the preliminary experiments (Table s1) for all subsequent tests. To determine the time neededto achieve equilibrium, samples were analyzed at eight time intervals: 1,
4, 8, 24, 48, 72, 96, and 120 h. The input concentration of DNAN used
was 0.5 mg L−1 in a 0.005 M CaCl2 aqueous solution. Three replicateswere prepared for each time interval, as well as blank samples without
soil. After agitation for a set period of time, samples were centrifugedand ﬁltered as described previously. The pH and EC were measured
for each sample. Aliquots for each sample were collected and analyzed
to determine the amount of DNAN remaining in solution, as well as
presence of DNAN transformation products. The equilibrium time wasdeﬁned as the minimum amount of time needed to establish a ratechange of solute concentration equal or b 5% per 24 h time interval(Roy et al., 1992). The mass-loss rate coefﬁcients, k, were determinedfrom the change in the solute concentrations over time for the time period commencing after adsorption equilibrium.
To conﬁrm that the removal of DNAN from solution at the determined equilibrium point represented reversible soil adsorption andwas not inﬂuenced by other processes such as irreversible adsorption
and transformation (microbial or abiotic), we repeated the experiments
for Catlin silt loam and Sassafras loam soils using both unsterilized andsterilized samples and extracted soil samples to determine the amountof DNAN retained in the soil. The soils were sterilized by autoclaving foran hour at 120 degrees, repeated three times over 3 days. Following thesorption equilibration period, the DNAN solution was removed for analysis. The soils were then extracted by adding 20 mL of acetonitrile toeach vial. The samples were agitated on a reciprocating shaker for
24 h, centrifuged and ﬁltered. Both solution samples and acetonitrile extracts were analyzed using HPLC. The mass of DNAN recovered in soil
and solution were used to calculate the DNAN mass balance.
Once the equilibration time was established, experiments were conducted to develop multipoint adsorption isotherms. Eight different
input concentrations, 2.03, 4.06, 8.12, 16.2, 32.5, 65.0, and 130 ppm(or 10.3, 20.5, 41.0, 81.8, 164.1, 328.3, and 656.6 μmol L−1) of DNAN
in 0.005 M CaCl2, were used to construct the isotherms. Each sample
was prepared in triplicate. The equilibration time used was 24 h for all
soils. As previously described the samples were agitated, centrifuged,ﬁltered, and analyzed using HPLC. We plotted soil concentrations calculated based on DNAN removal from solution against the solution concentrations and ﬁt them using both the linear and Freundlich
adsorption equation. From the plots we determined the linear adsorption coefﬁcient, Kd (L kg−1), Kf, the Freundlich adsorption coefﬁcient(mg1 − n Ln kg−1) and n, an empirical parameter that indicates the

afﬁnity of the compound for the adsorbent. The regression analysis
function in Microsoft Excel 2007 was used to determine adsorption parameters, conﬁdence intervals for the estimate, R2 and probabilities ofparameters being signiﬁcantly different from zero. The Freundlich equation was linearized to allow linear regression. The linear adsorption coefﬁcients were used to determine the retardation factor of DNAN in eachsoil. The retardation factor is deﬁned as:
R¼1þ

ρb K dθð1Þwhere ρb represents the bulk density [ML−3], θ is gravimetric watercontent and Kd is the linear adsorption coefﬁcient [L3 M−1]. To calculate
R, the neural network prediction application in HYDRUS-1D was used toestimate the porosity of each soil based on the textural class. The porosity was then used to calculate the bulk density.
Adsorption parameters were compared between the soils to assess
the effect of the soil type on adsorption. Soil properties such as OC content, pH, clay content, and CEC were evaluated for their impact on theadsorption of DNAN and to help predict the environmental fate of thecompound in soil.
2.5. Transport study
To provide a conservative estimate of the potential for DNAN transport in soils, two of the soils that had low DNAN attenuation (adsorption
and transformation) in batch studies, Camp Guernsey and Camp Swift,
were selected for the column experiments. They were packed into
Supelco (Belfonte, PA) glass columns with 7 cm length and 1.18 cm internal diameter and sealed with PTFE caps. Glass wool was placed at thebottom of the columns and on top of the soil proﬁle to prevent soil
movement. Approximately 11 to 12 g of soil was packed homogenously
resulting in the average bulk density (ρ) of 1.54 ± 0.02 g cm−3 for Camp
Swift and 1.62 ± 0.02 g cm−3 for Camp Guernsey soil. Column study experiments were conducted in duplicate.
The columns were saturated with 0.005 M CaCl2 for one hour fromthe bottom to avoid trapping air in the pores. After saturation, the column pore volume (PV) was determined as the volume of solution required to saturate the packed column, minus the dead volume
associated with the column. A Gilson 305 piston pump (Middleton,
WI), attached to the top of the column using stainless steel tubing, delivered a 0.5 mg L−1 (2.8 μmol L−1) DNAN solution with 0.005 M CaBr2
tracer at ~ 0.015 mL min−1 ﬂow rate, equivalent to a mean Darcy ﬂux
of 0.81 cm h− 1. The efﬂuent was collected in 4-mL amber glass vials
using a custom fraction collector with 49-vial capacity built by BricManagement (Tucson, AZ). Volumetric ﬂow rate was calculated by measuring the weight of the collected efﬂuent. After the efﬂuent reachedsteady-state concentrations the solution was switched back to the background solution (0.005 M CaCl2) to observe DNAN desorption from thesoil. Flow interruption studies were also conducted to further investigate mass transfer behavior (Brusseau et al., 1989; Brusseau et al.,1997). Flow was interrupted for 24 h to allow DNAN to equilibratewith the soil. During the ﬂow interruption the column remained
saturated.
DNAN and its transformation products were quantiﬁed using HPLC
as described above. The conservative tracer, CaBr2, was analyzed using
Ion Chromatography (Dionex ICS 5000 with diode array). The bromide
breakthrough curves were analyzed to determine longitudinal
dispersivity (λ) and observe for preferential ﬂow for each soil.
After the end of each experiment, the column was divided into thirds
and weighed. Extractions were performed on each soil sample to determine the amount of DNAN and its transformation products remaining inthe soil. A mixture of soil and acetonitrile in 1:2 ratio was agitated for
24 h, centrifuged, ﬁltered through 0.45 μm Millex-HV PVDF ﬁlter(EMD Millipore Darmstadt, Germany), and analyzed using HPLC (U. S.
Environmental Protection Agency, 2006).

J.D. Arthur et al. / Journal of Contaminant Hydrology 199 (2017) 14–23

Kd (L kg−1) and k (h−1) were used as initial estimates for DNAN transport parameters in HYDRUS-1D. Mass balance calculations were also
performed for DNAN and its transformation products (Table 5).

2.6. Numerical analysis
Numerical analysis of efﬂuent concentrations for the column experiments was performed using temporal moment analysis (TMA) and the
HYDRUS-1D code. TMA, a non-parametric statistical analysis tool used
to describe solute behavior in a time series of samples taken at a particular point, quantiﬁed solute transport parameters such as the Kd, retardation factor, R, λ, and mass balance ratio.
Experiments were also analyzed using HYDRUS-1D (Šimůnek et al.,2008) for simulating the one-dimensional movement of water, heatand multiple solutes in variably saturated porous media. Transport ofthe Br− tracer and solute was described using the advection-dispersion
equation:∂θC w =∂t þ ρ∂C s =∂t ¼ ð∂=∂zÞ  ½θDð∂C w =∂zÞ−∂qC w =∂z−φ

3. Results
3.1. Soil characterization
Results of chemical and physical analyses of the eleven soils selected
for this study are presented in Table 2. Soils are listed in order of decreasing OC content. The soils differed signiﬁcantly in all measured parameters, including OC content (0.34–5.28%), pH (4.23–8.21), clay
content (4.1–32.3%), SSA (1.7–38.3 m2 g−1), and mineralogy.

ð2Þ

3.2. DNAN batch adsorption studies

where Cs is the sorbed concentration [MM−1], θ is the volumetric watercontent [LL− 3], ρ represents the bulk density of the porous medium[ML−3], Cw represents the solute concentration [ML−3], φ is the sink/
source term that accounts for zero, ﬁrst order and other reactions[ML−3 T−1], and q is the volumetric ﬂuid ﬂux density [LT−1] evaluatedby Darcy-Buckingham law. D is the dispersion coefﬁcient, which represents both hydrodynamic dispersion and molecular diffusion [L2 T−1]:
D ¼ λν þ DPreliminary studies showed that DNAN was strongly adsorbed by
the soils, and for many soils the lowest soil to solution ratio, 1:60, wasneeded to achieve target solute removal from solution (Table s1).
3.2.1. Rate studies
Rate studies provide the equilibration time for adsorption and themass-loss rate coefﬁcients of DNAN after adsorption equilibrium isattained. DNAN concentration in the blank solutions did not change signiﬁcantly over 120 h and the slope of ln(C/C0) was not different fromzero (Fig. s2). For samples with soils, a sharp drop in DNAN concentration in the ﬁrst hours was followed by a steady decrease over time. Adsorption equilibrium was attained by 24 h for all soils except Sassafras
loam, for which 48 h was required. We chose to conduct all isotherm experiments using a 24-h equilibration time for easy comparison between
the soils.
The change in DNAN concentration over time after adsorption equilibrium followed 1st order kinetics. This behavior is attributed to transformation and/or irreversible adsorption, as discussed below. The ﬁrst
order mass-loss rate coefﬁcients ranged between 0.0002 and0.0068 h− 1 for Florence and Plymouth soils, respectively (Table 3),
equivalent to 144 to 4 day half lives. The k values were not signiﬁcantly
correleated with soil parameters such as, pH, OC, SSA, CEC, and clay content. No known products of DNAN tranformation were measured insolution.

ð3Þ

where the term λ is the longitudinal dispersivity [L], ν is the average linear velocity [LT−1] and D⁎ represents the effective diffusion coefﬁcient[L2 T−1]. In this model φ is the ﬁrst-order rate constant for the solution
only [ML−3 T−1]:
φ ¼ k  θ  Cw

17

ð4Þ

where k represents the mass-loss rate coefﬁcient due to transformation
and/or irreversible adsorption (T− 1), Cw and θ were as deﬁned
previously.
The inverse mode was used to analyze breakthrough curves to obtain estimated best-ﬁt values for selected parameters. Numerical analysis of the experimental data was performed by ﬁrst simulating theconservative tracer breakthrough curves to characterize water ﬂow
and estimate λ. TMA calculated values for λ were used as the initial inputs for HYDRUS-1D simulations of Br− breakthrough curves. It was observed that the HYDRUS-1D estimates of λ determined from Br−
breakthrough better characterized dispersivity in DNAN simulations
than TMA estimates for DNAN (Table 4). Batch adsorption results for3.2.2. DNAN mass balance
Mass balance studies evaluated the recovery of DNAN in solution
and in soil for sterilized and unsterilized Catlin silt loam and Sassafras

Table 2
Measured physical and chemical properties of soils used in experiments (Mark et al., 2016).

Soil

Texture

Clay
%

Silt
%

Sand
%

pHa

ECb

SSAc
m2 g−1

OCd%

CEC8.2ecmolc kg−1

Mineralogyf

CatlinFort Harrison
Arnold AFB
PlymouthCamp Butner
Limestone Hills
Sassafras
Camp Gruber
Camp Guernsey
Florence MRCamp Swift

Silt loam
Sandy loam
Silt loam
Loamy sand
Sandy loam
Sandy loam
Loam
Clay loam
Loam
Loam
Sandy clay loam

25.6
8.7
11.4
4.4
7.7
11.2
16.4
32.3
4.1
26.8
23.7

65.5
36.5
65.5
20.4
25.9
35.7
42.3
44.9
12.5
33.5
20.8

8.9
54.9
23.1
75.2
66.4
53.1
41.4
22.8
83.4
39.7
55.6

7.31
6.67
6.66
4.23
6.69
7.54
4.4
5.39
8.21
8
7.83

492
449
131
206
219
539
212
74
477
417
203

6.4
7.4
7.8
1.7
4.8
10.5
7.17
38.3
3.9
33
15.1

5.28
3.88
2.68
2.45
2.42
1.99
1.3
0.83
0.77
0.45
0.34

21.4
18
8.7
6.8
6.1
13
7.9
14.3
2.9
12.2
6.5

S, M, K, Q
V,M,K,C
HIV, K, Q, C
V, K
K, V, HIV, Q, M
K, M, C, S, Q
K, HIV, M, C
S, K, M, Q
S, M, K, C, Q
S, M, K, Q
K, M, S, Q

a

In 1:1 soil:water.
EC = Electrical conductivity.
SSA = speciﬁc surface area.
d
OC = organic carbon.
e
Mineralogy, listed in order of decreasing content: C = chlorite, HIV = hydroxyl-interlayered vermiculite, K = kaolinite, M = mica, Q = quartz, S = smectite, V = vermiculite.
f
CEC8.2 = cation exchange capacity at pH 8.2.
b
c

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J.D. Arthur et al. / Journal of Contaminant Hydrology 199 (2017) 14–23

Table 3
Fate and transport parameters for DNAN: linear adsorption coefﬁcient, Kd; adsorption coefﬁcient normalized to fraction of organic carbon in soils, KOC; calculated retardation factor, R;
Freundlich adsorption parameters, Kf and n; mass-loss rate coefﬁcient, k; R2 values, and 95% conﬁdence intervals (CI). All ﬁts for adsorption isotherms were highly signiﬁcant (P-value ≤ 0.01), signiﬁcance of the k estimates is indicated in the table (Sig.).
Soils

CatlinFort Harrison
Arnold AFB
PlymouthCamp Butner
Limestone Hills
Sassafras
Camp Gruber
Camp Guernsey
Florence MRCamp Swift

R2

Kd
Mean
L kg−1

95% CI

6.0
6.3
3.4
4.4
2.1
5.0
1.9
2.0
0.9
1.9
0.6

4.9–7.1
5.7–6.9
2.9–3.9
3.8–5.0
1.8–2.3
4.4–5.5
1.5–2.3
1.7–2.3
0.8–1.0
1.6–2.2
0.4–0.7

0.92
0.93
0.78
0.94
0.92
0.92
0.72
0.91
0.97
0.94
0.84

Koc
L kg−1

R

112.7
162.9
126.5
178.6
84.8
250.0
228.3
240.6
121.4
424.4
175.5

21.2
27.5
12.4
19.1
9.6
21.8
8.5
7.6
4.7
8.6
3.1

R2

Kf
Mean
L kg−1

95% CInMean

95% CI

34
13.9
14.4
10.1
15.4
10.8
2.3
7.6
1.7
6.6
1.3

29.6–39.0
9.7–19.8
10.9–18.9
8.3–12.2
11.7–20.2
8.7–13.2
1.2–4.3
4.9–11.9
1.1–2.6
5.4–7.9
0.6–2.8

0.62
0.77
0.68
0.83
0.56
0.77
0.97
0.72
0.85
0.74
0.84

0.58–0.67
0.65–0.89
0.59–0.77
0.75–0.90
0.47–0.65
0.70–0.85
0.77–1.16
0.57–0.87
0.69–1.02
0.68–0.80
0.58–1.11

0.98
0.90
0.93
0.98
0.91
0.96
0.85
0.84
0.93
0.98
0.70

k
Mean
mg1 − n Ln kg−1

95% CIh−1

0.003
0.00040.00160.00680.00060.00250.00090.00030.00330.00020.00060.0006–0.0054
0.0022–0.003
0.0006–0.0025
0.0045–0.0091
0.0014–0.0025
0.0003–0.0046
0.0024–0.0043
0.0015–0.002
0.0021–0.0044-0.0023 - 0.0027
0.0003–0.0009

R2

Sig.

0.85
0.08
0.90
0.96
0.22
0.76
0.21
0.06
0.96
0.03
0.91

*
ns
**
**
ns
*
ns
ns
**
ns
**

** = P value ≤ 0.01.
* = P-value ≤ 0.05.
ns = not signiﬁcant, P-value N 0.05.

loam soils equilibrated for 24 and 120 h (Fig. 1). Catlin and Sassafras
were selected to determine mass balance because they differed signiﬁcantly in a number of properties that are commonly associated withsorption behavior, such as OC and clay content, and pH of soil solution(Table 2). A full or close to full recovery was observed at 24 h for bothsoils with or without sterilization (Fig. 1, Table s2). However, sterilizedsoils adsorbed less DNAN (difference signiﬁcant for 24 h for both soils)(Table s2), possibly as a result of the impact of autoclaving on soil properties and resultant inﬂuence on adsorption (e.g., Xie and Mackenzie,
1991; Lotrario et al., 1995). The complete mass balance of DNAN obtained at 24 h means that calculation of sorbed concentrations and Kd values
from measures of solution-phase concentrations only are valid.
Complete DNAN recovery was not obtained at 120 h for either of thestudied soils for the unsterilized treatment. The smaller recoveries could
be the result of transformation, both abiotic and biotic, irreversible adsorption, or some combination thereof. Known transformation products
were not observed in solution.
The 24-h and 120-h recoveries were similar for the sterilized Sassafras soil, and were close to 100%. In addition, the 120-h recovery for theunsterilized treatment was much lower than for the sterilized treatment. These results indicate that the signiﬁcant mass loss observed forthe unsterilized Sassafras soil treatment is due almost exclusively to biotic transformation, with minor impacts of abiotic transformation or irreversible adsorption. Conversely, for the Catlin soil, the 120-h recovery
is lower than the 24-h recovery for the sterilized treatment. This indicates a contribution of abiotic transformation and/or irreversible
adsorption.
3.2.3. Adsorption isotherms
All studied soils adsorbed DNAN and the magnitude of adsorption
depended on the properties of the soil. The Kds ranged from 0.6 to
6.3 L kg−1 and the estimated retardation factors ranged between 3.5
and 27.5 (Table 3) indicating potentially signiﬁcant retardation of
DNAN in soil during transport. Catlin and Fort Harrison soils with highOC and CEC absorbed more DNAN from solution and had the highest retardation factors. Conductivity and pH of soil suspensions was not signiﬁcantly affected by addition of DNAN (not shown).
Both linear and Freundlich isotherms resulted in highly signiﬁcant
ﬁts to the measured data (Fig. 2). The parameter n, the exponent in
the Freundlich equation, ranged between 0.56 and 0.97. The 95% conﬁdence intervals of n estimates overlapped for several of the soils and for
Sassafras, Camp Guernsey and Camp Swift, n was not signiﬁcantly different from 1 (linear isotherm) (Table 3).
DNAN adsorption was best described by the Freundlich isotherm fora majority of the soils, however, for ﬁve soils, Camp Butner, Camp
Guernsey, Camp Gruber, Fort Harrison, and Camp Swift the linear

isotherm resulted in a better ﬁt to the data based on R2 value (Table3). Linear regressions were highly signiﬁcant, with Kd values different
from zero. Estimated mean log KOC (Kd normalized to OC) equaled
2.24 ± 0.20.
Both linear and Freundlich adsorption coefﬁcients for DNAN had ahighly signiﬁcant positive relationship with percent OC in soil (Fig. 3).
Neither Kd or Kf correlated to clay content, but a good correlation was
produced between Kf and the product of percent OC and clay content(Fig. s3). In addition, there was a highly signiﬁcant relationship between
both Kd and Kf and CEC. Signiﬁcant correlations were not obtained forother measured soils properties such as pH and SSA.
3.3. Transport studies
Breakthrough of the conservative tracer (Figs. 4 and 5) occurred at
1 pore volume (2.33 h), which indicates there was no preferential
ﬂow or air entrainment in the columns. The curves were sharp andFig. 1. Mass balance of DNAN in unsterilized and sterilized Catlin (a) and Sassafras (b) soils
for 24 and 120 h of contact. Soil to solution ratio was 1:60 for both soils. Error bars equal
conﬁdence interval of the mean (Table s2).

J.D. Arthur et al. / Journal of Contaminant Hydrology 199 (2017) 14–23

19

For Camp Swift soil, the Kd values estimated using HYDRUS-1D(1.22 ± 0.14 L kg− 1) and TMA (1.71 ± 0.36 L kg− 1) for DNAN were
not statistically different from each other. However, they are higher
than the estimated Kd from the batch experiments (0.60 ±0.09 L kg−1) (Table 4). These parameters could not be determined by
HYDRUS-1D for Camp Guernsey column experiments, but, Kds determined by TMA (1.13 ± 0.19 L kg−1) were similar to the estimated Kd
determined by batch experiments for DNAN in Camp Guernsey soil
(0.85 ± 0.17 L kg−1). The average DNAN retardation factors calculatedusing TMA were 8.5 for Camp Swift soil and 5.9 for Camp Guernsey.
Estimated mass-loss rate coefﬁcients, k, determined by HYDRUS-1D(0.046 ± 0.021 h−1) and TMA (0.053 ± 0.016) (Table 4) for DNAN in
Camp Swift soil were not statistically different according to a single factor ANOVA (P = 0.6). However, the mass-loss rate coefﬁcients werehigher than values for batch experiment data (0.0006 ± 0.0003 h−1).
This agrees with the fact that no transformation products of DNAN
were observed in the batch experiments. TMA estimates for mass-loss
rate coefﬁcients for Camp Guernsey (0.421 ± 0.088 h−1) were higher
than the batch study results (0.0033 ± 0.0011 h−1), as well. A Kd
value of 1.09 ± 0.72 L kg−1 was obtained for 2-ANAN in Camp Swiftsoil from application of HYDRUS-1D; 2-ANAN k values were not significantly different from zero.
3.3.1. DNAN mass balance in transport studies
DNAN added to the columns in solution was recovered in column efﬂuent and soil extracts as parent compound, as well as products of its
reduction, 2-ANAN and 4-ANAN. Mass balance calculations (Table 5) indicate that for Camp Swift soil on average all of the DNAN (mean ± CI:
102.0 ± 8.4%) was recovered as parent compound and 2-ANAN. For
Camp Guernsey soil, approximately half of DNAN was recovered(50.7 ± 20.7%). There was no signiﬁcant difference in total recoveries
between interrupted and continuous ﬂow experiments for either soil.
4. Discussion

Fig. 2. Adsorption isotherms calculated for DNAN in Catlin, Sassafras, and Plymouth soils.
Grey dashed line indicates linear adsorption isotherm ﬁt to the measured adsorption data(equation is in grey), while solid black line is a ﬁt of the Freundlich isotherm (equation inblack).

symmetrical, indicating ideal advective/dispersive transport. Longitudinal dispersivity values ranged from ~0.1 to ~3 cm (Table 4).
Figs. 4 and 5 show sample DNAN breakthrough curves for Camp
Swift and Camp Guernsey soils. DNAN breakthrough was observed
later than the conservative tracer bromide indicating adsorption to thesolid phase. DNAN transformation product 2-ANAN was observed in
all continuous and ﬂow interruption experiments, while 4-ANAN was
only observed in Camp Guernsey soil experiments. 2-ANAN and 4ANAN both exhibited retardation. Continuous ﬂow breakthrough curves
for Camp Swift soil were symmetrical (Fig. 4), while in Camp Guernsey
soil DNAN and its daughter compounds exhibited more complex behavior (Fig. 5): efﬂuent concentrations of DNAN decreased over time while
2-ANAN and 4-ANAN either continued at similar concentrations or also
decreased. During the ﬂow interruption experiments for Camp Swift, efﬂuent concentration decreased due to continuing transformation andthen increased again to a steady state value after resuming the experiment. The decrease in DNAN concentration during ﬂow interruption
was matched by an increase in 2-ANAN concentration. For Camp Guernsey soil, after the 24-h ﬂow interruption, no DNAN was detected but 2ANAN concentration increased. This observed behavior is consistent
with the impact of transformation reactions on transport.

This study examined the fate (adsorption and mass loss) of DNAN ineleven soils collected from training ranges across the United States. The
results are assessed and compared to TNT, a common and similar munitions compound. Implications of the correlations between fate andtransport parameters and soil properties for DNAN are discussed, as is
the potential that they may provide a tool for estimating these parameters for other soils.
Adsorption coefﬁcients ranged widely as would be expected for a diverse group of soils selected. Comparing these coefﬁcients to TNT adsorption coefﬁcients for Plymouth and Catlin soils showed higher
adsorption of DNAN in Plymouth soil (Kd of 4.4 L kg−1 for DNAN and
0.63–1.6 L kg−1 for TNT depending on the method used) (Dontsova etal., 2006) but less adsorption of DNAN in the Catlin soil (TNT Kd
17.9 L kg− 1 vs. DNAN Kd 6.1 L kg− 1) (Dontsova et al., 2009). The
Freundlich parameters were closer for the two compounds for the Catlinsoil (Kf = 45.6, n = 0.57 for DNAN and Kf = 32.67, n = 0.60 for TNT)
(Dontsova et al., 2009). Hawari et al. (2015) demonstrated a link between solubility, octanol-water partition coefﬁcient (Kow), and KOC for
DNAN, for several its transformation products, and for TNT. Solubility
followed the following order: TNT b DNAN b 2-ANAN b 4-ANAN
b DAAN whereas logKow and KOC followed the reverse order
DAAN b 4-ANAN b 2-ANAN b DNAN b TNT, so TNT had the lower solubility and the higher Kow and KOC than DNAN. Therefore, they predictedthat DNAN would be slightly more mobile than TNT in soil.
Our estimated mean log KOC (Kd normalized to OC) for DNAN was
2.24 ± 0.20, a value similar to one estimated for DNAN by Hawari etal. (2015) (2.45 ± 0.16), but also to values for TNT in soils (2.48–3.04)(US Department of Health and Human Services, 1995) and in water dispersible clay extracted from soils (2.65 ± 0.28) (Dontsova et al., 2009).
The low variability of KOC values as well as their consistent decrease
with decrease in log Kow implies that DNAN adsorbs to OC through20

J.D. Arthur et al. / Journal of Contaminant Hydrology 199 (2017) 14–23

Fig. 3. Correlation between measured DNAN Freundlich adsorptions coefﬁcients (Kfs) and percent organic carbon in soil (OC) (A); cation exchange capacity (CEC) (B); and linear
adsorptions coefﬁcients (Kds) and soil OC (C); CEC (D). All relationships were signiﬁcant at 95% conﬁdence level (P = 0.00011 for Kf vs. OC, P = 0.00061 for Kd vs. OC; P = 0.016 for Kf
vs. CEC and P = 0.0095 for Kd vs. CEC).

hydrophobic interactions. There were strong correlations between adsorption coefﬁcient and OC that supports this mechanism, however
the non-linear shape of the isotherms (Fig. 2) best described by the
Freundlich equation (Table 3) indicates that adsorption to the soils is
not solely based on partitioning to organic carbon.

Previous research conducted by Eriksson and Skyllberg (2001) studied the binding of TNT and its degradation products to soil organic matter, speciﬁcally looking at dissolved organic matter (DOM) and a twophase system of particulate organic matter (POM) and DOM. The resultsof their experiment with DOM showed that binding of TNT and its

Fig. 4. Breakthrough curves for DNAN and 2-ANAN in Camp Swift soil for continuous ﬂow
and ﬂow interruption (FI). DNAN inﬂow concentration was 2.87 μmol L−1 and2.64 μmol L−1 respectively for continuous and interrupted ﬂow experiments. Verticalsolid line indicates time of ﬂow interruption and dashed line indicates time when input
solution was switched back to background.

Fig. 5. Breakthrough curves for DNAN and 2-ANAN in Camp Guernsey soil for continuous
ﬂow and ﬂow interruption (FI). DNAN inﬂow concentration was 2.71 μmol L−1 and2.78 μmol L−1 respectively for continuous and interrupted ﬂow experiments. Verticalsolid line indicates time of ﬂow interruption and dashed line indicates time when input
solution was switched back to background.

J.D. Arthur et al. / Journal of Contaminant Hydrology 199 (2017) 14–23

21

Table 4Comparison of fate and transport parameters, longitudinal dispersivities, λ, linear adsorption coefﬁcients, Kd, and mass-loss rate coefﬁcients, k, for DNAN and 2-ANAN determined fromHYDRUS-1D and temporal moment analysis (TMA).
HYDRUS-1D

TMA

Bromide

DNAN

Soil

λ
cm
Estimate

95% CIKd
L kg−1
Estimate

Camp SwiftCamp SwiftCamp Swift FICamp Swift FI
Mean & CI

0.17
0.28
0.79
0.12
0.34

0.14
0.41
0.39
0.08
0.26

1.19
1.05
1.17
1.4
1.2

Camp GuernseyCamp GuernseyCamp Guernsey FICamp Guernsey FI
Mean & CI

0.15
3.35
0.37
0.77
1.16

0.53
4.1
0.37
0.76
1.45

n.a.
n.a.
n.a.
n.a.
n.a.

2-ANAN

95% CIkh−1
Estimate

0.06
0.04
0.09
0.12
0.08

0.028
0.041
0.039
0.076
0.046

n.a.
n.a.
n.a.
n.a.
n.a.

n.a.
n.a.
n.a.
n.a.
n.a.

95% CIKd
L kg−1
Estimate

0.005
0.01
0.055
0.009
0.019

1.93
1.46
0.38
0.55
1.08

n.a.
n.a.
n.a.
n.a.
n.a.

n.a.
n.a.
n.a.
n.a.
n.a.

DNAN

95% CIkh−1
Estimate

1.72
0.69
0.2
0.14
0.69

0.00001
0.00001
0.001
0.101
0.025

n.a.
n.a.
n.a.
n.a.
n.a.

n.a.
n.a.
n.a.
n.a
n.a

k
h−1
Estimate

R

95% CIKd
L kg−1
Estimate

0.000
0.000
0.087
0.03
0.039

1.28
1.9
1.56
2.11
1.71

0.03
0.064
0.06
0.058
0.053

5.58
8.94
6.92
9.24
7.67

n.a.
n.a.
n.a.
n.a
n.a

0.86
1.16
1.21
1.28
1.13

0.494
0.467
0.295
0.427
0.421

4.64
6.23
6.06
6.49
5.85

Estimate

Note: Bulk density (ρ) was determined by the mass of the air-dried soil used to pack the column and saturated water content (θ) was determined from the weight of the water need tosaturate the column. The estimated bulk density for Camp Swift was 1.54 ± 0.02 and saturated water content 0.40 ± 0.02. Camp Guernsey estimated bulk density was 1.62 ± 0.02 andsaturated water 0.38 ± 0.01. n.a- data not available from HYDRUS.

degradation products was greatly increased with increasing pH, whichindicated that negatively charged weak acid groups in DOM are involved in binding. The results of the two-phase system showed thatbinding of TNT and its degradation products to POM was less pH dependent than found for DOM. The suggested mechanism of TNT binding to
POM was due to hydrophobic partitioning because the POM has ahigher density of domains with hydrophobic character than DOM. We
did not observe a signiﬁcant relationship with pH for DNAN possibly
due to working with whole soils that would have a mixture of different
domains.
Other researchers also suggested that TNT and other nitroaromaticcompounds alike bind to organic matter by non-hydrophobic interactions. Zhang and Zhu (2009) who investigated the mechanism of adsorption of nitroaromatics to soils suggested that non-hydrophobic
sorptive interaction between nitroaromatics and soil organic matter
was primarily due to the π-π interactions. Nitroaromatics are strong π
acceptors and if soil organic matter contains several aromatics rings
within it structure then π-π interactions/stacking can occur hence binding DNAN to the soil organic matter. Since the chemical structure of
DNAN is similar to TNT and other nitroaromatic compounds, it should
behave similarly in organic matter.
Linker et al. (2015) demonstrated that similarly to TNT, DNAN can bealso adsorbed by phyllosilicate clays with amounts adsorbed increasing
when clays are saturated with cations that are not highly hydrated, as
was previously reported for nitroaromatic compounds (Haderlein etal., 1996). The mechanism of adsorption was coplanar electron donoracceptor (EDA) formation with oxygen ligands at the external siloxane
surface of clay as e−-donors and the π-system of the NACs as e−-acceptor according to Haderlein et al. (1996) and exchangeable cation-DNAN
complexation or bridging according to Linker et al. (2015).
Observed correlation between DNAN adsorption coefﬁcients and
CEC conﬁrms that both organic matter and clay adsorb DNAN, since
CEC is usually inﬂuenced by the amount and type of clay, as well as organic matter content on the soil (Essington, 2015). The lack of the link
between clay content alone and DNAN Kds and Kfs may be caused byclay fraction of the soil being composed of different minerals, only
some of which are phyllosilicates, or of phyllosilicates with different
reactivity.
Irrespective of the adsorption mechanism, the strong correlations
that have been observed between DNAN adsorption coefﬁcients andOC give us a good predictive capability. Since the soils tested from training ranges across the United States have a wide range of values for mainsoil properties, the strong correlation that exists between Kds and Kfs
and OC can be used to estimate adsorption based on measured OC for
any soil.
We observed mass loss of DNAN over time in both batch and column
experiments. However, measured rates and whether transformation
products were detected differed. We did not detect any DNAN transformation products in solution in batch studies despite decrease in DNAN
recovery at 120 h. One explanation may be that DNAN transforms toTable 5Mass of added DNAN recovered in efﬂuent and in soil during column transport experiments (%).
Solution recoveries, %Soil recoveries, %

Soil

DNAN

2-ANAN

4-ANANDNAN

2-ANAN

4-ANAN

Total, %(Solution + soil)Camp SwiftCamp SwiftCamp Swift FICamp Swift FI
MeanCICamp GuernseyCamp GuernseyCamp Guernsey FICamp Guernsey FI
Mean
CI

91.9
85.0
83.0
59.3
79.8
13.9
3.4
4.8
5.9
2.0
4.0
1.7

8.5
10.3
4.0
21.6
11.1
7.3
19.5
24.9
24.0
11.7
20.0
5.9

0.0
0.0
0.0
0.0
0.0
0.0
0.9
28.6
11.4
44.1
12.7
12.5

8.0
4.5
4.5
5.8
5.7
1.6
0.0
7.2
2.3
1.2
2.7
3.1

4.0
0.0
4.0
5.2
3.3
2.2
4.7
9.0
11.4
0.5
6.4
4.7

1.8
1.9
1.9
2.9
2.1
0.5
4.2
5.7
3.9
6.3
5.0
1.1

114.2
101.7
97.4
94.8
102.0
8.4
32.7
80.2
58.8
65.9
50.7
20.7

FI = ﬂow interruption for 24 h.

22J.D. Arthur et al. / Journal of Contaminant Hydrology 199 (2017) 14–23

its amino reduction products with consequent irreversible adsorption ofthese products to the soil organic matter. This has been observed for the
DNAN and its products, ANAN and DAAN, by Hawari et al. (2015), andfor TNT and DNTs, which has similar transformation pathways andstructure of their reduced products, by Thorn et al. (2002, 2008). It
would be expected that this mechanism would play bigger role in
DNAN fate when large amount of organic matter is available in thesoil. However, in mass balance studies despite large differences in OC
content between the soils there was no signiﬁcant difference in theamount of DNAN unrecovered at 120 h. It is also possible that DNAN degraded to products that were not analyzed.
In column studies, estimated mass-loss rate coefﬁcients, k, were signiﬁcantly higher than values determined in batch experiments. In addition we measured 2-ANAN in both soils and 4-ANAN in Camp Guernsey
soil. The absence of agitation in the column experiments can result in adecrease in O2 content of the solution as microorganisms consume it in
respiration. If anaerobic conditions result they can promote reduction of
nitro to amino groups in DNAN. However, we did not measure O2 content or redox potential of solutions, so cannot conﬁrm this.
No relationships were observed between mass loss and any of themeasured soil properties. Based on one-electron standard reduction potentials DNAN has lower tendency for nitro to amino group reductions
than TNT (Salter-Blanc et al., 2015). The mass-loss rate for DNAN was
slower than the ones previously observed for TNT in one of the studied
soils. In Plymouth soil, TNT transformation rate was measured to be
0.21 h−1 (Dontsova et al., 2006) while the DNAN rate coefﬁcient ofmass loss in batch studies was 0.0068 h−1. However, measurements
were done in batch study for DNAN and in column study for TNT andsince experimental design was shown to affect mass-loss rate coefﬁcients, we cannot make direct comparisons between these two values.
5. Conclusion
This study examined the adsorption and mass loss behavior of DNAN
in eleven different soils, as well as its transport behavior in a subset ofthese soils. The equilibrium adsorption data were ﬁtted to Freundlich
and linear isotherms with the Freundlich isotherm resulting in slightly
better ﬁt on average. A strong relationship between both linear andFreundlich adsorption coefﬁcients (Kd and Kf) and % OC and CEC indicates that DNAN's fate would be greatly inﬂuenced by organic matterand clays in the soils. Our measured adsorption values make it possible
to predict DNAN's behavior in other soils. In transport studies, we conﬁrmed that DNAN adsorbs to soils delaying the arrival of the contaminant to the ground water by a factor of six relative to the tracer evenfor sandy soil with little organic carbon. We also showed that underﬂow conditions DNAN transforms readily to the amino products, 2ANAN and 4-ANAN. DNAN's soil adsorption, and often signiﬁcant massloss, indicates that DNAN is naturally attenuated in the soils.
Acknowledgements
This work was funded by the Strategic Environmental Research andDevelopment Program, SERDP, project ER-2220. We are grateful to Anthony Di Stasio and Erika Rivera, US Army Armament Research, Development and Engineering Center (ARDEC), Picatinny Arsenal for
providing DNAN; Bonnie M. Packer, Rosa Gwinn, Lisa DeGrazia, Bethany
Keller, Jessica Milose, Amibeth Sheridan, Laurie Stenberg, Sarah Gettier,Army National Guard–Environmental Directorate and URS Corporation,
Germantown, MD and Mike Heitmann, CH2M HILL Englewood, CO forcollecting soils used in the experiments on Army National Guard
installations.
Supplementary data
Supplementary material

References
Boddu, V., Abburi, K., Fredricksen, A., Maloney, S., Damavarapu, R., 2009. Equilibrium andcolumn adsorption studies of 2,4-dinitroanisole (DNAN) on surface modiﬁed granular activated carbons. Environ. Technol. 30, 173–181.
Boddu, V.M., Abburi, K., Maloney, S.W., Damavarapu, R., 2008. Thermophysical propertiesof an insensitive munitions compound, 2,4-dinitroanisole. J. Chem. Eng. Data 53,
1120–1125.
Braida, W., Strickland, D., Balas Hummers, W., Koutsospyros, A., Ogundipe, A., Su, T.-L.,
Tuna, G.S., Kalomoiri, A., Pavlov, J., Dhedia, D., 2011. Vadose Zone Transport of Munitions Components. US ARMY RDECOM/ARDEC, Picatinny Arsenal, New Jersey.
Brunauer, S., Emmett, P.H., Teller, E., 1938. Adsorption of gases in multimolecular layers.
J. Am. Chem. Soc. 60, 309–319.
Brusseau, M.L., Hu, Q., Srivastava, R., 1997. Using ﬂow interruption to identify factors
causing nonideal contaminant transport. J. Contam. Hydrol. 24, 205–219.
Brusseau, M.L., Rao, P.S.C., Jessup, R.E., Davidson, J.M., 1989. Flow interruption: a method
for investigating sorption nonequilibrium. J. Contam. Hydrol. 4, 223–240.
Davies, P.J., Provatas, A., 2006. Characterisation of 2,4-Dinitroanisole: An Ingredient for
Use in Low Sensitivity Melt Cast Formulations. Weapons Systems Division, Defence
Science and Technology Organisation.
Dodard, S.G., Sarrazin, M., Hawari, J., Paquet, L., Ampleman, G., Thiboutot, S., Sunahara, G.I.,
2013. Ecotoxicological assessment of a high energetic and insensitive munitions compound: 2,4-dinitroanisole (DNAN). J. Hazard. Mater. 262, 143–150.
Dontsova, K.M., Hayes, C., Pennington, J.C., Porter, B., 2009. Sorption of high explosives towater-dispersible clay: inﬂuence of organic carbon, aluminosilicate clay, and extractable iron. J. Environ. Qual. 38, 1458–1465.
Dontsova, K.M., Yost, S.L., Simunek, J., Pennington, J.C., Williford, C.W., 2006. Dissolution
and transport of TNT, RDX, and composition B in saturated soil columns. J. Environ.
Qual. 35, 2043–2054.
Eriksson, J., Skyllberg, U., 2001. Binding of 2,4,6-trinitrotoluene and its degradation products in a soil organic matter two-phase system. J. Environ. Qual. 30, 2053–2061.
Essington, M.E., 2015. Soil and Water Chemistry: An Integrative Approach. second ed. CRC
Press.
Haderlein, S.B., Weissmahr, K.W., Schwarzenbach, R.P., 1996. Speciﬁc adsorption of
nitroaromatic explosives and pesticides to clay minerals. Environ. Sci. Technol. 30,
612–622.
Hawari, J., Monteil-Rivera, F., Perreault, N.N., Halasz, A., Paquet, L., Radovic-Hrapovic, Z.,
Deschamps, S., Thiboutot, S., Ampleman, G., 2015. Environmental fate of 2,4dinitroanisole (DNAN) and its reduced products. Chemosphere 119, 16–23.
Jurgensen, H., 2000. DoD Moving Toward Long-term Goal of IM-compliant Inventory. PM.
pp. 32–34.
Liang, J., Olivares, C., Field, J.A., Sierra-Alvarez, R., 2013. Microbial toxicity of the insensitive
munitions compound, 2,4-dinitroanisole (DNAN), and its aromatic amine metabolites. J. Hazard. Mater. 262, 281–287.
Linker, B.R., Khatiwada, R., Perdrial, N., Abrell, L., Sierra, R., Field, J.A., Chorover, J., 2015.
Adsorption of novel insensitive munitions compounds at clay mineral and metaloxide surfaces. Environ. Chem. 12, 74–84.
Lotrario, J.B., Stuart, B.J., Lam, T., Arands, R.R., O'Connor, O.A., Kosson, D.S., 1995. Effects ofsterilization methods on the physical characteristics of soil: implications for sorption
isotherm analyses. Bull. Environ. Contam. Toxicol. 54, 668–675.
Mark, N., Arthur, J., Dontsova, K., Brusseau, M., Taylor, S., 2016. Adsorption and attenuation behavior of 3-nitro-1,2,4-triazol-5-one (NTO) in eleven soils. Chemosphere
144, 1249–1255.
McDonald Jr., L.M., Evangelou, V.P., 1997. Optimal solid-to-solution ratios for organic
chemical sorption experiments. Soil Sci. Soc. Am. J. 61, 1655–1659.
Olivares, C., Liang, J., Abrell, L., Sierra-Alvarez, R., Field, J.A., 2013. Pathways of reductive
2,4-dinitroanisole (DNAN) biotransformation in sludge. Biotechnol. Bioeng. 110,
1595–1604.
Ro, K.S., Venugopal, A., Adrian, D.D., Constant, D., Qaisi, K., Valsaraj, K.T., Thibodeaux, L.J.,
Roy, D., 1996. Solubility of 2,4,6-trinitrotoluene (TNT) in water. J. Chem. Eng. Data41, 758–761.
Roy, W.R., Krapac, I.G., Chou, S.F.J., Grifﬁn, R.A., 1992. Batch-type Procedures for Estimating Soil Adsorption of Chemicals. Risk Reduction Engineering Laboratory, Cincinnati,
OH (100 pp.).
Saad, R., Radovic-Hrapovic, Z., Ahvazi, B., Thiboutot, S., Ampleman, G., Hawari, J., 2012.
Sorption of 2,4-dinitroanisole (DNAN) on lignin. J. Environ. Sci. 24, 808–813.
Salter-Blanc, A.J., Bylaska, E.J., Johnston, H.J., Tratnyek, P.G., 2015. Predicting reduction
rates of energetic nitroaromatic compounds using calculated one-electron reduction
potentials. Environ. Sci. Technol. 49, 3778–3786.
Shukla, M.K., Poda, A., 2016. Adsorption of emerging munitions contaminants on cellulose
surface: a combined theoretical and experimental investigation. Bull. Environ.
Contam. Toxicol. 96, 784–790.
Šimůnek, J., van Genuchten, M.T., Šejna, M., 2008. Development and applications of the
HYDRUS and STANMOD software packages, and related codes. Vadose Zone J. 7,
587–600.
Site, A.D., 2001. Factors affecting sorption of organic compounds in natural sorbent/water
systems and sorption coefﬁcients for selected pollutants. A Review. J. Phys. Chem. Ref.
Data 30, 187–439.
Stanley, J.K., Lotufo, G.R., Biedenbach, J.M., Chappell, P., Gust, K.A., 2015. Toxicity of theconventional energetics TNT and RDX relative to new insensitive munitions constituents DNAN and NTO in Rana pipiens tadpoles. Environ. Toxicol. Chem. 34, 873–879.
Taylor, S., Park, E., Bullion, K., Dontsova, K., 2015. Dissolution of three insensitive munitions formulations. Chemosphere 119, 342–348.
Taylor, S., Ringelberg, D.B., Dontsova, K., Daghlian, C.P., Walsh, M.E., Walsh, M.R., 2013. Insights into the dissolution and the three-dimensional structure of insensitive munitions formulations. Chemosphere 93, 1782–1788.

J.D. Arthur et al. / Journal of Contaminant Hydrology 199 (2017) 14–23
Thorn, K.A., Kennedy, K.R., 2002. 15N NMR investigation of the covalent binding of reduced TNT amines to soil humic acid, model compounds, and lignocellulose. Environ.
Sci. Technol. 36, 3787–3796.
Thorn, K.A., Pennington, J.C., Hayes, C.A., 2002. 15N NMR investigation of the reduction
and binding of TNT in an aerobic bench scale reactor simulating windrowcomposting. Environ. Sci. Technol. 36, 3797–3805.
Thorn, K.A., Pennington, J.C., Kennedy, K.R., Cox, L.G., Hayes, C.A., Porter, B.E., 2008. N-15
NMR study of the immobilization of 2,4- and 2,6-dinitrotoluene in aerobic compost.
Environ. Sci. Technol. 42, 2542–2550.
U. S. Environmental Protection Agency, 1986. SW846 method 9081. Cation-Exchange Capacity of Soils (Sodium Acetate). Ofﬁce of Solid Waste and Emergency Response,
Washington, DC.
U. S. Environmental Protection Agency, 2006. SW846 method 8330b. Nitroaromatics,
Nitramines, and Nitrate Esters by High Performance Liquid Chromatography(HPLC). Ofﬁce of Solid Waste and Emergency Response, Washington, DC.

23

U.S. Environmental Protection Agency, 2010. Standard operating procedure for analysis of
total organic carbon in sediments (dry combustion, IR detection), revision 04. Sampling and Analytical Procedures for GLNPO's Open Lake Water Quality Survey of theGreat Lakes (EPA 905-R-05-001).
US Department of Health and Human Services, 1995. Toxilogical Proﬁle for 2,4,6-trinitrotoluene. Sciences International, Inc., pp. 87–113.
Walsh, M.R., Walsh, M.E., Ramsey, C.A., Brochu, S., Thiboutot, S., Ampleman, G., 2013. Perchlorate contamination from the detonation of insensitive high-explosive rounds.
J. Hazard. Mater. 262, 228–233.
Xie, R.J., Mackenzie, A.F., 1991. Effects of autoclaving on surface properties and sorption ofphosphate and zinc in phosphate-treated soils. Soil Sci. 152, 250–258.
Zhang, D., Zhu D, W:, C., 2009. Sorption of nitroaromatics to soils: comparison of the importance of soil organic matter versus clay. Environ. Toxicol. Chem. 28, 1447–1454.