remediation

REMEDIATION Sorption of Low Molecular Mass Polycyclic Aromatic Hydrocarbons to Organic Carbon Deficient Aquifer Materials Coated with Residual Diesel Oil RONDALL J. HUDSONa, IRENA D. ATANASSOVAb, BRUCE E. HERBERTc GARY L. MILLS50 µm), 1.5 % silt (2-50 µm), 7.0 % course clay (0.2-2 µm), and 5.7 % fine clay(< 0.2 µm). X-ray diffraction analysis identified quartz and koalini te as the major minerals in the sand and clay fractions, respectively. The cation exchange capacity (CEC) of the clay fraction was determined by Ca-Mg exchange, followed by AAS measurement. It was 10.8 cmolckg- 1 for Scientific Research Papers: Remediation

Table 1. Selected physical and chemical properties of the Tobacco Road Sand Particle size (µm) Share of fraction (%) Sand(> 50)

85.1

Silt (2-50)

1.5

Coarse Clay (0.2-2)

7.0

Fine Clay (< 0.2)

5.7

Mineral composition Sand

Q,F

Silt

Q,M,GO

Coarse Clay

K, V,M,GI,C

Fine Clay

K, V,M,GI

CEC cmolckg-1

13.4 ± 0.1

(Fine Clay) 1.8 *Q- guartz; F - feldspar; M - mica; V -vermiculite; GO - goethite; GI - gibbsite; C - crandallite; •• standard deviation of duplicate trials.

the coarse clay and 13.4 cmolckg- 1 for the fine clay fraction. Selected physical and chemical properties are presented in Table 1. A set of aquifer material samples was prepared, which had diesel oil concentrations from 0 to 0.02 % of mass. After being oven dried and passed through a 2 mm sieve, the aquifer material was coated by placing a measured mass of diesel oil in a flask containing a measured mass of aquifer material. The flask was then rotated by a rotary evaporator without a vacuum until a well-mixed sample was obtained. Trace carbon analysis was conducted

on each sample using high temperature combustion method (Leco Model CR12 system with infrared detection at Huffman Laboratories, Inc. in Golden, Colorado (Table 2). Results of the total carbon analysis show that the uncontaminated Tobacco Road Sand has a low organic carbon content(< 0.1 %), which is typical of aquifer materials in this region (Lion et al., 1990). Column Apparatus. A column apparatus was used to simulate saturated aquifer conditions. It consisted of a heavy-walled borosilicate glass chromatography column (Kontes, Vineland, NJ, Part No. 420870-1510) with an ad-

Journal of Balkan Ecology, vol. 19, No 1, 2016

71

Table 2. Aquifer material treatments Oil content Organic carbon

(%)

(%)

0 0.005 0.01 0.014 0.02

0.020 0.030 ± 0.001 0.033 ± 0.001 0.035 ± 0.002 0.045 ± 0.001

justable bed height (1-13 cm height, 2.5 cm I.D.) filled with aquifer material. A 0.4 mm PTFE Teflon screen was used as a bed support on both ends of the column to enhance radial distribution of the influent fluid, and reduce dispersion at the effluent. The column was mounted vertically with fluids pumped upwards to help prevent compaction and ensure saturated conditions. The pumping rate was constant at 0.2 ml/min and is in the upper range of subsurface flow at the SRS. All columns were loaded to a 5.0 cm bed height at a bulk density (bp) of 1.5 ± 0.03 g/cm3 and 0.43 ± 0.02 porosity (n). Loading was done in 2.5 cm layers to ensure uniform packing. After each layer was added, the aquifer material was compacted by gently tapping the column on its bottom. A single piston pump (Fluid Metering, Inc., Oyster Bay, NY, Model (QG6-QOSSY) with a variable stroke length drew fluid from one of two 2 1 fluid reservoirs. Pumping was switched by a three-way valve between the reservoirs, one with a tracer (reactive or nonreactive) and one without. A second three-way valve was located between the pump and the column to allow fluids to bypass the column when necessary. The fluid reservoirs (Ace Glass, Vineland, NJ, and Part No. 5414-143) were constructed of heavy-wall borosilicate glass with a UV resistant plastic outer coating. All tubing, valve com72

Column number

1 2 3 4

5

ponents, fittings and connectors that came in contact with the fluids were constructed of PTFE Teflon or ETFE Tefzel. The system was maintained at 25°C by immersing the fluid reservoirs in a water bath, and continuously pumping water through a jacket surrounding the column. Samples were collected from the column effluent with a fraction collector (Gilson Model 215). Solutions and Tracers. A dilute (0.005 M) CaCh solution was used as a background electrolyte to help prevent clay dispersion. To sterilize the electrolyte solution and the aquifer material, 0.0002 % of mass sodium azide (NaN3) was added to the aqueous solution. Before injection of the tracers, the system was equilibrated by passing at least 10 pore volumes of electrolyte solution through the column. Three reactive tracers were used, which included the polycyclic aromatic hydrocarbons dibenzothiophene, acenapthene and fluorene. The compounds were selected because they have a range of properties and are common components of diesel oil. The Kow and Koc decrease in the following order: for acenaphthene, log Kow = 3.98, log Koc= 3.66 < fluorene, log Kow = 4.18, log Koc= 3.86 < dibenzothiophene log Kow = 4.38, log Koc = 11.23 (H an s c h et al., 1995; Hasse t et al., 1980; Site, 2001; USPHS, 1990). All reactive tracers were deuterium-labeled compounds (C/D/N Isotopes, Inc., Vaudreuil, Scientific Research Papers: Remediation

.

Quebec). To increase the sensitivity and selectivity for the analysis of the tracer compounds the mass spectrometer was operated in selective ion monitoring (SIM) mode. Aqueous solutions were prepared by first making a stock solution of the deuterated compound(s) in methanol. Then 1.0 ml of the stock solution was spiked into 1 1 solutions of dilute (0.005 M) CaCh with 0.0002 % of mass (NaN3). The resulting spiked solutions had deuterated compound concentrations that were about 75 % of their aqueous solubility. However, concentrations were expected to vary due to sorption by the glass walls of the fluid reservoir. The spiked solutions were allowed to equilibrate for 24 hours while being stirred on a stir plate, and then used immediately. The small amount (0.1 % by volume) of methanol in the spiked solutions was not expected to have an observable effect on the sorption of organic solutes by aquifer material (B a ck h us et al., 1990). PAH tracers in the effluent fractions were concentrated and prepared for GC/MS analysis immediately after collection by using solid-phase extraction (SPE). Aqueous samples were directly processed through C1s SPE column using a vacuum ap.riaratus (Burdick & Jackson Inert SPE M). Then the retained PAH were eluted with methanol and o-terphenyl was added as an internal standard. The bromide ion (Br) was used as the nonreactive tracer. It was injected into the column as a 0.1 M CaBf2 solution. The bromide tracer was detected by using a selective ion analyzer with a bromide sensitive electrode.

mes. The value C represents the effluent concentration, and Co is the initial input concentration determined by analyzing samples directly from the fluid reservoir. The BTCs were modeled with the one-dimensional advective-dispersive transport model, CXTFIT (T o r i d e et al., 1995) which uses a non-linear least-squares regression method to quantify the retardation factor (R), dispersion coefficient (D), and tracer velocity (v). The model was set to consider conditions of linear equilibrium sorption with continuous tracer input and flux averaged output concentrations. For the nonreactive tracer (bromide), D and v were fitted and R was fixed at 1. When the reactive tracers were modeled, D and R were fitted and v was fixed at the bromide velocity. RESULTS AND DISCUSSION

re constructed by plotting the relative concentration (C/Co) of each tracer versus the number of column pore volu-

Representative breakthrough curves (BTCs) from the column experiments are presented in Fig. 2. The bromide BTCs show a step input with very little tailing, indicating that hydrodynamic dispersion was low due to homogeneous well-packed columns. Thus, any non-ideal effects by hydrodynamic dispersion on contaminant sorption would be minimal. The BTCs for the reactive tracers have sigmoidal shapes and level off at one, which is characteristic of organic solutes exhibiting equilibrium sorption Relative displacement of the BTCs is consistent with the solute properties showing an increase in retardation with an increase in Koc and octanol-water partition coefficient (Kow) and a decrease in water solubility. Transport parameters obtained from modeling the BTCs with CXTFIT are shown in Table 3. Sorption coefficients (K) for each organic solute (Table 4) can be calculated by using the retar-

Journal of Balkan Ecology, vol. 19, No 1, 2016

73

Determining Transport Parameters. Breakthrough curves (BTCs) we-

dation values (R) generated by CXTFIT and the following equation:

(3) R= 1 + (bp/n)K where bp is the standard bulk density (g/cm3) and n is the porosity. A plot of K versus percent oil content (by mass) (Fig. 3) clearly shows that residual diesel oil increases the sorptive properties of the aquifer material. It also demonstrates that the sorption of the three P AHs increased linearly through the range of residual-oil contents. This indicates that the sorptive effects of diesel oil are additive. A comparison of K values for clean sand and oil-treated sand shows that weathered diesel oil increases PAHs sorption from 2 to 10 times through the given range of oil concentrations. If we consider the diesel-coated aquifer material as a three phase system, the following equation can be written: (4) K = f ocKoc + f minKmin + f oi!Koil where focKoc represents sorption to natural organic carbon, fminKmin sorption to minerals and foi!Koil partitioning to residual oil. To calculate the oil phase contribution to K, equation (4) can be rearranged as follows: (5) foi!KoiJ= K - focKoc - f minKmin Measured K values from the untreated column (1) were substituted for the combined effects of focKoc and fminKmin in equation (5), and the term foi!Koil was calculated for each of the PAHs used in the oil-treated columns. It was assumed that focKoc stayed constant as the oil content changed. A plot of the oil phase contribution to K shows linear relationships which can be projected to the origin, suggesting that only a minute amount of diesel oil

74

is necessary to act as a separate sorptive phase (Fig. 4). This is in contrast to the "threshold" concentration of S u n et al., (1991) above which PCB oil functions as a separate partitioning phase. J o n k e r et al. (2003) found that for the sediment used in their experiment (0.82 % OC), the concentrations at which the oil forms significant amount of separate phases (critical separate phase concentration CSPC) are between 0.1 and 0.3 %. The Koc values (Table 5) based on total carbon for oil-treated sediment are greater than those for clean sediment. This suggests that weathered diesel oil is a more effective sorptive phase than • natural organic carbon. Oil-water sorption coefficients (Koii) were determined from the slope of the lines in Fig. 3 for: acenapthene (Koii = 11500 ± 800), fluorene (Koii = 17300 ± 600), and dibenzothiophene (Koii = 29800 ± 400), and compared to literature Koc values. Weathered diesel oil is about 3 times more effective as a sorptive phase for the PAHs investigated than natural organic carbon per unit mass. The Koi1 values listed above fall within the range of Kow values (H a n s c h et al., 1995; Site, 2001; USP HS, 1990). When Kow was substituted for Koil in equation (4), reasonable estimates for K were calculated for all three organic compounds (e.g., K from 0.52 to 1.20 for acenapthene with 0.005 % oil). This suggests octanol and weathered diesel oil behave similarly as organic partitioning phases for the given solutes. However, it is uncertain if this relationship will hold true as weathering changes the nature (i.e., polarity) of diesel oil, or for more polar solutes. Octanol, which is an amphipathic solvent, would tend to favor slightly polar compounds more than a nonpolar residual hydrocarbon phase. Scientific Research Papers: Remediation

• Acenapthene •Fluorene ,., Dibenzothiophene xBromide

(a)

1,4 1,2

0 (.) (.)

-

.. .. ·' . .

~.···•• ••• • • •1. , x+

1 0,8

x

0,6

x

0,4

X+

0,2

••

.... •

... .........

••• ·.,

i

~ I

•'"'""'

.A

x ....

0

0

5

10 Pore Volume

15

• Acenapthene • Fluorene .a. Dlbenzothlophene xeromide

(b)

1,2 0

1

~

(.) 0,8

x

0,6

x

•

0,4

x 0,2

x 0

• •• • • •• 5

10

15 20 Pore Volume

25

30

Fig. 2. Breakthrough curves for bromide and PAHs through (a) clean aquifer material and (b) aquifer material coated with 0.01 % of mass of weathered diesel oil

Journal of Balkan Ecology, vol. 19, No 1, 2016

75

Table 3. Transport parameters generated by CXTFIT for the P AHs Acenapthene Dibenzothiophene Oil Fluorene content (%)

R

r2

R

r2

R

r2

0

1.36 ± 0.04

0.97

2.05 ± 0.08

0.97

3.37 ± 0.15

0.96

0.005

3.36 ± 0.53

0.96

5.42 ± 0.14

0.97

8.91±0.09

0.99

0.010

6.23 ± 0.11

0.98

9.11±0.16

0.97

18.3 ± 0.11

0.99

0.014

6.63 ± 0.09

0.98

9.61±0.10

0.99

18.9 ± 0.07

1.00

0.020

9.78 ± 0.11

0.98

14.7 ± 0.15

0.98

Table 4. Sorption coefficients Oil content

K (ml/g)

Acenapthene

Fluorene

Dibenzothiophene

0

0

0.106

0.311

0.701

0.005

0.672

1.26

2.25

0.010

1.32

2.05

3.72

0.014

1.54

2.62

4.87

0.020

2.48

3.86

ND a

Table 5. Calculated Koc values based on total organic carbon

Koc=K/foc Fluorene

Dibenzothiophene

534

1560

3500

2

2240

4190

7510

3

4010

6220

11300

4

4390

7490

13900

5

5520

8580

Column

76

Acenapthene

Scientific Research Papers: Remediation

--

8 7

~

4

... ~ 'E c v

.~

0 0

c

0

• Acenapthene •Fluorene ,;. Dibenzothiophene

6

"'

1

//

/~

... ....--------_---------_._--~ -------· //

3 2

//

//

5

a... 0

l

__________

//

~

0 0

0,005

0,01

0,015

% oil w/w ~-·---

-----·---

0,02 --- - - - -

0,025 ---~

Fig. 3. Relationship between the sorption coefficient (K) for each PAH compound and the % of oil in each column

+Acenapthene •Fluorene • Dibenzothiophene

---,

0,025 %oilw/w

Fig. 4. Relationship between the oil phase contribution to the sorption coefficient (K) and the content(%) of oil in each column

Journal of Balkan Ecology, vol. 19, No 1, 2016

77

CONCLUSION Our key findings are the following. Weathered diesel oil in aquifer material deficient in natural organic matter (foe= 0.0002) acts both as a source and a highly effective sorptive phase for HOCs in solution. Only a minute amount, 0.005 % of mass (50 µg/g) of moderately weathered diesel oil was needed to affect the sorption of the three PAHs, acenaphthene, fluorine, and dibenzothiophene. Measured sorption coefficients increased linearly with the oil content, indicating that the sorptive effects of diesel oil are additive. Comparison between experimental Koil values and published Koc values indicated that weathered diesel oil is a more effective sorptive phase than natural organic matter per unit mass. In addition, octanolwater partition coefficients (Kow) for the three solutes were found to be reasonable estimates for Koil values. The consequence of enhanced P AHs sorption to weathered diesel oil-coated aquifer material is decreased overall mobility of low molecular weight P AHs. This will affect the remediation strategies for aquifer systems contaminated with diesel oil. Pump and treat systems may require larger volumes of water and longer pumping times to remove the contaminants than expected from estimates that do not consider the sorptive effects of diesel oil. Assuming decreased P AHs mobility in the vapour phase also occurs, removal of volatile components by vacuum extraction may also take longer than expected. When applying mathematical transport models that use the mass fraction of natural organic carbon and published carbon-normalized sorption coefficients (Koc) values, modifications should be made to consider the sorption of P AHs to weathered diesel oil.

78

Acknowledgments. This research was supported by Contract DE-AC0976SR00-819 between the University of Georgia and the U.S. Department of Energy. REFERENCES Backhus, D. A., P. M. Gschw e n d. 1990. Fluorescent Polycyclic Aromatic Hydrocarbons as Probes for Studying the Impact of Colloids on Pollutant Transport in Ground Water. - Environmental Science and Technology, 24, 1214-1223. Chi, F. H., G. L. Amy. 2004. Transport of Anthracene and Benz(a)anthracene through Iron-quartz and Three Aquifer Materials in Laboratory Columns. - Chemosphere, 55, 515-524. C h r i s t e n s e n, L. B., T. H. L a r sen. 1993. Method for Determining the Age of Diesel Oil Spills in the Soil. - Ground Water Monitoring and Remediation, 23, 142-149. C 1 in e, P. V., J. J. D e 1fin o, P. S. Rao. 1991. Partitioning of Aromatic Constituents into Water from Gasoline and Other Complex Solvent Mixtures. - Environmental Science and Technology, 25, 914-920. C or n e 1i s s en, G., 0. Gust a f s s on, T. D. B u ch e 1 i, M. T. 0. Jo n k e r, A. A. K o e 1 m an s, van P. C. M. Noor t. 2005. Extensive Sorption of Organic Compounds to Black Carbon, Coal, and Kerogen in Sediments and Soils: Mechanisms and Consequences for Distribution, Bioaccumulation, and Biodegradation. - Environmental Science and Technology, 39, 6881-6895. Grat h w oh 1, P. 1990. Influence of Organic Matter from Soils and Sediment from Various Origins on the Sorption of Some Chlorinated Aliphatic Hydrocarbons: Implications Scientific Research Papers: Remediation

on Koc correlation. - Environmental Science and Technology 24, 16871693. Ha 1 e, S. E, S. Kwon, U. G ho sh, D. Werner. 2010. Polychlorinated Biphenyl Sorption by Activated Carbon and the Attenuation Caused by Sediment. - Global NEST Journal, 12, 318-326. Hansch, C., A. Le o, D. Hoek man. 1995. Exploring QSAR- Hydrophobic, Electronic, and Steric Constants. Washington, DC: American Chemical Society, p. 96 H a s s e t t, J. J., J. C. M e an s, W. L. B an wart, S. G. W o o d, S. A 1 i, A. K h a n. 1980. Sorption of Dibenzothiophene by Soils and Sediments. - Journal of Environmental Quality, 9, 184-186. Jonker, M. T. 0., A. A. Koe 1 m an s. 2002. Sorption of Polycyclic Aromatic Hydrocarbons and Polychlorinated Biphenyls to Soot and Soot-like Materials in the Aqueous Environment: Mechanistic Considerations. - Environmental Science and Technology, 36, 3725-3734. Jonker, M. T. 0., A. J. C. S ink e, J. M. B r i 1 s, A. A. K o e 1 m a n s. 2003. Sorption of Polycyclic Aromatic Hydrocarbons to Oil Contaminated Sediment: Unresolved complex? - Environmental Science and Technology, 37, 5197-5203. J o n k e r, M. T. 0., A. B a r e n d reg t. 2006. Oil is a Sedimentary Supersorbent for Polychlorinated Biphenyls. - Environmental Science and Technology, 40, 3829-3835. Kha 1i1, M. F., U. Ghosh, J. P. K r e i t i n g e r. 2006. Role of Weathered Coal Tar Pitch in the Partitioning of Polycyclic Aromatic Hydrocarbons in Manufactured Gas Plant Site Sediments. - Environmental Science and Technology, 40, 56815687.

Ku pry i an ch y k, D., M. I. Ra k ow ska, J. T. C. Grote n huis, A. A. Koelmans. 2012. In Situ Sorption of Hydrophobic Organic Compounds to Sediment Amended with Activated Carbon. - Environmental Pollution, 161, 23-29. Lane, W. F., R. C. Loehr. 1992. Estimating the Equilibrium Aqueous Concentrations of Polynuclear Aromatic Hydrocarbons in Complex Mixtures. - Environmental Science and Technology, 26, 983-990. L e e, L. S., M. H a g w a 11, J. J. Delfino, S. C. Rao. 1992a. Equilibrium Partitioning of Polycyclic Aromatic Hydrocarbons from Coal-tar into Water. - Environmental Science and Technology, 26, 21042110. Lee, L. S., P. S. Rao, I. 0 k u d a. 1992b. Partitioning of Polycyclic Aromatic Hydrocarbons from Diesel Fuel into Water. - Environmental Science and Technology, 26, 2110-2115. Lion, L. W., T. B. Stauffer, W. G. MacIntyre. 1990. Sorption of Hydrophobic Compounds on Aquifer Materials: Analysis Methods and the Effect of Organic Carbon. Journal of Contaminant Hydrology, 5, 215-234. Liu, Z., J. Liu, Q. Zhu, W. Wu. 2012. The Weathering of Oil after the Deepwater Horizon Oil Spill: Insights from the Chemical Composition of the Oil from the Sea Surface, Salt Marshes and Sediments. Environmental Research Letters, 7, 035302 0 n w u rah, I. N. E., V. N. 0 g u g u a, N. B. 0 n y i k e, A. E. Ochonogor, 0. F. Otitoju. 2007. Crude Oil Spills in the Environment, Effects and Some Innovative Clean-up Biotechnologies. - International Journal of Environmental Research, 1, 307-320.

Journal of Balkan Ecology, vol. 19, No 1, 2016

79

P i g n a t e 11 o, J. J., B. X i n g. 1996. Mechanisms of Slow Sorption of Organic Chemicals to Natural Particles. - Environmental Science and Technology, 30, 1-11. Ran, Y., W. Hu an g, P. S. C. Rao, D. L i u, G. S hen g, J. M. Fu. 2002. The Roles of Condensed Organic Matter in the Nonlinear Sorption of Hydrophobic Organic Contaminants by Peat and sediments. Journal of Environmental Quality, 31, 1953-1962. Ran, Y., B. H. Xi a o, J.M. Fu, G.Y. Sheng. 2003. Sorption and Desorption Hysteresis of Organic Contaminants by Kerogen in a Sandy Aquifer Material. - Chemosphere, 50, 1365-1376. Reddy, C. M., T. I. E g 1 into n, A. H o u n s h e 1 l, H. K. W h i t e, L. Xu, R. B. Gaines, G. S. Fry singer. 2002. The West Falmouth Oil Spill After 30 years: The Persistence of Petroleum Hydrocarbons in Salt Marsh Sediments. - Environmental Science and Technology, 36, 4754-4760. Se mp 1 e, K. T., A. W. J. Morriss, G. I. Paton. 2003. Bioavailability of Hydrophobic Organic Contaminants in Soils: Fundamental Concepts and Techniques for Analysis. - European Journal of Soil Science, 54, 809-818. Site, A. D. 2001. Factors Affecting Sorption of Organic Compounds in Natural Sorbents, Water Systems and Sorption Coefficients for Selected Pollutants. A Review. - Journal of Physical and Chemical Reference Data, 30, 187-439. Sun, S., S. A. Boyd. 1991. Sorption of Polychlorobiphenyl (PCB) Congeners by Residual PCB-oil Phases in Soils. - Journal of Environmental Quality, 20, 557-561.

80

Sun, S., S. A.Boyd. 1993. Sorption of Nonionic Organic Compounds in Soil-water Systems Containing Petroleum Sulfonate-oil Surfactants. Environmental Science and Technology, 27, 1340-1346. Toride, N., F. Leij, M. van Gen u ch ten. 1995. The CXTFIT Code for Estimating Transport Parameters from Laboratory or Field Tracer Experiments. Version 2.0, Research Report No. 137. Riverside, CA: U.S. Salinity Laboratory, USDA, ARS. USPHS.1990. Toxicological Profile for Polycyclic Aromatic Hydrocarbons. U.S. Department of Health and Human Services, PHS, Agency for Toxic Substances and Disease Registry, p. 23 l. W a 1 t er, T., H. J. Eder er, C. Forst, L. Stieg 1 it z. 2000. Sorption of Selected Polycyclic Aromatic Hydrocarbons on Soils in Oilcontaminated Systems. - Chemosphere, 41, 387-397. W e b e r, W. J. Jr., W. Hu an g. 1996. A Distributed Reactivity Model for Sorption by Soils and Sediments. 4. Intraparticle Heterogeneity and Phase Distribution Relationships under Nonequilibrium Conditions. - Environmental Science and Technology, 30, 881-888. W e r n e r, D., U. G h o s h, R. G. Lu t h y. 2006. Modeling Polychlorinated Biphenyl Mass Transfer After Amendment of Contaminated Sediment with Activated Carbon. Environmental Science and Technology, 40, 4211-4218. Zhang, Y., F. Li, J. Wang. 2011. Determination of Retardation Effect of SOM on Aqueous Leaching of Polycyclic Aromatic Hydrocarbons Using Confocal Laser Scanning Microscope. - International Journal of Environmental Research, 5, 999-1008.

Scientific Research Papers: Remediation