Evidence for the Natural Attenuation of PAH: Acenaphthene: the Last PAH Standing

PAH compounds are biodegradable, and several researchers have published the mechanisms, rates, and other details of PAH biodegradation in groundwater (Fraser, et al. 2008, Zam�rescu and Grathwohl, 2001). The researchers have shown that aerobic degradation removes most of the lighter, two-ring and three-ring PAH compounds. Heavier PAH compounds, especially carcinogenic PAH, are more generally resistaznt to biodegradation and are less mobile in the environment.

The pattern of groundwater PAH concentrations at the Reilly Site is similar to the biodegradation pattern described in the literature. This is illustrated by naphthalene and acenaphthene concentrations in groundwater samples. Near the source areas at the Reilly Site, naphthalene is the dominant PAH compound found in the groundwater and is the primary energy (food) source for biodegrading microorganisms. The mass of acenaphthene becomes greater than the mass of other PAH compounds downgradient from the source due to acenaphthene’s relative resistance to biodegradation compared to naphthalene, and its greater mobility compared to heavier PAH compounds.

Isoconcentration maps and other data presentations illustrate that acenaphthene represents 80% or more of the total PAH present in groundwater samples collected downgradient from the Reilly Site.

MGWA30 years

SummitEnvirosolutions

• Reilly operated a coal tar refinery and wood treating plant on 80 acres in St. Louis Park from 1917 to 1972.

• A multiaquifer well on site allowed PAH to migrate from shallow to deep aquifers.

• Taste and odor problems were encountered in 1932 when the City drilled its first well in the Prairie du Chien – Jordan Aquifer half a mile from the Reilly Site.

• PAH and coal-tar-like materials are present in soils and drift to the top of Platteville bedrock 65 feet deep.

• Clean soil was used to cover contamination, but a long-term source of PAH is present at the Site.

• Drinking water is treated using granular activated carbon.

Before

Site History

After

Coal Tar and PAH: Fun Facts to Know and Tell

• There are approximately 10 gallons of tar per ton of coal coked (or converted to gas at your neighborhood manufactured gas plant)

• Coal tar contains approximately 11% naphthalene

• Coal tar contains approximately 1.4% acenaphthene

• Typical coal tar is mostly pitch that contains high molecular weight PAH

• North Carolina “Tar Heels” were workers at underground wood coking operations for tar, turpentine, and charcoal production.

• There are over 100 different PAH compounds, 16 of which are priority pollutant PAH chosen to be representative of the entire group.

William M. Gregg, P.G. bgregg@summite.com Summit Envirosolutions, Inc., 1217 Bandana Blvd. North St. Paul, Minnesota 55108 www.summite.com

Drinking Water Criteria for PAH (PPB)

MDH HBV1

MDH HRL2

U.S. EPA, MCL3

Reilly Site Consent Decree4

Carcinogenic PAH (sum) 0.028Benzo(a)pyrene (BaP) 0.2BaP Equivalents (sum) 0.060

Other PAH (sum) 0.280Acenaphthene 400Anthracene 2,000Fluoranthene 300Fluorene 300Naphthalene 70Pyrene 200

1 Health Based Value for up to 25 carcinogenic PAH (potency related to BaP). This CPAH policy is currently under review at MDH.

2 Health Risk Limits for the only priority pollutant PAH listed by the MDH. 3 Maximum Contaminant Level for the only PAH listed by the U.S. EPA. 4 The Reilly Site Consent Decree lists 32 compounds, nine of which were considered carcinogenic.

Abstract

W20(4 ug/L)

W431(1 ug/L)W143

(7 ug/L)

W9(107.2 ug/L)

W439(852 ug/L)

W2(0.026 ug/L)

W437(2855 ug/L)

W421(1106 ug/L)

W420(2302 ug/L)

W27(2.275 ug/L)

W22(2.378 ug/L)

W18(5.125 ug/L)

W136(9.82 ug/L)

W10(0.044 ug/L)

P310(4.52 ug/L)

P309(17.6 ug/L)

P307(5.95 ug/L)

W438(0.297 ug/L)

W434(0.037 ug/L)

W427(0.086 ug/L)

W426(1.875 ug/L)

W15(0.0567 ug/L)

W131(1.453 ug/L)

W130(0.056 ug/L)

W121(0.053 ug/L)

W101(0.025 ug/L)

P312(1.336 ug/L)

P308(8.395 ug/L)

P109(0.023 ug/L)

W428(0.0913 ug/L)

Sources: Esri, DeLorme, NAVTEQ, USGS, Intermap, iPC, NRCAN, Esri Japan,METI, Esri China (Hong Kong), Esri (Thailand), TomTom, 2012

0 700350Feet± 1 inch = 700 feet

Drift Aquifer Naphthalene Distribution

Near the source areas at the Reilly Site, naphthalene is the dominant PAH compound found in the groundwater

• Acenaphthene is the dominant PAH compound found in downgradient groundwater

• In an idealized biodegradation setting, as distance from the source increases, all PAH concentrations decrease in downgradient areas due to various natural attenuation phenomena and naphthalene is removed below detection limits.

• The pattern of groundwater PAH concentrations at the Reilly Site is similar to the biodegradation pattern described in the literature

• Biological degradation removed naphthalene and a portion of the other more easily degraded PAH compounds in the source area. Higher molecular weight PAH that were not biodegradable were sorbed to the soils and aquifer matrix, especially the peat and organic soils in the bog area

• Acenaphthene and other PAH are attenuated by sorption and dispersion in the downgradient areas where biodegradation is largely absent

References:Fraser, M., Barker, J.F., Butler, B., Blaine, F., Joseph, S., Cooke, C., 2008. “Natural attenuation of a plume from an emplaced coal tar creosote source over 14 years”. Journal of Contaminant Hydrology 100, pp101-115, June 1, 2008.

Gregg, W., 2007. “The Role of Multiaquifer Wells in Coal Tar Migration”. Presentation at MGWA Spring Conference. April 19, 2007.

Zam�rescu, D., Grathwohl, P., 2001. “Occurrence and attenuation of speci�c organic compounds in the groundwater plume at a former gasworks site”. Journal of Contaminant Hydrology 53, pp 407-427, May 30,

Prairie du Chien – Jordan Aquifer Acenaphthene Distribution

Summary & Conclusion

W9(5.94ug/L)

W434(2.4ug/L)

W27(46.2ug/L)

P312(4.9ug/L)

W422(13.2ug/L)

W22(5.458ug/L)

W18(3.925ug/L)

W15(0.021ug/L)

W131(0.54ug/L)

W101(0.36ug/L)

P310(5.82ug/L)

P308(3.45ug/L)

P307(26.8ug/L)

W438(0.042ug/L)

W437(145.5ug/L)

W431(0.047ug/L)W143

(0.214ug/L)

W120(0.366ug/L)

P309(15.65ug/L)

W433(0.0514ug/L)

W428(0.0085ug/L)

W121(0.0096ug/L)

Sources: Esri, DeLorme, NAVTEQ, USGS, Intermap, iPC, NRCAN, Esri Japan,METI, Esri China (Hong Kong), Esri (Thailand), TomTom, 2012

0 700350Feet± 1 inch = 700 feet

Drift Aquifer Acenaphthene Distribution

W48(0.1ug/L)

W23(3.6ug/L)

SLP6(0.1ug/L)

H6(0.073ug/L)

E13(0.135ug/L)

W29(0.0119ug/L)

SLP15(0.13ug/L)

E7(0.00995ug/L)

E2(0.00816ug/L)

E15(0.0054ug/L)

W401(0.0243ug/L)

W119(0.0727ug/L)

SLP4(0.0555ug/L)

SLP10(0.712ug/L)

W402(0.00652ug/L)

MTK6(0.00053ug/L)

SLP14(0.00408ug/L)

Sources: Esri, DeLorme, NAVTEQ, USGS, Intermap, iPC, NRCAN, Esri Japan,METI, Esri China (Hong Kong), Esri (Thailand), TomTom, 2012

0 3,5001,750Feet± 1 inch = 3,500 feet

Prairie du Chien – Jordan Aquifer Naphthalene Distribution

W23(2.82ug/L)

SLP6(0.01ug/L)

E7(0.0095ug/L)

E3(0.0119ug/L)

E13(0.012ug/L)

W48(0.0078ug/L)

W402(0.017ug/L)

W29(0.0155ug/L)

H6(0.00432ug/L)

E2(0.00433ug/L)

W403(0.0168ug/L)

W401(0.0032ug/L)

E15(0.00315ug/L)

W406(0.00251ug/L)

W119(0.00618ug/L)

SLP4(0.00398ug/L)

MTK6(0.00428ug/L)

SLP16(0.00377ug/L)

SLP14(0.00408ug/L)

SLP10(0.00808ug/L)

Sources: Esri, DeLorme, NAVTEQ, USGS, Intermap, iPC, NRCAN, Esri Japan,METI, Esri China (Hong Kong), Esri (Thailand), TomTom, 2012

0 3,5001,750Feet± 1 inch = 3,500 feet

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

2000 2005 2010

Well W434

PA

H(R

atio)_

31__A

cenaphth

ene

(ug/L

)

6/27/1988 ~ 12/12/2012

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

1995 2000 2005 2010

Well E13

Acenaphth

ene

Per

cent

of T

PA

H

6/27/1988 ~ 12/12/2012

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1990 2000 2010

Reilly Site, St. Louis Park, MN

Naphth

ale

ne C

oncentr

ation

(ug/L

)N

aphth

ale

ne

Perc

ent

of

TP

AH

6/27/1988 ~ 12/12/2012

Naphthalene | W420

Naphthalene | W421

PAH(Ratio)_31__Naphthalene | W420

PAH(Ratio)_31__Naphthalene | W421

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1990 2000 2010

Well W422

PA

H(R

atio)_

31__A

cenaphth

ene

(ug/L

)

6/27/1988 ~ 12/12/2012

Well W422 Acenaphthene Percentage

Well E13 Acenaphthene Percentage

Source Area Naphthalene History

PAH Physical Properties

Well W434 Acenaphthene Percentage