Compound-specific radiocarbon analysis to evaluate the contribution of Peace River flooding to the PAH background in the Peace-Athabasca Delta.

(1)

Compound-specific Radiocarbon Analysis to Evaluate the Contribution of Peace

River Floodings to the PAH Background in the Peace-Athabasca Delta.

JOSUÉ JAUTZY,*

, 1

JASON M. E. AHAD,

2

ROLAND I. HALL,

3

JOHAN A. WIKLUND,

3

CHARLES GOBEIL,

1

AND MARTINE M. SAVARD

2

Map

AMS measurements

Δ

14

C

sample

=Δ

14

C

modern

f

modern

+Δ

14

C

fossil

f

fossil

Introduction

PAHs + apolar aromatic aliphatics

polar organic solvent

total organic extract silica

I II III

Methods

MARS & Soxlhet Extraction

Saponification & Liquid/Liquid Extraction

Silica-gel Cleanup

TLC

PAH Harvest (using PcGC)

Results & Discussion

WHERE?

WHY?

Oil sands located in a sensitive & complex environmental system.

Rapid growth of oil sands industry:

--> questionning the environmental impacts.

Focus on: Polycyclic Aromatic Hydrocarbons (PAHs). --> hazardous and carcinogenic organic compounds.

--> produced by: - incomplete combustion of biomass (modern or fossil). - maturation of kerogene towards fossil fuel.

- early stage diagenesis.

Establishing PAH background crucial in this region for source apportionment.

HOW?

Natural chronological record used:

--> 137_{Cs &}210_{Pb dated}_{lake sediment core.}

--> novel appproach based on 14_{C content of specific PAH}

alkyl source

discrimination.

--> able to estimate the relative contribution of fossil vs modern PAH.

fraction modern (f_modern)

Results & Discussion

PAH diagnostic ratios shows only a fossil fuel source in the entire sedimentary sequence --> not sensitive enough for this type of environment.

need to refine fingerprinting... Δ14_{C of specific PAHs:}

Sediment TOC : increasing trend for f_modern (from 20 to 36%)

--> flood frequency decrease associated with climate change.(1)

All PAH groups are < 12% modern, even though perylene and retene believed

to be related to modern biomass diagenesis or combustion.(3, 4)

Bacterial community selection --> metabolize fossil organic compound

Variation between top and bottom layer of the core within the error bars

However...

All PAHs except Alk-Naph/Fluo groups show an increasing trend for the modern fraction.

Mining related PAHs in this region -->particulate transport(5)--> unlikely to reach this remote area. Light PAHs more volatile--> could be transported further.

Take Home Conclusions

To be continued...

[PAH] :

> ISQGs for phenanthrene, benz[a]anthracene, dibenz[a, h]anthracene.

Alkylated PAH peak correlated with ice jam floods reported for this lake (C/N ratio & magnetic suceptibility profile).(1)

PAH_alkyl often related to fossil fuel, but can be produced by forest fire or

during diagenesis.(2, 3)

No correlation between [Ret] and [PAH_alkyl] profile.

--> [PAH_alkyl] unlikely related to forest fire events.

(1) PAH_alkyl naturally occuring in this lake from outcrops erosion/river

transport/ lake deposition during major flood events.

(2) More than 85% of the PAH_alkylare bitumen related.

(3) Less frequent flooding events in the last 10 years resulted in slightly less

input of bitumen related PAHs.

mass balance calculation:

Radiocarbon dead = Δ14_{C = -1000 ‰}

No large-scale bitumen surface mining

in the Peace River watershed.

Natural bitumen outcrops on river

banks. AB. SK. PAD15 Lake Athabasca Lake Claire Peace River -111.49° 58.95° N Sample site 10km References Acknowledgements Alk-Nap h/Fluo Alk-Phe

n/Anth_Per+Ret

Parent P AHs Alk-Fluo t/Pyr/Ch ry f modern (% ) 2 4 6 8 10 12 14 2000s_1960s

f_modern_{sediment TOC (%)}

0 10 20 30 40 Es ti m at ed C RS d at es (y r) 1960 1970 1980 1990 2000 2010 [∑PAH_alkyl] (ng.g-1 dry wt) 0 200 400 600 0 200 400 600 f_modern Ret+Per (%) 0 4 8 12 [Ret+Per] (ng.g-1 dry wt) 0 200 400 600 [∑PAH_parent] (ng.g-1 dry wt) 1997 1996 1994 1990 1979 1974 1972 Es ti m at ed flood d at es (y r)

(1) Compound specific Δ14_C _{on specific PAHs group from the}_{1970s layer.}

(2) Assess and model the input of bitumen derived PAHs into Athabasca Lake.

(3) Use of dual compound specific δ13_{C & δ}2_{H on light M.W. PAHs}_{for further}

source characterization.

Pre TLC

Post TLC

from GC Al₂O₃_cleanup C R O O R' + _H_O- R C O O -+ HO R'

&

ester ion hydroxyde ion carboxylate alcool

Hexane KOH/MeOH 365 nm 365 nm 365 nm 254 nm 254 nm sample PAH-standards

1

2

3

4

(1) Wolfe, B. B.; Hall, R. I.; Edwards, T. W. D.; Johnston, J. W., Environ. Rev. , 2012, 20, (3), 191-210.

(2) Gabos, S.; Ikonomou, M. G.; Schopflocher, D.; Fowler, B. R.; White, J.; Prepas, E.; Prince, D.; Chen, W., Chemosphere, 2001, 43 (4-7), 709-719. (3) Tan, Y. L.; Heit, M., Geochim. Cosmochim. Acta 1981, 45 (11), 2267-2279.

(4) Ramdahl, T., Nature 1983, 306 (5943), 580-582.

(5) Jautzy, J.; Ahad, J. M. E.; Gobeil, C.; Savard, M. M., Environ.Sci. Technol., 2013, 47, 6155-6163.

We wish to thank Pakdel, H. for the many useful discussions and technical advices in the lab. This work is supported by the CORES project, Natural Resources Canada.

Institut national de la recherche scientifique

Université du Québec

Eau, Terre et Environnement

Natural Resources

Canada Ressources naturellesCanada

1

2 3

Contact Information

*Tel: 418-654-4677 #4480; e-mail: josue.jautzy@ete.inrs.ca

Parent PAH

Alk-Naph/Fluo C1-Phen/Anth C2,C3-Phen/Anth Alk/Fluot/Pyr/Chry Perylene +Retene