PARTITIONING OF PYROGENIC AND PETROGENIC POLYCYCLIC AROMATIC

HYDROCARBONS IN NARRAGANSETT BAY SEDIMENTS. P.C. Hartmann and J.G. Quinn, University of Rhode Island, Narragansett, RI 02882. Hartmann@gsosun1.gso.uri.edu,

jgquinn@gsosun1.gso.uri.edu

Polycyclic aromatic hydrocarbons

(PAHs) are environmental contaminants that

are found in most estuarine sediments including those of Narragansett Bay, RI. There

are two primary sources of PAHs to estuaries:

pyrogenic PAHs derived from combustion

sources and petrogenic PAHs derived from

petroleum inputs . PAHs are an important

class of environmental contaminants to study

because some of these compounds are carcinogenic and/or mutagenic to mammals; in

addition, they have both acute toxicity and

sub-lethal effects on some aquatic organisms.

PAHs may also bioaccumulate in edible shellfish, which gives them a pathway to humans.

The EPA sediment quality criteria (SQC),

based on current models of the sediment bioavailability of PAHs, use a partitioning coefficient between PAHs in pore water and on

the total organic carbon in the sediments.

However, recent work suggests that this partitioning in marine sediments does not agree

with current models and that small soot particles in the sediment may be responsible for

some pyrogenically derived PAHs being less

available to partition into porewater than petrogenic PAHs [1]. This is important because

only the dissolved PAHs in porewater are

considered bioavailable; conversely, the soot

PAHs are strongly associated with solid

phases and may be less susceptible to degradation in the sediments, thereby lasting for

longer periods of time.

The objectives of our research project are

to assess the contribution of pyrogenic and

petrogenic PAHs to the sediments of Narragansett Bay and to evaluate the biogeochemical fate of these compounds with respect to

soot carbon and organic carbon. We looked at

45 individual PAH compounds, including alkyl homologs, in over 40 surface sediment

samples collected throughout Narragansett

Bay. Previous studies at other sites have

found a stronger relationship between selected PAHs and soot carbon than with organic carbon [2]. Our analysis did not find

this relationship for bulk PAHs or the PAHs

used in these other studies. We then turned to

principal component analysis (PCA) to try

and categorize sediment PAHs as pyrogenically or petrogenically dominated. Several

materials were included in the analysis to help

distinguish the sources of the PAHs. These

included urban dust (SRM1649a), marine

sediment (SRM1941a), #6 fuel oil, coal tar

(SRM1597), #2 fuel oil, used crankcase oil,

airplane soot and fire place soot. Pyrogenically dominated, sediments as determined

from PCA, showed a stronger correlation of

PAHs with soot carbon than organic carbon

supporting the hypothesis that many of these

PAHs are associated with soot particles. Petrogenically dominated sediments had a poor

correlation of PAHs with both soot and organic carbon possibly because they contain

weakly associated PAHs which are strongly

influenced by sediment diagenesis.

References: [1] McGroddy, S.E. and

J.W. Farrington, (1995) Environmental Science and Technology,. 29: p. 1542-1550.

[2] Gustafsson, O. and P.M. Gschwend,

(1997)in Molecular Markers in Environmental Geochemistry, R.P. Eganhouse, Editor., American Chemical Society: Washington

D.C. p. 365-380.

Ninth Annual V. M. Goldschmidt Conference 7252.pdf