Bioavailability and exposure assessment of petroluem hydrocarbons and trace elements in birds nesting near the North Platte River, Casper, Wyoming.
Kim Dickerson T. W. Custer C. M. Custer K. Allen
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The objectives of this study were to compare refinery-related petroleum hydrocarbon
concentrations in nestling tree swallows (Tachycineta bicolor) and nestling house wrens
(Troglodytes aedon) at sites along the North Platte River Casper, Wyoming in 1997 and 1998; and
to determine if contaminants were present in concentrations that could adversely affect the birds.
Because trace element concentrations, mixed function oxidase activity, and the variation in DNA are
often associated with petroleum hydrocarbon concentrations in birds, each was measured as
indicators of petroleum contamination. Sediment and aquatic invertebrates were also sampled for
characterizing a possible contaminant source to the birds. Sampling areas included sites upstream
(Game & Fish, Patterson-Zonta Park), adjacent to (Amoco Park, Texaco Refinery), and downstream
(EKW State Park) of the former Amoco and Texaco oil refineries. We also sampled one site
between the Amoco and Texaco Refineries (Crossroads Park). Additional samples were taken using
adult cliff swallows (Hirundo pyrrhonota) nesting under various bridges along the North Platte River
Several aliphatic hydrocarbons were detected in sediment, aquatic invertebrates, and
carcasses and gastrointestinal contents of house wren and tree swallow nestlings and adult barn and
cliff swallows from all sites but differences among sites were not significant. The low pristane to
n-C17 ratio in avian diet and tissues did not suggest chronic or acute exposure of birds to petroleum
at any of the locations. However, the high phytane to n-C18 ratios of the gastrointestinal contents
may indicate that some of the dietary items consumed by the birds were recently or chronically
exposed to petroleum products.
Most polycyclic aromatic hydrocarbons (PAHs) were not detected in aquatic insect larvae
but some were detected in sediments. Concentrations of total PAHs were detected in nestling
carcasses of tree swallows, house wrens, and a bank swallow. Differences in PAH concentrations
were not significant among sites for tree swallow nestlings but were for house wren nestlings. In
gastrointestinal contents of both tree swallow and house wren nestlings, PAH concentrations tended
to be higher at the Texaco Refinery site when compared to the Game & Fish site. Two hepatic
monooxygenase activities, benzyloxyresorufin-O-dealkylase (BROD) and ethoxyresorufin-Odealkylase
(EROD), in tree swallow livers also tended to be higher at the Texaco Refinery site than
at the Game & Fish sites and their induction may be related to PAH exposure. Because of the small
sample size, results of the flow cytometry analysis, which measured DNA content, were
inconclusive. Adult cliff swallow carcasses showed significant differences in total PAHs among
sites with the highest concentrations occurring at the Texaco Refinery site and the upstream
Patterson-Zonta Park site. PAHs were not detected in gastrointestinal contents of the cliff swallows.
The predominance of unsubstituted PAHs and the general lack of alkyl-PAHs in all samples suggests
that most of the PAHs were combustion-derived.
Most trace elements were not elevated in any of the samples. Chromium and selenium were
elevated in aquatic insect larvae but differences among sites were not significant. Chromium was
not detected in avian eggs or most nestling livers but was detected in nestling tree swallow and wren
carcasses and one adult barn swallow carcass. Mercury was detected in one bank swallow egg and
all tree swallow eggs. Mercury was significantly higher in tree swallow eggs collected at the EKW
State Park site when compared to the Game & Fish site. Mercury was detected in wren eggs from
EKW State Park but was not detected in eggs from the Game & Fish site or in two of the three eggs
USFWS - Region 6 - Environmental Contaminants Report
from the Texaco Refinery site. In tree swallow and wren nestling livers from EKW State Park and
the Texaco Refinery site, mercury concentrations were significantly higher than from the Game &
Fish site. Mercury was also detected in tree swallow nestling carcasses from both the Texaco
Refinery and EKW State Park but not from the Game & Fish site or in any of the house wrens.
Differences were not significant among sites and the source of the mercury is unknown.
Concentrations of mercury were detected in adult barn and cliff swallow livers and carcasses.
Selenium was detected in house wren and tree swallow eggs, livers, and nestling carcasses.
Selenium was also detected in adult barn and cliff swallow livers and carcasses. Differences were
not significant but selenium concentrations, probably the result of irrigation return flows, tended to
This study demonstrates that some refinery-related contaminants are bioavailable and birds
are being exposed. However, the data do not exhibit any pattern that can be linked to the refineries.
Our small sample size and limited statistical power do not allow us to determine if any of the
contaminants are adversely affecting the birds; and, the data collected on adult birds are inconclusive
because exposure to contaminants may have occurred outside the sampling area. Additionally, for
several contaminants detected, the upstream Game & Fish site appears to have concentrations similar
to the study sites. Finally, we were unable to determine the influence of yearly variation on the
results of the petroleum hydrocarbon or trace element analyses from 1997 and 1998; but, the 1997
data from the EKW State Park were not critical to the overall conclusions of the manuscript.
U.S. Fish and Wildlife Service
http://www.fws.gov/mountain-prairie/contaminants/papers/r6716c00.pdf, 423 KB
Mountain-Prairie Region Environmental Contaminants site