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Environ Sci Technol 37, 2003, 2847 2854 .pdf

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Rapidly Increasing Polybrominated
Diphenyl Ether Concentrations in the
Columbia River System from 1992
to 2000
Department of Chemistry, Box 3065, University of Victoria,
Victoria, British Columbia, Canada, V8W 3V6
Contaminants Science Section, Institute of Ocean Sciences,
Fisheries and Oceans Canada, 9860 West Saanich Road,
Sidney, British Columbia, Canada, V8L 4B2
Habitat and Enhancement Branch, Fisheries and
Oceans Canada, Suite 200, 400 Burrard Street,
Vancouver, British Columbia, Canada V6C 3S4

Concentrations and congener patterns of 32 individual
PBDE congeners from mono- through hexa-brominated
were investigated in two fish species occupying similar
habitatssbut having different diets and trophic levelss
and surficial sediments from several locations on the major
river system of western North America, the Columbia
River, in southeastern British Columbia, Canada. Total PBDE
concentrations have increased by up to 12-fold over the
period from 1992 to 2000 in mountain whitefish from the
Columbia River, with a doubling period of 1.6 years. The
rate at which PBDE concentrations are increasing in whitefish
is greater than has been previously reported worldwide.
At the current rate of increase, ΣPBDE will surpass those
of ΣPCB by 2003 to become the most prevalent organohalogen contaminant in this region. ΣPBDE in whitefish from
the mainstem of the Columbia River range up to 72 ng/g
wet weight, concentrations that are 20-50-fold higher than
in a nearby pristine watershed affected only by atmospheric
contaminant transport. Conversely, ΣPBDE in largescale
suckers were approximately an order of magnitude lower
than in whitefish, demonstrating the influence of biomagnification and feeding habits. Congener patterns in whitefish
from the Columbia River directly correlated with the two
major commercial penta-BDE mixtures in use and represent
the first time free-swimming aquatic biota such as fish
have been found to contain PBDE congener patterns so
similar to commercial mixtures. PBDE concentrations
in sediments were not linked to a variety of investigated
point sources but were instead inversely correlated with the
ratio of organic carbon:organic nitrogen in surficial
sediments with a pattern suggesting the dominant influence
of septic field inputs from the primarily rural population.

* Corresponding author phone: (250)363-6804; fax: (250)363-6807;
e-mail: IkonomouM@pac.dfo-mpo.gc.ca.
10.1021/es0340073 CCC: $25.00
Published on Web 05/17/2003

 2003 American Chemical Society

The Columbia River is the fifth largest river system in North
America ranked by flow (6650 m3/s), draining a total basin
area of 673 000 km2 in the northwestern United States and
Canada before discharging into the northeast Pacific Ocean
at the Washington State/Oregon border, some 1900 km from
its source in two mountain lakes of the Selkirk Mountain
range in British Columbia, Canada. Human settlement along
the river has been present for over 10 000 years, but the 20th
century saw large scale engineering projects (mostly hydroelectric developments) rapidly change the river’s hydrology.
Anthropogenic activities resulting from this development
have had numerous effects on the physical, chemical, and
biological characteristics of the region, especially declining
salmonid fish populations over the past century (1). At
present, more than 400 dams exist on the Columbia River
system, making it the most hydroelectrically developed river
system in the world (2). However, while much is known
regarding the effects of human development on the physical
and biological state of the Columbia River, relatively little is
known regarding organic contaminants in this system,
especially in the Canadian portion.
Among the organic contaminants of current interest and
concern, recent evidence has confirmed that the brominated
flame retardants, polybrominated diphenyl ethers (PBDEs),
are ubiquitous contaminants present in all environmental
compartments at concentrations up to the parts-per-million
range (3, 4). In industrialized and pristine regions of North
America, PBDE concentrations are increasing rapidly (3, 5)
at rates which may be more rapid than was ever observed
for PCBs (6) and in contrast to declining concentrations of
PCBs and PCDD/Fs in the present study area (7). Indeed, the
1999 worldwide production volume of PBDEs (sum of the
commercial penta-, octa-, and deca-BDE mixtures) at 67 000
tonnes is near the PCB production maximum of 100 000
tonnes in 1970 (8). At this rate of PBDE production, which
does not appear to be either stabilizing or declining (3), only
14 years would be required to surpass the estimated
worldwide PCB production of ∼1 000 000 tonnes which took
place over the five decades from the 1930s until the late 1970s
Unfortunately, there are few temporal studies by which
to rigorously examine how PBDE concentrations have
changed in different regions during the latter 20th and early
21st centuries. Furthermore, little is known of PBDE concentrations and congener patterns in the major North
American rivers (i.e. Mississippi-Missouri-Red Rock, St.
Lawrence, Mackenzie-Peace, Yukon, Columbia). In the
Columbia River, the large number of hydroelectric facilities
have, in effect, disconnected various units of the river from
each other, thereby preventing unrestricted movement of
fish throughout the ecosystem. This disconnection is thought
to have greatly constrained the access of anadromous fish
to upstream spawning sites, possibly helping to explain large
declines in regional fisheries stocks since the early 1900s
(10-12). In addition, dams largely prevent the downstream
movement of suspended and bedload sediments, thereby
encouraging scouring of the river bed downstream. These
sediments are known to be important vectors for hydrophobic
contaminants such as PBDEs, which would generally prefer
to reside on organic substrates than be dissolved in the water
column (13-16). This compartmentalization of fish populations and sediments makes the Columbia River system a
particularly intriguing one in which to examine PBDE



FIGURE 1. Map showing topographic features of the study region discussed in the text and sampling sites for mountain whitefish and
surficial sediments in the Columbia and Kootenay River systems in southeastern British Columbia, Canada. Sample numbers correspond
to data provided for individual fish and sediments in the Supporting Information.
concentrations and patterns. In addition, increasing concentrations of potentially toxic organic contaminants such
as PBDEs may be an additional stressor (17-19), that when
combined with other human influences such as hydroelectric
development, may further hinder recovery of some fish
populations in the Columbia River.
In the study region of the Columbia River and a major
tributary, the Kootenay River, in southeastern British Columbia, Canada (Figure 1), thalwegs are generally shallow
(2-12 m) during normal discharge events and river velocities
are moderate to high (75 to >150 cm/s), favoring a riverbed
composed of medium to large cobbles and small boulders
and/or parent bedrock material with a limited littoral area
(20, 21). Smaller numbers of depositional environments are
found where gravels, cobbles, sand, and silt materials collect
(20, 22). The Kootenay River joins the Columbia River ∼10
km downstream from Hugh Keenleyside Dam and 46 km
upstream from the Canada-United States border, after which
the Columbia River continues its course 1100 km through
the United States before discharging into the Pacific Ocean.
The average flow of the Columbia River at the Canada-United
States border is ∼2630 m3/s, of which 1150 m3/s is from the
Arrow Lakes reservoir system controlled by the Hugh
Keenleyside Dam, 790 m3/s from the Kootenay River system,
and 690 m3/s from the Pend d’Oreille River which enters the
Columbia River 3 km before the international border (22).
In the study region, 25 species of fish have been recorded
(22), of which mountain whitefish and largescale suckers are
considered resident (21) and thus good indicators of local
contaminant inputs and sources. Of these two species,
mountain whitefish are the most abundant sportfish in the
Columbia and lower Kootenay Rivers with a population that
has remained relatively stable at 35 000-40 000 individuals
since the early 1980s (20, 22). Whitefish tend to occupy high



velocity habitats with cobble or boulder substrates and riffle
and run areas adjacent to cobble and boulder deposition
areas. Their diet is mainly bottom feeding of aquatic insect
larvae (e.g. caddisflies), small mollusks, and occasionally fish
(23). Most adult whitefish in this area occupy deepwater
habitats in the day and relocate to shallow-water habitats for
feeding at night (24). Juveniles typically reside in shallow
nearshore habitats for rearing, as these areas provide the
greatest quantity of food and cover (20, 21). Largescale
suckers, in comparison, use a wider variety of habitats than
whitefish with adults residing in both deepwater and
nearshore habitats and juveniles occupying shallow stream
margins. The diet of immature suckers is mostly planktonic,
consisting mainly of water fleas and copepods, and shifts to
bottom feeding of invertebrates for adult individuals (23).
Largescale suckers generally spawn in May and June, while
whitefish spawn during the period from November through
February (21). The population of largescale suckers is
estimated to range between 21 000-57 000 and is also
thought to be relatively stable (22). Together with surficial
sediment samples, the resident nature of these two fish
species and their different feeding habits offer a means of
investigating the concentrations and patterns of PBDEs in
this section of the Columbia River system.
To facilitate an understanding of the temporal and spatial
trends of PBDEs in a major North American river, we
determined the concentrations of 32 individual PBDE
congeners from mono- through hexabrominated in mountain
whitefish, largescale suckers, and surficial sediments from
several locations on the Columbia and Kootenay River
systems in southeastern British Columbia, Canada. Whitefish
samples obtained over the period from 1992 to 2000 shed
insights into how PBDE concentrations have changed in this
aquatic system over the past decade. Largescale sucker

samples were taken to help determine how PBDE concentrations and congener patterns differ for fish occupying the
same region but with different feeding habits. Surficial
sediments were also collected to assist in identifying potential
PBDE sources and to examine whether congener patterns
and concentrations differed between sediments and fish.
Together, these samples form one of the first comprehensive
data sets on PBDE concentrations and congener patterns in
a major North American river.

Experimental Section
Sample Collection and Preparation. Sampling for mountain
whitefish (Prosopium williamsoni) in the Columbia and
Kootenay River systems took place during the first 2 weeks
of July in 1992, 1994/1995, and 2000. Whitefish samples from
the Slocan River reference site (WF39-41) were obtained by
angling methods in an attempt to avoid tissue damage
induced by electroshocking. Angling methods were unsuccessful at the Genelle (WF15-33) and Beaver Creek (WF1-14)
sites on the Columbia River, and whitefish were collected
using electroshocking. Whitefish samples collected in
Kootenay Lake (WF34-38) in early July of 1998 near the
outflow to the Kootenay River as well as largescale suckers
(Catostomus macrocheilus; LS1-6) collected in early July of
2000 downstream of the city of Nelson on the Kootenay River
were also obtained by electroshocking. Details on the
methods of electroshocking and age determination are
provided elsewhere (25, 26). Sampling sites are shown in
Figure 1; details regarding each location are discussed
throughout the manuscript.
Surficial sediments were collected from 11 depositional
locations (S1-11) on the Columbia and Kootenay River
systems on August 18 and 19, 2001. Samples were collected
from the top 2-3 cm of fine-grained silt, clay, and organic
materials within 2 m of the shoreline. All materials for
collecting sediments were stainless steel or amber glass and
were washed with successive rinses of tap water, distilled
water, 95% ethanol, and acetone in the field prior to collection.
Sediments collected at each site were placed in solvent rinsed
amber glass jars and stored on dry ice during sampling and
transport and at -20 °C in the laboratory prior to processing
and analysis (<30 d to processing from sampling date).
Sample Extraction, Cleanup, and Analysis. Fish muscle
tissue was thawed, dissected, and homogenized prior to
extraction. Skin and bones were removed during dissection,
and the tissue was homogenized with a commercial meat
grinder. Following homogenization, samples were subsampled for contaminant analysis and moisture and lipid
Sediment samples were thawed to room temperature, and
approximately 10 g (wet) was weighed out for extraction.
Additional samples (∼2 g) were also taken for moisture
content, organic carbon, and organic nitrogen analysis.
Moisture content was determined by drying the sample in
a 105 °C vented oven for 48 h and weighing the sample before
and after drying. Organic carbon and organic nitrogen content
were determined using a Leeman CE440 elemental analyzer.
Approximately 10 g of sample (tissue or sediment) was
spiked with a suite of 13C-labeled PBDE, PCDD, PCDF, and
PCB procedural internal standards (Cambridge Isotope
Laboratories; Andover, MA) and processed using procedures
described in detail previously (3, 4). Tissue samples were
ground with sodium sulfate, transferred quantitatively to an
extraction column with, and extracted with, CH2Cl2/hexane
(1:1 v/v). Sediment samples were Soxhlet extracted with
toluene/acetone (80:20 v/v), and the extract was acid-base
washed prior to other cleanup. Sample cleanup took place
in three stages. In the first step, aliquots were passed through
a multilayer silica column packed with successive layers of
silica gel (basic, neutral, acidic, neutral) and eluted with CH2-

FIGURE 2. Concentrations of total PBDEs and the five major
congeners in mountain whitefish muscle from the Columbia River,
British Columbia, Canada. Labels (e.g. Genelle 2000 (n ) 11)) indicate
sampling location, year, and sample size, respectively. Values are
in ng/g wet weight and are age normalized using ANCOVA.
Cl2/hexane (1:1 v/v). The second cleanup step was with a
neutral activated-alumina column capped with anhydrous
sodium sulfate. The column was washed with hexane followed
by CH2Cl2/hexane (1:1 v/v) elution to recover the analytes
of interest. Eluants from the alumina column were concentrated to less than 10 µL and spiked with 1 ng of a 13C-3,3′,4,4′tetrabromodiphenyl ether instrumental internal standard (10
µL of a 100 pg/µL stock solution) prior to congener-specific
PBDE analyses by high-resolution gas chromatography/highresolution mass spectrometry (HRGC-HRMS).
Where PCB and PCDD/F analyses were also required from
the same sample, the eluant concentrate collected from the
alumina column was fractionated with an automated highperformance liquid chromatography (HPLC) system utilizing
a carbon fiber column. The four fractions (fraction #1 ) dithrough tetra-ortho PCBs; #2 ) mono-ortho PCBs; #3-4 )
nonortho PCBs; #4 ) PCDD/Fs; #1-4 ) PBDEs) collected
from this system were spiked with the corresponding
instrumental internal standard(s) and analyzed for the desired
target analytes (i.e. PCBs and PCDD/Fs) by HRGC-HRMS.
All HRGC-HRMS analyses were performed with the HRMS
operating in the positive EI ionization mode at 10 000
resolving power and acquiring data under SIM conditions.
The sample workup and the instrumental analyses conditions
(for all analyses; PBDEs, PCBs, and PCDD/Fs) and the criteria
used for identification and quantitation are described in detail
in our previous works (3, 4).
Data Analysis. Data compilation and graphing were
performed using Microsoft Excel XP (Redmond, WA). Differences between sampling groups were investigated using
single factor ANOVA in SPSS v.10.0 (Chicago, IL). As has been
observed elsewhere (27-29), PBDE concentrations were
positively correlated with fish age and were thus agenormalized using ANCOVA for those sample groups having
different mean ages and age distributions. Cluster analysis
(with the standardized Euclidean measure and Ward clustering method) was performed using KyPlot v.2.0 b.9 (Tokyo,
JPN). Because of the difficulty in representing multivariate
data sets, such as multiple congener contributions to total
PBDEs, on conventional two- and three-dimensional graphs
(e.g. scatter and bar graphs), cluster analysis (CA) was
developed as a means of showing similarities and differences
of multivariate data sets in a two-dimensional form. A brief
description of interpreting the CA plot shown in Figure 4 is
presented below.

Results and Discussion
Increasing PBDE Concentrations in Mountain Whitefish.
Concentrations and congener patterns of the brominated



FIGURE 3. Relationship between total PBDE concentrations in
Columbia River surficial sediments and the ratio of organic carbon
to organic nitrogen content.
flame retardants, polybrominated diphenyl ethers (PBDEs),
were determined in 41 mountain whitefish, 6 largescale
suckers, and 11 surficial sediment samples from the Columbia
and Kootenay River systems in southeastern British Columbia, Canada (Figure 1). Total PBDE concentrations (ΣPBDE;
sum of the 13 major congeners shown in Figure 4) in
mountain whitefish obtained near Genelle and Beaver Creek

on the mainstem of the Columbia River have increased by
factors of 11.8 and 6.5, respectively, over the period from
1992 to 2000 (Figure 2). At Genelle (population 800), located
approximately 13 km downstream from the city of Castlegar
(population 7400) and the Celgar bleached softwood kraft
pulp mill, mean ΣPBDE concentrations increased 3.1-fold
from 6.1(4.6 ng/g wet weight (ww) to 19.1 ( 5.3 ng/g ww
between 1992 and 1994/1995 (p < 0.011). The period from
1994/95 to 2000 saw a further increase by a factor of 3.8 to
a mean ΣPBDE concentration of 71.8 ( 19.0 ng/g (p <
3.1 × 10-5). The total increase over the period from 1992 to
2000 at Genelle is over an order of magnitude (11.8-fold;
p < 1.2 × 10-5). At the confluence of Beaver Creek and the
Columbia River, approximately 25 km downstream from the
community of Genelle and 9 km downstream from the city
of Trail (population 35 300) and the Teck Cominco zinc and
lead smelting operation, ΣPBDE concentrations increased
by a factor of 6.5 from 4.5 ( 1.8 ng/g ww in 1992 to 29.2 (
15.4 ng/g ww in 2000 (p < 0.005). In the region where the
west arm of Kootenay Lake (regional pop. ∼34 000 along
lakeshore) discharges into the Kootenay River near the city
of Nelson (population 9700) and 30 km upstream from the
confluence of the Columbia and Kootenay Rivers, ΣPBDE
concentrations in mountain whitefish from 1998 were

FIGURE 4. Cluster analysis plot of PBDE congener patterns in Columbia River mountain whitefish muscle from Genelle (WF-G) and Beaver
Creek (WF-B) collected in 2000, male ringed seal blubber in individuals aged 0-15 years from the Canadian Arctic collected in 2000 (RS-A),
Dungeness crab hepatopancreas from the Strait of Georgia off the southwestern coast of British Columbia collected in 1996 (DC-SG), harbor
porpoise blubber from the Strait of Georgia collected in 1996 (HP-SG), largescale sucker muscle from near Taghum in the Kootenay River
collected in 2000 (LS-T), and two major penta-BDE mixtures (Bromkal 70-5DE and Great Lakes Chemicals DE-71).



significantly lower (14.3 ( 10.4 ng/g) than observed at Beaver
Creek or Genelle in 2000 (p < 0.012 and p < 1.3 × 10-5). The
increase in ΣPBDE concentrations at Genelle is unprecedented in the published literature, with a doubling period
of 1.6 years between 1995 and 2000.
On the Slocan River reference site, in an unpopulated
pristine area not directly impacted by anthropogenic activities, ΣPBDE concentrations in 1996 were 0.9(0.2 ng/g ww.
These concentrations at Slocan are ∼20-50 times lower than
those at Genelle in 1994/1995 and Beaver Creek in 1996,
respectively (single data point for 1996 at Beaver Creek
provided in the Supporting Information). The significantly
lower ΣPBDE concentrations at Slocan compared to Genelle
and Beaver Creek suggests long-range atmospheric deposition is not likely the major source of PBDEs to this region,
otherwise we would not expect to see such distinct differences
depending on locale. However, the Columbia River at Genelle
and Beaver drains a much larger area (∼90 000 km2) (21)
than the Slocan River (∼3300 km2) (30), which may allow
in-stream concentration of high levels of atmospherically
deposited PBDEs. On the other hand, the ratio of drainage
areas between the Columbia River and the Slocan River (∼27)
is similar to the ratio of mean flows between these two rivers
(2010 and 88 m3/s, respectively; ratio ≈ 23) (21, 30), suggesting
that a differential concentration of atmospherically deposited
PBDEs between the two watersheds is likely minimal and
insufficient to explain the large ΣPBDE concentration differences. Thus, there appears to be a regional source of PBDEs
discharging directly into this part of the Columbia River
system. Furthermore, the lower ΣPBDE concentrations in
whitefish from Kootenay Lake (volume ≈ 36.7 km3) (31)
compared to the Columbia River are consistent with dilution
of influent PBDE sources to the lake, such that there is a
reduced fish exposure to PBDEs via the water column in
Kootenay Lake versus the Columbia River between Castlegar
and the United States border. Knowledge regarding the
population distribution, and the suspected domestic wastewater sources of PBDEs in this area (discussed below),
appears to support this hypothesis and help understand the
spatial distribution of PBDE burdens in whitefish from this
PBDE concentrations were also determined in six largescale suckers sampled in 2000 downstream of the city of
Nelson on the Kootenay River at Taghum. These fish had
lower PBDE burdens (5.0 ( 1.9 ng/g ww) than whitefish from
either the upstream Kootenay Lake (p < 0.08) site or the
Genelle (p < 1.3 × 10-5) and Beaver Creek (p < 0.013) sites
on the Columbia River. The lower concentrations found in
suckers versus whitefish, especially compared to Kootenay
Lake whitefish (likely exposed to more dilute PBDE concentrations), suggests that whitefish may be able to accumulate PBDEs to a greater extent than suckers. Similar
findings have been reported between suckers and mountain
whitefish and rainbow trout from pristine and populated
watersheds in nearby Washington State (32). The differing
PBDE concentrations between whitefish and suckers occupying similar habitats may result from their relative trophic
status. Whitefish are insectivores and piscivores versus the
benthic omnivorous behavior of suckers (32), and thus the
higher PBDE burdens in whitefish may result from an
additional bioaccumulatory step up the local food chain (32,
33). Differential metabolic capacities of the two fish species
may also help explain the differences, although only qualitative data are available to support this hypothesis (32).
Domestic Wastewater as the Major Sources of PBDEs in
this Region of the Columbia River. The rapidly increasing
PBDE concentrations in whitefish from the Columbia River
in southeastern British Columbia, Canada, warranted further
investigation into potential sources of these compounds to
aquatic systems. We have recently shown that a congener-

TABLE 1. Concentrations of Total PBDEs, PCBs, and PCDD/Fs
in Columbia River Whitefish from 1992 to 2000a

Beaver Creek 1992
Genelle 1992
Genelle 1994/1995

(ng/g ww)

(ng/g ww)

(pg/g ww)

4.5 ( 1.8
6.1 ( 4.6
19.1 ( 5.3

70.3 ( 41.4
89.9 ( 45.6
86.2 ( 62.6

73.6 ( 32.3
43.3 ( 27.9
25.6 ( 20.1

Error bars are 95% confidence limits about the mean.

specific reconstruction procedure using semipermeable
membrane devices (SPMDs) deployed in the heavily urbanized and industrialized lower Fraser River (population
2 000 000) suggested that relatively unaltered present-day
commercial penta- and octa-BDE formulations are the likely
source of PBDEs to this aquatic system (34). However, our
analysis did not investigate where these PBDEs might be
coming from. To better understand potential sources of
PBDEs in this region of the Columbia River system, 11 surficial
sediment samples (top 1-2 cm of fine organic sediment)
were taken from a range of locations throughout the study
region (see Figure 1 for locations and Supporting Information
Table 1 for concentrations). PBDE concentrations in these
surficial sediments ranged from 3.8 to 90.9 ng ΣPBDE
normalized to organic carbon content (ng ΣPBDE/g OC),
with no prima facie spatial pattern. Other than the same
three major congeners (BDEs 47, 99, and 100), congener
patterns differed between sediments and whitefish from the
same region. BDE47 was the major congener in surficial
sediments (46-63% of ΣPBDE), with lesser quantities of BDEs
99 (23-39%) and 100 (6-8%). Interestingly, concentrations
of the two major hexa-BDE congeners usually found in the
environment and technical mixtures, BDEs 153 and 154, were
below detection limits (0.1-0.5 pg/g) in all sediment samples.
That BDE99 contributions were greater in whitefish than
sediments is unique because previous studies have suggested
that BDE99 is significantly less amenable to biological uptake
than BDE47. To our knowledge, no previous studies have
shown free-swimming aquatic biota (from plankton to fish
to marine mammals) with BDE99 as the major congener and
a percent contribution similar to major penta-BDE commercial mixtures (27, 28, 32, 35-41). Thus, sediments are
usually enriched in BDE99 contribution compared to aquatic
biota, in contrast to our findings here.
The difference in congener patterns between sediments
and whitefish in the Columbia River system, in a manner
contrary to what is expected and has been reported elsewhere,
suggests one or more of the following processes may be
operating. Whitefish could have a unique uptake, metabolism,
storage, and excretion (UMSE) mechanism distinct from other
fish species studied to date (e.g. trout, pike (42-44)), resulting
in preferential accumulation of BDE99 over BDE47. Such a
mechanism may be reasonably postulated provided there
are no size-limited diffusion restrictions on BDE99 accumulation in whitefish, as the log Kow for BDE99 (∼6.5) is
slightly greater than that for BDE47 (∼6.1) (13), thereby
favoring bioaccumulation of BDE99. In addition, the PBDE
sources that whitefish receive much of their burdens from
could be different from the sources to the surficial sediments.
However, previous work has shown the whitefish to spend
much of their spawning, rearing, and feeding time in the
same regions from where sediment samples were collected
(22, 45). Indeed, immediately downstream (∼1-2 km) of
Genelle is a known spawning area and high use rearing habitat
for whitefish (22). Additional spawning areas and high to
moderate use rearing areas are also located adjacent to the
remaining sediment samples. Thus, it seems unlikely that
sediments and whitefish would be exposed to different PBDE
sources when residing in the same area.



Another hypothesis is that congener-specific partitioning
occurs among sediment grains of different sizes and that the
smaller grains are enriched in the contribution of higher
brominated congeners such as BDEs 99 and 100. This
postulate is consistent with the results of previous studies
looking into the congener specific partitioning of halogenated
contaminants onto sediments of differing sizes (14, 16, 4652). Because of the generally greater organic content and
surface area of smaller sediment fractions (i.e. colloidal and
particulate organic carbon, organic detritus, silts and clays),
heavier congeners have a greater affinity for these sediments
than smaller congeners based on equilibrium partitioning
theory. Wide flow variations occur in this region of the
Columbia River because of the large spring/early summer
freshet in May-late June (22) followed by the dry season
from July-April (range of flows from 172 to 9340 m3/s at the
hydrographic station at Birchbank (sample site S8) (53). In
combination with seasonal, weekly, and daily discharge
variations from two dams (Hugh Keenleyside Dam and
Brilliant Dam) immediately upstream of the study region on
the Columbia and Kootenay Rivers, respectively (Figure 1),
large flows remove much of the bedload smaller than sand
and gravels each year at freshet time and continuously
throughout the seasons (20, 22). In addition, the Columbia
River downstream of Castlegar is generally characterized as
having moderate to high water velocities with few depositional regions (20, 22) and increased bed scour because of
the upstream dams which remove much of the sediment
load arriving from the headwaters (54), thereby favoring little
year-to-year accumulation of fine sediments. Overall, because
the UMSE processes for PBDEs in whitefish are at present
unknown, and because it is unlikely fish and sediments
residing in the same region in the shallow (<12 m as provided
in refs 20 and 22) waters of the Columbia and Kootenay rivers
would be exposed to different PBDE sources, the differing
congener patterns between whitefish and sediments in the
these aquatic systems likely results from the preferential
transport of higher brominated congeners out of the local
system due to the continual erosion of fine sediments. In
addition, whitefish are known to feed heavily on caddisflies
in streams. Caddisflies, in both the larval and adult stages,
tend to produce webs to capture fine suspended material as
a food source. These feeding habits by both whitefish and
their caddis fly prey may help explain both the higher PBDE
concentrations and predominance of higher brominated
congeners we observe in whitefish, as fine suspended
sediments tend to concentrate contaminants, especially the
more hydrophobic congeners (i.e. BDE99 over BDE47) as
discussed above. The intake of fine, suspended particulates
by whitefish in this aquatic system may be a major pathway
of exposure to higher brominated congeners not generally
reported to date in other aquatic systems (e.g. lakes and
marine environments) where PBDE concentrations and
patterns have less direct dietary influence from sediment
associated contaminants than in the present study.
At a first approximation, no obvious point sources of
PBDEs (e.g. furniture and textiles production (28) or PBDE
manufacturing plants) were evident along the Columbia River
downstream from Castlegar to the Canada-United States
border. Sampling sites were chosen to surround the following
potential sources identified from topographic map and “onthe-ground” surveys: automobile “wrecking” operations
(potential leaching from polyurethane foams) located immediately adjacent to watercourses, landfills situated within
1 km of the Columbia River or along tributaries, major
industries (e.g. pulp and paper mills, hydroelectric dams,
smelters) which may utilize or produce PBDEs, below forest
fire sites on erodible slopes, adjacent to agricultural land
where biosolids may have been applied, and the Castlegar
and city of Nelson municipal sewage outfalls. No clear trends



were observed in PBDE concentrations compared to any of
these potential sources. However, when ΣPBDE concentrations were plotted against the ratio of organic carbon to
organic nitrogen (OC:ON) content in each sample, a moderate
negative log-log correlation (R2 ) 0.62) was observed (Figure
3). Both municipal wastewater and landfill leachate have
been previously shown to have decreased OC:ON ratios
compared to natural aqueous samples (55-60). While no
studies have examined OC:ON ratios in leachate from
automobile wrecking operations, OC:ON ratios in such
leachate are expected to be higher than that of wastewater
and landfill leachate because there is not an appreciable
source of nitrogen in the source material (e.g. rubber,
polyurethanes, and mostly other hydrocarbon polymers) (61,
62). Upon further examination of the sediment samples with
>10 ng ΣPBDE/g OC, these locations are near potential point
and nonpoint (e.g. septic fields) sources of domestic wastewater, and higher concentrations do not correlate well with
known landfill sites. In addition, landfills in the region tend
to be located more distant from waterways than populations
residing directly adjacent to aquatic systems. Thus, sorption
of PBDEs onto saturated subsurface soils will likely hinder
their movement in landfill leachate and the resulting
groundwater, thereby reducing the effects of landfill leachate
relative to the more direct wastewater inputs.
Similar results suggesting municipal wastewater sources
of PBDEs to river sediments and biota have been previously
discussed (along with the likely exclusion of landfill leachate
as a significant source (40)) or is evident from the work of
other researchers (28, 40). PBDE congener patterns in some
municipal wastewater biosolids are also similar to the
commercial penta-BDE mixtures (63), suggesting that municipal wastewater contains similar congener patterns to
these technical mixtures and that the land application of the
resulting sludge may also be a potential source of PBDEs to
aquatic systems through leaching and subsequent transport
processes. Higher PBDE concentrations were not observed
in sediments immediately adjacent to the limited number of
agricultural areas in this region. This suggests the application
of PBDE-contaminated biosolids as an agricultural nutrient
amendment, and subsequent leaching processes, is not a
major PBDE input to this aquatic system. Furthermore, as
noted elsewhere for riverine environments enclosed by
hydroelectric facilities (28), a marine source of PBDEs (either
from anthropogenic or natural (64) sources) to the whitefish
from this portion of the Columbia River is not likely because
the number of dams present in the United States region of
the river prevents upstream movement of aquatic biota (2022). Overall, the ΣPBDE concentrations in sediments reported
here are in the lower end of the range observed elsewhere
(28, 35, 36, 40, 41), possibly because of the general lack of
good depositional areas for fine particulate organic matter,
silts, and clays in the mainstem of the Columbia River. In
various sediments worldwide, BDE99 has been generally
found at a higher contribution to ΣPBDE than BDE47 (35, 36,
40), although one instance where BDE47 dominated the
congener pattern in sediments has also been observed (28).
The absence of BDEs 153 and 154 in these surficial sediments,
and dominance of BDE47 over the more hydrophobic BDE99,
has been discussed above.
A number of small (population <500) communities are
prevalent along waterways through the study area, and, in
sum, the population of these “rural” residents outweigh those
living in the two regional cities (population of 57 000 in the
Regional District of Central Kootenay vs 16 300 in Castlegar
and Nelson). Thus, since most of these residents live along
the shores of the Columbia and Kootenay Rivers and
Kootenay Lake, rural septic field inputs to regional waterways
would be expected to dominate those from Castlegar
(secondary activated sludge treatment) and Nelson (primary

settling treatment). In essence, this “spreads out” the source
of PBDEs throughout the region, assuming no large industrial
point sources, which were not observed according to our
sampling pattern and topographic and field reconnaissance.
Furthermore, septic leachate is largely untreated compared
to the municipal discharges, and this may favor the release
of congener patterns more similar to commercial mixtures.
This may help to explain why, if PBDEs were released from
municipal wastewaters in the Kootenay and Columbia River
systems, our sediment sampling grid did not detect higher
PBDE levels near the major communities of Castlegar and
Comparisons with PCBs and PCDD/Fs. PCB and PCDD/F
concentrations were also determined in whitefish from
Genelle in 1992 and 1994/1995 and Beaver Creek in 1992
(Table 1) (25, 26). While total PCB (ΣPCB) and PCDD/F
(ΣPCDD/F) concentrations declined slightly at Genelle from
1992 to 1994/1995 following installation of an air-activated
sludge secondary treatment system and 100% ClO2 substitution for Cl2 in the bleaching process at the pulp mill upstream
of Castlegar (26), ΣPBDE concentrations increased by a factor
of 3.1 over this period of time. If PBDE concentrations
continue to rise at Genelle in the same manner as they have
since 1992 while PCB levels remain constant or decline,
ΣPBDE concentrations in these whitefish will surpass those
of ΣPCB (86 ng/g ww) by 2003. Likewise at Beaver Creek, the
increasing ΣPBDE concentrations will exceed ΣPCB (70 ng/
g) by 2013. Thus, in a relative short period of time (1-2
decades), compared to PCBs when they were commercially
produced in North America for five decades from the 1930s
to the late 1970s, PBDEs are overtaking PCB burdens in biota
from some regions. Such findings further attest to the ready
transport and bioaccumulation/biomagnification of PBDEs,
a perhaps ironic result if the manufacturing companies had,
in fact, chosen these compounds as commercial flame
retardants not only because of their inherent fire suppression
properties but also because the large molecular size, mass,
and hydrophobicity of these compounds was thought to
hinder environmental transport and biotic uptake.
PBDE Congener Patterns in Whitefish Compared to
Other Aquatic Biota. PBDE congener patterns in whitefish
from the Columbia River are remarkably similar to that of
the commercial penta-BDE mixtures from Great Lakes
Chemical Corporation (DE-71) and Bromkal (70-5DE) (Figure
4). Comparisons among these samples were made on the
basis of the relative contributions of the 13 major congeners
with >30% of values above MDLs. Concentrations of
individual congeners in the two technical mixtures are
provided elsewhere (34). The key to interpreting cluster
analysis plots as shown here is to compare the x-axis values
where the lines from different samples (and/or sample groups
or clusters) meet. The larger the x-axis value (or “distance”),
the lower the similarity in multivariate patterns between the
two samples or groups. In sharp contrast, congener patterns
in whitefish from the unpopulated reference area on the
Slocan River were distinct from those found in whitefish in
the Columbia River, as measured by distance on the cluster
analysis plot. Congener patterns are similar in whitefish from
the two Columbia River sites (Genelle and Beaver Creek),
suggesting a related source of PBDEs for these locations.
This difference in PBDE congener patterns between populated and reference sites further suggests that atmospheric
deposition (which is likely the only PBDE source for the Slocan
River whitefish) is not likely the major PBDE source for
whitefish in the Columbia River. Preferential removal of the
higher brominated BDEs 99, 153, and 154 from the Columbia
River system due to hydrological regimes has been discussed
above and may help explain congener pattern differences
between the Columbia River whitefish and those from the
Slocan River reference site. While a previous report suggested

a similarity in congener patterns between DE-71 (the major
North American penta-BDE product) and sediments and
sewage sludge, these comparisons were made using only the
five major congeners (BDEs 47, 99, 100, 153, and 154) and
with the assumption that DE-71 contained the same relative
proportions of these congeners as 70-5DE (35) for which
congener distributions had been published (65). Previous
work has shown DE-71 to contain slightly higher proportions
of BDEs 153 and 154, and lower proportions of BDEs 47 and
99, compared to 70-5DE (34), although there may be wide
variation in the congener patterns between different batches
of each commercial product. Although such qualitative
insights using the five major congeners are valuable, full
congener data and some type of statistical evaluation are
needed to provide some measure of confidence on congener
pattern comparisons.
Large variations in congener patterns for species occupying similar locales are also evident in the cluster analysis.
Both whitefish from Genelle and Beaver Creek have similar
congener patterns to whitefish from Kootenay Lake (data
not included in cluster plot for clarity but are provided in the
Supporting Information; BDE47: 32.7 ( 2.4%, 32.3 ( 2.4%,
and 36.3 ( 6.5%; BDE99: 41.6 ( 3.9%, 42.7 ( 3.9%, and
39.0 ( 4.7%; BDE100: 12.7 ( 1.3%, 11.4 ( 1.2%, and 11.0 (
1.5%; respectively, for Genelle, Beaver Creek, and Kootenay
Lake); these patterns are quite distinct from largescale suckers
sampled near Taghum on the Kootenay River (BDEs 47, 99,
and 100: 73.7 ( 2.5%, 0.2 ( 0.1%, and 16.2 ( 1.9%,
respectively). Taghum is located approximately 11 km west
of the outlet from Kootenay Lake, and both sites are expected
to have the same ambient PBDE patterns. Thus, there appear
to be significant species-specific UMSE processes between
whitefish and largescale suckers. This is particularly evident
in the low contribution of BDE99 in the largescale suckers
compared to whitefish (0.2% vs 39.0%), which cannot
otherwise be explained in this system where BDE99 seems
prevalent as the first or second most abundant congener.
Congener profiles in ringed seals from the Canadian Arctic
and harbor porpoise and Dungeness crab are also provided
for comparison. These samples have distinct congener
patterns from the Columbia River fish, further demonstrating
the combined effects of species type and location on PBDE

The authors are grateful to Gerry Oliver of Interior Reforestation, Les MacDonald of the British Columbia Ministry of
Water, Land, and Air Protection, and R.L. & L. Environmental
Services Ltd. in Castlegar, BC, for collecting the fish samples.
Many thanks to the Regional Dioxin Laboratory chemists
and laboratory assistants involved in the processing and
analyses of these samples. The authors gratefully acknowledge the manuscript review comments provided by Mike
Whittle. The financial support of the Environmental Sciences
Strategic Research Fund (Fisheries and Oceans Canada), the
Health Canada Toxic Substances Research Initiative Program
(TSRI), and the regional Fisheries and Oceans funding
available to the Regional Dioxin Laboratory at IOS made this
work possible and is appreciated.

Supporting Information Available
PBDE concentrations for all individual fish and sediment
samples. This material is available free of charge via the
Internet at http://pubs.acs.org.

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Received for review January 3, 2003. Revised manuscript
received March 25, 2003. Accepted April 15, 2003.

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