Envlron. Scl. Technol. 1904, 18, 72-79
Sources and Transport of Hydrocarbons in the Green-Duwamish River, Washington Susan E. Hamilton,’ Timothy S. Bates, and Joel D. Cline National Oceanic and Atmospheric Administration, Pacific Marine Environmental Laboratory, Seattle, Washington 98 115
Hydrocarbon concentrations were measured in the suspended matter and sediments of the Green-Duwamish River, Washington (197&1981), in an effort to document the sources, transport, and fate of these organic compounds in a tractable estuary. Hydrocarbon derived from algae, plant waxes, highway runoff, a secondary sewage treatment plant, and sedimentary sources were distinguished from each other. Hydrocarbon transports were calculated at each station. Dilution with pristine particulates and/or particulates associated with highway runoff accounted for transport disparities between stations encompassing no known point sources of hydrocarbons. Compositional effects of the sewage efffluent were observed, but the transport budget could not account for the hydrocarbons contributed by the outfall. Organic matter appears to flocculate and sediment as effluent mixes with river water. This organic-rich layer may be mobilized only during periods of high discharge. H
Introduction In recent years, increasing emphasis has been placed on the transport and fate of hydrocarbons in estuarine and coastal waters. These compounds are introduced into near-shore waters by wastewater discharge, surface runoff, casual spillage, and atmospheric deposition. Since petroleum hydrocarbons are largely hydrophobic and lipid soluble, a major transport mechanism of these compounds in riverine and estuarine systems is via their association with suspended particulates (1). Many of the marine studies to date have addressed the distribution and transport of petroleum hydrocarbons in urbanized estuaries. Farrington and Quinn (2) reported total hydrocarbon concentrations of up to 16.2 mg/L in effluent discharged from three wastewater treatment plants on the Providence River and Narragansett Bay, Rhode Island. Features of the hydrocarbon chromatograms were similar to those of crude and no. 2 fuel oils. Schultz and Quinn (3) reported decreasing hydrocarbon/ suspended-matter ratios from the Providence River into Narragansett Bay and changes in suspended-hydrocarbon composition that suggested sources in the river of petroleum contamination. Van Vleet and Quinn (1)determined that 95% of the total hydrocarbon concentration in the Field Point Treatment Plant effluent was in the form of suspended solids. Concentrations decreased with distance from the outfall, indicating rapid particulate deposition, dilution, and/or desorption. Again hydrocarbon composition was attributed to petroleum contamination. The authors concluded that if the concentration of total hydrocarbons in the Field Point wastewater were extrapolated to sewage discharge nationwide, the flux of hydrocarbons from wastewaters into coastal water would be as important as amounts entering by direct spills. For a pollution problem of such magnitude, it is surprising that individual compound concentrations, compositional parameters, and transports have not been reported to date. *Address correspondence to this author at the University of Washington, School of Oceanography WB-10, Seattle, WA 98105. 72
Envlron. Scl. Technol., Vol. 18, No. 2, 1984
This study was undertaken to examine in detail the sources and transport of suspended hydrocarbons in a small estuarine system. The Green-Duwamish River, which empties into ElIiott Bay within the Port of Seattle, Washington, was chosen for study because it is a tractable estuarine system, small in size, draining a region of moderate population density, and impinged upon by only one major point source of contamination, a secondary waste treatment plant located near Renton, WA (Figure 1). Sampling was designed to measure the seasonal and spatial distributions of suspended hydrocarbons and to identify major sources of these compounds. Emphasis was placed on determining the contribution from the secondary waste treatment plant in Renton operated by the Municipality of Metropolitan Seattle (METRO) and calculating a riverine hydrocarbon transport budget. This documentation of the sources and transport of hydrocarbons associated with particulates in a riverine system is applicable to a myriad of riverine environments impinged upon by natural and anthropogenic sources.
S t u d y Area The Green-Duwamish River system stretches from the western slopes of the Cascade Mountains to Elliott Bay in Puget Sound (Figure 1). From its source, the Green River flows west-northwest through forest, then farmland, and pastureland. At river kilometer 19, the Green River becomes the Duwamish River which meanders through a heavily industrialized region to Elliott Bay. River discharge is high during the late fall and winter, responding to seasonal rainfall (1978 average -40 m3/s ( 4 ) ) . Snow melt extends this runoff into June, after which flow decreases to a minimum in August (1978 average -10 m3/s (4)). The Howard Hanson Reservoir at river kilometer 103 provides water storage for flood control in the winter. Water is dissipated soon after a flood in order to have maximum holding capacity for a subsequent flood ( 4 ) . High discharges (-200 m3/s) of short duration (-2 days) occur approximately twice a year (4). In late spring runoff is stored to augment river discharge during the drier summer months. The four stations occupied in this study depict four different riverine settings, although river width and slope between stations remain approximately the same. The two upper stations correspond closely to USGS and METRO sampling sites, where discharge and suspended solids are monitored. Station 1, above Auburn, represents a relatively pristine environment largely removed from known urban discharges and dominated by coniferous forests and ground vegetation, Station 2 is located 5 km above the Renton Sewage Outfall and serves as a monitor below the urban contributions of the towns of Auburn and Kent, yet above the outfall, so that the effect of the sewage effluent may be isolated. Station 3 is located 0.5 km below the outfall, and station 4, at river kilometer 10.4, is located just above that portion of the river that is dredged for navigational purposes. This latter station is characterized by tidal reversals in flow and salt intrusion at depth. The Renton METRO Sewage Treatment Plant, a large source of organic material to the lower river, discharged
Not subject to U S . Copyright. Published 1984 by the American Chemical Society
122h
Flgure 1. Locations of sampling statlons and the Renton METRO sewage outfall on the Green-Duwamish River, Washington.
an average of 1.4 X lo5m3/day of effluent into the Green River in 1978. The concentration of suspended solids in the effluent ranged from 7.9 mg/L in January to 23.0 mg/L in November with a mean monthly average of 12.5 mg/L (5). The facility receives wastewater from both residential and industrial sources. Up to 25% of the total is industrial in origin. Secondary treatment at this plant removes approximately 94-97% of the organic matter from the influent (6).
Methods River stations were occupied for 18-36 h during which river water was retrieved with a Peabody Barnes submersible pump located midchannel and at middepth. Water was directed through an intake manifold and prefiltered through two nylon screens, the smallest being 100 pm in mesh size. To reduce contamination, the pump, manifold, and tubing were flushed with ambient water at each station for 30 min before the centrifuge was engaged. Suspended solids were collected continuously with a Sorvall Model SS-3 high-spreed centrifuge operating at 21 000 gravitational units and exhausting supernatant at the rate of 400-500 mL/min. Suspended matter was collected in eight 50-mL stainless-steel tubes. At the termination of sampling, excess water was decanted from each tube, and sediment was scraped into a sample jar and quickly frozen on dry ice. Centrifuge efficiency was tested at station 3 in Oct 1980 by passing centrifuge influent and effluent through preweighed 0.4-pm Nuclepore filters. Over a 24-h period, efficiencies varied from 63% to 92%, the average being 78 f 11Yo (one standard deviation expressed as a percentage of the mean). Highest efficiencies occurred close to periods
of low tide when river flow was at a maximum and larger particles were in suspension (7). These recoveries were comparable to those of glass-fiber filters in a study conducted on both sewage effluent and river water (7). Every 4 h water from the intake manifold was passed through Selas silver filters and Nuclepore membrane filters for total particulate carbon (TPC) analysis and total suspended matter (TSM) determinations. Prior to sampling, the 0.45-pm silver filters (25 mm in diameter) were combusted at 400 “C for 4 h. The total carbon samples were vacuum filtered through a glass filtration system. The filters were frozen immediately and later analyzed by the micro-Dumas combustion method (8) using a HewlettPackard Model 185B C-H-N analyzer. Total carbon was calculated based on combustion of known weights of NBS acetanilide. Precision of the total carbon analysis was *9% (one standard deviation expressed as a percentage of the mean); sampling variability based on previous work averaged f20%. Water was also vacuum filtered through preweighed 0.4-pm pore size Nuclepore polycarbonate filters (47 mm in diameter). TSM concentrations were calculated from the weight differences and volume of water filtered. These values were used only to calculate the amount of suspended material on the silver filters. The TSM amounts used in subsequent concentration and budget calculations were determined from the dry weight of the centrifuge sample and the volume of water passed through the centrifuge, which was monitored electronically. Discharge information was obtained from the U S . Geological Survey’s Water Resources Data (4). The average discharge for the period during which each station was sampled is reported in Table I and is used in all budget calculations. Bottom sediment samples (Oct 1980) were collected midchannel with a Van Veen grab sampler. In Feb 1981, a portion of the water from the pump was diverted through a 64-pm mesh plankton net. Two fractions of this material, 64-332 and >332 pm, were then separated by using stainless-steel sieves. Renton METRO sewage effluent samples (totaling -3200 mL) were taken concurrently with river samples and were composed of 200-300-mL aliquots withdrawn every 2 h from the plant effluent. These samples were poisoned with either sodium azide or mercuric chloride and were vacuum filtered through Gelman glass-fiber filters (type A/E, 47 mm in diameter). The filters were cleaned by combustion a t 450 OC overnight and by Soxhlet extraction in CH2C12/CH30H. All samples were spiked with recovery standards and Soxhlet extracted for 48 h in 65% CH2C12/35%CH,OH in preextracted, preweighed Whatman cellulose thimbles. Thimbles were then dried and weighed to calculate sediment dry weight by difference. Approximately 97% of the total extractable hydrocarbons was recovered in the original 48-h period. Following extraction, samples were washed with distilled water to remove the methanol and passed through a silica gel column topped with 5 g of activated copper powder to remove water, pigments, and elemental sulfur. The “saturated” fraction (containing some straight-chained alkenes, but not aromatic hydrocarbons) was eluted from a second silica gel column with 2 column volumes of petroleum ether. Samples were reduced, and a known volume of GC internal .standard (hexamethylbenzene) was added. Total saturates were measured by weighing an aliquot of this sample after solvent evaporation. Solvent blanks were run concurrently with each set of extractions. Concentrations in the blanks comprised an average of 4% of the n-alkane hydrocarbons Envlron. Scl. Technol., Vol. 18, No. 2, 1984
73
Table I. Concentrations and Compositional Parameters of Hydrocarbons Associated with Suspended and Bottom Sediments Recovered from the Green-Duwamish River and Suspended Solids Obtained from Renton, METRO Sewage Effluent sample typea Oct 1978 station 1 station 2 effluent station 3 Dec 1978 station 1 station 2 effluent station 3 Oct 1980 station 1 station 2
Feb 1981 effluent station 3
52 120 3500 660
sm sm sm sm
630 410 12000 740
240 120 4100 3 20
2.5 1.6 1.1 1.0
sm sm
280 480 10 18000 4200 6 2100 230
70 200 3 9500 2900 4 1100 160
1300
100
sm sm sm bs sm sm (total) sm (64-332 pm) (>332 pm)
a
Pr /
c,,
300 8700 2000
bs
station 4
UCM, pg/g
sm sm sm sm
bs
effluent station 3
total saturates,
discharge, T S M , ~ TPCC wt m3/s mg/L
0.04 0.17 0.42 0.28
2.2 2.9 1.3 1.5
10.7 12.1 1.6 13.7
1.4 2.2 8.8 2.5
12 9.3
14 10 1.6 5.0
0.50 0.60 1.5 0.68
1.1 1.5
34.3 39.1 1.7 40.8
3.2 5.1 15.3 6.9
15.4 3.1
25 10 1.0 4.6 8.0 1.1 3.4 2.7
8.5 6.1 2.3 1.3 1.5 2.3 2.1 3.6
0.03 0.06 14.3 0.31 0.19 2.36 0.40 0.79
2.7 2.3 10.1 0.9 1.1 3.7 1.7 2.1
12.7 12.8
1.2 1.8
7.3 6.8
1.4 14.2
16 1.8
1200 50
2.4 1.5
1.3 7.5
0.30 0.6
1.0 2.2
2.0 210
300
110
1.6
7.8
1.3
4.6
23
600
210
1.7
8.9
0.4
2.4
41
100
sm/bs, suspended matter/bottom sediment.
11 2.6 2.3 3.1
Environ. Sci. Technol., Vol. 18, No. 2, 1984
7.5 8.0 1.1 2.6
Total suspended matter,
measured in centrifuge sediment samples. Saturate hydrocarbon samples were analyzed on Hewlett-Packard Model 5730A or 5880 gas chromatographs temperature programmed from 70 to 270 OC at 4 OC/min. Component separation was accomplished by splitless injection on an SP-2100 WCOT glass capillary column, 30 m X 0.25 mm i.d. (J & W Scientific, Inc.), equipped with a flame ionization detector. Component concentrations were calculated by using response factors determined from a composite standard run daily. Concentrations were normalized to these external standards by use of an internal standard added just prior to injection (14). Losses such as evaporation were accounted for by applying the resulta from the recovery standard and an alkane recovery curve determined by spiking preextracted sediment with a known quantity of standard containing alkanes C12 through C32. The analytical precision based on multiple standard runs ranged from 2% to 8% for each compound. The chromatographic "hump", referred to in saturate samples as the unresolved complex mixture (UCM), is defined here as the concentration indicated by the area enclosed within the base line and tangential skim at the base of each peak from C14to C3* Straight-chained alkenes were hydrogenated by adding Pt02 and bubbling H2 through selected samples for 30 min. In Dec 1978, station 3 was occupied for 36 h to recover enough sediment for triplicate analyses. The mean relative standard deviation for all n-alkanes was *9%. The lowmolecular-weight hydrocarbons (C13 to Czo) showed significantly greater variabilities (*13%) than heavy hydrocarbons (C13 to C20,f7%). Station 3 was occupied for two consecutive 18-h periods in Oct 1978. These duplicates are the closest measure of sampling variability obtained. The difference between the two values divided by their mean averaged 24% for all the n-alkane compounds identified. 74
Pr I PhY
1.2 1.8
19
3.6
(-0.1) 16
(-0.1) 3.6
7.3 1.7
8.8
26 5.5
Total particulate carbon.
Results and Discussion Sources. The abundance of information on natural and anthropogenic sources of hydrocarbons provides a convenient means for identifying the origins of these compounds along the Green-Duwamish River. The hydrocarbon compositions of suspended matter and sediment extracts indicate five distinguishable sources: aquatic production, plant wax contributions, highway runoff, sewage effluent, and erosion of river sediments. (1) Aquatic Production. Pentadecane and heptadecane, dominant compounds in freshwater planktonic detritus (9),are abundant in the October suspended matter and METRO samples (Figures 2 and 3). These aquatic hydrocarbons are noticeably less predominant during the winter/ high-runoff periods of December and February. Several C17 monoenes (Kovats index IS^-^^^^ = 1665-1700) are present in the October suspended-matter samples (Figure 2). These compounds are converted to heptadecane under mild hydrogenation. Algae appear to be a primary source of heptadecene (10). A C17monoene has also been identified by Crisp et al. (11) in sediment trap particulates retrieved off the coast of southern California. Three dominant hydrocarbons at stations 1and 2 in Dec 1978 were phytadienes (M, 178). The three compounds (Isp-2100 = 1836, 1862, and 1880) were quantitatively converted to phytane under mild hydrogenation. The compounds occurred in the same ratios at both stations 1and 2 (11214) and were present at concentrations (17.5 pg/g station 1; 7.6 pg/g, station 2) approximately equivalent to the high-molecular-weight, odd-carbon alkanes ((225, C27, and C29). Phytadienes are likely derived from the dehydration of phytol and have been found in zooplankton (12), benthic algae (13),and sediments (14). Present data are insufficient to determine if the phytadienes at stations 1 and 2 are aquatically produced or if they result from the decomposition of plant tissue. The compounds were de-
STATION 2
STATION I
I IO
SEDIMENT
I
150
190
STATION 2
2 30
270
IHOLDINGI
17
150
I IO
'9C
23C
270
~HOLD~NG~
I90
230
270
IHOL3NGI
METRO I
I IO
E
I50
STATION 3
'i
I IC
I
I50
I90
230
270
m
IHOLDINGI
':
I IO
I50
T E M P E ~ A T J R E "C
Figure 3. (Top) Chromatographictrace of the aliphatic hydrocarbon fraction extracted from station 2 bottom sediments. (Bottom) Chromatographic trace of the aliphatic hydrocarbon fraction obtained from METRO effluent suspended matter.
I90 -EMPERATURE
230
270
('IOLDINGI
("C'
Figure 2. Gas chromatograms of the aliphatic hydrocarbon fractions extracted from Green-Duwamlsh River suspended matter. Samples were retrieved by centrifugation in Oct 1978. Chromatographic parameters are explained under Methods.
tected during only one of the four sampling periods and were not present at station 3. The disappearance of the phytadienes in the short distance (4.3 km)between stations 2 and 3 implies that these hydrocarbons are relatively reactive. The concentration of phytane at station 3 is insufficient to account for the hydrogenation of these compounds. (2) Plant Wax Contributions. A relative indicator of plant wax sources is the carbon preference index (CPI) calculated for the heavier hydrocarbons CZO through C32. The CPI is a weighted ratio of odd- to even-carbon n-alkanes (15). CP12,32 values between 4 and 10 usually suggest vascular land plant production of alkanes (16). The index was highest a t station 1 (7.5-14; Table I), reflecting the heavily forested drainage basin. The ratio decreased downriver to values averaging -4.3 at station 3, corresponding to the lower concentrations of terrestrially derived plant wax components. (3) Runoff. The influence of runoff is reflected by changes in the carbon preference index extending over the low-molecular-weight fraction CI4through C2@The CPI in this range shows the relative importance of those hydrocarbons contributed by plankton and algae, Cl5 and C1, (161, compared to compounds with no known recent bio-
logical source such as C16. The CPIl4-20 values (Table I) drop between stations 1and 2, reflecting a relative increase in the concentrations of the even-carbon compounds C14 and Cle. Crude oils and their refined products demonstate CPIlkZOvalues of approximately unity (17). Wakeham (9) reported an average CP114-20value of 1.2 for storm water and bridge runoff. The relative changes in concentrations of the LMW odd- and even-carbon compounds between stations 1and 2 may be due to diffuse injections of surface runoff contaminated with fossil fuel hydrocarbons. A survey of the Green River in Feb 1980 located 49 pipes between stations 1 and 2 of which 29 are known to transport highway runoff. (4)Sewage Effluent. A number of parameters listed in Table I demonstrate the influence of the outfall effluent on the hydrocarbon characteristics of riverine suspended matter. Gravimetric analyses of the total saturate fraction show results ranging from 100 to 4200 pg/g in the river with the higher concentrations consistently measured at station 3. The increase between stations 2 and 3 is due to dilution of the effluent hydrocarbon concentrations which are at least an order of magnitude greater than the river values. Concentrations measured in the outfall and at station 3 are greater than those reported for surface sediment in the Gulf of Mexico (0.1-7 pg/g (18)))the Northwest Atlantic slope and shelf (37 pg/g (19)),Narragansett Bay (173 pg/g (20)),and Puget Sound (4-350 pg/g (14)). Values measured in this study are on the order of concentrations measured in the surface sediments of Lake Washington, a freshwater lake near Seattle, WA (280-1700 pg/g (9)). Cycloalkanes, naphthenoaromatics, and other compounds present in the aliphatic hydrocarbon fraction elute from a GC column as a "hump" called the unresolved complex mixture (UCM) (21). This envelope of unresolved Environ. Sci. Technol., Vol. 18, No. 2, 1984
75
compounds is characteristic of petroleum hydrocarbons. The relative magnitude of the UCM has been used to approximate the anthropogenic contribution to hydrocarbon assemblages (2). Figures 2 and 3 show chromatograms representing the aliphatic fraction of riverine suspended-matter samples and the corresponding sewage effluent samples obtained in Oct 1978. In all samples, the UCM was unimodal, reaching a maximum near heptacosane. The absolute concentrations of the UCM increase as one proceeds downstream ranging from 52 to 240 pg/g at station 1and 50 to 2900 pg/g at station 3. The greatest increase occurs between stations 2 and 3 and is, again, an example of dilution of the effluent contribution (1200-4100 pg/g). If the riverine values are divided by the weight percent of total carbon in their respective sediments, UCM concentrations are on the order of those measured in post-1955-dated sediments of Puget Sound (14). Changes observed in the CPI,,, values between stations 2 and 3 are the result of the outfall effluent, which is characterized by relatively low indexes averaging 2.6. The CP120-32values also demonstrate an increase in the relative proportion of even-carbon compounds between stations 2 and 3. Values of 1.1-1.6 were calculated for the outfall effluent samples. Ratios of approximately 1 are typical of petroleum products and bacteria, both of which are probably present in the sewage effluent. Dilution of the effluent hydrocarbons is responsible for the reduction in riverine values from an average of 8.1 at station 2 to 4.2 at station 3. Pristane/C17 ratios are elevated in the effluent due to the amounts of C17that are relatively reduced when compared to the concentrations produced in the river by algae. Pristane/phytane ratios of approximately 1characterize the sewage effluent. The changes in both of these parameters between stations 2 and 3 demonstrate the mixing of effluent hydrocarbons with riverine suspended hydrocarbons. (5) Sedimentary Hydrocarbons. Bottom sediments collected at stations 2 and 3 (Oct 1980) consisted mainly of sand-sized particles while sediments at station 4 were much finer grained. The river bed at station 1,consisting of rubble, was inappropriate for sampling. The hydrocarbon composition of the surficial sediment at station 4 closely resembled that found in the suspended matter. The aliphatic extract of the bottom sediments at stations 2 and 3, however, revealed another source of hydrocarbons to the Green-Duwamish River system. The predominant compounds in these extracts were terpenoids (Figure 3). Sesquiterpenoids have been reported in crude oils (22), coals (23),and fossil resins (24),but due to their relative instability they are seldom found in sediments. The sesquiterpenoids from the Green-Duwamish River are methyl-, ethyl-, and propyl-substituted compounds with molecular weights of 206 and 208. The mass spectra do not match those of the compounds identified by Bendoraites (25) or Grantham and Douglas (24). Diterpenoids are common isoprenoids in fossil and tree resins (23). The Green-Duwamish River diterpenoids were present in total concentrations of 4.3 pg/g at station 2 and 0.4 pg/g at station 3 (Figure 3, Dl-D9). The mass spectra of D3, D4, D5, and D7 match those reported by Barrick and Hedges (26) for four ClQHS4diterpenoids found in Puget Sound sediments. The Kovats indexes of the Green-Duwamish River diterpenoids are 0.12 unit lower due to differences in column film thickness (SP-2100 Supelco vs. SP-2100 J & W Scientific). The mass spectra of D1, D2, D3, and D5 are similar and are probably derivatives of pimaric and isopimaric acid. Measurable quan76
Environ. Scl. Technol., Vol. 18, No. 2, 1984
tities of D1 and D2 were not detected in Puget Sound sediments (26). Three CZoH3, diterpenoids were also present in the riverine sediment (D6, D8, and D9). D8 and D9 have been previously reported by Barrick and Hedges (26). Diterpenoid hydrocarbons were detected in suspended-matter extracts only in Feb 1981, a period of extremely high discharge augmented by runoff from the Howard Hanson Reservoir (4). The centrifuge sample contained 2.2 pg/g of diterpenoid hydrocarbons, most of which were associated with the >332-pm particle size fraction. These compounds would appear to be erosional in nature and associated with large particles not mobilized during average discharge conditions. Several triterpenoids were present in the riverine sediment samples. Eluting between Cs0 and C31 (Figure 3) were four compounds with a molecular weight of 410. The most abundant triterpane matches the spectra of olean13(18)-ene (27). The fractionation patterns of the other three C30H50 compounds suggest related structures with varying placements of the double bond. Two C31H64 triterpanes eluted at Kovats indexes -3200 and 3210. The compounds were resolvable from C32 on an SE-54 column (ISE-54 = 3209 and 3222) and have been identified as 17a(HI- and 21/3(H)-hopanesbased on their retention times (26) and mass spectra (28). Pristane is a major component in the riverine bottom sediments but is not a dominant component in the suspended matter. It is therefore unlikely that zooplankton (29) are a major source of this compound to the coarse bottom sediment. Fossil fuel (30)is also an unlikely source of pristane to these bottom sediments since the phytane and UCM concentrations are very low. Barrick et al. (14) reported a natural assemblage of isoprenoid hydrocarbons in Puget Sound sediments. The Green-Duwamish River sediments, however, do not have the correspondinglyhigh concentrations of the other isoprenoids to accompany the abundance of pristane. There appears to be an additional source of pristane which is related to the diterpenoids. Robert Barrick has also found abnormally high pristanelditerpenoid levels at both the top and bottom of two southern Puget Sound cores collected near the Puyallup and Nisqually Rivers (31). A possible, but yet untested, source for the terpenoids and some of the pristane in the coarse Green-Duwamish river sediments is coal fragments. The river drainage basin contains several coal outcrops from the Hammer Bluff formation (upper Miocene) and Puget Group (upper Eocene) which were mined intermittantly for about 100 years (32). Although terpenoids are not present in the riverine suspended matter under normal flow conditions, they are suspended and moved downstream to Puget Sound during periods of high runoff (Feb 1981). The distribution of these compounds illustrates the importance of river discharge and particle size in the transport of organics in the river. Random measurement of riverine suspended matter is not necessarily an accurate estimate of the hydrocarbons reaching coastal waters. Hydrocarbon Transport. Transports of suspended hydrocarbons were calculated at each station from a knowledge of hydrocarbon concentrations, the magnitude of the suspended load, and river discharge. For simplicity these calculations assume a homogeneous well-mixed parcel of water moves downstream with no dispersion. Imbalances between stations were examined for sources and sinks of suspended hydrocarbons. Equations l a and l b describe suspended-hydrocarbontransport in the upper Ts = T2 - Ti (la) Ts = C2PzD2 - ClPlDl Ob)
Table 11. Results of the Suspended-Hydrocarbon Transport Budget Calculation for the Green Rivera Oct 1978 Dec 1978 Oct 1980 20
(1)deficit T,, mg/s
( 2 ) outfall/station 3, T0/T3
( 3 ) deficitlstation 3, TdT3 ( 4 ) station 2 ( 5 ) station 4
32
r: alk
C
13
21
20
32
alk
c alk
C
alk
13
13
32
32
20
I: alk
I: alk
C
21
13
13
32
alk
C
32
alk
21
C
alk
13
-1.88 1.71
-10.8 11.0
-12.6 5.19
-0.52 0.70
-9.86 1.32
-10.4 1.12
-1.13 2.12
-2.30 2.70
-3.43 2.43
-1.13
-10.9
-4.78
-0.12
-1.04
-0.75
-1.39
-2.41
-1.94
0.43
calculated concentration/measured concentration 1.02 0.75 0.33 1.06 0.91
0.97 0.91
1.02 0.83
1.01 0.87
a Row 1 presents the hydrocarbon transport deficits (2's). Rows 2 and 3 compare the transports due t o the outfall ( T o ) and the deficits ( T s )t o the transports measured at station 3 ( T 3 ) . Rows 4 and 5 compare the measured t o calculated hydrocarbon concentrations at stations 2 and 4, assuming that hydrocarbons associated with suspended matter at stations 1 and 3 are being diluted with pristine suspended material.
portion of the Green River. T = transport (pg/s), C = hydrocarbon concentration (pg/g), P = suspended-particulate concentration (g/m3), and D = discharge (m3/s). Subscripts 2,1, and S refer to stations 2 and 1and diffuse sources/sinks, respectively. Since major point sources of sediment and hydrocarbons between stations 1 and 2 are unknown, the effect of dilution was examined directly. It is assumed that the concentrations of hydrocarbons associated with the increased quantity of suspended-matter contributed by diffuse sources (runoff, eroded, or resuspended sediments) are negligible. Concentrations expected at station 2 are thus calculated (eq 2) and compared to
observed concentrations. The results of this comparison indicate that dilution plays a major role in the transport of the heavier suspended hydrocarbons, CZl through C32(Table 11; measured/calculated ratios). No major source of these compounds is apparent between stations 1and 2. In Oct and Dec 1978, the calculated concentrations of the low-molecular-weight (LMW) hydrocarbons at station 2 were much less than the measured concentrations, indicating sources of these components in the upper river. Separate calculations for oddand even-carbon compounds show that the LMW oddcarbon alkanes are influenced more by dilution than the even-carbon compounds. This implies that there are sources along the river contributing greater relative proportions of the LMW even-carbon compounds. Such a source might be surface (highway) runoff which contains nearly equal concentrations of LMW odd- and even-carbon compounds. The effects of dilution on suspended-hydrocarbon concentrations were also estimated between stations 3 and 4. Discharge data are unavailable at station 4,but there are no significant sources of water between these stations. Equation 3 was used to calculate the concentrations exc 4
c3p3
=p4
(3)
pected at station 4. Calculated and measured concentrations were in near agreement for both the LMW and heavy hydrocarbon fractions, indicating the dominance of a dilution effect. Between stations 2 and 3, quantitative data are available for one source, the Renton outfall, in addition to the two end members. The hydrocarbon transport measured at station 3 should equal the sum of three terms: the
transport measured at station 2, the input resulting from the outfall, and the amount contributed by diffuse sources between these stations. The transport due to diffuse sources is expressed in eq 4. Variables represent the same (4) Ts = C3P3D3 - CzPzDz - C#$O parameters defined in eq l b and subscripts 3, 2, and 0 refer to stations 3 and 2 and the outfall, respectively. Results of this calculation appear in Table 11. Both the LMW and heavy alkanes show deficits. A lower hydrocarbon transport than expected is measured at station 3 based on transport at station 2 and the outfall. The heavier alkanes account for a greater portion of this total deficit than the lighter paraffins. In most instances the deficits correspond closely to the proportion of hydrocarbons contributed by the outfall (compare To/ T3and Ts/T3in Table 11). The Renton sewage outfall is a greater source of heavy even-carbon compaunds than of the plant wax compounds measured at station 3. There is a correspondingly greater relative deficit of these even-carbon compounds at station 3. The disparities in transport have a number of plausible explanations: biological modification, incomplete mixing of effluent and river water, desorption and volatilization, overestimation of the effluent hydrocarbon contribution, and flocculation and subsequent sedimentation. These possible hypotheses are considered below. (1) The wastewater is dechlorinated just before discharge, allowing microbial activity to resume as the wastewater is transported through the 0.5-km pipe to the outfall. Biological modification within such a short time period, however, seems unlikely. Similarly, it is improbable that the alkanes are biologically altered within the river environment between the outfall and station 3, another 0.5 km. In addition, the UCM budget shows a deficit at station 3 for all sampling periods. If the hydrocarbon losses were due to biological modification, one would expect the UCM to remain more impervious to attack. (2) The budget anomalies may be the result of incomplete mixing between the effluent and the river water. The effluent at station 3 may be present as a well-defined water mass distinguishable from the river water. The changes noted in hydrocarbon composition between stations 2 and 3, however, are convincing evidence that we are sampling a portion of the sewage effluent (Table I). (3) Desorption and volatilization are not likely dominant processes since it is the heavy compounds that are preferentially lost. The heavy hydrocarbons are more hydrophobic than the LMW compounds, and they therefore should bind more tenaciously to the particulate phase. If desorption and volatilization were occurring, a preferential Environ. Sci. Technol., Vol. 18, No. 2, 1984
77
loss of the lighter compounds would be expected. This is not the case. (4) The heavy hydrocarbon deficit between stations 2 and 3 may be due to an exaggerated estimation of the suspended hydrocarbon concentrations present in the effluent, an artifact of the filtering procedure. The glassfiber filters coated with the effluent’s complex suspended-solid matrix act as scavenging mats retaining colloidal and dissolved hydrocarbons. However, concentrations of n-alkanes in glass-fiber filter samples compared favorably with those obtained by centrifigation in a subsequent study of METRO effluent (7). (5) The loss of suspended hydrocarbons between stations 2 and 3 may be due to flocculation and subsequent sedimentation of organic matter as the complex effluent matrix mixes with river water. The removal of trace metals between stations 2, 3, and 4 supports the contention that flocculation of organic matter is occurring (33). The less soluble heavy hydrocarbons would be deposited on a particulate phase more readily than the volatile compounds, accounting for the greater deficits of the heavy hydrocarbons. The suspended matter shows higher CP114-20 values than the bottom sediments, reflecting the abundance of the algal hydrocarbons, C15and C1,, in the suspended material. The CP120-32 numbers are greatest in the suspended material at station 2, indicating the dominance of plant wax components. A t stations 3 and 4 the CP120-32 values are lower in the suspended layer than in the bottom sediments, probably due to the near equal contribution of heavy odd- and even-carbon suspended hydrocarbons introduced by the outfall. Pr/C17 ratios were consistently higher in the bottom sediments and Pr/Phy results were lower in the suspended material. Most of the pristane appears to be associated with heavier material and terpenoids. Phytane and C17are allied with the lighter phases. At each station, the concentrations of total saturate hydrocarbons and the UCM were greater in the suspended matter and lower in the bottom sediments (Table I). Overall, the highest concentrations of the UCM and total saturates were associated with suspended matter retrieved at station 3 while values at station 4 were a factor of two lower. In contra& bottom sediments at station 4 exhibited concentrations far in excess of those measured at station 3. The results of the suspended-matter/ bottom sediment comparisons in conjunction with the budget deficit at station 3 might imply that the suspended hydrocarbons injected by the outfall flocculate and settle to the sediment/water interface where they are transported as bedload and deposited in areas further downstream where there is less turbulence (as at station 4). Variations in river velocity, tidal currents, intermittent runoff, and the readjustment of reservoir levels affect the movement of sdicial bottom sediments. The diterpenoids, for example, were detected in high concentrations in surface sediments but were found in the suspended matter only during the extraordinarily high discharge in Feb 1981 which was the result of heavy rains and a large discharge from the Howard Hanson Reservoir. Fractionation of the suspended matter in Feb 1981 (Table I) showed that the larger size fractions contained higher concentrations of particulate carbon, total saturates, UCM, and diterpenoids. Conclusions Five major sources of hydrocarbons have been defined along the Green-Duwamish River. The plant wax hydrocarbons are the predominant compounds in the upper river. Pentadecane, heptadecane, and several C17mono78
Environ. Scl. Technol., Vol. 18, No. 2, 1984
enes are produced by algae in the river. Highway runoff along the river contributes the suite of C14-C2aalkanes. The terpenoids and high concentrations of pristane appear to be erosional in origin and are periodically transported down the river under high flow conditions. A secondary waste treatment plant is a major point source of hydrocarbons to the river. The differences in hydrocarbon concentrations between stations 1and 2 and stations 3 and 4 can be accounted for largely by simple dilution. The hydrocarbon transport budget between stations 2 and 3 cannot quantitatively account for the hydrocarbons added by the Renton Sewage Treatment Plant. Although the input of METRO can be seen qualitatively at station 3, it cannot be accounted for quantitatively. The best explanation for this disparity is the flocculation and sedimentation of organic matter during mixing of the effluent and river water with subsequent near-bottom transport of this material during periods of high river flow. Acknowledgments We thank A. Young for his assistance in the field and J. Quan and M. Caffrey for their efforts in the laboratory. Richard Finger of the Renton METRO Sewage Treatment Plant generously supplied us with effluent samples. Herbert Curl, Jr., and Richard Feely were helpful in reviewing the manuscript. Robert Barrick provided invaluable assistance both in scientific discussion and in reviewing the manuscript. Literature Cited (1) Van Vleet, E. S.;Quinn, J. G. Enuiron. Sci. Technol. 1977, 11, 1086-1092. (2) Farrington, J. W.; Quinn, J. S. J. Water Pollut. Control Fed. 1973,45,704-712. (3) Schultz, D. M.; Quinn, J. G. Org. Geochem. 1977,1,27-36. (4) U.S. Geological Survey “Water Resources Data from Washington”; Western Washington, 1978; Vol. 1, pp 1-431. (5) Municipality of Metropolitan Seattle (METRO), 1978, Renton Treatment Plant monthly data sheets. (6) Acher, S. L. M.S. Thesis, University of Washington, Seattle, WA, 1975. (7) Bates, T. S.; Hamilton, S. E.; Cline, J. D. Estuarine Coastal Shelf Sci. 1983, 16, 107-122. (8) Sharp, J. H. Limol. Oceanoqr. 1974, 19, 984-989. (9) Wakeham, S. G. Ph.D. Thesis, University of Washington, Seattle, WA, 1976. (10) Philp, R. P.; Brown, S.; Calvin, M.; Brassel, S.; Eglinton, G. “Environmental Biogeochemistry and Geomicrobiology”; Krumbein, W. E., Ed.; Ann Arbor Science: Ann Arbor, MI, 1977; Chapter 22, pp 255-270. (11) Crisp, P. T.; Brenner, S.; Venkatesan, M. I.; Ruth, E.; Kaplan, I. R. Geochim. Cosmochim. Acta 1979, 43, 1791-1801. (12) Blumer, M.; Thomas, D. W. Science (Washington, D.C.) 1965,147,1148-1149. (13) Lytle, J. S.; Lytle, T. F.; Gearing, J. N.; Gearing, P. S. Mar. Biol. 1979,51, 279-288. (14) Barrick, R. C.; Hedges, J. I.; Peterson, M. L. Geochim. Cosmochim. Acta 1980, 44, 1349-1362. (15) Clark, R. C.; Finley, J. S. In “Proceedings of the 1973 Joint Conference on Prevention and Control of Oil Spills”; API/EPA/USCG: Washington, DC, 1974; pp 161-172. (16) Clark, R. C.; Blumer, M. Limnol. Oceanoqr. 1967,12,79-87. (17) Clark, R. C.; Brown, D. W. In “Effects of Petroleum on Arctic and Subarctic Marine Environments and Organisms”; Malins, D., Ed.; Academic Press: New York, 1977; Chapter 1, pp 1-89. (18) Gearing, P.; Gearing, J. N.; Lytle, T. F.; Lytle, J. S. Geochim. Cosmochim. Acta 1976. 40. 1005-1017. (19) Farrington, J. W.; Tripp; B. W. Geochim. Cosmochim. Acta 1977, 41, 1627-1641.
Environ. Sci. Technol. 4984, 18, 79-81
Wade, T. L.; Quinn, J. G. Org. Geochem. 1979,1,157-167. Blumer, M.; Souza, G.; Sass,J. Mar. Biol. 1970,5,195-202. Philp, R. P.; Gilbert, T. D.; Friedrich, J. Geochim. Cosmochim. Acta 1981,45, 1173-1180. Streibl, M.; Herout, V. In “Organic Geochemistry Methods and Results”;Eglinton, G.; Murphy, M. T. J.,Eds.; Springer: New York, 1969; pp 402-424. Grantham, P. J.; Douglas, A. G. Geochim. Cosmochim. Acta 1980,44,1801-1810. Bendoraites, J. G. In “Advances in Organic Geochemistry”; Tissot, B.; Bienner, F., E&.; Editions Technip: Paris, 1973; pp 209-224. Barrick, R. C.; Hedges, - J. I. Geochim. Cosmochim. Acta 1981,45, 381-392. Ekweozor, C. M.; Okogun, J. I.; Ekong, D. E. U.; Maxwell, J. R. Chem. Geol. 1979,27, 29-37. Ensminger, A.; Van Dorsselaer, A.; Spyckerelle, C.; Albrecht, P.; Ourisson, G. In “Advances in Organic Geochemistry 1973”;Tissot, B.; Bienner, F., E&.; Editions Technip: Paris, 1974; pp 245-260.
(29) Blumer, M.; Mullin, M. M.; Thomas, D. W. Helgol. Wiss. Meeresunters. 1964, 10, 187-201. (30) Han, J.; Calvin, M. Proc. Natl. Acad. Sci. U.S.A. 1969,64, 436-443. (31) Barrick, R., University of Washington, Seattle, WA, personal communication, 1982. (32) Mullineaux, D. R. Geol. Surv. Prof. Pap. (U.S.) 1970, No. 672, 1-92. (33) Curl, H., Jr.; Baker, E. T.; Cline, J. D.; Feely, R. A. Estuarine and Coastal Pollutant Transport and Transformation, the Role of Particulates, NOAA/OMPA Section 202 Research Program, Pacific Marine Environmental Laboratory, Seattle, WA, 1981, Annual Report, pp 1-104.
Received for review August 2,1982. Revised manuscript received J u l y 21,1983. Accepted August 15,1983. This study was supported by the Office of Marine Pollution Assessment (section 202) of N O A A . Contribution No. 545 f r o m the N O A A I E R L Pacific Marine Environmental Laboratory.
A Simple Method for Determining Bioconcentration Parameters of Hydrophobic Compounds Sujit Banerjee,” Richard H. Sugatt, and Dean P. O’Grady Life and Environmental Sciences Division, Syracuse Research Corporation, Syracuse, New York 13210
A method for the determination of uptake and clearance rate constants during the bioconcentration of toxicants in fish is described and validated. The procedure is limited to stable lipophilic compounds and requires the exposure of fish to an aqueous solution of toxicant under static conditions and measurement of toxicant loss from water with time. The rate constants are obtained from the time-concentration profile with the use of an iterative computer program. Bioconcentration factors obtained for pentachlorobenzene, two isomers of tetrachlorobenzene, and l,4-diiodobenzenewere consistent either with previous determinations or with expectations based on the octanol-water partition coefficient. The measurements with pentachlorobenzene were made over a 100-fold range of chemical concentration. No dependence of the bioconcentration factor on chemical concentration was observed, in accordance with a simple first-order uptake and depuration model, but in contrast to reported data on chlorinated diphenyl ethers and brominated toluenes.
Introduction The bioconcentration factor (BCF) of an organic compound in fish is generally measured in one of two ways. In the first, fish are exposed to an aqueous solution of the toxicant in a static system, and the concentration of the chemical in fish and water is monitored until equilibrium is reached (1). The concentration ratio of the compound in fish to water then represents the BCF. The disadvantages of the method are that potentially toxic metabolites may accumulate, the test must be continued to equilibrium, and rate data are generally not obtained. The second method (1) utilizes a flow-through approach where the toxicant concentration is held constant, and the accumulation of the compound in fish is measured until equilibrium is reached. The fish are then transferred to clean *Address correspondence to this author at the Safety and Environmental Protection Division, Brookhaven National Laboratory, Upton, NY 11973. 0013-936X/84/09 18-0079$01.50/0
flowing water, and the release of the toxicant from the fish is followed until the material is substantially cleared. Analysis of the concentration-time profiles obtained from the uptake and clearance phases then yields the corresponding rate constants. Both methods are fairly time consuming, and despite the modification of Branson et al. (2) which condenses the flow-through procedure, a BCF measurement remains a major experimental undertaking. We have developed a simple, reliable, and inexpensive method of measuring bioconcentration factors and rate constants as a prelude to a broader study on the mechanism of bioconcentration of persistent organic compounds, and in this paper we describe our approach and validate it through measurements with a number of halobenzenes.
Experimental Section Fish were obtained commercially and were held for at least 14 days prior to use. Test solutions were prepared in dechlorinated municipal water by shaking excess chemical with water for 24 h, filtering the solutions, and diluting aliquots of the filtrate to 3 L in l-gal vessels. The final chemical concentration was at least 5 times below the solubility limit. The solutions were allowed to stand overnight, and the experiments were initiated by the addition of four to eight fish which were starved for 48 h before use. The approximate weights of the fish used were as follows: rainbow trout (Salmo gairdneri), 0.1-0.6 g; bluegill sunfish (Lepomis macrochirus), 0.1-0.5 g; guppy (Poecilia reticulata),0.1-0.4 g. The loading factor ranged between 0.37 and 1.5 g/L and averaged 1.08 g/L. The solutions were not aerated to minimize loss of material through volatilization, but the dissolved oxygen concentration, monitored with a YSI 54A oxygen meter, remained at 60% or more of saturation throughout the experiments. The solutions were sampled initially and then periodically throughout the exposure period which lasted for 2 days. Twelve to 18 samples were taken, with the sampling frequency approximating that shown in Figure 1. The samples (250 pL) were mixed with hexane (1mL) in 2-mL vials which were sealed and shaken vigorously. The hexane was then ana-
0 1984 American Chemical Society
Environ. Sci. Technol., Vol. 18, No. 2, 1984 79
