Environ. Sci. Technol. 1992, 26, 1544-1550
( 5 ) Finkle, B. J. Nature (London) 1965,207, 604-605. (6) Public Data Branch, Office of Toxic Substances, U.S. Environmental Protection Agency, Washington, DC, 1991. (9Sielicki, M.; Focht, D. D.; Martin, J. P. Appl. Environ. Microbiol. 1978, 35, 124-128. (8) Baggi, G.; Boga, M. M.; Catelani, D.; Galli, E.; Treccani, V. Syst. Appl. Microbiol. 1983, 4, 141-147. (9) Hartmans, S.; van der Werf, M. J.; de Bont, J. A. M. Appl. Enuiron. Microbiol. 1990, 56, 1347-1351. (10) GrbiE-GaliE, D.; Churchman-Eisel, N.; MrakoviE, I. J.Appl. Bacteriol. 1990, 69, 247-260. (11) Banerjee, S.; Howard, P. H. Environ. Sci. Technol. 1988, 22, 839-841. (12) Hassett, J. J.; Banwart, W. L. In Reactions and Movement of Organic Chemicals in Soils; Sawhney, B. L., Brown, K., Eds.; Soil Science Society of America: Madison, WI, 1989; pp 31-44.
(13) Environmental Protection Agency. Occurrence of Synthetic Organic Chemicals in Drinking Water, Food, and Air; Office of Drinking Water, U.S. Environmental Protection Agency: Washington, DC, 1987. (14) Anderson, T. A.; Beauchamp, J. J.; Walton, B. T. J. Environ. Qual. 1991, 20, 420-424. (15) Alexander, M. Environ. Sci. Technol. 1985, 18, 106-111. (16) Scow, K. M.; Simkins, S.; Alexander, M. Appl. Environ. Microbiol. 1986, 51, 1028-1035. (17) Rubin, H. E.; Subba-Rao, R. V.; Alexander, M. Appl. Environ. Microbiol. 1982, 43, 1133-1138. Received for review January 29, 1992. Revised manuscript received April 17,1992. Accepted April 20,1992. Support for this research was provided by the Styrene Information and Research Center.
A History of Octachlorodibenzo-p-dioxin, 2,3,7,8-Tetrachlorodibenzofuran, and 3,3',4,4'-Tetrachlorobiphenyl Contamination in Howe Sound, British Columbia Roble W. Macdonald," Waiter J. Cretney, Norman Crewe, and David Paton Institute of Ocean Sciences, P.O. Box 6000, Sidney, British Columbia, V8L 462 Canada --
Six pulp mills using chlorine bleach discharge effluent into the Strait of Georgia, British Columbia. Fisheries were closed around the mills when dioxins and furans were measured in sediments and edible seafood. We report here the first measurements made for a dioxin (OCDD), a furan (2,3,7,8-TCDF),and a PCB (77) on three dated box cores collected from the region. OCDD is widely distributed, first appears in the sediments in 1940, reaches a maximum in 1970, and probably has an atmospheric source. In contrast, 2,3,7,8-TCDF is concentrated near pulp mills and has been accumulating in the sediments since -1965. PCB 77 correlates well with OCDD and is probably supplied from the atmosphere. ii
-
Introduction
P ~ d pmills using chlorine produce dioxins and furans (1, ?,!. British Columbia has 10 mills that discharge chlori-
nated effluent directly to the marine environment, and surface sediments near them are found to be contaminated with organochlorines (3). Two pulp mills are situated on Howe Sound and another four are located on the Strait of Georgia (Figure 1). Howe Sound has long received contaminant inputs ( 4 ) . Since 1899, Cu and Zn have entered the inlet from a mine at Britannia either as tailings or in acid drainage. From -1965 to 1970, a Hg cathode chlor-alkali plant (FMC) disposed -20 kg of Hg/day in effluent forcing closure of shellfkh and groundfish fisheries for 8 yr (5). Due to furan and dioxin contamination, in 1988 (November) harvesting of prawn, shrimp, and crab was curtailed near pulp mills; more extensive closures have followed. Pulp mill effluent has been reviewed as a coastal contaminant (6, 7), but byproduct organochlorines have gone unmentioned. Only recently have we been able to measure these compounds at the ultratrace concentrations which, we are now realizing, are of significance to human health and the ecosystem. For the West Coast there are few data for dioxins or furans, none reported in the open literature (3, 8-10). 1544
Environ. Sci. Technol., Vol. 26, No. 8, 1992
We report here octachlorodibenzo-p-dioxin (OCDD), 2,3,7,8-tetrachlorodibenzofuran (2,3,7,8-TCDF), and 3,3',4,4'-tetrachlorobiphenyl (PCB 77) determinations performed on sediments from three box cores dated by 210Pbgeochronology. We focus on these toxic, planar compounds because they represent the various compound classes and because they represent various expected sources. OCDD is known to have an important atmospheric source (11-13) while 2,3,7,8-TCDF is primarily associated with pulp mills (1-3,14). PCB 77 was measurable by making a small alteration to the dioxin procedure. Such non-ortho-substituted (coplanar) PCBs (15) rank with furans and dioxins in toxicity (16,17), and yet we have few data on their sources and budgets. We attempt to establish the source, the history, the distance of transport, and the magnitude of burdens and fluxes of these three contaminants to the sediments of Howe Sound and the Strait of Georgia. Such information is crucial to understand the environmental role of pulp mills, to design appropriate monitoring strategies, and to predict the effect of remedial action taken by pulp mills. S a m p l i n g and Subsampling M e t h o d s
In December 1990, two box cores (TC-1, HS-1) were collected in Howe Sound (Figure 1)and one was collected from Ballenas Basin (BB-1). Ballenas Basin was chosen partly because previous work has established geochronology (18) and partly to provide a basin-scale backdrop. Upon retrieval of each box core (0.06 m2,0.5 m/s), one wall of the stainless steel liner was lowered in the ship's laboratory to subsample each core with minimal disturbance. Stainless steel tools were cleaned between samples (tap water, distilled water, acetone), and sediment from the outer 5 cm of the box was discarded. Subsamples (I-cm interval for top 10 cm and 2-cm intervals deeper) were split for organochlorines (glass Mason jars with Teflon-lined lids) and other determinations (Whirl-pak bags) and frozen. Mason jars were stringently precleaned (detergent rinse, 4-h soak in 2% RBS, rinse, distilled water
0013-936X/92/0926-1544$03.00/0
0 1992 American Chemical Society
50")
49
125"W
124"
123"
Flgure 1. Cores TC-1 (Thornbrough Channel), HS-1 (Howe Sound), and BB-1 (Ballenas Basin). Locations of the six pulp mills are shown [(l) Port Mellon, (2) Woodfibre].
temperature program was 100-300 "C; 1min initial time, 20 deg/min to 200 "C, and then 3 deg/min to 300 "C with a 30-min final hold. Analytical Methods High-resolution mass spectrometry was used to confirm Organochlorines. Approximately 10 g of wet sediidentifications for three samples per core (VG Model 70s ments was ground in a mortar with Na2S04. Samples and GC/MS). Confirmation criteria and quantitation were a surrogate mixture of furans and dioxins (2 ng of [13based on EPA method 1613. In the sequence of extraction CI2]-2,3,7,8-TCDF,2 ng of [13C12]-2,3,7,8-TCDD,2 ng of and cleanup, one blank is spiked and subsequently ana[ 13C12]-1,2,3,7,8-PCDD, 4 ng of [13C12]-1,2,3,6,7,8-H6CDD, 4 ng of [13C12]-1,2,3,4,6,7,8-H7CDD, 6 ng of [13C12]OCDD) lyzed for every nine samples. Performance standards, which are dioxin/furan spiked sediments, were extracted were then Soxhlet extracted (overnight with -400 mL of and analyzed and were found to fall within f15% of an methylene chloride), rotary evaporated, and reconstituted established amount. in 10 mL of hexane; the sulfur was removed with acidLead-210. 210Pbwas determined by measuring 210Po(19) treated copper filings. Samples to be analyzed for nonusing a 300-mm silicon surface barrier detector with a ortho-substituted PCBs were spiked with the PCB 77 Canberra 8180 MCA. Counting errors were generally less surrogate ( [13C12]-3,3',4,4'-tetrachlorobiphenyl). Three than 10%. Replicate, unlabeled sediment samples were stages of cleanup were then applied: (1) Gel permeation used to verify this error [pooled CV was 5% ( u = 5)]. chromatography (Autoprep 1002A, Analytical BiochemCarbon and Nitrogen. Carbon and nitrogen were istry Laboratories) was employed to remove high molecular determined by following the method of Iperen and Helder weight (lipid) interferences; (2) Sample extracts (post(20) using a Carlo Erba 1106 elemental analyzer standGPC) to be analyzed for dioxins, furans, and non-orthoardized with acetanilide. The mean and standard deviasubstituted PCBs were transferred onto carbon columns tion for boat blanks was for C, 13.1 f 2.1 pg, and for N, (to separate dioxins/furans and PCBs from other residual -2.54 f 0.29 (n - 13). For nine replicates run among the chlorinated organics); and (3) Acidic Biosil/alumina colsamples we found the pooled standard deviation to be for umns were used to separate dioxins, furans, and PCB 77 C, 0.~073%(range 1.4113.24%), and for N, 0.0084% (range from the other non-ortho-substituted PCBs. Samples to 0.15-0.26 % ). be analyzed only for dioxins and furans were added to acidic Biosil/alumina and then onto carbon columns. The Sediment Dating and Mixing Model extracts were evaporated to dryness and dissolved in 21Pbwas used to construct a time sequence for the three toluene containing the internal standard [13C12]-TCDD. box cores; the method and its pitfalls are thoroughly reSamples to be analyzed for PCBs were evaporated to viewed by Robbins (21). Surface mixing (bioturbation) is dryness and dissolved in toluene containing anthracene-dlo. probably the most important consideration when atMeasurement by low-resolution GC/MS was performed tempting to relate depth in a core to age. In this regard, with a Hewlett Packard 5890 gas chromatograph with an H P 5970 mass selective detector (800 resolution) using the limit to interpretation of a contaminant profile can be selected-ion monitoring at a rate of 1 scan/s. Chromatoexpressed as the intrinsic time resolution [t,, depth of the graphic separation was achieved on a 60-m, 0.25-mm-i.d. mixed layer divided by the sedimentation rate (22)]. Surface mixing also drives contaminants into deeper sedDB-5 fused-silica column with helium carrier gas. The rinse, and baked overnight at 350 "C).
Environ. Sci. Technol., Vol. 26, No. 8, 1992
1545
LN (EXCESS LEAD-910)
80
-
0 5 1.0 1 5 2 0 2 5 3 0 0 0 0 5 1 0 1 5 2 0 2 5 0 0
v---
05
10
20
15
25
0 0
C 0 0
0
6 0
24
Flgure 2. Excess '"Pb profiles and linear least squares fits for the box cores taken at B E 1 and HS-1. For TC-1, lines fitted to the data were derived from the two-layer advection diffuslon model.
POROSITY 0.80
0.85
% CARBON
a
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HS-1 TC-1
Flgure 3. Porosity, percent carbon, and C/N ratio for the three cores plotted as a function of depth in the core.
iments, which, if not accounted for, will produce a misleading contaminant history (23). Bioturbation is often modeled by considering the sediments to comprise two zones; a surface mixed layer (SML) and a deeper layer where the sediments no longer mix (22,24-2-8). For BB-1, 0
100 200 300 400 500
1
the 21Tb(Figure 2), C (Figure 3), and contaminant profiles (Figure 3) suggest that mixing has been relatively unimportant. This interpretation is supported by more detailed zloPbprofiles taken at nearby sites (18)and by the safety factor that the rapid sedimentation at BB-1 would tend to produce a short t, ( h) A is assumed to be zero. The influence of compaction can be removed by expressing depth as total mass accumulation (g/cm2): r = p,(l - dw, (2) where p, is the density of the solids, 4 the porosity, and
0 10 20 30 , 40, 50 , ~~
I,
,%;:2
6 ; , 8,O ,lr
1990
0
1970
I:
0
_I 1950
1930
HS - 1 Flgure 4. OCDD, 2,3,7,&TCDF, and PCB 77 sediments profiles at (a) Ballenas Basin and (b) Howe Sound (HS-1). Where detection limits constrain data interpretationthey are shown as vertical bars. 1546 Envlron. Sci. Technol., Voi. 26, No. 8, 1992
Table I. Sedimentation Parameters for the Howe Sound and Strait of Georgia Cores"
location water depth, m sedimentation rate (WAcm/yr g cm2 yr-' SML depth (h), cm SML diffusion (A), cm2/yr zloPb sedimenting, dpm/g surface flux, dpm cm-2 yr-' supported, dpm/g
BB-1
HS-1
TC-1
49'13.0' N 123'35.0' W 377
49'27.1' N 123'16.5' W 245
49'32.1' N 123'25.7' W 230
1.4 f 0.2 0.64 f 0.09
0.78 f 0.11 0.36 f 0.04
0.46 f 0.11 0.20 f 0.05 9 4
13 & 0.9 8.3 f 0.8 0.9 f 0.2
9.5 f 1.0 3.4 f 0.6 1.2 f 0.2
"Cores were collected between December 5 and 6, 1990. *Calculated as x = x,(l laver.
r the sedimentation rate. Analytical solutions to eq 1are provided in Lavelle et al. (28). The accuracy of zloPb dating derived from the two-layer model depends on the assumptions [e.g., constant sedimentation rate, no diffusive loss of 210Pb,no mixing below the SML, and sampling intervals small relative to the total amount of sediment accumulated during the dating period (24)j. In these circumstances, excess zloPb below the SML follows the relationship (3) If there has been some bioturbation, using eq 3 will overestimate the sedimentation rate (21, 29). We can evaluate the importance of this bias to our cores by solving the advection-diffusion equation. When 210Pbactivity has exponential decrease with depth, the sedimentation velocity, w,, may be expressed as (27,29) W, = ( X / a ) - Aa (4) where a-l is the decay length (cm). In the case of the three cores reported here, if we assume A = 0 when in fact it has a small value of -1 cm2/yr (3 X lo-* cm2/s), we would overestimate the slowest sedimentation rate (0.46 cm/ yr) by -10% and the fastest sedimentation rate (1.4 cm/yr) by -2%. Sediment profiles for the various contaminants, which are discussed below, lead us to believe that where we have applied eq 3 the diffusivities are indeed less than 1 cm2/yr and probably closer to 0.1 cm2/yr. The sedimentation rates in Table I were determined from linear least squares fits to the data expressed in terms of mass accumulation. In the case of TC-1, where the SML is of major importance, data from deeper than -9 cm (3 g/cm2) were used for the calculation. The sedimentation parameters determined for the three box cores fall in the range of previous regional measurements (18,24,27). Results and Discussion Although the three cores may contain similar records for widely distributed sources, this is not likely to be true for point sources; for example, all three cores have increasing carbon and C/N ratios toward their surfaces, but it is especially evident at TC-1. An increase in C/N ratio implies added terrestrial carbon, the major regional source being pulp mills (18). In 1985, the Strait of Georgia pulp mills collectively discharged 130OOO kg of solids/day in their effluent (30). Using 6.2 and 90 for the marine and terrestrial C/N ratios, respectively (18),terrestrial C accounts for
