Environ. Sci. Technol. 1997, 31, 1483-1488
Distribution and Characterization of Polychlorinated Biphenyl Congeners in Soil and Sediments from a Superfund Site Contaminated with Aroclor 1268 K U R U N T H A C H A L A M K A N N A N , * ,† KEITH A. MARUYA,† AND SHINSUKE TANABE‡ Skidaway Institute of Oceanography, 10 Ocean Science Circle, Savannah, Georgia 31411, and Department of Environment Conservation, Ehime University, Tarumi 3-5-7, Matsuyama 790, Japan
The use of Aroclor 1268 at a former chlor-alkali plant in coastal Georgia (United States) has resulted in extensive contamination of soils on-site and also of sediments in the adjacent brackish marsh. The concentrations of total polychlorinated biphenyls (PCBs) in soil and marsh sediments ranged between 9.6 and 567 µg/g dry wt. A nearly 100fold decline in total PCBs with distance away from the site suggests a high attenuation of PCBs by the marsh environment. Isomer-specific analysis of PCBs in Aroclor 1268 and in soils and sediments from the site revealed that a comparable proportion of octa- and nonachlorobiphenyl congeners, characteristic of the source, were present. The distribution of PCBs in marsh sediments was similar to that in Aroclor 1268, which suggests a high degree of stability of this PCB formulation in this environment. The estimated 2,3,7,8-TCDD equivalents of coplanar PCBs in soil and sediments were between 1.6 and 28.6 ng/g dry wt and also declined by 2 orders of magnitude along the contamination gradient; the non-ortho congener, IUPAC No. 126, contributed greater than 50% of the toxic equivalents in these samples.
Introduction A former chlor-alkali plant in coastal (southeastern) Georgia (United States) is situated on a few hundred acres and borders a brackish tidal marsh dominated by emergent grasses (Spartina sp. and Juncus sp.). For over 75 years, several industrial ventures, mainly chemical in nature, occupied this site and disposed wastes on-site and also into the adjacent marsh. The chlor-alkali plant was established on-site in 1955 and was operated until 1994, when it was designated as a Superfund site. Process wastes were discharged into large holding pits near the top of the marsh and also directly into Purvis Creek (Figure 1). As a result of multi-industrial operations, the site and the adjacent brackish marsh have been severely contaminated by metals (mercury, lead, chromium, and zinc) and organics (PCBs, PAHs, and phenolic compounds). Recently, the U.S. Environmental Protection Agency (EPA) conducted surveys and confirmed the presence * Corresponding author present address: 201B Pesticide Research Center, Michigan State University, East Lansing, MI 48824. Fax: 517353-5598; e-mail:
[email protected]. † Skidaway Institute of Oceanography. ‡ Ehime University.
S0013-936X(96)00721-3 CCC: $14.00
1997 American Chemical Society
FIGURE 1. Map of the LCP Chemicals Superfund site in Glynn County near the city of Brunswick, GA, showing soil and sediment sampling locations (ES, MSL, MSR, and CCS represent excavation soil, marsh left- and right-transect sediments, and tidal creek sediment, respectively). of PCBs in sediment and biota collected on-site from the adjacent marsh and from nearby tidal creeks of the Turtle/ Brunswick River Estuary (1, 2). In addition, the toxicity of porewaters extracted from sediments in the nearby tidal creeks was attributed to PCBs and methylmercury (3). Aroclor 1268, a highly chlorinated PCB formulation, was applied to electrical equipment employed in the chlor-alkali process at the LCP site. It is not known exactly how long and how much Aroclor 1268 was used at this site, but the quantities are considered to be substantial on the basis of contamination levels (1, 2). The existing literature suggests that Aroclor 1268 was produced for use as a plasticizer in rubbers and synthetic resins and as wax extenders (4). Aroclor 1268 is a crystalline white powder in contrast to several other commercial PCB mixtures, which are viscous liquids or sticky resins (4). Although efforts have been made to understand the chemistry and ecotoxicology of major PCB formulations such as Aroclors 1016, 1242, 1254, and 1260 and their overseas equivalent preparations, little is known about the environmental fate and toxic potential of Aroclor 1268. In this paper, we present data from congener-specific analysis of PCBs in soil and sediments along a contamination gradient away from the site in order to characterize their distribution and potential for toxic effects and remediation. We also examined the composition of an Aroclor 1268 preparation to evaluate its toxic potential.
Materials and Methods Collection of Samples. Surficial sediments (0-5 cm) were collected from three intertidal locations during low tidestwo of them in the contaminated marsh [one each from left- (MSL) and right- (MSR) transect]sand the third from a tidal creek (CCS), which empties into Purvis Creek (Figure 1). In addition, a grab sample was taken from soil excavated (ES) from the site. This excavation is a part of the on-site remediation effort currently being administered by EPA. Soil and sediments from several locations at each of the four sites were combined to obtain a representative mixture. Samples were collected with a stainless steel scoop pre-rinsed with acetone and
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hexane, homogenized, immediately placed in I-Chem glass jars and transported to the laboratory in ice-filled portable containers, and stored at -20 °C prior to analysis. Sediments were freeze-dried and passed through a 500-mm sieve before chemical analysis. Isomer-Specific Analysis of PCBs. Soil and sediment samples (5-15 g dry wt) were refluxed in 100 mL of 1 N KOHethanol solution for 1 h following the method described elsewhere (5, 6). PCBs extracted into ethanol were transferred to 100 mL of hexane by shaking in a separatory funnel. The concentrated hexane layer was cleaned up on 1.5 g of silica gel (Wakogel S-1; Wako Pure Chemical Industries Ltd., Japan) packed in a glass column (10 mm i.d. × 20 cm length). PCBs were eluted with 200 mL of hexane at an elution rate of one drop/s. The eluate was concentrated to 6 mL in a KudernaDanish (K-D) concentrator. Half of the extract was treated with 5% fuming sulfuric acid, washed with hexane-washed water, and analyzed for ortho-chlorine-substituted PCBs including mono- and di-ortho congeners, using GC-ECD and GC-MS. The remaining 3 mL of the hexane extract was passed through a glass column (5 mm i.d.) packed with 125 mg of activated carbon (Wako Pure Chemical Industries Ltd., Japan) for separation of the non-ortho congeners, 3,3′,4,4′T4CB (IUPAC No. 77), 3,3′,4,4′,5-P5CB (IUPAC No. 126), and 3,3′,4,4′,5,5′-H6CB (IUPAC No. 169), according to Tanabe et al. (7). An initial eluate of 100 mL of 20% dichloromethane in hexane (v/v) containing PCBs with ortho-substituted chlorines and biogenic substances which interfere with nonortho congeners was discarded. A second fraction eluted with 100 mL of benzene:ethyl acetate (50:50) containing nonortho-chlorine-substituted PCBs was microconcentrated, and residues were extracted into 5 mL of hexane. This hexane extract was acid treated, rinsed in hexane-washed water, and analyzed by GC-ECD. Values obtained by GC-ECD analysis were confirmed by GC-MS. A Hewlett Packard 5890 Series II gas chromatograph (GC) equipped with a moving needle type injection port (splitless and solvent-cut mode) and a 63Ni electron capture detector was used for the determination of total PCBs. A fused silica capillary column (30 m × 0.25 mm i.d.) coated with DB-1 (100% dimethyl polysiloxane) having a film thickness of 0.25 µm (J&W Scientific, Folsom, CA) was used. The column temperature was programmed from 60 °C (1 min hold) to 160 °C at a rate of 20 °C/min, held for 10 min, and then ramped at a rate of 2 °C/min to 260 °C with a final hold time of 20 min. The injector and detector temperatures were maintained at 260 and 280 °C, respectively. Helium and nitrogen were used as the carrier and makeup gases, respectively. Concentrations of individually resolved PCB peaks were summed to obtain the total PCB concentration. For the isomer-specific analysis of PCBs, including nonortho congeners, a Hewlett Packard 5890 GC coupled with a 5971 mass selective detector (MSD) equipped with a HPG1034C MS Chem Station and operating at an electron impact energy of 70 eV was used. A similar column (DB-1) as mentioned above was employed. The oven temperature was programmed from 70 °C (1 min hold) to 160 °C (10 min hold) at a rate of 20 °C/min and then to a final temperature of 265 °C at a rate of 2 °C/min with a 15-min hold. Injector and ion-source (transfer line) temperatures were kept at 250 and 280 °C, respectively. Nitrogen was the carrier gas. PCB homologs were determined by selective ion monitoring (SIM) at m/z 256, 290, 324, 358, 392, 428, 460, and 494 for tri-, tetra-, penta-, hexa-, hepta-, octa-, nona-, and decachlorobiphenyls, respectively. The recoveries of nona- and decachlorobiphenyl congeners using the alkali digestion procedure were typically nonquantitative (
