Arch Environ Contam Toxicol (2008) 54:20–30 DOI 10.1007/s00244-007-9006-4
Polychlorinated Dibenzo-p-Dioxins, Dibenzofurans, and DioxinLike Polychlorinated Biphenyls in Sediment and Mussel Samples from Kentucky Lake, USA Bommanna G. Loganathan Æ Kurunthachalam Senthil Kumar Æ Shigeki Masunaga Æ Kenneth S. Sajwan
Received: 6 December 2006 / Accepted: 12 June 2007 / Published online: 6 September 2007 Springer Science+Business Media, LLC 2007
Abstract Sediment and mussel tissues from the Kentucky Dam Tailwater (KDTW) and Ledbetter Embayment (LE) of Kentucky Lake, Kentucky, USA, were analyzed to examine the presence of 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and non-, mono-, and di-orthochlorine-substituted polychlorinated biphenyls. Concentrations of target compounds varied with locations and sample matrices. In general, KDTW sediment samples contained slightly higher amounts of PCDD/DFs (average: 1100, range: 120-2400) than the LE sediments (average: 920, range: 580-1300) on a pg/g dry wt (dw) basis. Dioxinlike PCBs in KDTW were (average: 550, range: 70–2,000) higher than in LE (average: 320, range: 44-1000) on a ng/g dw basis. In contrast, mussel tissues had greater concentrations of PCDD/DFs in LE (average: 6500, range: 2200– 13,000) than in KDTW (average: 3500, range: 2500-4800). Dioxin-like PCBs were slightly higher in KDTW (average: 76, range: 18–100) than in LE (average: 49, range: 24–96) on a ng/g fat wt basis. Biota sediment accumulation factors (BSAFs) were calculated using tissue concentrations and
B. G. Loganathan Department of Chemistry and Center for Reservoir Research, Murray State University, 456 Blackburn Science Building, Murray, Kentucky 42071-3346, USA K. S. Kumar S. Masunaga Graduate School of Environment and Information Sciences, Yokohama National University, 79-7 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan K. S. Kumar (&) K. S. Sajwan Department of Natural Sciences and Mathematics, Savannah State University, 3219 College Street, P.O. Box 20600, Savannah, Georgia 31404, USA e-mail:
[email protected]
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sediment concentrations based on dry weight. PCDD/DFs BSAF was in the range of 0.21-25 in LE and 0.093-13 in KDTW. 1,2,3,7,8,9-HxCDF in LE and 2,3,7,8-TCDF in KDTW had a greater BSAF, while BSAF for dioxin-like PCBs ranged from 0.84 to 13 in LE and from 2.3 to 12 in KDTW in which PCB-169 had the greatest BSAF in LE and PCB-167 in KDTW. Toxic equivalency (TEQ) was greatest in mussel from LE (mean: 193 pgTEQ/g fat wt) followed by mussel from KDTW (32 pgTEQ/g fat wt), sediment in KDTW (13 pgTEQ/g dry wt), and sediment in LE (7.6 pgTEQ/g dry wt). In general, PCDD/DF had a greater contribution to toxicity in mussels, while dioxinlike PCBs had a greater contribution to toxicity in sediment at both locations.
Polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and dioxin-like PCB congeners are among the most toxic chemicals for a variety of animal species, including humans (Schecter et al. 1994a, b; Loganathan et al. 1995; Senthil Kumar et al. 2001a, 2002a, b, c, 2003a, b, c, d; Kannan et al. 2003). PCDDs and PCDFs are byproducts in the production of PCBs, polychlorinated naphthalenes, and chlorinated phenols (Kannan et al. 1997, 1998). These chemicals are widely dispersed in the environment (Schecter 1994) and the residues of these chemicals have been reported in air, water, soil, sediment, and aquatic and terrestrial organisms, including humans (Smith et al. 1984; Rappe et al. 1987; Patterson et al. 1994; Senthil Kumar et al. 2001a, b, 2002a, b, c, 2003a, 2003b, 2003c, 2003d, 2005; Kannan et al. 2003; Takasuga et al. 2004a). Because of the persistent and bioaccumulative properties of these compounds, animals that belong to higher trophic levels receive the largest amount of these contaminants, and these
Arch Environ Contam Toxicol (2008) 54:20–30
21
Fig. 1 Map showing sampling locations (the closed circles and a star show sampling sites)
Ohio R.
Tennessee R.
Paducah
USA
KE NT
Tailwater
UC KY LA
IN
KE
N
W
E
ILLINOIS KENTUCKY
S
Ledb ett er E mba ymen t MO
TENNESSEE AK
compounds have a variety of effects on health, including body weight loss, thymic atrophy, dermal disorder, hepatic damage, teratogenesis, reproductive toxicity, and immunotoxicity in some animals, and humans (Safe, 1990, 1991, 2000; Safe et al. 1985; Kennedy et al. 1996). To better understand the current status of dioxin and dioxin-like chemicals pollution, sediment and mussel samples were analyzed. The data will provide insight into details such as sources, levels, and their effects on a regional basis. The proposed major sources of dioxins are the combustion of various materials, the production and use of chlorinated organic compounds, and the bleaching of pulp and paper (Senthil Kumar et al. 1999, 2001a; Masunaga et al. 2001a). However, sources of dioxin contamination varied depending on location. For example, the historical increase of dioxin in the Great Lakes coincided with the production and disposal of chlorinated organic compounds (Giesy et al. 1999). Coal, wood, and peat were the major sources of dioxin from 1882 to 1962, and pentachlorophenol (PCP) was the main contributor from 1970 to 1985 in the Baltic Sea (Kjeller et al. 1991). The presence of PCDD/DFs and dioxin-like PCBs in sediment and selected biota has been of concern because of their bioaccumulation and potential for toxicity to highertrophic-level animals (Giesy et al. 1994). High concentrations of organic contaminants such as PCBs and PCDD/ DFs have impacted the health of sediment-dwelling organisms, especially mussels, and benthic biota, including fish (Kannan et al. 1998, 2001; Giesy et al. 1999; Sakurai et al. 2000; Yamashita et al. 2000; Masunaga et al. 2001a). For instance, in several regions some fish species collected in contaminated areas have shown a higher prevalence of morphologic abnormalities such as lip and skin lesions and physiologic effects, and liver neoplasms than those
10
0 10 Scale of km
20
collected from relatively less polluted sites (Maccubbin and Black 1990; Maccubbin and Ersing 1991; Baumann 1998; Baumann et al. 1996; Leadley et al. 1998). Westernmost Kentucky is endowed with the highest density of major rivers in the world and a variety of industries and state-of-the-art agricultural operations. In particular, the Kentucky Dam Tailwater (KDTW) suffered from the stress of pollutant loading from a variety of sources, including hazardous waste from manufacturing facilities and abandoned dumps, sewage, dredged materials, and heavy agricultural activities where organic pesticides are heavily used (USEPA 2003). Nevertheless, little is known about the levels of highly toxic dioxins, furans, and dioxin-like polychlorinated biphenyls in sediments and biota in this watershed. The objective of this study was to determine the concentrations of 2,3,7,8chlorine-substituted PCDDs, PCDFs, and non-, mono, and di-ortho-chlorine-substituted PCBs in surface sediment and mussel tissues collected from selected locations of the Kentucky Lake, the Ledbetter Embayment (LE), and KDTW. In addition, biota sediment accumulation factors (BSAFs) were calculated based on the dry weight data of sediment and mussel samples. Toxic equivalencies (TEQ) were estimated by using WHO TEFs proposed in 1998.
Materials and Methods Sampling Locations and Samples Kentucky Lake is one of the major man-made lakes in the U.S. Figure 1 is a map of westernmost Kentucky, the Kentucky Lake watershed, and the sediment and mussel sampling locations. Ledbetter Embayment (LE) of
123
22 Table 1 Details of sediment and mussel samples collected from Kentucky Dam Tailwater and Ledbetter embayment of Kentucky Lake, USA
Arch Environ Contam Toxicol (2008) 54:20–30
Ledbetter Embayment
Kentucky Dam Tailwater
Sample No.
Sample ID
Dry weight (g)
Sample No.
Sample ID.
64
1-SLE
27
70
TR03BFCS5
24
65
3-SLE
25
71
TR30CYM1S3
23
66
1-DLE
27
72
TR03BFGS8
26
67
2-ALEWU
25
74
TR03I24S9
22
68
3-BLECU
26
75
TR03E1FS6a
23
73
2-DLE
26
Sample No. Sample ID
Dry weight (g)
Age (yr) Pooled (n)a Dry wt (g) Wet wt (g) Moisture (%) Fat (%)
Ledbetter Embayment 106
KL01072EM2
7.0
6
4.4
42
89
0.48
107
KL01072EM3
9–12
5
4.8
53
91
0.11
114 111
KL01072EM6 LB02214M7
11–12 11–16
5 5
4.6 4.7
73 54
94 91
0.25 0.30
115
LB02214M6
9.0
6
4.5
63
93
0.26
117
LB01124M1
6.0
1
2.6
47
95
0.23 0.39
Kentucky Dam Tailwater
a
n denotes number of individuals of different mussel species
109
TR03ELFM28 10–11
5
4.6
41
89
110
TR03APM14
11–12
1
4.2
56
92
0.36
112
TR03124M7
30
1
4.5
46
90
0.31
113
TR03ELFM25 12–14
4
4.4
59
93
0.24
116
TR03APM23
4
3.5
36
90
0.34
10–12
Kentucky Lake is considered relatively less polluted, whereas Kentucky Dam Tailwater (KDTW) receives industrial wastewater from several industries (e.g., chemical, metallurgical); it is located in the Calvert City Industrial Complex. Selected locations, including LE and KDTW, were sampled for sediments and freshwater mussels during 1999 and 2000. Surface sediment (0-5 cm) samples were collected using the PONAR grab sampler. The organic matter content and particulate size of the sediment samples were more or less similar (data not shown). The mussels were collected by SCUBA diving on the same day after sediment sampling. The mussels were identified, their length, height, and width were measured, and their wet weight and age were determined (Table 1). The mussel species collected and analyzed included mapleleaf (Quadrula quadrula), threeridge (Amblema plicata), ebonyshell (Fusconaia ebena), and washboard (Megalonaias nervosa).
Chemical Analysis Sediment and mussel samples were freeze-dried, and the moisture content was measured and Soxhlet-extracted using methylene chloride for 16 h. Details of the analytical procedures have been reported previously (Senthil Kumar et al.
123
2001a, 2002a, b, c, 2003a, b, c, d, 2005). Briefly, after extraction, samples were concentrated using a KudernaDanish (K-D) concentrator to 10 ml and the solvent was transferred to n-hexane. The fat content from mussel tissues was determined gravimetrically from an aliquot of the extract. Seventeen 13C-labeled tetra-, penta-, hexa-, hepta-, and octa-CDD and CDF congeners substituted at the 2, 3, 7, 8 positions, and dioxin-like PCBs (IUPAC or CB Nos. 81, 77, 126, 169, 105, 114, 118, 123, 156, 157, 167, 189, 170, and 180) were spiked into hexane extracts prior to sulfuric acid treatment. The hexane layer was rinsed two times with hexane-washed water and dried by passing through anhydrous sodium sulfate in a glass funnel. The solution was concentrated to 2 ml and sequentially subjected to silica gel, alumina, and silica gel impregnated activated carbon column. In the case of sediments, sulfur was removed by passing through copper pellets in a column before separation. The detailed sediment analysis procedure was reported earlier (Masunaga et al. 2001a). Extracts were passed through a silica gel-packed glass column (Wakogel, silica gel 60, 2 g) and eluted with 130 ml of hexane, which contained PCDD/DFs and dioxin-like PCBs. The hexane extract was further K-D concentrated and passed through an alumina column (Merck-Alumina oxide, activity grade 1) and eluted with 30 ml of 2% dichloromethane as a first fraction, which contained several ortho-substituted PCBs.
Arch Environ Contam Toxicol (2008) 54:20–30
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Table 2 Concentrations of PCDD/DFs in sediment (pg/g dry wt) and mussel (pg/g fat wt) from Kentucky Dam Tailwater and Ledbetter embayment of Kentucky Lake Sediment
Mussel
Location
Ledbetter Embayment (n = 6)
Fat (%)
0.113 0.303 0.477 0.237 0.326 0.389 Minimum Mean Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean Maximum
2,3,7,8-D
0.03
0.04
0.04
0.01
0.04
0.08
<0.3
3.8
21
<0.3
9.1
40
1,2,3,7,8-D
0.05
0.10
0.19
0.01
0.09
0.19
6.1
73
270
<0.3
7.4
12
1,2,3,4,7,8-D
0.14
0.28
0.46
0.03
0.29
0.51
<0.3
65
240
<0.3
1.4
6.2
1,2,3,6,7,8-D
0.26
0.59
1.3
0.03
0.62
1.3
<0.3
73
240
<0.3
5.5
16
1,2,3,7,8,9-D
0.06
0.11
0.16
0.03
0.13
0.28
<0.3
9.1
29
<0.3
0.78
1.7
1,2,3,4,6,7,8-D 13
26
44
2.4
27
49
140
310
630
120
140
180
OCDD
560
880
1200
120
1000
1900
2100
5400
9700
2300
2800
3612
2,3,7,8-F
0.09
0.16
0.30
0.03
0.34
1.0
<0.3
55
190
35
77
158
1,2,3,7,8-F
<0.01
0.06
0.22
<0.01
0.42
1.7
<0.3
39
180
<0.3
5.2
25
2,3,4,7,8-F 1,2,3,4,7,8-F
0.03 0.06
0.08 0.27
0.21 0.87
0.03 0.03
0.12 1.7
0.40 6.8
<0.3 <0.3
69 53
270 180
9.4 <0.3
13.8 5.6
17 27
1,2,3,6,7,8-F
0.05
0.14
0.39
0.03
0.52
2.0
<0.3
48
160
<0.3
6.8
18
2,3,4,6,7,8-F
0.04
0.11
0.29
0.03
0.16
0.45
<0.3
78
300
<0.3
5.2
14
1,2,3,7,8,9-F
0.01
0.03
0.08
0.01
0.08
0.31
<0.3
42
190
<0.3
3.2
5.5
2.0
5.6
0.12
9.2
38
<0.3
57
180
8.2
60.5
111
1,2,3,4,6,7,8-F 0.61
Tailwater (n = 5)
Ledbetter Embayment (n = 6)
Tailwater (n = 5)
1,2,3,4,7,8,9-F 0.05
0.13
0.31
0.03
1.2
5.0
<0.3
48
200
<0.3
13.5
38
OCDF
1.2
3.0
5.8
0.36
70
311
<0.3
120
400
<0.3
291
492
PCDDs
570
910
1300
120
1000
2000
2200
5900
11000
2400
3000
3900
PCDFs
2.2
6.0
14
0.63
84
370
<0.3
600
2300
53
480
910
PCDD/DFs
580
920
1300
120
1100
2400
2200
6500
13000
2500
3500
4800
The second fraction eluted with 50% of 30 ml of dichloromethane in hexane containing PCDD/DFs and some dioxin-like PCBs, which was purged under a gentle stream of nitrogen to near dryness and passed through a silica gelimpregnated activated carbon column (0.5 g) to further separate mono- and di-ortho dioxin-like PCBs from nonortho dioxin-like PCBs and PCDD/DFs. The first fraction eluted with 25% dichloromethane in hexane containing mono- and di-ortho PCBs. The second fraction eluted with 250 ml of toluene containing non-ortho PCBs and PCDD/ DFs, which were concentrated and analyzed by high-resolution gas chromatography interfaced with high-resolution mass spectrometry (HRGC-HRMS). The procedural blanks for sediment sample (n = 1) and mussel tissues (n = 1) also were analyzed. Only OCDDs were found at 0.5 pg/g dry wt in both blanks; however, the values were not corrected for blank concentrations.
Identification and Quantification Identification and quantification of PCDD/DFs and dioxinlike PCBs were performed by a high-resolution gas
chromatography (HRGC) (Hewlett Packard 6890 Series) coupled with a high-resolution mass spectrometry (HRMS) (Micromass Autospec Ultima). The HRMS was operated in electron-impact mode and in the selected ion monitoring (SIM) mode at a resolution of R > 10,000 (10% valley). Separation was achieved using a DB-5 (J&W Scientific; 0.25 mm i.d. · 60 m length) and a DB-17 column (J&W Scientific; 0.25 mm i.d. · 60 m length). The oven temperature of the DB-5 and DB-17 columns was programmed from an initial temperature of 160C to a final temperature of 310C (total run time: 60 min) and from an initial temperature of 160C to a final temperature of 280C (total running time: 70 min), respectively. Before injection, 13C-labeled 1,2,3,4-TeCDD and 1,2,3,7,8,9-HxCDD were added for instrumental recovery estimation. Mean (and range) recoveries of spiked internal standards through the entire analytical procedure were 60% and 85%, respectively, to sediments (range: 51-64) and mussel tissues (range: 69-92). The concentrations were expressed as pg/g dry wt (sediment) and pg/g fat wt (mussel) for PCDD/DFs and TEQs and as ng/ g dry wt (sediment) and ng/g fat wt (mussel) for dioxin-like PCBs. Statistical analysis was performed using SPSS software 2005 modified version (SPSS Inc., Chicago, IL).
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Arch Environ Contam Toxicol (2008) 54:20–30
OctaH e p ta -
Tetra-
PCDD
Penta- HexaPCDF
75 74 72 71
Sediment
70 73 68
Sample Number
67 66 65 64 116 113 112
Mussel
11 0 109 117 11 5 111 114 107 106
0
50 Percentage Contribution (%)
100 0
50 Percentage Contribution (%)
100
Fig. 2 Homolog pattern of PCDD/DFs in individual sediment and mussel samples from Kentucky Lake
Results and Discussion PCDD/Fs Concentrations of PCDD/DFs in sediment from LE and KDTW were 920 (range: 580-1300) and 1100 (range: 1202400) pg/g dry wt (dw), respectively (Table 2). Maximum PCDD/DFs were noted in sediment from KDTW rather than from LE; however, no statistical difference (P > 0.05) was noted between the locations. Mussel tissue showed a contrast pattern with greater concentrations of PCDD/DF at LE (mean: 6500; range: 2200-13,000) than at KDTW (mean: 3500; range: 2500-4800). These results were statistically significant at P = 0.01%. Lipid normalized mean concentrations of PCDD/DFs in mussel tissues were 6500 and 3500 pg/g fat wt in LE and KDTW, respectively. A careful look at PCDD and PCDF levels in mussel samples revealed that concentrations of 2,3,7,8-D, 2,3,7,8-F, and OCDF were higher in samples from KDTW, while the higher PCDD + PCDF levels found in mussel samples from LE were the result of higher levels of high-chlorinated
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PCDD. Slightly higher PCDF proportions in mussel tissue from KDTW probably are the result of formation from an industrial source (Takasuga et al. 2004b). Contamination variation between sediment and mussel can be explained by the bioaccumulation efficiency of mussel. Furthermore, age and species differences should not be neglected. 1,2,3,4,6,7,8-HpCDD and OCDD accumulated considerably in sediment and mussel tissues (Table 2 and Fig. 2). Both congeners alone contributed 74.2-100% in sediment and 77-99.9% in mussel tissues. In particular, OCDD accumulated greatly in all the analyzed samples with the highest percentage contribution. Consequently, PCDD homologs were several orders of magnitude greater than PCDF homologs in all samples (Table 2 and Fig. 2). With greater accumulation levels, the ratio of PCDDs to PCDFs ranged from 3.3 to 82.4 in sediment, and from 3 to 97.8 in mussel tissues. Interestingly, KDTW samples TR03BFCS5 (sediment No. 70) and TR03ELFM28 (mussel No. 109) respectively showed a minimum ratio. Several reports documented an increased amount of HpCDD and OCDD in soil, sediment, crab, and shellfish (Kannan et al. 1998,
Arch Environ Contam Toxicol (2008) 54:20–30 3000
6000 PCDD/DFs Concentration in mussel (pg/g fat wt.)
Fig. 3 Correlation of PCDD/ DFs and dioxin-like PCBs in between sediment and mussel tissue
25
y = 6.0728x + 58.819 R2 = 0.9993
5000 4000
y = 2.7861x + 20.446 2 R = 0. 9 981
2500 2000
3000
1500
2000
1000
1000
500 LE
0 500
0
KDTR
0
1000
0
Dioxin-like PCBs Concentration in mussel (ng/g fat wt.)
25
y = 0 . 1 6 2 4 x - 0 . 1 41 R2 = 0.9263
20
500
1000
1500
PCDD/DFs C o n c e n t r a t i o n in se d i m e n t ( p g / g d r y w t . )
PCDD/DFs Con c e n t r a t i on i n s ed i m ent (p g / g d ry w t . )
35 y = 0.1253x + 0.5255 R2 = 0.8793
30 25
15
20
10
15 10
5
5 LE
0 0
50
100
150
D io xi n-l ik e PC Bs Concentration in sediment (ng/g dry wt.)
2001; Giesy et al. 1999; Sakurai et al. 2000; Yamashita et al. 2000; Masunaga et al. 2001a). Concentrations of PCDD/DFs in sediment in this study were lower than those of rural areas of Japan and coastal Georgia in the USA, but were several times higher than those in the Detroit River in the USA and similar to Tokyo Bay in Japan. Because our study first reported PCDD/DF concentrations in different species of mussel tissues, direct comparisons cannot be made. However, when compared to Great Lakes salmon and trout tissues (Giesy et al. 1999), in our study the levels were several times higher. Sedimentdwelling lower trophic animals have less metabolic capacity than gill-breathing fish and higher-trophic–level animals (Riisgard and Larsen 2001). This probably suggested higher levels of PCDD/DFs in mussel tissues than in fish from the Great Lakes. Similarly, shellfish and crab accumulated greater PCDD/DFs than rockfish, flounder, bartailed flathead, stingray, sea bass, and gray mullet (Sakurai et al. 2000). PCDFs, HpCDF and OCDF were the major contributors to the total PCDFs (Fig. 2). The predominance of OCDD in sediment samples collected from all over the world suggested atmospheric deposition (Czuczwa and Hites 1986). Similarly, slightly higher levels of HpCDF and OCDF suggested the impact of industry. Less chlorinated PCDDs and PCDFs were proposed to be more trapped and bind to accumulated vegetation rather than deposit onto the soil and sediment (Horstman et al. 1997). The presence of HxCDDs in sediment samples enabled the use of pentachlorophenol (PCP) for agriculture near Kentucky Lake. Masunaga et al. (2001b) reported
KDTR
0 0
100
200
300
D i o x in - l ik e PC B s Concentration in sediment (ng/g dry wt.)
higher concentrations of PCDD/DFs and dioxin-like PCBs from agrochemical impurities. Comparatively higher concentrations of PCDD/DFs in LE mussel would have originated not only from atmospheric deposition, but also from impurities of agrochemicals used in and around LE. Besides, the presence of TCDD, TCDF, and 2,3,4,7,8PeCDF most samples indicated pulp- and paper-related sources (Loganathan et al. 1995). The correlation between sediment and mussel was significant (r2 = 0.9993 in LE and r2 = 0.9981 in KDTW) (Fig. 3) for PCDD/DFs. This was because mussel bioaccumulated PCDD/DFs from the sediment at Kentucky Lake.
Dioxin-Like PCBs The concentrations of dioxin-like PCBs in sediment ranged from 44 to 1000 in LE and, 70 to 2000 in KDTW on a ng/g dry wt basis (Table 3). The results showed a statistically significant difference between locations at the P > 0.01 level. Concentrations of dioxin-like PCBs were in the range of 24-96 in LE and 18-100 in KDTW on a ng/g fat wt basis (Table 3). In particular, greater levels of PCBs were observed in KDTW mussel tissue; however, there is no statistical difference (P < 0.03) between locations. Heavy industrial activity around KDTW and less industrial activity around LE is a possible explanation for these results. Excluding CB-123 in mussel tissues from LE, all dioxin-like PCBs were detected at considerable
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Arch Environ Contam Toxicol (2008) 54:20–30
Table 3 Concentrations of dioxin-like PCBs in sediment (ng/g dry wt) and mussel (ng/g fat wt) from Kentucky Lake Sediment Location
Mussel
Ledbetter Embayment (n = 6)
Tailwater (n = 5)
Minimum
Mean
0.11 Minimum Mean Maximum Minimum
PCB-81
0.02
0.11
0.45
0.02
0.12
0.25
0.01
0.01
0.02
0.01
0.01
0.01
PCB-77
2.8
17
73
2.3
17
45
0.89
1.3
2.3
0.74
1.4
2.0
PCB-126
0.37
0.85
1.9
0.28
1.8
6.4
0.10
3.8
11
0.08
0.11
0.14
PCB-169
0.03
0.05
0.10
0.02
0.15
0.34
0.01
0.02
0.04
0.01
0.01
0.02
PCB-105
10
45
110
5.1
61
160
5.2
7.5
17
2.5
9.4
14
PCB-114
0.70
6.5
21
0.91
2.6
10
0.04
0.17
0.32
0.11
0.46
0.91
PCB-118
4.4
120
290
39
210
710
0.90
19
43
0.68
20
35
PCB-123
0.22
9.0
36
2.6
6.2
19
<0.01
<0.01
<0.01
0.09
0.09
0.09
PCB-156
3.9
25
120
1.8
13
47
0.86
1.4
2.45
0.95
3.2
5.4
PCB-157
0.71
6.3
25
0.92
2.9
10
0.25
0.47
1.11
0.36
0.80
1.6
PCB-167
1.3
9.2
41
0.22
5.7
20
0.68
1.1
2.20
0.75
1.9
3.3
PCB-189 Di-orthoa
0.41
1.0
3.3
0.29
1.8
7.6
0.05
0.07
0.08
0.07
0.44
1.2
PCB-170
5.8
26
110
6.2
59
250
2.1
4.5
6.9
3.0
9.0
16
PCB-180
13
51
190
11
170
660
2.8
9.9
20
8.9
30
54
Non-ortho
3.2
18
75
2.6
19
52
1.0
5.1
12
0.90
1.5
2.2
Mono-ortho 22
220
650
50
300
980
9.9
30
67
5.6
36
55
Di-ortho
19
77
300
17
230
910
9.4
14
27
12
39
70
Sum PCBs
44
320
1000
70
550
2000
24
49
96
18
76
100
Fat (%) Maximum
Ledbetter Embayment (n = 6) 0.30 Mean
0.48 Maximum
Tailwater (n = 5) 0.24 0.33 0.39 Minimum Mean Maximum
Non-orthoa
Mono-ortho
a
The values rounded a
PCB IUPAC numbers
concentrations. Among non-ortho PCBs, CB-77 was predominated, followed by CB-126, CB-169, and CB-81 in sediments and CB-126, CB-81, and CB-169 in mussel tissues. This suggested that mussels metabolize CB-169 faster than CB-81. Among mono-ortho PCBs, CB-118 was a prevalent congener followed by CBs 105, 156, 167, 157, 114, 123, and 189. Between the two di-ortho PCB congeners, CB-180 was a greater accumulant than CB-170. On a whole, mono-ortho PCBs constitute 48.3-69.6% in sediment and 44.4-87.4% in mussel tissues. Non-ortho PCBs were the least contributors with 1.4-28.9% in sediment and 2.3-13.6% in mussel tissues, the rest was shared by the two di-ortho PCBs. The observed levels of dioxin-like PCBs in this study were lower than those detected on the coast of Georgia in the USA and the Tokyo Bay of Japan (Kannan 1999; Yamashita et al. 2000), but were higher than those at the Detroit River in the USA (Kannan et al. 2001), while Kannan (1999) reported that clams off coastal Georgia contained levels ten times higher than that of the mussel tissues analyzed in present study. However, the PCB
123
accumulation pattern in sediment and clams from Georgia showed a similar pattern in the present study. Varied levels between clam and mussel tissue again suggested a different metabolic capacity of these animals (Kannan 1999). Furthermore, detection limits less than that of CB123 and CB-189 in some mussel tissues in this study showed that these two congeners were metabolized by the mussels because these congeners were present in sediment samples. Correlation between sediment and mussel was significant (r2 = 0.9263 in LE and r2 = 0.8793 in KDTW) (Fig. 3) for dioxin-like PCBs. These results showed that mussel bioaccumulated dioxin-like PCBs from the sediment in Kentucky Lake. However, a slightly lower r2 for dioxin-like PCBs compared with that of PCDD/DFs is probably due to metabolism of dioxin-like PCBs and their differences in chemical properties when compared with PCDD/DFs. For PCDD/DF we observed a higher proportion of higher-chlorinated dioxins and furans, and these congeners may not be easily metabolized by mussel and/or current intake from the sediment.
Arch Environ Contam Toxicol (2008) 54:20–30
27
Table 4 Toxic equivalency in sediment (pgTEQ/g dry wt) and mussel (pgTEQ/g fat wt) of Kentucky Lake Sediment
Mussel
Ledbetter Embayment (n = 6)
Tailwater (n = 5)
Minimum
Mean
Maximum
0.113 Minimum Mean Maximum Minimum
0.303 Mean
0.477 Maximum
0.237 0.326 0.389 Minimum Mean Maximum
PCDDs
0.22
0.40
0.64
0.05
0.41
0.78
6.5
111
415
0.35
18
56
PCDFs
0.04
0.13
0.35
0.02
0.45
1.8
0.0
62
240
6.5
14
26
Non-ortho
2.1
6.0
17
1.6
11
37
0.57
19
57
0.47
0.71
0.92
Mono-ortho 0.11
1.1
3.2
0.25
1.5
4.9
0.04
0.15
0.34
0.03
0.18
0.31
Total
7.6
21
2.0
13
44
7.1
193
713
7.4
32
83
2.5
Ledbetter Embayment (n = 6)
Biota Sediment Accumulation Factors (BSAFs) BSAFs have been proposed as a simple model for predicting the bioaccumulation of sediment-associated neutral organic contaminants by infaunal invertebrates (Kannan 1999). BSAF can be estimated based on the dry weightnormalized concentrations of contaminants in mussel divided by dry weight concentrations of contaminants in sediment by using the formula BSAF = Cfat/Coc. This simple construct of contaminant partitioning in infaunal organisms sediment systems is based on the assumption that no kinetic or structural barriers to the establishment of equilibrium are present. Nevertheless, because PCDD/DF and PCB congeners with greater numbers of chlorine atoms provided structural barriers to bioaccumulation, BSAFs varied depending on the species (both chemical and biological), sediment organic carbon, and contaminant concentrations, which suggested the need for site-specific evaluation of BSAFs. While most studies on BASFs were conducted on the partitioning of greater chlorinated PCBs with log Kow > 6.5, the Kentucky Lake watershed afforded an opportunity to examine partitioning of higher-chlorinated PCB congeners between sediment and mussel. Estimated BSAF in LE and KDTW was higher for TCDD, and decreased gradually with increasing chlorination. Similarly, TCDF, PeCDFs, and HxCDFs had greater BSAFs than HpCDF and OCDF. Altogether, OCDD and OCDF had lower BSAFs (Fig. 4). For dioxin-like PCBs, BASF was consistent with four non-, eight mono-, and two di-ortho PCBs. PCB-169 was highly enriched in LE while PCB-167 was prevalent in KDTW (Fig. 4). BSAFs for individual congeners of PCDD/DFs and dioxin-like PCBs varied by order of magnitude (Fig. 4). Earlier studies showed very low BASFs with a range of 0.07-0.88 in between clam sediment (Kannan 1999). Similarly, another study reported a BASF range of 0.66-7.2 for 2,3,7,8-chlorine-substituted PCDD/ DFs and a range of 0.0012-10 for non-2,3,7,8-PCDD/DFs (Sakurai et al. 2000). However, both studies compared clam sediment with the lipid weight and organic carbon of
Tailwater (n = 5)
sediment concentrations of an earlier study and therefore comparison of BSAFs is not withstanding. Furthermore, species-specific accumulation and metabolic capacity of contaminants would produce varied results. The large differences in BSAF between LE and KDTW reflect local contamination, species-specific variation, and age-related differences of mussel (Table 1). Collectively, BSAF studies showed that most toxic chemicals like TCDD, TCDF, and non-ortho PCBs have a high affinity to accumulate in biota and, therefore, it is considered a great concern because of the prolonged toxic effects on biota at lower trophic levels and the biomagnification of these chemicals to higher-trophiclevel fish, wildlife, and humans.
Toxic Equivalency (TEQ) TEQ is an acronym for 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) equivalents. It is a means of expressing the net toxicity of a complex mixture of different PCDD/F congeners and dioxin-like PCBs in terms of an equivalent quantity of 2,3,7,8-TCDD, the most toxic PCDD/DF or PCB congener. Each of the seventeen 2,3,7,8-substituted congeners and PCB compounds chlorinated in both para positions and at least two meta positions, but not the ortho positions, i.e., the non-ortho and mono-ortho-substituted congeners, have all been assigned a toxic equivalency factor (TEF) based on its toxicity relative to that of 2,3,7,8TCDD, which is universally assigned a TEF of 1. Multiplication of the concentration of a PCDD/DF and dioxinlike PCBs by its assigned TEF gives its concentration in terms of TEQ, and the toxicity of a mixture is the sum of the TEQs calculated for all congeners. Although, several TEF schemes have been proposed, the WHO TEF was used in our study for PCBs and PCDD/DFs. The human and fish TEFs were followed for the sediment and mussel TEQ calculations, respectively. The two di-ortho PCBs were not included in the TEQ estimation because of the unavailability of TEFs in the WHO TEF database.
123
28
Arch Environ Contam Toxicol (2008) 54:20–30
Fig. 4 Biota-sediment accumulation factors (BSAF) by PCDD/DFs and dioxin-like PCBs
30
Ledbetter Embayment 20
2,
3, 7, 8 2, -D 3, 7, 1, 8 2, 3, -D 4, 7 1, 2, ,8-D 3, 6 1 , ,7,8 2, 3 , -D 7 1, 2, ,8,9 3, 4 , -D 6, 7, 8D O CD D 2, 3, 7, 8 1, 2, -F 3, 7 2, ,8-F 3, 4, 7 1, 2, ,83, F 4 1 , ,7,8 2, 3 , -F 6 2 , ,7 ,8 3, 4 , -F 6 1 , ,7,8 2, -F 3 1 , , 7, 8 2, , 93, F 4 1, ,6,7 2, , 8 3, 4, -F 7, 8, 9F O CD F TE Q
0
1,
Biota-sediment accumulation factor
Tail River 10
50 40 30
Ledbetter Embayment
20
Tail River
10
Fig. 5 Toxicity contribution by PCDD/DFs and dioxin-like PCBs in sediment and mussel samples from Kentucky Lake
PCDDs
TE Q
-7 7 CB -1 26 CB -1 69 CB -1 05 CB -1 14 CB -1 18 CB -1 23 CB -1 56 CB -1 57 CB -1 67 CB -1 89 CB -1 70 CB -1 80
CB
CB -8
1
0
PCDFs
M u s s e l T a il r i v er
Mussel Ledbetter Embayment N o n - ort h o PCBs Sediment Tailriver Mono-ortho PCBs Sediment Ledbetter Embayment
0%
50%
100%
Contribution (%)
Mussels from LE had a maximum TEQ (pg TEQ/g fat wt) with mean value of 193 (range: 7.1-713), while KDTW mussel had a significantly (P < 0.05) lower TEQ of 32 (range: 7.4-83). By contrast, LE sediment had a significantly (P < 0.05) lower TEQ of 7.6 (range: 2.5-21) than that of the KDTW sediment of 13 (range: 2.0-44). The results also suggested that despite heavy industrial and extensive agricultural activity in and around KDTW, that did not increase TEQ in mussel. Overall, PCDDs and PCDFs comprised 93% of contaminants in KDTW and LE mussel tissue (Fig. 5). On the other hand, dioxin-like PCBs greatly contributed to contamination in KDTW (97%) and
123
LE (90%) (Fig. 5). On the whole, greater TEQ by PCDD/ DF in mussel tissue is of concern in Kentucky Lake. Our earlier studies that used a variety of samples from different locations showed higher TEQ contribution by non-ortho PCBs (Iseki et al. 2000; Senthil Kumar et al. 2001a, 2002a, b, c, 2003a, b, c, d). Greater atmospheric deposition of PCDD/DFs instead of industrial input into Kentucky Lake is of great concern. Observed TEQ in LE was similar to that of fish from the Great Lakes (Giesy et al. 1999), but TEQ levels in KDTW were similar to or less than that of aquatic organisms from different parts of the country (Senthil Kumar et al. 2001a, 2002b, 2003c). Dioxin levels
Arch Environ Contam Toxicol (2008) 54:20–30
in food, environmental samples, and breast milk decreased through the 1990s. In most industrialized countries, the daily dioxin intake is currently on the order of 1-3 pg ITEQ/kg body weight per day. At very high dioxin exposure, the risk for all cancers combined appears to increase. Noncancer effects of dioxin exposure include cardiovascular diseases, diabetes, and changes in blood composition. Thus, the mean TEQ levels noticed in mussel from LE are concerning; it may accumulate greatly in humans and has negative health implications for adults, even those with a body weight greater than 60 kg.
Conclusions The levels of dioxin and dioxin-like compounds analyzed have shown spatial variation in their levels. HpCDD and OCDD were major contaminants in sediment and mussel tissues. The atmospheric deposition of PCDD/DFs was shown to be similar irrespective of the locations and industrial and agricultural activity of the present study. Besides, impurities from agrochemicals should not be ignored due to a higher accumulation in mussel as shown in the Ledbetter embayment of Kentucky Lake. In contrast, dioxin-like PCB levels were greater in and around the heavy industrial areas in KDTW. In particular, PCB-118 was the predominant congener in both sample matrices. Higher-chlorinated PCDD/DFs showed less BSAF than the less chlorinated ones like TCDD, TCDF, PeCDF, and HxCDF. Furthermore, non-ortho and mono-ortho coplanar PCBs are also highly enriched in mussel tissues. Consequently, TEQ was greater in mussel tissues and consumption may lead to negative implications. It is worth mentioning that the contribution by PCDD/DF to toxicity in Kentucky Lake rather than the dioxin-like PCBs in mussel tissues is of concern. Acknowledgments National Science Foundation’s Collaborative Research in Undergraduate Institutions (NSF-CRUI), Murray State University, Murray, KY, USA, the Japan Society for the Promotion of Science (JSPS) (Fellowship to KS; ID:P00165), and Yokohama National University, Yokohama, Japan supported the research. The authors are thankful to Dr. James Sickel, Professor of Biology, Murray State University for his help in field sampling, identification and age determination of freshwater mussels.
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