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Author's personal copy
Marine Pollution Bulletin 63 (2011) 516–522
Contents lists available at ScienceDirect
Marine Pollution Bulletin
journal homepage: www.elsevier.com/locate/marpolbul
Distribution and source apportionments of polychlorinated biphenyls (PCBs)
in mariculture sediments from the Pearl River Delta, South China
Hong-sheng Wang a,b, Jun Du b, Ho-man Leung a, Anna Oi Wah Leung a, Peng Liang a, John P. Giesy c,
Chris K.C. Wong a,⇑, Ming-Hung Wong a,⇑
a
b
c
Croucher Institute for Environmental Sciences, and Department of Biology, Hong Kong Baptist University, Kowloon Tong, Hong Kong, PR China
Department of Microbial and Biochemical Pharmacy, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, Guangdong, PR China
Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong, PR China
a r t i c l e
i n f o
Keywords:
PCBs
Mariculture
Enrichment percentage
Fish feed
a b s t r a c t
Surface and core sediments collected from six mariculture farms in the Pearl River Delta (PRD) were anaP
lyzed to evaluate contamination levels of polychlorinated biphenyls (PCBs). The PCBs (37 congeners)
concentrations ranged from 5.10 to 11.0 ng g1 (mean 7.96 ng g1) in surface and 3.19 to 22.1 ng g1
(mean 7.75 ng g1) in core sediments, respectively. The concentrations were significantly higher than
that measured in the sediments of their corresponding reference sites, whereby the average enrichment
percentages were 62.0% and 42.7% in surface and core sediments, respectively. Significant correlations
(R2 = 0.77, p < 0.05) of PCB homologue group proportions between fish feeds and surface mariculture sediments suggested that fish feed input was probably the main source for the enrichment of PCBs. Due to
the fact that PCBs could be transferred along food chains, PCB contamination in fish feeds and mariculture
sediments should not be overlooked.
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
Polychlorinated biphenyls (PCBs) were first manufactured commercially in 1929 and used widely as electric insulators in transformers, hydraulic fluids and paint additives (Safe, 1994). Serious
concerns about the distribution of PCBs were raised since they
were found to be ubiquitous and persistent in environmental and
biota samples such as soil, water, animal and human tissues
(Jansson et al., 1993). Although the production of PCBs has been
banned since the early 1970s (Harrad et al., 1994), PCBs persist
as legacy pollutants in which the chronic toxicity still represents
a serious environmental risk.
High concentrations of PCBs have been reported in the coastal
food web such in fish and shellfish collected from all over the
world (Domingo and Bocio, 2007), including South China (Nie
et al., 2005). As PCBs in sediments can be bioaccumulated in benthic organisms and transported further up the food chain to higher
level consumers (such as fish) (Magnusson et al., 2006; Parnell
et al., 2008), the assessment of sediment PCB contamination is an
important issue for the evaluation of food safety, especially with
regards to fish cultured along the coastal areas. Nutrient enrichment in mariculture sediments is common worldwide such as in
⇑ Corresponding authors. Tel.: +852 3411 7746; fax: +852 3411 7743 (M.H.
Wong), tel.: +852 3411 7053; fax: +852 3411 5995 (C.K.C. Wong).
E-mail addresses: ckcwong@hkbu.edu.hk (C.K.C. Wong), mhwong@hkbu.edu.hk
(M.-H. Wong).
0025-326X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.marpolbul.2011.02.009
Japan (Yokoyama et al., 2006), Turkey (Alpaslant and Pulatsue,
2008), Spain (Mendiguchia et al., 2006) and Hong Kong (Gao
et al., 2005). The enriched organic matter could enhance the accumulation capacity of heavy metals (Mendiguchia et al., 2006) and
persistent organic pollutants (POPs) (Wang et al., 2010a) in mariculture sediments. The unconsumed fish feeds containing trace organic pollutants would further promote this contamination.
Although high PCB concentrations have been observed in fish feeds
manufactured in various parts of the world including China (Guo
et al., 2009), Canada (Kelly et al., 2008) and Europe (Jacobs et al.,
2002), no data is currently available to differentiate the levels
and sources of PCBs between natural and mariculture sediments.
The aim of the present study was to evaluate the level of enrichment of PCBs in mariculture surface and core sediments. The temporal trends, potential source apportionments and sediment
burden of PCBs were also investigated. To our knowledge, this is
the first study to investigate and compare the differences in PCB
contamination in mariculture sediments with levels found in natural sediments.
2. Methods and materials
2.1. Study area and sampling
Six mariculture farms located at Xixiang (XX), Tsing Yi (TY), Sam
Mun Tsai (SMT), Mirs Bay (MB), Sai Kung (SK) and Tung Lung Chau
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H.-s. Wang et al. / Marine Pollution Bulletin 63 (2011) 516–522
(TLC) were chosen for this study (Fig. 1). All sampling sites were located along the coast of Hong Kong and mainland China, representing the typical subtropical fish farming regions in the Pearl River
Delta (PRD). The major fish feeds used in the mariculture were
trash fish (mainly anchovies Thryssa sp.), and moist and dry pellet
feeds. The detailed information about each sampling site is listed in
Table 1. During July–September 2008, at least three surface (0–
5 cm, using a stainless steel grab sampler) and core (using a KC Kajak sediment core sampler, ø60/52 mm, length 100 cm, Denmark)
sediment samples (including sediments beneath mariculture cages
and reference sediments about 1–2 km away) were collected at
each site. Each sediment core was sectioned into 2.5 cm intervals
for the first 10 cm, then 5 cm intervals to 40 cm, and then 10 cm
intervals to the end. Fish feeds including trash fish (Thryssa sp.,
n = 6) and dry pellet feeds (n = 9), originally bought from local markets, were collected from TLC fish farms. Fish farmers of other sampling sites confirmed that their feeds were also bought from local
markets, but they were reluctant to give us the feeds. All samples
517
were wrapped in aluminum foil and kept at 20 °C until further
analyses.
2.2. Chemical analyses
The collected sediment samples were freeze-dried, homogenized and stored in desiccators prior to chemical analyses. The
samples were Soxhlet extracted according to US EPA Standard
Method 3540 C (USEPA, 1996a) using 120 ml mixture of acetone,
dichloromethane (DCM) and n-hexane (1:1:1, v:v:v) for 16–18 h
at 68 °C. Acid washed copper powder was added into the extracts
to remove sulfur. The extract solution was then concentrated to
2 ml with a rotary evaporator. About 10 ml of n-hexane was added
and was rotary evaporated to remove acetone and DCM. The concentrated extract was then cleaned up through a multilayer silica
gel column containing, from top to bottom, 1 g anhydrous sodium
sulfate, 2 g of deactivated silica (3% organic-free reagent water, w/
w), 8 g of acidic silica (44% concentrated sulfuric acid, w/w), 1 g of
Fig. 1. Sampling sites. 1: Xixiang (XX); 2: Tsing Yi (TY); 3: Sam Mun Tsai (SMT); 4: Mirs Bay (MB); 5: Sai Kung (SK); 6: Tung Lung Chau (TLC).
Table 1
Detailed information of mariculture sites.
No.
Site
Ab.
Latitude
Longitude
WD. (m)
OM (% LOI)a
Descriptions
1
Xixiang
XX
22°33.243’N
113°51.738’E
5–10
7.25 ± 0.91
2
Tsing Yi
TY
22°21.047’N
114°03.366’E
40–50
7.97 ± 0.12
3
Sam Mun Tsai
SMT
22°27.288’N
114°13.481’E
30–40
18.5 ± 1.34
4
Mirs Bay
MB
22°33.870’N
114°31.260’E
20–25
11.1 ± 0.79
5
Sai Kung
SK
22°20.483’N
114°19.043’E
20–30
10.9 ± 0.74
6
Tung Lung Chau
TLC
22°15.400’N
114°17.228’E
20–30
6.38 ± 0.42
Located at Pearl River Estuary, which constantly receives
discharges from the Pearl River. Black mud sediment
Located beside the Kwai Tsing Container Terminal, the third
busiest container port in the world. Participant of the ‘‘Accredited
Fish Farm Scheme’’
Located at a semi-enclosed bay in the inner region of Tolo Harbor
with a long history of receiving heavy pollution. Black mud
sediment
A semi-enclosed bay located in the east coast of Guangdong
Province. Relatively unpolluted marine environment (Liu and
Hills, 1998)
Near the open-sea. Relatively unpolluted marine environment
around culture cages
A small island located off the peninsula of Clear Water Bay
Ab. = Abbreviation; WD. = Water depth.
a
The organic matter (loss of ignition) in mariculture surface sediments of each sampling sites.
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deactivated silica, and 1 g of anhydrous sodium (USEPA, 1996c).
PCB enriched fractions were eluted from the columns with
160 ml of n-hexane. The eluate was then concentrated and passed
through a florisil column with 160 ml n-hexane (USEPA, 1996b).
Deuterated internal standard 2,4,5,6-tetrachloro-mxylene (TCmX)
was added into all extracts to the concentration of 100 ng g1 prior
to instrumental analysis for quantification. The final volume of all
the samples was 200 ll. PCBs were quantitatively analyzed by GC–
MS (Agilent 6890 GC coupled with a 5973 MS selective detector),
with a fused silica capillary column (5% phenyl, 95% methyl silicone, 30 m 0.25 mm 0.25 lm). The oven temperature was programmed from 100 °C (initial time, 2 min) to 270 °C at a rate of
5 °C/min, held for 8 min, and then ramped from 270 °C to 320 °C
at a rate of 2 °C/min. Measurement values below the limit of detection (LOD) were recorded as zero. Thirty-seven congeners (PCB 18,
28, 37, 44, 49, 52, 70, 74, 77, 81, 87, 99, 101, 105, 114, 118, 119,
123, 126, 128, 138, 151, 153, 156, 157,158, 167, 168, 169, 170,
177, 180, 183, 187, 189, 194 and 199) were detected. The geochemical parameters (including organic matter (OM), sediment
carbon (C), nitrogen (N) and sulfur (S), and sediment particle size)
of the surface mariculture and reference sediments were determined in our previous study (Liang et al., 2010).
2.3. QA/QC
The standard reference material (SRM) 1941b (marine sediment) obtained from the National Institute of Standards and Technology (NIST, USA) was used. The recovery rate of individual PCB
congeners ranged from 78.7% to 109%. The instrumental limit of
detection (LOD) was determined as the concentrations of analytes
that gave rise to a peak with a signal to noise ratio (S/N) of 3, and
ranged from 0.2 to 0.5 ng g1 for different PCB congeners. All data
were subjected to strict quality control procedures. For each set of
15 samples, a procedural blank, a spiked blank (standards spiked
into solvent), a sample duplicate, and a standard reference material
(NIST SRM 1941b) sample were processed. The levels in the procedural blank were less than LOD. All the data were corrected with
the recovery rates and reported in ng g1, dw (dry weight).
2.4. Data analyses
P
P
PCBs was defined as the sum of 37 PCB congeners, i-PCBs
(indicator PCBs) as the sum of PCB 28, 52, 101, 138, 153 and 180,
P
and
dl-PCBs (dioxin-like PCBs) as the sum of PCB 77, 81, 105,
114, 118, 123, 126, 156, 157, 167, 169 and 189. Data analyses were
performed using SPSS 13.0 for Windows. Normality was confirmed
by the Kolmogorov–Smirnov test. PCB concentrations in mariculture and reference sediments were analyzed using two independent t-tests, Wilcoxon rank sum test, one-way ANOVA and
Kruskal–Wallis test.
3. Results and discussion
3.1. Distribution of PCBs in mariculture and reference surface
sediments
P
In surface mariculture sediments of the PRD, the PCBs con1
centrations ranged from 5.10 to 11.0 ng g , with a mean of
P
P
7.96 ng g1. The mean concentrations of
i-PCBs and
dl-PCBs
1
were 1.18 and 3.89 ng g , respectively. The most abundant congeners were PCB 138, 81, 153, 169, 37, 189 and 158, comprising up
to 55.8% of the total amount. The proportions of PCBs generally decreased according to the following trend: hexa-PCBs > pentaPCBs > tetra-PCBs > hepta-PCBs > tri-PCBs > octa-PCBs (Fig. 2). Tetra-PCBs (23%) detected in mariculture surface sediments, sug-
gested the presence of a local source of contamination (Goerke
and Weber, 1998). Regression analyses were performed between
P
the
PCBs concentrations and their corresponding geochemical
parameters (including OM, sediment carbon (C), nitrogen (N) and
sulfur (S), and sediment particle size) at each sampling sites. No
P
significant correlations were found between
PCBs concentrations and OM, C, N and S contents as well as particle size. The findings were not consistent with a previous study which indicated
that higher concentrations of PCBs typically occur in sediments
having a larger fraction of clays, OM, or micro-particulate (Burgess
et al., 2001). The present results suggested that PCBs in mariculture
sediments might have been influenced by local mariculture
activities.
P
The highest concentration of
PCBs was detected at Xixiang
(11.0 ng g1), which was located adjacent to Shenzhen, a city with
rapid industrialization and socio-economic development during
the past 30 years. In addition, Xixiang receives large quantities of
polluted water from the Pearl River (Luo et al., 2009). The mariculture sediments collected from Tsing Yi contained the second highest PCB levels (9.98 ng g1). This sampling site was located near the
container vessels and the Kwai Tsing container terminal, one of the
busiest container ports in the world.
When compared to data from various aquaculture sediments
worldwide, the PCB contamination levels (5.10–11.0 ng g1, mean
7.96 ng g1) in mariculture sediments of PRD in the present study
were higher than that in freshwater fishpond sediments in Shanghai, China (mean 0.46 ng g1, Nakata et al., 2005), and similar to
those of Daya Bay, a key mariculture area in China (0.85–
27.4 ng g1, mean 8.83 ng g1, Zhou et al., 2001) and New Brunswick, Canada (1.07–10.4 ng g1, Sather et al., 2006). In general,
the PCB levels in mariculture surface sediments of the PRD were
moderately high.
3.2. Vertical distribution of PCBs in mariculture and reference core
sediments
P
P
The vertical distributions of PCBs and dl-PCBs in the mariculture and reference core sediments of the six sampling sites are
shown in Fig. 3. PCBs concentrations in mariculture core sediments
followed the trend of SK > XX > SK > SMT > TLC > MB, which was
P
the same as that for the mariculture surface sediments. The PCBs
1
concentrations ranged from 3.19 to 22.1 ng g , with a mean of
7.75 ng g1. Significantly (p < 0.05) higher concentrations of
P
PCBs were recorded at the depth of 20–25 cm at XX, 15–20 cm
at TY and 30–35 cm at SK in the mariculture core sediments
(Fig. 3). Since the sediment cores were not dated, it was difficult
to attribute the historical usage of PCBs in the sections of the mariculture sediment cores analyzed. Therefore, only the relative temporal distribution of the PCBs is known. Many factors such as
hydrodynamic processes and the use of fish feed (frequency and
amount) could significantly affect the sedimentation rates. In general, our data indicated that PCBs were widely used in the past. PCB
homologue group proportions in the core mariculture sediments
were comparable with that in the surface sediments, which were
in line with a previous study performed in this region (Wei et al.,
2008).
P
In reference core sediments, concentrations of
PCBs (1.46–
1
1
10.2 ng g , mean 4.97 ng g ) were significantly (p < 0.05) lower
than that in mariculture sediments. Generally, concentrations of
PCBs in the reference core sediments showed a decreasing trend
starting from a depth of 10 cm (p < 0.05). The observation was in
line with the same previous study that PCBs in sediment cores declined starting in mid-1990s in Hong Kong (Wei et al., 2008). The
PCB homologue group proportions decreased according to the following trend: hexa-PCBs > penta-PCBs > hepta-PCBs > tetra-PCBs >
tri-PCBs > octa-PCBs. The proportion of hepta-PCBs was higher than
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H.-s. Wang et al. / Marine Pollution Bulletin 63 (2011) 516–522
Fig. 2. PCB homologue group proportions in mariculture sediments of six sampling sites.
Concentrations (ng g-1, dw)
0
3
6
9
12 15 18 21 24
0
3
6
9
12 15 18 21 24
0
3
6
9
12 15 18 21 24
Depth (cm)
10
20
30
40
XX
TY
SMT
MB
SK
TLC
Depth (cm)
10
20
30
40
Fig. 3. Changes in
P
P
PCBs and dl-PCBs concentrations with depth of mariculture and reference core sediments at the six sampling sites (XX, TY, SMT, MB, SK and TLC).
the proportion of tetra-PCBs in reference core sediments, however
this was not observed in the mariculture sediments and suggested
that these natural sediments contained a prevailing contribution of
Aroclor 1254:1260 according to the Aroclor composition (Colombo
et al., 2005). The higher proportions of tri- and tetra-PCBs in core
sediments compared with surface sediments also suggested the
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520
H.-s. Wang et al. / Marine Pollution Bulletin 63 (2011) 516–522
basic trend of PCBs in coastal sediment: decrease of relative abundance of less chlorinated congeners (tri- and tetra-PCBs) with a
parallel increase of higher chlorinated PCBs (Spongberg, 2004).
3.3. Enrichment of PCBs in mariculture surface and core sediments
The enrichment percentage was calculated according to the following formula (1) (Gao et al., 2005):
Eri: ¼ ðC Aq: C Ref : Þ 100=C Ref :
ð1Þ
where Eri. is the enrichment percentage; CAq. the concentration in
mariculture sediment; and CRef. the concentration in reference sediment. As shown in Tables 2 and 3, the concentrations of PCBs in
both surface and core reference sediments were significantly
(p < 0.01) lower than that in the mariculture sediments. The average
P
P
P
enrichment percentages of PCBs, i-PCBs and dl-PCBs detected
in surface sediments were 62.0%, 78.7% and 49.2%, respectively.
These were significantly (p < 0.05) higher than that in the core
sediments which were 45.7%, 58.2% and 33.7%, respectively. This
implied that mariculture surface sediments could accumulate more
PCBs compared to core sediments, due to mariculture-related activities.The enriched mass inventory (EI) of PCBs in the mariculture
sediments was calculated according to the following formula (2)
(Lin et al., 2009):
EI ¼ ðC Aq: C Ref : ÞAdp
ð2Þ
where CAq. is the concentration in mariculture sediment, CRef. the
concentration in reference sediment, A the total water area
(224.4 km2) of mariculture zones in the PRD (Cao et al., 2007), d
the assumed sediment density of 1.5 g/cm3, and p sediment thickness (5 cm for surface and 30 cm for core sediment).
P
For surface and core sediments, the mean values of PCBs concentrations in mariculture and reference sediments were used to
deduce the burden of enriched PCBs. The total inventories of
P
PCBs in mariculture surface and core sediments of the PRD were
P
0.13 t and 0.78 t, respectively. The calculated enriched PCBs in
mariculture surface and core sediments were 0.047 t and 0.25 t,
respectively after the subtraction of the inventories in the reference sediments. Considering that the top 5.0 cm layer represents
1–2 years of accumulation according to sediment trap data, the enriched PCB inventories (0.047 t) for a total surface of 224.4 km2,
would result in average depositional fluxes of 0.11–0.21 mg
m2 yr1 from mariculture-related activities.
3.4. Potential sources of PCB to mariculture sediments
As mentioned above, mariculture surface and core sediments
were enriched with PCBs. Fish feed input was expected to be the
most important source for organic pollutants in mariculture sediP
ments. The concentrations of PCBs in fish feeds collected from
TLC were 19.2 ± 6.08 ng g1 (dw) in trash fish and 10.4 ± 2.12 ng g1
(dw) in commercial dry pellets, respectively. The values were within the same order of magnitude of those reported in aquaculture
feeds collected from the PRD (Guo et al., 2009). There was a significant correlation (Y = 1.181X 3.038, R2 = 0.77, p < 0.05) in the PCB
homologue group proportions between fish feeds with that in surface mariculture sediments collected from TLC. The data revealed
that PCBs in surface mariculture sediments may be derived from
fish feed inputs. High PCB concentrations were observed in fish
feeds manufactured all over the world including Europe (75.6–
1153 ng g1, Jacobs et al., 2002), Canada (mean 270 ng g1, Kelly
et al., 2008) and America (mean 84.8 ng g1, Serrano et al., 2008),
suggesting that the enrichment of PCBs in mariculture sediments
may be a worldwide problem.
3.5. Ecotoxicological and food safety concerns
To evaluate the ecotoxicological aspect of enriched PCBs in
mariculture sediment, the present data were compared with that
of US-EPA/NOAA and (TEC, EEC) SQGs for marine sediments (Gomez-Gutierrez et al., 2007; Long et al., 1995). The NOAA guideline
specifies ‘‘effects range low’’ (ERL) and ‘‘effects range median’’
(ERM), with ERL represents the chemical concentration below
which an adverse effect would rarely be observed, while ERM represents the concentration above which adverse effects would frequently occur. According to Long et al. (1995), ERL and ERM only
refer to 7 PCB congeners (PCB-28, 52, 101, 118, 138, 153 and
180). PCB concentrations (sum of 7 PCB congeners) in all six mariculture surface sediments (max 3.58 ng g1) were much lower than
the ERL (22.7 ng g1).
Former studies showed that congener proportions of PCBs were
comparable between benthic species and sediments (Chen et al.,
2002; Liu et al., 2007). Therefore, the concentrations of organochloride detected in benthic species could be a result of bioaccumulation from sediments (Magnusson et al., 2006). For animals at
higher trophic levels such as carnivorous fish, a study indicated
that the most probable source of PCBs contamination in fish tissues
(such as sanddab, sole, rockfish) was due to the disposal of dredged
sediments, and was not derived from the natural transport of
Table 2
PCBs (ng g1, dry wt) concentrations in surface (0–5 cm) mariculture and reference sediments of each site.
XX
tri-PCBs
tetra-PCBs
penta-PCBs
hexa-PCBs
hepta-PCBs
octa-PCBs
P
i-PCBs
P
dl-PCBs
P
PCBs
TY
SMT
MB
SK
TLC
AE ± SD
Aq.
Ref.
Eri.
Aq.
Ref.
Eri.
Aq.
Ref.
Eri.
Aq.
Ref.
Eri.
Aq.
Ref.
Eri.
Aq.
Ref.
Eri.
1.71
3.55
2.25
2.78
0.71
ND
1.23
5.14
11.0
0.53
0.80
1.40
1.14
0.66
ND
0.81
2.36
4.53
222
345
61.1
143
8.49
N
51.8
118
143
0.44
1.30
2.86
3.47
1.54
ND
1.09
4.17
9.98
0.63
1.19
1.05
2.15
0.82
ND
0.51
2.45
5.86
30.2
9.16
173
61.0
88.4
N
113
69.9
70.2
0.37
1.59
2.05
1.25
1.05
ND
0.93
3.60
6.31
0.28
1.54
1.40
1.51
1.19
0.13
0.89
3.58
6.06
30.8
2.90
46.6
17.2
11.9
N
4.62
0.51
4.17
0.40
1.25
1.05
1.74
0.65
ND
0.43
3.10
5.10
0.24
0.63
0.99
1.62
0.81
ND
0.47
2.56
4.29
70.1
99.7
5.70
7.35
19.3
N
10.3
21.1
19.0
0.94
1.59
1.50
1.96
1.16
ND
1.77
2.96
7.16
0.14
0.25
0.76
1.59
0.63
ND
0.48
2.19
3.37
575
540
98.7
23.7
83.5
N
270
35.4
113
0.97
1.74
2.30
1.72
1.50
ND
1.62
4.34
8.23
0.43
1.07
1.40
1.63
1.93
0.26
1.14
2.89
6.72
129
62.6
63.8
5.71
22.5
N
42.6
50.1
22.5
Aq. = Mariculture sediments.
Ref. = Reference sediments.
Eri. = Enrichment percentage.
AE ± SD = Average enrichment percentage ± standard deviation.
ND = Not detected.
N = Could not be calculated.
166 ± 218
177 ± 218
74.7 ± 56.6
37.2 ± 57.9
21.1 ± 51.4
N
78.7 ± 103
49.2 ± 41.2
62.0 ± 56.6
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H.-s. Wang et al. / Marine Pollution Bulletin 63 (2011) 516–522
72.8 ± 84.2
109 ± 61.2
56.6 ± 25.4
32.2 ± 19.5
11.8 ± 21.4
N
58.2 ± 52.7
33.7 ± 19.3
45.7 ± 18.6
21.8
70.0
30.2
38.4
15.1
N
37.5
25.4
30.7
0.48
1.56
1.62
1.72
1.08
ND
0.97
3.02
6.49
0.33
0.52
1.12
1.78
1.58
ND
0.99
2.42
5.37
47.0
242
71.7
5.25
20.9
N
26.8
44.5
36.6
0.62
0.92
1.25
1.25
0.94
ND
0.70
2.41
4.96
AE ± SD
Eri.
Ref.
Aq.
0.49
1.76
1.93
1.88
1.25
ND
1.26
3.49
7.33
218
100
40.3
40.9
51.7
N
146
8.09
63.9
0.27
0.75
1.29
1.56
0.95
ND
0.56
2.75
4.81
0.85
1.50
1.81
2.20
1.44
ND
1.39
2.97
7.89
30.2
62.6
43.2
60.4
20.8
N
19.5
32.8
37.5
0.67
0.82
1.24
1.37
1.07
ND
0.73
2.60
5.19
0.47
1.34
1.78
2.20
1.29
0.05
0.87
3.45
7.14
21.6
84.4
46.0
7.16
1.55
N
21.8
20.4
26.7
0.53
0.74
1.32
1.81
1.28
ND
0.83
2.96
5.68
0.65
1.37
1.92
1.94
1.26
0.07
1.01
3.57
7.20
117
59.9
52.6
20.9
5.92
N
52.9
24.5
37.6
0.44
0.99
1.22
1.79
1.05
ND
0.84
2.77
5.63
Aq. = Mariculture sediments.
Ref. = Reference sediments.
Eri. = Enrichment percentage.
AE ± SD = Average enrichment percentage ± standard deviation.
ND = Not detected.
N = Could not be calculated.
0.96
1.58
1.86
2.16
1.11
0.08
1.28
3.45
7.75
111
149
111
47.6
22.7
N
137
71.3
81.1
0.41
0.81
1.03
1.35
0.98
ND
0.55
2.49
4.58
0.85
2.01
2.18
2.00
1.20
0.06
1.31
4.27
8.30
120
103
57.5
36.9
0.42
N
24.0
42.9
51.1
0.28
0.95
1.25
1.68
0.99
ND
0.76
2.76
5.19
Aq.
Ref.
2.5–5.0 cm
Ref.
Eri.
Aq.
0.61
1.93
1.97
2.30
1.00
ND
0.94
3.94
7.85
tri-PCBs
tetra-PCBs
penta-PCBs
hexa-PCBs
hepta-PCBs
octa-PCBs
P
i-PCBs
P
dl-PCBs
P
PCBs
25–30 cm
Eri.
Ref.
20–25 cm
Aq.
Ref.
Eri.
The authors thank Dr. X.L. Sun and Mr. K.W. Chan for technical
assistance. This research was supported by the Research Grants
Council of the University Grants Committee of Hong Kong (Collaborative Research Fund, HKBU1/CRF/08 and Special Equipment
Grant, HKBU09) and the Mini-AOE (Area of Excellence) Fund from
the Hong Kong Baptist University.
Aq.
15–20 cm
Eri.
Ref.
Aq.
10–15 cm
Eri.
Ref.
Aq.
Aq.
Ref.
Eri.
7.5–10 cm
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