Science of the Total Environment 466–467 (2014) 214–220
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Science of the Total Environment
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Aquaculture-derived enrichment of hexachlorocyclohexanes (HCHs)
and dichlorodiphenyltrichloroethanes (DDTs) in coastal sediments of
Hong Kong and adjacent mainland China
Hong-Sheng Wang a,⁎, Zhuo-Jia Chen b, Zhang Cheng c, Jun Du a,⁎⁎, Yu-Bon Man c, Ho-Man Leung c,
John P. Giesy d,e,f,g, Chris K.C. Wong c, Ming-Hung Wong c,⁎⁎⁎
a
Department of Microbial and Biochemical Pharmacy, School of Pharmaceutical Sciences, Sun Yat-sen University, No.132 Waihuandong Road, University Town, Guangzhou 510006, China
State Key Laboratory of Oncology in South China, Department of Pharmacy, Sun Yat-Sen University Cancer Center, Guangzhou 510060, China
c
State Key Laboratory in Marine Pollution - Croucher Institute for Environmental Sciences, Hong Kong Baptist University and City University of Hong Kong, Hong Kong SAR, PR China
d
Department of Veterinary Biomedical Sciences & Toxicological Center, University of Saskatchewan, Canada
e
Department of Biology & Chemistry and State Key Laboratory in Marine Pollution, City University of Hong Kong, Kowloon, Hong Kong, SAR, China
f
School of Biological Sciences, University of Hong Kong, Hong Kong, China
g
State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, China
b
H I G H L I G H T S
• Aquaculture could derive significant enrichment of OCPs in coastal sediments.
• The enriched OCPs were mainly derived from fish feeds and DDT-based antifouling paints.
• This is the first study for aquaculture-derived OCP contaminations in coastal sediments.
a r t i c l e
i n f o
Article history:
Received 23 April 2013
Received in revised form 5 July 2013
Accepted 6 July 2013
Available online xxxx
Editor: Eddy Y. Zeng
Keywords:
OCPs
Mariculture
Sediments
HCHs
DDTs
Pesticides
a b s t r a c t
To evaluate contamination of sediments along the coast of Hong Kong and adjacent mainland China, concentrations of hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) in surface and core
sediments were measured in six mariculture zones. In surface sediments (0 to 5 cm), concentrations of
∑HCHs and ∑DDTs in mariculture sediments were approximately 1.3- and 7.7-fold greater, respectively,
than those detected in sediments at corresponding reference sites, which were 1 to 2 km away in areas
where there was no mariculture. Similarly, in cores of sediments, concentrations of ∑HCHs and ∑DDTs
were 1.2- and 14-fold greater in mariculture zones, respectively. Enrichment relative to regional background
concentrations, expressed as percentages was as large as 8.67 × 103% for o,p'-DDD. The major sources of the
enriched organochlorine pesticides (OCPs) were hypothesized to be derived from the use of contaminated
fish feeds and anti-fouling paints for maintaining fish cages. Results of ecological risk assessments revealed
that enriched OCPs had a large potential to contaminate the surrounding marine environment and lead to
adverse effects on the associated biota. To our knowledge, this is the first study to evaluate the differences
of OCP contaminations between mariculture and natural coastal sediments.
Crown Copyright © 2013 Published by Elsevier B.V. All rights reserved.
1. Introduction
Rapid development of aquaculture has raised concerns about the
potential for these operations to cause adverse effects on the local
coastal marine environment (Cao et al., 2007). One of the most negative effects of cage aquaculture is uncontrolled release of extra-loads
⁎ Corresponding author. Tel.: +86 20 3994 3024.
⁎⁎ Corresponding author. Tel.: +86 20 3994 3022.
⁎⁎⁎ Corresponding author. Tel.: +852 34117746; fax: +852 34117743.
E-mail addresses: whongsh@mail.sysu.edu.cn (H.-S. Wang),
dujun@mail.sysu.edu.cn (J. Du), mhwong@hkbu.edu.hk (M.-H. Wong).
of nutrients, suspended solids and organic matters to the water and
sediments (Yokoyama et al., 2006). Nutrient enrichment in sediments
in the vicinity of mariculture is common all over the world, such as
Japan (Yokoyama et al., 2006), Turkey (Alpaslan and Pulatsü, 2008)
and Spain (Mendiguchia et al., 2006). In Hong Kong, the average annual total phosphorus (TP) loads to sediments beneath mariculture
cages increased by 13.2-fold relative to those at reference locations
(Gao et al., 2005).
Enrichment of nutrients could change the physical–chemical
characteristics of sediments, which act as a sink for heavy metals and
persistent organic pollutants (POPs). Results of previous studies indicated that heavy metals such as copper (Cu), zinc (Zn), lead (Pb) and
0048-9697/$ – see front matter. Crown Copyright © 2013 Published by Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.scitotenv.2013.07.027
H.-S. Wang et al. / Science of the Total Environment 466–467 (2014) 214–220
cadmium (Cd) were enriched in sediments near mariculture facilities
due to the presence of unconsumed fish feeds and antifouling paints
(Dean et al., 2007; Mendiguchia et al., 2006). Concentrations of
trace organic pollutants such as polychlorinated biphenyls (PCBs),
organochlorine pesticides (OCPs) and polybrominated diphenyl ethers
(PBDEs) were great in fish feeds manufactured in the Pearl River Delta
(PRD) (Guo et al., 2009b), Canada (Kelly et al., 2008), Spain (Serrano et
al., 2003) and Hong Kong (Leung et al., 2010). However, data about
enrichment of persistent organic pollutants (POPs) in sediments in
the vicinity of mariculture facilities are limited worldwide including
the PRD. Concentrations of PCBs, polychlorinated dibenzo-p-dioxins
and dibenzofurans (PCDD/Fs), PBDEs, OCPs, and polycyclic aromatic
hydrocarbons (PAHs) in anoxic sediments under fish farm net pens in
New Brunswick were greater than those at other sites (Sather et al.,
2006). Concentrations of PAH in sediments under mariculture facilities
were significantly greater than those in coastal sediments where there
was no mariculture facility (Wang et al., 2010). Those authors suggested that fish feeds might be the main source of the enriched PAHs
in the mariculture sediments.
We hypothesized that OCPs could be greater in sediments near
mariculture facilities in Hong Kong and adjacent mainland China. The
specific objectives were to: (1) characterize concentrations of OCPs in
mariculture surface and core sediments of Hong Kong and adjacent
mainland China; (2) compare the concentrations of OCPs in marine
culture sediments and their corresponding reference sediments; and
(3) evaluate the sources, burden and ecological risks of OCPs in
sediments under mariculture facilities. To our knowledge, this is the
first study to evaluate the differences of OCP contaminations in coastal
sediments between areas with and without mariculture.
2. Materials and methods
215
extracted according to US EPA Standard Method 3540 C (USEPA,
1996) using 100 ml of a mixture of acetone, dichloromethane (DCM)
and n-hexane (1:1:1, v: v: v) for 16 to 18 h at 68 °C. Sufficient
acid-washed copper powder was added to remove sulfur. The extract
solution was concentrated to 2 ml with a rotary evaporator. About
10 ml n-hexane was added and then rotary evaporated to remove
acetone and DCM. The concentrated extract was then cleaned-up by
use of a multilayer silica gel column containing, from top to bottom,
1 g anhydrous sodium sulfate, 2 g of deactivated silica (3% organicfree reagent water, w/w), 8 g of acidic silica (44% concentrated sulfuric
acid, w/w), 1 g of deactivated silica and 1 g of anhydrous sodium. OCPs
were eluted with 90 ml n-hexane/dichloromethane (7:3, v/v). The eluate was then concentrated and passed through a florisil column with
160 ml n-hexane. Deuterated internal standard 2, 4, 5, 6-Tetrachloromxylene (TCmX) was added into all extracts to 100 ng g−1 prior to instrumental analysis for quantification. The final volume for all samples
was 200 μl. OCPs were quantitatively analyzed by a Hewlett-Packard
(HP) 6890 N gas chromatograph (GC) coupled with a HP-5973 mass
selective detector (MSD) and a 30 m × 0.25 mm × 0.25 μm DB-5 capillary column (J & W Scientific Co. Ltd., USA). The mass spectrometry
mode is selected ion monitoring (SIM). An aliquot of the extract
(1 μl) was injected with the aid of an auto sampler (Hewlett-Packard
7683 series). The oven temperature was programmed from 60 °C
(initial time, 1 min) to 290 °C at a rate of 4 °C/min, held for 10 min.
The 10 target OCP compounds included α-HCH, β-HCH, γ-HCH,
δ-HCH, o,p'-DDD, p,p'-DDD, o,p'-DDE, p,p'-DDE, o,p'-DDT and p,p'-DDT.
The standard curve was obtained by injecting standards of 1, 2, 5, 10,
20, and 50 ng OCP ml−1. The limit of detection (LOD) for OCPs was
0.02 ng g−1 in the samples (dry weight, dw). If the concentration of
a congener was less than the LOD, a value equal to half the LOD of
the analytical method was attributed for statistical analysis, while it
was set to zero for sum, mean and median calculations.
2.1. Study area and sampling
2.3. QA/QC
Six cage mariculture farms located at Xixiang (XX), Tsing Yi (TY),
Sam Mun Tsai (SMT), Mirs Bay (MB), Sai Kung (SK) and Tung Lung
Chau (TLC) were chosen for the present study (Fig. S1). Six sampling
sites were chosen for each direction to represent the typical, subtropical
fish farming regions in Hong Kong and adjacent mainland China.
Detailed information for these sampling sites is shown in Table S1.
Total organic carbon (TOC) concentrations in surface sediments
and cores for each sampling site are listed in Tables S2 and S3.
Detailed information on the physical properties of sediments has been
reported previously (Liang et al., 2012). Species cultured in these mariculture “farms” included Red snapper (Lutjanus campechanus), Orangespotted grouper (Epinephelus coioides) and Snubnose pompano
(Trachinotus blochii). In the period of July to 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) samples of sediments were collected from each site. Sediments at mariculture facilities were collected beneath cages, while reference sediments were collected about 1–2 km away from the cage, but
in the general vicinity. The total number of samples of surface sediments was 36 (18 mariculture surface samples and 18 reference surface
samples), and the total number of cores was 36 (18 mariculture core
samples and 18 reference core sediments). Cores of sediments were
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
waste fish (n = 6) and dry pellet feeds (n = 9) were collected from
TLC fish farms. All samples were packed in aluminium foil, transported
to the laboratory and kept at −20 °C until further analyses.
2.2. Identification and quantification of residues
Sediments were freeze-dried, homogenized and stored in desiccators prior to chemical analyses. Samples (2–3 g) were Soxhlet
Surrogate standards (4 4′-dichlorbiphenyl) were added to all
samples prior to extraction to quantify the procedural recoveries. For
each batch of 20 field samples, a method blank (solvent), a spiked
blank (standards spiked into solvent), a matrix spike (standards spiked
into pre-extracted sediment), a sample duplicate, and a standard reference material (SRM 1941) sample from National Institute of Standards
and Technology (NIST) were processed. The method blanks contained
no detectable target analysts. Several quality control criteria were
used to ensure the correct identification and quantization of the target
compounds: first, retention times matched with those of the authentic
reference compounds; second, the ratios of the two characteristic ions
were within 15% of the theoretical values; third, the signal-to-noise
(S/N) ratio was greater than three for the selected ions; fourth, the
amount of the analytes in the sample had to be at least two times that
in the blank sample if there were interferences. If any of these four
criteria failed, the congener was excluded. Measured concentrations
of target analytes in the NIST SRM 1941 were within 76.2–115% of the
certified and reference values. The mean surrogate recovery was
93.7 ± 13.6%. The variance between the duplicate samples all less
than 12%. The LOD using the present method was determined as the
concentrations of analytes in a sample that gave rise to a peak with a
signal-to-noise ratio (S/N) of 3. All the results were not corrected with
the recovery ratios due to the acceptable recovery rates and reported
in ng g−1, dry weight (dw), at three significant figures.
2.4. Data analysis
The ∑HCHs was defined as the sum of α-HCH, β-HCH, γ-HCH and
δ-HCH, ∑DDTs as the sum of o,p'-DDT, p,p'-DDT, o,p'-DDE, p,p'-DDE, o,
p'-DDD and p,p'-DDD, and ∑OCPs as the sum of ∑HCHs and
∑DDTs. The enrichment percentage was calculated according to the
216
H.-S. Wang et al. / Science of the Total Environment 466–467 (2014) 214–220
formula (Duce et al., 1972; Gao et al., 2005; Wang et al., 2011): Eri. =
(CAq. − CRef.) × 100/CRef., where Eri. is the enrichment percentage;
CAq. is the concentration in mariculture sediment; and CRef. is the
concentration in reference sediment.
Statistical analyses of data were performed by use of SPSS 17.0 for
Windows. Normality was confirmed by the Kolmogorov–Smirnov
test. Homogeneity of variances was confirmed using the Levene test.
Data of OCP concentrations in mariculture and reference sediments
were analyzed using two independent t-tests and one-way ANOVA
with Duncan's multiple range test as appropriate.
3. Results and discussion
3.1. Enrichment of OCPs in mariculture surface and core sediments
Concentrations of OCPs in surface sediments under mariculture
facilities were greater than those in sediments from reference locations
and some OCPs exceeded thresholds set by various institutions. In
reference sediments, concentrations of ∑HCHs ranged from 4.24 to
15.5 ng g−1 with a mean of 10.4 ng g−1, while those of ∑DDTs
ranged from 1.59 to 9.57 ng g−1 with a mean of 3.58 ng g−1. Detailed
information concerning OCP contaminations in both mariculture and
reference surface (0–5 cm) sediments of six sampling sites is shown
Table S2. As shown in Fig. 1, the concentrations of ∑HCHs ranged
from 5.62 to 20.4 ng g−1 with a mean of 13.2 ng g−1 in mariculture
surface sediments. The concentrations of ∑DDTs ranged from 9.95
to 44.4 ng g−1 with a mean of 23.9 ng g−1 were much higher than interim sediment quality guidelines (ISQG) target value of 4.48 ng g−1
set by the Canadian Council of Ministers of the Environment (CCME,
1999a) and accounted for 43.0 to 77.0% with a mean of 63.1% of
∑OCPs. Concentrations of ∑DDTs and ∑HCHs in surface sediments
at mariculture facilities were significantly (p b 0.05) greater than that
in reference surface sediments. Mean enrichment percentages for
∑HCHs and ∑DDTs in surface sediments of six mariculture locations
were 34.7 and 676%, respectively. Concentrations of ∑HCHs in surface
sediments under mariculture facilities ranged from 5.62 to 20.4 ng g−1
with a mean of 13.2 ng g−1 (Fig. 1). Concentrations of ∑DDTs ranged
from 9.95 to 44.4 ng g−1 with a mean of 23.9 ng g−1 were greater
than the interim sediment quality guideline (ISQG) target value of
4.48 ng g−1 set by the Canadian Council of Ministers of the Environment (CCME, 1999a) and accounted for 43.0 to 77.0% with a mean of
63.1% of ∑OCPs.
Fig. 1. The concentrations of ∑HCHs and ∑DDTs in mariculture and reference surface
sediments of the PRD. Aq. means mariculture sediments. Ref. means reference sediments.
The number of data for surface and core sediments is 18 and 60, respectively.
Concentrations of OCPs in core sediments under mariculture facilities were also significantly greater than those in sediments from reference locations. Concentrations and vertical distributions of ∑HCHs
and ∑DDTs at the six mariculture sites are shown in Figs. 1 and 2, respectively. The average concentrations of OCPs and their congeners in
the mariculture and reference core sediments are listed in Table S3.
Concentrations of ∑DDTs ranged from 0.92 to 326 ng g−1 with a
mean of 39.3 ng g−1 in sediment cores from mariculture sites. Concentrations of ∑HCHs in sediment cores of mariculture sites ranged from
4.89 to 52.8 ng g−1 with a mean of 14.2 ng g−1 dw. Concentrations of
both ∑DDTs and ∑HCHs were significantly (p b 0.01) enriched in
cores of sediments at mariculture sites relative to the reference sediments, with enrichment percentages ranging from 9.88 to 35.4 with a
mean of 21.9% for ∑HCHs and from 382 to 2.68 × 103 with a mean
of 1.30 × 103% for ∑DDTs, respectively. Enrichment percentages of
o,p'-DDD and p,p'-DDD were significantly greater (p b 0.05) than
those of other OCP congeners, especially in sediment cores of
10–15 cm where the average enrichment percentage was as high as
8.67 × 103% for o,p'-DDD.
3.2. Vertical distribution profiles of OCPs in core sediments
Vertical profiles of organic contaminants in core sediments could
provide useful information about historical trends of contaminant
inputs. As shown in Fig. 2, no significant historical variations of HCHs
in core sediments of both mariculture and reference sites were observed. The results were in line with previous studies also performed
in the PRD (Wei et al., 2008; Zhang et al., 2002).
For ∑DDTs in reference core sediments, the concentrations
displayed decreasing trends with sediment depth except the rebound
trend observed in some sites such as TLC (Fig. 2), revealing that DDT
contamination in natural marine sediments of Hong Kong and
adjacent mainland China shared similar historical inputs with other
coastal sediments in China such as Quanzhou Bay (Gong et al., 2007)
and Daya Bay (Wang et al., 2008). However, significantly (p b 0.01)
higher concentrations of ∑DDTs were recorded at the depth of 10 to
15 cm at SMT, MB and SK, and 20 to 25 cm at XX and TY in mariculture
core sediments. The peak concentrations which appeared in different
depths of the mariculture core sediments were perhaps attributed
to different sedimentation rates. Previous studies suggested that the
sedimentation rate at the west coast of Hong Kong (Deep Bay, 1.3 ±
1.7 cm a−1) was significantly higher than that in the east (0.35 ±
0.56 cm a−1, Hebe Haven; 0.46 ± 0.27 cm a−1) (Zhang et al., 2002).
Considering the sedimentation rates at XX and TY located in the west
coast, were higher than SMT, MB and SK located at the east coast of
Hong Kong, the ∑DDT peak concentrations suggested that the pesticides had been used substantially in the past during mariculture in
the PRD, which was in line with previous studies related to historical
usage of DDTs in this region (Guo et al., 2009a; Wei et al., 2008). The
dated of sediment core is needed to further illustrate the historical
usage of OCPs in the sections of the mariculture sediment cores
analyzed.
One recent study has indicated that the antifouling paint discharge
from fishing boat hull maintenance was the most dominant input
source of DDTs in mariculture sediments collected from Hailing Bay
of Guangdong Province, a major mariculture zone in South China
(Yu et al., 2011c). Therefore, the maximum peak of DDTs at various
sediment depths in the present study may be thus attributable to
the increasing consumption of DDT-containing antifouling paints
with increasing number of fishing boats, prior to the ban on the use
of DDT-bearing antifouling paints in Hong Kong. On the other hand,
the DDT loading has remained basically constant in sediment from
Hailing Bay (Yu et al., 2011b), probably because antifouling paints
from Hailing Bay still contained fairly large amounts of DDTs
compared to those from Hong Kong (Yu et al., 2011a). Because other
factors such as hydrodynamic process and use of fish feeds (frequency
H.-S. Wang et al. / Science of the Total Environment 466–467 (2014) 214–220
217
Concentrations (ng g-1, dw)
40
80
40
80
100
200
300
Depth(cm)
XX
100
200
TY
300
20
40
SMT
60
40
20
Depth(cm)
MB
SK
TLC
Fig. 2. Concentrations of ∑DDTs and ∑HCHs with depth of sediments in mariculture and reference core sediments. Aq. means mariculture sediments. Ref. means reference
sediments.
and amount) could also significantly affect the sedimentation rates of
mariculture core sediments, dating of sediment at each sampling site
would be imperative in future works to understand the historical
DDT usage by coastal mariculture in Hong Kong and adjacent mainland
China.
3.3. Congener composition of OCPs
Congener composition analyses of organic pollutants could provide
useful information about the source of input. The congener compositions of ∑HCHs and ∑DDTs in mariculture and reference surface
sediments are shown in Fig. S2. Our data indicated that β-HCH was
the most abundant isomer of HCHs in both surface mariculture
sediments (16 to 93%, mean of 67%) and reference sediments (20 to
96%, mean of 72%). The ratios of α/β-HCH in both surface mariculture
(0.03 to 2.08, mean of 0.50) and reference (0.02 to 1.57, mean of 0.34)
sediments were much lower than that of technical HCHs (50–70%
α-HCH, 5–14% β-HCH, 10–18% γ-HCH and 6–10% δ-HCH), suggesting
that β-HCH contamination might be due to historical usage and it is
the most hydrophobic isomer (Wang et al., 2008). Furthermore the significant (p b 0.05) higher percentage (4.0 to 63%, mean of 25%) of
γ-HCH as compared to that of technical HCHs found in the sediments,
indicated that there was new input of lindane in the sediments
(Wang et al., 2008), especially SK (61%) and XX (50%).
Due to the significant enrichment of ∑DDTs in both surface and
core mariculture sediments, it is important to understand its congener
compositions. The proportion of p,p'-DDD to ∑DDTs in mariculture
surface sediments (54 to 86%, mean of 70%) was significantly
(p b 0.05) higher than that in reference sediments (33 to 78%, mean
of 55%) (Fig. S2.B). Furthermore, the DDD/DDE ratios in surface mariculture sediments (1.55 to 14.6, mean of 5.98) were also significantly
(p b 0.01) higher than that (0.69 to 7.53, mean of 2.89) in reference
sediments. Similar trends were also recorded in the core sediments.
This indicated that mariculture sediments had much higher degree of
anaerobic conditions which could cause a reductive dechlorination of
DDT to DDD (Sethajintanin and Anderson, 2006). It was further confirmed by the results that the ratios of (DDD + DDE)/DDT in both
mariculture (mean 0.92) and reference (mean 0.85) were much higher
than 0.5, suggesting that DDTs were subjected to long-term weathering
(Hitch and Day, 1992). Furthermore, it is well accepted that the ratios
of (p,p'-DDE + p,p'-DDD)/p,p'-DDTs greater than 0.5 indicate historical
input of DDT, while those less than 0.5 imply recent input (Barakat et
al., 2011; Hong et al., 1999; Sudaryanto et al., 2007). Strandberg et al.
(1998) also suggested that ratios of p,p'-DDT/p,p'-DDE in sediments
higher than 0.5 may indicate recent input of DDT, while the ratios
less than 0.3 suggest past input. Both ratios of (p,p'-DDE + p,p'-DDD)/
p,p'-DDTs (50.0 ± 26.2) and p,p'-DDT/p,p'-DDE (0.12 ± 0.07) suggested that DDTs in mariculture surface sediments were from historical
usage. The ratios o,p'-DDT/p,p'-DDT in mariculture sediments ranged
from 0.16 to 6.69 (2.37 ± 1.60), which suggested a Dicofol source for
DDT contamination in mariculture sediments (Qiu et al., 2005). There
is no linear correlation (p N 0.05) between DDTs (sum of o,p'-DDT
and p,p'-DDT) and ∑DDTs in mariculture sediments of the present
study, reflecting that DDTs were not derived from a single dominant
source (discussed below).
3.4. Sediment burden of OCPs
The enriched mass inventory (EI) of OCPs in the mariculture
sediments could be calculated according to the following formula
(Lin et al., 2009):
EI ¼ ðCAq:−CRef:ÞAdp
H.-S. Wang et al. / Science of the Total Environment 466–467 (2014) 214–220
where CAq. is the concentration in mariculture sediment, CRef. is the concentration in reference sediment, A is the total water area of mariculture
zones in Hong Kong and adjacent mainland China (224.4 km2) (Cao et
al., 2007), d is the assumed sediment density of 1.5 g/cm3 (Lin et al.,
2009), and p is sediment thickness (5 cm for surface and 30 cm for
core sediment).
The total calculated inventories of ∑HCHs and ∑DDTs in mariculture surface sediments of Hong Kong and adjacent mainland
China were 0.22 and 0.40 t, respectively. The calculated enriched
∑HCHs and ∑DDTs in mariculture surface sediments of the PRD
were 4.7 × 10−2 and 0.35 t respectively after subtracted by reference
sediments. For core sediments, data of first 30 cm was employed to
deduce the enriched burden of organochlorines. The calculated
enriched inventories for ∑ HCHs and ∑DDTs were 0.23 and 3.67 t
respectively in mariculture core sediments of the PRD. Although
there were some uncertainties in the estimated OCP inventories
such as the representative of average concentrations in mariculture
and reference sediments, the identification of “enrichment” due to
mariculture, generally, our results indicated that the mariculture sediments were enriched by a large amount of OCPs.
Compound percentage in TLC
mariculture sediments
218
80
β-HCH
p,p’-DDD
60
40
R2=0.71, p<0.05
20
0
0
10
20
30
40
50
Compound percentage in TLC fish feeds
Fig. 3. The correlation of OCP congener proportions (HCH congeners to ∑HCH and
DDT congeners to ∑DDTs) between fish feeds and surface mariculture sediments
collected from TLC. The short dash line represents 1:1 line between the compound
percentage in fish feeds and sediments, whereas points above the line suggest selective
enhancement (positive deviation), otherwise degradation (negative).
3.5. The sources of enriched OCPs
The above results revealed that large amount of OCPs were
enriched in mariculture surface and core sediments. The enrichments
could be attributed to human mariculture activities. Primarily, fish
feed input was expected as the most important source for organic
pollutants in mariculture sediments. High concentrations of OCPs
were observed in fish feed manufactured in the PRD (∑DDTs,
mean of 417 ng g−1 in trash fish and 151 ng g−1 in pellets) (Guo et
al., 2009a) and Hong Kong (∑DDTs, 86.5 to 641 ng g−1 in trash
fish) (Leung et al., 2010). In the present study, concentrations of
∑HCHs and ∑DDTs in fish feeds collected from TLC were 29.8 ±
10.3 and 382 ± 203 ng g−1 in trash fish, and 34.4 ± 7.39 and
95.8 ± 30.1 ng g−1 in commercial dry pellets respectively. The concentrations of these organic pollutants in trash fish and dry pellets
collected from TLC were similar with fish feeds manufactured in the
PRD (Guo et al., 2009a). Fig. 3 shows the composition percentages
of HCHs and DDTs in fish feeds and mariculture surface sediments
collected from TLC. The composition proportion of OCP (excluding p,
p'-DDD) congeners in fish feeds was significantly correlated (R2 =
0.71, p b 0.05) with that in mariculture sediments, but not
(p N 0.05, data now shown) with that in reference sediments. This
revealed that the OCPs (excluding p,p'-DDD) in mariculture sediments
may be principally derived from fish feed inputs. There are two OCP
congeners' proportion values (β-HCH and p,p'-DDD) located above
the short dash line (1:1 line), indicating selective enhancement from
fish feeds to mariculture sediments. For β-HCH, previous studies indicated that this compound had a low vapor pressure and was the
most recalcitrant HCHs in the environment under anaerobic conditions
(Middeldorp et al., 1996). Therefore, the proportion of β-HCH to
∑HCHs in mariculture sediments would be enhanced. The proportion
of DDT to ∑DDTs in fish feeds (mean 28.8%) was significantly
(p b 0.01) higher than that (mean 7.30%) in mariculture surface sediments. It suggested the there is degradation of DDTs inputted by fish
feeds in mariculture sediments.
For p,p'-DDD, the proportion value in mariculture sediments was
4.4 times higher than that in fish feeds (Fig. 3). DDT contained in
fish feeds could be dechlorinated to DDD under anaerobic condition
(Corona-Cruz et al., 1999). Previous studies suggested that antifouling
paint was an important DDT source in the coastal sediments of the
PRD (Lin et al., 2009; Wang et al., 2007). High ∑DDT residues
(0.53–2.36 × 103 μg g−1) were reported in commercially available
antifouling paints in the PRD and about 30–60 Mt of DDT had been
used in the region (Wang et al., 2007). The DDT-based antifouling
paints were largely used to prevent the attachment of marine
organisms such as barnacles and algae on floating rafts. Furthermore,
the DDD/DDE ratios (1.55 to 14.6, mean 5.98) in mariculture surface
sediments were comparable to the data (1.1 to 11.8, mean 4.5)
obtained in fishing harbor sediments contaminated by DDT-based antifouling in the PRD (Lin et al., 2009). Therefore, it seems apparent that
another important source for the enriched DDTs, especially p,p'-DDD,
detected in mariculture sediments was in the form of dechlorinated
DDTs released from antifouling paints under anaerobic conditions,
although it needs further study to compare its contribution with fish
feed inputs. In addition, p,p'-DDD was also used as an insecticide
and applied directly to the water in fish farms to control weeds and
algae and to eliminate fish and invertebrates (Guo et al., 2008;
Sethajintanin and Anderson, 2006). Therefore, the higher proportions
of p,p'-DDD in mariculture sediments may partly stem from direct
inputs.
Previous studies indicated that coastal regions including residential, industrial, and harbor areas showed high OCP concentrations
compared with offshore sites (Hong et al., 2008; Hung et al., 2007).
The enrichment of OCPs in sediment from fish farms could be linked
to the emission of DDTs by fish ships. Elevated levels of DDTs in
harbor regions had also been observed elsewhere (Hong et al., 2006;
Lee et al., 2001). It indicated that shipping industry may also be a
source of DDTs in the mariculture farms in Hong Kong.
3.6. Ecological risk assessment
The overall water area of mariculture in the coastal zone of the
PRD represents a considerable proportion of the total water area
(Lin et al., 2009). Considering that coastal sediment is both a habitat
for aquatic organisms and a reservoir of pollutants, an ecological
risk assessment (ERA) (Chapman, 2002) was conducted in order to
assess the toxicity of surface mariculture and reference sediments
posed to the surrounding marine environment and associated biota.
The sediment quality guidelines specified by the USEPA (1997) and
the Canadian Council of Ministers of the Environment (CCME,
1999a, 1999b) were used to assess the potential ecotoxicological
impacts of these organic pollutants (Table 1). Results indicated that
p,p'-DDD had the largest ecotoxicological risk among all DDT congeners, 72.4% samples were above the probable effect level (PEL) (Long
et al., 1995; Nipper et al., 1998), with the maximum concentration 42
times higher than its PEL value. For total DDT concentrations, 13.8%
samples were above the effect range-medium (ER-M) (Long et al.,
1995; Nipper et al., 1998) value and 79.3% were above the PEL values
H.-S. Wang et al. / Science of the Total Environment 466–467 (2014) 214–220
219
Table 1
Comparison of the concentrations of DDTs and HCHs in the surface mariculture and reference area with the corresponding sediment quality criteria.
OCPs
p,p'-DDT
p,p'-DDD
p,p'-DDE
DDTs
γ-HCHs
Range
ER-L
Aq.
Ref.
0.05–7.49
0.23–302
0.08–26.2
0.61–326
ND-23.5
ND-1.07
0.06–7.43
0.05–2.51
0.47–9.57
ND-6.11
1
2
2.2
1.58
–
% above
ER-L
ER-M
Aq.
Ref.
48.3
79.3
65.5
84.5
–
1.72
20.3
1.69
76.3
–
7
20
27
46.1
–
% above
ER-M
TEL
Aq.
Ref.
3.45
36.2
0
13.8
–
0
0
0
0
–
1.19
1.22
2.07
2.26
0.32
% above TEL
Aq.
Ref.
43.1
82.8
70.7
81.0
98.3
0
42.4
1.69
50.8
84.6
PEL
4.77
7.18
374.17
4.79
0.99
% above PEL
Max (Median) multiple to
PEL
Aq.
Ref.
Aq.
Ref.
8.62
72.4
0
79.3
63.8
0
1.69
0
10.2
52.3
1.57 (0.21)
42.0 (2.21)
0.07 (0.01)
68.0 (4.12)
23.7 (1.41)
0.22 (0.03)
1.03(0.16)
0.01(0.00)
2.00 (0.49)
6.17 (1.05)
ER-L, effect range-low value; ER-M, effect range-medium value; % above ER-L/ER-M, percentage of sample above ER-L/ER-M; TEL, threshold effect level; PEL, probable effect level
(Long et al., 1995; Nipper et al., 1998).
with the maximum concentration 68 times higher than its PEL value.
High percentages of DDTs and γ-HCH exceeding the PEL indicated
that there may be a high potential contaminating surrounding marine
environment leading to adverse effects on the biota associated with
the sediments. Generally, the ecological risks of DDTs and HCHs in
reference sediments were much lower than that of mariculture
sediments. However, more attention should also be paid to Hong
Kong marine sediment contamination because there was more than
50.8% and 84.6% natural marine sediment samples that exceeded the
threshold effect level of DDTs and γ-HCHs, respectively.
The above results suggested that the large amount of OCPs especially p,p'-DDD were enriched in mariculture sediments. There is a great
potential for the enriched OCPs in mariculture sediments to enter
into food chains and finally reach human bodies. The contaminated
sediments are difficult to control and remediate due to technological
and economical reasons (Zhou et al., 2004). Based on the results of
the present study, it is recommended to minimize the sources of
OCPs such as reducing the OCP concentrations in fish feeds, replacing
the DDT-based antifouling paints, removing the unconsumed fish
feeds, etc.
4. Conclusions
The present study investigated the mariculture-derived contamination of HCHs and DDTs in surface and core coastal sediments of Hong
Kong and adjacent mainland China. The enrichment percentages of
∑HCHs and ∑DDTs were 34.7 and 676% respectively in surface mariculture sediments compared with, 21.9 and 1.30 × 103% respectively in
core mariculture sediments. In Hong Kong and adjacent mainland
China, the calculated enriched mass inventories for ∑HCHs and
∑DDTs were 4.7 × 10−2 and 0.35 t respectively in surface mariculture sediments, and 0.23 and 3.67 t respectively in core mariculture
sediments. The enriched organochlorines were mainly derived from
fish feeds, DDT-based antifouling paints, pesticide usage and other
trivial sources. Ecological risk assessment indicated that there was a
potential danger for the enriched organochlorines to contaminate the
surrounding marine environment and associated biota. Considering
the fact that enriched OCPs in mariculture sediments could be eventually accumulated into seafood and exert harmful effects on human
health, it is recommended to control OCPs at source.
Acknowledgments
The authors thank Dr. X. L. Sun and Mr. K.W. Chan for technical
assistance. This research was supported by the National Natural
Science Foundation of China (Grant No. 31101071), the Seed Collaborative Research Fund from the State Key Laboratory in Marine Pollution
(SCRF0003), the National Basic Research Program of China (973 Program, No. 2011CB9358003), the China Postdoctoral Science Foundation
(No. 2012M511868), the Fundamental Research Funds for the Central
Universities (Sun Yat-sen University) (No. 12ykpy09), and the Science
and Technology Planning Project of Guangdong Province, China
(No. 2012B031500005). Prof. Giesy was supported by the Canada
Research Chair program. He was also supported by the 2012 program
of “High Level Foreign Experts” (#GDW20123200120) funded by the
State Administration of Foreign Experts Affairs, the P.R. China to
Nanjing University and the Einstein Professor Program of the Chinese
Academy of Sciences and a Visiting Distinguished Professorship in the
Department of Biology and Chemistry and State Key Laboratory in
Marine Pollution, City University of Hong Kong.
Appendix A. Supplementary data
Two figures showing the sampling sites and congener compositions
of HCHs in mariculture and reference surface sediments are attached.
Three tables showing detailed information of sampling sites, concentrations of HCHs and DDTs in surface mariculture and reference
sediments of each sampling site, and the average vertical distribution
of OCPs in core sediments of Hong Kong are attached. Supplementary
data to this article can be found online at http://dx.doi.org/10.1016/j.
scitotenv.2013.07.027.
References
Alpaslan A, Pulatsü S. The effect of Rainbow Trout (Oncorhynchus mykiss Walbaum,
1792) cage culture on sediment quality in Kesikköprü Reservoir, Turkey. Turk J
Fish Aquat Sci 2008;8:65–70.
Barakat AO, Khairy M, Aukaily I. Persistent organochlorine pesticide and PCB residues in
surface sediments of Lake Qarun, a protected area of Egypt. Chemosphere 2011;90:
2467–76.
Cao L, Wang W, Yang Y, Yang C, Yuan Z, Xiong S, et al. Environmental impact of aquaculture and countermeasures to aquaculture pollution in China. Environ Sci Pollut
Res Int 2007;14:452–62.
CCME. Canadian sediment quality guidelines for the protection of aquatic life: DDT,
DDE and DDE. In Canadian Environmental Quality Guidelines. Winnipeg, MB:
Canadian Council of Ministers of the Environment; 1999a.
CCME. Canadian sediment quality guidelines for the protection of aquatic life: lindane.
In 412 Canadian Environmental Quality Guidelines. Winnipeg, MB: Canadian
Council of Ministers of the 413 Environment; 1999b.
Chapman PM. Ecological risk assessment (ERA) and hormesis. Sci Total Environ
2002;288:131–40.
Corona-Cruz A, Gold-Bouchot G, Gutierrez-Rojas M, Monroy-Hermosillo O, Favela E.
Anaerobic–aerobic biodegradation of DDT (dichlorodiphenyl trichloroethane) in
soils. Bull Environ Contam Toxicol 1999;63:219–25.
Dean RJ, Shimmield TM, Black KD. Copper, zinc and cadmium in marine cage fish farm
sediments: an extensive survey. Environ Pollut 2007;145:84–95.
Duce RA, Quinn JG, Olney CE, Piotrowicz SR, Ray BJ, Wade TL. Enrichment of heavy
metals and organic compounds in the surface microlayer of Narragansett Bay,
Rhode Island. Science 1972;176:161–3.
Gao QF, Cheung KL, Cheung SG, Shin PK. Effects of nutrient enrichment derived from
fish farming activities on macroinvertebrate assemblages in a subtropical region
of Hong Kong. Mar Pollut Bull 2005;51:994–1002.
Gong X, Qi S, Wang Y, Julia EB, Lv C. Historical contamination and sources of organochlorine pesticides in sediment cores from Quanzhou Bay, Southeast China. Mar
Pollut Bull 2007;54:1434–40.
Guo Y, Meng XZ, Tang HL, Zeng EY. Tissue distribution of organochlorine pesticides in
fish collected from the Pearl River Delta, China: implications for fishery input
source and bioaccumulation. Environ Pollut 2008;155:150–6.
Guo Y, Yu HY, Zeng EY. Occurrence, source diagnosis, and biological effect assessment
of DDT and its metabolites in various environmental compartments of the Pearl
River Delta, South China: a review. Environ Pollut 2009a;157:1753–63.
Guo Y, Yu HY, Zhang BZ, Zeng EY. Persistent halogenated hydrocarbons in fish feeds
manufactured in South China. J Agric Food Chem 2009b;57:3674–80.
220
H.-S. Wang et al. / Science of the Total Environment 466–467 (2014) 214–220
Hitch RK, Day HR. Unusual persistence of DDT in some western USA soils. Bull Environ
Contam Toxicol 1992;48:259–64.
Hong HS, Chen WQ, Xu L, Wang XH, Zhang LP. Distribution and fate of organochlorine
pollutants in the Pearl River estuary. Mar Pollut Bull 1999;39:376–82.
Hong SH, Yim UH, Shim WJ, Li DH, Oh JR. Nationwide monitoring of polychlorinated
biphenyls and organochlorine pesticides in sediments from coastal environment
of Korea. Chemosphere 2006;64:1479–88.
Hong SH, Yim UH, Shim WJ, Oh JR, Viet PH, Park PS. Persistent organochlorine residues
in estuarine and marine sediments from Ha Long Bay, Hai Phong Bay, and Ba Lat
Estuary, Vietnam. Chemosphere 2008;72:1193–202.
Hung CC, Gong GC, Chen HY, Hsieh HL, Santschi PH, Wade TL, et al. Relationships
between pesticides and organic carbon fractions in sediments of the Danshui River
estuary and adjacent coastal areas of Taiwan. Environ Pollut 2007;148:546–54.
Kelly BC, Fernandez MP, Ikonomou MG, Knapp W. Persistent organic pollutants in
aquafeed and Pacific salmon smolts from fish hatcheries in British Columbia,
Canada. Aquaculture 2008;285:224–33.
Lee KT, Tanabe S, Koh CH. Distribution of organochlorine pesticides in sediments from
Kyeonggi Bay and nearby areas, Korea. Environ Pollut 2001;114:207–13.
Leung SY, Kwok CK, Nie XP, Cheung KC, Wong MH. Risk assessment of residual DDTs in
freshwater and marine fish cultivated around the Pearl River Delta, China. Arch
Environ Contam Toxicol 2010;58:415–30.
Liang P, Wu SC, Li YC, Li HB, Yu GB, Yu S, et al. The effects of mariculture activities on
the adsorption/desorption and chemical fractionations of mercury on sediments.
Mar Pollut Bull 2012;64:836–43.
Lin T, Hu Z, Zhang G, Li X, Xu W, Tang J, et al. Levels and mass burden of DDTs in
sediments from fishing harbors: the importance of DDT-containing antifouling
paint to the coastal environment of China. Environ Sci Technol 2009;43:8033–8.
Long ER, MacDonald DD, Smith SL, Calder FD. Incidence of adverse biological effects
within ranges of chemical concentrations in marine and estuarine sediments. Environ
Manage 1995;19:81–97.
Mendiguchia C, Moreno C, Manuel-Vez MP, Garcia-Vargas M. Preliminary investigation
on the enrichment of heavy metals in marine sediments originated from intensive
aquaculture effluents. Aquaculture 2006;254:317–25.
Middeldorp PJM, Jaspers M, Zehnder AJB, Schraa G. Biotransformation of alpha-, beta-,
gamma-, and delta-hexachlorocyclohexane under methanogenic conditions. Environ
Sci Technol 1996;30:2345–9.
Nipper MG, Roper DS, Williams EK, Martin ML, Van Dam LF, Mills GN. Sediment toxicity
and benthic communities in mildly contaminated mudflats. Environ Toxicol Chem
1998;17:502–10.
Qiu X, Zhu T, Yao B, Hu J, Hu S. Contribution of dicofol to the current DDT pollution in
China. Environ Sci Technol 2005;39:4385–90.
Sather PJ, Ikonomou MG, Haya K. Occurrence of persistent organic pollutants in
sediments collected near fish farm sites. Aquaculture 2006;254:234–47.
Serrano R, Barreda M, Pitarch E, Hernandez F. Determination of low concentrations of organochlorine pesticides and PCBs in fish feed and fish tissues from aquaculture activities by gas chromatography with tandem mass spectrometry. J Sep Sci 2003;26:75–86.
Sethajintanin D, Anderson KA. Temporal bioavailability of organochlorine pesticides
and PCBs. Environ Sci Technol 2006;40:3689–95.
Strandberg B, van Bavel B, Bergqvist P-A, Broman D, Ishaq R, Naf C, et al. Occurrence,
sedimentation, and spatial variations of organochlorine contaminants in settling
particulate matter and sediments in the northern part of the Baltic Sea. Environ
Sci Technol 1998;32:1754–9.
Sudaryanto A, Monirith I, Kajiwara N, Takahashi S, Hartono P, Muawanah, et al. Levels
and distribution of organochlorines in fish from Indonesia. Environ Int 2007;33:
750–8.
USEPA. Method 3540C: soxhlet extraction. Washington, DC: US Environmental Protection
Agency; 1996.
USEPA. National sediment quality survey, appendix D. Washington, DC: U.S. Environmental Protection 478 Agency; 1997.
Wang J, Guo LL, Li J, Zhang G, Lee CSL, Li XD, et al. Passive air sampling of DDT, chlordane and HCB in the Pearl River Delta, South China: implications to regional
sources. J Environ Monit 2007;9:582–8.
Wang Z, Yan W, Chi J, Zhang G. Spatial and vertical distribution of organochlorine
pesticides in sediments from Daya Bay, South China. Mar Pollut Bull 2008;56:
1578–85.
Wang HS, Liang P, Kang YA, Shao DD, Zheng GJ, Wu SC, et al. Enrichment of polycyclic
aromatic hydrocarbons (PAHs) in mariculture sediments of Hong Kong. Environ
Pollut 2010;158:3298–308.
Wang HS, Du J, Leung HM, Leung AOW, Liang P, Giesy JP, et al. Distribution and source
apportionments of polychlorinated biphenyls (PCBs) in mariculture sediments
from the Pearl River Delta, South China. Mar Pollut Bull 2011;63:516–22.
Wei S, Wang Y, Lam JC, Zheng GJ, So MK, Yueng LW, et al. Historical trends of
organic pollutants in sediment cores from Hong Kong. Mar Pollut Bull 2008;57:
758–66.
Yokoyama H, Abo K, Ishihi Y. Quantifying aquaculture-derived organic matter in the
sediment in and around a coastal fish farm using stable carbon and nitrogen
isotope ratios. Aquaculture 2006;254:411–25.
Yu HY, Bao LJ, Liang Y, Zeng EY. Field validation of anaerobic degradation pathways for
dichlorodiphenyltrichloroethane (DDT) and 13 metabolites in marine sediment
cores from China. Environ Sci Technol 2011a;45:5245–52.
Yu HY, Shen RL, Liang Y, Cheng H, Zeng EY. Inputs of antifouling paint-derived dichlorodiphenyltrichloroethanes (DDTs) to a typical mariculture zone (South China):
potential impact on aquafarming environment. Environ Pollut 2011b;159:3700–5.
Yu HY, Zhang BZ, Giesy JP, Zeng EY. Persistent halogenated compounds in aquaculture
environments of South China: implications for global consumers' health risk via
fish consumption. Environ Int 2011c;37:1190–5.
Zhang G, Parker A, House A, Mai B, Li X, Kang Y, et al. Sedimentary records of DDT
and HCH in the Pearl River Delta, South China. Environ Sci Technol 2002;36:
3671–7.
Zhou W, Anitescu G, Rice P, Tavlarides L. Supercritical fluid extraction–oxidation
technology to remediate PCB-contaminated soils/sediments: an economic analysis.
Environ Prog 2004;23:222–31.
Supporting Information (SI) for
Aquaculture-derived Enrichment of hexachlorocyclohexanes (HCHs) and
dichlorodiphenyltrichloroethanes (DDTs) in Coastal Sediments of Hong Kong
and adjacent mainland China
Hong-Sheng Wang1*, Zhuo-Jia Chen2, Zhang Cheng3, Jun Du1*, Yu-Bon Man3,
Ho-Man Leung3, John P. Giesy4,5,6,7, Chris K. C. Wong3, Ming-Hung. Wong3*
1 Department of Microbial and Biochemical Pharmacy, School of Pharmaceutical Sciences, Sun Yat-sen University, No.132 Waihuandong Road,
University Town, Guangzhou 510006, P. R. China;
2 State Key Laboratory of Oncology in South China, Department of Pharmacy, Sun Yat-Sen University Cancer Center, Guangzhou 510060, China
3 State Key Laboratory in Marine Pollution - Croucher Institute for Environmental Sciences, Hong Kong Baptist University and City University of
Hong Kong, Hong Kong SAR, PR China;
4 Department of Veterinary Biomedical Sciences & Toxicological Center, University of Saskatchewan, Canada
5Department of Biology & Chemistry and State Key Laboratory in Marine Pollution, City University of Hong Kong, Kowloon, Hong Kong, SAR,
China
6 School of Biological Sciences, University of Hong Kong, Hong Kong, SAR, China
7 State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, People’s Republic of
China
* Co-corresponding authors: Dr. H.S. Wang: Tel: +86 20 3994 3024; Email:
whongsh@mail.sysu.edu.cn; Prof. J. Du: Tel: Tel: +86 20 3994 3022; Email:
dujun@mail.sysu.edu.cn; Prof. M.H. Wong: Tel: +852 34117746; Fax: +852
34117743; Email: mhwong@hkbu.edu.hk
Figures:
Figure S1. The map of 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).
Figure S2. The congener compositions of HCHs and DDTs in surface mariculture and reference
sediments at different sampling sites. A: HCHs; B: DDTs.
Tables
Table S1. Detailed information for each mariculture site
Table S2. Detailed information of OCPs (ng g-1, dry wt) enriched in surface (0-5cm) mariculture
and reference sediments at different sites.
Table S3. The average vertical distribution of OCPs (ng g-1, dry wt) in mariculture and reference
sediment cores of the PRD
FIGURE S1. The map of 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).
FIGURE S2. The congener compositions of HCHs and DDTs in surface mariculture
and reference sediments at different sampling sites. A: HCHs; B: DDTs.
TABLE S1 Detailed information for each mariculture site
No.
1
2
3
Site
Xixiang
Tsing Yi
Sam Mun
Tsai
Ab.
XX
TY
SMT
Latitude
22°33.243'N
22°21.047'N
22°27.288'N
Longitude
113°51.738'E
114°03.366'E
114°13.481'E
WD.(m)
5-10
40-50
30-40
4
Mirs Bay
MB
22°33.870'N
114°31.260'E
20-25
5
Sai Kung
SK
22°20.483'N
114°19.043'E
20-30
6
Tung Lung
Chau
TLC
22°15.400'N
Ab. = Abbreviation; WD. = Water Depth
114°17.228'E
20-30
Fish Feed
Descriptions
Trash fish and dry
pellet feed
Located at Pearl River Estuary, which has constantly received discharges
from various industrial and urban centers along the Pearl River during the past
30 years. Black mud sediment.
moist and dry pellet
feed, trash fish feed
moist and dry pellet
feed
Located along the sailing route of cargo vessels. Near 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 load from human activities in the
catchment. Black mud sediment.
Trash fish, moist and
A semi-enclosed bay located in the east coast of Guangdong Province.
dry pellet feed
Relatively unpolluted marine environment (LiuHills, 1998).
trash fish feed, mud
Near the open-sea. Relatively unpolluted marine environment around culture
carp fingerlings
Flour,
bread,
carp fingerlings
cages.
mud
A small island located off the peninsula of Clear Water Bay. Main sources of
pollutants are from cargo vessels in the vicinity.
-1
TABLE S2 Detailed information of OCPs (ng g , dry wt) enriched in surface (0-5cm) mariculture and reference sediments at different sites.
XX
TY
SMT
MB
SK
TLC
AE
Aq.
Ref.
Eri.
Aq.
Ref.
Eri.
Aq.
Ref.
Eri.
Aq.
Ref.
Eri.
Aq.
Ref.
Eri.
Aq.
Ref.
Eri.
α-HCH
4.97
1.89
163
0.67
1.19
-43.8
0.69
0.36
91.5
1.17
1.44
-19.2
1.70
0.68
150
1.23
1.10
12.4
59.0
β-HCH
2.64
1.30
103
4.51
5.76
-21.8
14.8
11.0
35.1
15.2
11.2
35.1
2.71
6.95
-61.1
9.24
11.3
-18.3
12.0
γ-HCH
7.69
3.05
153
0.61
0.94
-35.4
0.69
0.40
70.5
1.17
1.34
-12.9
6.86
0.70
882
2.11
1.45
45.0
184
δ-HCH
0.15
0.04
260
0.05
0.05
-10.6
ND
ND
N
0.06
0.02
190
ND
ND
N
ND
ND
N
N
∑HCHs
15.4
6.27
146
5.83
7.95
-26.6
16.2
11.75
37.9
17.6
14.1
25.1
11.3
8.34
35.2
12.6
13.9
-9.24
34.7
o,p’-DDD
1.1
0.21
436
0.86
0.06
1.94
0.07
1.58
0.26
510
1.15
0.11
982
2.02
0.46
337
p,p’-DDD
14.3
2.06
593
9.81
1.4
602
18.8
0.96
19.3
2.65
630
12.8
0.86
27.9
5.1
446
921
o,p’-DDE
0.13
ND
N
ND
ND
N
ND
ND
N
0.06
ND
N
0.06
ND
N
ND
ND
N
N
p,p’-DDE
1.96
0.57
244
1.76
0.54
225
6.02
0.74
717
3.33
1.04
219
4.17
0.50
738
2.56
0.99
158
384
o,p’-DDT
1.04
0.23
345
0.4
0.35
12.0
0.84
0.15
471
0.87
0.41
113
1.67
0.24
590
1.93
0.47
315
308
p,p’-DDT
2.73
0.22
0.18
0.14
28.9
0.29
0.11
158
0.42
0.17
145
0.4
0.12
228
0.62
0.12
427
352
∑DDTs
21.2
3.33
538
13.1
2.52
417
27.9
2.06
25.6
4.57
460
20.3
1.84
999
35.0
7.18
388
676
∑OCPs
36.6
9.6
281
18.9
10.5
80.8
44.1
13.8
219
43.2
18.7
131
31.6
10.2
210
47.6
21.1
126
175
TOC (%)
4.66
4.25
9.82
3.03
3.35
-9.62
8.44
4.41
91.3
3.96
3.75
5.66
7.86
6.19
26.9
4.29
4.11
4.38
21.4
1.13×
103
1.37×
10
3
2.81×
10
3
1.86×
10
3
1.25×
103
1.40×
103
1.07×
103
Aq. = Mariculture sediments; Ref. = Reference sediments; Eri. = Enrichment percentage; AE= Average Enrichment Percentage; ND=Not Detected; N= Could not be
calculated.; TOC = total organic carbon
TABLE S3 The average vertical distribution of OCPs (ng g-1, dry wt) in mariculture and reference sediment cores of the PRD
0-2.5cm
2.5-5.0 cm
5.0-7.5 cm
7.5-10cm
10-15cm
15-20cm
20-25cm
25-30cm
AE±SD
Aq.
Ref.
Eri.
Aq.
Ref.
Eri.
Aq.
Ref.
Eri.
Aq.
Ref.
Eri.
Aq.
Ref.
Eri.
Aq.
Ref.
Eri.
Aq.
Ref.
Eri.
Aq.
Ref.
Eri.
HCH
1.73
1.03
68.4
1.88
1.34
40.5
1.60
0.96
66.4
1.82
1.16
57.3
2.00
1.18
70.3
2.13
1.13
89.3
2.53
1.33
90.3
2.42
1.04
132
76.8±27
HCH
8.16
7.50
8.87
8.77
7.56
16.1
7.60
8.71
-12.7
7.62
7.92
-3.77
7.13
8.76
-18.6
7.16
7.94
-9.84
8.36
8.19
2.04
5.94
8.33
-28.7
-5.83±14
HCH
3.18
1.14
179
3.39
1.58
114
3.00
1.22
145
3.22
1.19
170
3.41
1.51
126
3.63
1.45
151
2.95
1.89
55.9
4.08
1.39
194
142±43.
HCH
0.06
ND
N
ND
ND
N
0.06
ND
N
ND
ND
N
0.07
ND
N
ND
ND
N
ND
ND
N
0.07
ND
N
N
HCHs
13.1
9.70
35.4
14.1
10.5
34.0
12.3
10.9
12.3
12.7
10.3
23.4
12.6
11.5
9.88
13.0
10.5
22.9
13.9
11.4
21.2
12.5
10.8
16.0
21.9±9.2
-DDD
1.35
0.25
434
1.23
0.17
630
1.75
0.16
4.01
0.42
851
17.9
0.20
0.12
813
2.18
0.13
0.13
2.96
467
14.3
2.21
547
20.4
1.35
52.0
1.75
60.0
1.75
13.58
1.01
1.12
29.5
0.68
0.06
ND
N
0.06
ND
N
0.07
ND
0.08
ND
0.15
ND
0.07
ND
1.25×
103
N
23.5
-DDE
2.87×
103
N
0.11
ND
1.57×
103
2.00×
103
N
2.44
16.8
8.66×
103
3.33×
103
N
1.10
-DDD
1.00×
103
1.42×
103
N
0.09
ND
1.81×
103
4.23×
103
N
(1.97±2.74
103
(2.01±1.36
103
N
-DDE
2.75
0.76
262
3.33
0.67
394
3.82
0.76
405
5.25
0.88
498
10.5
0.72
-DDT
0.55
0.35
54.5
1.08
0.26
311
1.75
0.31
466
1.41
0.18
667
1.38
-DDT
0.36
0.17
109
1.36
0.15
791
0.61
0.12
412
0.78
0.16
391
0.97
DDTs
21.8
4.53
382
21.3
3.50
509
28.4
2.72
944
63.5
3.43
OCPs
34.9
14.2
145
35.4
14.0
152
40.7
13.6
199
76.2
13.7
1.75×
103
454
C(%)
5.68
4.46
27.3
5.53
4.36
26.6
5.27
4.42
19.2
5.03
4.14
21.6
3.11
0.74
320
5.48
0.83
557
3.74
0.49
658
556±34
0.43
1.36×
103
224
0.56
0.24
135
1.12
0.26
329
0.47
0.17
177
295±19
0.14
619
0.48
0.15
226
0.59
0.19
216
0.56
0.10
459
403±22
90.9
3.27
18.9
2.30
722
33.0
2.57
1.60
14.8
31.9
12.8
149
46.9
14.0
1.19×
103
236
36.8
103.5
2.68×
103
601
49.3
12.4
2.19×
103
298
(1.30±0.83
103
279±16
4.93
3.98
23.9
4.32
3.69
16.8
4.32
3.82
13.1
3.86
3.21
20.3
21.1±4.8
Aq. = Mariculture sediments; Ref. = Reference sediments; Eri. = Enrichment percentage; AE±SD = Average Enrichment Percentage ± Standard Deviation; ND=Not
Detected; N= Could not be calculated; TOC = total organic carbon
References:
Liu, J.H. Hills, P., 1998. Sustainability and coastal zone management in Hong Kong - the case of Mirs Bay. Int. J. Sustain. Dev. World Ecol. 5: 11-26.