DSpace at VNU: Persistent organochlorine residues in estuarine and marine sediments from Ha Long Bay, Hai Phong Bay, and Ba Lat Estuary, Vietnam

Chemosphere 72 (2008) 1193–1202

Contents lists available at ScienceDirect

Chemosphere
journal homepage: www.elsevier.com/locate/chemosphere

Persistent organochlorine residues in estuarine and marine sediments
from Ha Long Bay, Hai Phong Bay, and Ba Lat Estuary, Vietnam
S.H. Hong a,*, U.H. Yim a, W.J. Shim a, J.R. Oh a, P.H. Viet b, P.S. Park a
a
b

South Sea Research Institute, Korea Ocean Research and Development Institute, 391 Jangmok-ri, Jangmok-myon, Geoje-shi 656-834, Republic of Korea
Vietnam National University, 334 Nguyen Trai Street, Thanh Xuan District, Hanoi, Viet Nam

a r t i c l e

i n f o

Article history:
Received 18 July 2007
Received in revised form 21 February 2008
Accepted 25 February 2008
Available online 28 April 2008

Keywords:
Organochlorine pesticides
PCBs
Marine sediment
Contamination

Vietnam

a b s t r a c t
To assess the organochlorine contamination in the northeast coastal environment of Vietnam, a total of
41 surface sediments were collected from Ha Long Bay, Hai Phong Bay, and Ba Lat estuary, and analyzed
for their organochlorine content. Organochlorine compounds (OCs) were widely distributed in the Vietnamese coastal environment. Among the OCs measured, DDT compounds predominated with concentrations ranging from 0.31 to 274 ng gÀ1. The overall contamination level of DDTs in coastal sediments from
northern Vietnam is comparable with those from other Asian countries. However, concentrations exceeding 100 ng gÀ1 are comparable with high concentrations reported from India and China, the largest DDT
consumers in the world. The overall concentrations of PCBs, HCHs, and chlordanes in surface sediments
were in the ranges of 0.04–18.71 ng gÀ1, not detected (n.d.) – 1.00 ng gÀ1, and n.d. – 0.75 ng gÀ1, respectively. Ha Long Bay and Hai Phong Bay were relatively more contaminated with DDTs and PCBs than other
regions, respectively. In contrast, the distribution of HCHs was relatively homogeneous. OCs contamination in the coastal environment of Vietnam is closely related to shipping and industrial activities. The levels of DDT compounds in harbors and industrial areas exceeded their sediment quality guideline values
suggested by Environment Canada [CCME (Canadian Council of Ministers of the Environment), 2002.
Canadian sediment quality guidelines for the protection of aquatic life. In: Canadian Environmental Quality Guidelines. Canadian Council of Ministers of the Environment, Winnipeg, MB] and Australian and New
Zealand [ANZECC and ARMCANZ, 2000. National water quality management strategy. Paper No. 4, Australian and New Zealand Guidelines for Fresh and Marine Water Quality, vol. 1, The Guidelines. Australia.
Document: indicating that adverse effects
may occur to marine species in that areas.
Ó 2008 Elsevier Ltd. All rights reserved.

1. Introduction
Persistent organic pollutants (POPs) such as polychlorinated
bipenyls (PCBs) and organochlorine pesticides have been recognized as one of the most problematic groups of anthropogenic
chemicals for the last few decades. A number of studies have reported their harmful effects on reproduction, development, and
immunological function in humans and wildlife (Fry and Toone,
1981; Podreka et al., 1998; Vallack et al., 1998). POPs are semivolatile and can therefore travel long distances through the
atmosphere as gases or aerosols, eventually accumulating in lowtemperature regions following condensation and deposition.
Increasing evidence indicates that pristine polar regions are widely
contaminated with POPs which probably come from low- and midlatitudes (Pacyna, 1995; Oehme et al., 1996; Bard, 1999). Industrial
organic chemicals such as PCBs have been mainly consumed in and
* Corresponding author. Tel.: +82 55 639 8674; fax: +82 55 639 8689.
E-mail address: (S.H. Hong).
0045-6535/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.

doi:10.1016/j.chemosphere.2008.02.051

emitted from; mid-latitudinal regions of the Northern hemisphere
because many developed countries are located in this region (Breivik et al., 2002). In the case of organochlorine pesticides, most global emissions are sourced in tropical and sub-tropical developing
countries, where they are used for agricultural and malaria control
purposes; emissions are lower from developed countries following
a ban on these pesticides in the 1970s. Recent investigations reveal
that global emissions of a-HCH and b-HCH have undergone a
southward trend for the last 20 years as more northern countries
have banned the use of technical HCH (Li et al., 2000, 2003).
Vietnam is a developing country located in a tropical region.
Agriculture, which employs approximately 80% of its inhabitants,
is the most important economic sector in Vietnam (Hung and Thiemann, 2002). By virtue of their low cost and high insecticidal efficacy, large amounts of organochlorine pesticides have been applied
to agriculture in order to increase crop yields (Hung and Thiemann,
2002). Additionally, by virtue of suitable climatic conditions, Vietnam had the world’s fifth-highest malaria incidence outside of
Africa until 1992 (Tenenbaum, 1996). Hence, a huge quantity of


1194

S.H. Hong et al. / Chemosphere 72 (2008) 1193–1202

regions of Vietnam, including one industrialized bay (Hai Phong
Bay), one World Heritage site (Ha Long Bay) and a large river
mouth (Ba Lat estuary) to evaluate contamination status and characteristics of organochlorine pesticides and PCBs.

insecticides has been widely sprayed in the Vietnamese environment for malaria vector control.
Application of such chemicals in the Vietnamese environment
can influence global pollution as Vietnam is located in a high-temperature region. Li et al. (2000, 2003) proposed that Vietnam has
been a dominant contributor to the global emission of a-HCH

and b-HCH since China banned the use of technical HCH in 1983.
Thus, understanding the POPs contamination in Vietnam is important for understanding global pollution by POPs. Monitoring studies have already been conducted to assess the contamination
status of POPs in Vietnam (Nhan et al., 1998, 1999, 2001; Hung
and Thiemann, 2002; Minh et al., 2002, 2004). Although the use
of DDT was officially banned in Vietnam in 1995, based on high
levels of DDTs found in humans and wildlife, other researchers
have suggested that DDTs are still in use (Nhan et al., 1998; Minh
et al., 2002, 2004). Although many approaches have been tried to
assess POPs pollution in Vietnam more recently, the earlier studies
were limited in extent, particularly for the marine environment,
with only a few sampling stations. In this investigation, we have
undertaken intensive sediment sampling in three northeast coastal

2. Materials and methods
2.1. Study areas and sampling strategy
Ha Long Bay has been recognized by UNESCO as a World Heritage Area for its universal values of landscape, geology and geomorphology. As the surrounding cities of the bay are rapidly
developing due to the expansion of tourism and ports, the authorities have had increasing management difficulties, especially in
environmental protection.
The sea territories of Hai Phong are part of the north-eastern
water area of Gulf of Tonkin. Hai Phong has a dense network of rivers with an average density of 0.6–0.8 km of river per 1 km2. Recently, industrial activities like coal mining, ship-building and
ship-repairing have caused geological and environmental changes

Table 1
Geographical information of sediment sampling sites and the concentrations (ng gÀ1 dry wt) of PCBs and organochlorine pesticides in sediments from Ha Long Bay, Hai Phong Bay,
and Ba Lat Estuary
Location

Type

Year

PCBs

DDTs

HCHs

Chlordanes

Aldrin

Dieldrin

Endrin

Mirex

TOC (%)

Particle composition (%)
Sand

Silt

Clay

Ha Long Bay
HL1
H
HL2

O
HL3
O
HL4
O
HL5
O
HL6
O
HL7
O
HL8
O
HL9
O
HL10
O
HL11
H
HL12
R
HL13
R
HL14
R
HL15
H
HL16
H

2003
2003
2003
2003
2003
2003
2003
2003
2003
2003
2004
2004
2004
2004
2004
2004

0.56
0.35
0.18
0.42
1.23
0.11
0.51
0.32
0.32
0.42
0.53
2.40
2.22

3.49
10.1
2.71

4.09
1.82
2.04
1.88
6.34
5.93
1.82
1.22
2.40
1.60
2.39
21.3
6.66
13.8
274
12.97

0.19
0.20
0.10
0.14
0.22
0.08
0.14
0.13
0.13

0.16
0.09
0.64
n.d.
0.28
0.85
0.20

n.d.
n.d.
0.02
n.d.
n.d.
n.d.
0.01
n.d.
0.01
0.04
0.02
0.18
0.54
0.12
0.75
n.d.

n.d.
n.d.
n.d.
n.d.
n.d.

n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.

n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
0.06
0.20
0.31
n.d.
1.05
0.09

n.d.

n.d.
n.d.
n.d.
n.d.
n.d.
0.01
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.

n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
0.03
n.d.
n.d.
0.02
0.04
n.d.
n.d.

0.66
0.11

1.40
1.43
1.01
1.23
2.30
1.11
1.36
1.36
1.41
1.25
2.07
3.00
3.61
6.38
4.83
4.64

7
2
13
13
16
25
5
50
5
21

63
1
7
17
4
23

36
41
41
38
41
39
32
14
36
40
14
35
32
36
38
35

57
57
46
49
44
36

63
36
59
39
24
64
61
47
58
42

Hai Phong Bay
HP1
H/I/F
HP2
H/I/F
HP3
H/I/F
HP4
H/I/F
HP5
H/I/F
HP6
H/I/F
HP7
H/I/F
HP8
E
HP9
E

HP10
O
HP11
O
HP12
O
HP13
O
HP14
O
HP15
O

2004
2004
2004
2004
2004
2004
2003
2003
2003
2003
2003
2003
2003
2003
2003

1.87

11.2
1.63
2.15
18.7
4.35
3.16
1.50
1.98
1.97
0.95
1.34
1.75
14.9
0.45

2.26
2.71
5.04
4.12
126
5.69
2.39
3.41
2.70
3.26
2.46
2.00
1.81
1.95
1.76

0.31
1.00
0.15
0.37
0.47
0.21
0.28
0.18
0.21
0.40
0.19
0.16
0.25
0.25
0.22

0.01
n.d.
0.01
0.01
0.10
0.02
n.d.
n.d.
n.d.
n.d.
n.d.
0.01
0.10

n.d.
n.d.

n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
0.03
n.d.
n.d.

0.06
n.d.
0.05
0.08
0.21
0.06
n.d.
n.d.
n.d.
n.d.
n.d.

n.d.
n.d.
0.04
n.d.

n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
0.01
n.d.
n.d.
n.d.
n.d.
n.d.

0.02
0.02
0.11
n.d.
n.d.
n.d.
n.d.
0.02
0.04

0.04
n.d.
n.d.
n.d.
n.d.
n.d.

1.63
0.71
1.13
1.37
1.32
1.61
1.18
1.07
1.10
1.31
1.17
0.93
1.28
0.95
1.14

12
16
6
6
27
8
27

42
12
3
19
36
31
14
28

57
59
53
59
44
56
47
31
60
58
50
35
42
46
32

32
25
41
35
29

35
26
27
28
39
31
29
27
40
41

Ba Lat Estuary
BL1
E
BL2
E
BL3
E
BL4
E
BL5
E
BL6
E
BL7
E
BL8
E
BL9
E

BL10
E

2004
2004
2004
2004
2004
2004
2004
2004
2004
2004

0.18
0.10
0.09
0.13
0.11
0.16
0.13
0.04
0.04
0.26

0.94
0.89
0.81
0.94
0.82

1.12
0.78
0.31
1.46
1.03

0.06
0.10
0.03
0.07
0.10
0.14
0.14
0.04
0.26
0.13

n.d.
n.d.
0.04
n.d.
n.d.
0.01
n.d.
0.01
n.d.
n.d.

n.d.
n.d.

n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.

n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.

n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.

0.01
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.

1.17
0.68
0.34
0.62
0.44
1.20
0.53
0.58
0.42
0.59

2
22
47
28
59
18
25

35
23
12

66
44
35
53
24
59
51
45
54
66

32
34
19
19
17
23
24
20
23
21

R, residential area; H, harbor; F, Farm; I, industrial area; E, estuary; O, open water; n.d., not detected.


1195

S.H. Hong et al. / Chemosphere 72 (2008) 1193–1202

2.2. Analytical procedure

in this region. In addition, coastal water quality has degraded due
to pesticide use and the discharge of domestic and industrial waste
water. Ba Lat estuary (Red River mouth) is one of the biggest river
estuaries and is a unique Ramsar site in Vietnam. The estuary area
is well-known as being the wetland site with the highest biodiversity in the country, and the Red River has a high turbidity, especially during the rainy season. There is only limited data on the
water quality from the flooded area of the Ba Lat estuary.
Surface sediment samples were collected from Ha Long Bay, Hai
Phong Bay and Ba Lat estuary in May 2003 and March 2004. A total
of 41 surface sediment samples were taken using a Van veen grab
on a ship (Table 1 and Fig. 1). In Ha Long Bay, sampling sites included a coastal area where pollution is problematic, and a relatively pristine area close to the open sea. In Hai Phong Bay,
sampling was conducted along the Cam River from the main
stream to its estuary. In Ba Lat estuary, samples were collected at
the Red River mouth. In each case approximately 2 cm of sediment
was removed from the surface, and stored at À20 °C until later
analysis.

Chemical analysis of OCs followed the method previously described by Hong et al. (2003, 2006). Briefly, 20 g sediment samples
were homogenized with anhydrous Na2SO4 and extracted in a
Soxhlet apparatus with dichloromethane. Activated copper granules were used to remove elemental sulfur. Copper treated extracts
were cleaned using 20 g of 5% deactivated silica gel and 10 g of 1%
deactivated alumina in a multilayer column. The samples were
then fractionated using high pressure liquid chromatography
(HPLC) with a size-exclusion column (250 Â 22.5 mm i.d., sizeexclusion column packing with Phenogel 100 Å, Phenomenex
Co.). The OC fractions were concentrated and solvent-exchanged
with n-hexane. Finally, quantitative analysis of OCs was carried

out using a Hewlett-Packard 5890 gas chromatograph (GC) with
a l-electron capture detector (ECD). A fused silica capillary column
(DB-5, 30 m  0.25 mm i.d. with 0.25 lm film thickness) (J&W Scientific, California, USA) was used. Helium and argon:methane
(95:5) were used as carrier and make-up gasses, respectively. The

21º 01'N
N

(a) Ha Long Bay
Lang Bang
Dong Vang

11

Vietnam

1

20º 55''

2
Hanoi

12
13

3

Hon
Gay

14 15
5

16

4
8
6
7

10
9

20 º 49''

Gia Luan

106º 57'E

107 º 07'

107 º 02'

(b) Hai Phong Bay

(c) Ba Lat Estuary
20º 24'N

20º 54'N

Thuy U

1
2
3

4

5

6

Hai Phong

7
8
11

2

3

20º 48''

20º 18'N

9
1

5
4
8

6
7
9
10

10
13

15

20º 42''

20º 12'N

Nghoung Nhan

14

12

106º 24'E

106º 30'E

106º 36'E

106º 42'E

106º 36'E

106º 45''

106º 54'

Fig. 1. Locations of sediment sampling sites in Ha Long Bay, Hai Phong Bay, and Ba Lat estuary, Vietnam. Squares represent bays with multiple sites.


1196

S.H. Hong et al. / Chemosphere 72 (2008) 1193–1202

temperature program during the run was as follows: 100 °C for
1 min, 100 °C to 140 °C at 5 °C minÀ1, 140 °C for 1 min, 140 °C to
250 °C at 1.5 °C minÀ1, 250 °C for 1 min, 250 °C to 300 °C at 10 °C
minÀ1, and 300 °C for 5 min. Injector and detector temperatures
were maintained at 275 °C and 300 °C, respectively.
A mixture of dibromooctafluorobiphenyl, PCB103, and PCB198
was added to all samples as a surrogate standard before extraction.
Tetrachloro-m-xylene was added to all samples prior to GC analysis. The calibration standard consisted of 22 individual PCB congeners (IUPAC No. 8, 18, 28, 29, 44, 52, 66, 87, 101, 105, 110, 118,
128, 138, 153, 170, 180, 187, 195, 200, 206, and 209) and organochlorine pesticides (DDT compounds, HCH compounds, chlordane
compounds, aldrin, dieldrin, endrin, and mirex; Ultra Scientific
Co.). The concentration of analytes was adjusted with the surrogate
standard recovery.
Recoveries of three surrogate standards (n = 41) were 72 ± 6%,
85 ± 10%, and 95 ± 14% for DBOFB, PCB103, and PCB198, respectively. If the recovery of surrogate standards was outside of the
60 to 130% ranges, the sample was reanalyzed. A procedural blank

was run with every set of 14 samples to check for secondary contamination. Quality assurance for the analysis was confirmed by
analysis of certified reference materials, EC-4, 1941a, and IAEA417, provided by Environment Canada, the National Institute of
Standards and Technology (NIST), and the International Atomic Energy Agency, respectively. All analytical values were within the
certified ranges. The detailed results of the certified reference
material analysis have been reported elsewhere (Hong et al.,
2003). The method detection limit of organochlorine compounds are in the ranges of 0.005–0.02 ng gÀ1 for PCB congeners,
0.005–0.02 ng gÀ1 for DDT compounds, 0.01–0.03 ng gÀ1 for HCH
compounds, 0.005–0.02 ng gÀ1 for chlordane compounds, and
0.005–0.04 ng gÀ1 for the other organochlorine pesticides.
All concentration data are based on dry weight. Total PCB concentrations were calculated by summing the 22 individual congeners listed above. Total DDT concentrations (DDTs) are the sum of
o,p0 -DDE, p,p0 -DDE, o,p0 -DDD, p,p0 -DDD, o,p0 -DDT, and p,p0 -DDT.
Total HCH concentrations (HCHs) are the sum of a-HCH, b-HCH,
c-HCH, and d-HCH. Total chlordane concentrations are the sum of
a-chlordane, c-chlordane, cis-nonachlor, and trans-nonachlor.
For measurement of total organic carbon (TOC), the sub-samples of sediments were freeze-dried (LABCONCO, Model 77545)
and ground on a mortar. The samples were acidified with 10% (v/
v) hydrochloric acid and dried again at 50 °C in an oven. Organic
carbon was measured on a CHNS analyzer (Flash EA1112) at combustion temperature of 900 °C. Grain-size analysis was carried out
using standard sieving methods for particles larger than 64 lm and
by pipetting for particles smaller than 64 lm (Carver, 1971).

3. Results and discussion
Organochlorine compounds were shown to be ubiquitously distributed in the northeast coastal environment of Vietnam. PCB,
DDT, and HCH compounds were detected in most sediment samples. Chlordanes were detected in about half of the samples, while
aldrin, endrin, dieldrin, and mirex were detected in less than 30% of
the samples. Among the target organochlorine pesticides measured,
DDT compounds were the predominant contaminant with concentrations ranging from 0.31 to 274 ng gÀ1 (Table 1 and Fig. 2). PCBs
were in the concentration range of 0.04–18.71 ng gÀ1. HCHs,
chlordanes, dieldrin, aldrin, endrin, and mirex were present at relatively low concentrations, in the ranges: n.d.–1.00 ng gÀ1, n.d.–
0.75 ng gÀ1, n.d.–1.05 ng gÀ1, n.d.–0.03 ng gÀ1, n.d.–0.01 ng gÀ1,

and n.d.–0.66 ng gÀ1, respectively.
DDTs: The dominance of DDT compounds found in estuarine
and marine environment has also been observed in inland Vietnam

such as in freshwater canals and rivers (Nhan et al., 2001; Hung
and Thiemann, 2002; Hung et al., 2004). Minh et al. (2002, 2004)
also observed high levels of DDTs in human breast milk and resident bird tissues, which they suspect is due to recent usage of
DDT in Vietnam. Judging by results of POPs monitoring conducted
in Vietnam to date, DDT is predominant POP in the Vietnamese
environment. DDT has been used as the main insecticide for malaria control in Vietnam. It is estimated that 24,042 tons of DDT were
used for malaria-vector control from 1957 to 1994 in Vietnam
(Hung and Thiemann, 2002). Following the Vietnamese government’s adoption of a DDT-free malarial control program in 1991
(WHO, 2000), DDT usage has sharply decreased. However, it is still
suspected that DDTs are used for crop protection and insect control
(Hung and Thiemann, 2002). Agricultural application has been another major contributor to DDT contamination in Vietnam, which
is one of the biggest rice exporters in the world (Tenenbaum,
1996).
In Asia, DDT is a ubiquitous contaminant through various environmental matrices. In particular, the dominance of DDT compounds among POP chemicals is common in developing Asian
countries including Vietnam, China, Thailand, and India (Hong
et al., 1999; Monirith et al., 2003). However, a different situation
is found in industrialized Asian countries such as Japan, Singapore
and South Korea (Monirith et al., 2003; Wurl and Obbard, 2005;
Hong et al., 2006), where industry-related chemicals such as PCBs
are present at high levels. The Asian Mussel Watch initiative by
Monirith et al. (2003) revealed that Vietnam, along with Hong Kong
and China, is one of the three countries having the highest DDT concentrations among 12 Asia-Pacific countries. Minh et al. (2002) also
reported that resident birds accumulated large quantities of DDTs
in comparison to migrants in Vietnam. DDT levels in human breast
milk from Vietnam ranked the highest among those reported from
Asian countries (Minh et al., 2004). All these studies indicate that

Vietnam is one of the more strongly DDT contaminated countries
in Asia. To see whether this characteristic is observed in the marine
and estuarine sediment as well, we compared DDT concentrations
determined in this study with those reported from other Asian
countries in Fig. 3. China and India, the world’s third and the sixth
largest consumers of DDT for agriculture, respectively (Li and Macdonald, 2005), showed the highest DDT concentrations among the
nine Asian countries. The overall level of DDTs in Vietnam is lower
than those in China and India. However, the highest DDT concentrations in Ha Long Bay and Hai Phong Bay exceed 100 ng gÀ1 and are
comparable with the high concentrations reported from those two
countries (Hong et al., 1995; Pandit et al., 2001; Mai et al., 2002).
Except for these contaminated sites, general DDT levels in Vietnam
are comparable to those of Hong Kong, Taiwan, and Singapore
(Richardson and Zheng, 1999; Doong et al., 2002; Wurl and Obbard,
2005). The level of DDTs in the coastal sediment of Vietnam is higher than those of South Korea (Hong et al., 2006) and Japan (Iwata
et al., 1994). Although United States (US) had been the world’s largest consumer of DDT (Li and Macdonald, 2005), the level of DDTs in
the US coastal sediments ( />data/index.html) is relatively lower than those in tropical Asian
countries, which could be due to the early restriction of DDT in
US compared to tropical Asian countries. Meanwhile, Mediterranean coasts of France showed elevated levels of DDTs (Wafo et al.,
2006; Gómez-Gutiérrez et al., 2007) even though their early ban
of DDT.
The spatial distribution of DDTs indicates that DDT contamination is closely related to human activities. Coastal regions including
residential, industrial, and harbor areas showed high DDT concentrations compared with offshore sites (Table 1 and Fig. 2). Interestingly, two top ranked sites, HL15 and HP5, are located in harbor
regions. The high DDT concentration in harbor regions could be
linked to the emission of DDTs by ships. DDT is known to have


1197

S.H. Hong et al. / Chemosphere 72 (2008) 1193–1202

PCBs (ng g -1 dw)

20

1800
1600
1400
1200
1000

15

400

5

200

0

0
HL1
HL2
HL3
HL4
HL5
HL6
HL7
HL8
HL9

HL10
HL11
HL12
HL13
HL14
HL15
HL16
HP1
HP2
HP3
HP4
HP5
HP6
HP7
HP8
HP9
HP10
HP11
HP12
HP13
HP14
HP15
BL1
BL2
BL3
BL4
BL5
BL6
BL7
BL8

BL9
BL10

10

PCBs (ng g -1 TOC)

a

Site
15000

300
200
100

10000
5000

30
800
600
400
200
0

20
10
HL1
HL2

HL3
HL4
HL5
HL6
HL7
HL8
HL9
HL10
HL11
HL12
HL13
HL14
HL15
HL16
HP 1
HP 2
HP 3
HP 4
HP 5
HP 6
HP 7
HP 8
HP 9
HP10
HP11
HP12
HP13
HP14
HP15
BL1

BL2
BL3
BL4
BL5
BL6
BL7
BL8
BL9
BL10

0

DDTs (ng g -1 TOC)

DDTs (ng g -1 dw)

b

Site
200

HCHs (ng g -1 dw)

2.5
2.0

150

1.5
100

1.0
50

0.5

0
HL1
HL2
HL3
HL4
HL5
HL6
HL7
HL8
HL9
HL10
HL11
HL12
HL13
HL14
HL15
HL16
HP 1
HP 2
HP 3
HP 4
HP 5
HP 6
HP 7
HP 8

HP 9
HP10
HP11
HP12
HP13
HP14
HP15
BL1
BL2
BL3
BL4
BL5
BL6
BL7
BL8
BL9
BL10

0.0

HCHs (ng g -1 TOC)

c

d

γ-HCH/Total HCHs

7

120

6

100

TOC (%)

5

80

4

60

3

40

2

20

0

0
HL1
HL2
HL3

HL4
HL5
HL6
HL7
HL8
HL9
HL10
HL11
HL12
HL13
HL14
HL15
HL16
HP 1
HP 2
HP 3
HP 4
HP 5
HP 6
HP 7
HP 8
HP 9
HP10
HP11
HP12
HP13
HP14
HP15
BL1
BL2

BL3
BL4
BL5
BL6
BL7
BL8
BL9
BL10

1

Slit & Clay (%)

Site

Site
Fig. 2. Spatial distribution of organochlorine compounds and sediment parameters in surface sediments from Ha Long Bay, Hai Phong Bay, and Ba Lat Estuary. (a) PCBs, (b)
DDTs, (c) HCHs, and (d) TOC content and particle size of sediment.

been used as a biocide in antifoulants in the past. Recently, UNEP
reported that China is still using DDT as an active ingredient for
antifouling ship paint ( The enhanced level of DDTs
around harbor regions has also been found elsewhere (Lee et al.,
2001; Barakat et al., 2002; Hong et al., 2006). Therefore, this suggests that the shipping industry may be a source of DDTs in the
Vietnamese coastal environment, along with agricultural and disease control activities. Among the sites surveyed, coastal regions
of Ha Long Bay showed the highest level of DDTs (Table 1 and
Fig. 2). Numerous shipping and port facilities for tourism, fishery,

and cargo transport seem to be a local source of DDTs in the Ha
Long Bay. On the other hand, in the relatively pristine Ba Lat estuary, levels of DDTs were much lower than those reported in Hanoi,

which reaches levels of 7.4–80.5 ng gÀ1 (Nhan et al., 2001).
Concentrations of DDT and its metabolites, DDD and DDE,
were in the ranges of 0.07–143 ng gÀ1, 0.30–98.8 ng gÀ1 and
0.05–37.7 ng gÀ1, respectively. DDD showed the highest mean
concentration (6.68 ± 0.12 ng gÀ1) and was followed by DDT
(4.44 ± 0.13 ng gÀ1) and DDE (1.96 ± 0.05 ng gÀ1). Metabolites
account for 78 ± 13% of total DDTs (Fig. 4a), implying that degradation of the parent compound occurs in the Vietnamese marine


1198

S.H. Hong et al. / Chemosphere 72 (2008) 1193–1202

a

10000

100

(ng g-1 dw)

Total DDT Concentration

1000

10

1

0.1

M
ed
US
ite
A
rra
(6
ne
55
an
)
co
as
t(
44
)
Ch
ina
(1
18
)
In
dia
(
88
Sr
)
iL
an

ka
Ho
(5
ng
)
Ko
ng
(2
1)
Ta
iw
an
Si
(1
ng
9)
ap
or
e(
13
)
Ja
So
pa
uth
n(
3)
Ko
rea
Ha

(
13
Lo
8)
ng
Ha
Ba
iP
y(
ho
16
ng
)
Ba
Ba
y(
La
15
tE
)
stu
ary
(1
0)

0.01

Vietnam
(This study)

Other Countries

Location

b

10000

1000

(ng g-1 dw)

Total HCH Concentration

100

10

1

0.1
Median;
n.d.

0.01

M
ed
US
ite

A
rra
(6
ne
55
an
)
co
as
t(
39
Ch
)
ina
(1
18
)
In
dia
(8
Sr
8)
iL
a
n
Ho
ka
ng
(5
)

Ko
ng
(2
1)
Ta
iw
an
Si
(1
ng
9)
ap
or
e(
13
)
Ja
So
pa
uth
n(
3)
Ko
rea
Ha
(1
Lo
38
)
ng

Ha
Ba
iP
y
ho
(1
ng
6)
Ba
Ba
y(
La
15
tE
)
stu
ary
(1
0)

0.001

Other Countries

Vietnam
(This study)

Location
Fig. 3. Comparison of the concentrations of (a) DDTs and (b) HCHs in coastal sediments from Vietnam and other countries. The number of data for each country is presented
in parentheses. In the box plots, the horizontal lines denote the 25th, 50th, and 75th percentile values. The error bars denote the 10th and 90th percentile values. The dotted

lines denote mean values. Reference: USA – National Coastal Assessment (Northeast) and EMAP (West Coast) ( Mediterranean coast – Fernandez et al. (1999), Catsiki et al. (2004), Wafo et al. (2006); China – Hong et al. (1995, 1999), Yuan et al. (2001), Zhou et al. (2001), Mai et al. (2002),
Yang et al. (2005); India – Pandit et al. (2001), Bhattacharya et al. (2003), Guzzella et al. (2005), Rajendran et al. (2005); Sri Lanka – Guruge and Tanabe (2001); Hong Kong –
Richardson and Zheng (1999); Taiwan – Doong et al. (2002); Singapore – Wurl and Obbard (2005); Japan – Iwata et al. (1994); South Korea – Hong et al. (2006).


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S.H. Hong et al. / Chemosphere 72 (2008) 1193–1202

a

o,p'-DDE
p,p'-DDE
o,p'-DDD
p,p'-DDD
o,p'-DD T
p,p'-DD T

Ba Lat Estuary

Hai Phong Bay

Ha Long Bay

0

20

40

60

80

100

Percent composition (%)

b

α-HCH
β-HCH
γ-HCH
δ-HCH

Ba Lat Estuary

Hai Phong Bay

Ha Long Bay

0

20

40

60

80

100

Percent composition (%)

c

Di
Tri
Tetra
Penta
Hexa
Hepta
Octa
Nona
Deca

Ba Lat Estuary

Hai Phong Bay

Ha Long Bay

0

20

40

60

80

100

Percent composition (%)
Fig. 4. Relative composition of (a) DDTs, (b) HCHs, and (c) PCBs in sediment from Ha Long Bay, Hai Phong Bay, and Ba Lat estuary, Vietnam.

environment. However, relatively elevated composition of DDT
(above 50%) found in station HL15 indicates that there still exists
fresh input of DDT in this region.
HCHs: HCH compounds are one of the most widely distributed
organochlorine pesticides in the Vietnamese marine sediment.
The concentration of HCHs in Ha Long Bay, Hai Phong Bay, and
Ba Lat estuary were in the ranges of n.d.–0.85 ng gÀ1, 0.15–
1.00 ng gÀ1, and 0.03–0.26 ng gÀ1, respectively (Table 1 and
Fig. 2). Compared to DDTs and PCBs, their distribution showed a
little spatial variation due to their physico-chemical properties
like high vapor pressure and low particle affinity (Loganathan
and Kannan, 1994), which cause them easier to diffuse via atmosphere and water than DDTs and PCBs. The HCH level observed in
this northern part of Vietnam is slightly higher than those

reported from the Mekong River delta located in the southern
part (Minh et al., 2007). Among the HCH compounds, a-HCH is
the dominant isomer in both Ha Long Bay and Hai Phong Bay
with a mean composition of 49%, followed by b-HCH and c-HCH
(Fig. 4b). Because the a-isomer is the most volatile of the HCH
isomers in this subtropical region (ATSDR, 2005), the abundance
of a-HCH means that a technical HCH has been most recently
used in these regions. c-HCH was not detected in offshore stations but in estuarine and coastal stations. All stations in Ba Lat

Estuary are located within estuary, resulting in increase of composition of c-HCH in this region.
The major regional contribution of a-HCH and b-HCH changed
from the Northern Hemisphere mid-latitudes to the Northern
Hemisphere tropics after China banned the use of technical HCH


1200

S.H. Hong et al. / Chemosphere 72 (2008) 1193–1202

in 1983 (Li et al., 2000, 2003). According to recent investigations by
Li et al. (2000, 2003), Vietnam is classified along with India and
Malaysia as being the region having the highest annual emission
per area for both HCH isomers. However, levels of total HCHs in
the Vietnamese marine/estuarine sediment are relatively lower
than other Asian countries (Fig. 3). The highest HCH concentration
has been observed in India and followed by China, Hong Kong, Taiwan, and Japan > Korea > Vietnam. United States (US) and Mediterranean countries showed relatively low level of HCHs compared
with Asian countries. Previous international monitoring studies
using mussels and residential birds also reported similar distributions between the Asian countries (Kunisue et al., 2003; Monirith
et al., 2003). The relatively lower accumulation of HCHs in the Vietnamese environment might be related to rapid evaporation of HCH
isomers after use due to its high volatility in regions with high
temperatures.
PCBs: The concentration of PCBs in Ha Long Bay, Hai Phong Bay,
and Ba Lat estuary were in the ranges of 0.11–10.1 ng gÀ1, 0.45–
18.7 ng gÀ1, and 0.04–0.26 ng gÀ1, respectively (Table 1 and
Fig. 2). Hai Phong Bay is more contaminated with PCBs than Ha
Long Bay and Ba Lat estuary. Considering PCBs originate in industrial activities, relatively high levels of PCBs in Hai Phong Bay reflect its relatively high degree of industrialization among the
three study regions. Ha Long Bay showed an intermediate contamination level and Ba Lat estuary showed the lowest. Similar to DDT
compounds, the PCB level determined in sediment from Ba Lat
estuary is much lower than those reported from its upstream

Red River (Iwata et al., 1994; Nhan et al., 1998; Nhan et al.,
2001). Long residence times of contaminants in the water column
in natural trapping systems such as mangrove forests seem to be
the reason for lower levels of contaminants in the lower reaches
of the Red River. The highest concentration of PCBs was found at
station HP5 where shipbuilding industry is located, and followed
by stations HP14, and HP2. In Ha Long Bay, residential and particularly harbor regions showed relatively high PCB levels. The overall
PCB levels in sediments from the Vietnamese coastal environment
is much lower that those reported from industrialized temperate
regions such as USA (Daskalakis and O’Connor, 1995), Mediterranean sea (Wafo et al., 2006; Gómez-Gutiérrez et al., 2007), and
South Korea (Hong et al., 2006).
To see regional differences in PCB patterns, percent compositions of PCB congeners in sediment samples from three regions
are presented in Fig. 4c. Mid-chlorinated congeners (penta-,
hexa-, and hepta-PCBs) are significantly abundant in sediment
samples from Hai Phong Bay in comparison with those of Ha Long
Bay (Student t-test, p < 0.005) and Ba Lat estuary (Student t-test,
p < 0.001). On the other hand, low-chlorinated congeners (di-,
tri-, and tetra-PCBs) are relatively abundant in samples from Ha
Long Bay and Ba Lat estuary. The percent composition of low- and
mid-chlorinated PCBs in these three regions are as follows:
21 ± 12%:78 ± 12% for Hai Phong Bay, 38 ± 18%:58 ± 19% for Ha
Long Bay, and 47 ± 11%:40 ± 13% for Ba Lat estuary. In a previous
study, we observed an enhanced signal of higher chlorinated congeners close to shipyards and harbor regions (Hong et al., 2005),
where penta- to hepta-chlorinated congeners comprised 74% of total PCBs. Hai Phong has been long viewed as a center of the Vietnamese ship building industry, which accounts for about 50% of
the whole country’s capacity ( />Haiphong,+Shipbuilding+Center+of+Vietnam-205521.html). Along
the river of the bay, various scales of ship repair/construction facilities are located and shipping activities are very active throughout
the bay. These intensive industrial activities result in rather distinct PCB signatures in this bay compared to other regions. By contrast, the congener patterns in Ba Lat estuary are similar to those
observed in the regions having no typical local contamination
sources in a Korean nationwide monitoring study (Hong et al.,

2006), where di- to tetra-CBs and penta- to hepta-CBs comprised
47 ± 16% and 42 ± 16% of total PCBs, respectively.
Chlordanes, aldrin, endrin, dieldrin, and mirex compounds were
rarely detected in the samples and were only present at low concentrations (Table 1). However, the spatial distribution of chlordanes is similar to the DDT compounds, showing relatively high
levels along the coastline of Ha Long Bay. Among the chlordane
compounds, trans-nonachlor is relatively abundant, which might
be due to its relatively high persistence property (Strandberg
et al., 1998).
3.1. Relationship between organic pollutants, TOC, and sediment
particle size
In Table 1 and Fig. 2, data on total organic carbon (TOC) and particle size in surface sediments are presented. The TOC content in
sediments collected from Ha Long Bay, Hai Phong Bay, and Ba Lat
Estuary were in the ranges of 1.01–6.38%, 0.71–1.63%, and 0.34–
1.2%, respectively. Average TOC content was highest in Ha Long
Bay, where coastal stations (from HL11 to HL16) showed more elevated levels of TOC contents than offshore stations. Silt and clay
contents showed a little spatial fluctuation.
In Ha Long Bay, there was a significant correlation between TOC
and PCBs (r2 = 0.51, p < 0.001). When station HL15 was not considered, better correlations between TOC and PCBs (r2 = 0.92 p <
0.001) was found and there also appeared correlation between
TOC and DDTs (r2 = 0.47, p < 0.005). Station HL15 showed the elevated OCs concentration compared with its TOC content, implying
that there exists localized input source, and proximity to source is
governing factor in this station. Meanwhile, no significant relationship (p > 0.05) between OCs and sedimentary parameters (TOC and
particle size) in Hai Phong and Ba Lat Estuary were observed.
Region with spatially limited pollution sources and relatively
homogenous environmental conditions, Ha Long Bay, showed significant correlation between TOC and OCs. While, Hai Phong Bay
which has spatially scattered pollution sources and heterogeneous
dynamic environmental conditions did not show any governing
sedimentary parameters over distribution of OCs. The concept that
TOC and other sedimentary parameters are the main factor dominating the sorption of OCs to sediment has been intensively studied (Edgar et al., 2003; Hung et al., 2007 and references therein).
Good correlation between OCs and TOC can result from either

post-depositional sorption or co-emission (Hung et al., 2006). Relatively homogeneous environmental conditions like offshore
(Kyeonggi Bay, Lee et al., 2001), continental shelf (Yellow Sea,
Zhang et al., 2007) provides TOC dependent post-depositional
sorption environment. Spatially limited or defined sources could
give localized enrichment and gradient of TOC and OCs (Hung
et al., 2006, 2007). Some studies show a lack of correlation between
OCs and TOC or particle size, but state that it is the origin of the organic matter that is most important in determining the partitioning to sediment (Edgar et al., 2003; Secco et al., 2005).
3.2. Ecotoxicological concern
To roughly evaluate the ecotoxicological significance of OC contamination in Vietnamese coastal sediments, the data were compared with the Canadian environmental quality guideline for
marine sediment (CCME, 2002) in Fig. 5. This guideline specifies
the ‘‘interim sediment quality guideline” (ISQG) and the ‘‘probable
effect level” (PEL). The ISQG represents the chemical concentration
below which an adverse effect would rarely be observed, whereas
the PEL represents the concentration above which adverse effect
would frequently occur.
To compare the data with the guidelines, our sums of 18 PCB
congeners (IUPAC Nos. 8, 18, 28, 44, 52, 66, 101, 105, 118, 128,


1201

S.H. Hong et al. / Chemosphere 72 (2008) 1193–1202

Ha Long Bay
Hai Phong Bay
Ba Lat Estuary

Endrin
(2.67, 62.4)a

Dieldrin
(0.71, 4.3)a

Lindane
(0.32, 0.99)a

Chlordane
(2.26, 4.79)a

p,p'-DDE
(2.07, 374)a

p,p'-DDD
(1.22, 7.81)a

p,p'-DDT
(1.19, 4.77)a

2 x 18PCBs
(21.5, 189)a
0.001

0.01

0.1

1

10

100

1000

-1

Concentration (ng g dry wt.)
Fig. 5. Comparison of organochlorine concentrations in sediments from the coast of Vietnam with sediment quality guidelines (SQG). a(ISQG, PEL); interim sediment quality
guideline and probable effect level were suggested by Environment Canada (CCME, 2002).

138, 153, 170, 180, 187, 195, 206, and 209) were multiplied by a
factor of 2 (2 Â 18 PCBs), following the method adopted by Daskalakis and O’Connor (1995) and O’Connor (1996). PCB concentrations
in this study exceeded the ISQG value (21.5 ng gÀ1) at two sites, but
all are below the PEL value (189 ng gÀ1). All sites above the ISQG
value of PCBs are located in Hai Phong Bay (station HL5 and
HL14). This suggests that PCBs are of concern in Hai Phong Bay
and it is probably necessary to continue monitoring the possible
sources and levels of PCBs in this region. Concentrations of p,p0 DDT, p,p0 -DDD, and p,p0 -DDE exceeded the ISQG values at 10 sites,
17 sites and 4 sites, respectively, among which 2 sites for p,p0 -DDT
and 3 sites for p,p0 -DDD also exceeded the PEL values. Among the
chemicals investigated in this study, only DDT compounds exceeded their respective PEL values. This result indicates that DDT
is still the chemical of most concern in Vietnam, although concentrations are decreasing (Minh et al., 2007). The levels of lindane (cHCH) and dieldrin compounds are over their ISQG values at one
site but below the PEL values. For chlordane and endrin, all of
the sites showed lower levels than the ISQG values. Comparison
of the OC concentrations in Vietnamese coastal sediments with
the Australian and New Zealand Guideline (ANZECC and ARMCANZ, 2000) also showed similar results. Based on these results,
it is concluded that DDTs are the main compound of concern in
the Vietnamese environment and that the overall concentration
levels of organochlorines, except for DDTs, in sediments from the
northeast coast of Vietnam are relatively low from an ecotoxicological aspect for benthic organisms. However, they could cause problems for fish and wildlife through trophic transfer. Therefore,

further follow-up studies on POPs contamination in fish and wildlife from the bays are needed.
Acknowledgments
The authors wish to acknowledge Tran Lieu Thi, Ho Dung My, Le
Tuyen Huu for their assistance in collection and processing of samples, and Dr. Dhong Il Lim for providing the particle size analysis.
This work was supported by Grants-in-aid from International
Cooperative Research Project of Ministry of Science and Technology, Korea (Grant No. BSPN50300-1640-4) and Ecotechnopia-21
Program of Ministry of Environment, Korea (Grant No. 120010032).
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