DSpace at VNU: Persistent organochlorine residues in estuarine and marine sediments from Ha Long Bay, Hai Phong Bay, and...
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: http://www.deh.gov.au/water/quality/nwqms/volume1.html], indicating that adverse effects may occur to marine species in that areas Ó 2008 Elsevier Ltd All rights reserved 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: shhong@kordi.re.kr (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 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 km2 Recently, industrial activities like coal mining, ship-building and ship-repairing have caused geological and environmental changes Table 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 13 13 16 25 50 21 63 17 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 27 27 42 12 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 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 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 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  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 20º 55'' Hanoi 12 13 Hon Gay 14 15 16 10 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 Hai Phong 11 20º 48'' 20º 18'N 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 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 min, 100 °C to 140 °C at °C minÀ1, 140 °C for min, 140 °C to 250 °C at 1.5 °C minÀ1, 250 °C for min, 250 °C to 300 °C at 10 °C minÀ1, and 300 °C for 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) 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 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 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 (http://www.epa.gov/emap/nca/html/ 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 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 15 400 200 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 20 10 HL1 HL2 HL3 HL4 HL5 HL6 HL7 HL8 HL9 HL10 HL11 HL12 HL13 HL14 HL15 HL16 HP HP HP HP HP HP HP HP HP HP10 HP11 HP12 HP13 HP14 HP15 BL1 BL2 BL3 BL4 BL5 BL6 BL7 BL8 BL9 BL10 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 HL1 HL2 HL3 HL4 HL5 HL6 HL7 HL8 HL9 HL10 HL11 HL12 HL13 HL14 HL15 HL16 HP HP HP HP HP HP HP HP HP 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 120 100 TOC (%) 80 60 40 20 0 HL1 HL2 HL3 HL4 HL5 HL6 HL7 HL8 HL9 HL10 HL11 HL12 HL13 HL14 HL15 HL16 HP HP HP HP HP HP HP HP HP HP10 HP11 HP12 HP13 HP14 HP15 BL1 BL2 BL3 BL4 BL5 BL6 BL7 BL8 BL9 BL10 Slit & Clay (%) Site Site Fig 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 (http://www.gefweb.org/Whats_New/documents/Antifouling_Paint_Final.pdf) 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 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 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 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 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) (http://www.epa.gov/emap/nca/html/data/index.html), 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) 1199 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 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 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 20 40 60 80 100 Percent composition (%) Fig 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 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 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 (http://www.marinelink.com/Story/ 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 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 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 x 18PCBs (21.5, 189)a 0.001 0.01 0.1 10 100 1000 -1 Concentration (ng g dry wt.) Fig 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  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 sites, respectively, among which sites for p,p0 -DDT and sites for p,p0 -DDD also 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Deca Ba Lat Estuary Hai Phong Bay Ha Long Bay 20 40 60 80 100 Percent composition (%) Fig Relative composition of (a) DDTs, (b) HCHs, and (c) PCBs in sediment from Ha Long Bay, Hai Phong Bay, and. .. 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... 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