PCBs in central vietnam coastal lagoons levels and trends in dynamic environments

Marine Pollution Bulletin 62 (2011) 1013–1024 Contents lists available at ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul PCBs in Central Vietnam coastal lagoons: Levels and trends in dynamic environments Silvia Giuliani a,⇑, Rossano Piazza b,c, Luca Giorgio Bellucci a, Nguyen Huu Cu d, Marco Vecchiato b,c, Stefania Romano a, Cristian Mugnai a, Dang Hoai Nhon d, Mauro Frignani a a CNR-Istituto di Scienze Marine, Via Gobetti 101, 40129 Bologna, Italy Dipartimento di Scienze Ambientali, Università di Venezia, Dorsoduro 2137, 30123 Venice, Italy CNR-Istituto per la Dinamica dei Processi Ambientali, Dorsoduro 2137, 30123 Venice, Italy d Institute of Marine Environment and Resources, 246 Da Nang Street, Haiphong City, Vietnam b c a r t i c l e i n f o Keywords: Polychlorinated biphenyls Sediments Historical trends Coastal lagoons Central Vietnam a b s t r a c t PCBs were analysed in surficial sediments and selected sediment cores collected between 2002 and 2008 in Central Vietnam coastal lagoons The aim was to determine contamination levels and trends, and to evaluate the effects of anthropogenic pressures and natural events Samples were mostly fine-grained with low total PCB concentrations (0.367–44.7 lg kgÀ1) Atmospheric transport and post depositional processes modify to some degree the fingerprint of PCB inputs to the environment favouring the predominance of 3, and chlorinated congeners The similarity of congener distributions in contemporary surficial samples also suggests the presence of a unique source over the entire study area, probably connected to mobilisation and long range transports from land-based stocks The removal of consistent sediment layers is hypothesised based on repeated samplings of the same area Natural meteorological events (such as typhoons) are suspected to be responsible for these sediment losses Ó 2011 Elsevier Ltd All rights reserved Introduction Polychlorinated biphenyls (PCBs) are compounds with a wide range of properties Commercially PCBs were marketed as mixtures with a degree of chlorination from 21% to 68% The most commonly used were those with a chlorine content between 42% and 54%, such as Aroclor 1242 and 1254 (Barbalace, 2003) Starting from their first commercialisation in 1929, these mixtures were used in many open (e.g., as lubricants, softeners for plastics and glues, laminating agents in paper production, impregnating agents, fire retardants, printing inks, oils, paints, self-copying paper, cement plaster and casting agents, insecticides, etc.) and closed systems (e.g., insulation liquid in capacitors, insulation and cooling liquid in transformers, hydraulic oils, heat exchangers), but their danger was soon acknowledged and the production was first regulated and then banned in the late 1970s (Erickson, 2001) Despite these efforts, PCBs have become ubiquitous pollutants, due to many factors: (1) the multiplicity of PCB sources and transport mechanisms; (2) the fact that their use is still allowed in enclosed transformers and capacitors, and (3) the presence of PCB in old ships as hydraulic liquids and covers of electric cables (Hutzinger et al., 1974; Atlas et al., 1986) In addition, landfills are now considered a major source, ⇑ Corresponding author Address: Consiglio Nazionale delle Ricerche Istituto di Scienze Marine, Sede di Bologna, Via Gobetti 101, 40129 Bologna, Italy Tel.: +39 051 6398864; fax: +39 051 6398940 E-mail address: silvia.giuliani@bo.ismar.cnr.it (S Giuliani) 0025-326X/$ - see front matter Ó 2011 Elsevier Ltd All rights reserved doi:10.1016/j.marpolbul.2011.02.035 due to their release from rubbish and wastes (Breivik et al., 2002) As a consequence, PCBs still constitute a worldwide environmental problem, and the knowledge of their concentrations in the environment is needed to understand present contamination levels and trends, to assess the risk, and to plan management strategies In this context, the assessment of sediment contamination is considered a fundamental indicator of the overall health of the systems (e.g Nhan et al., 2001; Colombo et al., 2005; Kuzyk et al., 2005; Sundberg et al., 2005; Denton et al., 2006) The information about PCB sources and levels in Vietnam is limited However, it is likely that environmental levels have been exacerbated by the long periods of conflict and subsequent rapid industrialization/economic development Frignani et al (2007) described the PCB distribution in cores and surficial samples from Tam Giang-Cau Hai (TG-CH) system, but nothing was known about the contamination of the other coastal lagoons in Central Vietnam We aimed to fill this gap by assessing present PCB levels through the analysis of surficial samples Additionally, trends and controlling factors were examined at five selected sites (four lagoons) through the study of sediment cores and the repeated sampling of the same locations in different years Study sites The studied lagoons are all located in the central part of the country, between 11°N and 16°N (Fig 1), and belong to the coastal 1014 S Giuliani et al / Marine Pollution Bulletin 62 (2011) 1013–1024 provinces of Thua Thien Hué, Quang Nam, Quang Ngai, Binh Dinh, Phu Yen, Khanh Hoa and Ninh Thuan They are diverse in scale, shape, size, stability of inlets, water features and geological and geomorphological distribution (Cu, 1995), and can be rated into four categories: very small (less than 10 km2, as Nuoc Man, NM, and Dam Nai, DN), small (10–20 km2 as Lang Co, LC, Nuoc Ngot, NN, and O Loan, OL), medium (20–50 km2 as Truong Giang, TG, and Thuy Trieu, here referred to as Cam Ranh, CR), and large (more than 50 km2 as TG-CH, and Thi Nai, TN) These valuable and diverse ecosystems, important as tourist attractions and useful for fishing and aquaculture activities, are key sites for the development of the Vietnamese economy However, ongoing problems with anthropogenic pollution, such as high concentrations of oil, nitrate and coliforms in water (Dieu, 2006; Thom, 2006) are believed to be deeply affecting the environmental quality of these sites over time Although the concentrations of persistent organic pollutants such as PCBs and PAHs (Frignani et al., 2007; Giuliani et al., 2008) are believed to be low, these are also expected to increase over time as economic development continues Materials and methods Sampling locations in Central Vietnam coastal lagoons are shown in Fig Sediment cores were sampled multiple times from 2002 to 2008, using a manual piston corer (6 cm i.d.) that preserved undisturbed sediment–water interfaces Collection dates and core lengths of the 2004–2008 samplings are reported in Table 1, in addition to sampling details of the TG-CH cores collected in 2002 and already described by Frignani et al (2007) After collection, the cores were extruded and sectioned at intervals of 1–4 cm, with higher resolution at the top Sediment slabs, cleaned at the edges to avoid the effects of smearing, were then put in polyethylene vessels and stored in a refrigerator at °C until arrival at the lab Afterwards, they were conserved at À18 °C until analysis Grain size analyses were carried out by wet sieving, to separate sands, after a pre-treatment with H2O2 Silt and clay fractions were determined with a X-ray Micrometric SediGraph Organic carbon (OC) content was obtained through a CHN analyser after elimination of carbonates by treatment with HCl in a silver capsule 210 Pb activities were determined through acid extraction and alpha counting of the daughter 210Po spontaneously deposited onto silver disks 209Po was used as an internal standard to account for methodological and counting efficiencies 137Cs determinations were obtained by gamma counting of dry samples in standard vessels of suitable geometries Radiotracer analyses were described in detail by Bellucci et al (2007) Fig Sample locations in Central Vietnam coastal lagoons Table Collection dates and results of the analysed parameters (core length, porosity,% content of fines, i.e silt plus clay, 210Pb activity, total and fine-normalised PCB concentrations,% contribution of each PCB congener class, from to 10 Cl substitutes) for all surficial samples of the cores collected from 2002 and 2008 Collection date Core length (cm) Porosity Fines (%)a 210 Pb activity (Bq kgÀ1) PCBs (lg kgÀ1) Norm PCBs (lg kgÀ1) CB-1 (%) CB-2 (%) CB-3 (%) CB-4 (%) CB-5 (%) CB-6 (%) CB-7 (%) CB-8 (%) CB-9 (%) CB-10 (%) TG-CH 02 08/12/02 23/06/04 27/06/07 11/12/02 22/06/04 27/06/07 22/06/04 27/01/08 07/06/05 08/06/05 26/01/08 08/06/05 25/01/08 09/06/05 25/01/08 10/06/05 23/01/08 11/06/05 21/01/08 11/06/05 21/01/08 74 81 51 50 37 51 87 79 73 69 59 57 59 29 99 77 71 73 95 49 75 0.74 0.63 0.66 0.70 0.61 0.73 0.74 0.77 0.70 0.69 0.59 0.70 0.57 0.62 0.59 0.78 0.74 0.94 0.73 0.60 0.45 93 91 82 88 80 95 92 92 40 85 77 76 51 1.0b 40 96 96 81 54 1.0b 18 174 152 95 240 196 106 445 196 85 78 64 84 44 109 70 94 74 60 37 36 28 22.9 5.04 6.39 24.5 5.29 1.40 4.39 4.35 2.55 1.99 5.80 2.12 5.04 44.7 3.36 2.34 4.15 2.32 5.38 1.32 4.50 24.6 5.53 7.83 27.8 6.64 1.48 4.77 4.73 6.30 2.33 7.52 2.79 9.94 4470b 8.42 2.44 4.34c 2.86 9.91c 132b 25.4c 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 17 n.d n.d 14 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 47 28 21 55 28 30 25 36 26 19 25 24 31 2.7 38 23 40 19 37 37 31 37 30 32 35 34 16 26 48 14 27 50 11 54 4.7 45 40 46 40 47 23 50 12 17 36 8.0 16 23 41 13 40 33 12 30 11 25 12 32 12 34 12 37 15 3.5 5.1 9.2 2.2 4.6 26 5.4 2.6 9.6 11 4.8 22 3.0 46 3.2 5.2 2.0 6.7 2.8 3.2 3.4 0.64 1.7 1.5 0.39 1.0 5.2 3.3 1.0 6.7 7.8 2.7 8.8 1.2 20 1.4 n.d n.d n.d 1.5 n.d n.d n.d n.d n.d n.d 1.3 n.d n.d n.d 3.8 2.1 5.0 4.2 n.d 2.0 n.d n.d n.d n.d n.d n.d n.d n.d 0.89 n.d n.d 0.70 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 0.58 n.d n.d 0.51 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 TG-CH 10 LC TG NM NN TN OL CR DN S Giuliani et al / Marine Pollution Bulletin 62 (2011) 1013–1024 Lagoon n.d = Not detected a Grain sizes are calculated considering only the fraction