Environ Sci Pollut Res DOI 10.1007/s11356-013-1709-7
PCB MIXTURES IN A COMPLEX WORLD
Distribution and ecological risk of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in surface sediments from the Bizerte lagoon, Tunisia Badreddine Barhoumi & Karyn LeMenach & Marie-Hélène Dévier & Yassine El megdiche & Bechir Hammami & Walid Ben Ameur & Sihem Ben Hassine & Jérôme Cachot & Hélène Budzinski & Mohamed Ridha Driss
Received: 4 January 2013 / Accepted: 1 April 2013 # Springer-Verlag Berlin Heidelberg 2013
Abstract Polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were determined in 18 surface sediment samples collected from Bizerte lagoon, Tunisia. The total concentrations of ten PCBs (∑PCBs) and of four OCPs (∑OCPs) in the sediments from this area ranged from 0.8 to 14.6 ng g−1 dw (average value, 3.9 ng g−1 dw) and from 1.1 to 14.0 ng g−1 dw (average value, 3.3 ng g−1 dw), respectively. Among the OCPs, the range of concentrations of dichlorodiphenyltrichloroethane and its metabolites (DDTs) and hexachlorobenzene (HCB) were 0.3– 11.5 ng g−1 dw (1.9 ng g−1 dw) and 0.6–2.5 ng g−1 dw (1.4 ng g−1 dw), respectively. Compositional analyses of the POPs indicated that PCB 153, 138 and 180 were the predominant congeners accounting for 60 % of the total PCBs. In addition, p,p′-DDT was found to be the dominant DDTs, demonstrating recent inputs in the environment. Compared with some other regions of the world, the Bizerte lagoon exhibited low levels of PCBs and moderate levels of HCB and DDTs. The high ratios ΣPCBs/ΣDDTs indicated predominant industrial versus agricultural activities in this area.
Responsible editor: Hongwen Sun B. Barhoumi : Y. El megdiche : B. Hammami : W. B. Ameur : S. B. Hassine : M. R. Driss (*) Laboratory of Environmental Analytical Chemistry (05/UR/12-03), University of Carthage, Faculty of Sciences of Bizerte, 7021 Zarzouna, Bizerte, Tunisia e-mail:
[email protected] B. Barhoumi : K. LeMenach : M.-H. Dévier : J. Cachot : H. Budzinski Laboratory of Physico- and Toxico-Chemistry of the Environment (LPTC), University Bordeaux 1, CNRS, EPOC (UMR 5805), 351 cours de la Libération, 33405 Talence Cedex, France
According to the established guidelines for sediment quality, the risk of adverse biological effects from such levels of OCPs and PCBs, as recorded at most of the study sites, was insignificant. However, the higher concentrations in stations S1 and S3 could cause biological damage. Keywords Organochlorine pesticides . Polychlorinated biphenyls . Sediments . Distribution . Ecotoxicological assessment . Bizerte lagoon . Tunisia
Introduction Organochlorines (OCs), such as polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs), represent an important group of persistent organic pollutants (POPs) that have caused worldwide concern as toxic environmental contaminants. In 2001, the Stockholm Convention (United Nations Environment Program UNEP 2001) on POPs was established as a global treaty to protect human health and the environment from these chemicals. Tunisia declared its accession to the Stockholm Convention in 2001 and became legally bound in 2004. Organochlorine compounds have been widespread used, with both industrial and agricultural sources contributing in significant amounts to inputs in the environment through leakage, disposal and evaporation. In aquatic environments, chlorinated compounds are removed from the water column and adsorbed onto particulate matter, and finally deposit to sediments, which may play a role as secondary contamination sources. These pollutants can be bioaccumulated in sediment-dwelling organisms and then transferred to higher trophic levels through the food chain (Chau 2005). POPs accumulated in sediments represent secondary sources of contamination and a potent threat for aquatic ecosystem.
Environ Sci Pollut Res
Although the applications of OCPs have been banned in many developed countries, some developing countries are still producing and using these persistent pesticides because of their low cost and versatility in controlling various insects (Monirith et al. 2003). OCPs chemicals were widely used in Tunisia from the end of 1940s to 1980s for insect control, sanitary purposes and agricultural and building protection. Based on their harmful effects to wildlife and humans, use and import of many chlorinated compounds such as aldrin, endrin, chlordane, DDT, HCB and toxaphene were completely banned in Tunisia in 1984. However, old stockpiles of obsolete pesticides were identified in Tunisia in 1997 (APEK 2005). The stocks were estimated in 2003 at 84,000 L and 1,472 tonnes of OCPs spread all over the country in some 132 sites. Similarly, PCBs have been used in industry as heat exchange fluids in transformers and capacitors and as additives in pesticides, adhesives, dusting agents, cutting oils, flame retardants, heat transfer fluids, hydraulic lubricants, sealants, paints, caulk and carbonless copy paper (Tolosa et al. 1997). In 1986, the import into Tunisia of transformers or any equipment containing PCBs was banned. Moreover, the use of PCB-containing transformer oils for maintenance and repair was also prohibited. However, a large number of transformers containing PCBs are still used or presently stored in unsatisfactory conditions and therefore may represent a threat and risk to human health and to the environment. This number continues to increase. In 2004, a preliminary study identified 1,079 PCBcontaminated transformers in Tunisia, representing 720 tonnes of liquid PCBs and 2,900 tonnes of contaminated equipment (APEK 2005). In spite of the fact that numerous countries withdrew the registered usage of OCPs many years ago, these manmade chemicals still persist at considerable levels worldwide (Hendy and Peake 1996; Sarkar et al. 1997). In many instances, derivatives of DDT, including DDE and DDD, have been detected in surface waters, in sediments and as suspended solids more than 25 years after DDT was prohibited (Hung and Thiemann 2002). The Bizerte lagoon is a Mediterranean lagoon located in the northern coast of Tunisia (latitude, 37°80′–37°14′N; longitude, 9°46′–9°56′E). It covers an area of 128 km2 and has a mean depth of 7 m. It communicates, in the North, with the Mediterranean Sea by a 7-km long canal and, in the South, with the Ichkeul Lake by the Tinja River. The principal tributaries of this lagoon are the Rivers Tinja, Mrezig, Garek, Ben Hassine and Gueniche (Fig. 1). The lagoon is subjected to the influence of several physical factors strongly fluctuating during the year. In winter, winds induce a vertical mixture of the water column, rains are strong and the freshwater flow coming from the Ichkeul Lake is important. On the other hand, in summer, inputs of seawater in the lagoon are important as well as surface water warming, which can lead to water column stratification (Sakka Hlaili
et al. 2003). The human population around the lagoon is estimated at 163,000 inhabitants (census of 2004) of which approximately 70 % are concentrated in Bizerte town. The other main important towns bordering the lagoon are Menzel Bourguiba (which has a naval port and a metal factory), Menzel Abderrahman and Menzel Jemil. Some other industries (an iron and steel plant, a cement factory and a refinery) are established nearby. Many recent reports are available describing the distribution of PAHs and heavy metals in surface sediments from the Bizerte lagoon (Trabelsi and Driss 2005; Louiz et al. 2008; Garali et al. 2010) and application of biochemical tools for pollution biomonitoring (Khessiba et al. 2001, 2005; Mahmoud et al. 2010; Ben Ameur et al. 2012). However, little information is available on contamination by OCs in this area. The only data available on OC contamination in the Bizerte lagoon are based on accumulation of these pollutants in marine species (Ben Ameur et al. 2013). To date, the distribution of PCBs in sediments from the Bizerte lagoon has been only reported by Derouiche et al. (2004), and these data represent the first report on the levels of contamination by OCPs. Based on this, a comprehensive study is needed to reflect the overall distribution and ecological risk of POPs in sediments from the Bizerte lagoon, and to identify the sources of POPs. Hence, 18 surface sediment samples were collected in this study area. The reported concentrations of OCPs in Bizerte lagoon sediments provide a baseline for future research in environmental pollution of lagoons and/or coastal areas in Tunisia.
Materials and methods Sampling A total of 18 surface sediments samples (0–10 cm) located by GPS (global positioning system) were collected with a stainless steel grab in March 2011. Details of the sampling sites are shown in Fig. 1 and Table 1. Sites were selected to be representative of the different human activities, e.g. industries, refinery activities, urban activities (wastewater) and agriculture. After collection, samples were wrapped in aluminium foil and cool transported to the laboratory where they were immediately stored in a freezer. All sediment samples were freeze-dried, then sieved using a 2-mm mesh, homogenized and stored at 4 °C prior to analysis. Chemicals and materials A standard mixture (Mix 1: Cat. No. 47927) of 12 PCB congeners (PCB 28, 31, 52, 44, 101, 149, 118, 153, 138, 180, 194 and 209) at 10-μg mL−1 heptane was purchased from Supelco (CIL, USA). OCP standards including p,p′-
Environ Sci Pollut Res Fig. 1 Sampling locations in the Bizerte lagoon
Table 1 Sampling site locations and physicochemical characteristics of the sediments from Bizerte lagoon
Station
Location
Depth (m)
TOC (%)
% CB209 > CB194 > CB44. The observed congener distribution towards more highly chlorinated compounds is consistent with previously published data in this lagoon and in other worldwide environments, indicating the preferential retention of these less volatile and more lipophilic compounds in the marine sediments (Nhan et al. 2001; Derouiche et al. 2004; Parolini et al. 2010). Differences in congener composition in the aquatic systems may also be attributed to a decline in the proportion of less chlorinated PCBs that are more susceptible to losses through volatilization, sedimentation and possibly microbial degradation (Quensen et al. 1988; MacDonald et al. 1992). Moderately and highly chlorinated PCBs may therefore be more persistent in the aquatic environment because they are less volatile and more soluble in lipids, adsorb more readily to sediments and are more resistant to microbial degradation (Connell 1988; Tyler and Millward 1996). The presence of tetrachloro- (CB52), pentachloro(CB101 and CB118), and hexachloro-congeners (CB138 and CB153) in sediments of the Bizerte lagoon is consistent with a contribution of commercial PCB mixtures, which have been widely used in transformers, electrical equipment and other industries in several countries (Barakat et al. 2002). The usage of PCBs in Tunisia is not well established, but the use of PCBs in transformers, electrical equipment and other industries is common. Very active industrial facilities are located in close vicinity to the Bizerte lagoon. Since the 1950s, about 100 industries settled at the vicinity of the lagoon, the most important being the cement factory (1950) and the steel complex “El Fouledh” (1965). Until 1985, one company in Tunisia (SACEM, in the Menzel Bourguiba
area) was manufacturing electrical transformers to meet national requirements. From 1970 to 1985, this company imported 900 tonnes of PCBs and manufactured about 908 transformers (APEK 2005). The comparison of OC concentrations observed in other regions of the world is difficult because of the geological characteristics of the sampling areas, the analytical method, the number of samples and number of compounds analyzed in the different studies that may not be the same. However, a general idea of pollutant levels of other coastal areas may be useful. In Table 5, the levels of organochlorine compounds in sediment samples recorded in this study are compared with those of other countries. As it can be seen in Table 5, the PCB concentrations in surface sediments of Bizerte lagoon in Tunisia are similar to those reported for Bengal Bay, India (Rajendran et al. 2005), Han River, Korea (Kim et al. 2009), Tonghui River, China (Zhang et al. 2004b), Cienfuegos Bay, Cuba (Tolosa et al. 2010), Bizerte lagoon, Tunisia (Derouiche et al. 2004) and Gulf of Lions, France (Tolosa et al. 1995). However, they are much lower than those measured in Alexandria Harbour, Egypt (Barakat et al. 2002), Offshore Barcelona, Spain (Tolosa et al. 1995), Firth of Clyde, Scotland (Kelly and Campbell 1995), Rhone Prodelta, France (Tolosa et al. 1995), Haihe River, China (Zhao et al. 2010) and Coast of Korea (Hong et al. 2006). Organochlorine pesticides (OCPs) The chlorinated organic compounds constitute the most important group of herbicides and are synthetically produced organic chemical compounds, with a circular structure in which the hydrogen molecules have been substituted by chlorine (Haynes and Johnson 2000). These pesticides are the ones found mostly in the environment because they were used extensively for at least two decades (1950–1970); their stable structure and their very poor solubility in water makes their accumulation in sediments easier. In the sediments of Bizerte lagoon, the major OCPs detected are DDTs and HCB. HCB, p,p′-DDE and p,p′-DDT showed the
Environ Sci Pollut Res
highest frequency of detection (100 %), followed by p,p′-DDD (28 %). DDTs Concentration of total DDTs (∑DDTs) ranged from 0.3 to 11.5 ng g−1 dw, with a mean of 1.9 ng g−1 dw (Table 3). Concentrations of p,p′-DDT in the sediments of Bizerte lagoon varied from 0.2 to 8.8 ng g−1 dw with the highest values observed at S1 (8.8 ng g−1 dw) and S3 (7.2 ng g−1 dw); p,p′-DDE and p,p′-DDD concentrations ranged from 0.1–0.9 ng g−1 dw to nd–1.9 ng g−1 dw, respectively, with maximum values observed at sites S1 and S3. ∑DDTs reached maximum value at station S1 (11.5 ng g−1 dw), which was similar to the results obtained for PCBs, followed by station S3 (10.6 ng g−1 dw). The minimum value of total DDTs was recorded at S5 and S13 (0.3 ng g−1 dw), whereas the other stations followed almost an equal trend of DDT distribution ranging from 0.4 to 1.5 ng g−1 dw. The high values of total DDT residue levels at site S1 might result from the discharge of untreated effluents from Bizerte City. Additionally, the high content of organic carbon in sediments at S1 may also favour DDT accumulation at this location. The station S3 is near the Haima River. The DDT residues likely issued from the agricultural areas located
upstream in the Haima River catchment and could be transported and deposited in the downstream sediment. The use of DDT was widespread in Tunisia during the 1940s and 1980s and was banned in the early 1984s (APEK 2005). The high concentrations of DDTs and related compounds in this lagoon indicate that DDT usage was heavy and that the lagoon had received significant amount of DDTs from river outflow and surface runoff. In Tunisia, the old stockpiles of DDT were estimated at 45 tonnes (APEK 2005) and were stored in unsatisfactory conditions, and this may explain the relatively elevated concentration of ∑DDTs reported in this study. The levels of DDTs in sediments in the present study compared with those in other parts of the world were shown in Table 5. As seen in Table 5, DDTs levels in sediments from the Bizerte lagoon were relatively high (0.3–11.5 ng g−1 dw) and similar to those in sediments from Bengal Bay, India (Rajendran et al. 2005), Han River, Korea (Kim et al. 2009), Tonghui River, China (Zhang et al. 2004b), Cienfuegos Bay, Cuba (Tolosa et al. 2010), Bizerte lagoon, Tunisia (Derouiche et al. 2004) and Gulf of Lions, France (Tolosa et al. 1995). Figure 3 shows p,p′-DDT and their metabolites as a percentage of total DDTs at the different sampling sites. As shown in Fig. 3, the average contributions of DDT congeners mixture detected in the sediment samples were
Table 5 Comparison of OCP and PCB concentrations (nanograms per gram dry weight) in surface sediments from various locations in the world Location
Year
∑PCBs
∑DDTs
HCB
References
Bizerte lagoon, Tunisia Bizerte lagoon, Tunisia Bengal Bay, India Han River, Korea Coast of Korea Tonghui River, China Haihe River, China Cienfuegos Bay, Cuba Rhone Prodelta, France Gulf of Lions, France
2011 2001 1998 2005 1997–2002 2002 2007 2005 1987–1991 1987–1991
0.8–14.6 (∑10PCBs) 0.89–6.63 (∑20PCBs) 0.02–6.57g 0.042–4.53h 0.170–371 (∑18PCBs) 0.78–8.74 (∑12PCBs) 0.177–253h 3.1–11.31 (∑11PCBs) 38.3–228.5 (∑12PCBs) 4.1–8.9 (∑12PCBs)
0.3–11.5b NA 0.04–4.79a 1.05–8.94a 0.010–135a 0.11–3.78b nd–155c 0.26–5.63b 62–675d 3.5–11.5d
0.6–2.5 NA NA 0.485–3.73 nd–2.59 NA nd–835
