Occurrence and distribution of linear alkylbenzene sulfonates and sulfophenylcarboxylic acids in several Iberian littoral ecosystems

The distribution of linear alkylbenzene sulfonates (LAS) and sulfophenylcarboxylic acids (SPC) has been characterized in water and sediment of five Iberian estuaries and a saltmarsh channel. The highest concentrations of LAS and SPC were detected in shallow zones close to discharge points of untreated urban effluent, and decreased sharply with increasing distance from these. SPC homologues of between 3 and 12 carbon atoms were detected, although their concentrations were several orders of magnitude lower than the corresponding LAS. The highest SPC concentrations found were of medium carboxylic chain lengths (C6-C8) in water, and of longer chain lengths (C9-C11) in particulate material. LAS homologues were associated preferentially with the particulate material. The vertical distribution of LAS in the water column was not homogeneous, in contrast to that presented by the SPC homologues. In the case of the Sancti Petri Channel, there was a net flow of LAS exportation into the Bay of Cádiz, of -38.6 kg day(-1), and a net flow for SPC of -6.0 kg day(-1). The daily mass input of LAS and their biodegradation intermediates from the Sancti Petri Channel to Cadiz Bay was 44.6 kg.     

Occurrence and weight-of-evidence risk assessment of alkyl sulfates, alkyl ethoxysulfates, and linear alkylbenzene sulfonates (LAS) in river water and sediments

Alkyl sulfates (AS), alkyl ethoxysulfates (AES) and linear alkyl benzene sulfonates (LAS) are all High Production Volume (HPV) and 'down-the-drain' chemicals used globally in detergent and personal care products, resulting in low levels ultimately released to the environment via wastewater effluent. Due to their surfactant properties, they preferentially sorb to sediments. Hence, assessment of their levels and potential perturbations on benthos are of interest. The relative levels of AS/AES decreased with distance from the wastewater treatment plant outfall. However, this was not evident for LAS. Short chained AES and especially AS dominated the homologue distribution for AES. There were no evident patterns in LAS homologue distribution. The overall mean margin of exposure (MoE) for AS/AES and LAS is approximately 40 (range: 3 to 100) suggesting no noteworthy perturbation on biota. The findings in this study are in concordance with previous preliminary hazard screening. Comparative sediment contamination analyses principally based on Chapman and Anderson [Chapman PM, Anderson, J. A decision-making framework for sediment contamination. Integr Environ Assess Mana. 2005; 1: 163-173.] and the U.S. Environmental Protection Agency RAPID assessment methods [USEPA. Rapid bioassessment protocols for use in wadeable streams and rivers: Periphyton, benthic, macroinvertebrates, and fish. 1999. Second Edition. U.S. Environmental Protection Agency Office of Water, Washington, D.C. EPA 841-B-99-002.] did not reveal significant correlations between the surfactant concentrations and ecological status of the sampling locations. Several Lines of Evidence (LoE) of the Weight-of-Evidence (WoE) lead to the conclusion of low aquatic risk associated to the monitored compounds.     

Organotin speciation in Bizerte lagoon (Tunisia)

For the first time, organotins have been assessed in samples collected from Bizerte lagoon, in Tunisia, during two seasons (summer and winter). The organotin distribution was studied in marine sediments and mussels tissues of this lagoon. Butyl-, phenyl- and octyltins were determined using a rapid speciation analytical method based on one-step ethylation/extraction with sodium tetraethylborate in aqueous phase. Simultaneously to the ethylation, the extraction was performed by either liquid/liquid extraction (LLE) or head-space solid phase microextraction (HS-SPME). Gas chromatography with pulsed flame photometric detection (GC-PFPD) was used to perform quantitative determination. The technique has been validated using biological and sediment reference materials. The different samples from Bizerte lagoon were found to be moderately contaminated, especially by butyltins. This pollution was attributed to industrial activities, which are very important in this area. Organotins appeared accumulated in both sediments and mussels, while significant degradations of triorganotins to monosubstituted ones was observed in water.     

Effect of linear alkylbenzene sulphonates (LAS) on the anaerobic digestion of sewage sludge

Batch anaerobic biodegradation tests with different alkylbenzene sulphonates (LAS) at increasing concentrations were performed in order to investigate the effect of LAS homologues on the anaerobic digestion process of sewage sludge. Addition of LAS homologues to the anaerobic digesters increased the biogas production at surfactant concentrations 5-10 g/kg dry sludge and gave rise to a partial or total inhibition of the methanogenic activity at higher surfactant loads. Therefore, at the usual LAS concentration range in sewage sludge, no adverse effects on the anaerobic digesters functioning of a wastewater treatment plant (WWTP) can be expected. The increase of biogas production at low surfactant concentrations was attributed to an increase of the bioavailability and subsequent biodegradation of organic pollutants associated with the sludge, promoted by the surfactant adsorption at the solid/liquid interface. When the available surfactant fraction in the aqueous phase instead of the nominal surfactant concentration was used to evaluate the toxicity of LAS homologues, a highly significant relationship between toxicity and alkyl chain length was obtained. Taking into account the homologue distribution of commercial LAS in the liquid phase of the anaerobic digesters of a WWTP, an EC(50) value of 14 mg/L can be considered for LAS toxicity on the anaerobic microorganisms.     

An improved microdesulphonation/gas liquid chromatography procedure for the determination of linear alkylbenzene sulphonates in U.K. rivers

An improved microdesulphonation/gas liquid chromatography (GLC) procedure is described for the specific determination of μg l⁻¹ levels of linear alkylbenzene sulphonates (LAS) in aqueous environmental samples including sewage, sewage effluent and surface waters. The LAS is concentrated from samples as its methylene blue complex by a large-scale solvent extraction and is then freed from potential interferences by a series of clean-up steps, i.e. ion-exchange chromatography, hydrolysis and solvent extraction, prior to its desulphonation with a concentrated phosphoric acid reagent. The resulting alkylbenzene hydrocarbons are recovered and quantitatively determined by a capillary GLC technique with the aid of internal standards (primary and secondary alkylbenzene sulphonate isomers) added at the initial concentration stage.The introduction of the clean-up stages, particularly a selective extraction of the LAS as the l-methylheptyl amine salt into hexane, has resulted in GLC traces that are free from major interferences and in which it is possible to readily identify LAS isomers on the basis of the relative retention times. The procedure has a limit of detection of less than 10 μg l⁻¹ LAS in a sample and allows the quantification of sub-μg l⁻¹ levels of individual isomers (C₉–C₁₅ homologues). The mean recovery of a C₁₂ LAS internal standard through the complete procedure is 91% for the environmental samples analysed.This procedure, together with a non-specific methylene blue colorimetric method (for determining anion surface active material), has been used in a monitoring exercise to establish the levels of LAS and methylene blue active substances (MBAS) in U.K. rivers and the River Rhine. A mean MBAS level of 0.15 mg l⁻¹ was found at the U.K. river sites selected (35 samples), of which only 26% on average was attributable to LAS by microdesulphonation/GLC analysis. However, the levels of LAS and its contribution to the total MBAS in rivers was found to vary with the nature of the sampling location, i.e. depending whether it was above, below or in the vicinity of a sewage effluent discharge. The distribution of the LAS isomers at these sites also showed differences that could be explained in terms of their relative biodegradabilities.     

Mercury in sediments and Nassarius reticulatus (Gastropoda Prosobranchia) in the southern Venice Lagoon

The southern basin of the Venice Lagoon has been the focus of fewer studies concerning contamination from heavy metals than the northern and central basins. A recent increase in urban waste waters from Chioggia town, as well as dockyards, shipping and fishing activities, affect this part of the lagoon. The aim of this study was to investigate the total mercury (THg) incidence in sediments and Nassarius reticulatus gastropods in order to assess its distribution and evaluate the level of contamination. THg concentration measured in bottom sediments ranged between 0.1 and 3.4 mg/kg d. wt. The enrichment factor (EF) showed high values (avg. 30, max 49) near the dockyards of Chioggia; the lowest (avg. 9, max 17) were found in the coastal marine sediments near the port entrance of the southern basin. THg in marine scavenger gastropods accumulated in N. reticulatus with concentrations falling within the range of 0.3-1.3 mg/kg d. wt. A positive correlation was found between THg concentration in sediments and in N. reticulatus in all sites, excluding the dockyards. A first local cause for mercury pollution might be attributed to the antifouling paints used in great quantity in the recent past near the town of Chioggia. Moreover, fine suspended sediments associated with tidal flushing are suggested as possibly being the vehicle for pollutant dispersal from the Marghera industrial area to the whole of Venice's lagoon.     

Determination of trace levels of linear alkylbenzenesulfonates in the marine environment by high-performance liquid chromatography

The widespread and increasing use of linear alkylbenzenesulfonates (LAS) has shown the need for analytical procedure of LAS. A method has been developed to isolate, concentrate and determine trace levels of LAS from marine environmental samples. LAS were extracted with Bond Elut C₁₈ reversed-phase minicolumn and quantified by high-performance liquid chromatography with fluorophotometric detection. This method can determine trace levels of LAS, simply, rapidly, specifically and sensitively and minimize the risk of contamination. This method showed the limit of determination for each LAS component of approx. 0.1 μg l⁻¹ for water, 0.03 μg g⁻¹ (dry basis) for bottom sediment or 0.3 μg g⁻¹ (wet basis) for fish sample, the recovery of 80% for water, 87% for sediment or 86% for fish sample, and the reproduceability of 3–4% relative standard deviation for five-replicated analysis of sea water or sea sediment.This proposed method was employed for the determination of LAS in marine environmental samples of Tokyo bay, Japan. A concentration range between 0.8 and 30 μg l⁻¹ of LAS was found in Tokyo bay water. The highest concentration was detected in the coastal areas.     

HPLC detection of linear alkylbenzenesulfonates surfactants (LAS) in marine sediments of the urban sewage area of Cortiou (Marseille,France)

An improved selective method for determining linear alkylbenzenesulfonates surfactants (LASs) in marine sediments using solid‐phase extraction and RP‐HPLC with UV detection is described. The complete analytical method is used on surface sediments from the creek of Cortiou, France. This site is affected by the sewage from the urban area of Marseille. The total LAS concentrations in the sediment range from 12.19?µg/g near the existing outlet to 0.47?µg/g beyond Maire Island. The flux of pollution provided by the outfall is preferentially oriented from east to west by the Liguro‐Provençal current. The significant values are mainly confined on a perimeter of 2.5?km around the outfall. The particule size observations concerning the sediments show that oxygenated sandy zones, where eliminating mechanisms (desorption, biodegradation) particularly occur, are mainly located on the Chèvres plateau and around Jarre, Plane and Riou Islands.     

Influence of the hydrophilic moiety of anionic and nonionic surfactants on their aerobic biodegradation in seawater

The extent and kinetics of the primary biodegradation have been characterized for the most commonly-used surfactants, employing four homologues with the same alkyl chain: dodecyl ethoxy sulfate (C₁₂AES), sodium dodecyl sulfate (SDS), dodecyl alcohol ethoxylate (C₁₂AEO) and dodecyl benzenesulfonate (C₁₂LAS). A brief acclimatization period has been required to enable an effective degradation of C₁₂LAS and C₁₂AES to take place, but this lag phase has not been detected for SDS and C₁₂AEO. Primary biodegradation percentages at the end of these experiments were higher than 99%, showing a fast degradation rate in all cases (average half-life lower than 2 days). The secondary biodegradation of C₁₂LAS was also monitored. C₁₂LAS external isomers, which are predominant, are preferentially degraded by successive β-oxidations, generating significant amounts of external even isomers of sulfophenylcarboxylic acid (SPC) (mainly 2,3ΦC_4,6SPCs). In ontrast, internal isomers are converted into internal odd isomers of SPC (mostly 4,5ΦC_5,7SPCs) by ω-oxidation followed by α-oxidation and/or β-oxidations.     

Reduction of aquatic toxicity of linear alkylbenzene sulfonate (LAS) by biodegradation

Partial biodegradation of LAS is shown to significantly reduce the specific toxicity (i.e. per unit weight) of the remaining LAS to Daphnia magna (water fleas) and Pimephales promelas (fathead minnows). This results from the fact that the longer homologs and more terminal isomers, which are the more toxic, are also the more rapidly degraded under bacterial action. The acute aquatic LC₅₀ of LAS may range from 0.5 to 50 mg/l depending mainly upon the chain length of the particular homolog. A high molecular weight commercial type LAS with LC₅₀ around 2 mg/l before biodegradation may show Daphnia LC₅₀'s of 30–40 mg/l. for the LAS remaining after 80–85% degradation.A further contribution to this toxicity reduction may occur if the methylene blue analytical method is used to determine the amount of LAS remaining, since some of the biodegradation intermediates show methylene blue activity but no significant toxicity. For example, sulfophenylundecanoate, a model of early intermediates, shows Daphnia and fathead lc₅₀'s 200 and 75 mg/l., respectively. Sulfophenylbutyrate, modeling somewhat later intermediates, gives lc₅₀ values around 5000–10,000 mg/l. Dialkyl tetralin/indane sulfonates (the major non-linear components in commercial LAS) exhibit 1/2–1/10 the toxicity of the corresponding LAS homologs.These results re-emphasize that analysis simply for methylene blue active substances (MBAS) gives no basis for predicting the aquatic toxicity of an environmental sample. And furthermore, that meaningful water quality criteria and standards cannot be established in terms of MBAS content while based on toxicity studies on intact, undegraded LAS.     

Distribution of heavy metals in sediments of the Venice Lagoon: the role of the industrial area

We sampled eighteen stations in the lagoon and nine in the canals of the industrial area of Porto Marghera. At each lagoon site a short core, 10 cm long, was taken and immediately extruded to obtain four slices 2.5 cm thick. Surficial sediment samples from the canals were 2-8 cm thick. Samples were analysed for As, Cd, Hg, Pb and Zn after acid extraction. Maximum values are seen in sediments taken from the oldest part of the industrial area (up to 132, 70, 48, 929, 8295 microg g(-1) for As, Cd, Hg, Pb and Zn, respectively), whereas the highest concentrations in the lagoon are much lower (25, 5.0, 2.3, 114, 1115 microg g(-1) for As, Cd, Hg, Pb and Zn, respectively). Metal distributions are not driven by sediment characteristics, such as grain size composition and organic carbon content: the strong gradients reflect the relative importance of the sources. In fact, a series of factories have been treating minerals for many years for the production of metals and chemicals. Concentration-depth profiles in lagoon sediments suggest that the contamination is decreasing, thus confirming the trends shown by previous core data. Since the release of metals from the industrial plants has been reduced, the polluted sediments stored in the industrial canals are presently the most likely source of toxic metals to the lagoon environment. The influence of this source can be seen in the still high levels found in the lagoon sample closest to the industrial area.     

Occurrence and fate of linear and branched alkylbenzenesulfonates and their metabolites in surface waters in the Philippines

Laguna de Bay in the Philippines is one of the largest freshwater lakes in Asia and is considered a primary source of drinking water, but also receives daily discharges of effluent from both domestic and industrial activities. Branched alkylbenzenesulfonates (ABS), which were banned in Europe and withdrawn from the market in the U.S. since the mid-1960s, but not in Southeast Asia, and linear alkylbenzenesulfonates (LAS) are anionic surfactants used in detergent formulations and are therefore main components of effluent discharges. The presence of both LAS and ABS in several water streams in the catchment area of Laguna de Bay was determined using liquid chromatography-mass spectrometry (LC-MS). The concentration levels of LAS (1.2-73 and 2.2-102 microg l(-1)) and ABS (1.1-75 and 1-66 microg l(-1)) in some tributaries of Laguna de Bay and its outlet (Pasig River) to Manila Bay were assessed in December 1999 and March 2000, respectively. The LAS/ABS ratio was calculated as an indication of the extent of the distribution and fate of these surfactants in the surface water. The nearer the location to the metropolitan area of Manila, the higher the levels of LAS and ABS detected in the waters. Moreover, the extent of biodegradation was investigated by monitoring their alkyl homologue distribution and the presence of sulfophenylcarboxylate (SPC) metabolites. Similarly, differences in the levels of SPC and the homologues were apparent at the different sampling points. Presumably, even the quite recalcitrant ABS form SPCs under the conditions present in Southeast Asia. Since wastewater treatment facilities are not well established in developing countries like the Philippines, the call for the use of environmentally friendly chemicals is of even higher significance.     

Effects of zinc on molting and body weight of the estuarine crab Neohelice granulata (Brachyura: Varunidae)

The semiterrestrial burrowing crab Neohelice granulata is one of the main inhabitants of the supratidal and intertidal zones of brackish salt marshes, estuaries and coastal lagoons from South America's Atlantic littoral. A large population of this species spreads out Mar Chiquita coastal lagoon (in Argentina) and its corresponding wetlands, and is considered as a key species within this system.Since high values of dissolved heavy metals (including Zn) have been recently reported within Mar Chiquita coastal lagoon, with levels unusually higher than those from other coastal systems within Argentina, it has been explored that the existence of a risk of environmental conditions endanger these populations. So, juveniles of this estuarine crab were experimentally exposed to increasing concentrations of dissolved Zn (i.e., 0, 0.5 and 1 mg Zn²⁺ L^− 1) during six months, the time involved between two successive molts; in addition, both the size and weight reached after each molt were also studied in this assay. It can be concluded that zinc can be toxic to crabs only at high concentrations. Considering that levels up to 1 mg Zn L^− 1 were recently reported in Mar Chiquita coastal lagoon waters, the potential occurrence of mean chronic effects on the crab population within the coastal lagoon is discussed.     

HPLC determination of polycyclic aromatic hydrocarbons (PAHs) in the littoral urban sewage area of cortiou (Marseille,France)

A selective method for determining polycyclic aromatic hydrocarbons (PAHs) in sediments using solid‐phase extraction and RP‐HPLC with fluorescence and UV detection is described. The complete analytical method is used to surface sediments from the creek of Cortiou (France). Sewage from the urban area of Marseille is delivered to the creek. PAH levels in sediments (µg/g) range between 2.251 µg/g (for the benzo(a)anthracene) and 相似文献   

Distribution of selected anthropogenic radionuclides (137Cs, 238Pu, (239,240)Pu and 241Am) in marine sediments with emphasis on the Spitsbergen-Bear Island area

Measurements of anthropogenic radionuclides in marine sediments can provide good estimates of past and present radioactive contamination of the marine environment. The Barents Sea is one of the world's richest ocean areas, and it is therefore of major interest for Norwegian fisheries to document the levels of radioactive contamination of this and adjacent ocean areas. In this study, concentrations of 137Cs, 238Pu, (239,240)Pu and 241Am were measured in marine sediments collected mainly in the Spitsbergen-Bear Island region. Additional samples collected in the deep Norwegian Sea and near the Greenland ice-edge have been included for comparison. The highest radionuclide levels were found near Spitsbergen, reaching over 50% higher than in adjacent areas. Determinations of the mineral content and particle size distribution indicate a relation between the content of clay minerals and radionuclide levels. The present study confirms earlier observations of elevated levels of 137Cs in sediments in the Spitsbergen-Bear Island area and documents elevated levels of 238Pu, (239,240)Pu and 241Am in these sediments. Using an exponential curve fit based on determinations of unsupported 210Pb in sediment cores, sedimentation rates of 0.28, 0.05 and 0.26 cm year(-1) were calculated at locations south of Spitsbergen, near the Greenland ice-edge and in the deep Norwegian Sea, respectively.     

Dynamic modelling of nitrification in an aerated facultative lagoon

Faced with the need to improve ammonia removal from lagoon wastewater treatment plants (WWTPs) operated in Quebec, Canada, mechanistic modelling has been proposed as a tool for explaining the seasonal nitrification phenomenon and to evaluate optimization and upgrade scenarios. A lagoon model that includes a modified activated sludge biokinetic model and that assumes completely mixed conditions in the water column and sediments has been applied to simulate 3 years of consecutive effluent data for a lagoon from the Drummondville WWTP. Successful prediction of results from this plant indicates that the seasonal nitrification is determined by temperature, dissolved oxygen (DO) concentrations, hydraulic retention time (HRT) of the water column and washout driven by a well-mixed water column. Results also indicate that sediments contribute to the ammonia load in the lagoon effluent, particularly in spring and early summer. Sensitivity analyses performed with the model indicate that the nitrification period could be prolonged by increasing DO concentrations in the lagoon and that bioaugmentation would be particularly effective in spring and early summer. Limitations of the model are discussed, as well as ways to improve the hydraulic model.     

Fate and effects of linear alkylbenzene sulphonates (LAS) in the terrestrial environment

Linear alkylbenzene sulphonates (LAS) are a group of anionic surfactants, characterised by having both a hydrophobic and a hydrophilic group. LAS is one of the major ingredients of synthetic detergents and surfactants and is used world-wide for both domestic and industrial applications. LAS is relatively rapidly aerobically degraded, but only very slowly or not at all degraded under anaerobic conditions. Therefore, LAS can be found in very high concentrations in most sewage sludge and enter the soil compartment as a result of sludge application. LAS can be found in elevated concentrations in soil immediately after sludge amendment, but a half-life of approximately 1-3 weeks will generally prevent accumulation in soil and biota. The concentration in soils that have not received sewage sludge recently, is generally less than 1 mg kg-1 and not more than 5 mg LAS kg-1. This is below the lowest concentration of LAS where effects have been observed in the laboratory. The laboratory data is in accordance with field studies using aqueous solutions of the sodium salt of LAS. However, observations of the ecological impact of sewage sludge applications or application of LAS spiked into sludge indicates a lower toxicity of LAS when applied in sludge. On the basis of the information reviewed in this paper, it is concluded that LAS can be found in high concentrations in sewage sludge, but that the relatively rapid aerobic degradation and the reduced bioavailability when applied via sludge, most likely will prevent LAS from posing a threat to terrestrial ecosystems on a long term basis.     

The concentrations and fate of linear alkylbenzene sulphonate in sludge amended soils

A programme of monitoring work to determine the fate of linear alkylbenzene sulphonates (LAS) in sludge amended soil is described. The concentration of LAS in soils are given for a large number of locations (24 farms and 51 fields) in the Thames Water Authority (TWA), U.K. The sites selected provide a range of soil types, frequency and concentration of sludge applications and agricultural uses (pasture/arable). In addition, the disappearance of LAS from soil with time is shown at three selected sites following different sludge application practices.A solid phase extraction-HPLC method, employing a Soxhlet extraction technique to recover LAS from soil matrices, is described for these determinations which gave an average recovery of LAS (2–15 μgg⁻ spikes) of 97%.In fields (42) not recently spread with sludge (prior to 1987) the concentrations of LAS found in the sludge amended soil are generally less than 1 p g LAS/g soil. When this data is compared with the estimated total cumulative load based on known sludge applications the majority of the sites show losses of LAS > 98%. In fields (9) recently spread (during 1987) the concentrations of LAS in soil are in the range <0.2–20 Mg g⁻¹ representing losses of LAS between 70 and 99% of the estimated total cumulative load. The time course studies confirm the rapid removal of LAS from sludge amended soils at three locations (5 fields) and for three different methods of application. The calculated half-lives for LAS in soil range from 7 to 22 days and agree with laboratory test results and other monitoring studies. The homologue distributions determined for LAS in soil suggest that microbial breakdown rather than leaching is the prime mechanism for its removal. Overall, the data indicate that an adequate safety margin exists between the concentrations of LAS in sludge amended soils and those likely to affect the growth of crop plants.     

Monitoring of dioxin-like, estrogenic and anti-androgenic activities in sediments of the Bizerta lagoon (Tunisia) by means of in vitro cell-based bioassays: contribution of low concentrations of polynuclear aromatic hydrocarbons (PAHs)

We used an array of in vitro cell-based bioassays to assess dioxin-like, estrogenic and (anti-)androgenic activities in organic extracts of sediments from the Bizerta lagoon, one of the largest Tunisian lagoons subjected to various anthropogenic and industrial pressures. The sediments were sampled both in winter and summer 2006 in 6 stations differently impacted and in one reference station located in the seawards entrance of Ghar el Melh lagoon. Chemical analyses of the 16 priority PAHs showed that the sediments were low to moderately contaminated (2-537 ng/g dry weight). By using the estrogen- (MELN) and androgen-responsive (MDA-kb2) reporter cell lines, significant estrogenic and anti-androgenic activities were detected only in the Menzel Bourguiba (MB) site, the most contaminated site, both in winter and summer. By using 7-ethoxyresorufin-O-deethylase (EROD) induction in the fish PLHC-1 cell line after both 4 and 24 h of cell exposure, dioxin-like activities were detected in all analysed samples. Dioxin-like activities were higher after 4 h exposure, and varied according to the sites and the sampling season. While highly significant correlation was observed between bioassay- and chemical analyses-derived toxic equivalents (TEQs), PAHs accounted for only a small part (up to 4%) of the detected biological activities, suggesting that other readily metabolised EROD-inducing compounds were present. This study argues for the use of short time exposure to assess biological TEQs in low contaminated samples and provides new induction equivalent factors (IEF(4h)) for 16 PAHs in the PLHC-1 cell line. Finally, our results stress the need to further characterise the nature of organic chemical contamination as well as its long-term impacts on aquatic wildlife in the Bizerta lagoon.