Structural control of the non-ionic surfactant alcohol ethoxylates (AEOs) on transport in natural soils.

Surfactants, after use, enter the environment through diffuse and point sources such as irrigation with treated and non-treated waste water and urban and industrial wastewater discharges. For the group of non-ionic synthetic surfactant alcohol ethoxylates (AEOs), most of the available information is restricted to the levels and fate in aquatic systems, whereas current knowledge of their behavior in soils is very limited. Here we characterize the behavior of different homologs (C12-C18) and ethoxymers (EO3, EO6, and EO8) of the AEOs through batch experiments and under unsaturated flow conditions during infiltration experiments. Experiments used two different agricultural soils from a region irrigated with reclaimed water (Guadalete River basin, SW Spain). In parallel, water flow and chemical transport were modelled using the HYDRUS-1D software package, calibrated using the infiltration experimental data. Estimates of water flow and reactive transport of all surfactants were in good agreement between infiltration experiments and simulations. The sorption process followed a Freundlich isotherm for most of the target compounds. A systematic comparison between sorption data obtained from batch and infiltration experiments revealed that the sorption coefficient (Kd) was generally lower in infiltration experiments, performed under environmental flow conditions, than in batch experiments in the absence of flow, whereas the exponent (ß) did not show significant differences. For the low clay and organic carbon content of the soils used, no clear dependence of Kd on them was observed. Our work thus highlights the need to use reactive transport parameterization inferred under realistic conditions to assess the risk associated with alcohol ethoxylates in subsurface environments.

Aerobic biodegradation of linear alkylbenzene sulfonates and sulfophenylcarboxylic acids for different salinity values by means of continuous assays.

Aerobic biodegradation of linear alkylbenzene sulfonates (LAS) and sulfophenylcarboxylic acids (SPCs) in water, at different salinity values, has been studied. Three experiments have been carried out employing a staircase model system with continuous dosage of LAS to the system and using concentrations of LAS of the same order as those detected in littoral waters receiving urban wastewater discharges. LAS biodegradation was observed to be almost complete (showing a great extent), and in all cases exceeds 98.4%. At the very low concentration values of LAS utilized in the experiments, no significant variations in the biodegradation of LAS due to the effect of the different salinity values assayed were observed. The biodegradation intermediates detected for all the cases were sulfophenylcarboxylic acids with carboxylic chains of between five and 13 carbon atoms. The detection of C13-SPC (which is only produced by C13-LAS) confirms the existence of omega-oxidation. The total disappearance of SPCs in all cases indicates that mineralization of LAS at the concentrations tested was complete.

Oxidative stress and histopathology damage related to the metabolism of dodecylbenzene sulfonate in Senegalese sole.

Surfactants such as linear alkylbenzene sulfonates (LAS) are widely utilised in the formulation of detergents in commercial products. After use, they pass through waste water treatment plants (WWTP) and are then discharged to aquatic ecosystems, causing risk to aquatic life. The exposure of marine animals to these compounds enhances the production of reactive oxygen species (ROS) with subsequent damage to macromolecules, and produces histological alterations. A flow-through experiment with Senegalese sole (Solea senegalensis) has been devised with the object of correlating the metabolism of LAS including sulfophenylcarboxylic acids (SPCs) by fish with their antioxidant defence system (generation of oxyradicals) and histopathological damage. The generation of intermediate degradation products (SPCs) by the organism, the histopathological responses, the antioxidant enzymes (catalase (CAT), glutathione peroxidase (GPX), glutathione reductase (GR), and glutathione S-transferase (GST)), as well as other kinds of enzyme such as acid and alkaline phosphatases (AcP, ALP), were measured. SPCs from 5ØC(6) to 11ØC(12) were identified and quantified in fish and water; their concentrations differed depending on the sampling moment. In general, the responses found in the enzymes were slight: a decrease in the enzymatic activity in gills and activation in the digestive tract. The evidence of histopathological damage identified was also small; the organism's defensive mechanism against pollutants should enable it to recover easily. A direct relationship was established between biotransformation and the generation of SPCs and ROS. In conclusion, the correct functioning of the antioxidant defence system with absence of large variations, the short-term histopathological damage, and the evidence of SPCs indicate an adequate metabolism of 2-phenyl-C(12)-linear alkylbenzene sulfonates (2ØC(12)LAS) by this specie and non-toxic effects at environmentally realistic levels.

Suitability of the marine prosobranch snail Hydrobia ulvae for sediment toxicity assessment: A case study with the anionic surfactant linear alkylbenzene sulphonate (LAS).

Individuals of the mudsnail Hydrobia ulvae (Pennant) (Mollusca: Prosobranchia) were exposed to sediments spiked with increasing concentrations (1.59-123.13mgkg(-1) dry weight) of the anionic surfactant linear alkylbenzene sulphonate (LAS) which is employed in the formulation of laundry powders and liquids, as well as hand dishwashing products. The suitability of the selected organism, H. ulvae for routine sediment toxicity testing was evaluated by measuring acute toxicity recording survival. Sublethal toxicity was evaluated as total number of produced veliger larvae per treatment throughout the test (9d). Mortality has shown to be a reliable and reproducible indicator of acute toxicity. LC(50) values were comprised between 203.4 (48h) and 94.3mgkg(-1) (9d) dry weight. As sublethal endpoint, the total number of produced larvae showed to be a useful indicator of toxicity for this organism. The number of produced larvae increased at lower exposure concentrations, whereas at the highest LAS concentration, the number of produced larvae decreased. This is the first report of acute and sublethal toxicity of sediment associated LAS for this species.

Testing organic solvents for the extraction from fish of sulfophenylcarboxylic acids, prior to determination by liquid chromatography-mass spectrometry.

The present paper describes the use of different solvent mixtures to extract from fish various sulfophenylcarboxylic acids (SPCs of C(6) to C(13)), and their originating compounds, linear alkylbenzene sulfonates (LAS of C(10) to C(13)). The analytical method utilized involves pressurized liquid extraction, followed by preconcentration of the samples, purification by solid-phase extraction, and finally identification and quantification of the target compounds by high-performance liquid chromatography-mass spectrometry using a system equipped with an electrospray interface operating in negative ion mode. The SPCs and LAS were extracted from spiked fish first with hexane to remove interference from fats, then with different mixtures of solvents: dichloromethane followed by methanol; 50:50 dichloromethane-methanol; and 30:70 dichloromethane-methanol. The LAS recoveries obtained with these three extraction options were high (between 68.5 and 80.8%); however, owing to the low percentages obtained for SPC homologues (13.5, 13.1, and 15.9%, respectively), another extraction procedure with methanol was developed in order to increase these recoveries. The percentage of recovery for total SPCs with the methanolic extraction was higher (90.1%), with a standard deviation of 9.9, and the LAS recoveries also increased (99.9%). Detection limits were between 1 and 22 ng g(-1) for LAS, and between 1 and 58 ng g(-1) for SPCs. Quantitation limits were between 4 and 73 ng g(-1) for LAS, and between 2 and 193 ng g(-1) for SPCs. This method has been applied to measure the biotransformation of 2ØC(10) LAS (where Ø is a sulfophenyl group) in fish exposed in a flow-through system, and enabled the separation and identification of SPCs from 5ØC(6) to 9ØC(10).

Derivation of predicted no effect concentrations (PNEC) for marine environmental risk assessment: application of different approaches to the model contaminant Linear Alkylbenzene Sulphonates (LAS) in a site-specific environment.

Four sediment-dwelling marine organisms were exposed to sediments spiked with increasing concentrations of Linear Alkylbenzene Sulphonate (LAS). The selected endpoint mortality was reported daily and acute LC(50) (96 h), as well as final LC(10) values were calculated for the derivation of environmentally safe predicted no effect concentrations (PNEC) for the sediment compartment. PNECs were estimated by both application of assessment factors (AF) and the equilibrium partitioning method (EPM) as proposed by the EU TGD. Finally, environmental risk assessment in a site-specific environment, the Sancti Petri Channel, South Iberian Peninsula, was carried out at three different sampling stations with known environmental LAS concentrations. PNECs obtained by the assessment factor approach with acute toxicity data were one to two orders of magnitude lower than those from the equilibrium partitioning method. On the other hand, when applying lower AFs to the estimated LC(10) values, the PNECs obtained by both approaches were more similar. Environmental risk assessment carried out with the estimated PNECs in a site specific environment with known sediment LAS concentrations revealed that PNECs obtained with acute toxicity data were over conservative whereas those obtained with AF=10 on LC(10) data and EPM produced more realistic results in accordance with field observations carried out in the study area.

Presence, biotransformation and effects of sulfophenylcarboxylic acids in the benthic fish Solea senegalensis.

The presence of linear alkylbenzene sulfonates (LAS) and their degradation intermediates, sulfophenylcarboxylic acids (SPCs), with concentrations up to 100 ppb has been found in surface waters taken from the estuary of the river Guadalete (Cádiz, SW of Spain). Higher concentrations were found at the sampling site located adjacent to the discharge outlet of a wastewater treatment plant (WWTP). The concentrations decreased downstream to a few ppb as a result of dilution, sorption, and degradation processes, which were taking place along the estuary. Once the presence of both xenobiotics was confirmed in the environment, an in vivo assay was conducted to study their biotransformation and effects in the benthic fish Solea senegalensis. A flow-through system was employed, consisting of an exposure phase (120 h) with environmental levels of the surfactant (200, 500 and 800 microg/L of 2ØC(10)LAS), followed by a depuration stage (72 h). The generation of SPCs has been quantified during these phases in both water and fish, with LAS biotransformation shown in all cases. The antioxidant enzymes catalase (CAT), glutathione peroxidase (GPX), glutathione reductase (GR), the phase II enzyme glutathione S-transferase (GST), and the phase III acid and alkaline phosphatases (AcP, ALP) were also estimated and utilized as biomarkers.

Presence of surfactants and their degradation intermediates in sediment cores and grabs from the Cadiz Bay area.

The occurrence and distribution of the major surfactants--LAS, AES, APEOs and AEOs--and their degradation intermediates--SPCs, AP and APECs--in a marine-estuarine environment at Spain are presented. Results show that their concentration in surface sediments is clearly correlated with their usage and the existence of wastewater discharges. The degradation processes appear to lead to the formation of SPCs in the case of LAS, and to the shortening of the average ethoxylated chain length in the case of NPEOs, AEOs and AES. Vertical profiles for AEOs and AES are reported for the first time and present the highest values nearest the surface, followed by a sharp decrease with depth for all surfactants, as well as the appearance of degradation intermediates in deeper sedimentary layers. Shorter LAS homologues and SPCs tend to be present in pore water while strongly non-polar intermediates like NP are firmly attached to the sediments.

Removal of linear alkylbenzene sulfonates and their degradation intermediates at low temperatures during activated sludge treatment.

The degradation of linear alkylbenzene sulfonates and their degradation intermediates (sulfophenylcarboxylic acids) has been characterized at 9 degrees C in an activated sludge pilot plant. After an adequate adaptation period (20 days), LAS primary degradation exceeds 99% and takes place preferentially for long alkyl chain homologues and external isomers. LAS homologues in the reactor are preferentially sorbed onto particulate matter, while sulfophenylcarboxylic acids (SPCs) are present predominantly in solution, due to their lower hydrophobicity. During the adaptation period the most abundant LAS biodegradation intermediates were long chain sulfophenylcarboxylic acids (SPCs) (C(9)-C(13)SPC). However once this system is fully adapted, the microorganisms are capable of degrading SPCs efficiently. SPCs with 7-9 carbon atoms in the carboxylic chain predominate due to their degradation being slower than for the rest of the SPCs. The presence of C(13)SPC confirms that LAS degradation in wastewater starts with a omega-oxidation on the alkylic chain. A preferential degradation of SPC isomers of the types 2phiC(n)SPC to 6phiC(n)SPC was also detected, as shown by the relatively higher SPC concentrations of the remaining ones.

New extraction method for the analysis of linear alkylbenzene sulfonates in marine organisms. Pressurized liquid extraction versus Soxhlet extraction.

A new method has been developed for the determination of linear alkylbenzene sulfonates (LAS) from various marine organisms, and compared with Soxhlet extraction. The technique applied includes the use of pressurized liquid extraction (PLE) for the extraction stage, preconcentration of the samples, purification by solid-phase extraction (SPE) and analysis by liquid chromatography with fluorescence detection. The spiked concentrations were added to the samples (wet mass of the organisms: Solea senegalensis and Ruditapes semidecussatus), which were homogenized and agitated continuously for 25 h. The samples were extracted by pressurized hot solvent extraction using two different extraction temperatures (100 and 150 degrees C) and by traditional Soxhlet extraction. The best recoveries were obtained employing pressurized hot solvent extraction at 100 degrees C and varied in the range from 66.1 to 101.3% with a standard deviation of between 2 and 13. Detection limit was between 5 and 15 microg kg(-1) wet mass using HPLC-fluorescence detection. The analytical method developed in this paper has been applied for LAS determination in samples from a Flow-through exposure system with the objective of measuring the bioconcentration of this surfactant.

Vertical distribution profiles of linear alkylbenzene sulfonates and their long-chain intermediate degradation products in coastal marine sediments.

The variation with depth of the concentration of linear alkylbenzene sulfonates (LASs) and of the long-chain sulfophenyl carboxylic acids (SPCs) resulting from LAS biodegradation was determined in coastal sediments. We analyzed samples of sediment cores taken from three locations in a littoral zone subjected to the discharge of untreated urban effluents in the Bay of Cádiz in the southwestern part of the Iberian Peninsula. The vertical profile of LAS concentrations showed a sharp reduction with depth, whereas the concentration of long-chain SPCs (6-13 carbon atoms) was greatest at 10 to 14 cm depth. At this depth, the conditions in the interstitial water are strictly anoxic (Eh = -380 mV). The partition coefficients between the solid phase of the sediment versus the interstitial water are very different for LAS and for its degradation intermediates. For LAS, the organic carbon-based partition coefficient values were between 2.4 x 10(3) and 6.6 x 10(5)L/kg for the C10 and C13 homologues, respectively; these values are similar to those obtained from laboratory tests for the sorption of LAS onto marine sediments. For the long-chain SPCs, the partition coefficients are several orders of magnitude less as a consequence of their lower hydrophobicity.

Determination of sulfophenylcarboxylic acids in marine samples by solid-phase extraction then high-performance liquid chromatography.

An analytical method is presented for the determination of sulfophenylcarboxylic acids (SPC) produced by the biodegradation of linear alkylbenzene sulfonates (LAS) in marine samples. Isolation and concentration of the compounds was by solid-phase extraction. The different factors affecting extraction efficiency packing composition, pH, clean-up, ionic strength, and elution solvents--were studied and optimized. With the proposed method C4-C13SPC and C10-C13 LAS recoveries varied between 65% and 105%, with standard deviations between 0.1 and 5, respectively, for 100-mL samples and 100 microg L(-1) concentrations of each homolog. Detection limits within the range 0.5 g L(-1) (for C4SPC) to 1.0 g L(-1) (for C12SPC) were obtained by liquid chromatography with fluorescence detection. This method is the first to be proposed that enables the simultaneous determination of monocarboxylic SPC (C>3) and LAS homologs in marine samples by a simple, sensitive, and specific method giving high recoveries and reproducibility. SPC with from three to twelve carbon atoms in the carboxyl chain have been found in marine water samples.

Bioconcentration of linear alkylbenzene sulfonates and their degradation intermediates in marine algae.

Sorption experiments using different homologues of linear alkylbenzene sulfonate (LAS) and sulfophenylcarboxylic acid (SPC) on several marine microalgae have been carried out. The steady state seems to be reached in the first 4 hours. Longer exposure times lead to biodegradation of the compound and, therefore, to an overestimation of the bioconcentration factor. Sorption coefficients are higher for Nannochloropsis gaditana, for example, 1,293 Lkg(-1) for C11-LAS and 525 Lkg(-1) for C11-SPC versus 727 Lkg(-1) for C11-LAS and 28 Lkg(-1) for C11-SPC for Dunaliella salina. For both algae an increase in the sorption coefficient is observed when the polarity of the compound decreases (C5-SPC

Extraction and isolation of linear alkylbenzene sulfonates and their intermediate metabolites from various marine organisms.

A method has been developed for the determination of linear alkylbenzene sulfonates and its degradation intermediates (sulfophenylcarboxylic acids) from different marine organisms, which includes the stages of extraction and analysis by liquid chromatography with fluorescence detection. The extraction stage (Soxhlet and solid-phase extractions) was optimised by the selection of the appropriate solvent, minicolumns and different clean-up stages. Recoveries varied in the range from 80 to 104%, with a standard deviation between 1 and 9%. Detection limits were 15 ng g(-1) wet mass for undecylbezene sulfonate and 30 ng g(-1) wet mass for sulfophenylundecanoic acid using HPLC-fluorescence detection. The complete analytical method was successfully applied to different marine organisms from the Bay of Cadiz (SW Spain).

Inter-laboratory comparison of liquid chromatographic techniques and enzyme-linked immunosorbent assay for the determination of surfactants in wastewaters.

Seven laboratories participated in an inter-laboratory comparison exercise within the framework of the PRISTINE, SANDRINE and INEXsPORT European Union Projects. Solid-phase extraction (SPE) methodologies were used for the extraction of target analytes from wastewaters. The analytical strategies were based on liquid chromatography (LC) coupled to mass spectrometric (MS) or to fluorescent (FL) detection in all cases with the exception of one laboratory using a test-tube enzyme-linked immunosorbent assay kit. Samples were spiked with the surfactants nonylphenolpolyglycol ether, coconut diethanolamide, linear alkylbenzene sulfonate, nonylphenolpolyglycol ether sulfate, alkylpolyglycol ether and secondary alkane sulfonate. After enrichment on previously conditioned SPE cartridges, the SPE cartridges were distributed among the participating laboratories without the information about the amount of spiked surfactants. In addition, SPE cartridges loaded with a real-world environmental sample containing a tannery wastewater were also analyzed. The results of the programme showed that SPE followed by LC-MS techniques are reliable for the surfactants determination at submicrogram to microgram per liter levels in wastewaters. Inter-laboratory precision values were calculated as the reproducibility relative standard deviation (RSD(R)) which was determined from the reproducibility standard deviation (sR) and the average concentration at a particular concentration level. When data from all laboratories were pooled, the RSD(R) values ranged from 5.1 to 28.3% for the determination of target analytes. The most accurate result corresponded to that given for linear alkylbenzene sulfonates. Taking into account that different methodologies were used (including non-chromatographic techniques) and the complexity of the samples analyzed, it can be considered that acceptable reproducibility values were obtained in this inter-laboratory study.

Handling of marine and estuarine samples for the determination of linear alkylbenzene sulfonates and sulfophenylcarboxylic acids.

Due to the physicochemical properties of linear alkylbenzene sulfonates (LAS), an anionic surfactant, it is difficult to obtain representative samples from sampling sites. Further, the high biodegradability of these compounds makes it necessary to study their biodegradation intermediates, sulfophenylcarboxylic acids (SPC) that do not have a surfactant character and show a different behavior. A procedure for determining and quantifying LAS and SPC in different environmental matrices by Soxhlet and solid-phase extractions and high-performance liquid chromatography is presented. The recoveries varied in the range from 85 to 102% for the water samples, and from 75 to 105% for sediment samples, with a standard deviation of between 1 and 7, and 2 and 11, respectively. Detection limits obtained were in the range from 5 to 10 microg kg(-1) for sediment samples (10 g) and from 0.2 to 0.4 microg l(-1) for water samples (250 ml). The method was applied to the simultaneous determination of LAS (C10-C13) and SPC (C4-C13) homologues in water, sediment and interstitial water collected from different areas of Spain.