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.     

Linear alkylbenzene sulfonates in river, estuary and bay water

Linear alkylbenzene sulfonates (LAS) in aquatic environments were determined by combined gas-liquid chromatography and mass spectrometry. The ratios of the concentrations of LAS to those of methylene blue active substances in river and bay water were estimated to 0.40–0.85 and less than 0.20, respectively.The percent composition of LAS varied among commercial detergent, river, estuary and bay water. The cause of the variation in the LAS composition among the aquatic environments is discussed.     

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.     

Selection and evaluation of adsorbents for the removal of anionic surfactants from laundry rinsing water

Low-cost adsorbents were tested to remove anionic surfactants from laundry rinsing water to allow re-use of water. Adsorbents were selected corresponding to the different surfactant adsorption mechanisms. Equilibrium adsorption studies of linear alkyl benzene sulfonate (LAS) show that ionic interaction results in a high maximum adsorption capacity on positively charged adsorbents of 0.6-1.7 gLAS/g. Non-ionic interactions, such as hydrophobic interactions of LAS with non-ionic resins or activated carbons, result in a lower adsorption capacity of 0.02-0.6 gLAS/g. Negatively charged materials, such as cation exchange resins or bentonite clay, have negligible adsorption capacities for LAS. Similar results are obtained for alpha olefin sulfonate (AOS). Cost comparison of different adsorbents shows that an inorganic anion exchange material (layered double hydroxide) and activated carbons are the most cost-effective materials in terms of the amount of surfactant adsorbed per dollar worth of adsorbent.     

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.     

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.     

Bioconcentration of linear alkylbenzene sulfonate (LAS) in bluegill (Lepomis macrochirus)

The potential of the surfactant linear alkylbenzene sulfonate (LAS) to be bioconcentrated in various tissues and organs of bluegill (Lepomis macrochirus) was determined during a 35 day continuous exposure to a mean measured water concentration of 0.5 (±0.05) mg l^{−1 14}C-ring labelled LAS and during a 14 day depuration study. Based on the assumption that all of the ¹⁴C-radioactivity was present as intact LAS, which represents the maximum amount of LAS that could be present, the steady state whole body bioconcentration factor (BCF) was 104 and the muscle BCF was 36. The site of greatest concentration was the gall bladder with a BCF of approx. 5000. The BCF for liver, gills and viscera, remaining carcass, and blood ranged from 64 to 283. Clearance of ¹⁴C-activity from the organs and tissues was rapid with half-lives of 2–5 days. These results on LAS were obtained by both the plateau and kinetic methods of data analysis and are similar to other published data on surfactant bioconcentration.     

Toxicity of anionic detergents determined by Saccharomyces cerevisiae microarray analysis

Sodium n-dodecyl benzene sulfonate (LAS) and sodium dodecyl sulfate (SDS) are popular anionic detergents (surfactants) that are used worldwide and the toxicities of these chemicals have been characterized. We applied these chemicals in a DNA microarray bioassay and determined that the microarray data reflects previous findings and also provides some new information about anionic detergent toxicity. The mRNA expression profiles suggest that LAS and SDS cause damage to membranes and alterations in carbon metabolism, and induce the oxidative stress response. We also found that LAS and SDS induce the pleiotropic drug-resistance network, and that LAS and SDS may be pumped out of yeast cells by this network. Hierarchical clustering of the expression profiles showed that LAS and SDS cause similar features of toxicity and that the toxicity is similar to that of capsaicin but different from that of cadmium and mercury.     

Georeferenced aquatic fate simulation of cleaning agent and detergent ingredients in the river Rur catchment (Germany)

The Geography-referenced regional exposure assessment tool for European rivers (GREAT-ER) 1.0 was developed in the context of environmental risk assessment of chemicals to calculate the aquatic fate of 'down-the-drain' chemicals in surface waters due to point release. As a follow-up project, the river Rur catchment in Germany was incorporated into the system. This included aspects of data collection, modelling and monitoring. Investigated substances are the four detergent and cleaning agent ingredients boron, linear alkylbenzene sulfonate (LAS), nitrilotriacetate (NTA) and ethylenediaminetetraacetate (EDTA). Results of the catchment's incorporation into the system and a comparison of GREAT-ER simulations with different monitoring results are both given. It is shown that data sets derived from a literature review can be used to calculate concentration profiles that are in the range of measured values. Since the model establishes a causal relationship between emission sites and data on the one hand, and observed concentrations in the receiving surface waters on the other, the simulation results can be used to explain monitoring data.     

Occurrence and fate of emerging wastewater contaminants in Western Balkan Region

This paper reports on a comprehensive reconnaissance of over seventy individual wastewater contaminants in the region of Western Balkan (WB; Bosnia and Herzegovina, Croatia and Serbia), including some prominent classes of emerging contaminants such as pharmaceuticals and personal care products, surfactants and their degradation products, plasticizers, pesticides, insect repellents, and flame retardants. All determinations were carried out using a multiresidue analytical approach, based on the application of gas chromatographic and liquid chromatographic techniques coupled to mass spectrometric detection. The results confirmed a widespread occurrence of the emerging contaminants in municipal wastewaters of the region. The most prominent contaminant classes, determined in municipal wastewaters, were those derived from aromatic surfactants, including linear alkylbenzene sulphonates (LAS) and alkylphenol polyethoxylates (APEO), with the concentrations in raw wastewater reaching into the mg/l range. All other contaminants were present in much lower concentrations, rarely exceeding few microg/l. The most abundant individual compounds belonged to several classes of pharmaceuticals (antimicrobials, analgesics and antiinflammatories, beta-blockers and lipid regulators) and personal care products (fragrances). Due to the rather poor wastewater management practices in WB countries, with less than 5% of all wastewaters being biologically treated, most of the contaminants present in wastewaters reach ambient waters and may represent a significant environmental concern.     

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.     

Determination of alkyl benzenesulfonate in water by u.v. method

Alkyl benzenesulfonates in water were determined by u.v. method.Alkyl benzenesulfonates in water were extracted by 1,2-dichloroethane as methylene blue complexes, and, after being isolated from methylene blue by washing with cone. hydrochloric acid, were extracted by water from 1,2-dichloroethane solution.Alkyl benzenesulfonate solutions were measured by absorbance at 222 nm. This band is characteristic of benzene and alkyl benzenesulfonates separated from other anionic surfactants completely.     

Photocatalytic destruction of anionic SAS by ozone and oxygen

The article has investigated photocatalytic destruction of anionic SAS—sodium alkylbenzene sulfate (ABS) in the aqueous medium by ozone on TiO₂ Degussa P-25 at UV radiation by a DB-15 low-pressure mercury-quartz lamp. The paper has determined the parameters of photocatalytic ozonization securing complete ABS destruction (100% in terms of organic carbon). We have assessed advantages of photocatalytic ozonization of ABS solutions compared with photocatalytic oxidation by oxygen and O₃/UV treatment.     

动物蛋白类混凝士发泡剂的制备与发泡性能测试

以氢氧化钠、盐酸和人发为主要原料制备XK型动物蛋白混凝土发泡剂,以十二烷基苯磺酸钠(LAS)、十二烷基硫酸钠(SDS)和明胶3种稳泡剂对合成发泡剂进行复配改性,并对复配发泡剂的稳泡性能进行了分析研究。结果表明,这3种稳泡剂能不同程度提高合成发泡剂的泡沫稳定性,其中以LAS与明胶复配的改性作用最好。     

The behaviour of linear alkyl benzene sulphonate under direct discharge conditions in Vientiane, Lao PDR

Direct discharge of untreated sewage to surface waters is a common practice in many parts of the world. However, relatively little is known about the behaviour of synthetic organic pollutants under these conditions. This paper describes a sampling campaign designed to track changes in water quality in a surface water system in Vientiane (Lao PDR) receiving significant quantities of untreated waste water. The study was based on following in-channel transport using a fluorescent tracer injected as a pulse, with a focus on the anionic surfactant linear alkylbenzene sulphonate (LAS) and ammonia. Water samples were collected at a number of stations with sampling times estimated to coincide with solute time-of-travel. The reduction in LAS concentration with flow-time could be approximated by first-order kinetics with a half life of about 7 h. Free ammonia concentrations decreased more slowly than LAS and remained above the level believed to be toxic for sensitive aquatic species along the entire channel. Changes in the ratios of LAS alkyl chain homologues to total LAS concentrations suggest a preferential removal of longer chain lengths. The role of biodegradation in the removal of LAS was confirmed by the presence of LAS metabolites (sulphophenylcarboxylates, SPCs) which increased systematically (as a fraction of LAS remaining) with flow-time.     

Influence of surfactants on the determination of Cu, Pb and Cd by ASV

In anodic stripping voltammetric studies using a thin film Hg electrode and an acetate buffered base solution containing NaCl, peak currents were found to be influenced by the presence of surfactants of different charge types. The addition of mg l⁻¹ amounts of di-stearyl dimethyl ammonium chloride, lauryl dimethyl-benzyl ammonium chloride, sodium alkyl-benzene sulfonate, sodium salt of sulfonated lauryl alcohol polyoxyethylene condensate, coconut mono-ethanol-amide ethoxylate or octa-decylamine ethoxylate caused enhancement of Cu (20%) and Pb (10%) peaks and suppression of Cd response. The magnitude of the induced changes was not directly related to surfactant type, or experimental parameters, and as a result it is recommended that when analysing waters suspected of containing surfactants, extra care should be taken in the calibration stage.     

Kinetic modeling and synergy quantification in sono and photooxidative treatment of simulated dyehouse effluent

The aim of this work was to explore the application of sulfate radical based advanced oxidation processes: photooxidation (UV/PMS/PS), sonooxidation (US/PMS/PS) and combined sono-photooxidation (US/UV/PMS/PS) for the mineralization of simulated dyehouse effluent (WW); using peroxymonosulfate (PMS) and persulfate (PS) as oxidants. Experiments were performed in a reaction vessel of a defined geometry and axially positioned source of UV-C radiation, all placed in the ultrasonic bath (35 kHz). Mathematical model of the process was developed according to the proposed degradation scheme. Decomposition of dyestuff (C.I. Reactive Violet 2, RV2 and C.I. Reactive Blue 7, RB7), surfactant (linear alkylbenzene sulfonate; hereafter: LAS) and auxiliary organic components was explored in three types of model wastewater: WW, simulated effluent excluding inorganic species (WW-IS) and model solution that consists of a specific compound (hereafter: compound model solutions). The influence of inorganic matrix (Cl⁻, CO₃²⁻/HCO₃⁻) was studied due to the corresponding quenching affinity toward HO and SO₄⁻ radicals. The efficiency of applied processes was evaluated and the response to combined phenomena (cavitation and irradiation) was quantified as synergy index, f_Syn. Sono-photooxidative treatment (US/UV/PMS/PS) of WW resulted in a partial mineralization and partial decolourization; approximately 40% of initial TOC and 30% of initial RB7 remained after 60 min of treatment, while RV2 and LAS molecule were completely decomposed. Circumstantially, the combined process increased the mineralization efficiency by a factor of 3 (f_Syn = 3.026).     

Occurrence and hazard screening of alkyl sulfates and alkyl ethoxysulfates in river sediments

Alkyl sulfates (AS) and alkyl ethoxysulfates (AES) are High Production Volume (HPV) 'down-the-drain' chemicals widely used globally in detergent and personal care products, resulting in low levels (ng to microg L(-1) range) ultimately released to the environment via wastewater. These surfactants have a strong affinity for sorption to sediments. However, data regarding the fate and effects following release into the environment has not been reported. Sediment samples from both normal exposed and presumably low exposed locations (background) were analyzed to determine the levels of AS/AES. The method used in this study shows broad applicability across various sediment types and the most common congeners of AS/AES. The combined levels of AS/AES detected in the two presumed lower exposed sites ranged from 0.025 and 0.034 microg g(-1) on a dry weight (dw) basis while the presumed higher exposed site had combined levels of AS/AES of 0.117 microg g(-1) (dw) based on triplicate analyses. Results indicate that detectable levels of AS/AES can be found in sediments in the environment at these three sites that are below the concentrations expected to produce significant adverse ecological effects for individual homologues and the whole mixture, the hazard screening for these three sites had PEC(porewater)/PNEC(total mixture) ratios of 0.007-0.024. However, further investigation of potential effects and risk assessment is warranted.     

Chemical treatment of an anionic surfactant wastewater: Electrospray-MS studies of intermediates and effect on aerobic biodegradability

The effect of wet air oxidation on the aerobic biodegradability of a model wastewater containing 1000 mg L(-1) of linear alkylbenzene sulfonate (LAS) has been investigated. Semibatch oxidation experiments were performed temperature of 473 K, oxygen partial pressure of 1.3 MPa and residence times varying from 40 to 390 min, while continuous oxidation experiments were performed at a residence time of 120 min. Oxygen uptake tests were performed to assess the aerobic biodegradability of both the oxidised and the original LAS solutions using cultures that had been adapted to both LAS and oxidation intermediates. The concentration of total organic carbon, chemical oxygen demand and active detergent were followed throughout the wet oxidation and biodegradation experiments, while the main intermediates formed during wet oxidation were identified by means of Electrospray-MS and high performance liquid chromatography. It was found that LAS could be easily oxidised at 473 K to yield a group of molecules with short alkyl chains which do not behave as active detergents. Sulfonated aromatics are produced as intermediates which have had the alkyl chains shortened. The segments of alkyl chains broken off the intermediate compounds appear primarily as short chain organic acids. The original unoxidised 1000 mg L(-1) LAS solution was found to be readily biodegradable in the laboratory aerobic reactors operating at low organic loadings and substrate to microorganism concentration ratios. However, wet oxidation resulted in effluents that were less readily biodegradable than the original LAS with biodegradability decreasing with increasing degree of oxidation. These results suggest that, at the conditions under consideration, a combined chemical pre-oxidations and biological post-treatment process may be less effective in removing LAS than a single-stage biological or chemical process.     

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.