Fate of the Benzene Ring of Linear Alkylbenzene Sulfonate in Natural Waters

The relative risk and its distribution of endocrine disrupting chemicals, pharmaceuticals and personal care products to freshwater organisms in the Bohai Rim, China

In this study, the risks to aquatic organisms posed by 12 commonly detected pharmaceuticals and personal care products (PPCPs) and endocrine disrupting chemicals (EDCs) that are extensively used in Bohai coastal region of China were examined. These were linear alkylbenzene sulfonate (LAS), nonylphenol (NP), diethylhexyl phthalate (DEHP), norfloxacin (NOR), sulfamethoxazole (SMX), erythromycin (ERY), bisphenol A (BPA), ofloxacin (OFL), carbamazepine (CBZ), naproxen (NPX), atenolol (ATL) and metoprolol (MET). Their relative risk was ranked based on the proximity between the medians of the reported effect concentrations and measured river or lake water concentrations. The surfactants (LAS) and endocrine disrupting chemicals NP (a breakdown product of the surfactant nonylphenol polyethoxylate) and DEHP (a plasticizer) were identified as posing the greatest risk from this range of chemicals. LAS had a hundred-fold higher risk than any of the pharmaceuticals. The highest risk ranked pharmaceuticals were all antibiotics. Zinc (Zn) and mercury (Hg) were added to the comparison as representative heavy metals. Zn posed a risk higher than all the organics. The risk posed by Hg was less than the surfactants but greater than the selected pharmaceuticals. Whereas LAS and DEHP could cause harmful effects to all the wildlife groups, NP and BPA posed the greatest risk to fish. Antibiotics showed the highest risk to algae. Spatial and temporal distributions of PPCPs and EDCs were conducted for risk identification, source analysis and seasonal change exploration. Municipal sewage effluent linked to urban areas was considered to be the major source of pharmaceuticals. With regard to seasonal influence the risk posed by LAS to the aquatic organisms was significantly affected by wet and dry seasonal change. The dilution effects were the common feature of LAS and ERY risks. The difference in LAS and ERY risk patterns along the rivers was mainly affected by the elimination process.

Environmental Safety of the Use of Major Surfactant Classes in North America

This paper brings together over 250 published and unpublished studies on the environmental properties, fate, and toxicity of the four major, high-volume surfactant classes and relevant feedstocks. The surfactants and feedstocks covered include alcohol sulfate or alcohol sulfate (AS), alcohol ethoxysulfate (AES), linear alkylbenzene sulfonate (LAS), alcohol ethoxylate (AE), and long-chain alcohol (LCOH). These chemicals are used in a wide range of personal care and cleaning products. To date, this is the most comprehensive report on these substance's chemical structures, use, and volume information, physical/chemical properties, environmental fate properties such as biodegradation and sorption, monitoring studies through sewers, wastewater treatment plants and eventual release to the environment, aquatic and sediment toxicity, and bioaccumulation information. These data are used to illustrate the process for conducting both prospective and retrospective risk assessments for large-volume chemicals and categories of chemicals with wide dispersive use. Prospective risk assessments of AS, AES, AE, LAS, and LCOH demonstrate that these substances, although used in very high volume and widely released to the aquatic environment, have no adverse impact on the aquatic or sediment environments at current levels of use. The retrospective risk assessments of these same substances have clearly demonstrated that the conclusions of the prospective risk assessments are valid and confirm that these substances do not pose a risk to the aquatic or sediment environments. This paper also highlights the many years of research that the surfactant and cleaning products industry has supported, as part of their environmental sustainability commitment, to improve environmental tools, approaches, and develop innovative methods appropriate to address environmental properties of personal care and cleaning product chemicals, many of which have become approved international standard methods.

LAS degradability by marine biofilms derived from seawater in Spain and Sweden

Marine biofilms were established on glass beads with or without deliberate pre-exposure to LAS (20 μg/L) in Spain (Cadiz) and Sweden (Kristineberg). The ability of each community to mineralize LAS (100 μg/L) was then assessed in biometers at four experimental temperatures (between 6 and 21°C). Genetic diversity and biomass of the biofilms were assessed by genetic fingerprinting (DGGE) and direct bacterial counts. With biofilms from Sweden, where LAS was not detected in seawater (n = 3), deliberate pre-exposure to LAS resulted in lower genetic diversity and higher mineralization rate constant; however, with biofilms from Spain, where 6.4 ± 3.9 μgLAS/L (n = 3) was measured during the colonization, pre-exposure did not affect the bacterial community. Bacterial acclimation therefore appeared to have been induced at environmental concentrations < 6 μgLAS/L. Environmental pre-exposure was not a pre-requisite for featuring the full consortia of LAS degraders in the biometers. The mineralization rate was described using an Arrhenius equation at experimental temperatures within the typical annual range; however, they departed from this model below this range.

Mineralization of linear alkylbenzene sulfonate by a four-member aerobic bacterial consortium

A bacterial consortium capable of linear alkylbenzene sulfonate (LAS) mineralization under aerobic conditions was isolated from a chemostat inoculated with activated sludge. The consortium, designated KJB, consisted of four members, all of which were gram-negative, rod-shaped bacteria that grew in pairs and short chains. Three isolates had biochemical properties characteristic of Pseudomonas spp.; the fourth showed characteristics of the Aeromonas spp. Cell suspensions were grown together in minimal medium with [C]LAS as the only carbon source. After 13 days of incubation, more than 25% of the [C]LAS was mineralized to CO(2) by the consortium. Pure bacterial cultures and combinations lacking any one member of the KJB bacterial consortium did not mineralize LAS. Three isolates carried out primary biodegradation of the surfactant, and one did not. This study shows that the four bacteria complemented each other and synergistically mineralized LAS, indicating catabolic cooperation among the four consortium members.

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.

Fate, behavior and effects of surfactants and their degradation products in the environment

Surfactants are widely used in household and industrial products. After use, surfactants as well as their products are mainly discharged into sewage treatment plants and then dispersed into the environment through effluent discharge into surface waters and sludge disposal on lands. Surfactants have different behavior and fate in the environment. Nonionic and cationic surfactants had much higher sorption on soil and sediment than anionic surfactants such as LAS. Most surfactants can be degraded by microbes in the environment although some surfactants such as LAS and DTDMAC as well as alkylphenols may be persistent under anaerobic conditions. LAS were found to degrade in sludge amended soils with a half-lives of 7 to 33 days. Most surfactants are not acutely toxic to organisms at environmental concentrations and aquatic chronic toxicity of surfactants occurred at concentrations usually greater than 0.1 mg/L. However, alkylphenols have shown to be capable of inducing the production of vitellogenin in male fish at a concentration as low as 5 microg/L. More toxicity data are needed to assess the effects on terrestrial organisms such as plants.

Biodegradation of linear alkylbenzene sulfonates and their degradation intermediates in seawater

A study has been made of the aerobic biodegradation of linear alkylbenzene sulfonates (C12 and C11 homologues) and sulfophenylcarboxylic acids (C5 and C11 homologues) in seawater at concentrations of the same order as those detected ones in coastal waters influenced by wastewater effluents, at different temperatures, and both with and without the addition of an inoculum adapted to the presence of linear alkylbenzene sulfonate (LAS). The biodegradation of C12LAS, C11LAS, C5SPC, and C11SPC exceeds 99% in all tests performed and can be satisfactorily fitted to a second-degree polynomial without an independent term. The kinetic of degradation of LAS presents a clear seasonal component, since the process is considerably inhibited at lower temperatures; it is also kinetically enhanced by the presence of the inoculum. The intermediates detected for all the cases are sulfophenylcarboxylic acids (SPCs), the most abundant being those intermediates produced by the omega- and beta-oxidations of the parent compound, although intermediates produced by the alpha-oxidation have also been detected. The kinetic of the SPCs generated can be described using a model composed of two terms that represent the formation and the degradation of these intermediates. The total disappearance of the SPCs in all cases indicates that the degradation of LAS in seawater at the tested concentrations in aerobic conditions is complete.

Incomplete degradation of linear alkylbenzene sulfonate surfactants in Brazilian surface waters and pursuit of their polar metabolites in drinking waters

In Brazil more than 90% of the population are not connected to municipal wastewater treatment plants. As a consequence, surface waters receive continuously considerable amounts of untreated domestic sewage containing surfactants as a major constituent. Such polluted waters gave rise to special interest if they are used as a source for the production of drinking water. In this work, the river Rio Macacu (State Rio de Janeiro, Brazil) was monitored for the occurrence of the most widely used anionic surfactant linear alkylbenzene sulfonate (LAS) together with its main degradative product, sulfophenyl carboxylates (SPC). In order to pursue the fate of both compounds after emission into the river, samples were collected at several locations along the river bank, and analyzed applying liquid chromatography-mass spectrometry after enrichment by solid-phase extraction. The LAS concentrations ranged between 14 and 155 microg l(-1) and the levels of their metabolic intermediates were found from 1.2 to 14 microg l(-1). The self-purification capacity of the water was impressively demonstrated in the upper course of the river downstream of a town considered as one major discharge point, whereas in the lower course the relative constant concentrations of both analytes were detected which was explained with an overall increasing level of pollution. Furthermore, a series of drinking water samples from Niterói and São Gonçalo, supplied by the same waterworks treating surface waters from the Rio Macacu, were taken during two sampling periods and examined for the presence of the strongly polar SPC which is suspected of by-passing the purification processes. The levels detected in the drinking water ranged between 1.6 and 3.3 microg l(-1). For the analyses of drinking and surface waters the peak pattern of a selected SPC homologue composed by several positional isomers served as an indicator to describe the progression of SPC degradation occurred in the river and could be used to distinguish drinking waters of different origins.

Degradation of sodium 4-dodecylbenzenesulphonate photoinduced by Fe(III) in aqueous solution

The Fe(III)-photoinduced degradation of 4-dodecylbenzenesulphonate (DBS) in aqueous solution was investigated. The mixing of DBS (1 mm) and Fe(III) (1 mm) solutions immediately led to the formation of a precipitate that contained DBS and monomeric Fe(OH)2+, the predominant Fe(III) species. Both species were also present in the supernatant. Irradiation of the supernatant solution resulted in a photoredox process that yielded Fe(II) and *OH radicals. The disappearance of DBS was shown to involve only attack by *OH radicals; the quantum yield of DBS disappearance is similar to the quantum yield of *OH radical formation. A wavelength effect was also observed; the rate of DBS disappearance was higher for shorter wavelength irradiation. Five photoproducts, all containing the benzene sulphonate group, were identified. *OH radicals preferentially abstract hydrogen from the carbon in the alpha position of the aromatic ring. The results show that the Fe(III)-photoinduced degradation of DBS could be used as an alternative method for polluted water treatment.

Biodegradation kinetics of surfactants in seawater

In this paper, a general kinetic model for degradation processes of surfactants is proposed. The model equation is v = K2S2 + K1S + K0, where v is the substrate consumption rate in the biodegradation process, S is the surfactant concentration in the medium and K2, K1, and K0 are kinetic constants. From this general expression, different simplified equations can be obtained (where K0 = 0; K2 and K0 = 0; K2 = 0; K2 and K1 = 0), which are representative of the process for different operating conditions. This model was tested by measuring the degradation of two different surfactants (Sodium dodecyl benzene sulfonate, LAS; and Sodium dodecyl sulfate, DSNa) under two different temperatures (5 and 20 degrees C). Values predicted by the model are close to experimental data obtained.

Impact of biodegradation test methods on the development and applicability of biodegradation QSARs

The biodegradability of a substance depends on the structure and physical form of the substance, the time that has been available for acclimation, and the environmental conditions. Importantly, these later factors can be just as important as structure in determining the outcome of a biodegradation test. The development of appropriate QSARs for biodegradation and the ultimate value of the final QSAR depends on understanding these factors. This paper will describe what is known about the effect of test conditions on the results of biodegradation tests. The ability of these tests to reflect real environmental conditions will also be examined. Finally, we will discuss what we believe, in the light of this information, should be the goal of biodegradation QSARs and how these QSARs can be most appropriately used in fate assessments.

Biodegradation of linear alkylbenzenesulphonates (LAS) by mixed methanotrophic-heterotrophic cultures

The biodegradation of undecylbenzenesulphonate (C11LAS) was studied in shake flasks at 21 degrees C using two mixed bacterial cultures. The first culture, MM1, contained a type II methanotroph and four heterotrophs, and was enriched from a groundwater aquifer. The second culture, MC, consisted of five heterotrophic strains, most of them belonging to the genus Pseudomonas, and was isolated from the wastewater of a detergent plant. Methane, carbon dioxide and oxygen concentrations were determined by gas chromatography. Concentrations of C11LAS and the aromatic intermediates were determined by reversed-phase HPLC. In spite of faster transformation of the alkyl side-chain by the culture MC, the culture MM1 containing type II methanotroph was capable of further degradation of C11LAS aromatic intermediates (sulphophenylalkanoates). The most probable mechanism for the degradation of the alkyl part of the C11LAS molecule by both cultures was omega-oxidation of the terminal methyl group followed by beta-oxidation. Studies of methane utilization demonstrated an approximately three times higher second-order rate coefficient for methane consumption (kmax/Ks) in the absence of C11LAS. This indicates a possible metabolic activity of methanotrophs in the transformation of the complex LAS molecule due to the methane monooxygenase enzyme system.

Biodegradation kinetics of linear alkylbenzene sulfonate in sludge-amended agricultural soils

The kinetics of ultimate biodegradation (mineralization to CO2) of linear alkylbenzene sulfonate (LAS) were studied in sludge-amended agricultural soils for a series of pure chain length LAS homologs containing 10 to 14 carbon atoms in the alkyl chain. Degradation rates were measured by following the production of 14CO2 from uniformly 14C-ring-labeled material. In general, degradation of LAS was rapid in soil over a broad concentration range (0.1 to 10 times the expected environmental concentration) and demonstrated little variation among different homologs. Half-lives for mineralization of the benzene ring ranged from 18 to 26 days and were not significantly different for any homolog over the range of alkyl chain lengths tested. Half-lives measured for LAS degradation in these studies were comparable to values reported in the literature and also to values obtained for naturally occurring materials (stearic acid, cellulose) typically present in soil environments. On the basis of the results of the present studies and those of other investigators, it is concluded that soil environments exposed to LAS in sewage sludges contain microbial communities which can actively metabolize this material. Rates of biodegradation of the benzene ring, the final step in the LAS biodegradation pathway prior to complete mineralization, are also sufficient to prevent LAS from accumulating in soil environments.

Two approaches to modeling kinetics of biodegradation by growing cells and application of a two-compartment model for mineralization kinetics in sewage

The patterns of microbial mineralization of 0.3 to 30 ng of glucose, benzoate, and phenol per ml of sewage collected in late fall and winter were analyzed with the integrated Monod equation and a model in which growth of active organisms occurs at the expense of organic compounds other than the test substrate. Either model could be closely fit by nonlinear regression to the data from individual tests with one concentration of substrate added to one dilution of sewage. However, neither model accounted satisfactorily for differences in patterns of mineralization resulting from differences in substrate concentration and cell density between different tests. It is suggested that both the added substrates and other organics present in sewage contributed to the growth of the active organisms. The mineralization of glucose in sewage collected in summer was better described by a two-compartment model than by any other model tested.

Adaptation of Aquatic Microbial Communities to Quaternary Ammonium Compounds

The effects of long-chain (C 12 to C 18 ) quaternary ammonium compounds (QACs) on the density, heterotrophic activity, and biodegradation capabilities of heterotrophic bacteria were examined in situ in a lake ecosystem. Monoalkyl and dialkyl substituted QACs were tested over a range of concentrations (0.001 to 10 mg/liter) in both acute (3 h) and chronic (21 day) exposures. In general, none of the QACs tested had significant adverse effects on bacterial densities in either acute or chronic studies. However, significant decreases in bacterial heterotrophic activity were noted in acute studies at QAC concentrations from 0.1 to 10 mg/liter. Chronic exposure of lake microbial communities to a specific monoalkyl QAC resulted in an adaptive response and recovery of heterotrophic activity. No-observable-effect level in the adapted populations was >10 mg/liter. Chronic exposure also resulted in significant increases in the number and activity of bacteria capable of biodegrading the material. The increase in biodegradation capability was observed at low (microgram per liter) concentrations which are approximately the same as realistic environmental levels. In general, our studies indicated that exposure of lake microbial communities to QACs results in the development of adapted communities which are less sensitive to potential toxic effects and more active in the biodegradation of these materials.

Kinetic Concepts for Measuring Microbial Rate Constants: Effects of Nutrients on Rate Constants

We investigated the effect of preincubation of environmental waters amended with inorganic nutrients (nitrogen, phosphorus, and traces of iron and magnesium) on the kinetics of the microbial transformation of phenol, propanil, propyl ester of (2,4-dichlorophenoxy)acetic acid, methyl parathion, Ronnel, and methoxychlor in pond and river waters. No effect on the second-order rate constants for these compounds was observed, although there was an increase in the bacterial populations and the pseudo-first-order rate constants. The use of nutrient-amended waters could be a useful tool for estimating second-order rate constants for an expanded number of compounds. This technique would provide a larger data base for predicting the behavior of xenobiotic compounds in the environment by using currently available mathematical models.