Toxicity of ionic and nonionic surfactants to six macrobes found in Agra, India

Influencing of hydrogeochemical conditions and engineering parameters on phase behaviors and remediation performance of in-situ microemulsion for residual PCE in aquifers

In-situ microemulsion has great potential for remediation of chlorinated solvent contaminated aquifers due to its efficient solubilization, and the in-situ formation and phase behaviors of microemulsion is a key factor in determining the remediation performance. However, the role of aquifer properties and engineering parameters on microemulsion in-situ formation and phase transition has been rarely attended. In this work, the influences of hydrogeochemical conditions on in-situ microemulsion phase transition and solubilization ability for tetrachloroethylene (PCE) were explored, and the formation condition, phase transition and removal efficiency for in-situ microemulsion flushing under various flushing conditions were investigated. The results indicated that the cations (Na⁺, K⁺, Ca²⁺) all facilitated the microemulsion phase altering from Winsor I → III → II, whereas the anions (Cl^-, SO₄^2-, CO₃^2-) and pH variation (5-9) had no profound influence on phase transition. Besides, the solubilization capacity of microemulsion was enhanced by the pH variation and the cations, which was proportional to the cation concentration of groundwater. The column experiments demonstrated that PCE underwent the phase transition from emulsion to microemulsion and then to micellar solution during the flushing process. The formation and phase transition of microemulsion were mainly related to injection velocity and PCE residual saturation in aquifers. The slower injection velocity and higher residual saturation were profitable to the in-situ formation of microemulsion. In addition, the removal efficiency could achieve 99.29 % for residual PCE at 12 °C, enhancing with the finer porous medium, lower injection velocity and intermittent injection. Furthermore, the flushing system exhibited high biodegradability and weak reagent adsorption onto the aquifer media, presenting a low environmental risk. This study provides valuable information on the in-situ microemulsion phase behaviors and the optimal reagent parameters, facilitating the application of in-situ microemulsion flushing.

Alcohol ethoxysulfates (AES) in environmental matrices

Extensive use of surfactants in numerous fields resulted in their discharge into various environmental compartments including soil, sediment, and water. Alcohol ethoxysulfates (AES) together with alcohol ethoxylates (AE), alkyl sulfates (AS), and linear alkyl benzene sulfonates (LAS) find wide variety of applications in consumer products including both domestic and industrial applications. Consequently, all these surfactants pose several concerns to both aquatic and human health. In the context of environmental impacts, AES has almost equal importance as that of LAS though the literature on this topic is only emerging. This review provides a detailed overview on the various aspects of the anionic surfactant, AES, such as toxicity of AES, its fate in the ecosystem, technical advancements in the area of identification and quantification, its occurrence and distribution in different environmental compartments spanning across the world, and finally a remark of its potential removal strategy from the environment.

Acute toxicity and sublethal effects of sodium laureth sulfate on oxidative stress enzymes in benthic oligochaete worm, Tubifex tubifex

The present study was performed to determine the acute toxicity of sodium laureth sulfate (SLES) and its sublethal effects on oxidative stress enzymes in benthic oligochaete worm Tubifex tubifex. The results showed that 96 h median lethal concentration (LC₅₀) value of SLES for Tubifex tubifex is 21.68 mg/l. Moreover exposed worms showed abnormal behaviours including incremented erratic movement, mucus secretion, and decreased clumping tendency at acute level. Percentage of autotomy additionally increased significantly (P < 0.05) with the increasing dose of toxicant at 96 h exposure. Sublethal concentrations of SLES (10% and 30% of 96 h LC₅₀ value) caused paramount alterations in the oxidative stress enzymes. Superoxide dismutase (SOD), reduced glutathione (GSH), glutathione S-transferase (GST), and glutathione peroxidase (GPx) exhibited a striking initiatory increment followed by a resulting descending pattern. Moreover, during exposure times, catalase (CAT) activity and malondialdehyde (MDA) level increased markedly with incrementing concentrations of SLES. However, the effects of sodium laureth sulfate on Tubifex tubifex were characterized and portrayed by the development of a correlation matrix and an integrated biomarker response (IBR) assessment. These results indicate that exposure to this anionic surfactant alters the survivability and behavioral response at acute level and modifies changes in oxidative stress enzymes at sublethal level in Tubifex tubifex.

Studying the toxicity of SLEnS-LAS micelles to collembolans and plants: Influence of ethylene oxide units in the head groups

Mixed micelles of linear alkylbenzene sulfonic acid (LAS) and ether sulfate-based surfactants (SLE_nS) can be added in household products and cleaning agents. SLE_nS with higher ethylene oxide (EO) units in the head groups have economic and environmental advantages. This work aims to assess the influence of the number of EO units in the ecotoxicity of seven variants of SLE_nS-LAS micelles (0-50 EO units) in soils. Ecotoxicological tests were carried out to assess emergence and growth of four plants species and reproduction of collembolans. Most of the variants inhibited plants growth at the highest concentrations (1237.5 μg SLE_nS kg^-1 of soil_dw). For reproduction, lower number of EO units resulted in EC₅₀ from 924.2 (95 % CL: 760.7-1063.4) to 963.2 (95 % CL: 676.9-1249.6) μg SLE_nS kg^-1 of soil_dw, whereas for higher number of EO units (50 and 30) no inhibition was reported. Based on these results, we suggest that a higher number of EO units contribute to less hazardous formulations, confirming that different designs of surfactants may contribute to changes in the responses of terrestrial organisms. Therefore, we demonstrate that standardized ecotoxicological assays may contribute to more sustainable and effective formulations, when used upstream, prior to manufacture and marketing.

Ecotoxicity and micellization behavior of anionic surfactant sodium dodecylbenzene sulfonate (SDBS) and its mixtures with nonionic surfactant fatty alcohol-polyoxyethylene ether (AEO)

Surfactant mixtures have extensive industrial applications due to their ideal properties and low ecotoxicity. However, the ecotoxicity of surfactant mixtures with different proportions and their correlation with surface properties have remained poorly investigated. In this study, the ecotoxicity and surface activity of the composites of anionic surfactant sodium dodecylbenzene sulfonate (SDBS) and nonionic surfactant fatty alcohol-polyoxyethylene ether (AEO) in various mass ratios were assessed, and the correlation between ideal application properties and safe ecological perspective of the composites was explored. The ecotoxicity of individual SDBS, AEO, and SDBS/AEO mixtures was determined using the bioluminescence inhibition assay with Photobacterium phosphoreum, and the critical micelle concentrations (CMC) were measured by surface tension method and steady-state fluorescence spectroscopy. Sodium dodecylbenzene sulfonate (SDBS) showed a considerably higher toxicity than individual AEO and SDBS/AEO mixtures. Scanning electron microscope images illustrated the rupture of bacteria membrane induced by SDBS, and the addition of AEO alleviated the damage. According to the dose-response relationship on luminous bacteria, SDBS/AEO mixtures were divided into three groups (group I with a high proportion of SDBS, SDBS:AEO = 4:1 and 3:2; group II, SDBS:AEO = 1:1; group III with a high proportion of AEO, SDBS:AEO = 2:3 and 1:4). The sequence of toxicity of the SDBS/AEO mixtures was group II > group III > group I, demonstrating that the toxicity of the composites was related to the mixture proportion instead of the amount of AEO added. The CMC order of SDBS/AEO mixtures was group II > group I > group III, and it was proportion dependent. Furthermore, ΔC^M was defined as the difference of the experimental (C^M) and ideal CMC (C^Mi_deal) of the mixed system, indicating the interaction between the two kinds of surfactants. The order of the ΔC^M was group II > group III > group I, which was consistent with the sequence of the toxicity. Therefore, ΔC^M can be a potential indicator for the hazardous assessment of surfactant mixtures involving high ionic strength.

A review on the application of chemical surfactant and surfactant foam for remediation of petroleum oil contaminated soil

Soil, exposed to petroleum oil contaminants (in the form of petrol, diesel, gasoline, crude oil, used motor oil), may cause potential damage to the environment, animal and human health. In this review article, mechanisms of the petroleum oil contaminant removal from soil by chemical surfactant systems such as surfactant solution, surfactant foam and nanoparticle stabilized surfactant foams are explained. Laboratory based research works, reported within the last decade on the application of similar systems towards the removal of petroleum oil contaminant from the soil, have been discussed. It is an important fact that the commercial implementation of the chemical surfactant based technology depends on the environmental properties (biodegradability and toxicity) of the surfactants. In recent times, surfactant foam and nanoparticle stabilized surfactant foam are becoming more popular and considered advantageous over the use of surfactant solution alone. However, more research works have to be conducted on nanoparticle stabilized foam. The impact of physicochemical properties of the nanoparticles on soil remediation has to be explored in depth.

Authorization and Toxicity of Veterinary Drugs and Plant Protection Products: Residues of the Active Ingredients in Food and Feed and Toxicity Problems Related to Adjuvants

Chemical substances applied in animal husbandry or veterinary medicine and in crop protection represent substantial environmental loads, and their residues occur in food and feed products. Product approval is governed differently in these two sectors in the European Union (EU), and the occurrence of veterinary drug (VD) and pesticide residues indicated by contamination notification cases in the Rapid Alert System for Food and Feed of the EU also show characteristic differences. While the initial high numbers of VD residues reported in 2002 were successfully suppressed to less than 100 cases annually by 2006 and on, the number of notification cases for pesticide residues showed a gradual increase from a low (approximately 50 cases annually) initial level until 2005 to more than 250 cases annually after 2009, with a halt occurring only in 2016. Main notifiers of VD residues include Germany, Belgium, the UK, and Italy (63, 59, 42, and 31 notifications announced, respectively), and main consigning countries of non-compliances are Vietnam, India, China, and Brazil (88, 50, 34, and 23 notifications, respectively). Thus, countries of South and Southeast Asia are considered a vulnerable point with regard to VD residues entering the EU market. Unintended side effects of VDs and plant protection products may be caused not only by the active ingredients but also by various additives in these preparations. Adjuvants (e.g., surfactants) and other co-formulants used in therapeutic agents and feed additives, as well as in pesticide formulations have long been considered as inactive ingredients in the aspects of the required main biological effect of the pharmaceutical or pesticide, and in turn, legal regulations of the approval and marketing of these additives specified significantly less stringent risk assessment requirements, than those specified for the active ingredients. However, numerous studies have shown additive, synergistic, or antagonistic side effects between the active ingredients and their additives in formulated products; moreover, toxicity has been evidenced for various additives. Therefore, toxicological evaluation of surfactants and other additives is essential for proper environmental risk assessment of formulations used in agriculture including animal husbandry and plant protection.

Characteristics and environmental fate of the anionic surfactant sodium lauryl ether sulphate (SLES) used as the main component in foaming agents for mechanized tunnelling

The anionic surfactant sodium lauryl ether sulphate (SLES) is the main component of most commercial products used for soil conditioning in the excavation industry, in particular as lubricants for mechanized tunnelling. Its use during the excavation processes can result in either the subsequent possible re-use of the huge amount of soil debris as by-products (e.g. land covering) or its discharge as waste. Currently, there are neither SLES soil threshold limits in European legislation, nor comprehensive studies on the environmental risk for soil ecosystems in these exposure scenarios. In this context, the present paper reviews the available data on the intrinsic characteristics of persistence and the ecotoxicological effects of the anionic surfactant SLES. Although SLES is generally reported to be biodegradable in standard tests, with degradation rates between 7 h and 30 days, depending on the initial conditions, data on its biodegradation in environmental studies are quite scarce. Consequently, assessing SLES biodegradation rates in field conditions is crucial for evaluating if in residual concentrations (typically in the range 40-500 mg/kg in excavated soils) it can or not be a potential hazard for terrestrial and water organisms. Laboratory ecotoxicological tests pointed out detrimental effects of SLES for aquatic organisms, while data on the terrestrial species are rather poor so far and further studies at the expected environmental concentrations are necessary. Finally, the review reports the main analytical methods available for detecting anionic surfactants in solid matrices and the future research needed to improve knowledge on the possible environmental risks posed by the use of SLES in foaming agents for mechanized tunnelling.

Exploring the Effects of Different Types of Surfactants on Zebrafish Embryos and Larvae

Currently, surfactants are widely distributed in the environment. As organic pollutants, their toxicities have drawn extensive attention. In this study, the effects of anionic [sodium dodecyl sulphate (SDS) ], cationic [dodecyl dimethyl benzyl ammonium chloride (1227)] and non-ionic [fatty alcohol polyoxyethylene ether (AEO) ] surfactants on zebrafish larval behaviour were evaluated. Five behavioural parameters were recorded using a larval rest/wake assay, including rest total, number of rest bouts, rest bouts length, total activity and waking activity. The results revealed that 1227 and AEO at 1 μg/mL were toxic to larval locomotor activity and that SDS had no significant effects. Moreover, we tested the toxicities of the three surfactants in developing zebrafish embryos. AEO exposure resulted in smaller head size, smaller eye size and shorter body length relative to SDS and 1227. All three surfactants incurred concentration-dependent responses. Furthermore, in situ hybridisation indicated that smaller head size may be associated with a decreased expression of krox20. The altered expression of ntl demonstrated that the developmental retardation stemmed from inhibited cell migration and growth. These findings provide references for ecotoxicological assessments of different types of surfactants, and play a warning role in the application of surfactants.

Surfactant induced complex formation and their effects on the interfacial properties of seawater

The effect of a cationic surfactant, hexadecyltrimethylammonium bromide (CTAB), on the interfacial properties of seawater has been studied by dynamic and equilibrium surface tension and by dilational rheology essays. Important modifications of the surface tension and dilational rheology response have been observed already at the very low CTAB concentrations, where the effects due to the high ionic strength are negligible. The comparison with the effects of CTAB in different seawater models, or in natural seawater fractions, points out the establishment of strong interactions between the surfactant molecules and the lipophilic fraction of organic material dispersed/dissolved in seawater, affecting the interfacial activity of the molecules. Considering the biochemical richness of seawater, these results can be explained assuming interaction mechanisms and adsorption schemes similar to those speculated for protein and other macromolecules in the presence of surfactants, which in fact show similar features. Thus already at the low concentrations the surfactant molecules form highly surface-active complexes with part of the organic fraction of seawater. At the larger surfactant concentrations these complexes compete for adsorption with an excess of free CTAB molecules which, according to the thermodynamic conditions, are most favoured to occupy the liquid interface. The results of this study underline the important role of the sea organic content in enhancing the surface-activity of surfactants, which is relevant for a deeper understand of the direct and indirect effects of these types of pollutants on the physico-chemical environment in the sea coastal areas and develop mitigation strategies.

Nanostructured liquid crystalline particles as an alternative delivery vehicle for plant agrochemicals

Agrochemical spray formulations applied to plants are often mixed with surfactants that facilitate delivery of the active ingredient. However, surfactants cause phytotoxicity and off-target effects in the environment. We propose the use of nanostructured liquid crystalline particles (NLCP) as an alternative to surfactant-based agrochemical delivery. For this, we have compared the application of commercial surfactants, di (2-ethylhexyl) sulfosuccinate and alkyl dimethyl betaine, with NLCP made from phytantriol, at concentrations of 0.1%, 1% and 5% on the adaxial surface of leaves of four plant species Ttriticum aestivum (wheat), Zea mays (maize), Lupinus angustifolius (lupin), and Arabidopsis thaliana. In comparison with the application of surfactants there was less phytotoxicity on leaves of each species following treatment with NLCP. Following treatment of leaves with NLCP analysis of cuticular wax micromorphology revealed less wax solubilization in the monocot species. The results clearly show that there are advantages in the use of NLCP rather than surfactants for agrochemical delivery.

Perspective on the use of humic acids from biomass as natural surfactants for industrial applications

In the context of renewable vs. non-renewable sources of chemical compounds, the development of natural surfactants as a substitute for synthetic surfactants in technological applications is an important issue. In addition, as synthetic surfactants can persist in the environment causing toxic effects, the use of natural products presents a possibility to minimize impact on the environment. Nowadays, a promising new approach in surfactant-based technologies, consists of the use of humic acids (HAs) extracted directly from biomass that exhibit amphiphilic properties, and can be conveniently used as environmentally friendly surfactants. The raw material from which HAs are extracted and their macromolecular composition affect surfactant properties. Therefore fundamental data from more strictly qualitative aspects, needs to be investigated. This review highlights surfactant ability and chemical properties of HA substances coming from renewable sources in comparison to synthetic surfactants, and points out the capacity for HAs to be used effectively in this field of application.

A feed-forward artificial neural network for prediction of the aquatic ecotoxicity of alcohol ethoxylate

A feed-forward artificial neural network (ANN) has been developed for predicting the aquatic ecotoxicity of alcohol ethoxylate (AE), a non-ionic surfactant comprising a variety of homologues. Trained with previously reported ecotoxicity data, the ANN utilizes both molecular characteristics (alkyl chain length, branching extent in alkyl chain, and ethoxylate (EO) number) and exposure features (effect endpoint, test duration, test type, and species taxon) as inputs to predict the ecotoxicity. The ANN predicted an increase in ecotoxicity for homologues with a longer or less-branched alkyl chain, or those with fewer EO units. But for long alkyl chain (>14) homologues, the ecotoxicity increase was predicted by the ANN to level off, which is obscured by existing quantitative structure-activity relationships (QSARs). A "leave-one-out" cross-validation process indicated that the prediction accuracy was within a factor of 5 with 90% probability. This research demonstrated that the current ANN covers a wider application domain with respect to the homologue range and a variety of exposure features without compromising on predictive accuracy.

Ecotoxicity and biodegradability of an alkyl ethoxysulphate surfactant in coastal waters

Alkyl ethoxysulphates (AES) are anionic surfactants widely used in numerous commercial and industrial applications. In spite of the high AES volume consumption a few data concerning the occurrence, fate and effects of AES in marine environments are reported in literature. The objective of this study is to evaluate the biodegradability and toxicity of AES in pristine sea water. Ultimate biodegradation was studied according to the guideline 835.3160 "Biodegradability in sea water" proposed by the United States Environmental Protection Agency (USEPA). Acute toxicity of AES was studied to the microalgae Nannochloropsis gaditana, Isochrysis galbana, Chaetoceros gracilis, Dunaliella salina and Tetraselmis chuii and the invertebrate Artemia franciscana, using culture growth inhibition and death, respectively, as effect criteria. During the degradative process two different stages were observed, which were better described with the first order and logistic kinetic models, respectively. Lag times were 3.3 (stage A) and 26.5 (stage B) days whereas half-lives were 18.6 (stage A) and 49.8 (stage B) days. AES inhibited the microalgae growth, with 96-h EC50 values ranging from 4.68 g L(-1) for D. salina to 24.02 mg L(-1) for I. galbana. Mean 48- and 72-h LC50 values for A. franciscana were 38.30 and 23.92 mg L(-1), respectively. The results indicate an extensive biodegradability of AES in sea water, although at a very slow rate. Acute toxicity was highly dependent on the species tested, being the green alga D. salina the most affected organism. The present study provides relevant data concerning the biodegradability and adverse effects of an AES surfactant on marine organisms, which are useful to establish water quality criteria in a regulatory framework.

Inhibition of growth and photosynthesis of selected green microalgae as tools to evaluate toxicity of dodecylethyldimethyl-ammonium bromide

The effect of dodecylethyldimethyl-ammonium bromide (DEAB), a quaternary ammonium, compound widely used as disinfectant, on phytoplankton of inland water systems was analysed by using an experimental model. A toxicity test was based on inhibition of photosynthesis performances (effective quantum yield from photosystem II, Phi(PSII) and O(2) production) of the phytoplanktonic species Scenedesmus intermedius and Dictiosphaerium chlorelloides (Chlorophyceae) under growing doses of DEAB. A concentration-dependent toxic response was obtained in both parameters analysed. In addition, this response was almost immediate. Consequently, the measurement of both parameters (Phi(PSII )and O(2) production) allows to assess DEAB toxicity with higher standards of precision and repeatability. We propose that this procedure could be used to detect presence of quaternary ammonium pollutants in freshwater.

Effects of nonionic and ionic surfactants on survival, oxidative stress, and cholinesterase activity of planarian

Eight widely used surfactants (cetyltrimethylammonium bromide; CTAB, benzethonium chloride; Hyamine 1622, 4-nonylphenol; NP, octylphenol ethoxylate; Triton X-100, dodecylbenzene sulfonate; LAS, lauryl sulfate; SDS, pentadecafluorooctanoic acid; PFOA, and perfluorooctane sulfonate; PFOS) were selected to examine their acute toxicities and effects on oxidative stress and cholinesterase (ChE) activities in Dugesia japonica. The differences in acute toxicity among eight surfactants to planarians were at least in the range of three orders of magnitudes. The toxicity rank of surfactants according to estimated 48-h LC(50) was SDS>NP>LAS>Hyamine 1622>CTAB>Triton X-100>PFOS>PFOA. The toxicity rank of surfactants according to 96-h LC(50) was as follows: SDS>CTAB>NP>LAS>Hyamine 1622>Triton X-100>PFOS>PFOA. There were significant increases in catalase activities in planarians exposed to LAS at nominal concentrations of 0.5 or 1 mgl(-1) and to PFOS at nominal concentrations of 5 or 10 mgl(-1) after 48-h exposure. Inhibitions of ChE activities were found in planarians exposed to Hyamine 1622 at all concentrations tested, to PFOS at nominal concentration of 10 mgl(-1), to PFOA at nominal concentrations of 50 or 100 mgl(-1) and to NP at nominal concentration of 0.5 mgl(-1). A significant increase in ChE activities was also observed in planarian exposed to Triton X-100 at nominal concentration of 5 mgl(-1). The implication of ChE inhibition by NP, PFOS and PFOA on neurological and behavioral effects in aquatic animals requires further investigation.

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.

Ability of biosolids and a cationic surfactant to modify methidathion leaching. Modelling with pescol

Packed columns were prepared with an agricultural soil to examine the ability of two organic soil modifiers, biosolid and the cationic surfactant tetradecyl trimethyl ammonium bromide (TDTMA), to alter the leaching of the insecticide methidathion. Ion chloride was used as a tracer of water flow and the mathematical model PESCOL was selected to predict the mobility of the insecticide. The biosolid addition (SB column) delayed the breakthrough curves for methidathion with respect to the non-amended soil (S) column. The cationic surfactant TDTMA, alone or combined with the biosolid (SS and SBS) and previously incorporated in the soil column, caused the highest retardation of this pesticide in the soil columns. Theoretical retardation factors (TRf) were similar to the experimental Rf values for the S and SB columns, and predicted the high retention observed in the SBS and SS columns. The simulation with PESCOL predicted the experimental results.