Anionic surfactant linear alkylbenzene sulfonates (LAS) in sediments from the Gulf of Gdańsk (southern Baltic Sea, Poland) and its environmental implications

A comparative study of surfactant distribution and fate (western and eastern) Egyptian Mediterranean coasts focusing on its environmental toxicity

One of the most difficult-to-manage new contaminants constantly released into the environment is linear alkylbenzene sulphonate (LAS), an anionic surfactant. Significant volumes of LAS are received by the Mediterranean coast of Egypt. The current study is a comprehensive assessment of the environmental fate of the LAS 1505 km off the Mediterranean coast of Egypt in the fall of 2023 in order to track its geographic spread and eventual demise in the water column. Critical analysis of LAS revealed that it is vertically distributed in various ways according to sources, uses, production amounts, and salinity levels. The vertical variation of LAS can be explained by its amphiphilic structure. A significant increase in surfactant concentration (>300 μg/L) was recorded in 66% and 43% of the total samples, ranging from 301.128 to 455.36 and from 304.556 to 486.135 for the western and eastern sides along the Egyptian Mediterranean coast, respectively. Evaluation of the average acute and chronic risk quotient (RQ) along the investigated locations revealed that fish were the most susceptible to LAS in both long and short exposure periods. The presented results also indicated significant LAS toxicity to three trophic levels (RQ values > 1). LAS toxicity to marine organisms was greater in the western than in eastern coastal regions according to acute and chronic mixture risk characterization ratios (RCRmix). The three trophic levels in the study area had the following order of acute relative contribution (RC) to LAS toxicity: fish > invertebrates > algae. The ANOVA test results showed that in both the western and eastern regions, LAS varied significantly (p < 0.05) with salinity (1.04E-60 and 5.44E-42) and depth (6.02E-65 and 1.59E-47), respectively. In addition, a significant difference was observed using the ANOVA test between the eastern and western regions of the Egyptian Mediterranean coast.

Effects of surfactants on the adsorption of norfloxacin onto ferrihydrite: comparison between anionic and cationic surfactants

There is little information on how widespread surfactants affect the adsorption of norfloxacin (NOR) onto iron oxide minerals. In order to elucidate the effects of various surfactants on the adsorption characteristics of NOR onto typical iron oxides, we have explored the different influences of sodium dodecylbenzene sulfonate (SDBS), an anionic surfactant, and didodecyldimethylammonium bromide (DDAB), a cationic surfactant, on the interactions between NOR and ferrihydrite under different solution chemistry conditions. Interestingly, SDBS facilitated NOR adsorption, whereas DDAB inhibited NOR adsorption. The adsorption-enhancement effect of SDBS was ascribed to the enhanced electrostatic attraction, the interactions between the adsorbed SDBS on ferrihydrite surfaces and NOR molecules, and the bridging effect of SDBS between NOR and iron oxide. In comparison, the adsorption-inhibition effect of DDAB owning to the adsorption site competitive adsorption between NOR and DDAB for the effective sites as well as the steric hindrance between NOR-DDAB complexes and the adsorbed DDAB on ferrihydrite surfaces. Additionally, the magnitude of the effects of surfactants on NOR adsorption declined with increasing pH values from 5.0 to 9.0, which was related to the amounts of surfactant binding to ferrihydrite surfaces. Moreover, when the background electrolyte was Ca2+, the enhanced effect of SDBS on NOR adsorption was caused by the formation of NOR-Ca2+-SDBS complexes. The inhibitory effect of DDAB was due to the DDAB coating on ferrihydrite, which undermined the cation-bridging effect. Together, the findings from this work emphasize the essential roles of widely existing surfactants in controlling the environmental fate of quinolone antibiotics.

Growth and physiological responses of submerged macrophytes to linear alkylbenzene sulfonate (LAS)

The potential toxic effects of linear alkylbenzene sulfonate (LAS), widely used in commercial detergents and cleaners, on submerged macrophytes remain unclear. We conducted a two-week exposure experiment to investigate LAS toxicity on five submerged macrophytes (four native and one exotic), focusing on their growth and physiological responses. The results showed that lower concentrations of LAS (< 5 mg/L) slightly stimulated the growth of submerged macrophytes, while higher doses inhibited it. Increasing LAS concentration resulted in decreased chlorophyll content, increased MDA content and POD activity, and initially increased SOD and CAT activities before declining. Moreover, Elodea nuttallii required a higher effective concentration for growth compared to native macrophytes. These findings suggest that different species of submerged macrophytes exhibited specific responses to LAS, with high doses (exceeding 5 ∼ 10 mg/L) inhibited plant growth and physiology. However, LAS may promote the dominance of surfactant-tolerant exotic submerged macrophytes in polluted aquatic environments.

Emerging pollutants in textile wastewater: an ecotoxicological assessment focusing on surfactants

Water and several chemicals, including dyestuffs, surfactants, acids, and salts, are required during textile dyeing processes. Surfactants are harmful to the aquatic environment and induce several negative biological effects in exposed biota. In this context, the present study aimed to assess acute effects of five surfactants, comprising anionic and nonionic classes, and other auxiliary products used in fiber dyeing processes to aquatic organisms Vibrio fischeri (bacteria) and Daphnia similis (cladocerans). The toxicities of binary surfactant mixtures containing the anionic surfactant dodecylbenzene sulfonate + nonionic fatty alcohol ethoxylate and dodecylbenzene sulfonate + nonionic alkylene oxide were also evaluated. Nonionic surfactants were more toxic than anionic compounds for both organisms. Acute nonionic toxicity ranged from 1.3 mg/L (fatty alcohol ethoxylate surfactant) to 2.6 mg/L (ethoxylate surfactant) for V. fischeri and from 1.9 mg/L (alkylene oxide surfactant) to 12.5 mg/L (alkyl aryl ethoxylated and aromatic sulfonate surfactant) for D. similis, while the anionic dodecylbenzene sulfonate EC50s were determined as 66.2 mg/L and 19.7 mg/L, respectively. Both mixtures were very toxic for the exposed organisms: the EC50 average in the anionic + fatty alcohol ethoxylate mixture was of 1.0 mg/L ± 0.11 for V. fischeri and 4.09 mg/L ± 0.69 for D. similis. While the anionic + alkylene oxide mixture, EC50 of 3.34 mg/L for D. similis and 3.60 mg/L for V. fischeri. These toxicity data suggested that the concentration addition was the best model to explain the action that is more likely to occur for mixture for the dodecylbenzene sulfonate and alkylene oxide mixtures in both organisms. Our findings also suggest that textile wastewater surfactants may interact and produce different responses in aquatic organisms, such as synergism and antagonism. Ecotoxicological assays provide relevant information concerning hazardous pollutants, which may then be adequately treated and suitably managed to reduce toxic loads, associated to suitable management plans.

Surfactants in water and wastewater (greywater): Environmental toxicity and treatment options

Surfactant, an emerging pollutant present in greywater, raises the toxicity levels in the water body. Soap, detergent, and personal care items add surfactant to greywater. Due to excessive washing and cleaning procedures brought on by the COVID-19 pandemic, the release of surfactants in greywater has also increased. Considering the environmental toxicity and problems it creates during the treatment, it's essential to remove surfactants from the wastewater. This review intends to explain and address the environmental toxicity of the surfactant released via greywater and current techniques for surfactant removal from wastewater. Various physical, chemical, and biological methods are reported. Modern adsorbents such as hydrophilic silica nanoparticles, chitosan, fly ash, and iron oxide remove surfactants by adsorption. Membrane filtration effectively removes surfactants but is not cost-effective. Coagulants (chemical and natural coagulants) neutralize surfactant charges and help remove them as bigger particles. Electrocoagulation/electroflotation causes surfactants to coagulate and float. Microorganisms break down surfactants in microbial fuel cells to generate power. Surfactants are removed by natural processes and plants in constructed wetlands where traditional aerobic and anaerobic approaches use microbes to break down surfactants. Constructed wetlands, natural coagulation-flocculation, and microbial fuel cells are environmentally beneficial methods to remove surfactants from wastewater.

Adsorption of fluoroquinolone antibiotics onto ferrihydrite under different anionic surfactants and solution pH

To date, little information is available regarding the impacts of the widespread anionic surfactants on the adsorption behaviors of antibiotics onto typical iron oxides. Herein, we have investigated the effects of two typical surfactants (sodium dodecyl sulfate (SDS) and sodium dodecylbenzene sulfonate (SDBS)) on the adsorption of two widely used antibiotics (i.e., levofloxacin (LEV) and ciprofloxacin (CIP)) onto ferrihydrite. Results of kinetic experiments showed that the adsorption of antibiotics was well fitted by the pseudo-second-order kinetic models, indicating that the adsorption process might be controlled by chemisorption. The affinity of ferrihydrite toward CIP was greater than that toward LEV, which was ascribed to the higher hydrophobicity of CIP than LEV. Both surfactants enhanced antibiotic adsorption owing to SDS or SDBS molecules as bridge agents between ferrihydrite particles and antibiotics. Interestingly, the extent of the enhanced effects of surfactants on antibiotic adsorption declined as the background solution pH increased from 5.0 to 9.0, which was mainly due to the weaker hydrophobic interactions between antibiotics and the adsorbed surfactants on the iron oxide surfaces as well as the greater electrostatic repulsion between the anionic species of antibiotics and the negatively charged ferrihydrite particles at higher pH. Together, these findings emphasize the importance of widespread surfactants for illustrating the interactions between fluoroquinolone antibiotics and iron oxide minerals in the natural environment.

Rhodamine 6G-Anionic Surfactant System Modified by Triton X-100 for Fluorescence Determination of Albumin

The influence of sodium hexadecyl sulfate on the nature of the fluorescence spectra of rhodamine 6G in an aqueous solution and a solution of nonionic Triton X-100 was investigated. The change in the nature of the emission spectra is explained by the formation of hydrophobic stoichiometric and sub-stoichiometric reagent-surfactant associates. Stabilization of the colloid-chemical state and reduction of the total turbidity of rhodamine 6G-anionic surfactant associate solutions with the addition of nonionic surfactant as a modifier were registered. The method of modification of the rhodamine 6G-sodium hexadecyl sulfate system with a nonionic surfactant was used in the development of conditions for the fluorescence determination of protein substances in physiological solutions. The concentration conditions for the use of the modified reagent system rhodamine 6G-anionic surfactant-nonionic surfactant for the fluorescence determination of albumin in urine were optimized.

Accelerated transformation of sodium dodecylbenzene sulfonate surfactant in the UV/chlorine process: Kinetics and formation of chlorinated disinfection by-products

The degradation kinetics of Sodium dodecylbenzene sulfonate (SDBS) surfactant in the UV/chlorine process was comprehensively investigated, and the formation of chlorinated disinfection by-products (Cl-DBPs) were determined. Results showed that the degradation of SDBS by UV, chlorine and UV/chlorine all followed pseudo-first-order kinetics. The rate constant by UV/chlorine in ultrapure water was approximately 3 times higher than the sum of those by UV and chlorine, and decreased from 0.297 to 0.063 min^-1 with pH increasing from 5.0 to 9.0. Water matrices such as NO₃^-, HCO₃^- and natural organic matter (NOM) inhibited the degradation efficiency to a certain extent. The second-order rate constant of SDBS with HO^• was determined as 2.84 × 10⁹ M^-1 s^-1. Through using different probes, the main contributors to SDBS degradation were found to be UV, HO^• and reactive chlorine species (RCS). Meanwhile, 64.0 μg L^-1 trichloromethane (TCM) and 8.7 μg L^-1 chloral hydrate (CH) were simultaneously formed within 30 min of UV/chlorine treatment. The concentration of total organic chlorine (TOCl) (424.0 μg L^-1) was obviously higher than those of TCM and CH. In addition, 414 unknown by-products formed during UV/chlorine treatment were detected by mass spectrometry at a high confidence level, including 64 monochloro-DBPs and 2 dichloro-DBPs. Although UV/chlorine process accelerated SDBS degradation, the associated DBP formation deserves enough attention.

Ultra-high-performance supercritical fluid chromatography-mass spectrometry for the analysis of organic contaminants in sediments

A nontarget screening method was developed based on D-optimal designs for ultra-high performance supercritical fluid chromatography with positive and negative electrospray ionization mode mass spectrometry. A mixture of organic contaminants such as pesticides, steroids, surfactants, phenolic and fatty acids, and polycyclic aromatic hydrocarbon derivatives, was used for the optimization. An aprotic mixture of dichloromethane and acetone [3:1] performed overall best as the injection solvent. The highest peak capacities (n) were accomplished at the shallowest gradient (1%B/min), ammonium formate (n = 378 in negative ionization mode), or ammonium acetate (n = 327 in positive ionization mode) in methanol as the modifier. Capillary voltage, make-up solvent flow rate, water, and additive concentration were the most significant factors for improving peak intensity: higher peak intensities were obtained at lower additive concentrations (5mM ammonium formate), and with 5% water in positive ionization mode. Conversely, water had detrimental effects in negative ionization mode. The optimized method was used to quantify organic contaminants in 17 freshwater sediment samples from Copenhagen, Denmark. Out of 50 monitored contaminants, 35 were detected in at least one sample. Further, the method has a potential for target and nontarget screening analysis of organic contaminants in solid matrices.

Environmental risks and toxicity of surfactants: overview of analysis, assessment, and remediation techniques

This work comprehensively reviewed the toxicity and risks of various surfactants and their degraded products in the environmental matrices, various analytical procedures, and remediation methods for these surfactants. The findings revealed that the elevated concentration of surfactants and their degraded products disrupt microbial dynamics and their important biogeochemical processes, hinder plant-surviving processes and their ecological niche, and retard the human organic and systemic functionalities. The enormous adverse effects of surfactants on health and the environment necessitate the need to develop, select, and advance the various analytical and assessment techniques to achieve effective identification and quantification of several surfactants in different environmental matrices. Considering the presence of surfactants in trace concentration and environmental matrices, excellent analysis can only be achieved with appropriate extraction, purification, and preconcentration. Despite these pre-treatment procedures, the chromatographic technique is the preferred analytical technique considering its advancement and shortcomings of other techniques. In the literature, the choice or selection of remediation techniques for surfactants depends largely on eco-friendliness, cost-implications, energy requirements, regeneration potential, and generated sludge composition and volume. Hence, the applications of foam fractionation, electrochemical advanced oxidation processes, thermophilic aerobic membranes reactors, and advanced adsorbents are impressive in the clean-up of the surfactants in the environment. This article presents a compendium of knowledge on environmental toxicity and risks, analytical techniques, and remediation methods of surfactants as a guide for policymakers and researchers.

Assessing the distributions and fate of household and personal care chemicals (HPCCs) in the Songhua Catchment, Northeast China

Many household and personal care chemicals (HPCCs) are of environmental concern due to their potential toxicity to humans and wildlife. However, few studies investigate the spatiotemporal variations and fate of HPCCs in large-scale river systems. Here, river water and sediment samples from the Songhua River in Northeast China were analyzed for seven classes of HPCCs. Correlation analysis suggested similar sources and environmental behavior for compounds from the same HPCC classes. In the river water, the concentrations of most HPCCs in the cold season were significantly higher than that of the warm season (p < 0.01). Significantly higher levels of target compounds were found in the downstream water samples of a city, suggesting the influence of human activities on the distributions of HPCCs. The concentrations and distributions of most HPCCs were controlled by primary emission sources. The derived dissolved concentrations of HPCCs suggested that small amounts of caffeine and parabens were partitioned onto particles, while large amounts of many other HPCCs were bound to the particle phase. Water-sediment distribution coefficients (log K_d) ranged from 1.59 for caffeine to 3.95 for benzalkonium chloride-C14. This work presents new insights into the environmental behavior of HPCCs and the factors affecting their fate in river systems.

Antagonism or synergism? Responses of Hydrocharis dubia (Bl.) Backer to linear alkylbenzene sulfonate, naphthalene and their joint exposure

The presence of surfactants may affect the bioavailability of polycyclic aromatic hydrocarbons. A hydroponic experiment was conducted to investigate the response of Hydrocharis dubia (Bl.) Backer to different concentrations of linear alkylbenzene sulfonate (LAS), naphthalene (NAP) and their mixture (0.5, 5, 10, and 20 mg/L) for 14 days and 28 days. The results showed that LAS had a greater toxic effect on H. dubia growth than NAP at treatment concentrations of 0.5-20 mg/L. The combined effect of LAS and NAP was damaging to H. dubia at concentrations of LAS + NAP ≥5 + 5 mg/L. When LAS + NAP ≥10 + 10 mg/L, the underground parts of H. dubia suffered more significant damage than the aboveground parts. Under the treatments with LAS, NAP and their mixture, H. dubia experienced oxidative stress. Soluble proteins and antioxidant enzymes were the main substances protecting H. dubia from LAS stress, and superoxide dismutase (SOD) and peroxidase (POD) were the main protective enzymes. When exposed to NAP, H. dubia growth was stimulated and promoted at the same time. In the short-term treatment (14 d), catalase (CAT) activity was sensitive to NAP stimulation, and soluble proteins and SOD were the main protective substances produced. Soluble sugars, SOD and ascorbate peroxidase (APX) played important protective roles during the longer exposure time (28 d). The physiological response of H. dubia exposed to the combined toxicants was weaker than the response to exposure to individual toxicants. The responses of SOD and CAT activity were positive in the short term (14 d), and these were the main protective enzymes. As the exposure time increased (28 d), the plant antioxidant system responded negatively.

Laundry wastewater and domestic sewage pilot-scale anaerobic treatment: Microbial community resilience regarding sulfide production

In this study, the removal of anionic surfactant Linear Alkylbenzene Sulfonate (LAS) from laundry wastewater was evaluated in co-digestion with domestic sewage, using a pilot-scale Expanded Granular Sludge Bed reactor. Surfactant influent concentration was enhanced from 5 ± 3 mg LAS L^-1 (stage I) to 19 ± 10 mg LAS L^-1 (stage II) and 36 ± 19 mg LAS L^-1 (stage III) throughout reactor operation. Sulfide levels higher than 20 mg L^-1 influenced LAS removal efficiency, which decreased from 71% to 55% and 32% in stage I, II and III, respectively. Acclimation of microbial population was verified and higher relative abundance of the genera similar to Cytophaga, Bacteroides, Syntrophus and Syntrophobacter in the early stages (adaptation and stage I) was replaced by higher relative abundance of the genera Anaerophaga, Nitrosovibrio, Sulfurovum and Desulfovibrio in the last stages (stage II and III).

Potentiometric Sensors for the Determination of Anionic Surfactants - A Review

Anionic surfactants are important components of many products used in everyday life in all households. They are also applied in various industrial fields at a very large scale. Since they have a negative influence on the environment, it is an imperative to monitor their concentration in aquatic ecosystems. Therefore, it is of great importance to develop new methods for the determination of a wide spectra of anionic surfactants in complex environmental samples in a short time. A comprehensive review of potentiometric sensors for the determination of anionic surfactants in the last 50 years is given with special concern to papers published since 2000, but noting some earlier published important papers. The latest development in use of new ionophores, polymer formulations, and nanomaterials is presented. Additionally, the application of new potentiometric sensors in batch mode or in miniaturized microfluidic methods is discussed.

Degradation of SDBS in water solutions using plasma in gas-liquid interface discharge: Performance, byproduct formation and toxicity evaluation

Sodium Dodecyl Benzene Sulfonate (SDBS) is a major anionic surfactant and is widely used in the detergent industry. The large amount of SDBS discharged into water bodies can cause eutrophication of water bodies and produce toxic effects in aquatic organisms. In this study, the degradation of SDBS and variation in toxicity during the plasma treatment process were evaluated using gas-liquid interface discharge. The experimental results showed that SDBS could be removed effectively after discharge for 8 min at an initial concentration of 30 mg/L. The SDBS removal could be fitted by the first-order kinetic model. The plasma voltage and initial pH had great effects on the removal of SDBS. At the same voltage, SDBS could be removed faster under alkaline conditions. Compared to ozonation, much higher SDBS and TOC removal performance was achieved by plasma treatment. HO, which was mainly derived from the reaction of H₂O₂ and ozone in the solutions, played a major role in the oxidation process. The toxicity evaluation showed that plasma treatment could reduce the acute toxicity effectively initially, and also indicated that the formed intermediates of formate, oxalate, malonate and sulfate had no negative effects. However, further treatment caused an increase in toxicity, which was mainly correlated with the excessive residual H₂O₂ formed during the plasma process. This study indicated that while applying plasma treatment, the conditions should be optimized comprehensively to maintain a low H₂O₂ residual in the effluent.

Growth and Physiological Responses in Myriophyllum spicatum L. Exposed to Linear Alkylbenzene Sulfonate

The exogenous organic pollutant linear alkylbenzene sulfonate (LAS) is frequently detected in water. Myriophyllum spicatum L., a submerged aquatic plant, is a popular choice for phytoremediation. The present study investigated the growth and physiological responses of M. spicatum to different concentrations of LAS (0, 0.1, 0.5, 1, 10, 50, 100, and 500 mg/L) after 14 and 28 d of treatment. After 14 d, higher LAS doses (50-100 mg/L) significantly reduced the growth of M. spicatum compared with controls. Plants died at 500 mg/L LAS. Chlorophyll a and total chlorophyll contents were markedly increased at higher doses of LAS (10-100 mg/L). Significantly enhanced peroxidase (POD) activity was found at 50 mg/L of LAS, and decreased superoxide dismutase (SOD) activity at 100 mg/L of LAS; other indices showed no significant changes under LAS stress. After 28 d, no significant effect was observed on the growth of plants exposed to LAS doses of 0.1 to 100 mg/L, whereas plants died at 500 mg/L LAS. Compared with controls. SOD activity increased significantly at 0.1 mg/L LAS and maintained the same level as controls at higher concentrations. At all LAS exposures, POD activity was higher than that of controls. Other indices for M. spicatum were not remarkably changed at 28 d. Our results indicate that the oxidative damage to M. spicatum caused by LAS stress after 28 d is clearly less than such damage at 14 d. Environ Toxicol Chem 2019;38:2073-2081. © 2019 SETAC.

Growth and antioxidant response in Ceratophyllum demersum L. under sodium dodecyl sulfate (SDS), phenol and joint stress

Surfactants and phenolic compounds are common organic pollutants in aquatic and terrestrial ecosystems. However, the ecological risks of their combination are still unknown. This study investigated the effects of sodium dodecyl sulfate (SDS), phenol and their mixture on the growth and physiological responses of Ceratophyllum demersum L. Antagonistic effects were elicited with Phenol-SDS mixtures (≤10 + 20 mg l^-1). The results showed that photosynthetic pigments were sensitive to these toxins. The chlorophyll a, b and total chlorophyll of the plant significantly decreased under individual or the combined stress of SDS and phenol. Soluble protein content declined obviously in high stress conditions (≥1.0 mg l^-1 Phenol, ≥10 mg l^-1SDS, ≥0.5 + 1.0 mg l^-1 Phenol+SDS). To cope with oxidant stress, C. demersum can activate antioxidant defense systems, such as the increase of superoxide dismutase (SOD) and peroxidase (POD). Moreover, under combined stress, the activities of catalase (CAT), SOD and POD significantly increased relative to a single stress. Our results showed that the toxicity of SDS and phenol may be antagonistic in C. demersum in its natural environment, and their mixture did not produce more severe effects on the growth of C. demersum than each toxin individually. Furthermore, the chlorophyll content can be considered an indicator of the combined toxicity of SDS and phenol.

Identification of surfactants and its correlation with physicochemical parameters at the confluence region of Vembanad Lake in India

The present study describes the monitoring of some of the major classes of surfactants in water. The separation, identification, and the quantitative estimation of the compounds were achieved using LC-Q-ToF-MS. The analyses revealed the presence of variety of surfactants including linear alkylbenzene sulfonate (LAS), alcohol ethoxysulfates (AES), and alcohol ethoxylates (AE). Further, emphasis was given to AES as they are one of the most produced and consumed surfactants in the world. And as far as India is concerned, the present study is one of the most significant attempt regarding the identification and quantification of AES. The data obtained during the analysis revealed that the average concentration of AES C12Ex varied from 0.7 to 13.6 μg L^-1 while that of C14Ex ranged between 1.3 and 10.4 μg L^-1. The risk assessment revealed that higher chain AES are capable of posing medium level risk to the aquatic compartment. In addition, the study also included the physicochemical analysis of water from the selected area. Water was found to be acidic in nature and the salinity, TDS, and EC values were found to be high during the pre-monsoon season. The order of the levels of anionic constituents was of Cl^->SO₄^2-SO₄^2->F^->NO₃^2- ≅ PO₄^2- while that of cations were Na⁺ > Mg²⁺ > K⁺ > Ca²⁺. Results of correlation analysis showed that statistically negative correlation exists between AES homologs and pH while slight positive correlations were found between AES and other parameters including TDS and EC. The suitability of this water for domestic and agricultural purposes has been examined on the ground of basic quality indices such as the water quality index (WQI) and sodium adsorption ratio (SAR). The WQI measurements also revealed that the water quality of the region falls under the "very poor" category especially during the pre-monsoon season. The study could explore the cumulative share of these canals in the quality impairment of the receiving Vembanad Lake.

Toxic effects of linear alkylbenzene sulfonate on Chara vulgaris L

Linear alkylbenzene sulfonate (LAS) is a common organic pollutant in freshwater environments. Studies have shown that the toxicity of LAS to aquatic plants is directly related to the LAS concentration and depends on the plant species. A 2-week exposure experiment was designed to investigate the toxicity of LAS for the submerged plant Chara vulgaris L. and focused on the effects on growth, photosynthetic pigment content, and antioxidant enzyme activity. The results showed that when exposed to lower LAS doses (≤ 1.0 mg l^-1), the dry weight of C. vulgaris was significantly reduced. Compared to those of the control group, superoxide dismutase (SOD) and peroxidase (POD) activities significantly increased, while no significant effect was observed for catalase (CAT) activity. Malondialdehyde (MDA) content significantly increased in the LAS treatment groups except for the LAS concentration of 1.0 mg l^-1. The content of carotenoids was significantly lower in plant groups exposed to lower concentrations of LAS, while carotenoid content significantly increased at the highest concentration of LAS (5.0 mg l^-1). LAS treatment did not significantly affect chlorophyll a and b or total chlorophyll content. The results showed that 5.0 mg l^-1 causes some oxidative damage to C. vulgaris but that this concentration was far below the lethal concentration of LAS to C. vulgaris and did not produce severe effects on growth. C. vulgaris plants had some resistance to LAS stress (in the group with ≤ 5.0 mg l^-1). SOD, POD, and carotenoids were more sensitive to the effects of LAS stress and may be considered as response indicators for LAS stress.

Comprehensive review of several surfactants in marine environments: Fate and ecotoxicity

Surfactants are a commercially important group of chemicals widely used on a global scale. Despite high removal efficiencies during wastewater treatment, their high consumption volumes mean that a certain fraction will always enter aquatic ecosystems, with marine environments being the ultimate sites of deposition. Consequently, surfactants have been detected within marine waters and sediments. However, aquatic environmental studies have mostly focused on the freshwater environment, and marine studies are considerably underrepresented by comparison. The present review aims to provide a summary of current marine environmental fate (monitoring, biodegradation, and bioconcentration) and effects data of 5 key surfactant groups: linear alkylbenzene sulfonates, alcohol ethoxysulfates, alkyl sulfates, alcohol ethoxylates, and ditallow dimethyl ammonium chloride. Monitoring data are currently limited, especially for alcohol ethoxysulfates and alkyl sulfates. Biodegradation was shown to be considerably slower under marine conditions, whereas ecotoxicity studies suggest that marine species are approximately equally as sensitive to these surfactants as freshwater species. Marine bioconcentration studies are almost nonexistent. Current gaps within the literature are presented, thereby highlighting research areas where additional marine studies should focus.

Surfactants in aquatic and terrestrial environment: occurrence, behavior, and treatment processes

Surfactants belong to a group of chemicals that are well known for their cleaning properties. Their excessive use as ingredients in care products (e.g., shampoos, body wash) and in household cleaning products (e.g., dishwashing detergents, laundry detergents, hard-surface cleaners) has led to the discharge of highly contaminated wastewaters in aquatic and terrestrial environment. Once reached in the different environmental compartments (rivers, lakes, soils, and sediments), surfactants can undergo aerobic or anaerobic degradation. The most studied surfactants so far are linear alkylbenzene sulfonate (LAS), quaternary ammonium compounds (QACs), alkylphenol ethoxylate (APEOs), and alcohol ethoxylate (AEOs). Concentrations of surfactants in wastewaters can range between few micrograms to hundreds of milligrams in some cases, while it reaches several grams in sludge used for soil amendments in agricultural areas. Above the legislation standards, surfactants can be toxic to aquatic and terrestrial organisms which make treatment processes necessary before their discharge into the environment. Given this fact, biological and chemical processes should be considered for better surfactants removal. In this review, we investigate several issues with regard to: (1) the toxicity of surfactants in the environment, (2) their behavior in different ecological systems, (3) and the different treatment processes used in wastewater treatment plants in order to reduce the effects of surfactants on living organisms.

Effects of linear alkylbenzene sulfonate on the growth and toxin production of Microcystis aeruginosa isolated from Lake Dianchi

The exogenous organic pollutant linear alkylbenzene sulfonate (LAS) pollution and Microcystis bloom are two common phenomena in eutrophic lakes, but the effects of LAS alone on Microcystis remain unclear. In the present study, we investigated the effects of LAS on the growth, photochemical efficiency, and microcystin production of Microcystis aeruginosa in the laboratory. Results showed that low LAS (≤10 mg/L) concentrations improved the growth of M. aeruginosa (12 days of exposure). High LAS (20 mg/L) concentrations inhibited the growth of M. aeruginosa on the first 8 days of exposure; afterward, growth progressed. After 12 days of exposure, the concentrations of chlorophyll a in algal cells were not significantly affected by any of LAS concentrations (0.05 to 20 mg/L) in the present study; by contrast, carotenoid and protein concentrations were significantly inhibited when LAS concentrations reached as high as 20 mg/L. After 6 and 12 days of exposure, low LAS (≤10 mg/L) concentrations enhanced the maximal photochemical efficiency (Fv/Fm) and the maximal electron transport rate (ETRmax) of M. aeruginosa. Furthermore, LAS increased the microcystin production of M. aeruginosa. Extracellular and intracellular microcystin contents were significantly increased after M. aeruginosa was exposed to high LAS concentrations. Our results indicated that LAS in eutrophic lakes may increase the risk of Microcystis bloom and microcystin production.