Vertical distribution profiles and diagenetic fate of synthetic surfactants in marine and freshwater sediments

Historical trends of polychlorinated biphenyls and alkylphenols recorded in core sediments from the intertidal areas of the Yellow Sea and Bohai Sea

Historical records of polychlorinated biphenyls (PCBs) and alkylphenols (APs) were reconstructed from intertidal zones of the Yellow and Bohai Seas over the past 80 years. Concentrations of PCBs (1.50-6.47 ng g-1 organic carbon (OC)) and APs (8.42-13.8 ng g-1 OC) in Dangjin, South Korea, peaked in the 1970s and subsequently declined. Conversely, levels in Tianjin and Dandong, China, have continued to increase in recent decades (PCBs: 0.53-6.1 ng g-1 OC; APs: 2.61-42.7 ng g-1 OC). These divergent trends align with regulatory enforcement: levels in South Korea declined following the implementation of regulations in 1979 and 2003, while the continued increase in China, despite regulation in 1974 and 2011, points to unregulated sources. Estimated fluxes of PCBs and APs from the intertidal zone to offshore areas decreased by approximately 83% and 57%, respectively. This study provides baseline data for assessing long-term pollution trends in intertidal environments.

Decoupling Sources of Anthropogenic Influences on Sediments of the Visovac Lake (Krka National Park, Croatia) Using Multiparametric Approach

Historical changes of sediment characteristics and levels of inorganic and organic contaminants were studied in dated sediment cores from the Visovac Lake, situated in the Krka National Park, Croatia, to identify the main sources of anthropogenic pressures on this highly protected system. Depth distributions of lithogenic elements showed a steady decrease of terrigenous inputs due to the reduction in agricultural activities in the area, which was particularly pronounced during the 1991-1995 war in Croatia. Vertical and longitudinal distributions of Cd and Zn indicated that they are predominately of anthropogenic origin. The historical profiles of these toxic metals coincide well with the recorded production of metal industry in the upper reach of the Krka River with a sharp decrease reflecting the interruption by the war and slow recovery afterwards. By contrast, the recovery of the tourist industry in Krka NP after the war was accompanied by increasing contamination by elements characteristic of boat and car traffic (Sn, Cu, Pb) as well as oil pollution. The contamination with polycyclic aromatic hydrocarbons and polychlorinated biphenyls was only moderate. Although levels of metallic and organic contamination can be considered relatively low, the observed shift from industrial to tourism-related sources indicated that touristic activities should also be regarded as a possible threat for this vulnerable karst aquatic ecosystem.

Comparative analysis of microbial community under acclimation of linear alkylbenzene sulfonate (LAS) surfactants and degradation mechanisms of functional strains

Linear alkylbenzene sulfonate (LAS) is one of the most widely used anionic surfactants and a common toxic pollutant in wastewater. This study employed high throughput sequencing to explore the microbial community structure within activated sludge exposed to a high concentration of LAS. Genera such as Pseudomonas, Aeromonas, Thauera and Klebsiella exhibited a significant positive correlation with LAS concentrations. Furthermore, Comamonas and Klebsiella were significantly enriched under the stress of LAS. Moreover, bacterial strains with LAS-degrading capability were isolated and characterized to elucidate the degradation pathways. The Klebsiella pneumoniae isolate L1 could effectively transform more than 60 % of 25 mg/L of LAS within 72 h. Chemical analyses revealed that L1 utilized the LAS sulfonyl group as a sulfur source to support its growth. Genomic and transcriptomic analyses suggested that strain L1 may uptake LAS through the sulfate ABC transport system and remove sulfonate with sulfate and sulfite reductases.

Use of nitrate, sulphate, and iron (III) as electron acceptors to improve the anaerobic degradation of linear alkylbenzene sulfonate: effects on removal potential and microbiota diversification

Linear alkylbenzene sulfonate (LAS) is a synthetic anionic surfactant that is found in certain amounts in wastewaters and even in water bodies, despite its known biodegradability. This study aimed to assess the influence of nitrate, sulphate, and iron (III) on LAS anaerobic degradation and biomass microbial diversity. Batch reactors were inoculated with anaerobic biomass, nutrients, LAS (20 mg L-1), one of the three electron acceptors, and ethanol (40 mg L-1) as a co-substrate. The control treatments, with and without co-substrate, showed limited LAS biodegradation efficiencies of 10 ± 2% and 0%, respectively. However, when nitrate and iron (III) were present without co-substrate, biodegradation efficiencies of 53 ± 4% and 75 ± 3% were achieved, respectively, which were the highest levels observed. Clostridium spp. was prominent in all treatments, while Alkaliphilus spp. and Bacillus spp. thrived in the presence of iron, which had the most significant effect on LAS biodegradation. Those microorganisms were identified as crucial in affecting the LAS anaerobic degradation. The experiments revealed that the presence of electron acceptors fostered the development of a more specialised microbiota, especially those involved in the LAS biodegradation. A mutual interaction between the processes of degradation and adsorption was also shown.

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

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

Distribution and diagenetic fate of synthetic surfactants and their metabolites in sewage-impacted estuarine sediments

Surfactants are high production volume chemicals used in numerous domestic and industrial applications and, after use, the most abundant organic contaminants in wastewater. Their discharge might jeopardize the receiving aquatic ecosystems, including sediments, where they tend to accumulate. This is the first comprehensive study on their distribution and fate in this environmental compartment as we performed simultaneous analysis of the three main classes of surfactants (anionic: LAS; nonionic: NPEO and AEO; cationic: DTDMAC, DADMAC, BAC, and ATMAC) and some of their transformation products (SPC, NP, NPEC, and PEG). To account for spatial and time trends, surface sediments and dated cores were collected from Jamaica Bay, a heavily sewage-impacted estuary in New York City. The concentrations of surfactants in surface sediments were between 18 and > 200 μg g^-1 and showed slight variation (<10%) over different sampling years (1998, 2003 and 2008). Cationic surfactants were found at the highest concentrations, with DTDMAC accounting for between 52 and 90% of the total sum of target compounds. Vertical concentration profiles in dated cores from the most contaminated station, in the vicinity of the biggest local sewage treatment plant (STP), indicated two sub-surface surfactant peaks in the mid-1960s (469 μg g^-1) and late 1980s (572 μg g^-1) coinciding with known STP upgrades. This trend was observed for most target compounds, except for DADMAC, C22ATMAC, and PEG, which showed a continuous increase towards the top of the cores. In-situ degradation was studied by comparing sediment core samples taken 12 years apart (1996 and 2008) and revealed a net decrease in PEG and specific surfactants (BAC, ATMAC, NPEO, and AEO) accompanied by growing concentrations of metabolites (SPC, NP, and NPEC). DTDMAC, DADMAC, and LAS, however, remained stable over this period, suggesting recalcitrant behavior under the anaerobic conditions in Jamaica Bay sediments.

MAIN FINDING

Chronology of major synthetic surfactants are illustrated in the dated sediment cores, as well as their different diagenetic fates.

Effects of extreme rainfall events on the distribution of selected emerging contaminants in surface and groundwater: The Guadalete River basin (SW, Spain)

This study is focused on the Guadalete River basin (SW, Spain), where extreme weather conditions have become common, with and alternation between periods of drought and extreme rainfall events. Combined sewer overflows (CSOs) occur when heavy rainfall events exceed the capacity of the wastewater treatment plants (WWTP), as well as pollution episodes in parts of the basin due to uncontrolled sewage spills and the use of reclaimed water and sludge from the local WWTP. The sampling was carried out along two seasons and three campaigns during dry (March 2007) and extreme rainfall (April and December 2010) in the Guadalete River, alluvial aquifer and Jerez de la Frontera aquifer. Results showed minimum concentrations for synthetic surfactants in groundwater (<37.4μg·L^-1) during the first campaign (dry weather conditions), whereas groundwater contaminants increased in December 2010 as the heavy rainfall caused the river to overflow. In surface water, surfactant concentrations showed similar trends to groundwater observations. In addition to surfactants, pharmaceuticals and personal care products (PPCPs) were analyzed in the third campaign, 22 of which were detected in surface waters. Two fragrances (OTNE and galaxolide) and one analgesic/anti-inflammatory (ibuprofen) were the most abundant PPCPs (up to 6540, 2748 and 1747ng·L^-1, respectively). Regarding groundwater, most PPCPs were detected in Jerez de la Frontera aquifer, where a synthetic fragrance (OTNE) was predominant (up to 1285ng·L^-1).

Determining the distribution of pharmaceutically active compounds (PhACs) in soils and sediments by pressurized hot water extraction (PHWE)

The occurrence of pharmaceutically active compounds (PhACs) in the environment may pose a potential risk for humans and ecosystems. Wastewater treatment plants (WWTPs) are recognized as one of the main sources of these chemicals into both aquatic and terrestrial environments. The objectives of the study were to determine the presence of a wide variety of PhACs (n = 45) in sewage-impacted sediments and soils from the Guadalete River basin (SW Spain) by developing and applying an environmentally friendly multi-residue method based on pressurized hot water extraction (PHWE). Different parameters were optimized, including extraction temperature, pH, solvents, and clean-up. Extraction recoveries were analyte dependent, varying between 50% and 140% for most of the analytes when using pure water as extraction solvent at 100 °C. Determination of PhACs was performed by ultra-high performance liquid chromatography - tandem mass spectrometry (UPLC-MS/MS), enabling method detection (mLODs) and quantification (mLOQs) limits between <0.01 and 0.83 ng g^-1 and from 0.02 to 2.75 ng g^-1, respectively. Regarding the sampling area, 14 out of 45 target compounds were detected in soils and sediments. Analgesic/anti-inflammatories was the therapeutic group most commonly detected, reaching concentrations up to 20 ng g^-1.

4-Nonylphenol induces disruption of spermatogenesis associated with oxidative stress-related apoptosis by targeting p53-Bcl-2/Bax-Fas/FasL signaling

4-Nonylphenol (NP) is a ubiquitous environmental chemical with estrogenic activity. Our aim was to test the hypothesis that pubertal exposure to NP leads to testicular dysfunction. Herein, 24 7-week-old rats were randomly divided into four groups and treated with NP (0, 25, 50, or 100 mg/kg body weight every 2 days for 20 consecutive days) by intraperitoneal injection. Compared to untreated controls, the parameters of sperm activation rate, curvilinear velocity, average path velocity, and swimming velocity were significantly lower at doses of 100 mg/kg, while sperm morphological abnormalities were higher, indicating functional disruption and reduced fertilization potential. High exposure to NP (100 mg/kg) resulted in disordered arrangement of spermatoblasts and reduction of spermatocytes in seminiferous tubules, while tissues exhibited a marked decline in testicular fructose content and serum FSH, LH, and testosterone levels. Oxidative stress was induced by NP (50 or 100 mg/kg) as evidenced by elevated MDA, decreased SOD and GSH-Px, and inhibited antioxidant gene expression (CAT, GPx, SOD1, and CYP1B1). In addition, NP treatment decreased proportions of Ki-67-positive cells and increased apoptosis in a dose-dependent manner. Rats treated with 100 mg/kg NP exhibited significantly increased mRNA expression of caspase-1, -2, -9, and -11, decreased caspase-8 and PCNA1 mRNA expression, downregulation of Bcl-2/Bax ratios and upregulation of Fas, FasL, and p53 at the protein and mRNA levels. Taken together, NP-induced apoptosis, hormonal deficiencies, and depletion of fructose potentially impairs spermatogenesis and sperm function. p53-independent Fas/FasL-Bax/Bcl-2 pathways may be involved in NP-induced oxidative stress-related apoptosis. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 739-753, 2017.

Sorption, degradation and transport phenomena of alcohol ethoxysulfates in agricultural soils. Laboratory studies

In the present work, laboratory studies were conducted in order to determine and model the sorption, degradation and transport processes of alcohol ethoxysulfates (AES), one of the most important groups of anionic surfactants. Adsorption/desorption isotherms were obtained for several structurally related AES ethoxymers (homologue AES-C₁₂E_n with n = 0-10 ethoxymer units and homologue AES-C₁₄E_n with n = 0-7 ethoxymer units) using a batch equilibrium method. Data were fitted to a linear and a Freundlich isotherm models. Additionally, experiments in continuous-flow soil columns were also carried out and the breakthrough curves observed for each compound were studied. Breakthrough curves were used to determine the fundamental parameters of the transport model (hydrodynamic dispersion coefficient, degradation rate constant and adsorption/desorption isotherm slope), that is the main phenomena that take place simultaneously when AES move through agricultural soil. When the results obtained for the AES ethoxymers are combined, they reveal a clear and consistent trend towards a sorption increase with the number of ethoxylated units and with the length of the alkyl chain that opens the possibility to estimate the values of the transport parameters for other structurally related ethoxymers.

Anaerobic degradation of alcohol ethoxylates and polyethylene glycols in marine sediments

This research is focused on alcohol polyethoxylates (AEOs), nonionic surfactants used in a wide variety of products such as household cleaners and detergents. Our main objective in this work was to study the anaerobic degradation of these compounds and their main aerobic degradation products and precursors (polyethylene glycols, PEGs, which are also used for many other applications) in marine sediments, providing the first data available on this topic. First, we observed that average AEO sediment-water partition coefficients (Kd) increased towards those homologs having longer alkyl chains (from 257 L/kg for C12 to 5772 L/kg for C18),which were less susceptible to undergo biodegradation. Overall, AEO and PEG removal percentages reached up to 99.7 and 93%, respectively, after 169 days of incubation using anaerobic conditions in sediments ([O2] = 0 ppm, Eh = -170 to -380 mV and T = 30 °C). Average half-life was estimated to be in a range from 10 to 15 days for AEO homologs (C12AEO8-C18AEO8), and 18 days for PEGEO8.Methanogenic activity proved to be intense during the experiment, confirming the occurrence of anaerobic conditions. This is the first study showing that AEOs and PEGs can be degraded in absence of oxygen in marine sediments, so this new information should be taken into account for future environmental risk assessments on these chemicals.

Occurrence and spatial distribution of emerging contaminants in the unsaturated zone. case study: Guadalete River basin (Cadiz, Spain)

Irrigation with reclaimed water is becoming a common practice in arid- and semi-arid regions as a consequence of structural water resource scarcity. This practice can lead to contamination of the vadose zone if sewage-derived contaminants are not removed properly. In the current work, we have characterized soils from the Guadalete River basin (SW Spain), which are often irrigated with reclaimed water from a nearby wastewater treatment plant and amended using sludge. Physico-chemical, mineralogical and hydraulic properties were measured in soil samples from this area (from surface up to 2 m depth). Emerging contaminants (synthetic surfactants and pharmaceutically active compounds, or PhACs) were also determined. Synthetic surfactants, widely used in personal care products (PCPs), were found in a wide range of concentrations: 73-1300 μg kg(-1) for linear alkylbenzene sulfonates (LAS), 120-496 μg kg(-1) for alkyl ethoxysulfates (AES), 19-1090 μg kg(-1) for alcohol polyethoxylates (AEOs), and 155-280 μg kg(-1) for nonylphenol polyethoxylates (NPEOs). The presence of surfactant homologues with longer alkyl chains was predominant due to their sorption capacity. A positive correlation was found between LAS and AEOs and soil organic carbon and clay content, respectively. Out of 64 PhACs analyzed, only 7 were detected occasionally (diclofenac, metoprolol, fenofibrate, carbamazepine, clarithromycin, famotidine and hydrochlorothiazide), always at very low concentrations (from 0.1 to 1.3 μg kg(-1)).