NSO-heterocyclic PAHs - Controlled exposure study reveals high acute aquatic toxicity.

Environmental occurrence and hazardous nature of heterocyclic polyaromatic hydrocarbons (heterocyclic PAHs) has the potential to threaten the health of aquatic ecosystems. Here, we investigate the acute toxicity of heterocyclic PAHs (log KOW 3.7-6.9) to aquatic organisms: marine bacteria (Aliivibrio fischeri), freshwater green algae (Raphidocelis subcapitata), and water fleas (Daphnia magna) using passive dosing to maintain stable exposure. The membrane-water partition coefficient (KMW) of the heterocycles was measured to elucidate its relationship with toxicity. Our findings show that the tested heterocycles had little inhibitory effect on A. fischeri, while most compounds were highly toxic to R. subcapitata and D. magna. Toxicity generally increased with increasing KMW values, and nonpolar narcosis was identified as the most likely mode of toxic action of the heterocycles. Comparison of standard protocols with passive dosing emphasizes the importance of maintaining a constant concentration during toxicity testing, as very high losses occurred in standard tests and passive dosing experiments revealed higher toxicities. These results indicate a potentially high risk to aquatic life and call for more in-depth investigation of the (eco)toxic effects of NSO-PAHs.

Environmental persistence assessment of heterocyclic polyaromatic hydrocarbons - Ultimate and primary biodegradability using adapted and non-adapted microbial communities.

Heterocyclic polyaromatic hydrocarbons (heterocyclic PAHs) are of increasing concern and their environmental and human health impacts should be assessed due to their widespread presence and potential persistence in the environment. This study investigated the ultimate and primary biodegradability of ten heterocyclic PAHs, nine of which were found to be non-readily biodegradable. To generate a microbial community capable of degrading such compounds, a bacterial inoculum isolated from the effluent of a wastewater treatment plant (WWTP) was adapted to a mixture of heterocyclic PAHs for one year. Throughout the adaptation process, bacterial samples were collected at different stages to conduct primary biodegradation, ultimate biodegradation, and inoculum toxicity tests. Interestingly, after one year of adaptation, the community developed the ability to mineralize carbazole, but in the same time showed an increasing sensitivity to the toxic effects of benzo[c]carbazole. In two consecutive primary biodegradation experiments, degradation of four heterocycles was observed, while no biodegradation was detected for five compounds in any of the tests. Furthermore, the findings of this work were compared with predictions from in silico models regarding biodegradation timeframe and sorption, and it was found that the models were partially successful in describing these processes. The results of study provide valuable insights into the persistence of a representative group of heterocyclic PAHs in aquatic environments, which contributes to the hazard assessment of this particular class of substances.

Environmental Hazard Screening of Heterocyclic Polyaromatic Hydrocarbons: Physicochemical Data and In Silico Models.

Heterocyclic polyaromatic hydrocarbons (heterocyclic PAHs) are frequently found in the environment yet, compared to homocyclic PAHs, little attention has been paid to their environmental behavior and a comprehensive hazard assessment has not been undertaken. Surprisingly, the physicochemical data necessary to perform at least a screening-level assessment are also limited. To address this, we began by experimentally determining the physicochemical properties of heterocyclic PAHs, namely, water solubility (Sw), n-octanol-water partition coefficients (Kow), and organic carbon-water partition coefficients (Koc). The physicochemical data obtained in this study allowed for the development of clear structure-property relationships and evaluation of the predictive power of in silico models including conductor-like screening model for realistic solvation, the poly-parameter linear solvation energy relationship, and the quantitative structure-property relationship. Finally, heterocyclic and homocyclic PAHs were evaluated in terms of persistence, bioaccumulation, mobility, and toxicity to perform a screening-level comparative hazard assessment by integrating the data and evidence from multiple sources.

Environmental contamination by microplastics originating from textiles: Emission, transport, fate and toxicity.

Microplastic (MP) pollution has become a global concern in terms of its environmental abundance and potential detrimental effects. Fibrous microplastics (FMPs) released from synthetic textiles are believed to contribute significantly to environmental MP pollution. This review provides an overview of current knowledge relating to the environmental impact of FMPs through a summary and discussion of (1) the concentrations in different environmental compartments including water, soil and air, (2) emission from wastewater treatment plants: via effluent discharges to waters and via sludge to land, (3) environmental transport and fate, and (4) toxicity and associated effects. How the properties of FMPs influence these aspects is discussed and their behaviour is compared to MPs of other shapes. We have summarised the Environmental Concentrations and derived Predicted No-Effect Concentrations for a preliminary risk assessment of FMPs by extrapolating the risk quotient for each respective environmental compartment. The uncertainties surrounding current assessment methods are discussed. In particular we address the need to improve determination of exposure levels and to better characterise the effects of FMPs. We conclude by presenting topics for future studies to address, which will improve our still limited understanding of the interactions between FMPs and the environment.

Treatment of electropolishing industrial wastewater and its impact on the immobilisation of Daphnia magna.

The amount of industrial pollution entering the environment and its impact on living organisms is an ongoing concern. At the same time, due to an increasing awareness, new methods of wastewater treatment are being explored that are not only effective but also environmentally acceptable. Meeting environmental standards for permitted concentrations is a necessity, but investigating the effects of wastewater on living organisms is also an important issue. In this paper, the influence of metal ions (Fe(III), Cr(III), Ni(II), Cu(II)) in industrial wastewater from electropolishing of stainless steel on Daphnia magna has been investigated. Daphnids have been exposed to wastewater both before and after treatment (Ca(OH)2 precipitation, sorption with peat). Immobilisation in a 48-h acute toxicity test and EC50 has been determined. In the case of studied industrial wastewater, the organic content (expressed as total organic carbon) of the effluent has a positive impact in terms of the survival of D. magna and increases the range of heavy metal concentrations tolerated by them. The application of a two-stage process with Ca(OH)2 neutralisation followed by sorption with peat allows for the removal of almost 100% of metal ions from the wastewater. The reduction obtained ensured a limited impact on D. magna and a decrease in immobilisation to less than 10%. Proper execution of the wastewater treatment process ensures a reduction of its negative impact on living organisms.

Toward the Proactive Design of Sustainable Chemicals: Ionic Liquids as a Prime Example.

The tailorable and often unique properties of ionic liquids (ILs) drive their implementation into a broad variety of seminal technologies. The modular design of ILs allows in this context a proactive selection of structures that favor environmental sustainability─ideally without compromising their technological performance. To achieve this objective, the whole life cycle must be taken into account and various aspects considered simultaneously. In this review, we discuss how the structural design of ILs affects their environmental impacts throughout all stages of their life cycles and scrutinize the available data in order to point out knowledge gaps that need further research activities. The design of more sustainable ILs starts with the selection of the most beneficial precursors and synthesis routes, takes their technical properties and application specific performance into due account, and considers its environmental fate particularly in terms of their (eco)toxicity, biotic and abiotic degradability, mobility, and bioaccumulation potential. Special emphasis is placed on reported structure-activity relationships and suggested mechanisms on a molecular level that might rationalize the empirically found design criteria.

Toxicity of a Quinaldine-Based Liquid Organic Hydrogen Carrier (LOHC) System toward Soil Organisms Arthrobacter globiformis and Folsomia candida.

The study aims to establish a preliminary environmental assessment of a quinaldine-based LOHC system composed of hydrogen-lean, partially hydrogenated, and fully hydrogenated forms. We examined their toxicity toward the soil bacteria Arthrobacter globiformis and the Collembola Folsomia candida in two exposure scenarios, with and without soil, to address differences in the bioavailability of the compounds. In both scenarios, no or only slight toxicity toward soil bacteria was observed at the highest test concentration (EC50 > 3397 µmol L-1 and >4892 µmol kg-1 dry weight soil). The effects of the three quinaldines on F. candida in soil were similar, with EC50 values ranging from 2119 to 2559 µmol kg-1 dry weight soil based on nominal concentrations. Additionally, corrected pore-water-concentration-based EC50 values were calculated by equilibrium partitioning using soil/pore-water distribution coefficients. The tests without soil (simulating pore-water exposure) revealed higher toxicity, with LC50 values between 78.3 and 161.6 µmol L-1 and deformation of the protective cuticle. These results assign the compounds to the category "harmful to soil organisms". Potential risks toward the soil environment of the test compounds are discussed on the basis of predicted no-effect concentrations.

Membrane partitioning of ionic liquid cations, anions and ion pairs - Estimating the bioconcentration potential of organic ions.

Recent efforts have been directed towards better understanding the persistency and toxicity of ionic liquids (ILs) in the context of the "benign-by-design" approach, but the assessment of their bioaccumulation potential remains neglected. This paper reports the experimental membrane partitioning of IL cations (imidazolium, pyridinium, pyrrolidinium, phosphonium), anions ([C(CN)3]-, [B(CN)4]-, [FSO2)2N]-, [(C2F5)3PF3]-, [(CF3SO2)2N]-) and their combinations as a measure for estimating the bioconcentration factor (BCF). Both cations and anions can have a strong affinity for phosphatidylcholine bilayers, which is mainly driven by the hydrophobicity of the ions. This affinity is often reflected in the ecotoxicological impact. Our data revealed that the bioconcentration potential of IL cations and anions is much higher than expected from octanol-water-partitioning based estimations that have recently been presented. For some ILs, the membrane-water partition coefficient reached levels corresponding to BCFs that might become relevant in terms of the "B" (bioaccumulation potential) classification under REACH. However, this preliminary estimation need to be confirmed by in vivo bioconcentration studies.

Ultimate biodegradability and ecotoxicity of orally administered antidiabetic drugs.

Hypoglycaemic pharmaceuticals are recently more and more frequently detected in the environment. In our previous study, we have shown that even though many of them undergo significant primary degradation some are transformed to stable products or undergo such transformation that a large part of the structure is still preserved. One of the main routes of elimination from wastewaters or surface waters is biodegradation and a lack thereof leads to accumulation in the environment. Within this work we tested the ultimate biodegradability of six oral antidiabetics: metformin and its main metabolite guanylurea, acarbose, glibenclamide, gliclazide, glimepiride and repaglinide. We also compared the experimental results obtained in this and accompanying work with models designed to predict biodegradability and showed that these models are only moderately successful. Additionally, we examined these compounds in acute Daphnia magna test to check if they might pose an ecotoxicological threat. Combining the results of biodegradability and toxicity tests allows a preliminary assessment of their potential environmental impact.

Mixture toxicity of flubendazole and fenbendazole to Daphnia magna.

Nowadays, residual amounts of many pharmaceuticals can be found in various environmental compartments including surface and ground waters, soils and sediments as well as biota. Even though they undergo degradability, their environmental discharge is relatively continuous, thus they may be regarded as quasi-persistent contaminants, and are also frequently regarded as emerging organic pollutants. Benzimidazoles, especially flubendazole (FLU) and fenbendazole (FEN), represent two anthelmintic drugs belonging to this group. Although their presence in environmental matrices has been reported, there is relatively little data concerning their (eco)toxicological impact. Furthermore, no data is available on their mixture toxicity. FLU and FEN have been found to have a strong impact on an environmentally important non-target organism - Daphnia magna. Moreover, these compounds are usually present in the environment as a part of pharmaceutical mixtures. Therefore, there is a need to evaluate their mixture toxicity, which was the main aim of this study. Single substance toxicity tests were carried out in parallel with mixture studies of FLU and FEN, with the application of two well established concepts of Concentration Addition (CA) and Independent Action (IA). As a result, both models (CA and IA) were found to underestimate the toxicity of mixtures, however CA yielded more accurate predictions.

Primary degradation of antidiabetic drugs.

Type 2 diabetes is a chronic disease affecting a large portion of the world population and is treated by orally administered drugs. Since these drugs are often taken in high doses and are excreted unchanged or partially metabolised many of them are nowadays detected in surface waters or wastewater treatment plants effluents. Unmetabolised antidiabetics or some of their transformation products retain their pharmacological activity, therefore their presence in the environment is highly undesired. One of the main routes of elimination from wastewaters or surface waters is biodegradation. Within this work we tested primary biodegradation of: metformin and its metabolite guanylurea, acarbose, glibenclamide, gliclazide and glimepiride. We also inspected what might be the extent of the degradation by examining the products formed during the degradation using liquid chromatography coupled to tandem mass spectrometry. Transformation of diabetes staple drug metformin to dead-end product guanylurea was generally confirmed. An alternative, though rather minor pathway leading to complete mineralisation was also found. Complete primary degradation was observed for acarbose, glibenclamide and glimepiride whereas gliclazide was shown to be resistant to biodegradation. These results allow a preliminary assessment of environmental persistency of a very important group of pharmaceuticals and show need for implementing monitoring programs.

Ionic liquid assisted dissolution of dissolved organic matter and PAHs from soil below the critical micelle concentration.

Increased use and production of ionic liquids (ILs) may result in emissions into the environment. Particularly vulnerable are industrial areas and landfills where ILs are utilized and ultimately disposed of. This study investigates how IL contamination can affect soil properties and the sorption of pre-existing contaminants. The commonly used IL 1-methyl-3-octyl imidazolium chloride ([OMIM][Cl]) was added at various quantities to a landfill soil contaminated with polycyclic aromatic hydrocarbons (PAHs). Subsequently, the release of PAHs and dissolved organic matter (DOM) from this soil was thoroughly investigated. Two fractions of PAH release into the porewater were measured, the freely dissolved fraction (measured using a passive sampler) and the total PAH concentration (which includes the freely dissolved molecules as well as those associated with colloids, micelles and DOM). As expected the highest levels of total PAH porewater concentration occurred when the critical micelle concentration (CMC) of the IL was exceeded. However, as we report here for the first time, enhanced amounts of freely dissolved PAHs were released by sub-CMC concentrations of IL. Additionally, enhanced levels of DOM, due to dissolution of soil organic matter by IL, were also observed upon addition of sub-CMC IL concentrations. Based on this, enhanced release of pre-existing contaminants and DOM is suggested as a potential risk from IL emissions at trace concentrations well below the CMC. Potential mechanisms of this sub-CMC release are discussed.

Toxicity of ionic liquid cations and anions towards activated sewage sludge organisms from different sources -- consequences for biodegradation testing and wastewater treatment plant operation.

Ionic liquids (ILs) have attracted great interest in academia and industry during the last decade. So far, several ILs have been used in technological processes, from small scale to industrial applications, which makes it more and more likely that they will be released into the environment. Researchers have been actively studying the environmental and toxicological behaviour of ILs, but their influence on the activated sludge communities of wastewater treatment plants have yet to be investigated. This study aims to fill this knowledge gap by systematically investigating the influence of ILs on activated sewage sludge communities. We tested the inhibition of activated sludge respiration (according to OECD guideline 209) by a selection of 19 different compounds covering the chemical space of ILs as comprehensively as possible. To elicit the differences in sensitivities/tolerances towards ILs we investigated activated sludge from different domestic and industrial sources. Generally speaking, the structure activity relationships of IL toxicity towards activated sludge are in good agreement with those found for other organisms and test systems. The inhibitory potential of tested ILs substituted with short alkyl chains (≤ 4) and polar anions was low. On the other hand, the toxic effects of highly hydrophobic ionic cations and anions were greater - IC50 values were low, some < 50 µM (<10 mg L(-1)). We were able to demonstrate that the EC50 values from Vibrio fischeri can be used for a reliable assessment of the sludge inhibition potential of tested ILs. All the results are discussed in the context of their consequences for biodegradation processes and the performance of wastewater treatment plants.

Solubilization of benzene, toluene, and xylene (BTX) in aqueous micellar solutions of amphiphilic imidazolium ionic liquids.

Water-soluble ionic liquids may be considered analogues to cationic surfactants with a corresponding surface activity and ability to create organized structures in aqueous solutions. For the first time, the enhanced solubility of the aromatic hydrocarbons, benzene, toluene, and xylene, in aqueous micellar systems of 1-alkyl-3-methylimidazolium chlorides was investigated. Above a critical micelle concentration, a gradual increase in the concentration of aromatic hydrocarbons in the miceller solution was observed. This phenomenon was followed by means of the molar solubilization ratio, the micellar/water partition coefficient, and the number of solubilizate molecules per IL micelle. The molar solubilization ratio for ionic liquid micelles was found to be significantly higher when compared to that of ionic surfactants of similar chain length. The incorporation of the hydrocarbon into the micelle affects also an increase of the aggregation number.

Changes in zeta potential of imidazolium ionic liquids modified minerals--Implications for determining mechanism of adsorption.

As the amount of industrial processes involving ionic liquids (ILs) increase the question of their environmental fate awaits an answer. Should ILs become a source of pollution they will primarily be found in soils and water. Interaction of imidazolium IL with soils is a complex interplay of many parameters making predicting their fate and mobility a challenging task. In order to shed more light on the mechanism of adsorption in soils we examined the interactions of imidazolium ILs with the major component of soils, namely mineral fraction. Within this work adsorption on kaolinite and quartz was investigated in terms of adsorption isotherms, partition coefficients and changes of zeta potentials of clays modified by ILs aggregates. The zeta potential was found to be dependent on the alkyl chain length of the imidazolium homologues. It can therefore be concluded that although adsorption seems to rely on electrostatic attraction, at least in the initial stage, the hydrophobicity of molecules is just as significant.

Influence of microbial adaption and supplementation of nutrients on the biodegradation of ionic liquids in sewage sludge treatment processes.

As ionic liquids are winning more attention from industry as a replacement of more hazardous chemicals, some of their structures have the potential to become persistent pollutants due to high stability towards abiotic and biotic degradation processes. Therefore it is important to determine the hazard associated with the presence of ILs in the environment, for example biodegradation under real conditions. Standard biodegradation testing procedures generally permit pre-conditioning of inoculum but do not allow for pre-exposition to the test substance. These are usually conducted in a mineral medium which does not provide additional organic nutrients. Though very valuable, as a point of reference, these tests do not fully represent real conditions. In in situ conditions, for example in wastewater treatment plants or natural soils and water bodies, the presence of readily available sources of energy and nutrients as well as the process of adaptation may often alter the fate and metabolic pathways of xenobiotics. Our results have shown that these are the opposing processes influencing the biodegradation rate of ILs in sewage sludge. The results have significant practical implications with respect to the assessment of biodegradability and environmental fate of ILs and other xenobiotics in environmental conditions and their potential remediation options.

Influence of the Hofmeister anions on self-organization of 1-decyl-3-methylimidazolium chloride in aqueous solutions.

Inorganic salts usually influence water structure affecting the hydration of the molecules which lead to a salting-in or a salting-out effect of hydrophobic compounds. Specific conductivity and isothermal titration calorimetry have been used to study the effect of inorganic salts on aggregation of the cationic surfactant 1-decyl-3-methylimidazolium chloride in aqueous solutions. The effect of the concentration, the nature of the anion and temperature on micelle formation were studied. A decreasing critical micelle concentration (CMC) due to the weakening electrostatic repulsion between the headgroups was observed. The salts used in this investigation decreased the CMC and degree of micelle ionization in the order of Cl(-)

1-methyl-3-octylimidazolium chloride--sorption and primary biodegradation analysis in activated sewage sludge.

Ionic liquids (ILs) are known to be non-volatile and thus to have low potential for atmospheric contamination or intoxication of humans by inhalation. However ILs have the potential to contaminate soil and water as they might be water soluble and can be sorbed onto solids. The investigation of possible natural ways of reducing the concentration of ILs in the environment is of high importance, especially because the requirement for biodegradable chemicals increases, together with pressure for reduction of incineration and landfill waste. It was found that the upper concentration threshold for primary biodegradation of 1-methyl-3-octylimidazolium chloride is 0.2 mM. At higher concentrations the dehydrogenase activity of the cells dropped markedly, indicating that the IL inhibits cell activity. This concentration is in good agreement with the minimal inhibitory concentration of the same compound found for a series of bacteria and fungi by this research group. The sorption of 1-methyl-3-octylimidazolium chloride was found to be significant, and the sorption coefficient was determined to be 98.2 L kg(-1).