Organic Contaminants In Aquatic Environment Research Articles

Versatile hybrid magnetic core silver-shell (Fe3O4@PEI@Ag) microspheres based SERS substrates for detection of organic dyes pollutant

In recent years, the development of highly sensitive and versatile substrates for Surface-Enhanced Raman Scattering (SERS) has become pivotal in environmental monitoring. This study introduces a hybrid SERS substrate designed to enhance the detection and discrimination of organic dyes in aqueous environments. In this report, we present silver shell magnetic core (Fe3O4@PEI@Ag) microspheres as a versatile SERS substrate for the detection and differentiation of organic dyes, specifically malachite green (MG), crystal violet (CV), Rhodamine 6G (R6G), and Safranin O (S.O), which are often overlooked water pollutants. The core-shell structure of Fe3O4@PEI@Ag microspheres have been synthesized via seed-mediated growth method. The microspheres, integrates a magnetic core of iron oxide (Fe3O4) through a polymeric layer of polyethyleneimine (PEI) with silver shell (Ag), are optimized to act as magnetic separator and show SERS activity. The SEM measurements confirm the spherical shape of grown nano-particles whereas magnetization experiments confirm the presence of magnetic cores as well non-magnetic layers coating in the end products. These microspheres with aluminium (Al) base combination demonstrate high SERS sensitivity with enhancement factor of 1 × 105, 5.6 × 106, 6.4 × 106, and 4.2 × 105 for MG, CV, R6G, and S.O respectively. The detection limits have been found in the range between 10–8–10–10 for all four dyes. A linear relationship between Raman intensity and concentrations of dyes make it suitable for quantitative analysis of unknown concentration. Principal component analysis (PCA), a multivariate analysis has been adopted to discrimination of dyes. These dyes have been effectively detected quantitative in tap water to express substrate's suitability in real-world application. Their dual functionality, as SERS-active substrate and as magnetic separator, enhances their utility in real-world applications such as organic contaminants in aquatic environments.

Upcycling polystyrene microplastics to Fe/Mo-doped sponge-carbon: Mo5+ enhanced electron transfer for boosting Fenton-like performance

The rate-limiting steps of promoting the conversion of Fe3+ to Fe2+ in Fenton-like systems are crucial for achieving efficient degradation of organic contaminants in aquatic environments. Herein, a novel magnetic Fe/Mo bimetallic doped sponge carbon (Fe/Mo-N-C) derived from polystyrene microplastics was successfully synthesized and the presence of metastable Mo5+ remarkably synergized the electron transfer of Fe2+ in internal microenvironment. In the Fe/Mo-N-C activating peroxymonosulfate (PMS) system, Mo5+ boosted the oxidation of Fe2+, and the conversion of Mo4+/Mo6+ accelerated the restoration of Fe2+ from Fe3+, resulting in nearly 100 % of 17α-ethinylestradiol (EE2) degradation with the kinetic rate constant of 0.343 min−1, which was 8.1 times faster than that of Fe-N-C. Moreover, Fe/Mo-N-C possessed excellent resistance to interference from various coexisting anions (especially chloride, sulfate, and nitrate ions up to 500 mM), natural organic matter, nano-plastics, and different water matrices. Density functional theory analysis demonstrated that Mo centers regulated the electron rearrangement of the Fe 3d orbital, enhancing the activation performance of Fe/Mo-N-C towards PMS. This study lays the groundwork for understanding the mechanism of metastable Mo, which holds significant importance for the up-recycling of polyethylene plastics and environmental remediation.

Interpreting the removal behaviours of aniline and 3,4-diaminotoluene on aromatic carbon-rich magnetic polymer: Statistical modelling, DFT quantitative calculations and new perspectives

The widespread presence of harmful and stubborn amine organic contaminants in aquatic environments motivated the exploration of efficient technologies for alleviating their serious environmental crisis. Herein, the recyclable magnetic Schiff base polymer (Fe3O4-TENE) with satisfactory and promising capacity in treating aniline and 3,4-diaminotoluene as representative amine organic contaminants was fabricated via a simple in-situ polymerization method, which combined the magnetic separability advantage of magnetic oxides with the abundant aromatic carbon content properties of Schiff base polymer. Multiple characterization methods verified the effectiveness of the in-situ polycondensation coating reaction and analyzed the physicochemical properties of Fe3O4-TENE. The Fe3O4-TENE possessed abundant homogeneous reaction sites and excellent regeneration performance, multiple diffusion driving forces and micro-mechanisms co-participated in the removal reaction. The adsorption pathway, underlying reaction mechanism and the most probable bonding system were identified based on the statistical modelling and DFT quantitative calculations. Especially, the visible electrostatic potential molecular and molecular orbitals verified the π-π interaction and electrostatic forces greatly contributed to the removal reaction. The Driving forces – Challenges – Breakthrough – Application framework was proposed for comprehensively assessing the possible environmental application of Fe3O4-TENE. Overall, this work not only provides important insights into the utilization of magnetic polymer composite to alleviate ecological and environmental risks caused by amine organic pollutants, but also contributes to an in-depth excavation of the bonding types and removal mechanisms from both micro and macro perspectives.

Passive sampler housing and sorbent type determine aquatic micropollutant adsorption and subsequent bioassay responses

The combination of integrative passive sampling and bioassays is a promising approach for monitoring the toxicity of polar organic contaminants in aquatic environments. However, the design of integrative passive samplers can affect the accumulation of compounds and therewith the bioassay responses. The present study aimed to determine the effects of sampler housing and sorbent type on the number of chemical features accumulated in polar passive samplers and the subsequent bioassay responses to extracts of these samplers. To this end, four integrative passive sampler configurations, resulting from the combination of polar organic chemical integrative sampler (POCIS) and Speedisk housings with hydrophilic-lipophilic balance and hydrophilic divinylbenzene sorbents, were simultaneously exposed at reference and contaminated surface water locations. The passive sampler extracts were subjected to chemical non-target screening and a battery of five bioassays. Extracts from POCIS contained a higher number of chemical features and caused higher bioassay responses in 91% of cases, while the two sorbents accumulated similar numbers of features and caused equally frequent but different bioassay responses. Hence, the passive sampler design critically affected the number of accumulated polar organic contaminants as well as their toxicity, highlighting the importance of passive sampler design for effect-based water quality assessment.

Structural investigation, photoluminescence, and antibacterial properties of purified palygorskite impregnated with α-Ag2WO4 microcrystals

The presence of organic contaminants in aquatic environments, such as antibiotics, induces the proliferation of resistant pathogens, giving rise to the need to develop new materials with antimicrobial action. Therefore, in this work, we report new results to purified Palygorskite (P-Pal) clay with a surface impregnated with alpha-silver tungstate (α-Ag2WO4) microcrystals abbreviated as AWO, and its structural, photoluminescence (PL) and antibacterial investigation for inactivation of gram-negative (Escherichia coli) and gram-positive (Staphylococcus aureus) bacterial strains at concentrations of P-Pal/x%/AWO from x = 4–32%. X-ray diffraction patterns, Rietveld refinement data, and Fourier transform infrared spectroscopy confirmed that the P-Pal is composed of two crystal phases (Mg2.074Al1.026) (Si4O10.48)2(OH)2(H2O)10.68 with an orthorhombic structure and α-SiO2 with a rhombohedral structure; already the AWO microcrystals are single-phase with an orthorhombic structure and their vibrational modes. Ultraviolet–visible spectroscopy shows an increase in the Egap values for mixed systems compared to the isolated materials, indicating a synergistic interaction between the energy levels of both materials. Field emission scanning electron microscopy images display the presence of several elongated fibers and hexagonal crystals in the P-Pal clay and rod-like AWO microcrystals. In contrast, P-Pal clay/AWO microcrystals exhibit the presence of all three crystal shapes. Photoluminescence spectra show a high emission for the P-Pal clay/4% AWO microcrystals, indicating a better energy band gap synergistic. Finally, the microbiological tests show that as the proportion of AWO crystals on the P-Pal clay surface increases, there is a rise in antibacterial activity.

Synergistic effect on simultaneous treatment of Cr(VI) and chloramphenicol using a non-thermal plasma technology

Toxic organic and heavy metal contaminants commonly exist in industrial waste stream(s) and treatment is of great challenge. In this study, a dielectric barrier discharge (DBD) non-thermal plasma technology was employed for the simultaneous treatment of two important contaminants, chloramphenicol (CAP) and Cr(VI) in an aqueous solution through redox transformations. More than 70% of CAP and 20% of TOC were degraded in 60 min, while Cr(VI) was completely removed in 10 min. The hydroxyl radicals were the main active species for the degradation. Meanwhile, the consumption of hydroxyl radicals was beneficial to the reduction of Cr(VI). The synergistic effect was investigated between CAP degradation and Cr(VI) reduction. The reduction of Cr(VI) would be enhanced in the presence of CAP with a low concentration and could be inhibited under a high concentration, because part of hydroxyl radicals could be consumed by the low-concentration CAP and the obtained intermediates with a higher kinetic rate. However, CAP with a high concentration could react with such reductive species as eaq− and •H, which could compete with Cr(VI) and inhibit the reduction. In addition, the presence of Cr(VI) enhanced the degradation and mineralization of CAP; the study of obtained intermediates indicated that the presence of Cr(VI) changed the degradation path of CAP as Cr(VI) would react with reductive species, enhance the generation of hydroxyl radicals, and cause more hydroxylation reactions. Moreover, the mechanism for the simultaneous redox transformations of CAP and Cr(VI) was illustrated. This study indicates that the DBD non-thermal plasma technology can be one of better solutions for simultaneous elimination of heavy metal and organic contaminants in aquatic environments.

Cerium/sulfur co-doped spinel iron-cobalt oxide@carbon interconnected mesh networks as superior peroxymonosulfate activator for tetracycline degradation

Transition metal spinel oxides have potential applications in activating peroxymonosulfate (PMS) to generate reactive substances for degrading organics in polluted water. However, many catalytic materials have low efficiency, indicating the need for advancements in material design. In this study, we present the one-step fabrication of Ce, S-codoped spinel iron-cobalt oxide@carbon (Ce-FeCo2O4@SxC) with interconnected mesh networks for efficient PMS activation in degrading tetracycline hydrochloride (TCH). Among the Ce-FeCo2O4@SxC samples, Ce-FeCo2O4@S1.5C demonstrates the highest catalytic performance, achieving a TCH degradation efficiency of 97.2 % in 30 min. Moreover, the catalytic system also exhibits anti-interference abilities against various anions and shows universality in degrading organic pollutants. Characterization and experimental tests confirm the co-existence of radical (SO4•−, •OH and O2•−) and non-radical pathways (1O2 and direct electron transfer), with 1O2 identified as the primary reactive species. Three plausible pathways for TCH removal are proposed based on detected intermediate products. Toxicity evaluation reveals a significant reduction in the toxicity of the original TCH solution during the degradation process with the PMS activator. This study introduces a simple yet effective co-doping strategy to enhance the catalytic properties of spinel oxides for PMS activation in degrading organic contaminants in aquatic environments.

Occurrence and cycle of dissolved iron mediated by humic acids resulting in continuous natural photodegradation of 17α-ethinylestradiol

17α-ethinylestradiol (EE2), a synthetic endocrine-disrupting chemical, can degrade in natural waters where humic acids (HA) and dissolved iron (DFe) are present. The iron is mostly bound in Fe(III)-HA complexes, the formation process of Fe(III)-HA complexes and their effect on EE2 degradation were explored in laboratory experiments. The mechanism of ferrihydrite facilitated by HA was explored with results indicating that HA facilitated the dissolution of ferrihydrite and the generation of Fe(III)-HA complexes with the stable chemical bonds such as C-O, CO in neutral, alkaline media with a suitable Fe/C ratio. 1O2, •OH, and 3HA* were all found to be important in the photodegradation of EE2 mediated by Fe(III)-HA complexes. Fe(III)-HA complexes could produce Fe(II) and hydrogen peroxide (H2O2) to create conditions suitable for photo-Fenton reactions at neutral pH. HA helped to maintain higher dissolved iron concentrations and alter the Fe(III)/Fe(II) cycling. The natural EE2 photodegradation pathway elucidated here provides a theoretical foundation for investigating the natural transformation of other trace organic contaminants in aquatic environments.

Biodegradation of trace sulfonamide antibiotics accelerated by substrates across oxic to anoxic conditions during column infiltration experiments

Frequent occurrence of trace organic contaminants in aquatic environments, such as sulfonamide antibiotics in rivers receiving reclaimed water, is concerning. Natural attenuation by soil and sediment is increasingly relied upon. In the case of riverbank filtration for water purification, the reliability of antibiotic attenuation has been called into question due to incomplete understanding of their degradation processes. This study investigated influence of substrates and redox evolution along infiltration path on biotransformation of sulfonamides. Eight sand columns (length: 28 cm) with a riverbed sediment layer at 3–8 cm were fed by groundwater-sourced tap water spiked with 1 μg/L of sulfadiazine (SDZ), sulfamethazine (SMZ), and sulfamethoxazole (SMX) each, with or without amendments of dissolved organic carbon (5 mg-C/L of 1:1 yeast and humics) or ammonium (5 mg-N/L). Two flow rates were tested over 120 days (0.5 mL/min and 0.1 mL/min). Iron-reducing conditions persisted in all columns for 27 days during the initial high flow period due to respiration of sediment organics, evolving to less reducing conditions until the subsequent low flow period to resume more reducing conditions. With surplus substrates, the spatial and temporal patterns of redox conditions differentiated among columns. The removal of SDZ and SMZ in effluents was usually low (15 ± 11%) even with carbon addition (14 ± 9%), increasing to 33 ± 23% with ammonium addition. By contrast, SMX removal was higher and more consistent among columns (46 ± 21%), with the maximum of 64 ± 9% under iron-reducing conditions. When sulfonamide removal was compared between columns for the same redox zones during infiltration, their enhancements were always associated with the availability of dissolved or particulate substrates, suggesting co-metabolism. Manipulation of the exposure time to optimal redox conditions with substrate amendments, rather than to simply prolong the overall residence time, is recommended for nature-based solutions to tackle target antibiotics.

Revealing the sorption mechanisms of carbamazepine on pristine and aged microplastics with extended DLVO theory

The co-occurrence of microplastics (MPs) and organic contaminants in aquatic environment can complexify their environmental fate via sorption interactions, especially when the properties of MPs can even vary due to the aging effect. Thus, quantitatively clarifying the sorption mechanisms is required to understand their environmental impacts. This study selected popularly occurring carbamazepine (CBZ) and four types of MPs as model systems, including polyethylene, polyvinyl chloride, polyethylene terephthalate and polystyrene in their pristine and aged forms, to investigate the sorption isotherms, kinetics, and desorption. The variation of MPs during the aging process were analyzed with scanning electron microscopy, contact angle, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. It was found that the aging process elevated the sorption capacity and intensified the desorption hysteresis of CBZ on MPs via increasing the surface roughness, decreasing the particle size, and altering the surficial chemistry of all MPs. The extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory was innovatively applied hereby to calculate the interfacial free energies and revealed that the hydrophobic interaction was significantly lessened after aging for all MPs with the slightly enhanced van der Waals interaction. Then the total interfacial free energies were dropped down for all MPs, which resulted in their declined specific sorption capacity. This work reveals the sorption mechanisms of CBZ on pristine and aged MPs with XDLVO and provides a useful reference to study the sorption of other neutral organics onto MPs.

Occurrence, distribution, and ecological risk assessment of pharmaceuticals and personal care products in the surface water of the middle and lower reaches of the Yellow River (Henan section)

Pharmaceuticals and personal care products (PPCPs) are commonly seen emerging organic contaminants in aquatic environments. The transects for the occurrence and distribution of 24 PPCPs along the middle and lower reaches of the Yellow River (Henan section) were investigated in this study. All 24 targeted compounds were detected in surface water, with concentrations in the range from not detected (ND) to 527.4ng/L. Among these PPCPs, caffeine is found to have the highest concentration and its detection frequency is 100%. The total PPCP concentration ranged from 136ng/L to 916ng/L (median, 319.5ng/L). Spatial analysis showed that the pollution level of PPCPs in the trunk stream was lower than that in most tributaries in the middle and lower reaches of the Yellow River (Henan section). The ecotoxicological risk assessment indicated that norfloxacin, azithromycin, estrone, and triclosan posed high risks to aquatic organisms (RQ > 1), roxithromycin and oxytetracycline imposed moderate risks (0.1≤ RQ < 1), and the tributary Jindi River had the highest mixed risk (MRQ = 222).

Wavelength-Dependent Photoreactivity of Root Exudates from Aquatic Plants under UV-LED Irradiation

Aquatic plants and their root exudates play important roles in the removal of trace organic contaminants in aquatic environments. However, the wavelength-dependent photogeneration of reactive species (RS) and photodegradation of organic contaminants by root exudates are poorly understood. This paper presents the first evidence that the photogeneration of 3DOM*, 1O2, and ·OH by root exudates varied under UV light-emitting diode (UV-LED) irradiation in the wavelength range of 265–400 nm. The quantum yields of 3DOM* and 1O2 of the four plants’ root exudates, including Scindapsus aureus, Pistia stratiotes, Eichhornia crassipes, and Nymphaea tetragona, reached the highest value at an irradiation wavelength of 275 nm and further decreased with increasing wavelength, while the ·OH quantum yield decreased gradually from 3.2–5.5 × 10–4 at 265 nm to 1.4–2.6 × 10–6 at 400 nm. The root exudate of Pistia stratiotes showed higher quantum yields of 3DOM* and 1O2 than that of the other three plants, while the highest ·OH quantum yield was observed in that of Eichhornia crassipes. The excitation wavelength affected the indirect degradation of organic contaminants by altering the photogeneration of RS in root exudate solutions. These findings highlight the wavelength-dependent photoreactivity of root exudates and improve the understanding of their photochemical processes in aquatic environments.

Sunlight-Induced Interfacial Electron Transfer of Ferrihydrite under Oxic Conditions: Mineral Transformation and Redox Active Species Production.

Fe(II)-catalyzed ferrihydrite transformation under anoxic conditions has been intensively studied, while such mechanisms are insufficient to be applied in oxic environments with depleted Fe(II). Here, we investigated expanded pathways of sunlight-driven ferrihydrite transformation in the presence of dissolved oxygen, without initial addition of dissolved Fe(II). We found that sunlight significantly facilitated the transformation of ferrihydrite to goethite compared to that under dark conditions. Redox active species (hole-electron pairs, reactive radicals, and Fe(II)) were produced from the ferrihydrite interface via the photoinduced electron transfer processes. Experiments with systematically varied wet chemistry conditions probed the relative contributions of three pathways for the production of hydroxyl radicals: (1) oxidation of water (5.0%); (2) reduction of dissolved oxygen (40.9%); and (3) photolysis of Fe(III)-hydroxyl complexes (54.1%). Results also showed superoxide radicals as the main oxidant for Fe(II) reoxidation under acidic conditions, thus promoting the ferrihydrite transformation. The presence of inorganic ions (chloride, sulfate, and nitrate) did not only affect the hydrolysis and precipitation of Fe(III) but also the generation of radicals via photoinduced charge transfer reactions. The involvement of redox active species and the accompanying mineral transformations would exert a profound effect on the fate of multivalent elements and organic contaminants in aquatic environments.

Joint effects of micro-sized polystyrene and chlorpyrifos on zebrafish based on multiple endpoints and gut microbial effects

Microplastics often co-occur with a variety of organic contaminants in aquatic environment and pose combined risks to aquatic wildlife. Here, we investigated joint effects of micro-sized polystyrene (mPS, 5 µm) and an organophosphate pesticide chlorpyrifos on zebrafish, using multiple endpoints at both fish individual and gut microbiota levels. It was revealed that mPS ingested by zebrafish accumulated in gut and liver, and caused oxidative stress, hyperactive swimming performance and histological damages in fish, and induced disorders and diversity alterations of the gut microbial community. More importantly, mPS exhibited considerable adsorption capacity against chlorpyrifos, and those adsorbing chlorpyrifos presented greater effects on fish individuals but no different effects on gut microbiota compared to single mPS exposure. Together with body residues of chlorpyrifos in zebrafish, it was proposed that the joint effects between mPS and chlorpyrifos were attributed to the chlorpyrifos released from mPS within zebrafish. The present results provided a comprehensive understanding of joint effects of mPS and contaminants co-occurring in the environment and emphasized the importance of considering the adsorbed chemicals in toxicological studies of microplastics.

Synthesis and Characterization of TiO2 – Ag-Cellulose Nanocomposite and evaluation of photo catalytic degradation efficiency for Congo Red

Photocatalytic degradation of toxic organic contaminants in aquatic environments is a cost-effective, efficient, and long-term solution for environmental restoration. The capacity to fine-tune the structures and compositions of photocatalysts is vital for optimizing photocatalytic decontamination processes, as is a deep understanding of the mechanisms that govern photocatalytic interfacial molecular changes. We created a ternary TiO2/Ag/cellulose nanocomposite particle by hydrothermal process that acts as a photocatalyst for the photodegradation of congo red CR dye into mineralized small moleculesThe morphology, size and crystalline structure of the TiO2 – Ag – Cellulose nanocomposite were investigated by scaning electron microscopy SEM, transmission electron microscopy (TEM) and X-ray diffraction XRD respectively. Surface functional groups were analyzed using FTIR analysis. Specific surface area of the composite was characterized by BET-BJH analysis and the elemental composition of the composite was study using EDX analysis. Interestingly, the prepared TiO2 – Ag – Cellulose nanocomposites showed high catalytic degradation activity for CR dye. The photocatalytic degradation of the azo dye was monitored spectrophotometrically, a high degradation efficiency 81,76 % under visible radiation were obtained for composite after 120 min of reaction compared to 30% for pure TiO2.

In-situ quantitative monitoring the organic contaminants uptake onto suspended microplastics in aquatic environments

Microplastics act as a source of organic contaminants in aquatic environments and thus affect their environmental fate and toxicity. Because of the weak and reversible interactions between microplastics and organic species, the organic coronas vary with their surrounding environments. Thus, in order to evaluate the possible environmental risks of microplastics, methods for evaluating the dynamic uptake of organic contaminants onto suspended microplastics in aquatic environments are greatly desired. In this work, a UV–vis spectroscopy-based approach was developed for in-situ monitoring organic contaminants uptake onto suspended microplastics after correcting the light scattering interference from microplastics suspensions and establishing the nonlinear relationship between concentration and light absorbance of organic species. The inverse adding-doubling method based on radiative transfer theory was adopted to correct the light scattering effect of suspensions. Then, the resulting mixed absorption spectra were decomposed to calculate the concentrations of the aqueous and adsorbed organic species simultaneously with a nonlinear calibration method. The uptake processes of bisphenol A and p-nitrophenol onto nylon 66 microparticles were monitored with this approach and confirmed by high-performance liquid chromatography analysis. The approach was validated by applying it to natural water samples, and the equilibrium adsorption capacity was found to be interfered mainly by the protein-like substances. This approach has high accuracy, good reproducibility, remarkable universality, and ease of handling, and also provides a potential tool for characterizing the corona formation process on suspended particles both in natural and artificial environments, such as eco-corona formation and engineering surface modification on nano/micro-particles.

Point or non-point source: Toxicity evaluation using m-POCIS and zebrafish embryos in municipal sewage treatment plants and urban waterways

Municipal sewage treatment plants (STPs) have been regarded as an important source of organic contaminants in aquatic environment. To assess the impact of STPs on occurrence and toxicity of STP-associated contaminants in receiving waterways, a novel passive sampler modified from polar organic chemical integrative sampler (m-POCIS) was deployed at the inlet and outlet of a STP and several upstream and downstream sites along a river receiving STP effluent in Guangzhou, China. Eighty-seven contaminants were analyzed in m-POCIS extracts, along with toxicity evaluation using zebrafish embryos. Polycyclic musks were the predominant contaminants in both STP and urban waterways, and antibiotics and current-use pesticides (e.g., neonicotinoids, fiproles) were also ubiquitous. The m-POCIS extracts from downstream sites caused significant deformity in embryos, yet the toxicity could not be explained by the measured contaminants, implying the presence of nontarget stressors. Sewage treatment process substantially reduced embryo deformity, chemical oxygen demand, and contamination levels of some contaminants; however, concentrations of neonicotinoids and fiproles increased after STP treatment, possibly due to the release of chemicals from perturbed sludge. Source identification showed that most of the contaminants found in urban waterways were originated from nonpoint runoff, while cosmetics factories and hospitals were likely point sources for musks and antibiotics, respectively. Although the observed embryo toxicity could not be well explained by target contaminants, the present study showed a promising future of using passive samplers to evaluate chemical occurrence and aquatic toxicity concurrently. Zebrafish embryo toxicity significantly decreased after sewage treatment, but higher toxicity was observed for downstream samples, demonstrating that urban runoff may produce detrimental effects to aquatic life, particularly in rainy season. These results highlight the relevance of monitoring nonpoint source pollution along with boosting municipal sewage treatment infrastructure.

Adsorption characteristics of tetracycline onto particulate polyethylene in dilute aqueous solutions

The presence of ultrafine plastics particles and its potential to concentrate and transport organic contaminants in aquatic environments have become a major concern in recent years. Specifically, the uptake of hazardous chemicals by plastics particles may affect the distribution and bioavailability of the chemicals. In this study, the adsorption of tetracycline (TC), an antibiotic frequently found in aquatic environments, on high-density polyethylene (PE) particles with the average size of 45 μm, was investigated. The PE particles were characterized for surface acidity for the first time. Results showed that pH controls the surface charge of PE particles. TC adsorption onto PE particles was rapid as expected following the pseudo-second-order rate law (r2 > 0.99). Polar forces in addition to specific chemical interactions, such as hydrogen bonding and hydrophophilicity controlled TC adsorption onto PE particles. Parameters, including pH, dissolved organic matter, ionic strength, major cations and anions affected TC adsorption onto PE micro-particles. Results indicated that PE particles can function as a carrier of antibiotics in the aquatic environment, which potentially imposes ecosystem and human health risks.

Enhanced phototransformation of atorvastatin by polystyrene microplastics: Critical role of aging

Reactive oxygen species (ROS) generated from light irradiation of microplastics (MPs) can potentially affect the environmental fate of organic contaminants when they coexist in the same environment. This study investigated the effect of polystyrene (PS) MPs with different aging degrees on the phototransformation of atorvastatin (ATV) under simulated sunlight. Results showed that the presence of PS MPs facilitated the phototransformation of ATV, and the degradation rate was linearly correlated with the aging degree (i.e., carbonyl index) of MPs. The enhanced effects mainly depended on the contents of oxygen-containing functional groups of PS MPs, which increased the absorption of light energy and the generation of ROS (e.g., singlet oxygen (1O2) and triplet-excited state PS (3PS*)). Quenching experiments indicated that 1O2 generated from photosensitization of PS was the major contributor to the increased phototransformation of ATV. Additionally, the role of 3PS* became more important in the photodegradation mediated by higher degree aged MPs because much more 1O2 was generated from the 3PS* . PS MPs also increased the types and yields of degradation products, especially for higher degree aged MPs, despite the low effect on leachate toxicity. The findings provide a novel insight into the critical role of MPs in the fate of organic contaminants in aquatic environments.

Sustainable wood-based nanotechnologies for photocatalytic degradation of organic contaminants in aquatic environment

Sustainable wood-based nanotechnologies for photocatalytic degradation of organic contaminants in aquatic environment