Acid-like Compounds Research Articles

The interplay of Brown carbon (BrC) surrogates and copper: Implications for the oxidative potential of ambient particles

Atmospheric particulate matter (PM) poses adverse effects on human via producing reactive oxygen species (ROS). Oxidative potential (OP, ability to generate ROS) can be induced by various chemicals in PM, while their interplay remains poorly characterized. Here, we systematically assessed influences of Cu2+ on OP of Brown carbon (BrC) (e.g., imidazoles) using dithiothreitol (DTT) assay. Results showed DTT consumption rate exhibited an initial rise and later decline (0.25 −0.56 µM/min) along with increase of BrC concentration (0.1 − 2 µM), while no general trend was observed for •OH formation. Although Cu2+ showed either antagonism or synergism with BrC against DTT consumption, Cu2+ displayed antagonism with most BrC against •OH generation. Fluorescence quenching experiments provided evidence of complexation between Cu2+ and water-soluble organic compounds (WSOCs, from ambient PM2.5), which was influenced by Cu2+ concentration. Further parallel factor analysis of spectra showed that polycarboxylate-type humic acid-like substances (complexation site number (n): 0.46, complexation equilibrium constant (k): 0.51) and fulvic acid-like compounds (n: 0.42, k: 0.62) were the main components in WSOCs that complexed with Cu2+. Our results suggest the interactions of BrC and copper play a crucial role in PM OP and highlight complexation in evaluation of PM OP.

Polystyrene microplastics enhanced the photo-degradation and -ammonification of algae-derived dissolved organic matters

Algae-derived organic matter (ADOM) is a key source of chromophoric dissolved organic matter (CDOM) in natural waters. When exposed to solar irradiation, ADOM undergoes gradual degradation and transformation. The escalating presence of microplastics (MPs) can act as a novel type of environmental photosensitizer, however its impacts on ADOM photodegradation remains largely unexplored. Thus, in this study, ADOM were extracted from four common algal species (Microcystis aeruginosa, Synechococcus sp., Chlorella pyrenoidosa and Scenedesmus obliquus) and exposed to UV irradiation with or without polystyrene (PS) MPs, namely ADOM+PS groups and ADOM groups, respectively. The results indicated that a more rapid degradation of amino acid-like substances (∼38 % vs. ∼22 %) and more ammonia products (1.86 vs. 1.21 mg L−1) were observed in the ADOM+PS groups compared to the ADOM groups after a five-day exposure. This enhanced photodegradation might be attributed to the production of environmentally persistent free radicals and reactive species during the photoaging of PS. Furthermore, PS-derived high electron transfer belt activity of ADOM led to the production of highly aromatic and humified products. These humic-like products could potentially accelerate the degradation of amino acid-like compounds by exciting the generation of excited triplet CDOM. This study underscores the role of MPs as environmental photosensitizers in promoting ADOM degradation and ammonia generation, providing insights on the transformation of ADOM mediated by emerging pollutants and its impact on aquatic carbon and nitrogen cycles.

S-containing molecular markers of dissolved organic carbon attributing to riverine dissolved methane production across different land uses

The emission of methane (CH4) from streams and rivers contributes significantly to its global inventory. The production of CH4 is traditionally considered as a strictly anaerobic process. Recent investigations observed a “CH4 paradox” in oxic waters, suggesting the occurrence of oxic methane production (OMP). Human activities promoted dissolved organic carbon (DOC) in streams and rivers, providing significant substrates for CH4 production. However, the underlying DOC molecular markers of CH4 production in river systems are not well known. The identification of these markers will help to reveal the mechanism of methanogenesis. Here, Fourier transform ion cyclotron mass spectrometry and other high-quality DOC characterization, ecosystem metabolism, and in-situ net CH4 production rate were employed to investigate molecular markers attributing to riverine dissolved CH4 production across different land uses. We show that endogenous CH4 production supports CH4 oversaturation and positively correlates with DOC concentrations and gross primary production. Furthermore, sulfur (S)-containing molecules, particularly S-aliphatics and S-peptides, and fatty acid-like compounds (e.g., acetate homologs) are characterized as markers of water-column aerobic and anaerobic CH4 production. Watershed characterization, including riverine discharge, allochthonous DOC input, turnover, as well as autochthonous DOC, affects the CH4 production. Our study helps to understand riverine aerobic or anaerobic CH4 production relating to DOC molecular characteristics across different land uses.

Landfill leachate treatment using sequential natural zeolite adsorption and peroxymonosulfate activated by UV/Fe2+ system: Effects of main operating parameters and application of fluorescence EEM to monitor organic matters’ transformation

The significant increase in global Landfill Leachate is a pressing challenge directly linked to the growing global population. Among the strategies for landfill leachate treatment, advanced oxidation processes using sulfate radical (SR-AOP) have gained considerable interest, despite the challenge of nitrate generation during ammonia oxidation. This study introduces a sequential treatment method that combines adsorption and a UV/PMS/Fe2+ system to assess its impact on COD (Chemical Oxygen Demand) and ammonia removal efficiencies.The results show that the sequential process achieves optimal COD and ammonia removal rates of 88 % and 88.3 % respectively. The increase in UV254 absorbance removal during the adsorption phase indicates the removal of UV quenching substances (UVQS), supporting the effectiveness of using adsorption as a pretreatment for the UV-assisted systems (UV/PMS/Fe2+). Additionally, analysis using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) reveals that the adsorption treatment before the SR-AOP process not only enhances COD and ammonia removal efficiencies, but also eliminates heavy metals such as vanadium (V), titanium (Ti), zinc (Zn), and aluminum (Al) present in leachate.Moreover, the higher BOD/COD ratio suggests improved biodegradability of the effluent. When compared to other systems at optimal conditions, the sequential adsorption and UV/PMS/Fe2+ systems demonstrate superior performance, focusing on removing refractory matter and reducing ammonia content, especially effective at a pH level of 7.25. Analysis using Excitation-Emission Matrix (EEM) shows a shift from primary peaks in raw leachate spectra associated with humic and fulvic acid-like compounds to lower-intensity peaks from fulvic-like small molecule materials in the treated effluent.

Colloidal fraction on pomelo peel-derived biochar plays a dual role as electron shuttle and adsorbent in controlling arsenic transformation in anoxic paddy soil

Arsenic release and reduction in anoxic environments can be mitigated or facilitated by biochar amendment. However, the key fractions in biochars and how they control arsenic transformation remain poorly understood. In this study, a biochar produced from pomelo peel was rich in colloids and was used to evaluate the roles of the colloidal and residual fractions of biochar in arsenic transformation in anoxic paddy soil. Bulk biochar showed a markedly higher maximum adsorption capacity for As(III) at 1732 mg/kg than for As(V) at 75.7 mg/kg, mainly because of the colloidal fraction on the surface. When compared with the control and treatments with the colloidal/residual fraction, the addition of bulk biochar facilitated As(V) reduction and release in the soil during days 0–12, but decreased the dissolved As(III) concentration during days 12–20. The colloidal fraction revealed significantly higher electron donating capacity (8.26 μmole−/g) than that of bulk biochar (0.88 μmole−/g) and residual fraction (0.65 μmole−/g), acting as electron shuttle to promote As(V) reduction. Because the colloidal fraction was rich in aliphatic carbon, fulvic acid-like compounds, potassium, and calcium, it favored As(III) adsorption when more As(III) was released, probably via organic-cation-As(III) complexation. These findings provide deeper insight into the role of the colloidal fraction of biochar in controlling anaerobic arsenic transformation, which will be helpful for the practical application of biochar in arsenic-contaminated environments.

Understanding microplastic aging driven by photosensitization of algal extracellular polymeric substances

The aging of microplastics (MPs) is extremely influenced by photochemically-produced reactive intermediates (PPRIs), which are mediated by natural photosensitive substances. Algal extracellular polymeric substances (EPS) can produce PPRIs when exposed to sunlight. Nonetheless, the specific role of EPS in the aging process of MPs remains unclear. This work systematically explored the aging process of polystyrene (PS) MPs in the EPS secreted by Chlorella vulgaris under simulated sunlight irradiation. The results revealed that the existence of EPS accelerated the degradation of PS MPs into particles with sizes less than 1 µm, while also facilitating the formation of hydroxy groups on the surface. The release rate of dissolved organic matter (DOM) from PS MPs was elevated from 0.120 mg·L-1·day-1 to 0.577 mg·L-1·day-1. The primary factor contributing to the elevated levels of DOM was humic acid-like compounds generated through the breakdown of PS. EPS accelerated the aging process of PS MPs by primarily mediating the formation of triplet excited states (3EPS*), singlet oxygen (1O2), and superoxide radicals (O2∙-), resulting in indirect degradation. 3EPS* was found to have the most substantial impact. This study makes a significant contribution to advance understanding of the environmental fate of MPs in aquatic environments impacted by algal blooms.

Membrane fouling in engineering nanofiltration process for drinking water treatment: The spatial and chemical aspects

Nanofiltration (NF) has become an established process for advanced treatment of drinking water, while membrane fouling remains as the main issue slowing the widespread application of the process. In this study, the key foulants were identified, and their spatial distribution and potential interactions were investigated based on a two-stage NF engineering project for municipal drinking water treatment. Over half a year of operation showed that the membrane fouling was mostly chemically reversible. Characterizations of the cleaning waste revealed that inorganic fouling dominated at both stages, which was mainly caused by the deposition of Al, Ca, and Si. While the overall fouling was much more severe at Stage 2, the organic fouling was the reverse. Autopsy of one full-size membrane element from each stage indicated that in addition to Al, P and humic acid-like compounds were abundant in the fouling layer for both stages despite the spatial differences. The spatial distribution of foulants was influenced by both concentration effects and presence of feed channel spacers. For the free membrane area, inorganic foulants and humic acid-like compounds had higher contents at Stage 2 than Stage 1. While for the membrane area contacting with spacers, Al and P at Stage 1 were 0.74 and 1.51 times higher than those at Stage 2, respectively. Moreover, statistical analysis, complexation experiments and engineering operation strongly supported that the residual Al and natural organic matter (NOM) were key foulants for the NF process, mainly by forming Al-NOM complexes. Besides the Al-NOM complexes, condensed phosphate, primarily sourced from the dosed phosphate-containing antiscalants, might also co-precipitate with Al or Al-NOM complexes.

Nanoplastics removal from spiked laundry wastewater using electro-peroxidation process

Microplastics and nanoplastics (NPs) in laundry wastewater (LWW) are major sources of plastic particles in wastewater treatment plants. Unlike microplastics, almost no information exists in the literature on the degradation of NPs in LWW. In this work, the degradation of NPs in commercial LWW by the electro-peroxidation process is investigated. The obtained results demonstrated that already existing ions in LWW such as Cl− contribute to faster degradation of NPs and a complete removal could be obtained as fast as 40 min. In addition, three-dimensional excitation and emission matrix fluorescence analysis was performed, which revealed humic acid-like, aromatic proteins-like, and fulvic acid-like compounds could be oxidized after 20, 40, and 60 min of treatment respectively. The effects of operating parameters on the process performance were then examined by response surface methodology (RSM) models. The results showed that initial TOC concentration was the most important parameter influencing negatively the percentage of NP degradation. Afterward, optimization of the process revealed that the energy consumption could be minimized at 31.2 mA/cm2, 0.025 mol/L [Na2SO4], and 52 min treatment time for 52.2 mg/L initial TOC. Finally, analysis of treated LWW showed no toxicity on Daphnia magna. This study showed that the electro-peroxidation process can completely degrade NPs in LWW without any remaining toxic compounds.

A novel fungal-algal coupling system for slaughterhouse wastewater treatment and lipid production

In this study, a novel fungal-algal coupling system was established for slaughterhouse wastewater treatment with Chlorella sp. DT025 and a new fungus, Penicillium sp. AHP141. With the optimization of cultivation conditions for the fungal-algal coupling system, the harvest efficiency of Chlorella sp. DT025 reached 99.79%. The mechanism of microalgae harvest of the fungal-algal system was revealed to be related to the morphological characteristics, surface charge, and the secretion of humic acid-like compounds and tryptophan on the surface of the fungi cells. For the original slaughterhouse wastewater treatment, the fungal-algal coupling system had a better removal efficiency of COD, TN, and TP than both monoculture systems. In the high-concentration artificial slaughterhouse wastewater, COD removal of the fungal-algal system reached more than 5350 mg/L. The lipid production of the fungal-algal coupling system in the high-concentration artificial slaughterhouse wastewater treatment was improved by 343.33% to 1.33 g/L compared to the microalgae monoculture treatment.

Gut microbiota metabolites mediate the interplay between childhood maltreatment and psychopathology in patients with eating disorders

Eating disorders (EDs) are syndromes with a multifactorial etiopathogenesis, involving childhood traumatic experiences, as well as biological factors. Human microbiome has been hypothesised to play a fundamental role, impacting on emotion regulation, as well as with eating behaviours through its metabolites such as short chain fatty acids (SCFAs). The present study investigated the interactions between psychopathology of EDs, the gut microbiome and SCFAs resulting from bacterial community metabolic activities in a population of 47 patients with Anorexia Nervosa, Bulimia Nervosa, and Binge Eating Disorder and in healthy controls (HCs). Bacterial gut microbiota composition differences were found between subjects with EDs and HCs, especially in association with different pathological behaviours (binge-purge vs restricting). A mediation model of early trauma and ED-specific psychopathology linked reduction of microbial diversity to a typical microbiota-derived metabolite such as butyric acid. A possible interpretation for this model might be that childhood trauma represents a risk factor for gut dysbiosis and for a stable modification of mechanisms responsible for SCFAs production, and that this dysfunctional community is inherited in the passage from childhood to adulthood. These findings might open the way to novel interventions of butyric acid-like compounds as well as faecal transplant.

Influences of Anthropogenic Pollution on the Dynamics of Sedimentary Fulvic Acid Fractions as Revealed via Spectroscopic Techniques Combined with Two-Dimensional Correlation Spectroscopy

To identify the influences of anthropogenic activities on the composition, spatial distribution, sources, and transformation mechanism of sedimentary fulvic acid (FA) fractions from different reaches of an urban river were tracked via excitation-emission matrix (EEM) fluorescence spectroscopy with parallel factor (PARAFAC) analysis and two-dimensional correlation spectroscopy (2D-COS). Sediment samples were collected from Baitapu River (BR) along gradients with human activities (e.g., rural, town, and urban sections) in Shenyang, northeast China, from which FA fractions were extracted and then determined via EEM fluorescence spectroscopy. According to optical indices, the autochthonous sources of sedimentary FA fractions in BR were more significant than the terrestrial sources. Among the sections, the contribution from autochthonous sources decreased in the following order: Rural > Urban > Town. Six components of sedimentary FA fractions were identified via EEM–PARAFAC: C1 comprised tryptophan-like (TRL) compounds; C2 was associated with microbial humic-like (MHL) compounds; C3, C4, and C5 were associated with FA-like (FAL) compounds; and C6 comprised humic acid-like (HAL) compounds. The proportion of sedimentary FA fractions decreased in the following order: MHL + FAL + HAL (humus, 77.37–88.90%) > TRL (protein, 11.10–22.63%) for the three sections, showing that humus dominated. The town section exhibited the highest sedimentary FA fractions (5328.87 ± 1315.82 Raman unit [R.U.]), followed by the urban (4146.49 ± 535.75 R.U.) and rural (2510.56 ± 611.00 R.U.) sections. Three pollution sources were determined via principal component analysis (i.e., the dominant industrial source, domestic wastewater, and agricultural effluent). Additionally, the results from 2D-COS revealed that sedimentary FA fractions tended to stabilize as the protein-like component was transformed into the HAL component. Furthermore, we used the structural equation model to validate the critical environmental variables affecting the FA fraction transformation. The results can elucidate the influences of human activities on the dynamics of sedimentary FA fractions in urban rivers.

Structure of the humic acid-like compounds of raw and hydrothermally treated sewage sludge

Humic acids are of great interest in many fields; however, they are inhibitors of fermentative processes applied to hydrothermally treated sewage sludge. Hence, the structure and composition of soluble and bound humic acid-like fractions from raw and hydrothermally treated sewage sludge were studied. Lipid, polysaccharide, protein and aromatic fractions were identified, as well as a high nitrogen content (7–10 %) and low solubility in alkaline media. Thus, they do not strictly meet the chemical definition of ‘humic acids’. The soluble humic acid-like compounds had more aromatic and less protein content. Thermal hydrolysis of sewage sludge increased their aromaticity to the detriment of protein and polysaccharide fractions, while wet oxidation caused an increase in all structural fractions. Regarding the bound compounds, lipid, polysaccharide and aromatic fractions increased markedly during both treatments, although oxygen produced higher degradation of the protein fraction and, from 1 h, the partial degradation of aromatic compounds and an increase in the C/N atomic ratio (from 5.0 to 18.7 after 2 h). Therefore, hydrothermal treatments have a positive impact on the hydrolysate biodegradability due to the organic matter solubilisation, but also a negative impact linked to the higher solubilisation of the humic acid-like compounds and their structural changes.

Fulvic acid enhanced peroxymonosulfate activation over Co–Fe binary metals for efficient degradation of emerging bisphenols

Bisphenol F (BPF) and bisphenol S (BPS) are emerging bisphenols, which have become the main substitutes for bisphenol A (BPA) in industrial production and are also considered as new environmental pollution challenges. Thus, the necessity for an effective approach to remove BPF and BPS is essential. In this study, fulvic acid (FA) was used to modify Co–Fe binary metals (CFO) for peroxymonosulfate (PMS) activation. The characterization results demonstrated that CFO changed significantly in morphology after compounding with FA, with smaller particle size and 5.6 times larger specific surface area, greatly increasing the active sites of catalyst; Moreover, humic acid-like compounds increased the surface functional groups of CFO, especially phenolic hydroxyl, which could effectively prolong the PMS activation. The concentration of all reactive species, such as SO4•−, •OH, O2•−, and 1O2 increased in FA@CFO/PMS system. As a result, the degradation efficiency of CFO for both BPF and BPS was significantly improved after compounding FA, which also had a wide range of pH applications. The degradation pathways of both BPF and BPS were proposed based on liquid chromatography-mass spectrometry (LC-MS) analysis and the density functional theory (DFT) calculations. Our findings are expected to provide new strategies and methods for remediation of environmental pollution caused by emerging bisphenols.

Targeting Cellular Retinoic Acid Binding Protein 1 with Retinoic Acid-like Compounds to Mitigate Motor Neuron Degeneration.

All-trans-retinoic Acid (atRA) is the principal active metabolite of Vitamin A, essential for various biological processes. The activities of atRA are mediated by nuclear RA receptors (RARs) to alter gene expression (canonical activities) or by cellular retinoic acid binding protein 1 (CRABP1) to rapidly (minutes) modulate cytosolic kinase signaling, including calcium calmodulin-activated kinase 2 (CaMKII) (non-canonical activities). Clinically, atRA-like compounds have been extensively studied for therapeutic applications; however, RAR-mediated toxicity severely hindered the progress. It is highly desirable to identify CRABP1-binding ligands that lack RAR activity. Studies of CRABP1 knockout (CKO) mice revealed CRABP1 to be a new therapeutic target, especially for motor neuron (MN) degenerative diseases where CaMKII signaling in MN is critical. This study reports a P19-MN differentiation system, enabling studies of CRABP1 ligands in various stages of MN differentiation, and identifies a new CRABP1-binding ligand C32. Using the P19-MN differentiation system, the study establishes C32 and previously reported C4 as CRABP1 ligands that can modulate CaMKII activation in the P19-MN differentiation process. Further, in committed MN cells, elevating CRABP1 reduces excitotoxicity-triggered MN death, supporting a protective role for CRABP1 signaling in MN survival. C32 and C4 CRABP1 ligands were also protective against excitotoxicity-triggered MN death. The results provide insight into the potential of signaling pathway-selective, CRABP1-binding, atRA-like ligands in mitigating MN degenerative diseases.

Study of the Humification Process and Humic Acid-like Structure Characteristics of Kitchen Waste with the Addition of Biochar

The majority of the studies on humification culture presently use livestock and poultry manure as the primary raw material. There is significantly less research on the changes and structural characteristics of humic acid-like compounds (HAL) formed by humification using real food waste as the raw material. This paper aims to study the changes in humic components and the structure of HAL in the humification process through the addition of biochar to pre-meal waste and post-meal swill as the primary raw materials. Kitchen waste + corn straw (KC) and kitchen waste + corn straw + biochar carbon (KCBr) were humified for 24 days, respectively, using the indoor static composting method, where the samples were collected at days 0, 12, and 24 of incubation. The HAL were analyzed using elemental analysis, infrared spectroscopy, and differential thermal techniques. The results demonstrated that KCBr first entered the high-temperature phase, which lasted for 12 days above 50 °C. The total organic carbon (TOC) demonstrated a decreasing trend in both treatments, while the total nitrogen (TN) demonstrated an upward trend. The HAL and fulvic acid-like (FAL) contents of the two treatments increased and decreased with an increase in the incubation time, respectively. The relative HAL content and humification index (PQ%) of KCBr and KC at the end of humification were 22.76% and 19.69% and 74.30%, and 73.11%, respectively. In terms of the HAL structure, the KCBr treatment demonstrated lowered condensation, reduced oxidation, decreased aliphatic, enhanced aromatization, and increased thermal stability of HAL compared with the KC treatment.

Gas Chromatography Fingerprint of Martian Amino Acids before Analysis of Return Samples

Within the perspective of the current and future space missions, the detection and separation of building blocks such as amino acids are important subjects which are becoming fundamental in the search for the origin of life and traces of life in the solar system. In this work, we have developed and optimized a strategy adapted to space experimentation to detect the presence of amino acid-like compounds using gas chromatography coupled to mass spectrometry (GC-MS). Selected derivatization methods meet the instrument design constraints imposed on in situ extraterrestrial experiments. Coupled to a fast selective extraction, GC analysis would be highly efficient for the detection of organic materials. In the future, the corresponding GC-MS TIC could facilitate simple and fast selection of sediments/dust samples onboard GC-MS-equipped rovers for sample return-to-Earth missions.

Investigation of some endophytic fungi from five medicinal plants with growth promoting ability on maize (Zea mays L.).

This study aimed to identify endophytic fungi from Anthemis altissima, Matricaria parthenium, Cichorium intybus, Achillea millefolium, and A. filipendulina with plant-promoting ability on the ZP684 maize hybrid-cultivar. Plants were collected from northeast-Iran and endophytic fungi were isolated and identified using partial large subunit nrDNA, internal transcribed spacer, translation elongation factor, and β-tubulin genetic markers. Endophytic fungi that improved seed germination were studied under greenhouse conditions. Ninety-seven endophytic fungi were identified. Preussia africana, Bjerkandera adusta, Schizophyllum commune, Alternaria embellisia, Trichaptum biforme, Septoria malagutii, A. consortiale, Verticillium dahliae, Fusarium avenacearum, and Trametes versicolor significantly improved seed-germination. Alternaria consortiale produced the highest level of indole-3-acetic acid-like compounds and maize growth-promoting. Plant fungal colonization frequency increased with orthometric height. Sampling location Chahar Bagh at 2230 m contained the most endophytic fungi. Fusarium and Alternaria were the most frequently isolated endophytic genera. Therefore, medicinal plants are potential hosts for endophytic fungi that may be suitable biofertilizer agents in agriculture. This study helps to better understand the ecosystem functions by investigating of endophytic fungi distribution under different ecological conditions. Finding effective isolates among these microorganisms with a suitable plant-promoting ability on crops may help to reduce the use of chemical fertilizers in an agroecosystem.

Use of fulvic acid-like compounds from pulp-derived black liquor for enhancing the selenium content of peanut buds

BackgroundCleaner production involving the extraction of useful material from the black liquor by-product of straw pulp would be environmentally beneficial and would permit increased wastewater usage.ResultsThe fulvic-acid-like components of pulp black liquor (PFA) with molecular weights below 10 kDa were isolated. The chemical and physiological characteristics of PFAs were investigated. Selenite can enhance the selenium nutrition level of crops, but excessive selenite may be toxic to plant growth. In order to explore how to increase selenite tolerance and selenium accumulation in peanut, the effects of PFA on selenium-associated properties in peanut seedlings were examined by growing seedlings with sodium selenite (0, 5, 15, and 25 mg·L− 1 Na2SeO3, 15 mg·L− 1 Na2SeO3 solution containing 60 mg-C/L PFA, and 25 mg·L− 1 Na2SeO3 containing 60 mg-C/L PFA).ConclusionThe results showed that with 15 mg·L− 1 Na2SeO3, PFA significantly increased both the total and hypocotyl fresh weight of the seedlings but reduced the fresh weight of the root. PFA also effectively promoted the conversion of Se from inorganic to organic compounds in the root and hypocotyl, increased the soluble total sugar and soluble protein contents of the hypocotyl, and thus improved the edible quality and food safety of the selenium-enriched peanut buds. The results suggest that PFA can be used as an innovative bio-based substance for selenium-enriched sprout vegetable production.

Characterization of dissolved black carbon and its binding behaviors to ceftazidime and diclofenac pharmaceuticals: Employing the molecular weight fractionation

As the ubiquitous component of the aquatic environment, dissolved organic matter (DOM) readily bind with residual pharmaceutical contaminants (PCs) and influence their environmental behaviors. However, the binding mechanisms between dissolved black carbon (DBC), a vital part of the natural DOM pool, and PCs were poorly researched. In this study, the bulk DBC was divided into four fractions in molecular weight (MW) via an ultrafiltration system, and the properties of DBC and their binding interaction with two kinds of typical PCs (ceftazidime (CAZ) and diclofenac (DCF)) were explored concretely. The results showed that low MW component was the main contributor to bulk DBC, and the aromaticity increased with the increase of MW. The categories of chemical structures and fluorescent substances in different MW DBC were similar. Multispectral techniques showed that the oxygen-enriched compounds in DBC had the higher affinity to CAZ/DCF. The –NH–, –COOH, –NH2 groups in CAZ molecules appeared to form the hydrogen bond with DBC. Fluorescence quenching experiments were analyzed, and the binding mechanisms were specifically expounded from the thermodynamic perspective. The fluorophore of fulvic acid-like compounds (FA) were quenched by both static and dynamic quenching mechanisms, while only static quenching occurred for humic acid-like compounds (HA). For bulk DBC, the hydrogen bond and van der Waals force were the major forces in the HA-CAZ system, while the hydrophobic force made the primary contribution to the HA-DCF system, which might be ascribed to the higher hydrophobic nature of DCF. Notably, with the increase of HA MW, the main binding mode of HA-CAZ/DCF changed from hydrophobic force to hydrogen bond and van der Waals force gradually, which also directly proved that various noncovalent interactions co-driven the binding processes. Our findings are beneficial to better assess the fate of DBC and PCs and the corresponding complexes in the aquatic environment.

Spectroscopic characteristics and disinfection byproduct formation during UV-assisted photoelectrochemical degradation of humic acid

UV-assisted photoelectrochemical processes (UV/E) that produce reactive species are extensively used for degrading pollutants in water, such as natural organic matter (NOM). However, the consequence of the chlorinated disinfection byproducts (DBPs) from smaller compounds broken down is not clear in the UV/E. In this study, excitation-emission matrices (EEM) and parallel factor analysis (PARAFAC) were applied to determine the products formed during decomposition and the influence of UV/E processes on the formation of DBPs. In comparison with UV photochemical and electrochemical processes, the deterioration rate of NOM in the UV/E process rose by 68.45% and 54.47% in 70 min, while it increased up to 48.85% under the electrochemical process in 23 h. Not only does the reaction time affect the degradation, but the electrolyte concentration and current density also disturb it. The EEM peak locations were 275 nm/495 nm (Component 1), 275 nm/410 nm (Component 2), 230 nm/405 nm (Component 3), and <220 nm/290 nm (Component 4), which were considered to humic acids, hum-like compounds, fulvic acid-like compounds, and aromatic proteins, respectively. C1 and C2 were well relevant to dissolved organic carbon (DOC) and UV254 (r = 0.925–0.963, p < 0.01) and the formation of MCAA, DCAA, and TCAA were strongly interrelated with UV254 and DOC (r = −0.711 to −0.584). The generation of DBPs has a good correlation with C2 (r = – 0.673, p < 0.01). DBPs formation and calculated theoretical cytotoxicity were significantly suppressed by the UV/E process with a higher degradation of NOM. A similar amount of DBPs formation was obtained while 52.6% and 82.90% of the DOC was reduced under the electrochemical process and the UV/E process, indicating that a lower DBPs production and higher degradation efficiency in the UV/E process. It was supposed that the UV/E process could be an alternative for natural organic matter oxidation with properly controlled DBP formation.