Chemical Model Systems Research Articles

Inhibitory action of antimicrobial peptides against the formation of carcinogenic and mutagenic heterocyclic amines in meat

Thermal processing of meat leads to the development of Maillard's reaction intermediates, and carcinogenic toxicants. For the first time, the effectiveness of three (HX-12A, HX-12B and HX-12C) antimicrobial peptides (AMPs) against the formation of heterocyclic amines (HAs) in chemical and meat model systems. The results showed that AMPs especially 12A and 12C have strong metal chelation potential (48 and 40% at 1 mg/ml) and antioxidant activity (35 and 25% at 1 mg/ml), respectively, which were endorsed by their secondary structure (FTIR analysis) in terms of high β-sheets (1628 cm−1 and 1672 cm−1) in those AMPs. UPLC-MS analysis revealed that 12A and 12C were the most capable AMPs in MeIQx and PhIP-producing chemical models, respectively, whereas 12B promoted the HAs formation even higher than control. In particular, 12C AMP significantly (P < 0.05) decreased the most abundant carcinogenic HAs (PhIP) up to 90% at 9 mg/100 g of fresh meat, whereas 12A inhibited up to 80% of mutagenic HAs at same level compared to control and 12B. Low Field Nuclear Magnetic Resonance (LF-NMR) test showed that inhibitory effect of 12A and 12C was mediated by means of retaining water (lower T22 and T23 relaxation time) inside the macromolecules. This favorable effect was also evidenced by significantly enhanced tryptophan fluorescent intensity. Finally, based on correlation and principle component analysis, the mechanism of action has been proposed. These outcomes recommend that 12A and 12C are potential AMPs for the attenuation of HAs in thermally processed meat-based products.

Acrylamide detection and reduction in meat products using organic acids, fruit extracts, and probiotics

Grilled foods are an important source of acrylamide, which has neurotoxic, genotoxic, and carcinogenic properties. The current study aims to evaluate the level of acrylamide in beef, chicken, and fish products, especially those requiring high cooking temperatures, using High Performance Liquid Chromatography (HPLC). Reduction of acrylamide by organic acids i.e., (citric acid, malic acid, tartaric acid, and lactic acid) and fruit extracts of lemon, apple, and grape has also been investigated. The results revealed that the highest mean acrylamide concentration was found in chicken products (grilled chicken) which recorded 8.32 μg/100 g, followed by beef products (beef grilled) with a concentration of 7.91 μg/100 g, and fish products (pan-fried fish burgers) which recorded 6.77 μg/100 g). Furthermore, the mixture of organic acid has the highest effect on reducing the level of acrylamide in a chemical model system. Moreover, the fruit extract mixture was more effective in reducing the percentage of acrylamide in the grilled chicken than organic acids mixture. Finally, the addition of fruit extract improved the sensory properties of grilled chickens. In sum, this study offers novel and promising natural strategies to decrease acrylamide in meat products toward further future application in meat industry to deliver safe food to consumers.

Effect and mechanism of polyphenols containing m-dihydroxyl structure on 2-amino-1-methyl-6-phenylimidazole [4, 5-b] pyridine (PhIP) formation in chemical models and roast pork patties

2-amino-1-methyl-6-phenylimidazole [4, 5-b] pyridine (PhIP) is a prevalent heterocyclic amine (HAA) found in heated processed meat. This study investigated the inhibitory impact of eight different types of polyphenols containing m-dihydroxyl structure on PhIP formation through a chemical model system. The structure-activity relationship and potential sites of action of polyphenols containing m-dihydroxyl structure were also analyzed. Then, the mechanism of inhibiting PhIP formation by kaempferol, naringenin and quercetin was speculated by UPLC-MS. Results showed that 8 kinds of polyphenols containing m-dihydroxyl structure had significant (P < 0.05) inhibition on the formation of PhIP in the chemical model system in a dose-dependent manner. In addition, PhIP was most significantly inhibited by naringenin at the same concentration, followed by kaempferol and quercetin (83.27%, 80.81% and 79.26%, respectively). UPLC-MS results speculated that kaempferol, naringenin, and quercetin formed a new admixture via an electrophilic aromatic substitution reaction with the intermediate product phenylacetaldehyde, preventing the formation of PhIP.

Inhibitory mechanism of carboxymethyl cellulose on advanced glycation end products in plant-based meat alternatives

Plant-based meat alternatives (PBMA) were detected with high advanced glycation end products (AGEs) levels in our previous study, threatening human health. In this study, carboxymethyl cellulose (CMC) exhibited excellent inhibitory effects on AGEs in both PBMA and chemical model systems. Moreover, the inhibitory effects were dependent on the levels of CMC addition. With 4% CMC addition, the contents of Nε-carboxymethy-l-lysine (CML) and Nε-carboxyethy-l-lysine (CEL) in PBMA decreased by 75% and 83%, respectively. Through comprehensive characterizations and high-resolution mass spectrometry analysis, three possible inhibitory pathways were proposed at the molecular level: CMC improved the thermal stability of soy protein isolates (SPI) via covalent bond; CMC occupied the amino reaction sites on SPI and competitively inhibited the reaction between SPI and glucose; CMC scavenged the intermediates of AGEs (i.e glyoxal and methylglyoxal). This research lays a theoretical foundation on the inhibition of AGEs in PBMA through the regulation of hydrocolloids.

Unraveling the relationships between processing conditions and PhIP formation in chemical model system and roast pork patty via principal component analysis

2-amino-1-methyl-6-phenylimidazole [4,5-b] pyridine (PhIP) is one of the higher levels of HAAs produced in protein foods during heating. The effects of heating temperature, time, and concentration of precursors on PhIP and related substances in the chemical model system and roast pork patty were studied using HPLC-Q-Orbitrap-HRMS and GC–MS. Results showed that the heating temperature, time, and concentration of four precursors significantly affected PhIP and its related substances (P < 0.05) in the chemical model system. Among them, PhIP production was greatest when heating at 200 min with 220 °C, and the concentrations of phenylalanine, creatinine, glucose, and creatine added were 10, 20, 20, and 20 mmol/L, respectively. Moreover, as the fat proportion of roast pork patties increased, PhIP and its intermediate-phenylacetaldehyde concentrations increased substantially (P < 0.05). PCA results showed that the samples of PhIP and related substances gradually dispersed as the temperature and time increased, and there were obvious effects among them.

Physics‐informed learning of chemical reactor systems using decoupling–coupling training framework

AbstractIt is known that physics‐informed learning become a new learning philosophy that has been applied in many scientific domains. However, this approach often struggles to achieve optimal performance in addressing the issue of multiphysics coupling. Here, for the first time, we extend this approach to modeling chemical reactor systems. We design a new decoupling–coupling training framework, which consists of decoupling pre‐training and multiphysics coupling training steps. With decoupling pre‐training, the complex physical domain is decomposed into subdomains of fluid flow, heat transfer, and mass transfer combined with reaction kinetics. Each subdomain is represented by a specialized neural network that can provide a coarse but reasonable distribution of network parameters for initializing the sub‐networks for the subsequent multiphysics coupling training. The capabilities of this approach, in comparison with the traditional CFD simulation, are demonstrated through an example of a plate reactor system with a heating cylinder.

Simultaneous Identification and Quantification of Phenylalanine, Glycine and Lysine amino acids and conjugated heterocyclic amines in Maillard chemical model system using RP-HPLC-DAD

In this study, we developed a simple reversed-phase high-performance liquid chromatography (RP-HPLC) methodology for simultaneous identification and quantification of three types of mix: (1) phenylalanine and PHIP; (2) glycine and MeIQx; (3) lysine and 4,8 DiMeIQx in Maillard chemical model systems. In addition, we investigated the effects of different conditions on decreasing amino acids and heterocyclic amines (HCA) formation in chemical model systems. The results show that the developed methods used to separate the proposed mixes gave a relative standard deviation (RSD)% of less than 2% of peak area and retention time, thus proving the robustness and high reproducibility of the proposed method. The relationship between concentration and peak areas is linear with high statistical significance (p&lt;0.001). The residual and slope of linear regression give a limit of detection LoD) and (LoQ) of phenylalanine and PHIP were (2.92- 0.029 ppm),(9.73- 0.098 ppm),respectively, which indicate the high sensitivity of the developed method. Moreover, the findings illustrate that a water ratio of 20% leads to a decrease in phenylalanine versus the largest amount of PHIP, and phenylalanine is the most active amino acid with a decreasing percentage up to 99%.

Remdesivir-Loaded Nanoliposomes Stabilized by Chitosan/Hyaluronic Acid Film with a Potential Application in the Treatment of Coronavirus Infection.

An object of the present study was the development of liposomes loaded with the medicine Veklury® (remdesivir) stabilized by electrostatic adsorption of polysaccharide film formed from chitosans with different physicochemical characteristics and hyaluronic acid. The functionalization of the structures was achieved through the inclusion of an aptamer (oligonucleotide sequence) with specific affinity to the spike protein of the human coronavirus HCoV-OC43. The hydrodynamic size, electrokinetic potential and stability of the structures were evaluated at each step in the procedure. The encapsulation efficiency and loaded amount of remdesivir (99% and 299 µg/mL) were estimated by UV-vis spectroscopy. Our investigations showed manifestation of promising tendencies for prolonged periods of the drug release and increased effectiveness of its antiviral action. Among all studied versions of the delivery system, the most distinguished and suitable in a model coronavirus therapy are the liposomes formed from chitosan oligosaccharides. The cytotoxicity of the liposomes was determined against the HCT-8 cell line. A cytopathic effect inhibition test was used for the assessment of the antiviral activity of the compounds. The virucidal activity and the effect on the viral adsorption of the samples were reported by the end-point dilution method, and the alteration in viral titer was determined as Δlgs compared to untreated controls. The redox-modulating properties of the nanoparticles were studied in vitro in certain/several/a few chemical model systems. Our investigations showed a manifestation of promising tendencies for a prolonged effect of the drug release and increased effectiveness of its antiviral action.

Single‐molecule fluorescence microscopy for imaging chemical reactions: Recent progress and future opportunities for advancing polymer systems

AbstractSingle‐molecule fluorescence (smFL) imaging techniques have evolved greatly over the past two decades to encompass the ability to monitor chemical reactions, providing unique advantages of non‐invasive sample preparation and characterization, labeling specificity, and high spatial and temporal resolutions. This work summarizes the recent progress in this important area by first providing a brief overview of different smFL techniques, including their common optical setups and working principles. We then introduce recent developments of smFL to characterize various model chemical reaction systems, such as biochemical synthesis, catalyzed systems, and nanomaterial assembly. Furthermore, several representative areas of using smFL to understand polymer reactions are discussed, including understanding interfacial phenomenon and polymerization kinetics, as well as characterizing electrochemical reactions. We also highlight the outlook of this exciting field and potential opportunities for further development and application of smFL to enable advances in polymer chemistry and physics.

Inhibitory Effects of Some Hydrocolloids on the Formation of Advanced Glycation End Products and Heterocyclic Amines in Chemical Models and Grilled Beef Patties.

Effectively inhibiting the formation of heterocyclic amines (HAs) and advanced glycation end products (AGEs) is crucial to human health. In the present study, chemical model systems were used to evaluate the inhibitory effects of seven hydrocolloids on HA and AGE formation. The results showed that hydrocolloids effectively inhibited the formation of two major AGEs. However, their inhibitory action against HA formation showed unexpected results, wherein alginic acid, carrageenan and konjac glucomannan promoted the formation of 2-Amino-1-methyl-6-phenylimidazo [4,5-b]pyridine (PhIP), harmane, norharmane and 2-amino-3,8-dimethyl-imidazo [4,5-f]-quinoline (MeIQx). Only chitosan and pectin showed significant inhibitory effects on HAs, reducing HA levels by 34.5-56.3% and 30.1-56.6%, respectively. In grilled beef patties, the addition of 1.5% chitosan and pectin significantly decreased AGE and HA content by 53.8-67.0% and 46.9-68.1%, respectively. Moreover, it had a limited impact on quality and sensory properties. Further mechanism studies conducted in model systems revealed that chitosan and pectin decreased the formation of key intermediates of AGEs and HAs. These findings suggest that chitosan and pectin are powerful inhibitors against AGE and HA formation with minimal impact on food quality. Therefore, their application in meat preparation and processing could effectively decrease human dietary exposure to HAs and AGEs.

A Full Quantum Mechanical Approach Assessing the Chemical and Electromagnetic Effect in TERS.

Tip-enhanced Raman spectroscopy (TERS) is a valuable method for surface analysis with nanometer to angstrom-scale resolution; however, the accurate simulation of particular TERS signals remains a computational challenge. We approach this challenge by combining the two main contributors to plasmon-enhanced Raman spectroscopy and to the high resolution in TERS, in particular, the electromagnetic and the chemical effect, into one quantum mechanical simulation. The electromagnetic effect describes the sample's interaction with the strong, highly localized, and inhomogeneous electric fields associated with the plasmonic tip and is typically the thematic focus for most mechanistic studies. On the other hand, the chemical effect covers the different responses to the extremely close-range and highly position-sensitive chemical interaction between the apex tip atom(s) and the sample, and, as we could show in previous works, plays an often underestimated role. Starting from a (time-dependent) density functional theory description of the chemical model system, comprised of a tin(II) phthalocyanine sample molecule and a single silver atom as the tip, we introduce the electromagnetic effect through a series of static point charges that recreate the electric field in the vicinity of the plasmonic Ag nanoparticle. By scanning the tip over the molecule along a 3D grid, we can investigate the system's Raman response on each position for nonresonant and resonant illumination. Simulating both effects on their own already hints at the achievable signal enhancement and resolution, but the combination of both creates even stronger evidence that TERS is capable of resolving submolecular features.

Tin transport and cassiterite precipitation from hydrothermal fluids

Cassiterite (SnO2) is the main ore mineral of tin in magmatic–hydrothermal tin deposits, but tin transport and precipitation mechanisms from hydrothermal fluids remain poorly understood. We critically evaluated aqueous tin speciation in hydrothermal fluids from extensive experimental data and thermodynamic modeling. Sn(II) chloride complexes in hydrothermal fluids exist mainly as SnCl+, SnCl2(aq), and SnCl3−. The revised Helgeson–Kirkham–Flowers model parameters of these three tin species and two tin ions (Sn4+ and Sn2+) were derived from the correlation algorithms among these parameters, and the standard molar properties of cassiterite were optimized to be internally consistent with the available thermodynamic dataset. These thermodynamic parameters, together with the available equilibrium constant equation of Sn(IV) chloride complexes, could reproduce the available solubility data of cassiterite in acidic solutions at 400–700 °C under oxygen fugacity (fO2) levels buffered by hematite–magnetite (HM) or nickel–nickel oxide (NNO). These comparisons allow modeling chemical systems of SnO2–NaCl–HCl–H2O (liquid phase) to examine tin transport and cassiterite precipitation mechanisms under tin-mineralizing conditions: 300–500 °C, 50–150 MPa, 2 molal NaCl, and fO2 levels from QFM (quartz–fayalite–magnetite) to HM. Sn(II) chloride complexes are commonly interpreted to dominate in aqueous tin speciation under fO2 = NNO, but our modeling results indicate that considerable contents of Sn(IV) chloride complexes also exist in those reduced fluids with high HCl contents, consistent with recent in situ high-temperature experiments and molecular dynamic simulations. The Sn(II)/Sn(IV) ratios in fluids depends on fO2, temperature, and HCl contents. A considerable amount of Sn(IV) possibly exist in an early mineralization stage even under fO2 = NNO; if so, redox reactions are unnecessary to precipitate cassiterite from these mineralizing fluids. We find that even if the fO2 levels are constant, simple cooling can alter mineralizing fluids to be more oxidized (e.g., from QFM to HM) and cause cassiterite precipitation, indicating that oxidizing agents are not necessary as previously thought. This explains why cassiterite can precipitate in host rocks (e.g., sandstone or quartzite) that do not provide oxidizing agents. A simple rise in fO2 levels and pH neutralization (e.g., greisenization) also cause cassiterite precipitation. Cassiterite solubility in oxidized acidic hydrothermal fluids (NNO < fO2≤HM) is high enough to account for the tin contents of fluid inclusions from typical tin deposits, but the mineralization potential of oxdized fluids is inferior to reduced fluids (fO2≤ NNO) under the same conditions.

Determination of 2-amino-1-methyl-6-phenylimidazole [4, 5-b] pyridine (PhIP) and its precursors and possible intermediates in a chemical model system and roast pork

PhIP (2-amino-1-methyl-6-phenylimidazole [4, 5-b] pyridine) is a carcinogenic heterocyclic aromatic amine often generated in thermal processing of food. Methods for PhIP and its precursors and possible intermediates determination in chemical model system and roast pork were established based on HPLC-Q-Orbitrap-HRMS and GC-MS. Results showed that the linearity of 8 targets was good in a certain concentration range (R2 ≥ 0.992). LODs and LOQs were in the range of 0.3–15 μg/kg and 1–50 μg/kg, respectively. Under the model system, the recoveries of 8 target compounds ranged from 86.3% to 119.2%, with relative standard deviations (RSDs) of 0.5–6.9%. The established method was applied to 8 targets determination in roast pork, with recoveries ranging from 87.1% to 107.3% and RSDs in the range of 1.2–7.8%. The developed methods are accurate and fast, which are suitable for PhIP and its precursors and possible intermediates analysis in chemical model system and actual meat products.

Is there a better way of representing stationary wave functions than basis expansion?

We extend our previously developed approach for finding the exact analytical form of ground state wave function of single-electron Schrödinger equations to target arbitrary excited states of 1D model chemical systems of hydrogen atom and H 2 + $$ {\mathrm{H}}_2^{+} $$ with soft Coulomb potential. Our representation of the wave functions is formally unified by a factorized formula involving a polynomial prefactor encoding the nodal information, a non-integer power prefactor, and an exponentially decaying term modulated by a modulator function. We show that our method leads to faster energy convergence than the basis expansion method, and hence is a better way of representing the wave function. This conclusion is also validated in the real-world H 2 + $$ {\mathrm{H}}_2^{+} $$ .

Acylated anthocyanin inhibited the formation of heterocyclic amines in hybrid chemical model system and its underlying mechanism

Enzymatic acylation was employed to synthesize acylated anthocyanin, and a hybrid chemical model system was used for the formation of heterocyclic amines. And the inhibition effect and underline mechanism were investigated by analyzing the variations in important precursors and intermediates. Results confirmed that cyanidin-3-(6-cinnamoyl) -glycosidase (C3(6C)G) with a purity of 98.9% was obtained. HPLC identified seven types of heterocyclic amines (IQ, MeIQx, 4,8-DimeiqX, Norharman, Harman, PhIP, and AαC) generated in the chemical model. (C3(6C)G) showed a good concentration-dependent manner for the inhibition effect on most HCAs except for MeIQx and PhIP. It also suppressed the glucose content, showed a dose-dependent manner in creatine/creatinine inhibition, and could scavenge formaldehyde, acetaldehyde, and phenylacetaldehyde. Two potential pathways might be involved: 1. by inhibiting the content of precursors (glucose and creatinine), competing with the formation of amino acids, to suppress HCAs generation; 2 through the removal of reactive carbonyl, reducing its reaction with creatinine.

Improvement of local ozone phytotoxicity modelling for autochthonous grape cultivars

The grapevine is a key crop for Mediterranean environments and is both sensitive to climate warming and air pollutants, of which ozone is the most damaging to crop yield and quality. Ambient ozone effects on the grapevine have been noticed since the late fifties but risk assessments are still impaired by the lack of information concerning differences in cultivar sensitivity, and adaptation capacity to environmental factors including drought conditions. This study develops a specific parametrization for autochthonous grape cultivars within a leaf-level stomatal flux model, the DO3SE model, coupled with a meteorological and atmospheric chemical transport modelling system, the WRF-CHIMERE, by using a renowned wine producing area, the Douro wine region of Portugal, as case study. The DO3SE model parametrization introduced in this study included phenology, photosynthetic active radiation, air temperature, air vapour pressure deficit, and leaf water potential as a proxy of soil water content. The modelling experiments, which included simulations with the current default Convention on Long-Range Transboundary Air Pollution DO3SE parametrization and with the proposed parametrization, covered a reference grapevine growing season (from April to September 2017), during which a measuring campaign was carried out. Simulation results show that the proposed parametrization succeeded to replicate the observed grapevine leaf-level stomatal flux gradient in the region. Both field and modified DO3SE model values indicate that considerable areas in the Douro wine region of Portugal can exceed critical phytotoxic ozone dose (POD) values, although with a lower and different spatial extent when compared to the default DO3SE parametrization for the grapevine. However, under irrigated conditions, the POD values increase, and the values are close to those obtained with the default parametrization. Overall, the research results indicate that air quality management, in particular the reduction of ozone levels in the ambient air, must also be considered to define sustainable grape and wine production strategies in the context of climate and wine production management change.

Quantification of Key Peroxy and Hydroperoxide Intermediates in the Low-Temperature Oxidation of Dimethyl Ether

Dimethyl ether (DME) oxidation is a model chemical system with a small number of prototypical reaction intermediates that also has practical importance for low-carbon transportation. Although it has been studied experimentally and theoretically, ambiguity remains in the relative importance of competing DME oxidation pathways in the low-temperature autoignition regime. To focus on the primary reactions in DME autoignition, we measured the time-resolved concentration of five intermediates, CH3OCH2OO (ROO), OOCH2OCH2OOH (OOQOOH), HOOCH2OCHO (hydroperoxymethyl formate, HPMF), CH2O, and CH3OCHO (methyl formate, MF), from photolytically initiated experiments. We performed these studies at P = 10 bar and T = 450-575 K, using a high-pressure photolysis reactor coupled to a time-of-flight mass spectrometer with tunable vacuum-ultraviolet synchrotron ionization at the Advanced Light Source. Our measurements reveal that the timescale of ROO decay and product formation is much shorter than predicted by current DME combustion models. The models also strongly underpredict the observed yields of CH2O and MF and do not capture the temperature dependence of OOQOOH and HPMF yields. Adding the ROO + OH → RO + HO2 reaction to the chemical mechanism (with a rate coefficient approximated from similar reactions) improves the prediction of MF. Increasing the rate coefficients of ROO ↔ QOOH and QOOH + O2 ↔ OOQOOH reactions brings the model predictions closer to experimental observations for OOQOOH and HPMF, while increasing the rate coefficient for the QOOH → 2CH2O + OH reaction is needed to improve the predictions of formaldehyde. To aid future quantification of DME oxidation intermediates by photoionization mass spectrometry, we report experimentally determined ionization cross-sections for ROO, OOQOOH, and HPMF.

Inhibitory effects of hydrocolloids on the formation of heterocyclic aromatic amines in smoked chicken drumsticks and the underlying mechanism

This study aims to investigate the inhibitory effects of hydrocolloids on heterocyclic aromatic amine (HAA) formation in chemical model systems and smoked chicken drumsticks. In chemical model systems I and II, xanthan gum (XG) and carboxymethyl cellulose sodium (CMC-Na) effectively inhibited the 2-amino-1-methyl-6-phenylimidazo[4,5- b ]pyridine (PhIP), 1-methyl-9H-pyrido[3,4- b ]indole (Harman), and 9H-pyrido[3,4- b ]indole (Norharman) formation in comparison with the control sample ( P < 0.05). Arabic gum (AG) inhibited the PhIP and Harman formation ( P < 0.05), but its inhibitory action against Norharman formation was not significant ( P > 0.05). Further mechanism investigation of chemical model system I showed that the formation of PhIP was mainly inhibited via trapping phenylalanine and creatinine by glyoxal and methyglyoxal. A mechanistic investigation of chemical model system II suggested the inhibition of Harman and Norharman formation by XG and CMC-Na could be through trapping tryptophan by glyoxal and methyglyoxal. In smoked chicken drumsticks, CMC-Na had a dose-dependent inhibitory effect against the PhIP, Harman, and Norharman formation in comparison with the control sample ( P < 0.05), and 2.0% CMC-Na had the highest inhibitory rates of 45.83%, 21.82%, and 30.92%, respectively. Moreover, CMC-Na effectively inhibited the formation of PhIP, Harman, and Norharman precursors and intermediates in smoked chicken drumsticks, which further confirmed the above inhibition mechanism of CMC-Na. These results could provide an effective approach to reduce HAA formation in smoked meat products by incorporating hydrocolloids. • XG and CMC-Na inhibit PhIP, Harman, and Norharman formation in chemical model system. • AG inhibit the formation of PhIP and Harman in chemical model system. • 2.0% CMC-Na is the most promising inhibitor of HAAs in smoked chicken drumsticks. • Hydrocolloids can inhibit HAAs by trapping their precursors and intermediates.

Analysis of the National Air Pollutant Emissions Inventory (CAPSS 2018) Data and Assessment of Emissions Based on Air Quality Modeling in the Republic of Korea

According to the 2018 National Air Pollutant Emissions Inventory (NEI), air pollutant emissions in the Republic of Korea comprised 808,801 tons of CO, 1,153,265 tons of NOX, 300,979 tons of SOX, 617,481 tons of TSP, 232,993 tons of PM10, 98,388 tons of PM2.5, 15,562 tons of black carbon (BC), 1,035,636 tons of VOCs, and 315,975 tons of NH3. As for national emission contributions to primary PM2.5 and PM precursors (NOX, SOX, VOCs, and NH3), major source categories were the road sector for NOX, the industry sector for SOX and PM2.5, and the everyday activities and others sector for VOCs and NH3. In the case of emissions by region, the largest amount of NOX was emitted from the Seoul Metropolitan Areas (SMA; Seoul, Incheon, and Gyeonggi-do, hereafter SMA) and the largest amounts of SOX, PM2.5, VOCs, and NH3 were from the Yeongnam region. A 3D chemical transport modeling system was used to examine the uncertainty of the national air pollutant emissions based on the National Emission and Air Quality Assessment System (NEAS). Air quality was simulated using CAPSS 2018, and the simulation data were compared with observed concentrations to examine the uncertainties of the current emissions. These data show that emissions from five si (cities) (Pohang, Yeosu, Gwangyang, Dangjin, and Ulsan) need to be improved. Most of all, it is necessary to examine the emissions from places of business that use anthracite, which is the major PM2.5 emission source, as fuel in these areas.

Inhibition effects of typical antioxidants on the formation of glycidyl esters in rice oil and chemical model during high temperature exposure

Glycidyl esters (GEs) are heat-induced processing contaminants in refined oil. This study aimed to investigate the inhibition effects of seven typical antioxidants including quercetin (QU), astaxanthin (AS), tert-butylhydroquinone (TBHQ), propyl gallate (PG), L-ascorbyl palmitate (AP), puerarin (PU), and α-tocopherol (VE) on the generation of GEs in rice oil (RO) and chemical model systems during high-temperature exposure. The results showed that all selected antioxidants (0.06%, m/m) significantly inhibited the generation of GEs in both RO and chemical model systems heated at 240 °C for 1.5 h. The inhibitory effects in RO were ranked as: PG > AS > AP > PU > TBHQ > QU > VE. PG, AS and AP with different multiple antioxidant mechanisms exhibited the significantly better GEs-inhibition effects in RO (43.20%, 30.82%, and 27.72%, respectively). Further study found that increasing doses of PG led to a dose-dependent decrease in the inhibition rate of GEs in RO. Amazingly, AS could promote the formation of GEs in RO heated at 270 °C. The GEs inhibition of PG and AS in RO exhibited a remarkable time-dependent effect. These results may widen the knowledge for the chemical inhibition of GEs by blocking reaction path, and also provide new perspective on GEs inhibition in refined oil by natural compounds.