Peaks In Mode Research Articles

Exploring Bioactive Compounds in Prosopis juliflora Extracts Through Comparative LC–MS Analysis

ABSTRACTThe current study was carried out to assess the alkaloid‐enriched constituents of Prosopis juliflora (Fabaceae) against bacterial blight of pomegranate. Utilising plant extracts for disease management offers an eco‐friendly approach. In vitro assessment of the minimum inhibitory concentration (MIC) for alkaloid‐enriched fractions from the leaves and inflorescence of P. juliflora revealed a 14 mm zone of inhibition, with the lowest MIC value being 30 mg/mL. Untargeted metabolomics analysis of alkaloid‐rich fractions (ARF) from four different tissues of P. juliflora, subjected to LC–MS for alkaloid identification, detected a total of 1489 peaks in positive mode and 240 peaks in negative mode. The highest peaks were detected in the leaves, where 47 metabolites and 9 alkaloids were identified. Ellipticine and ormosanine were found in relatively high concentrations across all four tissues, as indicated by their peak areas. The inflorescence had significantly high concentrations of sparteine, solanidine‐I and puberanidine compared with other parts. Additionally, acetylsolanine was more abundant in the inflorescence, while solasodine‐I was more prevalent in the leaves. A substantial amount of strictosidine was also found in the inflorescence.

Graphite Sheet-Assisted Laser Desorption Ionization-Mass Spectrometry for Small Organic Compound Analysis.

Carbon-based nanopowders have been used as ionization materials for laser desorption ionization-mass spectrometry (LDI-MS) and are very efficient at detection in low m/z regions. In this study, we aimed to develop a new sheet-type graphite material that possessed a randomly grooved nanostructured surface consisting of developed sp2-conjugated atomic carbon to facilitate the desorption/ionization of small compounds in LDI-MS. The graphite sheet exhibited higher UV absorption and provided higher ionization efficiency and survival yield in the LDI-MS detection of a thermometer ion, 4-chloro-benzopyridinium, than those of highly oriented graphite plates. These properties demonstrate that the present graphite sheet is suited for use as an LDI-MS material. Graphite sheet-assisted LDI-MS successfully detected various substances, including amino acids, peptides, and polyethylene glycol polymers, with higher ion intensities and less noise than those associated with conventional organic matrix-assisted LDI-MS (MALDI-MS). Furthermore, graphite sheet-assisted LDI-MS analysis provided more peaks (252 peaks) derived from soy sauce than those obtained by MALDI-MS (36 peaks) and required fewer preparation processes (dilution and air-dried) compared with previously established graphite carbon black-assisted LDI-MS (171 peaks) in the positive mode. This study demonstrates that graphite sheet-assisted LDI-MS has the potential for small organic compound analyses in the biomedical and food science fields.

Combination of in silico prediction and convolutional neural network framework for targeted screening of metabolites from LC-HRMS fingerprints: A case study of “Pericarpium Citri Reticulatae - FructusAurantii”

In this study, a novel approach is introduced, merging in silico prediction with a Convolutional Neural Network (CNN) framework for the targeted screening of in vivo metabolites in Liquid Chromatography-High Resolution Mass Spectrometry (LC-HRMS) fingerprints. Initially, three predictive tools, supplemented by literature, identify potential metabolites for target prototypes derived from Traditional Chinese Medicines (TCMs) or functional foods. Subsequently, a CNN is developed to minimize false positives from CWT-based peak detection. The Extracted Ion Chromatogram (EIC) peaks are then annotated using MS-FINDER across three levels of confidence. This methodology focuses on analyzing the metabolic fingerprints of rats administered with "Pericarpium Citri Reticulatae - Fructus Aurantii" (PCR-FA). Consequently, 384 peaks in positive mode and 282 in negative mode were identified as true peaks of probable metabolites. By contrasting these with “blank serum” data, EIC peaks of adequate intensity were chosen for MS/MS fragment analysis. Ultimately, 14 prototypes (including flavonoids and lactones) and 40 metabolites were precisely linked to their corresponding EIC peaks, thereby providing deeper insight into the pharmacological mechanism. This innovative strategy markedly enhances the chemical coverage in the targeted screening of LC-HRMS metabolic fingerprints.

Explore the Constituents and Mechanism of Traditional Chinese Medicine Preparation Zhachong Shisan Pills Based on HPLC-QTOF-MS and Network Pharmacology

Introduction: Th study aims to establish the chromatographic fingerprint of Zhachong Shisan pills (ZSP), and to explore its active components and mechanism of analgesic and anti-inflammatory action. Method: First, the Personal Compound Database and Library (PCDL) of ZSP was constructed through literature mining, and then the chemical composition and fingerprint of methanol extractions from 8 batches of ZSP were studied using High-Performance Liquid Chromatography with Quadrupole Time-Of-Flight tandem Mass Spectrometry (HPLC-QTOF-MS) technology. Furthermore, network pharmacology was used to explore the active compounds, potential targets, and signal pathways of analgesic and anti-inflammatory activity of ZSP. A total of 102 compounds were detected in positive and negative ion mode. Results: Fifty-six characteristic peaks in positive ion mode and 78 characteristic peaks in negative ion mode were confirmed as common peaks in the fingerprint of ZSP. Through network pharmacology research, the effective components, key targets, and signal pathways of ZSP for the treatment of cerebral apoplexy by analgesic and anti-inflammatory effects were all analyzed. Conclusion: This study explained the substance basis of the analgesic and anti-inflammatory effects of Zhachong Shisan Pills, and explores its possible mechanisms, providing ideas for rational clinical medication and in-depth pharmacological research.

Air-silica core microstructured optical fiber-based SPR sensor for temperature and refractive index measurement

We propose an air-silica core microstructured optical fiber-based surface plasmon resonance (SPR) sensor to simultaneously measure temperature and refractive index (RI). The sensing channel is formed by coating the outside of the fiber with a gold film and a polydimethylsiloxane (PDMS) layer as a temperature sensing medium, and then being immersed into the liquid analyte. The plasmon mode can penetrate through the PDMS layer and then into the analyte, therefore both the temperature and the analyte RI changings can lead to the variations of SPR spectra that will be measured. Our numerical results demonstrate that the proposed sensor can support two resonance peaks in the x-polarized core mode and one resonance peak in the y-polarized core mode, therefore providing two detection approaches, peak-based and polarization-based approaches. By measuring the two peaks in the x-polarized core mode, for the peak-based approach, the temperature coefficients are −2.077 nm/°C and −2.723 nm/°C, and the RI coefficients are 1252 nm/RIU and 1931 nm/RIU, respectively. While by measuring the second peak in x-polarized core mode and the peak in y-polarized core mode, for the polarization-based approach, the temperature coefficients are −2.723 nm/°C and −3.401 nm/°C, and the RI coefficients are 1931 nm/RIU and 2973 nm/RIU, respectively.

Insights into the growth parameters, mineral composition, protein and UHPLC–QTOF–LC/MS‐based non‐targeted metabolomic fingerprints of wheatgrass as a function of photoperiod and temperature

SummaryWheatgrass juice powder (WJP) obtained from four Indian wheat varieties grown under different photoperiod and temperature conditions were examined for growth parameters, chlorophyll content, mineral composition, protein and metabolomic profile. The percentage yield and total chlorophyll content of WJP varied from 2.5% to 9.12% and 1.08 to 4.76 mg g−1, respectively. The WJP obtained from PBW‐752 showed the highest yield and total chlorophyll content. The mineral composition (Na, K, Ca and Mg) of WJP also showed variation with different photoperiod and temperature conditions. The electrophoretic pattern of total soluble proteins of WJP showed variability in the accumulation of high and low molecular weight polypeptides against different photoperiod and temperature conditions. The comprehensive metabolites profile of WJP was analysed by UHPLC–QTOF–liquid chromatography/mass spectrometry. Based on the retention times and m/z values, 1012 feature peaks in positive ionisation mode were detected. The metabolomic profile of WJP revealed 180 different classes of primary and secondary metabolites.

Systematic analysis of in-source modifications of primary metabolites during flow-injection time-of-flight mass spectrometry

Flow-injection mass spectrometry (FI-MS) enables metabolomics studies with a very high sample-throughput. However, FI-MS is prone to in-source modifications of analytes because samples are directly injected into the electrospray ionization source of a mass spectrometer without prior chromatographic separation. Here, we spiked authentic standards of 160 primary metabolites individually into an Escherichia coli metabolite extract and measured the thus derived 160 spike-in samples by FI-MS. Our results demonstrate that FI-MS can capture a wide range of chemically diverse analytes within 30 s measurement time. However, the data also revealed extensive in-source modifications. Across all 160 spike-in samples, we identified significant increases of 11,013 ion peaks in positive and negative mode combined. To explain these unknown m/z features, we connected them to the m/z feature of the (de-)protonated metabolite using information about mass differences and MS2 spectra. This resulted in networks that explained on average 49 % of all significant features. The networks showed that a single metabolite undergoes compound specific and often sequential in-source modifications like adductions, chemical reactions, and fragmentations. Our results show that FI-MS generates complex MS1 spectra, which leads to an overestimation of significant features, but neutral losses and MS2 spectra explain many of these features.

UHPLC-Q-Exactive Orbitrap MS/MS-Based Untargeted Metabolomics and Molecular Networking Reveal the Differential Chemical Constituents of the Bulbs and Flowers of Fritillaria thunbergii.

Both the bulbs and flowers of Fritillaria thunbergii Miq. (BFT and FFT) are widely applied as expectorants and antitussives in traditional Chinese medicine, but few studies have been conducted to compare the chemical compositions of these plant parts. In this study, 50% methanol extracts of BFT and FFT were analyzed via UHPLC-Q-Exactive Orbitrap MS/MS, and the feasibility of using non-targeted UHPLC-HRMS metabolomics and molecular networking to address the authentication of bulb and flower samples was evaluated. Principal component analysis (PCA), Orthogonal Partial Least Squares-Discriminant Analysis (OPLS-DA), and heat map analysis showed there were dissimilar metabolites in BFT and FFT. As a result, 252 and 107 peaks in positive ion mode and negative mode, respectively, were considered to represent significant difference variables between BFT and FFT. Then, MS/MS-based molecular networking of BFT and FFT was constructed to perform an in-depth characterization of the peaks using different variables. A total of 31 alkaloids with significant differences were annotated in this paper, including seven cis-D/E-vevanine without C20-OH and one trans-D/E-cevanine with C20-OH, thirteen trans-D/E-cevanine without C20-OH, five cevanine N-oxide, and five veratramine. Among the 31 alkaloids, eight alkaloids had higher FFT than BFT contents, while all the flavonoids identified in our work had greater FFT than BFT contents. The influence of different ingredients on the pharmacological activities of BFT and FFT should be investigated in future studies.

Comparative analysis of the chemical constituents and in vitro antioxidant activities of different aqueous extracts of Cistanche phelypaea (L.) Cout. from Algeria

• Different aqueous extracts were prepared from Cistanche phelypaea roots. • Decoction presented the highest total phenolic content. • Identical qualitative chromatographic patterns were observed for all extracts. • Quantitative variations were highlighted in some of the identified compounds. • Cold maceration gave the extract with the weakest ferric reducing power activity. Cistanches herba are well-known for their nutritional and therapeutic effects, but only few reports are available about the species Cistanche phelypaea (L.) Cout. and studies of aqueous extracts are scarce. This study aimed to elucidate the impact of aqueous extraction methods including decoction, infusion and cold maceration from C. phelypaea roots on phytochemical composition and in vitro antioxidant activities of the extracts. In order to accomplish this, determinations of total phenolic and flavonoid contents, liquid chromatography electrospray ionization mass spectrometry (LC/ESI-MS and LC/ESI-MS/MS) analyses and in vitro antioxidant activity studies were carried out. All extracts had significant levels of total phenolic content, but the decoction possessed the highest concentration and no significant difference was observed between infusion and cold maceration. Concerning flavonoids, decoction and infusion possessed the highest concentrations. Data obtained from LC/ESI-MS and LC/ESI-MS/MS analyses showed similar qualitative profiles for all aqueous extracts with 14 characteristic chromatographic peaks in negative mode and 6 in positive mode, which allowed the tentative identification of syringin, 14 phenylethanoid glycosides and 5 iridoids, including 5 pairs of isomers. However, significant variations were recorded for the relative abundance of some compounds depending on the method that was employed. Hot extraction procedures, decoction and/or infusion were more efficient in extracting acteoside, isoacteoside and two molecules corresponding to isomers of 2ʹ-acetylacteoside/tubuloside B, and it seems that a longer time of heating-extraction was required for an improved extraction of isoacteoside, and one of the two isomers of 2ʹ-acetylacteoside/tubuloside B, as decoction gave a significant higher amount of these compounds. However, 8-epiloganic acid and cistanoside F, with their respective isomers, and syringin were more extractable by the cold maceration process. All extracts had similar antioxidant properties in scavenging DPPH radical and total antioxidant activity assays, with the exception of the ferric-reducing power activity assay, in which cold maceration exhibited a significantly less potent activity. Aqueous extracts of C. phelypaea roots present an interesting antioxidant potential which is related to the synergistic effects of several antioxidant compounds.

Year-round observation of atmospheric inorganic aerosols in urban Beijing: Size distribution, source analysis, and reduction mechanism

To investigate particle characteristics and find an effective measure to control severe particle pollution, year-round observation of size-segregated inorganic aerosols was conducted in Beijing from January to December, 2016. The sampled atmospheric particles all presented bimodal size distribution at four pollution levels (clear, slight pollution, moderate pollution and severe pollution), and peak values appeared at the size range of 0.7-2.1 μm and >9.0 μm, respectively. As dominant particle compositions, NO3−, SO42−, and NH4+ in four pollution levels all showed significant peaks in fine mode, especially at the size range of 1.1-2.1 μm. Secondary inorganic aerosols accounted for about 67.6% (36.3% (secondary sulfates) + 31.3% (secondary nitrates)) of the total sources of fine particles in urban Beijing. Severe pollution of fine particles was mainly caused by the air masses transported from nearby western and southern areas, which are industrial and densely populated region, respectively. Sensitivity tests further revealed that the control measures focusing on ammonium emission reduction was the most effective for particle pollution mitigation, and fine particles all showed nonlinear responses after reducing ammonium, nitrate, and sulfate concentrations, with the fitting curves of y = -120.8x - 306.1x2 + 290.2x3, y = -43.5x - 67.8x2, and y = -25.8x - 110.4x2 + 7.6x3, respectively (y and x present fine particle mass variation (μg/m3) and concentration reduction ratio (CRR)/100 (dimensionless)). Overall, our study presents useful information for understanding the characteristics of atmospheric inorganic aerosols in urban Beijing, as well as offers policy makers with effective measure for mitigating particle pollution.

Effect of LP-EGR on the Emission Characteristics of GDI Engine

Exhaust gas recirculation (EGR) can improve the fuel economy of gasoline direct-injection (GDI) engines, but at the same time it will have a significant impact on emissions. In this paper, the effects of low-pressure exhaust gas recirculation (LP-EGR) and its rate on the main gaseous and particulate emission characteristic of a GDI engine were investigated. The results showed that the particle size distribution of the GDI engine presented bimodal peaks in nucleation and accumulation mode, and the nucleation mode particles comprised the vast majority of the total particles. The effect of LP-EGR on emissions depended on the engine conditions. At low and medium speed, the particle emissions increased with the increase in the EGR rate, while at high speed, a reduction in the particle emission was observed. When the engine operated in full load condition, an increase in the EGR rate reduced the particle number (PN) concentration significantly, but increased the particle mass (PM) concentration. In terms of the gaseous emission, the EGR could reduce as much as 80% of the NOx emission; however, the total hydrocarbons (THC) emission presented an increased trend, and the maximum increase reached 23.5%. At low and medium loads, the EGR could reduce the CO emission, but at high load, the CO emission worsened with the EGR.

Barbeya oleoides Leaves Extracts: In Vitro Carbohydrate Digestive Enzymes Inhibition and Phytochemical Characterization.

This study investigated the in vitro inhibitory potential of different solvent extracts of leaves of Barbeya oleoides on key enzymes related to type 2 diabetes mellitus (α-glucosidase and α-amylase) in combination with an aggregation assay (using 0.01% Triton X-100 detergent) to assess the specificity of action. The methanol extract was the most active in inhibiting α-glucosidase and α-amylase, with IC50 values of 6.67 ± 0.30 and 25.62 ± 4.12 µg/mL, respectively. However, these activities were significantly attenuated in the presence of 0.01% Triton X-100. The chemical analysis of the methanol extract was conducted utilizing a dereplication approach combing LC-ESI-MS/MS and database searching. The chemical analysis detected 27 major peaks in the negative ion mode, and 24 phenolic compounds, predominantly tannins and flavonol glycosides derivatives, were tentatively identified. Our data indicate that the enzyme inhibitory activity was probably due to aggregation-based inhibition, perhaps linked to polyphenols.

Hepatopancreatic metabolomics shedding light on the mechanism underlying unsynchronized growth in giant freshwater prawn, Macrobrachium rosenbergii

The giant freshwater prawn, Macrobrachium rosenbergii (M. rosenbergii) as an important freshwater aquaculture species with high commercial value, exhibited unsynchronized growth. However, the potentially metabolic mechanism remains unclear. In this study, we used liquid chromatography tandem mass spectrometry (LC-MS/MS) to investigate the hepatopancreatic metabolic profiles of twenty giant freshwater prawns between the fast-growing group and slow-growing group. In the metabolomics assay, we isolated 8,293 peaks in positive and negative iron mode. Subsequently, 44 significantly differential metabolites were identified. Functional pathway analysis revealed that these metabolites were significantly enriched in three key metabolic pathways. Further integrated analysis indicated that glycerophospholipid metabolism and aminoacyl-tRNA biosynthesis have significant impact on growth performance in M.rosenbergii. Our findings presented here demonstrated the critical metabolites and metabolic pathways involved in growth performance, moreover provided strong evidence for elucidating the potentially metabolic mechanism of the unsynchronized growth in M. rosenbergii.

Modifying Electrical and Magnetic Properties of Single-Walled Carbon Nanotubes by Decorating with Iron Oxide Nanoparticles

In this work, we report a facile approach to modify the magnetic and electrical property of Hipco single-walled carbon nanotubes (SWCNTs) by attaching iron oxide nanoparticles (FeNPs). The Raman spectra of FeNP-SWCNTs revealed an apparent intensity reduction of metallic peaks in Radial breathing mode (RBM) region, which indicates the ratio change between the metallic and semiconducting component of SWCNTs after modification. Distinctive magnetic and electric resistance properties of FeNP-SWCNTs were found to be associated with the different shapes of FeNPs. The specific FeNP examples as showcased in this work can be applied to tune the electric and magnetic properties of other nanostructured materials in general and shed light on various electronic and magnetic applications.

Nonlinear vibration of a nanocomposite laminated piezoelectric trapezoidal actuator in subsonic airflow under combined electrical and forcing excitations

The nonlinear dynamic and vibration behaviors of a cantilevered carbon nanotube-reinforced composite trapezoidal plate with two surface-bonded piezoelectric layers as an actuator in micro air vehicles are considered in this article. The plate is reinforced by single-walled carbon nanotubes and is exposed to subsonic airflow under combined parametric and external excitations. The large deflection von Karman plate assumptions and the classical laminated plate theory are applied to derive the governing equations of the motion of the piezoelectric nanocomposite laminated trapezoidal plate by using Hamilton's principle. The geometry of the trapezoidal plate is mapped into a rectangular computational domain. The Galerkin's approach is used for transforming the nonlinear partial differential equations of motion into nonlinear two-degrees-of-freedom ordinary differential equations of cubic nonlinearities. The case of 1:3 internal resonance and primary resonance is considered, and the multiple scales method is employed. The aerodynamic pressure distribution formula is modeled by linear potential flow theory. The frequency and time history responses and phase portrait in free forced vibrations are obtained to analyze the nonlinear dynamic behavior of the plate. The effects of different parameters such as the plate geometry, volume fraction of carbon nanotubes, and different excitations on the nonlinear vibration of the thin laminated plate are also discussed. A complex softening nonlinearity with two peaks in the higher mode is observed in frequency response curves. The influence of electrical excitation with several amplitudes and frequencies on dynamic stability is investigated using time response curves.

Mass Concentrations and Size Distributions of Water-soluble Inorganic Ions in Atmospheric Aerosols in Beibei District, Chongqing

In order to study the concentration and distribution characteristics of water-soluble inorganic ions in aerosol particles of the Beibei district of Chongqing, aerosol samples were collected with an Andersen cascade impactor between March 2014 and February 2015. Water-soluble inorganic ions, including Na+, NH4+, K+, Mg2+, Ca2+, F-, Cl-, NO3-, and SO42- were determined for different particle sizes (9.00, 5.80, 4.70, 3.30, 2.10, 1.10, 0.65, and 0.43 μm) using the ion chromatography method. Results showed that SO42-, NH4+, NO3-, Cl-, Na+, and K+ were mainly distributed in fine particles, while Mg2+, Ca2+, and F- were mainly present in coarse particles. SNA (SO42-, NH4+, and NO3-) exhibited clear unimodal distribution, with peaks in the droplet mode of 0.65-1.10 μm, mainly present in the form of (NH4)2SO4 and NH4NO3 in fine particles. The formation of SO42- is mainly attributed to in-cloud processes and partly to oxidation of SO2. Na+, Cl-, and Mg2+ exhibited bimodal distribution in coarse and fine particles; K+ was a single peak distribution in the range of 0.43-1.10 μm, while peaks of F- and Ca2+ concentrations were in coarse particles. Average annual concentrations of total water-soluble ions in PM2.1 and PM9.0 were (32.68±15.28) μg·m-3and (48.01±19.66) μg·m-3 over the observation period. Seasonal variations of PM2.1 and PM9.0concentrations decreased in the order of winter > spring > summer > autumn. This was the same for most ions, but a small number of ions (F-, Mg2+ and Ca2+) had a different pattern in the spring, summer, and winter. The SNA were the major components of water-soluble ions in PM2.1, and Ca2+ was the major component of water-soluble ions in PM9.0 besides SNA. The concentration of cations was significantly higher than that of anions' in PM2.1 and PM9.0, with a certain correlation between different ions. Emissions from motor vehicle exhaust, combustion processes, soil sources, and fugitive dust were the major sources of water-soluble ions in this area. The effect of air temperature on secondary ions is significant (P<0.05), but relative humidity and wind speed have no significant effect (P>0.05).

Simple and Robust N-Glycan Analysis Based on Improved 2-Aminobenzoic Acid Labeling for Recombinant Therapeutic Glycoproteins

N-glycans of therapeutic glycoproteins are critical quality attributes that should be monitored throughout all stages of biopharmaceutical development. To reduce both the time for sample preparation and the variations in analytical results, we have developed an N-glycan analysis method that includes improved 2-aminobenzoic acid (2-AA) labeling to easily remove deglycosylated proteins. Using this analytical method, 15 major 2-AA–labeled N-glycans of Enbrel® were separated into single peaks in hydrophilic interaction chromatography mode and therefore could be quantitated. 2-AA–labeled N-glycans were also highly compatible with in-line quadrupole time-of-flight mass spectrometry (MS) for structural identification. The structures of 15 major and 18 minor N-glycans were identified from their mass values determined by quadrupole time-of-flight MS. Furthermore, the structures of 14 major N-glycans were confirmed by interpreting the MS/MS data of each N-glycan. This analytical method was also successfully applied to neutral N-glycans of Humira® and highly sialylated N-glycans of NESP®. Furthermore, the analysis data of Enbrel® that were accumulated for 2.5 years demonstrated the high-level consistency of this analytical method. Taken together, the results show that a wide repertoire of N-glycans of therapeutic glycoproteins can be analyzed with high efficiency and consistency using the improved 2-AA labeling–based N-glycan analysis method.

Variations of aerosol size distribution, chemical composition and optical properties from roadside to ambient environment: A case study in Hong Kong, China

This study investigated the “roadside-to-ambient” evolution of particle physicochemical and optical properties in typical urban atmospheres of Hong Kong through collection of chemically-resolved PM2.5 data and PM2.5 size distribution at a roadside and an ambient site. Roadside particle size distribution showed typical peaks in the nuclei mode (30–40 nm) while ambient measurements peaked in the Aitken mode (50–70 nm), revealing possible condensation and coagulation growth of freshly emitted particles during aging processes. Much higher levels of anthropogenic chemical components, i.e. nitrate, sulfate, ammonium, organic carbon (OC) and elemental carbon (EC), but lower levels of OC/EC and secondary inorganic aerosols (SIA)/EC ratios appeared in roadside than ambient particles. The high OC/EC and SIA/EC ratios in ambient particles implied high contributions from secondary aerosols. Black carbon (BC), a strong light absorbing material, showed large variations in optical properties when mixed with other inorganic and organic components. Particle-bound polycyclic aromatic hydrocarbons (p-PAHs), an indicator of brown carbon (BrC), showed significant UV-absorbing ability. The average BC and p-PAHs concentrations were 3.8 and 87.6 ng m−3, respectively, at the roadside, but were only 1.5 and 18.1 ng m−3 at the ambient site, suggesting BC and p-PAHs concentrations heavily driven by traffic emissions. In contrast, PM2.5 UV light absorption coefficients (babs-BrC,370nm) at the ambient site (4.2 Mm−1) and at the roadside site (4.1 Mm−1) were similar, emphasizing that particle aging processes enhanced UV light-absorbing properties, a conclusion that was also supported by the finding that the Absorption Ångström coefficient (AAC) value at UV wavelengths (AAC_UV band) at the ambient site were ∼1.7 times higher than that at the roadside. Both aqueous reaction and photochemically produced secondary organic aerosol (SOA) for ambient aerosols contributed to the peak values of babs-BrC,370nm in ambient particles at midnight and around noon, highlighting that secondary BrC had different sources and particle aging in the atmosphere affected BrC and BC properties and related aerosol light absorption.

Characteristics of the Size Distribution of Water Soluble Inorganic Ions in Sanya, Hainan

Size-resolved filter samples were collected in Sanya every other week from June 2012 to May 2014. The mass concentrations of water-soluble inorganic ions, including anions (Cl-, NO3-, SO42-) and cations (Na+, NH4+, K+, Mg2+, Ca2+) were measured by ion chromatography. The results showed that the total concentrations of measured water-soluble inorganic ions were (8.91±7.27) and (11.34±9.37) μg·m-3 in PM2.1 and PM2.1-9, respectively. In PM2.1, SO42- and NH4+ comprised 72.2% of all water-soluble inorganic ions, while in PM2.1~9, Cl-, Ca2+ and Na+ comprised 67.6% of all water-soluble inorganic ions. In PM2.1, the total concentrations of water-soluble inorganic ions had highest concentrations in winter and lowest concentrations in summer. In PM2.1~9, the total concentrations of water-soluble inorganic ions presented the highest concentrations in summer. SO42- and NH4+ showed bimodal size distributions and the peaks in the fine mode shifted from 0.43-0.65 μm in spring, summer and autumn to 0.65-1.1 μm in winter. NO3-, Na+, Cl-, Ca2+ and Mg2+ were unimodal with the peaks in the coarse mode of 4.7-9.0 μm. K+ showed bimodal size distribution with the fine mode at 0.43-0.65 μm and the coarse mode at 4.7-5.8 μm. PCA analysis showed that water-soluble inorganic ions were mainly affected by the secondary formation, sea salt and soil particles or falling dust.

Mass Concentration and Size-Distribution of Atmospheric Particulate Matter in an Urban Environment

To investigate the ambient mass concentration, size-distribution and temporal variability of atmospheric particulate matter (PM), a long-term monitoring campaign was undertaken at an urban background site in Como, Northern Italy, from May 2015 to March 2016. A 13-stage Low Pressure Impactor (DLPI) was used for the collection of size-segregated particulates in the 0.028-10 μm size range. The results revealed a good level of agreement between DLPI and a co-located Harvard-type PM_(2.5) Impactor, allowing them to be classified as comparable and characterized by a reciprocal predictability. The PM concentration levels varied greatly between the different 5-days monitoring sessions, with higher mean mass concentrations during the heating season. Appreciable seasonal differences were found for particles between 0.15 and 1.60 μm that, on average, registered concentration levels 3.5 times higher during the heating season (mean: 28.2 μg m^(-3); median: 24.4 μg m^(-3)) compared to the non-heating season (mean: 8.3 μg m^(-3); median: 7.6 μg m^(-3)). No relevant and significant differences were detected for the coarser ranges (＞ 1.60 μm). Temporal variabilities were influenced by typical PM urban sources (e.g., household heating, traffic), that significantly affected fine and submicrometer particles, and were related to meteorological factors. Ambient air particles exhibited a trimodal distribution: a first and sharp peak more pronounced during the heating season was identified between 0.3 and 0.5 μm and two other slight peaks in the coarse mode were centered on approximately 3 and 8 μm. No relevant differences were found in the shape of the size-distribution between the two investigated seasons. The mean PM_(2.5) (22.4 μg m^(-3)) and PM_(10) (27.7 μg m^(-3)) concentrations monitored in the study area exceeded the annual Air Quality Guideline Values (respectively equal to 10 μg m^(-3) and 20 μg m^(-3)) established by the World Health Organization.