Characterization of carbonaceous particles by single particle aerosol mass spectrometer in the urban area of Chengdu, China.

Carbonaceous particles are an important chemical component of atmospheric fine particles. In this study, a single particle aerosol mass spectrometer was used to continuously measure the carbonaceous particles in Chengdu, one of the megacities most affected by haze in China, from January 22 to March 3, 2021. During the observation period, the average mass concentration of PM2.5 was 62.3 ± 37.2 µg m-3, and the emissions from mobile sources were more prominent. Carbonaceous particles accounted for 68.6% of the total particles and could be classified into 10 categories, with elemental carbon (EC) mixed with sulfate (EC-S) particles making the highest contribution (33.1%). EC particles rich in secondary components and organic carbon (OC) particles rich in secondary component exhibited different diurnal variations, suggesting different sources and mixing mechanisms. From "excellent" to "polluted" days, the contributions of EC-S, EC mixed with sulfate and nitrate (EC-SN) and OC mixed with EC (OC-EC) particles increased by 9.8%, 4.5% and 6.6%, respectively, and thus these particles are key targets for future pollution control. The potential source contribution of the southwest area was stronger than that of other areas, and the potential contribution of regional transport to EC-related particles was stronger than to OC-related particles. Most particles were highly mixed with sulfate or nitrate, and the level of secondary mixing further enhanced as pollution worsened.

An electrochlorination process integrating enhanced oxidation of phosphonate to orthophosphate and elimination: Verification of matrix chloridion-induced oxidation mechanism.

Phosphonate used as scale inhibitor is a non-negligible eutrophic contaminant in corresponding polluted waters. Besides, its conversion to orthophosphate (ortho-P) is a precondition for realizing bioavailable phosphorus recovery. Due to the feeble degradation efficiency with less than 30 % from classical Fenton commonly used in industrial wastewater treatment and itself vulnerable to strong inhibition interference of matrix chloride ions, we proposed an electrochemical approach to transform the native salt in the solution into oxidizing substances, sort of achieving beneficial utilization of matrix waste, and enhanced the ortho-P conversion rate of 1-Hydroxyethane-1,1-diphosphonic acid (HEDP) to 89.2 % (± 3.6 %). In electrochlorination system, it was found that HEDP rapidly complexed with Fe(II) and then coordinated in-situ Fe(III) to release free HEDP via intramolecular metal-ligand electron transfer reaction. The subsequent degradation mainly rooted in the oxidation of pivotal reactive species HClO, FeIVO2+ and 1O2, causing C-P and CC bonds to fracture in sequence. Eventually the organically bound phosphorus of HEDP was recovered as ortho-P. This study acquainted the audiences with the rare mechanism of chloridion-triggered HEDP degradation under electrochemical way, as well as offered a feasible technology for synchronous transformation of organically bound phosphorus to ortho-P and elimination from phosphonates.

Interannual evolution of the chemical composition, sources and processes of PM2.5 in Chengdu, China: Insights from observations in four winters.

The air quality in China has improved significantly in the last decade and, correspondingly, the characteristics of PM2.5 have also changed. We studied the interannual variation of PM2.5 in Chengdu, one of the most heavily polluted megacities in southwest China, during the most polluted season (winter). Our results show that the mass concentrations of PM2.5 decreased significantly year-by-year, from 195.8 ± 91.0 µg/m3 in winter 2016 to 96.1 ± 39.3 µg/m3 in winter 2020. The mass concentrations of organic matter (OM), SO42-, NH4+ and NO3- decreased by 49.6%, 57.1%, 49.7% and 28.7%, respectively. The differential reduction in the concentrations of chemical components increased the contributions from secondary organic carbon and NO3- and there was a larger contribution from mobile sources. The contribution of OM and NO3- not only increased with increasing levels of pollution, but also increased year-by-year at the same level of pollution. Four sources of PM2.5 were identified: combustion sources, vehicular emissions, dust and secondary aerosols. Secondary aerosols made the highest contribution and increased year-by-year, from 40.6% in winter 2016 to 46.3% in winter 2020. By contrast, the contribution from combustion sources decreased from 14.4% to 8.7%. Our results show the effectiveness of earlier pollution reduction policies and emphasizes that priority should be given to key pollutants (e.g., OM and NO3-) and sources (secondary aerosols and vehicular emissions) in future policies for the reduction of pollution in Chengdu during the winter months.

Inactivation of Escherichia Coli by mixed-valent nanoparticles in-situ generated during Fe electrocoagulation.

Electrocoagulation (EC) is promising for the removal of chemical and microbial contaminants. Although the removal of pathogens from wastewater is efficient by conventional Fe-EC in the presence of dissolved oxygen (DO), the non-inactivated pathogens in the sediment still have a risk. Herein, the inactivation of Escherichia coli (E. coli) with the mixed-valent iron nanoparticles, magnetite and green rust (GR), in-situ generated from Fe-EC process in the absence of DO was investigated. The inactivation efficiency was significantly higher with magnetite (4.7 log cells) and GR (3.2 log cells) compared with FeOOH (0.7-1.7 log cells) generated at 50 mA in 10 min. The unstable in-situ generated magnetite with positive charges was prone to adsorb onto E. coli, damaging the cell membrane, inactivating the bacteria. The unstable in-situ generated GR was prone to coagulate with E. coli, delivering Fe2+ into the cell and inducing the generation of endogenous ROS, inactivating the bacteria. Fe-EC in the absence of DO was proved to be efficient for the inactivation of E. coli (4.2-4.3 log cells) in real wastewater. These findings identified the ignored inactivation effect and mechanism of E. coli with magnetite and GR generated in situ from Fe-EC process, which will provide theoretical support for real applications.

Finding Needles in the Haystack: Strategies for Uncovering Noncoding Regulatory Variants.

Despite accumulating evidence implicating noncoding variants in human diseases, unraveling their functionality remains a significant challenge. Systematic annotations of the regulatory landscape and the growth of sequence variant data sets have fueled the development of tools and methods to identify causal noncoding variants and evaluate their regulatory effects. Here, we review the latest advances in the field and discuss potential future research avenues to gain a more in-depth understanding of noncoding regulatory variants.

Characterization of water-soluble brown carbon in atmospheric fine particles over Xi'an, China: Implication of aqueous brown carbon formation from biomass burning.

Brown carbon (BrC) aerosols can affect not only the climate but also human health, however, the light absorption, chemical compositions, and formation mechanisms of BrC are still uncertain, which leads to uncertainties in the accurate estimation of its climate and health impacts. In this study, highly time - resolved brown carbon (BrC) in fine particles was investigated in Xi'an using offline aerosol mass spectrometer analysis. The light absorption coefficient (babs365) and mass absorption efficiency (MAE365) at 365 nm of water-soluble organic aerosol (WSOA) generally increased with oxygen-to-carbon (O/C) ratios, indicating that oxidized OA could have more impacts on BrC light absorption. Meanwhile, the light absorption appeared to increase generally with the increases of nitrogen-to-carbon (N/C) ratios and water-soluble organic nitrogen; strong correlations (R of 0.76 for CxHyNp+ and R of 0.78 for CxHyOzNp+) between babs365 and the N - containing organic ion families were observed, suggesting that the N - containing compounds are the effective BrC chromophores. babs365 correlated relatively well with BBOA (r of 0.74) and OOA (R of 0.57), but weakly correlated with CCOA (R of 0.33), indicating that BrC in Xi'an was likely to be associated with biomass burning and secondary sources. A multiple linear regression model was applied to apportion babs365 to contributions of different factors resolved from positive matrix factorization on water-soluble organic aerosols (OA) and obtained MAE365 values of different OA factors. We found that biomass-burning organic aerosol (BBOA) dominated the babs365 (48.3 %), followed by oxidized organic aerosol (OOA, 33.6 %) and coal combustion organic aerosol (CCOA, 18.1 %). We further observed that nitrogen-containing organic matter (i.e., CxHyNp+ and CxHyOzNp+) increased with the increase of OOA/WSOA and the decrease of BBOA/WSOA, especially under high ALWC conditions. Our work offered proper observation evidence that BBOA is oxidized through the aqueous formation to produce BrC in Xi'an, China.

A multiscale functional map of somatic mutations in cancer integrating protein structure and network topology.

A major goal of cancer biology is to understand the mechanisms underlying tumorigenesis driven by somatically acquired mutations. Existing computational approaches focus on either scoring the pathogenicity of mutations or characterizing their effects at specific scales. Here, we established a unified computational framework, NetFlow3D, that systematically maps the multiscale mechanistic effects of somatic mutations in cancer. The establishment of NetFlow3D hinges upon the Human Protein Structurome, a complete repository we first compiled that incorporates the 3D structures of every single protein as well as the binding interfaces for all known PPIs in humans. The vast majority of 3D structural information was resolved by recent deep learning algorithms. By applying NetFlow3D to 415,017 somatic protein-altering mutations in 5,950 TCGA tumors across 19 cancer types, we identified 1,656 intra- and 3,343 inter-protein 3D clusters of mutations throughout the Human Protein Structurome, of which ~50% would not have been found if using only experimentally-determined protein structures. These 3D clusters have converging effects on 377 cellular subnetworks. Compared to canonical PPI network analyses, NetFlow3D achieved a 5.5-fold higher statistical power for identifying significantly dysregulated subnetworks. The majority of identified subnetworks were previously obscured by the overwhelming background noise of non-clustered passenger mutations, including portions of non-canonical PRC1, mediator complex, MCM2-7 complex, neddylation of cullins, complement system, TRiC, etc. NetFlow3D and our pan-cancer results can be accessed from http://netflow3d.yulab.org. This work shows that mapping how individual mutations act across scales requires the integration of their local spatial organization on protein structures and their global topological organization in the PPI network.

Transcriptional and metabolic responses of apple to different potassium environments.

Potassium (K) is one of the most important macronutrients for plant development and growth. The influence mechanism of different potassium stresses on the molecular regulation and metabolites of apple remains largely unknown. In this research, physiological, transcriptome, and metabolite analyses were compared under different K conditions in apple seedlings. The results showed that K deficiency and excess conditions influenced apple phenotypic characteristics, soil plant analytical development (SPAD) values, and photosynthesis. Hydrogen peroxide (H2O2) content, peroxidase (POD) activity, catalase (CAT) activity, abscisic acid (ABA) content, and indoleacetic acid (IAA) content were regulated by different K stresses. Transcriptome analysis indicated that there were 2,409 and 778 differentially expressed genes (DEGs) in apple leaves and roots under K deficiency conditions in addition to 1,393 and 1,205 DEGs in apple leaves and roots under potassium excess conditions, respectively. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment showed that the DEGs were involved in flavonoid biosynthesis, photosynthesis, and plant hormone signal transduction metabolite biosynthetic processes in response to different K conditions. There were 527 and 166 differential metabolites (DMAs) in leaves and roots under low-K stress as well as 228 and 150 DMAs in apple leaves and roots under high-K stress, respectively. Apple plants regulate carbon metabolism and the flavonoid pathway to respond to low-K and high-K stresses. This study provides a basis for understanding the metabolic processes underlying different K responses and provides a foundation to improve the utilization efficiency of K in apples.

Transcription factors MhDREB2A/MhZAT10 play a role in drought and cold stress response crosstalk in apple.

Drought and cold stresses seriously affect tree growth and fruit yield during apple (Malus domestica) production, with combined stress causing injury such as shoot shriveling. However, the molecular mechanism underlying crosstalk between responses to drought and cold stress remains to be clarified. In this study, we characterized the zinc finger transcription factor ZINC FINGER OF ARABIDOPSIS THALIANA 10 (ZAT10) through comparative analysis of shoot-shriveling tolerance between tolerant and sensitive apple rootstocks. MhZAT10 responded to both drought and cold stresses. Heterologous expression of MhZAT10 in the sensitive rootstock 'G935' from domesticated apple (Malus domestica) promoted shoot-shriveling tolerance, while silencing of MhZAT10 expression in the tolerant rootstock 'SH6' of Malus honanensis reduced stress tolerance. We determined that the apple transcription factor DEHYDRATION RESPONSE ELEMENT-BINDING PROTEIN 2A (DREB2A) is a direct regulator activating the expression of MhZAT10 in response to drought stress. Apple plants overexpressing both MhDREB2A and MhZAT10 genes exhibited enhanced tolerance to drought and cold stress, while plants overexpressing MhDREB2A but with silenced expression of MhZAT10 showed reduced tolerance, suggesting a critical role of MhDREB2A-MhZAT10 in the crosstalk between drought and cold stress responses. We further identified drought-tolerant MhWRKY31 and cold-tolerant MhMYB88 and MhMYB124 as downstream regulatory target genes of MhZAT10. Our findings reveal a MhDREB2A-MhZAT10 module involved in crosstalk between drought and cold stress responses, which may have applications in apple rootstock breeding programs aimed at developing shoot-shriveling tolerance.

[Characteristics of Carbonaceous Species in PM2.5 in Chengdu Under the Background of Emission Reduction].

The Air Pollution Prevention and Control Action Plan and Three-year Plan on Defending the Blue Sky promulgated by the State Council of the People's Republic of China have played an important role in the overall improvement of air quality in China. However, few studies have evaluated the implementation effects of these two policies in Sichuan Basin and the new characteristics of PM2.5 chemical components after the implementation of these policies. The key periods for evaluating the implementation effects of these two pollution reduction policies are 2017 and 2020, respectively. In order to study the atmospheric PM2.5 and carbonaceous species in Chengdu during these two periods, this study sampled the PM2.5 in Chengdu from October 2016 to July 2017 and December 2020, respectively, and the organic carbon (OC) and elemental carbon (EC) were analyzed. The results showed that the annual ρ(PM2.5) from 2016-2017 in Chengdu was (114.0±76.4) µg·m-3. The maximum value of the ρ(PM2.5) appeared in winter[(193.3±98.5) µg·m-3], and the minimum value appeared in spring[(73.8±32.3) µg·m-3]. By contrast, the ρ(PM2.5) in winter decreased significantly in 2020, with a value of (96.0±39.3) µg·m-3. The annual ρ(OC) and ρ(EC) from 2016-2017 were (21.1±16.4) µg·m-3 and (1.9±1.3) µg·m-3, which accounted for 18.5% and 1.7% of the PM2.5 mass, respectively. The seasonal variation characteristic of ρ(OC) was:winter[(40.6±21.5) µg·m-3]>autumn[(17.0±7.0) µg·m-3]>summer[(14.4±3.9) µg·m-3]>spring[(12.6±6.0) µg·m-3], whereas the ρ(EC) in the four seasons were close, ranging from 1.3 to 2.4 µg·m-3. The annual ρ(SOC) was (9.4±9.1) µg·m-3, which accounted for 44.5% of the OC mass. Compared with that in winter 2016, the ρ(OC) decreased by 52.7% in winter 2020, whereas the ρ(EC) increased by 26.1%. With the aggravation of pollution, the change trends of carbon species and their contributions were different. Compared with that in winter 2016, the variation in the contribution of OC with the aggravation of pollution in winter 2020 was more stable, whereas the proportion of SOC increased more obviously. There were obvious differences in the direction of air masses and the potential source area of pollutants in each season. Although there was no significant change in the direction of air masses in winter 2020 compared with those in winter 2016, the pollutant concentrations corresponding to each cluster decreased significantly, and the potential source area of pollutants expanded significantly to the eastern area.

Nano-Sized Antioxidative Trimetallic Complex Based on Maillard Reaction Improves the Mineral Nutrients of Apple (Malus domestica Borkh.).

The metallic complex is widely used in agricultural applications. Due to the oxidation of the metal and environmental unfriendliness of ligand, maintaining an efficient mineral supply for plants without causing environmental damage is difficult. Herein, an antioxidative trimetallic complex with high stability was synthesized by interacting Ca2+, Fe2+, and Zn2+ with the biocompatible ligands from the Maillard reaction. The composite structure elucidation was carried out by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR). Thermal stability was measured by thermogravimetric (TG). Antioxidative activities were evaluated by ferric reducing antioxidant power and radical scavenging activity assays. The three metals were successfully fabricated on the Maillard reaction products (MRPs) with contents of Ca (9.01%), Fe (8.25%), and Zn (9.67%). Microscopy images revealed that the three metals were uniformly distributed on the MRPs with partial aggregation of <30 nm. FTIR and XPS results revealed that the metals were interacted with MRPs by metal-O and metal-N bonds. TG and antioxidative activity assays showed that the trimetallic complex meets the requirements of thermodynamics and oxidation resistance of horticultural applications. Additionally, the results of the exogenous spraying experiment showed that the trimetallic complex significantly increased the mineral contents of the "Fuji" apple. By treatment with the complex, the concentrations of Ca, Fe, and Zn were increased by 85.4, 532.5, and 931.1% in the leaf; 16.0, 225.2, and 468.6% in the peel; and 117.6, 217.9, and 19.5% in the flesh, respectively. The MRP-based complexes offered a higher growth rate of the mineral content in apples than ones based on sugars or amino acids. The results of the spraying experiment carried out in 2 years show that the method has high reproducibility. This study thus promotes the development of green metallic complexes and expands the scope of agrochemical strategy.

Retraction Notice to: LINC00472 Acts as a Tumor Suppressor in NSCLC through KLLN-Mediated p53-Signaling Pathway via MicroRNA-149-3p and MicroRNA-4270.

[This retracts the article DOI: 10.1016/j.omtn.2019.06.003.].

Methylome and transcriptome analyses of three different degrees of albinism in apple seedlings.

BACKGROUND: Leaf colour mutations are universally expressed at the seedling stage and are ideal materials for exploring the chlorophyll biosynthesis pathway, carotenoid metabolism and the flavonoid biosynthesis pathway in plants. RESULTS: In this research, we analysed the different degrees of albinism in apple (Malus domestica) seedlings, including white-leaf mutants (WM), piebald leaf mutants (PM), light-green leaf mutants (LM) and normal leaves (NL) using bisulfite sequencing (BS-seq) and RNA sequencing (RNA-seq). There were 61,755, 79,824, and 74,899 differentially methylated regions (DMRs) and 7566, 3660, and 3546 differentially expressed genes (DEGs) identified in the WM/NL, PM/NL and LM/NL comparisons, respectively. CONCLUSION: The analysis of the methylome and transcriptome showed that 9 DMR-associated DEGs were involved in the carotenoid metabolism and flavonoid biosynthesis pathway. The expression of different transcription factors (TFs) may also influence the chlorophyll biosynthesis pathway, carotenoid metabolism and the flavonoid biosynthesis pathway in apple leaf mutants. This study provides a new method for understanding the differences in the formation of apple seedlings with different degrees of albinism.

Exogenous application of acetic acid enhances drought tolerance by influencing the MAPK signaling pathway induced by ABA and JA in apple plants.

The external application of acetic acid (AA) has been shown to improve drought survival in plants, such as Arabidopsis, rice, maize, wheat, rapeseed and cassava, and the application of AA also increased drought tolerance in perennial woody apple (Malus domestica) plants. An understanding of AA-induced drought tolerance in apple plants at the molecular level will contribute to the development of technology that can be used to enhance drought tolerance. In this study, the morphological, physiological and transcriptomic responses to drought stress were analyzed in apple plants after watering without AA (CK), watering with AA (AA), drought treatment (D) and drought treatment with AA (DA). The results suggested that the AA-treated apple plants had a higher tolerance to drought than water-treated plants. Higher levels of chlorophyll and carotenoids were found under the DA conditions than under D stress. The levels of abscisic acid (ABA), jasmonic acid (JA) and methyl jasmonate were increased in AA-treated apple plants. Transcriptomic profiling indicated the key biological pathways involved in metabolic processes, mitogen-activated protein kinase (MAPK) signaling, plant hormone signal transduction and the biosynthesis of secondary metabolites in response to different drought conditions. The 9-cis-epoxycarotenoid dioxygenase, (9S,13S)-cis-oxophytodienoic acid reductase, allene oxide synthase, allene oxide cyclase and lipoxygenase genes participate in the synthase of ABA and JA under drought and AA treatments. Collectively, the results showed that external application of AA enhanced drought tolerance in apple plants by influencing the ABA- and JA-induced MAPK signaling pathways. These data indicated that the application of AA in plants is beneficial for enhancing drought tolerance and decreasing growth inhibition in agricultural fields.

[Characteristics of Water-soluble Ions in an Autumn Haze Process in the Southern Sichuan Urban Agglomeration After the Implementation of China's Air Pollution Prevention and Control Action Plan].

To investigate the PM2.5 pollution in the southern Sichuan urban agglomeration after the implementation of China's Air Pollution Prevention and Control Action Plan (APPCAP), PM2.5 samples were simultaneously collected in four cities (Neijiang, Zigong, Yibin, and Luzhou) from November 7 to 19, 2018. The pollution characteristics of PM2.5 and main water-soluble ions were analyzed in combination with the synoptic situation, and the influence of regional transport on atmospheric pollution was also discussed in this study. The results showed that the mean ρ(PM2.5) in this region was (67.2±38.3) µg·m-3, being highest in Luzhou and lowest in Neijiang. The proportion of SNA (SO42-, NO3-, and NH4+) in PM2.5 was 33.3%, among which NO3- was dominant. From the intermediate stage (2015) to the end(2018) of the implementation of APPCAP, ρ(PM2.5) values were increased by 13.8%, 47.2%, and 69.1% in Neijiang, Yibin, and Luzhou, respectively, though unchanged in Zigong. Due to the significant reduction in ρ(SO2) but slight decrease or increase in ρ(NO2), as well as the lack of controlling NH3 emissions, from 2015 to 2018, ρ(NO3-) had increased by 36.7%-116.0%, whereas ρ(SO42-) decreased by 19.8%-40.2%, and ρ(NH4+) changed slightly in four cities. On haze days, the nitrogen oxidation rate (NOR) increased by 60.0%-118.2%, whereas the sulfur oxidation rate (SOR) increased slightly or decreased, leading to a significant increase in ρ(NO3-) (2.7-3.0 times that on clean days) and NO3-/SO42- mass ratios (1.7-1.9 on haze days). These values indicated that the secondary formation of nitrate was the dominant chemical mechanism in this haze process. On haze days, the PM2.5 pollution in this region was mainly affected by the regional transport within Sichuan Basin, particularly by the northeasterly air masses passing through Chongqing.

Bioremediation of stainless steel pickling sludge through microbially induced carbonate precipitation.

In this study, microbial induce carbonate precipitation (MICP) was introduced to immobilize chromium (Cr) in stainless steel pickling sludge (SSPS). Two methods were utilized to conduct the MICP process - Bacteria lysis liquor (BLL)-based MICP and bacteria-based MICP. BLL was obtained by breaking the cell walls with ultrasonic treatment. The urea hydrolyzation test illustrated that the BLL was better than bacteria solution. Both the treatments of bacteria lysis liquor-based MICP and bacteria-based MICP process can effectively entrap the Cr into mineral lattices, that reduce the potential environmental risk of SSPS. With 30 g/L urea and 7 days' treatment, BLL-based MICP presented better immobilization performance than bacteria-based MICP by lowering the bacteria concentration (OD600) from 0.8 to 0.7. The excellent biosorption of BLL contributed to Cr removal. Nevertheless, the addition of calcium (Ca) significantly enhanced the immobilization performance of bacteria-based MICP process rather than BLL-based MICP process. pH-dependent leaching tests illustrated the leaching of Cr followed an amphoteric pattern, while the leaching of Ni and Ca followed the cation pattern. Geochemical modeling revealed that the leaching of Cr from bio-mineralized products was solubility-controlled by Cr(OH)3 and Cr2O3.

Characterization and source identification of submicron aerosol during serious haze pollution periods in Beijing.

Submicron aerosol is of extensive concern not only due to its significant impact on air quality but also because it is detrimental to human health. In this study, we investigated the characteristics, sources and chemical processes of submicron aerosol based on real-time online measurements of submicron aerosols (NR-PM1) during December 2015 at an urban site in Beijing. The average mass concentration of NR-PM1 was 92.5±84.9 µg/m3, the hourly maximum was 459.1 µg/m3 during the entire observation. The organic aerosol (OA) (55%) was the largest contributor to NR-PM1. The average mass concentration of PAHs was 0.217±0.247 µg/m3, exhibiting the highest concentration at night and the lowest levels in the daytime. The average mass concentration of organic nitrate was 2.52±2.36 µg/m3 and that of inorganic nitrate was 7.62±8.22 µg/m3, accounting for 36% and 64%, respectively, of the total nitrate mass. Positive matrix factorization (PMF) differentiated the OA into five chemical components including LV-OOA, SV-OOA, COA, HOA and CCOA, accounting for 22%, 16%, 13%, 25% and 24% respectively, of the total OA. The average NR-PM1 mass concentration on the heavy polluted days (HPD) was 182.8±70.2 µg/m3, which was approximately 9 times that on clean days (CD). The enhanced secondary formation of SNA was evident on HPD, especially the rapid increase of sulfate (23%) and nitrate (19%).

Particle composition, sources and evolution during the COVID-19 lockdown period in Chengdu, southwest China: Insights from single particle aerosol mass spectrometer data.

In order to investigate the effects of the Coronavirus Disease 2019 (COVID-19) lockdown on air quality in cities in southwest China, a single particle aerosol mass spectrometer (SPAMS) and other online equipments were used to measure the air pollution in Chengdu, one of the megacities in this area, before and during the lockdown period. It was found that the concentrations of fine particulate matter (PM2.5), nitric oxide (NO), nitrogen dioxide (NO2), sulfur dioxide (SO2) and carbon monoxide (CO) decreased by 38.6%, 77.5%, 47.0%, 35.1% and 14.1%, respectively, while the concentration of ozone (O3) increased by 57.5% from the time before to the time during lockdown. All particles collected during the study period could be divided into eight categories: biomass burning (BB), coal combustion (CC), vehicle emissions (VE), cooking emissions (CE), Dust, K-nitrate (K-NO3), K-sulfate (K-SO4) and K-sulfate-nitrate (K-SN) particles, and their contributions changed significantly after the beginning of lockdown. Compared to before lockdown, the contribution of VE particles experienced the largest reduction (by 14.9%), whereas the contributions of BB and CE particles increased by 7.0% and 7.3%, respectively, during the lockdown period. Regional transmission was critical for pollution formation before lockdown, whereas the pollution that occurred during the lockdown period was caused mainly by locally emitted particles (such as VE, CE and BB particles). Weighted potential source contribution function (WPSCF) analysis further verified and emphasized the difference in the contribution of regional transmission for pollution formation before and during lockdown. In addition, the potential source area and intensity of the particles emitted from different sources or formation mechanisms were quite different.

Characteristics of fine particulate matter (PM2.5) at Jinsha Site Museum, Chengdu, China.

Air pollution is a serious threat to ancient sites and cultural relicts. In this study, we collected indoor and outdoor PM2.5 samples and individual particles at the Exhibition Hall of Jinsha Site Museum in June 2020, and then the chemical components, sources, morphology, and mixing state of the fine particulate matter were analyzed. Our results show that the indoor and outdoor PM2.5 concentrations at the Exhibition Hall were 33.3±6.6 and 39.4±11.4 µg m-3, respectively. Although the indoor and outdoor concentrations of OC and EC were close, the proportion of secondary organic carbon in OC outdoor (33%) was higher than that indoor (27%). The PM2.5 was alkaline both indoors and outdoors, and the outdoor alkalinity was stronger than the indoor alkalinity. SNA (SO42-, NO3-, and NH4+) was the dominant component in the water-soluble inorganic ions; Na+, Mg2+, and Ca2+ were well correlated (R2> 0.9), and Cl- and K+ were also highly correlated (R2> 0.8). Enrichment factor analysis showed that Cu (indoor) and Cd were the main anthropogenic elements and that Cd was heavily enriched. Principal components analysis showed that the main sources of PM2.5 at Jinsha Site Museum were motor vehicles, dust, secondary sources, and combustion sources. The individual particles were classified as organic matter, S-rich, soot, mineral, and fly ash/metal particles, and most of these particles were internally mixed with each other. At last, we proposed pollution control measures to improve the air quality of museums and the preservation of cultural relicts.

Interannual evolution of elemental carbon-containing particles in winter in the atmosphere of Chengdu, China.

As one of the important components of PM2.5, elemental carbon (EC) particles could quickly mix with other organic or inorganic species after entering the atmosphere, which directly affected its climate and environmental effects and impact on human health. In order to study the mixture and evolution of EC particles in the atmosphere, this study used single particle aerosol mass spectrometry to measure the EC-containing particles in three winters (2016/17, 2018/19 and 2019/20) in Chengdu, one of the most polluted megacities in China. The results showed that the average mass concentrations of PM2.5 in the three winters were 121 ± 58 µg m-3, 90 ± 32 µg m-3 and 79 ± 38 µg m-3, respectively, and the mass ratios of PM2.5/PM10 were 0.71, 0.78 and 0.78, respectively. EC-containing particles accounted for 40.7%-54.7% of all particles and could be divided into six categories: EC-dust (EC-D), fresh EC (ECf), EC-organic carbon (EC-OC), EC-nitrate (EC-N), EC-sulfate (EC-S) and EC-sulfate-nitrate (EC-SN). From winter 2016/17 to 2019/20, the contributions of EC-N and EC-OC particles increased, while the contributions of EC-S and EC-SN particles decreased. Meanwhile, EC-N particles became increasingly important for the formation of heavy pollution. Photochemical and liquid-phase processes dominated the formation of EC-N and EC-S particles, respectively, while the dominant formation mechanism of EC-SN particles changed from photochemical to liquid-phase processes from winter 2016/17 to 2019/20. Total EC and EC-S particles in Chengdu were mainly transported from the east and southeast areas to Chengdu, while ECf particles mainly derived from local emissions. Compared with the previous two winters, the potential source areas of the EC-containing particles in winter 2019/20 reduced significantly. These findings provide new insight into the atmospheric behavior of urban particles and are important reference for the study of EC particles in other regions in the world, especially in urban areas.