[Analysis of a Typical Ozone Pollution Process in Guangzhou in Winter].

This study focused on an ozone pollution event occurring in winter (January) in Guangzhou. Various influencing factors were analyzed, including various atmospheric trace gases, meteorological conditions during the whole pollution process, as well as the characteristics of the main O3 precursor volatile organic compounds (VOCs). The main sources of VOCs and the O3 formation regime were analyzed using an array of tools:the ozone potential formation (OFP), positive matrix factorization (PMF) model, and empirical kinetic modeling approach (EKMA) curve. Feasible strategies for O3 control were suggested. The results showed that O3 and NO2 exceeded the corresponding standards in this winter pollution event, when the concentrations of PM10 and PM2.5 were also high, differing from the air pollution characteristics in summer and autumn. Low boundary layer height (<75 m) and high atmospheric stability at night exacerbated the accumulation of ozone precursors and fine particles. Meteorological conditions such as the increased daytime temperature (5℃), stronger solar radiation (10%), and low horizontal wind speed (<1 m·s-1) favored photochemical reactions and promoted the formation of ozone and fine particles. VOCs were mainly composed of alkanes, and the proportions of alkanes and alkynes in winter were higher than those in the other seasons. Aromatics (xylenes and toluene) and propylene were the key VOCs species leading to O3 formation. The main VOCs sources were vehicle exhaust (22.4%), solvent usage (20.5%), and industrial emissions (17.9%); however, the source with highest OFP was identified as solvent usage. O3 formation in this event was in the VOCs-limited regime, and reducing O3 precursors in the VOCs/NOx ratio of 3:1 was effective and feasible for O3 control. This study explored the causes of an O3 pollution event in winter, which will serve as reference for the synergistic control of O3 and PM2.5 in heavy pollution seasons.

[Influence of Burning Fireworks on the Atmosphere During the Spring Festival in Guangzhou in 2020].

Twenty-one air quality monitoring stations including four with single particle aerosol mass spectrometers (SPAMS) were used to observe air quality and aerosol particulates during the 2020 Spring Festival (from January 21 to 28) in Guangzhou. The effect of burning fireworks on the atmosphere of Guangzhou and its eleven administrative regions was examined, and the chemical composition of firework particles was detected and analyzed by single particle aerosol mass spectrometry. The results show that the burning of fireworks had a significant impact on air quality in the discharge area and the prohibited discharge area. The concentrations of PM2.5, PM10, and SO2 sharply increased in Guangzhou on New Year's Eve. Air quality in Zengcheng District, Baiyun District, Huangpu District, and some areas of Tianhe District was also affected by the concentrated burning of fireworks on January 25 between 01:00 and 06:00. A method of fireworks tracing based on SPAMS using Al+ as a tracer was established with a time resolution of 5 min. The main particle types emitted by the burning fireworks were levoglucan, potassium-rich, and mineral. These particles were well mixed with nitrate, but this was not conducive to the formation of ammonium.

Complete chloroplast genomes of three important species, Abelmoschus moschatus, A. manihot and A. sagittifolius: Genome structures, mutational hotspots, comparative and phylogenetic analysis in Malvaceae.

Abelmoschus is an economically and phylogenetically valuable genus in the family Malvaceae. Owing to coexistence of wild and cultivated form and interspecific hybridization, this genus is controversial in systematics and taxonomy and requires detailed investigation. Here, we present whole chloroplast genome sequences and annotation of three important species: A. moschatus, A. manihot and A. sagittifolius, and compared with A. esculentus published previously. These chloroplast genome sequences ranged from 163121 bp to 163453 bp in length and contained 132 genes with 87 protein-coding genes, 37 transfer RNA and 8 ribosomal RNA genes. Comparative analyses revealed that amino acid frequency and codon usage had similarity among four species, while the number of repeat sequences in A. esculentus were much lower than other three species. Six categories of simple sequence repeats (SSRs) were detected, but A. moschatus and A. manihot did not contain hexanucleotide SSRs. Single nucleotide polymorphisms (SNPs) of A/T, T/A and C/T were the largest number type, and the ratio of transition to transversion was from 0.37 to 0.55. Abelmoschus species showed relatively independent inverted-repeats (IR) boundary traits with different boundary genes compared with the other related Malvaceae species. The intergenic spacer regions had more polymorphic than protein-coding regions and intronic regions, and thirty mutational hotpots (≥200 bp) were identified in Abelmoschus, such as start-psbA, atpB-rbcL, petD-exon2-rpoA, clpP-intron1 and clpP-exon2.These mutational hotpots could be used as polymorphic markers to resolve taxonomic discrepancies and biogeographical origin in genus Abelmoschus. Moreover, phylogenetic analysis of 33 Malvaceae species indicated that they were well divided into six subfamilies, and genus Abelmoschus was a well-supported clade within genus Hibiscus.

[Effect of ß-lactamase detection on reducing the incidence of antibiotic-associated diarrhea in children with severe bacterial pneumonia].

OBJECTIVE: To study the effect of ß-lactamase (BLs) detection and ß-lactam/ß-lactamase inhibitor (BL/BLI) on the incidence of antibiotic-associated diarrhea (AAD) in children with severe bacterial pneumonia. METHODS: The clinical data of the children with bacterial severe pneumonia were retrospectively studied. Of all the patients, 248 using amoxicillin/clavulanate but without BLs detection and 323 using amoxicillin (BLs negative) or amoxicillin/clavulanate (BLs positive) were used as the amoxicillin group; 208 patients using piperacillin/tazobactam but without BLs detection and 291 patients using piperacillin (BLs negative) or piperacillin/tazobactam (BLs positive) were used as the piperacillin group; and 191 patients using cefoperazone/sulbactam but without BLs detection and 341 patients using cefoperazone (BLs negative) or cefoperazone/sulbactam (BLs positive) were used as the cefoperazone group. The incidence and clinical symptoms of AAD between the undetected and detected BLs patients were compared. RESULTS: The incidences of AAD in the amoxicillin, piperacillin and cefoperazone groups without BLs detection groups were significantly higher than those in the corresponding groups with negative or positive results of BLs detection (P<0.01). The durations of diarrhea, antibiotic use and hospitalization stay in AAD patients receiving BLs detection were shorter than in those without receiving BLs detection (P<0.01). CONCLUSIONS: It is very important to detect BLs for reducing the incidence and relieving symptoms of AAD in children with severe bacterial pneumonia.

Composition analysis and anti-proliferation activity of polysaccharides from Dendrobium chrysotoxum.

Water-soluble polysaccharides (DCCP, DCPP) were extracted from the stems of Dendrobium chrysotoxum using boiling water and ultrasound. DCPP were successively purified by chromatography on DEAE-Cellulose-52 and Sephadex G-200 column, giving three major polysaccharide fractions termed DCPP-I, DCPP-I-a and DCPP-II. Among these fractions, DCPP-I-a exhibited the highest abundance (79.5%). The number-average molecular weight and weight-average molecular weight of DCPP-I-a were 67 kDa and 122 kDa, respectively. Monosaccharide components analysis indicated that DCPP-I-a were composed of xylose, glucose, galactose in a molar ratio of 1.44:6.93:12.79. Infrared spectra (IR) and (1)H NMR showed that DCPP-I-a was composed of a ß-D pyran ring with a ß-configuration. The evaluation of anti-proliferation activity suggested that DCPP-I-a and DCPP-II had a higher inhibitory effect on the SPC-A-1 cells than DCCP as determined with in vitro anti-proliferation test.