[Chemical Composition and Characterization of Nitroaromatic Compounds in Urban Areas of Shanghai].

The compositional characteristics, concentration of nitroaromatic compounds(NACs) in PM2.5 in urban Shanghai, and their correlation with gaseous precursors were investigated. A total of 39 winter and 46 summer PM2.5 samples from 2020 to 2021 were collected using a high-flow sampler and analyzed via ultra-performance liquid chromatography coupled with ESI-Orbitrap high-resolution mass spectrometry(UPLC-Orbitrap-HRMS). Quantitative analysis was performed on 12 NACs compounds, combined with backward trajectory meteorological elements, molecular composition, and classification analysis of CHON substances. The results showed that a total of 12 NACs had an average concentration in winter of 17.1 ng·m-3, which was three times higher than that in summer(5.7 ng·m-3), mainly due to air masses in winter coming primarily from the northern part of China with more biomass burning, whereas more air masses in summer came from the cleaner southeastern ocean. 4-Nitrophenol was the most abundant species of NACs in winter, whereas 4-nitrophenol(clean days) and 4-hydroxy-3-nitrobenzoic acid(polluted days) were the most abundant species in summer. Qualitative analysis based on features such as aromatic ring equivalence number(Xc), O/C, and H/C values for the identification and characterization of monocyclic and polycyclic aromatic compounds showed that CHON compounds were mainly aromatic compounds in winter and summer in urban Shanghai. The number and abundance of CHON compounds detected on PM2.5 polluted days were 2 and 1.5 times higher(winter) and 2.5 and 2 times higher(summer) than that on clean days, respectively. Comparing the analysis results of clean and polluted days in winter and summer, it was found that 80% of the CHON compounds with a relative abundance in the top 10 had O/N ≥ 3 and RDBE values between 5 and 8. The results suggest that these highly abundant CHON analogs may have had mononitro- or dinitro-substituted benzene rings. Correlation analysis between gaseous precursors and NACs indicated that oxidative reactive formation of VOCs(benzene, toluene, etc.) from anthropogenic emissions was the main source of NACs in summer. By contrast, it was influenced by a combination of biomass combustion emissions and secondary formation of oxidative NOx from anthropogenic VOCs in winter.

[Chemical Characteristics and Source Apportionment of Organic Aerosols in Urban Shanghai During Cold Season Based on High Time-resolution Measurements of Organic Molecular Markers].

Organic aerosols (OA) are closely related to the formation of both PM2.5 and O3 in the atmosphere. In this study, a thermal desorption aerosol GC/MS (TAG) online system was adopted to measure hourly concentrations of 94 total organic molecular markers in PM2.5 at an urban site in Shanghai from November 6th to December 31st, 2021. Combined with air mass cluster analysis and other online measurement data, the chemical characteristics of OA under the influence of different air masses, oxidant levels, and relative humidity (RH) levels were investigated. The results showed that OA was characterized by higher mass percentages of primary organic molecular markers (e.g., saturated fatty acids, unsaturated fatty acids, and alkanes) under the influence of local air masses. Further, high loadings of biomass burning tracers were observed in OA under the influence of long-range transported air masses. In contrast, OA impacted by marine air masses was laden with significantly higher fractions of secondary organic molecular markers, such as dicarboxylic acids and hydroxyl dicarboxylic acids, which were formed from a wide range of volatile organic precursors through photochemical and aqueous-phase processing. With the application of the positive matrix factorization (PMF) model, seven total primary source factors and five secondary source factors were resolved for PM2.5 and OA during the observation. Among them, secondary nitrate was the highest contributor to PM2.5 mass with a mass percentage of 25.2%, whereas vehicle emissions were the top contributor (24.0%) to OA mass. Primary source factors, including coal combustion, vehicle emission, and cooking emission as well as their corresponding secondary source factors (e.g., secondary nitrate, secondary organic aerosols 2, etc.) showed elevated contributions in PM2.5 and OA with the increase in PM2.5 masses, indicating that more stringent controls of local emission sources (e.g., coal combustion, vehicle emission, and cooking emission) are needed to further lower PM2.5 pollution and improve air quality in Shanghai.

[Characteristics of Nitroaromatic Compounds in PM2.5 in Urban Area of Shanghai].

Nitroaromatic compounds (NACs) are an important class of nitrogen-containing compounds in fine particles. The investigation of characteristics and seasonal variation of NACs in PM2.5 increases our knowledge about nitrogen-containing compounds and contributes to the scientific basis in formulating reduction policies of NOx in urban areas. In this study, we analyzed the chemical composition of PM2.5 samples collected from March 2018 to February 2019 in an urban location in Shanghai. A total of 2439-3695 organic molecular formulas were detected using UPLC-Orbitrap MS. Nine NACs were quantified using an internal standard method. In spring, ρ(NACs) ranged from 3.12 to 16.76 ng·m-3, and the average concentration was 9.31 ng·m-3. In summer, it ranged from 1.05 to 9.70 ng·m-3, and the average value was 4.16 ng·m-3. In autumn, it ranged from 2.87 to 36.27 ng·m-3, and its average was 9.84 ng·m-3. In winter, it ranged from 4.83 to 56.23 ng·m-3, and the average was 22.37 ng·m-3. 4-Nitrophenol accounted for more than 25% of the quantified NACs in different seasons. In summer, the concentration of 5-nitrosalicylic acid accounted for 36%, but it decreased to 19% in winter. NACs in summer mainly originated from secondary formation, as evidenced by their clear correlation with the oxidant level, whereas biomass burning became the main source of NACs in winter.

[Audit Indicators and Suggested Ranges for Data Validation of Chemical Components in Ambient PM2.5: A Case Study of the Yangtze River Delta].

Diagnostic indicators for the validation of PM2.5 compositional data were calculated, based on the monitoring results of approximately 2100 ambient samples collected in the Yangzi River Delta from 2014 to 2017. According to the results of a correlation analysis, we propose that the audit indexes of the monitoring data of PM2.5 components in ambient air should include:equivalent ratios of anion-cation charge balance(A/C), the consistency between sum of all measured components(∑species) and weighed PM2.5, the consistency between mass reconstructed PM2.5(PM2.5, reconstructed) and weighed PM2.5, the chemical consistency between elemental S and water-soluble SO42-, elemental K and water-soluble K+, and the chemical consistency of theoretical and tested NH4+. The double-sided 95% reference ranges of anion-cation equivalent balance (A/C), ∑species/PM2.5, PM2.5, reconstructed/PM2.5, S/SO42-, and K/K+ ratios were determined in terms of P2.5 and P97.5 as follows:(0.82, 1.35), (0.63, 0.94), (0.62, 1.00), (0.28, 0.50), and (0.66, 2.31). These diagnostic indicators were helpful for judging the errors of chemical component analysis and retain seasonal variation stability. In most cases, NH4+ existed in the form of NH4NO3 and (NH4)2SO4 in spring and summer. With the approach of autumn and winter, it transformed to NH4NO3, (NH4)2SO4, and NH4Cl. The results of literature verification showed the pass rate of A/C was 87.1% and the rate of other indexes was 100%, indicating that the above audit indexes we propose could be applied to not only the Yangzi River Delta but the entire country. Furthermore, there were certain conditions in applying the diagnostic indicators. The S/SO42- ratio worked well with PM2.5 ≥ 40 µg·m-3 in summer and with 60 µg·m-3 ≤ PM2.5 ≤ 140 µg·m-3 in spring, autumn, and winter. Other audit indexes were available universally in all weathers under the condition of PM2.5 ≥ 60 µg·m-3.

[Health Benefit Analyses of the Clean Air Action Plan Implementation in Shanghai].

To understand the public health benefits of the Clean Air Action Plan implemented in Shanghai from 2013-2017, the changes of the PM2.5 exposure levels and related health and economic benefits were quantitatively evaluated by using air quality numerical modeling, health risk assessment, and environmental valuation methods. The results show that the proportion of the population exposed to a mean annual PM2.5 concentration lower than or equal to 35 µg·m-3 has increased from 1.62% in the base year to 34.06% in the control year. The death risk attributable to ambient PM2.5 exposure decreased from 15.2% in the base year to 11.9% in the control year. The total health benefits are approximately 11.841 billion RMB(95% CI:5.024-17.819 billion RMB), accounting for 0.55%(95% CI:0.23%-0.82%)of Shanghai's GDP in 2013. The implementation of the action plan has a positive effect on the protection of the health of the population. Health benefits in areas with dense populations and high PM2.5 declines are more pronounced within the outer ring line of Shanghai City.

[Analysis of Non-polar Organic Compounds in PM2.5 by Rapid Thermo-desorption Method Coupled with GC/MS].

Non-polar organic compounds (NPOCs) associated with PM2.5 in the atmosphere were analyzed by automated thermo-desorption (TD) coupled with gas chromatography/mass spectrometry (TD-GC/MS). The analyses for a total of 72 NPOCs were reviewed, including 34 PAHs, one Debenzothiophene, 27 alkanes (C10-C34), 5 hopanes and 5 steranes. Through this improved TD method, operation of filter loadings, TD condition and sample introduction were optimized. The MDL were 0.01-1.0, 0.1-8.0 and 0.50-2.0 ng·m-3 for PAHs, alkanes, hopanes and steranes, respectively. Calibration curve linearities were above 0.9 for all compounds. The TD efficiencies were 95%-100% for PAHs, 81%-100% for alkanes and 83.1%-100% for hopanes and steranes. PM2.5 samples were pretreated by TD and ultrasonic extraction methods separately and analyzed by GC/MS in two laboratories. Results from these two methods were comparable, as the relative biases were less than 30% for most compounds. Analysis results of PM2.5 samples from Linan and Shanghai showed that NPOCs were higher in winter than that in summer. Alkanes were predominant among NPOCs, followed by PAHs. Source analysis by PAH characteristic ratios indicated that fossil fuel burning and coal burning were the main sources of NPOCs in the two sites during the sampling periods.

[Chemical Characterization, Spatial Distribution, and Source Identification of Organic Matter in PM2.5 in summertime Shanghai, China].

Particulate organic matter (POM) has attracted increasing attention recently due to its great contribution to fine particles (PM2.5) and complex components and sources. In the present study, 78 particulate organic compounds in PM2.5 were quantified at three sites in Shanghai during summer; these sites were located in urban (Xuhui), suburban (Qingpu), and coastal (Lin'gang) areas of the city. Accordingly, the chemical composition and spatial distribution were investigated and sources were explored based on the indicators and diagnostic ratios combined with backward trajectory. The results showed that during the period of observation, the quantified organic matter in the suburban area is about 319 ng ·m-3, close to the urban area but much higher than that of the coastal areas. Fatty acids were the largest contributors, followed by levoglucosan, polycyclic aromatic hydrocarbons (PAHs), n-alkanes, and hopanes. Source analysis based on tracer methods indicates that gasoline vehicle emissions were the main source of POM in Shanghai. Biomass burning from the northeast impacted somewhat on the urban area and western suburbs during the observation period. Terrestrial plant emissions played an important role in the source of fatty acids at Qingpu and Lin'gang, and emissions of marine phytoplankton and microorganisms were also important for fatty acids at Lin'gang. Coal combustion and motor vehicle exhaust made an important contribution to PAHs according to an analysis of diagnostic ratios. This study presented the characteristics and sources of POM in summertime Shanghai, which facilitates the development of an effective control strategy on PM2.5 pollution.

[Physiochemical Properties of the Aerosol Particles and Their Impacts on Secondary Aerosol Formation at the Background Site of the Yangtze River Delta].

The study of the sources, compositions, and formation mechanisms of pollutants at the background site is crucial for the understanding of episodic events in the Yangtze River Delta (YRD). Secondary species are major components of PM2.5 particles. In this work, the compositions and concentrations of organic matter and secondary organic aerosol (SOA) at a background site of the YRD region were determined. The acidity and liquid water content of aerosol particles were modeled to investigate the impact of the physicochemical properties of aerosol particles on the formation of secondary species. The annual mean PM2.5 concentration in Chunan is 33 µg·m-3, with major contributions from inorganic sulfate (19%), nitrate (15%), ammonium (12%), and organic matter (19%). Nitrate is mainly locally formed, while sulfate is more affected by regional transport, except in winter. We found that the particles at the background site of the YRD have a high acidity and no seasonal variation was observed. The SOA formation at the background site of the YRD is enhanced by the liquid water content of the aerosol in spring, while it is more affected by the concentration of the oxidant, that is, O3, in summer. The contribution of SOA to PM2.5 in summer is as high as 40%.

[Chemical Characteristics of Particulate Matters and Trajectory Influence on Air Quality in Shanghai During the Heavy Haze Episode in December, 2013].

Intensive haze shrouded central and eastern parts of China in Dec. 2013. In this study, the mass concentrations of gaseous and particulate pollutants, and also the chemical compositions of fine particulate matters were obtained based on in-situ measurement in Shanghai urban area. The characteristics of PM2.5 were investigated during different pollution episodes, including dust, haze, fog-haze and long-rang transport episodes. The results showed that pollution was most serious during the fog-haze episode, during which the maximum daily mass concentrations of PM10 and PM2.5 reached 536 microg x m(-3) and 411 microg x m(-3), respectively. During the fog-haze episode, the ratio of PM2.5 to PM10 was over 76.7%, suggesting that high humidity enhanced the secondary formation of NO3-, SO4(2-) and NH4+ in PM2.5. Highest concentration of Ca2+ in PM2.5 occurred during the dust episode and the proportion of primary components in PM2.5 increased obviously. Highest concentration of SO2- was observed in PM25 during the long-range transport episode, with a fast growth rate. Meanwhile, the trajectories reaching Shanghai urban area and cluster analysis during different pollution episodes were simulated by HYSPLIT model. Combined with observation data of PM2.5 in Shanghai urban area, chemical characteristics of PM2.5 in different clusters and potential source apportionment of various pollution episodes were also studied in this study. The result revealed that the air trajectories could be grouped into six clusters based on their spatial similarities. Among these clusters, cluster6 which moved fast was associated with clean air. Cluster2 and cluster3 originating from Mongolia region had strong correlations to dust pollution, along with low PM2.5/PM10 ratio and high concentration of Ca2+ in PM2.5. Compared with other clusters, cluster5 and cluster4 with slow moving speed were more favorable for reactions between particulate species and formation of secondary pollutants during transport. Additionally, the stagnant weather condition under these two clusters with high water vapor when passing over the East China Sea further led to the aggravation of atmospheric pollution in Shanghai.

[Development of 3-enzyme pyrosequencing system and its application in rapid diagnosis of Down's syndrome].

To avoid sequencing error resulting from use of apyrase in conventional 4- enzyme pyrosequencing system, a non-apyrase 3-enzyme pyrosequencing system with a better performance of quantitative analysis was established. The method is to immobilize biotinylated DNA template, ATP sulfurylase and luciferase on streptavidin-coated magnetic beads for pyrosequencing. After pyrosequencing, ATP produced from the pyrosequencing reaction and excess dNTPs were removed by magnetic separation technique; another dNTP was then dispensed for sequencing reaction, and the components interfering with the next circle of pyrosequencing reaction were removed by the same way, achieving the circular sequencing. This new system can accurately measure base sequences of a target DNA template, and also can quantitatively determine the relative ratio of two alleles. The allele ratios in two SNPs (rs1042917 and rs4818219) having a higher heterozygote rate on chromosome 21 were successfully detected for 16 normal samples and 8 clinical samples from Down's syndrome patients. The results can accurately demonstrate whether or not the target sample has equal copies of chromosome 21 from mother and father. This paper established a non-apyrase 3-enzyme pyrosequencing method, which owns a good perform-ance of quantitative analysis. The method is especially suitable to allelic quantification of an SNP, enabling the rapid diagnosis of Down's syndrome by analyzing allele ratio of SNPs on chromosome 21.