Scientific knowledge on the chemical compositions of fine particulate matter(PM_(2.5)) is essential for properly assessing its health and climate effects,and for decisionmakers to develop efficient mitigation strategi...
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Scientific knowledge on the chemical compositions of fine particulate matter(PM_(2.5)) is essential for properly assessing its health and climate effects,and for decisionmakers to develop efficient mitigation strategies.A high-resolution PM_(2.5) chemical composition dataset(CAQRA-aerosol)is developed in this study,which provides hourly maps of organic carbon,black carbon,ammonium,nitrate,and sulfate in China from 2013 to 2020 with a horizontal resolution of 15 *** paper describes the method,access,and validation results of this *** shows that CAQRA-aerosol has good consistency with observations and achieves higher or comparable accuracy with previous PM_(2.5) composition *** on CAQRA-aerosol,spatiotemporal changes of different PM_(2.5) compositions were investigated from a national viewpoint,which emphasizes different changes of nitrate from other *** estimated annual rate of population-weighted concentrations of nitrate is 0.23μg m^(−3)yr^(−1) from 2015 to 2020,compared with−0.19 to−1.1μg m^(−3)yr^(−1) for other *** whole dataset is freely available from the China Air Pollution Data Center(https://***/10.12423/capdb_***).
Qualitative and quantitative analyses of derivatized phenols in Beijing and in Xinglong were performed from 2016 to 2017 using gas chromatography-mass *** results showed substantially more severe pollution in *** the ...
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Qualitative and quantitative analyses of derivatized phenols in Beijing and in Xinglong were performed from 2016 to 2017 using gas chromatography-mass *** results showed substantially more severe pollution in *** the 14 compounds detected,the total average concentration was 100 ng/m^3 in Beijing,compared with 11.6 ng/m^3 in *** specifically,concentration of nitro-aromatic compounds(NACs)(81.9 ng/m^3 in Beijing and 8.49 ng/m^3 in Xinglong) was the highest,followed by aromatic acids(14.6 ng/m^3 in Beijing and 2.42 ng/m^3 in Xinglong) and aromatic aldehydes(3.62 ng/m^3 in Beijing and 0.681 ng/m^3 in Xinglong).In terms of seasonal variation,the highest concentrations were found for 4-nitrocatechol in winter in Beijing(79.1±63.9 ng/m^3) and 4-nitrophenol in winter in Xinglong(9.72±8.94 ng/m^3).The analysis also revealed diurnal variations across different *** compounds presented higher concentrations at night in winter because of the decreased boundary layer height and increased heating *** some presented higher levels during the day,which attributed to the photo-oxidation process for summer and more biomass burning activities for *** concentrations appeared in winter and autumn than in spring and summer,which resulted from more coal combustions and adverse meteorological *** significant correlations among NACs indicated similar sources of *** correlations presented within each subgroup than those between the *** correlations between levoglucosan and nitrophenols,nitrocatechols,nitro salicylic acids,with correlation coefficients(r) of 0.66,0.69 and 0.69,respectively,indicating an important role of biomass burning among primary sources.
N-Containing heteroaromatics 1,2,4,5-tetra（pyridin-3-yl）benzene[1,2,4,5-T（3-PY）B] and 1,2,4,5-tetra（pyridin-4-yl）benzene[1,2,4,5-T（4-PY）B] were each co-crystallized with 1,2-diiodo-tetrafluoro-benzene（1,2-DI...
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N-Containing heteroaromatics 1,2,4,5-tetra（pyridin-3-yl）benzene[1,2,4,5-T（3-PY）B] and 1,2,4,5-tetra（pyridin-4-yl）benzene[1,2,4,5-T（4-PY）B] were each co-crystallized with 1,2-diiodo-tetrafluoro-benzene（1,2-DITFB）, or 1,4-diiodo-tetrafluoro-benzene（1,4-DITFB）, respectively, generating four co-crystals, namely, （1,2-DITFB）4 [1,2,4,5-T（3-PY）B]（1）, （1,2-DITFB）4.[ 1,2,4,5-T（4-PY）B]（2）, （1,4-DITFB）2.[1,2,4,5-T（3-PY）B]-CHCI3（3）, and （1,4-DITFB）-[1,2,4,5-T（4-PY）B]2CHCI3（4）. This study takes aim at providing an insight into the relative importance of fundamental solid state halogen bonding interactions（i.e., halogen..N, halogen,..halogen, and halogen...π in systems. The effects of the donor and acceptor on supramolecular assembly and the crystal structure determined interactions were discussed. The N...I halogen bonds are the main directing interactions responsible for the observed structures. In compounds 1 and 2, the donors exhibited lower-than-expected supramolecular connectivity. In spite of this, co-crystal 2 exhibits polymeric structures consisting of infinite one-dimensional（1D） double-zigzag chains of alternating electron donor and acceptor. The basic structure of co-crystals 3 and 4 is also infinite 1D chain. Therefore, the ID halogen bonded supramolecular assemblies can be obtained by matching the appropriate donor and acceptor.
Beijing is one of the most polluted cities in the *** this study,the long-term and continuous measurements of volatile organic compounds （VOCs） in the urban area of Beijing,specifically at Beijing 325 m Meteorologic...
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Beijing is one of the most polluted cities in the *** this study,the long-term and continuous measurements of volatile organic compounds （VOCs） in the urban area of Beijing,specifically at Beijing 325 m Meteorological Tower,were conducted from 2000 to *** annual record of VOC trends exhibited in two different phases was separated in *** show that VOC concentrations increased from 2000 to 2003 due to the abrupt increase in vehicle ***,since 2003,there had been a decrease in VOCs concentrations as the policy on gasoline and air pollution was ***,benzene,and i-pentane are the chemicals that abound in and are directly related to vehicle activity,such as in vehicle exhaust and gasoline ***,records indicate that there had been seasonal variation in VOCs levels in that VOCs level in summer is higher than that in *** such,temperature is considered to significantly contribute to VOCs in *** also show that VOCs level was high in the morning and during rush hours in the *** contrast,VOCs level was low during midday due to photochemical destruction with OH radical and dilution *** this study,a particular benzene to toluene ratio range （0.4–1.0） was used as the indicator of air propelled by vehicular *** also applied the correlation coefficients between BTEX and i-pentane to evaluate evaporation influence to ambient BTEX in the Beijing urban area.
We implemented the online coupled WRF-Chem model to reproduce the 2013 January haze event in North China, and evaluated simulated meteorological and chemical fields using multiple observations. The comparisons suggest...
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We implemented the online coupled WRF-Chem model to reproduce the 2013 January haze event in North China, and evaluated simulated meteorological and chemical fields using multiple observations. The comparisons suggest that temperature and relative humidity （RH） were simulated well （mean biases are 0.2K and 2.7%, respectively）, but wind speeds were overestimated （mean bias is 0.5 m.s -1）. At the Beijing station, sulfur dioxide （SO2） concentrations were overpredicted and sulfhte concentrations were largely underpredicted, which may result from uncertainties in SO2 emissions and missing heterogeneous oxidation in current model. We conducted three parallel experiments to examine the impacts of doubling SO2 emissions and incorporating heterogeneous oxidation of dissolved SO2 by nitrogen dioxide （NO2） on sulfate formation during winter haze. The results suggest that doubling SO2 emissions do not significantly affect sulthte concentrations, but adding heterogeneous oxidation of dissolved SO2 by NO, substantially improve simulations of sulfate and other inorganic aerosols. Although the enhanced SO2 to sulfate conversion in the HetS （heterogeneous oxidation by NO2） case reduces SO2 concentrations, it is still largely overestimated by the model, indicating the overestimations of SO2 concentrations in the North China Plain （NCP） are mostly due to errors in SO2 emission inventory.
Fine particle of organic aerosol （OA）, mostly arising from pollution, are abundant in Beijing. To achieve a better un- derstanding of the difference in OA in summer and autumn, a high-resolution time-of-flight aeros...
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Fine particle of organic aerosol （OA）, mostly arising from pollution, are abundant in Beijing. To achieve a better un- derstanding of the difference in OA in summer and autumn, a high-resolution time-of-flight aerosol mass spectrometer （HR- ToF-AMS, Aerodyne Research Inc., USA） was deployed in urban Beijing in August and October 2012. The mean OA mass concentration in autumn was 30 4-30 μg m-3, which was higher than in summer （13 4-6.9 μg m-3）. The elemental anal- ysis found that OA was more aged in summer （oxygen-to-carbon （O/C） ratios were 0.41 and 0.32 for summer and autumn, respectively）. Positive matrix factorization （PMF） analysis identified three and five components in summer and autumn, re- spectively. In summer, an oxygenated OA （OOA）, a cooking-emission-related OA （COA）, and a hydrocarbon-like OA （HOA） were indentified. Meanwhile, the OOA was separated into LV-OOA （low-volatility OOA） and SV-OOA （semi-volatile OOA）; and in autumn, a nitrogen-containing OA （NOA） was also found. The SOA （secondary OA） was always the most important OA component, accounting for 55% of the OA in the two seasons. Back trajectory clustering analysis found that the origin of the air masses was more complex in summer. Southerly air masses in both seasons were associated with the highest OA loading, while northerly air masses were associated with the lowest OA loading. A preliminary study of OA components, especially the POA （primary OA）, in different periods found that the HOA and COA all decreased during the National Day holiday period, and HOA decreased at weekends compared with weekdays.
In this study, we performed a highly time-resolved chemical characterization of nonrefractory submicron particles（NR-PM_1） in Beijing by using an Aerodyne high-resolution time-of-flight aerosol mass spectrometer（HR...
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In this study, we performed a highly time-resolved chemical characterization of nonrefractory submicron particles（NR-PM_1） in Beijing by using an Aerodyne high-resolution time-of-flight aerosol mass spectrometer（HR-ToF-AMS）. The results showed the average NR-PM_1 mass concentration to be 56.4 ± 58.0 μg/m^3, with a peak at 307.4 μg/m^3. Due to the high frequency of biomass burning in autumn, submicron particles significantly increased in organic content, which accounted for 51% of NR-PM_1 on average. Secondary inorganic aerosols（sulfate ＋ nitrate ＋ ammonium） accounted for 46% of NR-PM_1, of which sulfate,nitrate, and ammonium contributed 15%, 20%, and 11%, respectively. To determine the intrinsic relationships between the organic and inorganic species, we used the positive matrix factorization（PMF） model to merge the high-resolution mass spectra of the organic species and NO＋and NO_2~＋ions. The PMF analysis separated the mixed organic and nitrate（NO＋and NO_2~＋） spectra into four organic factors, including hydrocarbon-like organic aerosol（HOA）, oxygenated organic aerosol（OOA）, cooking organic aerosol（COA）, and biomass burning organic aerosol（BBOA）, as well as one nitrate inorganic aerosol（NIA） factor. COA（33%） and OOA（30%） contributed the most to the total organic aerosol（OA） mass, followed by BBOA（20%） and HOA（17%）. We successfully quantified the mass concentrations of the organic and inorganic nitrates by the NO＋and NO2＋ions signal in the organic and NIA factors. The organic nitrate mass varied from 0.01-6.8 μg/m^3, with an average of 1.0 ±1.1 μg/m^3, and organic nitrate components accounted for 10% of the total nitrate mass in this observation.
Particulate matter(PM_(2.5))pollution in high emission regions will affect air quality,human health and climate change on both local and regional scales,and thus attract worldwide *** this study,a comprehensive study ...
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Particulate matter(PM_(2.5))pollution in high emission regions will affect air quality,human health and climate change on both local and regional scales,and thus attract worldwide *** this study,a comprehensive study on PM_(2.5)and its chemical composition were performed in Yuncheng(the most polluted city of Fen-Wei Plain of China)from November28,2020 to January 24,*** average concentration of PM_(2.5)was 87.8±52.0μg/m^(3),which were apparently lower than those observed during the same periods of past five years,attributable to the clean air action plan implemented in this ***_(3)^(-)and organic carbon(OC)were the dominant particulate components,which on average contributed 22.6%and16.5%to PM_(2.5)2.5,*** fractions of NO_(3)^(-),NH_(4)^(+),OC and trace metals increased while those of crustal materials and elemental carbon decreased with the degradation of PM_(2.5)*** types of PM_(2.5)sources were identified by the PM_(2.5)F model,including secondary inorganic aerosol(35.3%),coal combustion(28.7%),vehicular emission(20.7%),electroplating industry(8.6%),smelt industry(3.9%)and dust(2.8%).Locations of each identified source were pinpointed based on conditional probability function,potential source contribution function and concentration weighted trajectory,which showed that the geographical distribution of the sources of PM_(2.5)roughly agreed with the areas of high ***,this study provides valuable information on atmospheric pollution and deems beneficial for policymakers to take informed action to sustainably improve air quality in highly polluted region.
The influences of strong El Nino events(1997/98 and 2015/16)on summertime near-surface ozone(O_(3))concentrations over China are investigated using the GEOS-Chem *** results show that near-surface O_(3) concentrations...
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The influences of strong El Nino events(1997/98 and 2015/16)on summertime near-surface ozone(O_(3))concentrations over China are investigated using the GEOS-Chem *** results show that near-surface O_(3) concentrations increased by a maximum of 6 ppb(parts per billion)during the summer of the developing phase of the 1997/98 El Nino in northeastern China,mainly due to the increased chemical production related to the hot and dry ***,the O_(3) concentration increased by 3 ppb during the developing summer of both the 1997/98 and 2015/16 El Nino in southern *** was linked to the weakened prevailing monsoon winds,which led to the accumulation of O_(3) in southern *** contrast,in the summer of the decaying phase of the two El Nino events,O_(3) concentrations decreased over many regions of China when the El Nino reversed to the cooling *** highlights that El Nino plays an important role in modulating near-surface O_(3) concentrations over China.
Scientific knowledge on the chemical compositions of fine particulate matter(PM2.5) is essential for properly assessing its health and climate effects, and for decisionmakers to develop efficient mitigation strategies...
Scientific knowledge on the chemical compositions of fine particulate matter(PM2.5) is essential for properly assessing its health and climate effects, and for decisionmakers to develop efficient mitigation strategies. A high-resolution PM2.5chemical composition dataset（CAQRA-aerosol） is developed in this study, which provides hourly maps of organic carbon,black carbon, ammonium, nitrate, and sulfate in China from 2013 to 2020 with a horizontal resolution of 15 km. This paper describes the method, access, and validation results of this dataset. It shows that CAQRA-aerosol has good consistency with observations and achieves higher or comparable accuracy with previous PM2.5composition datasets. Based on CAQRA-aerosol, spatiotemporal changes of different PM2.5compositions were investigated from a national viewpoint,which emphasizes different changes of nitrate from other compositions. The estimated annual rate of population-weighted concentrations of nitrate is 0.23 μg m-3yr-1from 2015 to 2020, compared with-0.19 to -1.1 μg m-3yr-1for other compositions. The whole dataset is freely available from the China Air Pollution Data Center（https://***/10.12423/capdb＿***）.
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