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Atmospheric amines have unique acid-neutralizing capacity and play an important role in atmospheric chemical reactions. An integrated observation of PM 2.5 samples (from Dec 2015 to Nov 15, 2016) was conducted in a typical industrial city (Xuzhou), China. Concentrations of total measured amines (∑amines, including methylamine (MA), ethylamine (EA), dimethylamine (DMA), propanamine (PA) and trimethylamine (TMA) + diethylamine (DEA)) were 172.0 ± 98.2 ng m -3 , accounting 1.5 ± 0.6 ‰ of PM 2.5 mass. ∑amines were higher in winter (249.0 ± 112.3 ng m -3 ) and spring (192.4 ± 75.9 ng m -3 ) than in summer (114.7 ± 33.3 ng m -3 ) and autumn (103.7 ± 34.3 ng m -3 ). Concentrations of MA and EA (the dominant amines) were highest in winter, while DMA, PA and TMA + DEA showed opposite seasonality. EA/MA ratios ranged from 0.04 to 8.7 with a median value of 0.3, and the averaged EA/MA ratio was 2.0 in winter, indicating large contribution of EA. Environmental factors including temperature (T), relative humidity (RH) and atmospheric oxidizing capacity (O 3 and O x represented) were found to influence concentrations of amines in PM 2.5 . The Positive Matrix Factorization (PMF) model identified secondary products (41.6 %), combustion emissions (39.8 %), soil and waste incineration emissions (13.2 %) and biological emissions and aging products (5.4 %) as the 4 sources of amines in PM 2.5 . MA was mainly secondary products (82.5 %) and had high contribution of local secondary formation, while EA was mainly derived from combustion emissions (83.7 %) and influenced by regional transportation. In winter, combustion emissions (including coal combustion, biomass burning and traffic emissions, contributed 57.7 %) surpassed secondary products (31.6 %) as the predominant sources of amines, especially under the influence of regional transportation (75.7 %)., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Carbonaceous aerosol is an important component of atmospheric fine particles that has an important impact on air quality, human health, and climate change. In order to explore the long-term changes in carbonaceous aerosol under the background of emission reduction, this study measured the mass concentrations of organic carbon (OC) and elemental carbon (EC) of PM 2.5 , which collected in the northern suburbs of Nanjing for five years (December 17, 2014 to January 5, 2020). The results showed that the five-year average ρ (OC) and ρ (EC) were (10.2±5.3) μg·m -3 and (1.6±1.1) μg·m -3 , accounting for 31.1% and 5.2% of PM 2.5 , respectively. OC and EC concentrations were both high in winter and low in summer. According to the nonparametric Mann-Kendall test and Sen's slope, the mass concentrations of OC and PM 2.5 decreased significantly[OC: P <0.0001, -0.79 μg·(m 3 ·a) -1 , -0.29%·a -1 ; PM 2.5 : P <0.0001, -4.59 μg·(m 3 ·a) -1 , -1.58%·a -1 ]. Although EC had an upward trend, the significance and range of change were not obvious[ P =0.02, 0.05 μg·(m 3 ·a) -1 , 0.02%·a -1 ]. OC and EC decreased significantly during winter from 2014 to 2019[OC: P <0.0001, -2.05 μg·(m 3 ·a) -1 , -0.74%·a -1 ; EC: P =0.001, -0.15 μg·(m 3 ·a) -1 , -0.05%·a -1 ], and the decline was more obvious than the whole. The correlation between OC and EC showed that the sources in winter and summer were more complex than those in spring and autumn. According to the characteristic ratio of OC and EC, the contribution of coal combustion and biomass burning decreased from 2015 to 2019, whereas the impact of industrial sources and vehicle emissions became more significant. Corresponding to this was the obvious decline in OC and the slight recovery of EC. The OC/EC ratio was over 2.0, indicating that there was secondary pollution in the study area. Further calculation revealed that the variation in SOC was consistent with that in OC, showing a significant decrease[ P <0.0001, -0.47 μg·(m 3 ·a) -1 , -0.17%·a -1 ]. The average mass concentration of SOC was (5.0±3.5) μg·m -3 , accounting for 49.2% of OC. These changes indicate clear effects of the prevention and control of air pollution in Nanjing in recent years. Furthermore, future control can focus on the emissions of VOCs to reduce secondary pollution.

Biomass burning (BB) is an important source of carbonaceous aerosols in Northeast China (NEC). Quantifying the original contribution of BB to organic carbon (OC) [BB-OC] can provide an essential scientific information for the policy-makers to formulate the control measures to improve the air quality in the NEC region. Daily PM 2.5 samples were collected in the rural area of Changchun city over the NEC region from May 2017 to May 2018. In addition to carbon contents, BB tracers (e.g., levoglucosan and K + BB , defined as potassium from BB) were also determined, in order to investigate the relative contribution of BB-OC. The results showed that OC was the dominant (28%) components of PM 2.5 during the sampling period. Higher concentrations of OC, levoglucosan, and K + BB were observed in the autumn followed by the winter, spring, and summer, indicating that the higher BB activities during autumn and winter in Changchun. By using the Bayesian mixing model, it was found that burning of crop residues were the dominant source (65-79%) of the BB aerosols in Changchun. During the sampling period, the aging in air mass (AAM) ratio was 0.14, indicating that ~86% of levoglucosan in Changchun was degraded. Without considering the degradation of levoglucosan in the atmosphere, the BB-OC ratios were 23%, 28%, 7%, and 4% in the autumn, winter, spring, and summer, respectively, which were 1.4-4.8 time lower than those (14-42%) with consideration of levoglucosan degradation. This illustrated that the relative contribution of BB to OC would be underestimated (~59%) without considering degradation effects of levoglucosan. Although some uncertainty was existed in our estimation, our results did highlight that the control of straw burning was an efficient way to decrease the airborne PM 2.5 , improving the air quality in the NEC plain., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Humic-like substances (HULIS), as important components of brown carbon (BrC), play an important role in climate change. In this study, one-year PM 2.5 samples from 2017 to 2018 were collected at Nanjing, China and the water soluble HULIS and other chemical species were analyzed to investigate the seasonal variations, optical properties and possible sources. The HULIS concentrations exhibited highest in winter and lowest in summer. The annual averaged HULIS concentration was 2.61 ± 1.79 μg m -3 , accounting for 45 ± 13% of water-soluble organic carbon (WSOC). The HULIS light absorption coefficient at 365 nm (Abs 365, HULIS ) averagely accounted for 71 ± 19% of that of WSOC, suggesting that HULIS are the main light-absorbing components in WSOC. The annual averaged Ångström absorption exponent and mass absorption efficiency of HULIS at 365 nm were 5.22 ± 0.77 and 1.71 ± 0.70 m 2  g -1 . Good correlations between HULIS with levoglucosan and K + suggested biomass burning (BB) influence on HULIS. High concentrations of HULIS and secondary species (e.g., NO 3 - , SO 4 2- , NH 4 + , C 2 O 4 2- ) were found in present of high relative humidity, indicating strong aqueous phase secondary HULIS formation. Secondary HULIS produced from anthropogenic and biogenic precursors were quantified based on the positive matrix factorization (PMF) model and the results showed that both fossil (55%) and biogenic (45%) emission sources made great contributions to HULIS. Fossil fuel combustion significantly contributed to HULIS formation throughout the whole year, which were enriched with more secondary HULIS (30%) than primary HULIS (25%). Strongest BB contribution (39%) was found in winter and biogenic SOA contribution (32%) was found in summer. A multiple linear regression (MLR) method was further applied to obtain specific source contributions to Abs 365, HULIS and the results showed that strong light-absorbing chromophores were produced from anthropogenic precursors. Our results highlight the anthropogenic SOA and fossil fuels combustion contributions to HULIS in addition to the biggest contributor, BB, in urban area in China., (Copyright © 2021 Elsevier Inc. All rights reserved.)

High concentrations of PM 2.5 in China have caused severe visibility degradation and health problems. However, it is still challenging to accurately predict PM 2.5 and its chemical components in numerical models. In this study, we compared the inorganic aerosol components of PM 2.5 (sulfate, nitrate, and ammonium (SNA)) simulated by the Weather Research and Forecasting model fully coupled with chemistry (WRF-Chem) model with in-situ data in a heavy haze-fog event during November 2018 in Nanjing, China. Comparisons show that the model underestimates sulfate concentrations by 81% and fails to reproduce the significant increase of sulfate from early morning to noon, which corresponds to the timing of fog dissipation that suggests the model underestimates the aqueous-phase formation of sulfate in clouds. In addition, the model overestimates both nitrate and ammonium concentrations by 184% and 57%, respectively. These overestimates contribute to the simulated SNA being 77.2% higher than observed. However, cloud water content is also underestimated which is a pathway for important aqueous-phase reactions. Therefore, we constrained the simulated cloud water content based on the Moderate Resolution Imaging Spectroradiometer (MODIS) Liquid Water Path observations. Results show that the simulation with MODIS-corrected cloud water content increases the sulfate by a factor of 3, decreases the Normalized Mean Bias (NMB) by 53.5%, and reproduces its diurnal cycle with the peak concentration occurring at noon. The improved sulfate simulation also improves the simulation of nitrate, which decreases the simulated nitrate bias by 134%. Although the simulated ammonium is still higher than the observations, corrected cloud water content leads to a decrease of the modelled bias in SNA from 77.2% to 14.1%. The strong sensitivity of simulated SNA concentration to the cloud water content provides an explanation for the simulated SNA bias. Hence, uncertainties in cloud water content can contribute to model biases in simulating SNA which are less frequently explored from a process-level perspective and can be reduced by constraining the model with satellite observations., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

So far, studies on the conversion of stereochemistry under photo-Fenton conditions and their atmospheric implication are still rare. Here, we found that the biomass burning marker, the chiral compound levoglucosan (L), undergoes oxidative degradation under photo-Fenton conditions and can be isomerized into mannosan (M) and galactosan (G) simultaneously. Among the formic acid, acetic acid, and oxalic acid in the degradation products of levoglucosan, it was found that the yield of formation of formic acid in the photo-Fenton pathway can be as high as 86%. It is worth noting that both levoglucosan and its isomers are present in the atmosphere and their concentrations are strongly correlated. At the same time, the range of their concentration ratios, L/(G + M), measured in the photo-Fenton experiments in the laboratory was found to agree well with that measured in atmospheric PM 2.5 samples. However, the sources of L, G, and M in the atmosphere are complex, and the photo-Fenton reaction may be an essential pathway for the distribution of L, G, and M in the atmosphere.

Fine particulate matter (PM2.5) samples were collected using a high-volume air sampler and pre-combusted quartz filters during May 2013 to January 2014 at a background rural site (47 ∘ 35 N, 133 ∘ 31 E) in Sanjiang Plain, Northeast China. A homologous series of dicarboxylic acids (C 2 -C 11 ) and related compounds (oxoacids, α-dicarbonyls and fatty acids) were analyzed by using a gas chromatography (GC) and GC-MS method employing a dibutyl ester derivatization technique. Intensively open biomass-burning (BB) episodes during the harvest season in fall were characterized by high mass concentrations of PM2.5, dicarboxylic acids and levoglucosan. During the BB period, mass concentrations of dicarboxylic acids and related compounds were increased by up to >20 times with different factors for different organic compounds (i.e., succinic (C 4 ) acid > oxalic (C 2 ) acid > malonic (C 3 ) acid). High concentrations were also found for their possible precursors such as glyoxylic acid (ωC 2 ), 4-oxobutanoic acid, pyruvic acid, glyoxal, and methylglyoxal as well as fatty acids. Levoglucosan showed strong correlations with carbonaceous aerosols (OC, EC, WSOC) and dicarboxylic acids although such good correlations were not observed during non-biomass-burning seasons. Our results clearly demonstrate biomass burning emissions are very important contributors to dicarboxylic acids and related compounds. The selected ratios (e.g., C 3 /C 4 , maleic acid/fumaric acid, C 2 /ωC 2 , and C 2 /levoglucosan) were used as tracers for secondary formation of organic aerosols and their aging process. Our results indicate that organic aerosols from biomass burning in this study are fresh without substantial aging or secondary production. The present chemical characteristics of organic compounds in biomass-burning emissions are very important for better understanding the impacts of biomass burning on the atmosphere aerosols., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

To better characterize the chemical compositions and sources of fine particulate matter (i.e. PM 2.5 ) in Sanjiang Plain, Northeast China, total carbon (TC), organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC), and inorganic ions as well as stable carbon isotopic composition (δ 13 C) were measured in this study. Intensively open biomass burning episodes are identified from late September to early October by satellite fire and aerosol optical depth maps. During the biomass-burning episode, concentrations of PM 2.5 , OC, EC, and WSOC are increased by a factor of 4-12 compared to those during the non-biomass-burning period. Non-sea-salt potassium is strongly correlated with PM 2.5 , OC, EC and WSOC, demonstrating an important contribution from biomass-burning emissions. The enrichment in both the non-sea-salt potassium and chlorine is significantly larger than other inorganic species, suggesting that biomass-burning aerosols in Sanjiang Plain are mostly fresh and less aged. In addition, the WSOC-to-OC ratio is lower than that reported in biomass-burning aerosols in tropical regions, further supporting that biomass-burning aerosols in Sanjiang Plain are mostly primary and secondary organic aerosols may be not significant. A lower average δ 13 C value (-26.2‰) is observed during the biomass-burning period, indicating a dominant contribution from combustion of C3 plants in the studied region., (Copyright © 2015. Published by Elsevier B.V.)

This study presents one of the first long term datasets including a statistical summary of PM2.5 concentrations obtained from one-year monitoring in 190 cities in China. We found only 25 out of 190 cities could meet the National Ambient Air Quality Standards of China, and the population-weighted mean of PM2.5 in Chinese cities are 61 μg/m(3), ~3 times as high as global population-weighted mean, highlighting a high health risk. PM2.5 concentrations are generally higher in north than in south regions due to relative large PM emissions and unfavorable meteorological conditions for pollution dispersion. A remarkable seasonal variability of PM2.5 is observed with the highest during the winter and the lowest during the summer. Due to the enhanced contributions from dust particles and open biomass burning, high PM2.5 abundances are also found in the spring (in Northwest and West Central China) and autumn (in East China), respectively. In addition, we found the lowest and highest PM2.5 often occurs in the afternoon and evening hours, respectively, associated with daily variation of the boundary layer depth and anthropogenic emissions. The diurnal distribution of the PM2.5-to-CO ratio consistently displays a pronounced peak during the afternoon periods, reflecting a significant contribution of secondary PM formation.

An increase in haze days has been observed in China over the past two decades due to the rapid industrialization, urbanization and energy consumptions. To address this server issue, Chinese central government has recently released the Action Plan on Prevention and Control of Air Pollution, which mainly focuses on regulation of indusial and transport-related emissions with major energy consumption from fossil fuels. This comprehensive and toughest plan is definitely a major step in the right direction aiming at beautiful and environmental-friendly China; however, based on recent source apportionment results, we suggest that strengthening regulation emissions from biomass-burning sources in both urban and rural areas is needed to meet a rigorous reduction target. Here, household biofuel and open biomass burning are highlighted, as impacts of these emissions can cause local and regional pollution., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

To study the role of biomass burning (BB) in air pollution at upper‐northern Thailand, the source apportionment of size‐resolved carbonaceous aerosols from Chiang Mai was carried out based on the radiocarbon (14C) analysis. The fraction of modern carbon (F14C) was generally decreased with particle size increasing and with the highest and lowest values of 0.90 ± 0.04 and 0.61 ± 0.04, respectively. Elemental carbon, regardless of emission sources, and BB‐derived organic carbon (OCbb) showed unimodal size distribution patterns with peaks at 0.43–0.65 μm. Fossil‐fuel derived‐OC (OCf) displayed a bimodal mode with the major peak at 2.1–10 μm, and the minor one at 0.43–0.65 μm. The biogenic secondary organic aerosols (BSOA) showed a typical fine‐mode unimodal size distribution pattern during the high BB (HBB) season, and a bimodal mode during the low BB season. The BSOA concentration increased by 189% ± 80% due to the interaction with open BB plums during HBB season, which was quantified by a 14C‐involved random forest model. Besides, the concentration of biogenic primary organic aerosols also showed a significant increment during the HBB season, especially in sub‐microns. Our results highlight the critical importance of controlling open fires to reduce air pollutants and the potential exposure risk. Plain Language Summary: Large‐scale biomass burning (BB) activities take place annually in Southeast Asia. BB can emit large amounts of carbonaceous aerosols (CA) thus affecting human health and causing climate change. The particle size, directly affects how deep the particle can penetrate the human body, can be significantly changed by BB. In this study, BB‐derived CA contributed the most to the total concentration of CA. The concentration of BB‐derived CA in PM10 (particles with an aerodynamic diameter of less than 10 μm) was 12 times higher in high BB (HBB) season than in low BB (LBB) season. More specifically, BB‐derived CA in fine (PM1.1) and coarse (PM1.1–10) particles increased by roughly 13 and 5 times in HBB season compared to LBB season, respectively. Besides, BB enhanced the concentration of biogenic secondary organic aerosols by 180%, wherein 65% of the increment was allocated in PM1.1. Our results indicated that BB can not only emit particles or precursors of aerosol particles but also promote the generation of biogenic aerosols. And BB significantly enhanced the loading of CA, particularly in fine particles. Key Points: Fossil‐derived carbonaceous aerosols (CA) showed a bimodal mode size distribution patternNon‐fossil‐derived CA showed a typical fine‐mode unimodal size distribution patternBiomass burning greatly enhanced the production of biogenic secondary organic aerosols particularly in fine aerosols [ABSTRACT FROM AUTHOR]

Excessive reactive oxygen species (ROS) in the human body is an important factor leading to diseases. Therefore, research on the content of reactive oxygen species in atmospheric particles is necessary. In recent years, the online detection technology of ROS has been developed. However, there are few technical studies on online detection of ROS based on the dithiothreitol (DTT) method. Here, to modify the instrument, a DTT experimental module is added that is protected from light and filled with nitrogen at the end based on the Monitor for AeRosols and Gases in ambient Air (MARGA). The experimental study found that the detection limit of the modified instrument is 0.024 nmol min -1. The DTT consumption rate of blank sample (ultrapure water) is reduced by 44 %, which eliminates the influence of outside air and light in the experiment. And the accuracy of the online instrument is determined by comparing the online and offline levels of the samples, which yielded good consistency (slope 0.97, R2=0.95). It shows that the performance of the instrument is indeed optimized, the instrument is stable, and the characterization of ROS is accurate. The instrument not only realizes online detection conveniently and quickly, but also achieves the hour-by-hour detection of ROS based on the DTT method. Meanwhile, reactive oxygen and inorganic ions in atmospheric particles are quantified using the online technique in the northern suburbs of Nanjing. It is found that the content of ROS during the day is higher than that at night, especially after it rains; ROS peaks appear in the two time periods of 08:00–10:00 and 16:00–18:00 (China Standard Time, UTC + 8:00; expressed here in local time – LT). In addition, examination of the online ROS, water-soluble ion (SO42- , NO3- , NH4+ , Na+ , Ca2+ , K+), BC, and polluting gas (SO2 , CO, O3 , NO, NOx) measurements revealed that photo-oxidation and secondary formation processes could be important sources of aerosol ROS. This breakthrough enables the quantitative assessment of atmospheric particulate matter ROS at the diurnal scale, providing an effective tool to study sources and environmental impacts of ROS. [ABSTRACT FROM AUTHOR]

Open biomass burning (BB) has contributed severely to the ambient levels of particulate matter of less than 2.5 μm diameter (PM2.5) in upper northern Thailand over the last decade. Some methods have been reported to identify the sources of burning using chemical compositions, i.e., ions, metals, polycyclic aromatic hydrocarbons, etc. However, recent advances in nuclear techniques have been limited in use due to their specific instrumentation. The aims of this study were to investigate the sources of ambient PM2.5 in Chiang Mai city using stable carbon (δ13C) and nitrogen isotopes (δ15N). The mean concentrations of total carbon (TC) and total nitrogen (TN) in PM2.5 were 12.2 ± 5.42 and 1.91 ± 1.07 μg/m3, respectively, whereas δ13C and δ15N PM2.5 were −26.1 ± 0.77‰ and 10.3 ± 2.86‰, respectively. This isotopic analysis confirmed that biomass burning was the source of PM2.5 and that C3 and C4 plants contributed about 74% and 26%, respectively. These study results confirm that the stable isotope is an important tool in identifying the sources of aerosols. [ABSTRACT FROM AUTHOR]

Inorganic nitrate production is critical in atmospheric chemistry that reflects the oxidation capacity and the acidity of the atmosphere. Here we use the oxygen anomaly of nitrate (Δ17O( NO 3 − )) in high-time-resolved (3 h) aerosols to explore the chemical mechanisms of nitrate evolution in fine particles during the winter in Nanjing, a megacity of China. The continuous Δ17O( NO 3 − ) observation suggested the dominance of nocturnal chemistry (NO3 + HC/H2O and N2O5 + H2O/Cl−) in nitrate formation in the wintertime. Significant diurnal variations of nitrate formation pathways were found. The contribution of nocturnal chemistry increased at night and peaked (72%) at midnight. Particularly, nocturnal pathways became more important for the formation of nitrate in the process of air pollution aggravation. In contrast, the contribution of daytime chemistry (NO2 + OH/H2O) increased with the sunrise and showed a highest fraction (48%) around noon. The hydrolysis of N2O5 on particle surfaces played an important role in the daytime nitrate production on haze days. In addition, the reaction of NO2 with OH radicals was found to dominate the nitrate production after nitrate chemistry was reset by the precipitation events. These results suggest the importance of high-time-resolved observations of Δ17O( NO 3 − ) for exploring dynamic variations in reactive nitrogen chemistry. [ABSTRACT FROM AUTHOR]

Excessive reactive oxygen species (ROS) in the human body is an important factor leading to diseases. Therefore, research on the content of reactive oxygen species in atmospheric particles is necessary. In order to more conveniently and accurately detect the content of reactive oxygen in atmospheric particles hour by hour. Here, to modify the instrument, it is added a DTT experimental module that is protected from light and filled with nitrogen at the end, based on the Monitor for AeRosols and Gases in ambient Air (MARGA). The experimental study found that the detection limit of the modified instrument is 0.024 nmol min-1. And the accuracy of the online instrument is determined by comparing the online and offline levels of the samples, which yielded good consistency (slope 0.97, R2 = 0.95). It shows that the performance of the instrument is indeed optimized, the instrument is stable, and the characterization of ROS is accurate. Meanwhile, reactive oxygen and inorganic ions in atmospheric particles are quantified using the online technique in the northern suburbs of Nanjing. It is found that the content of ROS during the day is higher than that at night, especially after it rains, ROS peaks appear in the two time periods of 08:00-10:00 and 16:00-18:00. In addition, examination of the online ROS and water-soluble ions (SO42-, NO3-, NH4+, Na+, Ca2+, K+), BC and polluting gases (SO2, CO, O3, NO, NOx) measurements revealed that photo-oxidation and secondary formation processes could be important sources of aerosol ROS. This method breakthrough enables the quantitative assessment of atmospheric particulate matter ROS at the diurnal scale, providing an effective tool to study sources and environmental impacts of ROS. [ABSTRACT FROM AUTHOR]

Environmentally persistent free radicals (EPFRs) are a new type of substance with potential health risks. EPFRs are widely present in atmospheric particulates, but there is a limited understanding of the size-resolved health risks of these radicals. This study reports the exposure risks and source of EPFRs in atmospheric particulate matter (PM) of different particle sizes (<10 µm) in Linfen, a typical coal-burning city in China. The type of EPFRs in fine particles (< 2.1 µm) is different from that in coarse particles (2.1–10 µm) in both winter and summer. However, the EPFR concentration is higher in coarse particles than in fine particles in summer, and the opposite trend is found in winter. In both seasons, combustion sources are the main sources of EPFRs, with coal combustion as the major contributor in winter, while other fuels are the major source in summer. Dust contributes part of the EPFRs, and it is mainly present in coarse particles in winter and the opposite in summer. The upper respiratory tract was found to be the area with the highest risk of exposure to EPFRs of the studied aerosols, with an exposure equivalent to that of approximately 21 cigarettes per person per day. Alveolar exposure to EPFRs is equivalent to 8 cigarettes per person per day, with combustion sources contributing the most to EPFRs in the alveoli. This study helps us to better understand the potential health risks of atmospheric PM with different particle sizes. [ABSTRACT FROM AUTHOR]

The North China Plain (NCP) is becoming one of the most polluted areas characterized by a high frequency of haze pollution. However, the spatial and temporal evolutions of aerosol chemical compositions in such a highly polluted region are not well understood due to the lack of a long-term and comprehensive observation-based network. China's National Aerosol Composition Monitoring Network (NACMON) has conducted comprehensive offline and online measurements of compositions and optical properties of airborne aerosols in order to systematically investigate the formation process, source apportionments of haze, and interactions between haze pollution and climate change. The objective of the observations is to provide information for policy makers to make strategies for the alleviation of haze occurrence. In this paper, we present instrumentations and methodologies as well as the preliminary results of the offline observations in NACMON stations over the NCP region. The implications and future perspectives of the network are also summarized. Benefiting from simultaneous observations from this network, we found that secondary aerosols were the dominant component in haze pollution. High anthropogenic emissions, low wind speed, and high relative humidity (RH) facilitated gas-to-particle transformation and resulted in high PM2.5 formation (PM2.5 is particulate matter that is smaller than 2.5 μm in diameter). Sulfate-dominant or nitrate-dominant aerosols during the haze period were driven by ambient RH. Moreover, the contributions of coal combustion and biomass burning to PM2.5 revealed downward trends, whereas secondary aerosols showed upward trends over the last decade. Thus, we highlighted that strict control of anthropogenic emissions of precursor gases, such as NOx, NH3, and volatile organic compounds (VOCs), will be an important way to decrease PM2.5 pollution in the NCP region. [ABSTRACT FROM AUTHOR]

Hemorrhagic stroke (HS) is associated with severe morbidity and high mortality. Identifying the trigger factors for HS is critical for disease prevention. This study aimed to assess the associations between short-term environmental triggers (STETs) and HS risk. We systematically searched six databases for articles published up to September 9, 2022. Pooled odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated using random-effect models to evaluate the associations between STETs and the risk of HS. Heterogeneity was assessed using Cochran Q and I 2 tests. A total of 63 studies were included for analysis. Of these, 40 focused on air pollutants and 23 on meteorological factors. Pooling results showed that exposure to particulate matter 2.5 (PM 2.5; OR, 1.003 per 10 μg/m3; 95% CI, 1.001–1.007), sulfur dioxide (SO 2; OR, 1.022 per 10 ppb; 95% CI, 1.005–1.040), and nitrogen dioxide (NO 2; OR, 1.026 per 10 ppb; 95% CI, 1.004–1.047) was associated with an increase in HS risk. Moreover, exposure to PM 2.5 (OR, 1.018 per 10 μg/m3; 95% CI, 1.009–1.027) and SO 2 (OR, 1.102 per 10 ppb; 95% CI, 1.010–1.204) was positively associated with the risk of intracerebral hemorrhage. In addition, extreme temperature, high pressures, high and low relative humidity were potentially associated with HS risk. Targeted preventive measures to limit the effect of these air pollutants and extreme meteorological factors should be taken to reduce the HS disease burden. Further studies are warranted to verify these findings. • PM 2.5 , SO 2 , and NO 2 may be triggers for hemorrhagic stroke (HS). • PM 2.5 and SO 2 are positively associated with risk of intracerebral hemorrhage. • Temperature, humidity, and air pressure are potentially associated with HS. [ABSTRACT FROM AUTHOR]

Air pollution is the main cause of respiratory diseases. Fine particulates with the diameter below 2.5 μm can get into the alveoli and then enter the blood circulation through the lung tissue ventilation function and cause multiple systemic diseases especially the respiratory diseases. This study investigated the pathological mechanism of the lungs injury in rats induced by PM2.5 and the effect and mechanism of the Chinese herbal medicine number 2 Feibi Recipe (number 2 FBR) on lungs injury. In this experiment, Wistar rats were used. Lungs injury was induced by PM2.5. Number 2 FBR was used to treat the rats. The result showed that number 2 FBR could improve the lung injury in the rats. Meanwhile, it significantly reduced pathological response and inflammatory mediators including interleukin-6 (IL-6), interleukin-13 (IL-13), interleukin-17 (IL17), monocyte chemotactic protein-1 (MCP-1), and transforming growth factor-α (TNF-α) and upregulated glutathione peroxidase (GSH-Px) in the PM2.5 induced lung injury in the rats. Collectively, number 2 FBR appears to attenuate the lungs injury in rats induced by PM2.5. [ABSTRACT FROM AUTHOR]

One-hour resolution observations of stable carbon isotopes in both gaseous water-soluble organic carbon (WSOCg) and particulate water-soluble organic carbon (WSOCp) were conducted at a city site in the Yangtze River Delta. WSOCg exhibited significantly higher concentrations and lower 13C compared to WSOCp. The presence of radiation emerged as a crucial factor influencing the gas-particle partitioning mechanism of WSOC. There appeared to be distinct formation processes for WSOCp and WSOCg during nighttime, except on hazy days with elevated particulate matter concentrations. Gas-particle partitioning of WSOC may become inactive in environments with high temperatures and ozone concentrations, while it may become active in environments characterized by high relative humidity (RH) and elevated WSOCg concentrations. When addressing WSOC pollution, it's essential to focus not only on its sources but also on the suitable environmental conditions for gas-particle partitioning. Active gas-particle partitioning of WSOC may coincide with the formation of secondary inorganic ions (NH 4 +, NO 3 − and SO 4 2−). Thus, in targeting WSOC sources, it's imperative to implement coordinated strategies to control the sources of secondary inorganic ions. • Photochemical production is a critical mechanism of WSOC gas-particle partitioning during the wintertime. • δ13C–WSOC is influenced by both WSOC source compositions, meteorological conditions and gaseous pollutants concentrations. • Secondary inorganic ions are formed synergistically during gas-particle partitioning of WSOC. [ABSTRACT FROM AUTHOR]

Nitrate is the major component of fine particle matter in recent years, and fog deposition is an important sink form of atmospheric nitrate aerosol. However, evidence shows that high relative humidity, and stable atmosphere condition may lead to the rapid increase of secondary aerosols, including nitrate. Therefore, whether fog event is a sink or a source of nitrate aerosol is still an open question. Simultaneous observations of concentration and isotopes of nitrate both in PM 2.5 and fog water during fog event were conducted during a heavy fog event happened in winter of 2018 in Nanjing, a megacity sited in the Yangzi River Delta, China. Based on nine 12-h time resolution fog water samples and eleven 24-h time resolution PM 2.5 samples, it was found that NO 3 − concentration in PM 2.5 increased during the fog event (from 10.4 ± 8.6 μg m−3 to 21.2 ± 11.0 μg m−3). Compared with Δ17O–NO 3 - in PM 2.5 before (28.4 ± 3.7‰) and after the fog event (28.6 ± 1.3‰), Δ17O–NO 3 - in PM 2.5 during the fog event was higher (31.6 ± 1.2‰) and Δ17O–NO 3 - in fog water was lower (24.3 ± 1.2‰). The increased NO 3 − in PM 2.5 during the fog event had a different formation pathway compared with NO 3 − in PM 2.5 when there is no fog, and NO 3 − in fog water had another formation pathway as well. Explosive growth of NO 3 − in PM 2.5 may come from active NO 3 + HC reaction, along with happen of fog event through the reaction of NO 2 with ·OH or H 2 O and hydrolysis of N 2 O 5. As the fog event finished, the fog water possibly mainly settled NO 3 − newly generated during the fog event. It seems the fog event may be a source rather than a sink of atmospheric nitrate aerosols in this case. [Display omitted] • Nitrate is the main ion in fog water in urban area, mainly come from reaction of NO 2 with ·OH/H 2 O and hydrolysis of N 2 O 5. • Plenty of nitrate particles generated by reaction of NO 3 with HC/H 2 O during the fog event, mainly came from coal burning. • Fog water mainly settled nitrate particles newly generated during the fog event rather than that before the fog event. [ABSTRACT FROM AUTHOR]

From 2013, a significant decline in fine particulate matter (PM 2.5) occurred in most Chinese cities. In Nanjing, a capital city in the central of the Yangtze River Delta (YRD) region, the mass concentrations of total carbon (TC) in PM 2.5 decreased by approximately 48% during wintertime from 2014 to 2019. To provide detailed information in this trend, source apportionment of TC was carried out using a radiocarbon-(14C-) based method. In general, the average mass concentrations (and fossil fuel proportions) of TC, organic carbon (OC) and elemental carbon (EC) in six winters were 16.3 ± 8.5 μg m−3 (51%), 14.4 ± 7.8 μg m−3 (48%) and 2.0 ± 1.2 μg m−3 (65%), respectively. From 2014 to 2019, the reduction in TC was mainly attributed to the decline in non-fossil sources (6.4, 6.3–6.5 μg m−3) rather than fossil-fuel sources (3.6, 3.4–3.7 μg m−3) (medians, 10th-90th percentiles). The reduction of OC (9.1 μg m−3) was mainly attributed to OC from biomass burning (5.3, 4.6–6.1 μg m−3) and secondary formation from fossil-fuel sources (3.3, 2.6–3.9 μg m−3). Although the inter-annual variations for EC were less obvious, the reduction was dominated by the variations in non-fossil emissions (i.e., biomass burning). This study highlights the important role of non-fossil source control in the reduction of TC mass concentration in the YRD. Strategies of future emission control may pay more attention to both biomass burning emissions and secondary organic aerosols from precursors originating from fossil sources. [Display omitted] •Source apportionment was carried out using a14C-based method for six winters. •Nearly 2/3 of the declined TC was attributed to the decrease of non-fossil emissions. •Reduction of SOC ff should be considered more in the future. [ABSTRACT FROM AUTHOR]

Secondary inorganic aerosols, including sulfate, nitrate, and ammonium (SNA), are the predominant components of fine particles (PM 2.5). Reasonable representations of SNA formation in numerical models can largely improve the predictions of PM 2.5 concentrations and effectively help implement emission control strategies. Despite the Atmospheric Pollution Prevention and Control Action Plan has been implemented since 2013, PM 2.5 concentration during 2017 in Nanjing, one of the megacities in China, still exceeded the World Health Organization-recommended safe level (35 μg m−3). In this study, WRF-Chem model was applied to simulate aerosol chemical components in PM 2.5 during April 2016 and January 2017 in Nanjing, and the simulations are evaluated with in-situ observations. Our results show that the model can reasonably reproduce the temporal variability of PM 2.5 in two seasons, but significantly underestimate the sulfate concentrations by 71% (84%) in April (January), and overestimate the nitrate concentrations by 67% (45%) in April (January). The simulated ammonium is overall consistent with the observations. Meanwhile, the model tends to overestimate SO 2 concentrations by 20% (74%) in April (January). Several sensitivity studies are conducted to explore the mechanisms for underestimation of sulfate and overestimation of nitrate, and found that the conversion rate of SO 2 to sulfate is significantly underestimated in the model. Tripling the gas-phase oxidation rate of SO 2 by OH only enhances sulfate by 67% (72%) in April (January), indicating gas-phase oxidation is not the main causes for the underestimations in the model. However, inclusion of SO 2 heterogeneous oxidation in aerosol water can largely increase the simulated sulfate by 84% (196%) in April (January), and also better reproduce the diurnal variations of sulfate compared to the reference run. It should be noted that the simulated sulfate is still 47% (53%) lower than the observations in April (January), though inclusion of heterogeneous reaction can substantially improve the simulation performance of SNA. • SO 4 underestimates by 71% (84%), while NO 3 overestimates by 45% (67%) in Apr. (Jan.). NH 4 is consistent with the observation. • Underestimated SO 4 is accompanied by overestimated SO 2 by 27% (74%) in Apr. (Jan.), indicating SO 2 oxidation rate may be low. • Compared to the reference run, tripling SO 2 gas-phase oxidation rate only increases SO 4 by 67% (72%) in Apr. (Jan.). • Incorporating SO 2 heterogeneous reaction in aerosol water can increase SO 4 y 84% (196%) in Apr. (Jan.). • Incorporating SO 2 heterogeneous reaction can also better reproduce the observed diurnal variation. [ABSTRACT FROM AUTHOR]