Seasonal variations and chemical characteristics of PM(2.5) in Wuhan, central China

Short-term exposures to PM2.5, PM2.5 chemical components, and antenatal depression: Exploring the mediating roles of gut microbiota and fecal short-chain fatty acids

BACKGROUND

PM2.5 and its chemical components increase health risks and are associated with depression and gut microbiota. However, there is still limited evidence on whether gut microbiota and short-chain fatty acids (SCFAs) mediate the association between PM2.5, PM2.5 chemical components, and antenatal depression. The purpose of this study was to investigate the mediating role of maternal gut microbiota in correlations between short-term exposure to PM2.5, short-term exposure to PM2.5 chemical components, and antenatal depression.

METHODS

Demographic information and stool samples were collected from 75 pregnant women in their third trimester. Their exposure to PM2.5 and PM2.5 chemical components was measured. Participants were divided into the non-antenatal depression group or the antenatal depression group according to the cut-off of 10 points on the Edinburgh Postnatal Depression Scale (EPDS). The gut microbiota were analyzed using the 16 S rRNA-V3/V4 gene sequence, and the concentration of PM2.5 and its chemical components was calculated using the Tracking Air Pollution in China (TAP) database. Gas chromatography-mass spectrometry was used to analyze SCFAs in stool samples. In order to assess the mediating effects of gut microbiota and SCFAs, mediation models were utilized.

RESULTS

There were significant differences between gut microbial composition and SCFAs concentrations between the non-antenatal depression group and the antenatal depression group. PM2.5 and its chemical components were positively associated with EPDS scores and negatively associated with genera Enterococcus and Enterobacter. Genera Candidatus_Soleaferrea (β = -7.21, 95%CI -11.00 to -3.43, q = 0.01) and Enterococcus (β = -2.37, 95%CI -3.87 to -0.87, q = 0.02) were negatively associated with EPDS scores, indicating their potential protective effects against antenatal depression. There was no significant association between SCFAs and EPDS scores. The mediating role of Enterococcus between different lagged periods of PM2.5, PM2.5 chemical component exposure, and antenatal depression was revealed. For instance, Enterococcus explained 29.23% (95%CI 2.16-87.13%, p = 0.04) of associations between PM2.5 exposure level at the day of sampling (lag 0) and EPDS scores.

CONCLUSION

Our study highlights that Enterococcus may mediate the associations between PM2.5, PM2.5 chemical components, and antenatal depression. The mediating mechanism through which the gut microbiota influences PM2.5-induced depression in pregnant women still needs to be further studied.

Nitrogen and oxygen isotope characteristics, formation mechanism, and source apportionment of nitrate aerosols in Wuhan, Central China

Understanding the sources and formation mechanisms of nitrate in PM2.5 is important for effective and precise prevention and control of particulate matter pollution. In this study, we detected stable nitrogen and oxygen isotope signatures of NO- 3 (expressed as δ15N-NO- 3 and δ18O-NO3-) in PM2.5 samples in Wuhan, the largest city in central China. The sources and formation pathways of NO3- were quantitatively analyzed using the modified version of the Bayesian isotope mixing (MixSIR) model, and the regional transport characteristics of NO3- were analyzed using the hybrid single-particle Lagrangian integrated trajectory (HYSPLIT) model and concentration-weighted trajectory (CWT) method. The results showed that NO3- significantly contributed to the ambient PM2.5 pollution and its driving effect increased with the gradient of pollution level. The average δ15N-NO3- and δ18O-NO3- values were 4.7 ± 0.9 ‰ and 79.7 ± 2.9 ‰, respectively. δ15N-NO3- and δ18O-NO3- were more enriched in winter and increased dramatically in heavily polluted days. The reaction pathway of NO2 + OH dominated nitrate formation in summer, while the reaction pathway of N2O5+ H2O dominated in other seasons and contributed more in polluted days than clean days. The contributions of vehicle emission, coal combustion, biomass burning, biogenic soil emission, and ship emission sources to NO3- were 26.4 %, 23.4 %, 22.8 %, 15.3 %, and 12.1 %, respectively. In addition to local emissions, air mass transport from the northern China had a significant impact on particulate NO3- in Wuhan. Overall, we should pay special attention to vehicle and ship emissions and winter coal combustion emissions in future policymaking.

Impact of antioxidants on PM2.5 oxidative potential, radical level, and cytotoxicity

Antioxidants are typically seen as agents that mitigate environmental health risks due to their ability to scavenge free radicals. However, our research presents a paradox where these molecules, particularly those within lung fluid, act as prooxidants in the presence of airborne particulate matter (PM2.5), thus enhancing PM2.5 oxidative potential (OP). In our study, we examined a range of antioxidants found in the respiratory system (e.g., vitamin C, glutathione (GSH), and N-acetylcysteine (NAC)), in plasma (vitamin A, vitamin E, and β-carotene), and in food (tert-butylhydroquinone (TBHQ)). We aimed to explore antioxidants' prooxidant and antioxidant interactions with PM2.5 and the resulting OP and cytotoxicity. We employed OH generation assays and electron paramagnetic resonance assays to assess the pro-oxidative and anti-oxidative effects of antioxidants. Additionally, we assessed cytotoxicity interaction using a Chinese hamster ovary cell cytotoxicity assay. Our findings revealed that, in the presence of PM2.5, all antioxidants except vitamin E significantly increased the PM2.5 OP by generating more OH radicals (OH generation rate: 0.16-24.67 pmol·min-1·m-3). However, it's noteworthy that these generated OH radicals were at least partially neutralized by the antioxidants themselves. Among the pro-oxidative antioxidants, vitamin A, β-carotene, and TBHQ showed the least ability to quench these radicals, consistent with their observed impact in enhancing PM2.5 cytotoxicity (PM2.5 LC50 reduced to 91.2 %, 88.8 %, and 75.1 % of PM2.5's original level, respectively). Notably, vitamin A and TBHQ-enhanced PM2.5 OP were strongly associated with the presence of metals and organic compounds, particularly with copper (Cu) contributing significantly (35 %) to TBHQ's pro-oxidative effect. Our study underscores the potential health risks associated with the interaction between antioxidants and ambient pollutants.

Vertical changes of PM2.5 driven by meteorology in the atmospheric boundary layer during a heavy air pollution event in central China

Regional PM_2.5 transport is a crucial factor affecting air quality, and the meteorological mechanism in the atmospheric boundary layer (ABL) has not been fully understood over the receptor region in the regional transport of air pollutants. Based on the intensive vertical measurements of air pollutants and meteorology in the ABL during a transport-induced heavy air pollution event in Xiangyang, an urban site over a receptor region in central China, we investigated the meteorological mechanism in vertical PM_2.5 changes in the ABL for heavy air pollution over the receptor region. Driven by northerly winds, regional PM_2.5 transport was built from upstream northern China to downstream central China, where the observed ABL structures were unstable throughout the air pollution event. We assessed the ABL structures with meteorological and PM_2.5 profiles at growth, maintenance, and dissipation stages, and elucidated the mechanism of regional PM_2.5 transport inducing air pollution over the receptor region with the contribution of thermal and mechanical factors. The regional PM_2.5 transport was concentrated in the upper ABL over the downwind receptor region with high PM_2.5 concentrations at altitudes of 600-800 m, where the transported PM_2.5 peaks were downwards mixed by vertical wind shear, forming the vertical PM_2.5 transport from the upper ABL to near-surface in the growth stage; the weakened winds and less unstable structures in the ABL favored the sustained pollution with slight vertical PM_2.5 changes in the maintenance stage, which was dominated by thermal factors with 87 % contribution; the removal of PM_2.5 was triggered by increasing winds from the upper ABL, activating the dissipation of heavy PM_2.5 pollution with the mechanical effect accounting for 60 % in the dissipation stage. These findings could improve our understanding of ABL's influence on air pollution over the receptor region with implications for the regional transport of air pollutants in environmental changes.

Policy-driven variations in oxidation potential and source apportionment of PM2.5 in Wuhan, central China

China has implemented several control measures to mitigate PM_2.5 pollution and improve air quality, such as the Action Plan for the Prevention and Control of Air Pollution (APPCAP). To comprehensively assess the changes in ambient PM_2.5 concentrations and the corresponding health risk with the implementation of APPCAP, this study examined PM_2.5 samples collected in Wuhan in 2012/2013 and 2018 for water-soluble ions, carbonaceous fractions, and elements, respectively. Dithiothreitol (DTT) assay was used to determine the oxidation potential (OP) of PM_2.5. The positive matrix factorization (PMF) model and the multiple linear regression (MLR) model were used to analyze PM_2.5 sources and the contribution of each source to the OP of PM_2.5. The results showed that PM_2.5 concentrations in Wuhan decreased significantly, however, there was little change in the health risk and a significant increase in intrinsic toxicity. DTT_v (the volume-normalized dithiothreitol) showed high correlations (r > 0.5, p < 0.01) with water-soluble organic carbon (WSOC), organic carbon (OC), secondary ions (NO₃^-, SO₄^2-, and NH₄⁺), and elements. Compared to 2012/2013, the contribution of vehicle emissions and secondary aerosol sources to PM_2.5 increased significantly in 2018. Biomass burning sources significantly contribute to DTT_v in the summer and autumn, and secondary aerosol sources significantly contribute to DTT_v in winter. The human health impacts from coal combustion sources remained high, while vehicle emission sources increased. In the context of decreasing PM_2.5 concentrations, the role of vehicle emissions health impacts is increasingly significant due to the large increment in vehicle ownership and high inherent OP. Therefore, targeting vehicle emissions for control is of great importance for human health and needs to be given great attention in future policymaking.

Rainfall characteristics significantly affect the scavenging of water-soluble ions attached to leaves

Precipitation is considered the most effective way to remove particulate matter from the leaves of plants. Changes in rainfall characteristics can affect the scavenging processes of particulate matter from leaves. In order to better understand the dynamics of PM scavenging during rainfall, especially the water-soluble ions components, leaves from the 11 plant species (trees, shrubs, terrestrial herbs, wetland plants) from the Olympic park were sampled and used in indoor experiments. During the experiments, the rainfall intensity was set at 30 mm/h, 45 mm/h, and 60 mm/h, and the duration was divided into 0-20 min, 20-40 min, and 40-60 min. The sampled plant leaves were set in the experiments at 1 m and 3 m height from the ground. Concentrations and compositions of nine water-soluble ions of rainfall samples were analyzed in this experiment. The results revealed that SO₄^2-, Ca²⁺, and Na⁺ were the most abundant ionic species removed from the leaves, and NO₃^- ranked fourth, followed by Cl^-, Mg²⁺ K⁺, NH₄⁺, and F^-. The ions concentration of rainfall samples decreased when the rain intensity increased from 30 to 45 mm/h and when the rain intensity increased to 60 mm/h. The efficiency of scavenging during different rainfall durations depends on the ionic species. Na⁺, Mg²⁺, Ca²⁺, and SO₄^2- concentrations increased with the increase in rainfall duration, whereas those of NH₄⁺, K⁺, and Cl^- decreased. The effect of leaf height on ions concentration of rainfall samples was also different among the ionic species: Na⁺, Mg²⁺, Ca²⁺, NO₃^-, and F^- concentrations were significantly higher at 1 m compared with 3 m. The principal component analysis of ions in rainfall samples revealed two main sources of particulate matter in our study. One is from vehicle exhaust and industrial and agricultural pollution. The other is agricultural combustion and ground dust sources. The results of the above study can provide a basis and theoretical support for the establishment of urban cleaning systems and the prevention of air pollution.

Characteristics and Weekend Effect of Air Pollution in Eastern Jilin Province

Using the hourly monitoring data of pollutants from 16 automatic atmospheric monitoring stations in eastern Jilin Province from 2015 to 2020, this paper analyzed the temporal and spatial distribution laws of CO, SO2, NO2, PM10, PM2.5, and O3 in eastern Jilin Province. At the same time, the regional transport pathways of pollutants were analyzed using the hybrid single-particle Lagrangian integrated trajectory (HYSPLIT) model; the potential source contribution function (PSCF) analyzed the potential source area of PM2.5. Finally, the “weekend effect” of CO, NO2, PM2.5, and O3 was analyzed. The results showed that the six pollutants showed a downward trend year by year. The concentrations of O3, PM10, and PM2.5 were higher in northwest Jilin, and the concentrations of SO2 and CO were higher in southwest Jilin. Except for CO, the seasonal variation of pollutants was pronounced. Except for O3, most pollutants had the highest concentration in winter. Hourly variation analysis described that SO2 and O3 had only one peak in a day, and the other four pollutants showed “double peak” hourly variation characteristics. The study area was mainly affected by the airflow pathway from northwest and southwest. The weight potential source contribution function (WPSCF) high-value area of PM2.5 was northwest and southwest. O3 showed a “negative weekend effect”, and NO2 and CO showed a “positive weekend effect”.

Benefits of refined NH3 emission controls on PM2.5 mitigation in Central China

Atmospheric ammonia (NH₃) is one of the most crucial precursors of secondary inorganic aerosols. However, its emission control is still weakness over China. NH₃ emission inventories of 2015 with and without considering a set of refined emission reduction strategies covering seven major NH₃ emission sources were constructed in Central China. GEOS-Chem model simulations were conducted to quantify the benefits of NH₃ emission reduction on PM_2.5 mitigation in four typical months (January, April, July and October). The results showed that these control strategies could reduce approximately 47.0% (152 Gg) of the total NH₃ emissions in Hubei Province, with the agricultural (livestock and fertilizer application) source being reduced the most (133 Gg). NH₃ had a significant nonlinear relationship with sulfate, nitrate, ammonium and PM_2.5. NH₃ emission reduction exerted less effect on sulfate mitigations (the annual average sensitivity was 4.5%), but it obviously alleviated nitrate, ammonium and thus PM_2.5, with the annual average sensitivities of 81.9%, 34.8% and 22.0%, respectively. The average provincial concentrations of PM_2.5 were alleviated by 11.2% in January, 10.6% in October, 10.2% in April and 9.3% in July through NH₃ emission reduction by 47.0%. The reduction benefits were more pronounced in high NH₃ emission areas, such as Yichang, with the PM_2.5 reduction of 14.4% in January. This research could provide scientific support for formulating NH₃ emission reduction policies to further mitigate PM_2.5 pollution.

Responses of surface O3 and PM2.5 trends to changes of anthropogenic emissions in summer over Beijing during 2014-2019: A study based on multiple linear regression and WRF-Chem

Owing to the implementation of air pollution control actions, anthropogenic emissions in Beijing have changed in recent years. Understanding the impact of changes in anthropogenic emissions on O₃ and PM_2.5 trends is helpful for developing air quality management strategies. Herein, we investigated the variations of air pollutants in summer over Beijing using long-term data sets from 2014 to 2019, and explored the responses of O₃ and PM_2.5 trends to changes in anthropogenic emissions based on multiple linear regression (MLR) analysis and WRF-Chem model. The results indicated a significant decrease in PM_2.5, but a near constant level of O₃ during 2014-2019. The decrease rate of PM_2.5, which was lower than that of SO₂, might be due to the effect of NO₂ on atmospheric PM_2.5. Both the slightly increasing correlations between PM_2.5 and NO₂ and the WRF-Chem model simulations implied that atmospheric PM_2.5 in Beijing is trending to be more sensitive to NO_x than SO₂. The emissions of NO_x and VOCs from industry and transportation were found to make great contribution to O₃ production in Beijing. Due to the titration of NO_x in VOC-limited regime, the relatively low emission ratios of NO_x and VOCs from industry and transportation in Beijing provided convincing evidence for the persistently high O₃ concentrations during 2014-2019. However, the noticeable increase of the O₃ trends in other areas (e.g., Hebei, Tianjin) could be explained by the significant decline in the emission ratios of NO_x and VOCs from anthropogenic emissions especially industry during 2014-2019. Controlling the emission of NO_x can substantially reduce PM_2.5 pollution, but may aggravate O₃ pollution, and thus effective VOC emission control strategies need to be considered for simultaneously controlling O₃ and PM_2.5 pollution in Beijing and other regions of China.

Monthly Global Estimates of Fine Particulate Matter and Their Uncertainty

Annual global satellite-based estimates of fine particulate matter (PM2.5) are widely relied upon for air-quality assessment. Here, we develop and apply a methodology for monthly estimates and uncertainties during the period 1998-2019, which combines satellite retrievals of aerosol optical depth, chemical transport modeling, and ground-based measurements to allow for the characterization of seasonal and episodic exposure, as well as aid air-quality management. Many densely populated regions have their highest PM2.5 concentrations in winter, exceeding summertime concentrations by factors of 1.5-3.0 over Eastern Europe, Western Europe, South Asia, and East Asia. In South Asia, in January, regional population-weighted monthly mean PM2.5 concentrations exceed 90 μg/m3, with local concentrations of approximately 200 μg/m3 for parts of the Indo-Gangetic Plain. In East Asia, monthly mean PM2.5 concentrations have decreased over the period 2010-2019 by 1.6-2.6 μg/m3/year, with decreases beginning 2-3 years earlier in summer than in winter. We find evidence that global-monitored locations tend to be in cleaner regions than global mean PM2.5 exposure, with large measurement gaps in the Global South. Uncertainty estimates exhibit regional consistency with observed differences between ground-based and satellite-derived PM2.5. The evaluation of uncertainty for agglomerated values indicates that hybrid PM2.5 estimates provide precise regional-scale representation, with residual uncertainty inversely proportional to the sample size.

Industrial Source Contributions and Health Risk Assessment of Fine Particle-Bound Polycyclic Aromatic Hydrocarbons (PAHs) during Spring and Late Summer in the Baoshan Area, Shanghai

The main objective of this study was to examine the chemical characteristics, possible sources, and health risks of fine particle-bound Polycyclic Aromatic Hydrocarbons (PAHs) in the Baoshan area of Shanghai. Here, ambient particles with five-size ranges were collected during the spring and late summer of 2017. The PAHs were determined by the Gas Chromatography-Mass Spectrometry (GC-MS). Our results showed that the average mass concentration of 13 species of PAHs in spring and in late summer was 4.83 (1.88~12.1) ng/m3 and 4.27 (2.09~5.75) ng/m3 in Total Suspended Particles (TSPs), respectively. The higher PAH ratios (PM1.1/TSPs) indicated that PAHs are mainly concentrated in PM1.1, especially in late summer. The values of BaA/(BaA+CHR) were under 0.50 and IcdP/(IcdP+BghiP) were in range from 0.20 to 0.50 for TSP and PM1.1, suggesting that petroleum combustion and diesel emissions could be considered as key sources of PAHs, which tend to be associated with PM1.1. Moreover, the Principal Component Analysis (PCA) in PM1.1 identified the main PH sources, which include stationary and diesel emissions. The air mass backward trajectories and wind direction analysis showed that air masses were mainly derived from marine sources across the local industry area in late summer. Individual Carcinogenic Risk Inhalation (ILCR) was over 10−6 among the total six age groups in both of the sampling periods in TSPs, indicating the possible carcinogenic risk, especially for children and the young age group. Toxic PAHs belong to Heavy Molecular Weight (HMW) PAHs, especially Benzo[a]pyrene (BaP). Compared with PM1.1–2.0, the Combustion-Derived PAHs group (COMPAHs) and Carcinogenic PAHs (CANPAHs) were highly concentrated in PM1.1. Stationary sources, such as the developed steel industry, made a great contribution to the level of PAHs, especially in late summer.

Composition analysis of PM2.5 at multiple sites in Zhengzhou, China: implications for characterization and source apportionment at different pollution levels

Zhengzhou is one of the most heavily polluted cities in China. This study collected samples of PM_2.5 (atmospheric fine particulate matter with aerodynamic diameter ≤ 2.5 μm) at five sites in different functional areas of Zhengzhou in 2016 to investigate the chemical properties and sources of PM_2.5 at three pollution levels, i.e., PM_2.5 ≤ 75 μg/m³ (non-pollution, NP), 75 μg/m³ < PM_2.5 ≤ 150 μg/m³ (moderate pollution, MP), and PM_2.5 > 150 μg/m³ (heavy pollution, HP). Chemical analysis was conducted, and source categories and potential source region were identified for PM_2.5 at different pollution levels. The health risks of toxic elements were evaluated. Results showed that the average PM_2.5 concentration in Zhengzhou was 119 μg/m³, and the sum of the concentrations of SO₄^2-, NO₃^-, and NH₄⁺ increased with the aggravation of pollution level (23, 42, and 114 μg/m³ at NP, MP, and HP days, respectively). Positive Matrix Factorization analysis indicated that secondary aerosols, coal combustion, vehicle traffic, industrial processes, biomass burning, and dust were the main sources of PM_2.5 at three pollution levels, and accounted for 38.4%, 21.6%, 16.7%, 7.4%, 7.7%, and 8.1% on HP days, respectively. Trajectory clustering analysis showed that close-range transport was one of the dominant factors on HP days in Zhengzhou. The potential source areas were mainly located in Xinxiang, Kaifeng, Xuchang, and Pingdingshan. Significant risks existed in the non-carcinogenic risk of As (1.4-2.3) for children at three pollution levels and the non-carcinogenic risk of Pb (1.0-1.4) for children with NP and MP days.

Assessment of 12 Essential and Toxic Elements in Whole Blood of Pregnant and Non-pregnant Women Living in Wuhan of China

Exposures to toxic trace elements and deficiencies of essential elements during pregnancy are associated to various birth complications. Assessment of the trace elements in pregnant women living in specific areas is important for biomonitoring. A total of 196 healthy pregnant women absent of pregnancy complications living in Wuhan of China and 210 healthy non-pregnant women were enrolled. The whole blood were collected. The toxic element chromium (Cr), arsenic (As), cadmium (Cd), mercury (Hg), thallium (Tl), and lead (Pb) and essential elements magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), and zinc (Zn) were determined by using a inductively coupled plasma mass spectrometry (ICP-MS)-based method. All the metal(loid)s, except for Cd, Hg, and Tl, showed different levels in whole blood of the pregnant women compared with the non-pregnant women (p < 0.05), among which Mg, Fe, As, and Pb were lower while Ca, Cr, Mn, Cu, and Zn were higher. Moreover, whole blood levels of Mg, Mn, Fe, Cu, and Zn showed significant variations among different gestational ages, while As and Cd showed significant variations among different maternal ages. In addition, Fe-Mg, Fe-Zn, Cu-Ca, and Hg-As were found to be correlated positively in whole blood of the pregnant women, while Fe-Ca, Zn-Ca, and Fe-Cu were correlated negatively. The systematic information of toxic and essential elements in whole blood of pregnant women living in Wuhan of China can provide important guidance for the supplementation of essential elements during pregnancy and for biomonitoring of environmental overexposure.

Source Apportionment and Health Risk Assessment of Metal Elements in PM2.5 in Central Liaoning’s Urban Agglomeration

To better understand the source and health risk of metal elements in PM2.5, a field study was conducted from May to December 2018 in the central region of the Liaoning province, China, including the cities of Shenyang, Anshan, Fushun, Benxi, Yingkou, Liaoyang, and Tieling. 24 metal elements (Na, K, V, Cr, Mn, Co, Ni, Cu, Zn, As, Mo, Cd, Sn, Sb, Pb, Bi, Al, Sr, Mg, Ti, Ca, Fe, Ba, and Si) in PM2.5 were measured by ICP-MS and ICP-OES. They presented obvious seasonal variations, with the highest levels in winter and lowest in summer for all seven cities. The sum of 24 elements were ranged from to in these cities. The element mass concentration ratio was the highest in Yingkou in the spring (26.15%), and the lowest in Tieling in winter (3.63%). The highest values of elements in PM2.5 were mostly found in Anshan and Fushun among the studied cities. Positive matrix factorization (PMF) modelling revealed that coal combustion, industry, traffic emission, soil dust, biomass burning, and road dust were the main sources of measured elements in all cities except for Yingkou. In Yingkou, the primary sources were identified as coal combustion, metal smelting, traffic emission, soil dust, and sea salt. Health risk assessment suggested that Mn had non-carcinogenic risks for both adults and children. As for Cr, As, and Cd, there was carcinogenic risks for adults and children in most cities. This study provides a clearer understanding of the regional pollution status of industrial urban agglomeration.

Importance of meteorology in air pollution events during the city lockdown for COVID-19 in Hubei Province, Central China

Compared with the 21-year climatological mean over the same period during 2000-2020, the aerosol optical depth (AOD) and Angstrom exponent (AE) during the COVID-19 lockdown (January 24-February 29, 2020) decreased and increased, respectively, in most regions of Central-Eastern China (CEC). The AOD (AE) values decreased (increased) by 39.2% (29.4%) and 31.0% (45.3%) in Hubei and Wuhan, respectively, because of the rigorous restrictions. These inverse changes reflected the reduction of total aerosols in the air and the contribution of the increase in fine-mode particles during the lockdown. The surface PM_2.5 had a distinct spatial distribution over CEC during the lockdown, with high concentrations in North China and East China. In particular, relatively high PM_2.5 concentrations were notable in the lower flatlands of Hubei Province in Central China, where six PM_2.5 pollution events were identified during the lockdown. Using the observation data and model simulations, we found that 50% of the pollution episodes were associated with the long-range transport of air pollutants from upstream CEC source regions, which then converged in the downstream Hubei receptor region. However, local pollution was dominant for the remaining episodes because of stagnant meteorological conditions. The long-range transport of air pollutants substantially contributed to PM_2.5 pollution in Hubei, reflecting the exceptional importance of meteorology in regional air quality in China.

Evolution of Aerosols in the Atmospheric Boundary Layer and Elevated Layers during a Severe, Persistent Haze Episode in a Central China Megacity

Aerosol vertical profiling is crucial to understand the formation mechanism and evolution processes of haze, which have not yet been comprehensively clarified. In this study, we investigated a severe, persistent haze event in Wuhan (30.5° N, 114.4° E), China during 5–18 January 2013 by the use of a polarization lidar, a Cimel sun photometer, meteorological datasets, and the hybrid single-particle Lagrangian integrated trajectory (HYSPLIT) model, focusing on the time–height evolution of aerosols in both the atmospheric boundary layer (ABL) and elevated layers. During the haze period, the integrated particle depolarization ratio was 0.05 ± 0.02, and the fine mode fraction reached 0.91 ± 0.03, indicating haze particles were rather spherical and predominately submicron, that is, of anthropogenic nature. Compared with the clear period, columnar aerosol optical depth at 500 nm tripled to 1.32 ± 0.31, and the strongest enhancement in aerosol concentration occurred from near the ground to an altitude of 1.2 km during the haze period. The daytime evolution of aerosol vertical distribution in the ABL exhibited a distinct pattern under haze weather. Abundant particles accumulated below 0.5 km in the morning hours due to stable meteorological conditions, including a strong surface-based inversion (4.4–8.1 °C), late development (from 1000–1100 LT) of the convective boundary layer, and weak wind (<4 m∙s−1) in the lowermost troposphere. In the afternoon, improved ventilation delivered an overall reduction in boundary layer aerosols but was insufficient to eliminate haze. Particularly, the morning residual layer had an optical depth of 0.29–0.56. It influenced air quality indirectly by weakening convective activities in the morning and directly through the fumigation process around noon, suggesting it may be an important element in aerosol–ABL interactions during consecutive days with haze. Our lidar also captured the presence of the elevated aerosol layers (EALs) embodying regional/long-range transport. Most of the EALs were observed to subside to <1.2 km and exacerbate the pollution level. Backward trajectory analysis and lidar data revealed the EALs originated from the transport of anthropogenic pollutants from the Sichuan Basin, China, and of dust from the deserts in the northwest. They were estimated to contribute ~19% of columnar aerosol-loading, pointing to a non-negligible role of transport during the intense pollution episode. The results could benefit the complete understanding of aerosol–ABL interactions under haze weather and air quality forecasting and control in Wuhan.

Atmospheric outflow of anthropogenic iron and its deposition to China adjacent seas

Atmospheric deposition of iron (Fe) can increase marine primary productivity, consequently affect ocean biogeochemical cycles and climate change. In this study, we develop an adaptor to generate anthropogenic Fe emission inventories for China in 2012 and 2016 via anthropogenic PM_2.5 emissions from Multi-resolution Emission Inventory for China (MEIC) using local source-specific mass fractions of Fe in PM_2.5. Using the generated emission inventories, we simulated Fe concentrations as well as dry deposition fluxes to China marginal seas using a WRF-CMAQ model during four campaign periods. The simulated Fe concentrations are in good agreement with observations except for those in presence of severe dust-intrusion events (NMB -13% ~ -27%), indicating a reasonably good performance of the generated Fe emissions and leaving the large underestimation of Fe concentrations mainly due to nature dust emissions. Simulated Fe concentrations over China marginal seas are in the range of 62-6.5 × 10² ng m^-3, providing 2.0-12.5 μg m^-2 d^-1 to the seas during the study periods. We also found that inputs of total Fe in PM_2.5 to the seas in presence of dust-intrusion events are 3 and 13 times larger than those in presence of haze events or on less polluted days. Due to lower Fe solubility in nature mineral aerosols than in anthropogenic aerosols, dry deposition fluxes of bioavailable Fe on haze days almost double that in dust days. The total anthropogenic emissions of Fe over China in 2012 and 2016 are estimated as 5.5 × 10² Gg and 3.3 × 10² Gg, respectively. Iron and steel industry are the dominant sources of Fe, accounting for 59-63% of the total anthropogenic Fe emissions. Geotropically, stronger emissions per area were distributed in eastern China, e.g., 2.3 to 15.4 ng m^-2 s^-1 in eastern China versus <0.4 ng m^-2 s^-1 in western China.

Distribution characteristics and policy-related improvements of PM2.5 and its components in six Chinese cities

This study presents the distribution characteristics and possible sources of fine particulate matter (PM_2.5) and its components, as well as policy-related pollution reduction in the Chinese cities of Jinan, Shijiazhuang (SJZ), Chengdu, Wuxi, Wuhan, and Harbin (HRB). PM_2.5 samples were collected using mid-volume samplers during the autumn of 2017 in all six cities. The samples were analyzed to determine the ambient PM_2.5 compositions, including the concentrations of water-soluble inorganic ions (WSIIs), carbonaceous aerosols, and elements concentrations. The chemical ratios of organic carbon to elemental carbon and nitrate to sulfate as well as the enrichment factors of elements were calculated to establish the possible sources of PM_2.5 in all six cities. The highest PM_2.5 concentration was 152 μg/m³ in SJZ, while the lowest concentration was 47 μg/m³ in HRB. During the sampling period in these six cities, the PM_2.5 concentrations exceeded the World Health Organization recommended daily average air quality guidelines by 2.4-6.1 times, and WSIIs, carbonaceous aerosols, and elements accounted for 31.8%-61.6%, 9.8%-35.1%, and 0.9%-2.5% of the PM_2.5, respectively. In 2013, the Chinese government formulated the Air Pollution Prevention and Control Action Plan (APPCAP) for controlling air pollution, and effective measures have been implemented since then. Compared with previous studies conducted during 2009-2013 before the implementation of the APPCAP, the concentrations of PM_2.5 and most of its components decreased to varying degrees, and large changes in the chemical ratios of PM_2.5 components were observed. These results indicate that PM_2.5 sources vary among these six cities and that China has improved the ambient air quality in these cities through the implementation of air pollution control policies. The APPCAP have achieved considerable results in continuously reducing pollution concentrations, although the air pollution concentrations observed in this study remain high compared with those of other countries.

Trends in ambient air pollution levels and PM2.5 chemical compositions in four Chinese cities from 1995 to 2017

An in-depth analysis of the specific evolution of air pollution in a given city can provide a better understanding of the chronic effects of air pollution on human health. In this study, we reported trends in ambient concentrations of particulate matter (PM) and gaseous pollutants [sulfur dioxide (SO₂), nitrogen dioxide (NO₂), and ozone (O₃)] from 1995 to 2017 and PM_2.5 composition for the period of 2000–2017 in Guangzhou, Wuhan, Chongqing, and Lanzhou. We provided socio-economic indicators to help explain the pollution trends. SO₂ and PM (including PM₁₀ and PM_2.5) concentrations showed a downward trend in recent years with the most notable reduction in SO₂ in Chongqing and PM_2.5 in Guangzhou. There was an overall flat trend for NO₂, while O₃ showed an upward trend in recent years except in Lanzhou. The majority of PM_2.5 mass was SO₄²⁻ (6.0–30 µg/m³) and organic carbon (6.0–38 µg/m³), followed by NO₃⁻ (2.0–12 µg/m³), elemental carbon (2.1–12 µg/m³), NH₄⁺ (1.0–10 µg/m³), K⁺ (0.2–2.0 µg/m³), and Cl⁻ (0.2–1.9 µg/m³). Except for secondary inorganic aerosols in Wuhan, annual average concentrations of all PM_2.5 constituents showed a declining trend after 2013, corresponding to the trend of PM_2.5. The secondary sources in PM_2.5 were found to be most prominent in Wuhan, while the most abundant EC and Cl⁻ in Lanzhou was attributed to the use of coal. Despite temporal and spatial variabilities across the four cities, coal combustion, traffic emissions, and secondary pollution have been the major sources of PM_2.5 pollution. These trends in ambient air pollution levels and PM_2.5 composition may help understand changes in health outcomes measured at different times within the time period of 1995–2017 in the four cities.

Pollution Characteristics, Chemical Compositions, and Population Health Risks during the 2018 Winter Haze Episode in Jianghan Plain, Central China

To determine the pollution characteristics, chemical compositions, and population health risks of PM2.5 at different pollution levels, PM2.5 samples were intensively collected during the long-lasting winter haze episode from 13–23 January 2018 in Xiantao in Jianghan Plain (JHP), central China. The higher PM2.5 levels during the severe pollution period were dominated by the WNW-NNE air-masses, whereas the lower PM2.5 concentrations during other pollution periods were mainly affected by the NE, S, and NW air-masses. The NO3−/SO42− and OC/EC ratios indicated a mixed contribution of intensive vehicle exhaust and secondary formation. The enrichment factor and geo-accumulation index for assessing the PM2.5-bound metal(loid)s contamination levels were positively correlated. Ingestion is the dominant exposure pathway of PM2.5-bound metal(loid)s for children and adults, followed by inhalation and dermal contact. As, Cr, and Pb may pose carcinogenic and non-carcinogenic risks, whereas Sb and V may only pose non-carcinogenic risks for children and adults. The population health risks may not depend on the pollution levels but depend on the PM2.5-bound metal(loid)s concentrations. PM2.5-bound metal(loid)s may pose much higher population health risks for adults compared to children. More attentions should be paid to the population health risks of PM2.5-bound metal(loid)s during a long-lasting winter haze episode in JHP.

Analysis of Pollution Characteristics and Influencing Factors of Main Pollutants in the Atmosphere of Shenyang City

Air pollution is one of the most concerning environmental problems in cities. Hourly data on pollutant concentrations from 11 automatic atmospheric monitoring stations and meteorological data in Shenyang from 2017 to 2019 were used to analyze the spatio-temporal variation rules of CO (carbon monoxide), SO2 (sulfur dioxide), NO2 (nitrogen dioxide), O3 (ozone), PM2.5 and PM10 (PM particles with an aerodynamic diameters of not more than 2.5 µm and 10 µm) and their relationships with meteorological parameters. Meanwhile, the regional transmission route of pollutants was analyzed by the hybrid single particle Lagrangian integrated trajectory (HYSPLIT) model. The results showed that the concentration of O3 in the northern area of the city was higher than that in the south; CO, SO2 and NO2 were relatively high in the urban center; and PM2.5 and PM10 were relatively high in the southwest. The average concentration of pollutants was lowest in 2019. The concentration of O3 was the highest in spring, while CO showed no significant variations between different seasons. The remaining pollutant concentrations appeared to be high in winter and low in summer. The cumulative concentrations of the six pollutants were the highest in March, and relatively low in July–September. The diurnal concentration variations of O3, CO and SO2 exhibited a “single peak,” while others showed a “double peak and double valley.” Temperature was positively correlated with O3 concentration and negatively correlated with others. Wind speed was negatively correlated with the concentration of PM2.5, NO2, and O3. The air quality of the main urban area in spring and summer was mainly affected by the coastal air flow, while it was mostly affected by the northwest air flow in autumn and winter.

Characterization, Pollution Sources, and Health Risk of Ionic and Elemental Constituents in PM2.5 of Wuhan, Central China

Atmospheric PM2.5 samples from Wuhan, China were collected during a winter period of February and a summer period of August in 2018. The average PM2.5 mass concentration in winter reached 112 μg/m3—about two-fold higher than that found in summer. Eight ionic species constituted 1/3 of PM2.5, whereas more than 85% represented secondary ionic aerosols (NO3−, SO42− and NH4+). Higher ratios of NO3−/SO42− (0.95–2.62) occurred in winter and lower ratios (0.11–0.42) occurred in summer showing the different contribution for mobile and stationary sources. Seventeen elemental species constituted about 10% of PM2.5, with over 95% Na, Mg, Al, Ca, Fe, K and Zn. Higher K-concentration occurred in winter indicating greater contribution from biomass and firework-burning. Carcinogenic risks by Cr, As, Cd, Ni and Pb in PM2.5 indicated that about 6.94 children and 46.5 adults among per million may risk getting cancer via inhalation during surrounding winter atmospheric sampling, while about 5.41 children and 36.6 adults have the same risk during summer. Enrichment factors (EFs) and elemental ratios showed that these hazardous elements were mainly from anthropogenic sources like coal and oil combustion, gasoline and diesel vehicles.

Associations of exposure to fine particulate matter during pregnancy with maternal blood glucose levels and gestational diabetes mellitus: Potential effect modification by ABO blood group

BACKGROUND

Previous studies have examined the relationships between prenatal fine particulate matter (PM_2.5) exposure and gestational diabetes mellitus (GDM), but the results were inconsistent. Furthermore, the possible effect modification by ABO blood group has not been explored.

OBJECTIVES

To assess the associations of PM_2.5 exposures during pregnancy with maternal glucose levels as well as GDM, and further to evaluate the potential effect modification by ABO blood group.

METHODS

Between January 2013 and January 2015, 4783 pregnant women were enrolled in our study based on a birth cohort in Wuhan. Daily PM_2.5 exposure levels for each woman during pregnancy were estimated using a spatial-temporal land-use regression model. Linear regressions with general estimating equations (GEE) were performed to assess the associations between trimester-specific PM_2.5 exposures and maternal glucose levels. Modified Poisson regressions with GEE analyses were used to evaluate the impacts of PM_2.5 exposures during each trimester on the risk of GDM. The associations of PM_2.5 exposure during the whole study period with glucose levels and GDM were estimated using multiple linear regression model and modified Poisson regression model, respectively. We conducted a stratified analysis to explore the potential effect modification by ABO blood group.

RESULTS

Among all the 4783 participants, 394 (8.24%) had GDM. Exposure to PM_2.5 was found to be positively associated with elevated fasting glucose level during the whole study period [0.382 mg/dL, 95% confidence interval (CI): 0.179-0.586, per 10 μg/m³ increase in PM_2.5], the first trimester (0.154 mg/dL ,95% CI: 0.017-0.291) and the second trimester (0.541 mg/dL, 95% CI: 0.390-0.692). No statistically significant results were observed between PM_2.5 and 1-h and 2-h glucose levels during any study period. Increased risks of GDM for each 10 μg/m³ increase in PM_2.5 levels were observed during the whole study period [relative risk (RR): 1.120, 95% CI: 1.021-1.228] and the first trimester (RR: 1.074, 95% CI: 1.012-1.141), but not the second trimester (RR: 1.035, 95% CI: 0.969-1.106). Stratified analysis indicated that the associations of PM_2.5 exposures with GDM were more pronounced among pregnant women with blood group A, but no significant effect modifications were observed.

CONCLUSION

Our study enriched epidemiological evidence linking PM_2.5 exposures during pregnancy to elevated maternal glucose levels and increased risk of GDM. More importantly, we first highlighted that the impact of PM_2.5 on GDM might be greater among pregnant women with blood group A.

Characteristics of Carbonaceous Matter in Aerosol from Selected Urban and Rural Areas of Southern Poland

The purpose of this study is to obtain a detailed picture of the spatial and seasonal variability of carbonaceous matter in southern Poland. Particulate matter (PM) samples from eight selected urban and rural background sites were analyzed for organic carbon (OC) and elemental carbon (EC) (thermal-optical method, “eusaar_2” protocol), and the content of secondary (SOC) and primary organic carbon (POC) was estimated. The OC and EC dynamics were further studied using each of the thermally-derived carbon fractions (OC1–4, PC, and EC1–4). Clear spatiotemporal variability of carbonaceous compounds concentrations was observed, with higher levels recorded during the heating season. The considered measurement sites differed particularly in the shares of SOC and POC, with higher values of POC contents especially in rural areas. In terms of the content of carbon fractions, the analyzed sites showed roughly the same characteristics, with PC, OC4, and OC2 as dominant fractions of OC and with clear dominance of EC3 and EC2 over other EC fractions. The results obtained as part of this work may be a valuable source of information about the actual status of the carbonaceous matter, which remains one of the least known components of atmospheric PM.

Temporal trend of arsenic in outdoor air PM2.5 in Wuhan, China, in 2015-2017 and the personal inhalation of PM-bound arsenic: implications for human exposure

Arsenic in fine air particulate matter (PM_2.5) has been identified as an important factor responsible for the morbidity of lung cancer, which has increased sharply in many regions of China. Some reports in China have shown that arsenic in the air exceeds the ambient air quality standard value, while long-term airborne arsenic concentrations in central China and human exposure via inhalation of PM-bound arsenic (inhalable airborne PM) have not been well characterized. In this study, 579 outdoor air PM_2.5 samples from Wuhan, a typical city in central China, were collected from 2015 to 2017, and arsenic was measured by inductively coupled plasma-mass spectrometry. Personal exposure to PM-bound arsenic via inhalation and urinary arsenic concentration were also measured. The concentrations of arsenic in PM_2.5 were in the range of 0.42-61.6 ng/m³ (mean 8.48 ng/m³). The average concentration of arsenic in 2015 (10.7 ng/m³) was higher than that in 2016 (6.81 ng/m³) and 2017 (8.18 ng/m³), exceeded the standard value. The arsenic concentrations in spring and winter were higher than those in summer and autumn. No significant differences (p > 0.05) were found among different sites. The daily intake of arsenic inhalation based on PM₁₀ samples collected by personal samplers (median, 10.8 ng/m³) was estimated. Urban residents inhaled higher levels of PM-bound arsenic than rural residents. Daily intake of arsenic via inhalation accounted for a negligible part (< 1%) of the total daily intake of arsenic (calculated based on excreted urinary arsenic); however, potential associations between the adverse effects (e.g., lung adenocarcinoma) and inhaled PM-bound arsenic require more attention, particularly for those who experience in long-term exposure. This study is the first report of a 3-year temporal trend of airborne PM_2.5-bound arsenic in central China.

An integrated chemical mass balance and source emission inventory model for the source apportionment of PM2.5 in typical coastal areas

The source apportionment of PM_2.5 is essential for pollution prevention. In view of the weaknesses of individual models, we proposed an integrated chemical mass balance-source emission inventory (CMB-SEI) model to acquire more accurate results. First, the SEI of secondary component precursors (SO₂, NO_x, NH₃, and VOCs) was compiled to acquire the emission ratios of these sources for the precursors. Then, a regular CMB simulation was executed to obtain the contributions of primary particle sources and secondary components (SO₄^2-, NO₃^-, NH₄⁺, and SOC). Afterwards, the contributions of secondary components were apportioned into primary sources according to the source emission ratios. The final source apportionment results combined the contributions of primary sources by CMB and SEI. This integrated approach was carried out via a case study of three coastal cities (Zhoushan, Taizhou, and Wenzhou; abbreviated WZ, TZ, and ZS) in Zhejiang Province, China. The regular CMB simulation results showed that PM_2.5 pollution was mainly affected by secondary components and mobile sources. The SEI results indicated that electricity, industrial production and mobile sources were the largest contributors to the emission of PM_2.5 gaseous precursors. The simulation results of the CMB-SEI model showed that PM_2.5 pollution in the coastal areas of Zhejiang Province presented complex pollution characteristics dominated by mobile sources, electricity production sources and industrial production sources. Compared to the results of the CMB and SEI models alone, the CMB-SEI model completely apportioned PM_2.5 to primary sources and simultaneously made the results more accurate and reliable in accordance with local industrial characteristics.

Decoupling PM2.5 emissions and economic growth in China over 1998-2016: A regional investment perspective

It is crucial to decouple economic growth from environmental pollution in China. This study aims to evaluate China's decoupling level between PM_2.5 emissions and economic growth from a regional investment perspective. Using the panel data of 30 Chinese provinces for the period of 1998-2016, this study combines decomposition analysis with decoupling analysis to identify the roles of conventional factors and three novel investment factors in the mitigation and decoupling of PM_2.5 emissions in China and its four sub-regions. The results show that China's PM_2.5 emissions were weakly decoupled to economic growth during the period of 1998-2016, as well as in China's four sub-regions. At the national level, investment scale played the dominant role while investment structure had a marginal effect in mitigating the decoupling level. In contrast, emission intensity was the largest driver in promoting the decoupling effect. At the regional level, emission intensity and investment efficiency accelerated the regional decoupling level, but the coupling effect from investment scale in the western region far exceeded those in other three sub-regions. At the provincial level, the investment structure of Inner Mongolia and investment scales of Xinjiang and Inner Mongolia had the greatest impacts on PM_2.5 emission growth. Finally, several policy recommendations are raised for China to mitigate its PM_2.5 emissions.

Validation of PM2.5 model particle through physicochemical evaluation and atherosclerotic plaque formation in ApoE-/- mice

PM_2.5 particles are regarded as prominent risk factors that contribute to the development of atherosclerosis. However, the composition of PM_2.5 is rather complicated. This study aimed to provide a model particle that simulates the behavior of actual PM_2.5, for subsequent use in exploring mechanisms and major complications arising from PM_2.5. To establish model particles of PM_2.5, a series of monodisperse SiO₂ microspheres with different average grain diameters were mixed according to the size distribution of actual PM_2.5. The organic carbon (OC) was removed from PM_2.5 and coated onto the SiO₂ model particle, to formulate simulant PM_2.5. Results showed that the size distribution of the model particle was highly approximate to that of the PM_2.5 core. The polycyclic aromatic hydrocarbon (PAHs) composition profile of the simulated PM_2.5 were approximate to PM_2.5, and loading efficiency was approximately 80%-120%. Furthermore, compared to the control, SiO₂-only model particle had negligible cytotoxicity on cell viability and oxidative stress of HUVECs, and marginal effect on the lipid metabolism and atherosclerotic plaque formation in ApoE^-/- mice. In contrast, simulated PM_2.5 exhibited similar cytotoxic and detrimental effects on lipid metabolism and atherosclerotic plaque formation with actual PM_2.5. Traffic-related PM_2.5 had negative effects on endothelial function and led to the formation of atherosclerosis via oxidative stress. The simulated PM_2.5 simulated the outcomes of actual PM_2.5 exposure. Here, we show that SiO₂ particle model cores coated with OC could significantly assist in the evaluation of the effects of specific organic compositions bound on PM_2.5, specifically in the context of environmental health and safety.

Characterization of aerosol chemical composition and the reconstruction of light extinction coefficients during winter in Wuhan, China

To evaluate light extinction contributions of aerosol chemical constituents and their impacts on atmospheric visibility, the PM_2.5 and its chemical components, light scattering (b_sp) and absorption (b_ap) were continuously measured in Wuhan from January to February 2018. The average of PM_2.5 concentration, b_sp and b_ap were 96.5 ± 13.7 μg m^-3, 564 ± 124 Mm^-1 and 44 ± 8 Mm^-1 during polluted days, respectively, which was about 2.0, 2.1 and 1.6 times higher than those of clean days, respectively. Compared with the clean days, the increase of the mass concentrations of SNA (SO₄^2-, NO₃^-, NH₄⁺) during polluted days was higher than those of organic (OC) and elemental (EC) carbon, indicated the increase of SNA was the main cause of air pollution. The PM_2.5 concentration threshold was 66 μg m^-3, corresponding to the visibility lower than 10 km. The revised Interagency Monitoring of Protected Visual Environments (IMPROVE) algorithm was used to reconstruct the light extinction coefficient (b_ext) in Wuhan. The sum of light extinction coefficients of (NH₄)₂SO₄, NH₄NO₃ and organic matter (OM) accounted for 70.5% and 83.9% of b_ext during clean and polluted days, respectively. The backward trajectory and potential source contribution function (PSCF) analysis revealed that regional transport accounted for 55.6% of the total airflow, which originated from south, northwest and west of Wuhan. The increases of (NH₄)₂SO₄ and NH₄NO₃ concentrations, emitted from local vehicle exhaust and coal combustion, and their hygroscopic growth in ambient were the major causes of pollution in Wuhan.

Oxidative potential of ambient PM2.5 in Wuhan and its comparisons with eight areas of China

Oxidative potential (OP) is a good indicator for assessing health risk associated with exposure to fine particulate matter (PM_2.5, <2.5 μm in aerodynamic diameter). In this study, 24-h ambient PM_2.5 samples were collected at three sampling sites throughout selected months of 2012 in Wuhan, Central China. Water soluble ions, metals, organic carbon (OC), elemental carbon (EC), levoglucosan, polycyclic aromatic hydrocarbons (PAHs), hopanes, and dicarboxylic acids were determined. The dithiothreitol (DTT) assay was used to characterize the oxidative potential of PM_2.5. Linear regression analysis and principal component analysis (PCA) were used to link OP to the individual redox-active components originating from diverse emission sources. The OP results from the three sites in Wuhan, combined with the findings from eight other field studies of OP conducted in China, were compiled in order to compare the OP data in developed countries. The average, normalized OP levels for volume and mass at the three sampling sites in Wuhan were in the range of 1.8-8.2 nmol min^-1 m^-3 and 18.2-52.8 nmol min^-1 mg^-1, respectively. The differences in OP levels across sampling sites depended on the temporal and spatial differences in redox-active components of PM_2.5. Results from linear regression and PCA showed that the redox-active components emitted from secondary inorganic aerosols as well as secondary organic aerosols were associated with the volume normalized OP in Wuhan. Two notable findings are illustrated by synthesizing the OP results observed at multi-sites across China. Of the nine field studies conducted in China, the lowest measured mass-normalized OP levels are significantly higher than the highest OP levels from field studies conducted in developed continents. China shares the same sources responsible for OP (e.g., secondary sources, fuel combustion, biomass burning, and dust emissions) with several other countries in developed continents.

Optical Properties of Aerosols and Chemical Composition Apportionment under Different Pollution Levels in Wuhan during January 2018

To clarify the aerosol optical properties under different pollution levels and their impacting factors, hourly organic carbon (OC), elemental carbon (EC), and water-soluble ion (WSI) concentrations in PM2.5 were observed by using monitoring for aerosols and gases (MARGA) and a semicontinuous OC/EC analyzer (Model RT-4) in Wuhan from 9 to 26 January 2018. The aerosol extinction coefficient (bext) was reconstructed using the original Interagency Monitoring of Protected Visual Environment (IMPROVE) formula with a modification to include sea salt aerosols. A good correlation was obtained between the reconstructed bext and measured bext converted from visibility. bext presented a unimodal distribution on polluted days (PM2.5 mass concentrations > 75 μg⋅m−3), peaking at 19:00. bext on clean days (PM2.5 mass concentrations < 75 μg⋅m−3) did not change much during the day, while on polluted days, it increased rapidly starting at 12:00 due to the decrease of wind speed and increase of relative humidity (RH). PM2.5 mass concentrations, the aerosol scattering coefficient (bscat), and the aerosol extinction coefficient increased with pollution levels. The value of bext was 854.72 Mm−1 on bad days, which was 4.86, 3.1, 2.29, and 1.28 times of that obtained on excellent, good, acceptable, and poor days, respectively. When RH < 95%, bext exhibited an increasing trend with RH under all pollution levels, and the higher the pollution level, the bigger the growth rate was. However, when RH > 95%, bext on acceptable, poor and bad days decreased, while bext on excellent and good days still increased. The overall bext in Wuhan in January was mainly contributed by NH4NO3 (25.2%) and organic matter (20.1%). The contributions of NH4NO3 and (NH4)2SO4 to bext increased significantly with pollution levels. On bad days, NH4NO3 and (NH4)2SO4 contributed the most to bext, accounting for 38.2% and 27.0%, respectively.

Spatial Econometric Analysis of the Impact of Socioeconomic Factors on PM2.5 Concentration in China's Inland Cities: A Case Study from Chengdu Plain Economic Zone

Particulate matter with a diameter less than 2.5 µm (PM_2.5), one of the main sources of air pollution, has increasingly become a concern of the people and governments in China. Examining the socioeconomic factors influencing on PM_2.5 concentration is important for regional prevention and control. Previous studies mainly concentrated on the economically developed eastern coastal cities, but few studies focused on inland cities. This study selected Chengdu Plain Economic Zone (CPEZ), an inland region with heavy smog, and used spatial econometrics methods to identify the spatiotemporal distribution characteristics of PM_2.5 concentration and the socioeconomic factors underlying it from 2006 to 2016. Moran’s index indicates that PM_2.5 concentration in CPEZ does have spatial aggregation characteristics. In general, the spatial clustering from the fluctuation state to the stable low state decreased by 1% annually on average, from 0.190 (p < 0.05) in 2006 to 0.083 (p < 0.1) in 2016. According to the results of the spatial Durbin model (SDM), socioeconomic factors including population density, energy consumption per unit of output, gross domestic product (GDP), and per capita GDP have a positive effect on PM_2.5 concentration, while greening rate and per capita park space have a negative effect. Additionally, those factors have identified spatial spillover effects on PM_2.5 concentration. This study could be a reference and support for the formulation of more efficient air pollution control policies in inland cities.

Variation of airborne DNA mass ratio and fungal diversity in fine particles with day-night difference during an entire winter haze evolution process of Central China

Airborne fungi are a primary component of bioaerosols and proved to impact human health and climatic change. Deoxyribonucleic acid (DNA) is the essential component of most living organisms with relatively stable physicochemical properties. Little is known about day-night and pollution-episode differences of DNA mass ratio and fungal community in fine particles (PM_2.5) during serious winter haze events in China. Here we collected twenty-nine PM_2.5 samples every day and night during an entire winter haze evolution process in a megacity of Central China, Wuhan. DNA extraction and high-throughput sequencing methods were adopted to analyze fungal community. Results showed that mass ratio of DNA in PM_2.5 (R_D/P %) changed with pollution process and showed significant negative correlations with PM_2.5 concentration (r = -0.72, P < 0.05) and temperature (r = -0.74, P < 0.05). R_D/P became lower (4.40 × 10^-4%) after haze episodes than before (7.16 × 10^-4%). R_D/P of night-samples (1.98 × 10^-4-4.97 × 10^-4%) were all lower than those for day-samples (3.05 × 10^-4-9.99 × 10^-4%) for the same period. The fungal species richness became much lower (76 operational taxonomic units (OTUs)) after haze episodes than before (198 OTUs). The species richness of night-samples (119-537 OTUs) were all higher than those of day-samples (71-198 OTUs) for the same period. The OTUs specially owned by night-samples were also more than those by day-samples. Fungal community diversity showed random variations. The fungal community composition of each sample was classified from phylum to genus level. Pathogenic fungi accounted for 8.60% of the entire fungal community. The significantly enriched fungal taxa in the night-sample group (29 taxa) were also much more than that in the day-sample group (9 taxa), which could explain the higher species richness of airborne fungi community in the night during the haze evolution episodes. These findings may serve as an important reference or inspiration to other aerosol studies focusing on human health and behavior of aerosols in the atmosphere.

Personal exposure to PM2.5-bound polycyclic aromatic hydrocarbons and lung function alteration: Results of a panel study in China

Fine particulate matter (PM_2.5) exposure has been associated with lung function decline, but impact of PM_2.5 constituents especially for polycyclic aromatic hydrocarbons (PAHs) on lung function is unclear among community population. We enrolled 224 Chinese participants who participated in two study periods (2014-2015 and 2017-2018) of the Wuhan-Zhuhai cohort as a panel, and quantified the associations of personal PM_2.5 and sixteen PM_2.5-bound PAHs with lung function levels as well as lung function change in three years by linear mixed models. Diagnostic ratios were calculated to identify potential sources of PM_2.5-bound PAHs in Wuhan and Zhuhai separately. In single-constituent models, we found that each one interquartile-range increase of naphthalene, acenaphthene, fluoranthene and pyrene were associated with 26.82, 60.99, 45.25 and 23.37 mL decline in FVC respectively; while fluoranthene and pyrene were associated with 27.43 and 15.49 mL decline in FEV₁ respectively. Similar results were observed in consitituent-PM_2.5 joint models and single-constituent residual models. Persistently long-term high levels of three HMW-PAHs (benzo[a]anthracene, dibenzo[a,h]anthracene, and benzo[ghi]perylene) were associated with 214.65, 226.13, and 265.00 mL decline in FVC decline in three years, compared with persistently low exposure level groups. The associations were different between Wuhan and Zhuhai. The results of diagnostic ratios suggested the differences in PAH emissions between two cities. Our findings provide evidence that both short- and long-term PM_2.5-bound PAH exposures might affect lung function.

Aromatic Hydrocarbons in Urban and Suburban Atmospheres in Central China: Spatiotemporal Patterns, Source Implications, and Health Risk Assessment

: Ambient aromatic hydrocarbons (AHs) are hazardous air pollutants and the main precursors of ozone (O3). In this study, the characteristics of ambient AHs were investigated at an urban site (Ziyang, ZY) and a suburban site (Jiangxia, JX) in Wuhan, Central China, in 2017. The positive matrix factorization (PMF) model was used to investigate the sources of AHs, and a health risk assessment was applied to estimate the effects of AHs on human health. The concentrations of total AHs at ZY (2048 ± 1364 pptv) were comparable (p > 0.05) to that (2023 ± 1015 pptv) at JX. Source apportionment results revealed that vehicle exhaust was the dominant source of both, total AHs, and toluene, contributing 51.9 ± 13.1% and 49.3 ± 9.5% at ZY, and 44.7 ± 12.6% and 43.2 ± 10.2% at JX, respectively. Benzene was mainly emitted from vehicle exhaust at ZY (50.2 ± 15.5%), while it was mainly released from biomass and coal burning sources at JX (50.6 ± 16.7%). The health risk assessment results indicated that AHs did not have a significant non-carcinogenic risk, while the carcinogenic risks of benzene exceeded the regulatory limits set by the USEPA for adults (1 × 10−6) at both sites. Hence, controlling the emissions of vehicular and biomass/coal burning sources will be an effective way to reduce ambient AHs and the health risk of benzene exposure in this region. These findings will enhance our knowledge of ambient AHs in Central China and be helpful for local governments to formulate air pollution control strategies.

Analysis of urinary trace element levels in general population of Wuhan in central China

Trace element distribution in the human body varies across regions and countries due to their different living environment and lifestyle. Thus, it is of great significance to investigate the reference level of trace element in a specific population. Wuhan is the largest metropolitan area in central China with highly developed heavy industries. This study aimed at determining the reference urinary distribution in general populations of Wuhan for nine trace elements (Cr, Mn, Cu, As, Se, Cd, Hg, Tl, Pb), and analyzed their associations with age, sex, and the kidney function. In total, 226 healthy adults not exposed to these trace elements were recruited, and the first-morning urine specimens were analyzed by using ICP-MS-based method. Our results showed higher urinary levels for As and Cd in Wuhan population when compared with other countries, while other element levels were almost equivalent. Sex difference existed for urinary Cu, Mn, As, Tl, and Pb. And urinary Cd, Tl, and Pb levels were associated with the glomerular filtration rate. Almost all these urinary elements showed significant inter-correlations, especially for Cu but except for Mn. This study provides systematic information regarding urinary trace element levels in residents of Wuhan in central China, and shall be of importance for future environmental and occupational biomonitoring.

Multiple exposure pathways and health risk assessment of heavy metal(loid)s for children living in fourth-tier cities in Hubei Province

In the past, most research focused on the children living near a typical contaminated area but ignored the health risks of children living in the fourth or fifth tier cities without typical contaminated sources. These cities are now facing a series of problems, such as serious environmental pollution, undeveloped health system and so on. Furthermore, the development of modern logistics for food delivery has altered lifestyles that directly impact diets and eating patterns. In this study, multiple exposure pathways and health risks of children to heavy metal(loid)s were studied based on questionnaire-based surveys and field sampling of soil, dust, fine particulates, drinking water and food. We found that Pb, Cd and Mn levels in environmental samples were very high indicating a serious pollution problem. Inhalation exposure via aerosol particles was the most important pathway and was greater than exposure by food ingestion. The hazard index for Mn via aerosol particles was >1 even at the 5th percentile and Mn levels in urine was 10 times higher than those of people living in typical contaminated areas. The total incremental lifetime cancer risk (ILCR) for all metal(loid)s was also higher than the threshold at the 95th percentile. This study highlights health risks to children living in fourth tier cities and the importance of air pollution control to protect heavy metal exposure for children.

Observation and Source Apportionment of Trace Gases, Water-Soluble Ions and Carbonaceous Aerosol During a Haze Episode in Wuhan

As the new core region of the haze pollution, the terrain effect of sub-basin and water networks over the Twin-Hu Basin (THB) in the Yangtze River Middle-Reach (YRMR) had great impacts on the variations and distributions of air pollutants. In this study, trace gases (NH3, HNO3, and HCl), water-soluble ions (WSIs), organic carbon (OC), and elemental carbon (EC) were measured in PM2.5 from 9 January to 27 January 2018, in Wuhan using monitoring for aerosols and gases (MARGA) and a semi-continuous OC/EC analyzer (Model RT-4). The characteristics of air pollutants during a haze episode were discussed, and the PM2.5 sources were quantitatively analyzed on haze and non-haze days using the principal component analysis/absolute principal component scores (PCA/APCS) model. The average PM2.5 concentration was 122.61 μg·m−3 on haze days, which was 2.20 times greater than it was on non-haze days. The concentrations of secondary water soluble ions (WSIs) including NO3−, SO42−, and NH4+ increased sharply on haze days, which accounted for 91.61% of the total WSIs and were 2.43 times larger than the values on non-haze days. The heterogeneous oxidation reactions of NO2 and SO2 during haze episodes were proven to be the major sources of sulfate and nitrate in PM2.5. On haze days, the concentrations of EC, primary organic carbon (POC), and secondary organic carbon (SOC) were 1.68, 1.69, and 1.34 times larger than those on non-haze days, the CO, HNO3, and NH3 concentrations enhanced and relatively low SO2, O3, and HNO2 levels were observed on haze days. The diurnal variations of different pollutants distinctly varied on haze days. The PM2.5 in Wuhan primarily originated from the secondary formation, combustion, dust, industry, and vehicle exhaust sources. The source contributions of the secondary formation + combustion sources to PM2.5 on haze days were 2.79 times larger than the level on non-haze days. The contribution of the vehicle exhaust + combustion source on haze days were 0.59 times the value on non-haze days. This description is supported by a summary of how pollutant concentrations and patterns vary in the THB compared to the variations in other pollution regions in China, which have been more completely described.

Assessment of 12 Metals and Metalloids in Blood of General Populations Living in Wuhan of China by ICP-MS

Assessment of trace element levels in general population from the specific area is of importance for nutritional and occupational monitoring. In the current study, baseline blood levels of 12 toxic and/or essential metals and metalloids, including arsenic (As), cadmium (Cd), lead (Pb), mercury (Hg), chromium (Cr), thallium (Tl), manganese (Mn), copper (Cu), Zinc (Zn), calcium (Ca), iron (Fe), and magnesium (Mg), in general populations (n = 477) of Wuhan in central China were investigated by using inductively coupled plasma mass spectrometry (ICP-MS). The geometric means for As, Cd, Pb, Hg, Cr, Tl, Mn, and Cu were measured as 2.25, 0.70, 17.84, 1.90, 0.36, < 0.05, 12.40, and 783.76 μg/L, respectively. The geometric means for Zn, Ca, Fe, and Mg were 5.85, 56.66, 488.98, and 39.44 mg/L, respectively. We found the men had higher blood As, Pb, Hg, Zn, Fe, and Mg levels but had lower blood Cu and Ca levels than the women (p < 0.05). Age-related difference were found for blood Cu, Zn, Ca, Mg, Pb, Mn, As, Cd, and Hg levels (p < 0.05). Moreover, many metal concentrations were found correlated, with the strongest correlations between the pairs Fe-Mg (r = 0.57), Fe-Zn (r = 0.42), As-Hg (r = 0.46), Ca-Cu (r = 0.34), Pb-Hg (r = 0.36), Pb-Cd (r = 0.31), Pb-As (r = 0.25), and Ca-Fe (r = - 0.23). Compared with reports from other countries, most of our results were consistent, except that As Pb, Hg, Mn, and Cu showed different blood levels with European, Korea, or Beijing areas. Our study would be of importance for nutritional, environmental, and/or occupational monitoring of these metals in human.

Examining the spatially varying effects of factors on PM2.5 concentrations in Chinese cities using geographically weighted regression modeling

Whilst numerous studies have explored the spatial patterns and underlying causes of PM_2.5, little attention has been paid to the spatial heterogeneity of the factors affecting PM_2.5. In this study, a geographically weighted regression (GWR) model was used to explore the strength and direction of nexus between various factors and PM_2.5 in Chinese cities. A comprehensive interpretive framework was established, composed of 18 determinants spanning the three categories of natural conditions, socioeconomic factors, and city features. Our results indicate that PM_2.5 concentration levels were spatially heterogeneous and markedly higher in cities in eastern China than in cities in the west of the country. Based on the results of GWR, significant spatial heterogeneity was identified in both the direction and strength of the determinants at the local scale. Among all of the natural variables, elevation was found to be statistically significant with its effects on PM_2.5 in 95.60% of the cities and it correlated negatively with PM_2.5 in 99.63% cities, with its effect gradually weakening from the eastern to the western parts of China. The variable of built-up areas emerged as the strongest variable amongst the socioeconomic variables studied; it maintained a positive significant relationship in cities located in the Pearl River Delta and surrounding areas, while in other cities it exhibited a negative relationship to PM_2.5. The highest coefficients were located in cities in northeast China. As the strongest variable amongst the six landscape factors, patch density maintained a positive relationship in part of cities. While in cities in the northeast regions, patch density exhibited a negative relationship with PM_2.5, revealing that increasing urban fragmentation was conducive to PM_2.5 reductions in those regions. These empirical results provide a basis for the formulation of targeted and differentiated air quality improvement measures in the task of regional PM_2.5 governances.

Spatial and seasonal characteristics of particulate matter and gaseous pollution in China: Implications for control policy

By employing the air pollution data including particular matter (PM) and gaseous pollutants (SO₂, NO₂, CO, and O₃) measured over 130 cities in China from April 2014 to March 2015, the spatial and seasonal variations of air pollution are analyzed. The 9 representative regions including Beijing, Tianjin, and Hebei (BTH), Yangze River Delta (YRD), central China (CC), Sichuan Basin (SB), northeast China (NEC), northwest China (NWC), Pearl River Delta (PRD), Yungui Plateau (YP), and Tibet, are chose to quantify the conditions of PM and gaseous pollution. According to the magnitudes of PM_2.5 from high to low, the regions are listed in sequence as BTH, CC, SB, YRD, NEC, NWC, PRD, YP, and Tibet. The spatial patters of gaseous pollutants except O₃ are generally consistent with PM's. The CO maximum is found in BTH and NWC while the O₃ maximum in YRD, PRD, and Tibet. The seasonal cycles of SO₂ and NO₂ are quite similar to that of PM, but the SO₂ is overall higher than NO₂ in winter over the northern China while the opposite is true over the southern China. The O₃ concentrations are generally low in winter, but high in spring and summer due to active photochemical reaction when temperature is high. The percentage of haze days (daily PM_2.5 exceeds NAAQS Grade II, i.e. 75  μg m^-3) to the entire year is 45, 32 and 29%, respectively over BTH, CC, and SB, three most PM pollution regions during the study period. Although the most severe haze region occurs in BTH (139 days) from annual mean, the most severe winter in SB (54 days) owing to its basin landform and high air pollutant emissions. In contrary to PM pollution, gaseous pollution in China are overall quite trivial.

Maternal exposure to fine particulate matter and the risk of fetal distress

Prenatal life exposure to fine particulate matter (aerodynamic diameter less than or equal to 2.5 µm, PM_2.5) has been linked with increased risk of adverse fetal development and birth outcomes in previous studies. However, to our knowledge, no study has investigated the association of maternal PM_2.5 with the risk of fetal distress, which is a harmful fetal status and may lead to fetal brain damage, even fetal death. Therefore, we conducted a study to determine the association between maternal PM_2.5 and fetal distress among 7835 mother-infant pairs from a birth cohort, in Wuhan, China, 2013-2015. The individual daily PM_2.5 level was assessed using land use regression model. We evaluated the association of maternal PM_2.5 level over the whole pregnancy with fetal distress by logistic regression model, and estimated the risk between PM_2.5 exposure in specific trimester and fetal distress using generalized estimating equations. We observed that per 10 µg/m³ change of maternal PM_2.5 level over the whole pregnancy was associated with 25% increased risk of fetal distress (95% confidence interval: 1.09-1.44). Further, we found PM_2.5 level in the 2nd trimester, but not in the 1st and 3rd trimesters, was associated with fetal distress. Stratified analyses indicated that the association was only significant among infants who were born in cold seasons. Our study suggested that PM_2.5 exposure during the whole pregnancy exhibited significant associations with the risk of fetal distress, and exposure in the 2nd trimester maybe the susceptible window. Further stratified analyses indicated that birth season is a possible modifier in the association.

Seasonal Characteristics of the Chemical Composition of Fine Particles in Residences of Nanjing, China

Indoor fine particulate matter (PM_2.5) and its chemical composition is important for human exposure as people spend most of their time indoors. However, few studies have investigated the multiseasonal characteristics of indoor PM_2.5 and its chemical composition in China. In this study, the chemical composition of PM_2.5 samples in residences was analyzed over four seasons in Nanjing, China. Indoor water-soluble ions exhibited similar seasonal variations (winter > autumn > summer > spring) to those from outdoors (winter > autumn > spring > summer) except in summer. Whereas, indoor metallic elements exhibited a different seasonal pattern from that of outdoors. The highest concentrations of indoor metallic elements were observed in summer when the outdoor concentrations were low. The different seasonal variations of the chemical composition between indoor and outdoor PM_2.5 indicated that people should consider both indoor and outdoor sources to reduce their exposure to air pollutants in different seasons. The carcinogenic risks for metallic elements were within the acceptable levels, while manganese (Mn) was found to have potential noncarcinogenic risk to humans. More attention should be paid to the pollution of Mn in the study area in the future. Moreover, the cumulative effect of noncarcinogenic PM_2.5-bound elements should not be ignored.

Characteristics and source apportionment of PM2.5 in Jiaxing, China

Herein we investigated the morphology, chemical characteristics, and source apportionment of fine particulate matter (PM_2.5) samples collected from five sites in Jiaxing. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that soot aggregates and coal-fired fly ash were generally the most abundant components in the samples. All the samples were analyzed gravimetrically for mass concentrations and their various compositions were determined. Our results revealed that the PM_2.5 concentrations in the samples were in the following order: winter > spring > autumn > summer. The PM_2.5 concentrations in winter and spring were higher than those in autumn and summer, except for inorganic elements. Carbonaceous species and water-soluble inorganic ions were the most abundant components in the samples, accounting for 26.17-50.44% and 34.27-49.6%, respectively. The high secondary organic carbon/organic carbon ratio indicated that secondary organic pollution in Jiaxing was severe. The average ratios of NO₃^-/SO₄^2-, ranging from 1.01 to 1.25 at the five sites, indicated that mobile pollution sources contributed more to the formation of PM_2.5 than stationary sources. The BeP/(BeP + BaP) ratio (0.52-0.71) in samples reflected the influence of transportation from outside of Jiaxing. The positive matrix factorization (PMF) model identified eight main pollution sources: secondary nitrates (26.95%), secondary sulfates (15.49%), secondary organic aerosol (SOA) (19.64%), vehicle exhaust (15.67%), coal combustion (8.6%), fugitive dust (7.7%), ships and heavy oil (5.23%), biomass burning, and other sources (0.91%). Therefore, PM_2.5 pollution in Jiaxing during the winter and spring seasons was more severe than that in the summer and autumn. Secondary aerosols were the most important source of PM_2.5 pollution; therefore, focus should be placed on controlling gaseous precursors.

Fine particle-bound polycyclic aromatic hydrocarbons (PAHs) at an urban site of Wuhan, central China: Characteristics, potential sources and cancer risks apportionment

Levels, compositions, sources, and cancer risks of fine particle (PM_2.5)-bound PAHs were investigated at an urban site of Wuhan, Central China. Totally 115 PM_2.5 samples collected during four seasons from 2014 to 2015 were analyzed for 16 USEPA priority PAHs. The annual average of PM_2.5 and total PAHs were 106 ± 41.7 μg m^-3 and 25.1 ± 19.4 ng m^-3, respectively. The seasonal levels of PM_2.5 and PAHs varied in a similar trend, with the highest concentrations in winter and the lowest in summer. PM_2.5-bound PAHs under different pollution level was discussed and the highest average PAH levels were found at a moderate (115-150 μg m^-3) air quality level. Three sources including coal combustion and biomass burning, petrogenic source, and vehicle emissions were extracted and quantified by the positive matrix factorization (PMF) model, accounting for 22.7 ± 21.3%, 34.4 ± 29.0% and 42.9 ± 31.3% of the total PAHs, respectively. The potential source contribution function (PSCF) and the concentration-weighted trajectory (CWT) were combined to explore the geographic origins of PAHs. The spatial distributions of coal combustion and biomass burning, petrogenic source, and vehicle emissions were well correlated with medium molecular weight (MMW), low molecular weight (LMW) and high molecular weight (HMW) PAHs, respectively. Results of PSCF and CWT indicated that the long-distance transport form north of Wuhan as far as northern and eastern of China was higher than that from the southern China while the contribution of local areas was higher than those from the long-range transport. The overall lifetime lung cancer risk (LLCR) via inhalation exposure to PM_2.5-bound PAHs was estimated as 3.03 × 10^-4, with vehicle emissions contributed 57.1% (1.6 × 10^-4) to the total risk on average, followed by coal combustion and biomass burning (31.0%, 9.6 × 10^-5), and petrogenic source (11.9%, 3.6 × 10^-5).

Characteristics and oxidative potential of atmospheric PM2.5 in Beijing: Source apportionment and seasonal variation

PM_2.5 (particulate matter with the aerodynamic diameter D_p < 2.5 μm) was hypothesized to generate reactive oxygen species (ROS) and induce oxidative stress associated with inflammation and cardiovascular diseases. In the current study, PM_2.5 concentrations, water-soluble ions and elements, carbonaceous components and ROS activity characterized by the dithiothreitol (DTT) assay were determined for the PM_2.5 samples collected in Beijing, China, over a whole year. Source apportionments of PM_2.5 and DTT activity were also performed. The mean ± standard deviation of PM_2.5, DTT_m (mass-normalized DTT activity) and DTT_v (volume-normalized DTT activity) were 113.8 ± 62.7 μg·m^-3, 0.13 ± 0.10 nmol·μg^-1·min^-1 and 12.26 ± 6.82 nmol·m^-3·min^-1, respectively. The seasonal averages of DTT_m and DTT_v exhibited peak values during the local summer. Organic carbon (OC), NO₃^-, SO₄^2-, NH₄⁺ and elemental carbon (EC) were the dominant components in the constituents tested. Higher concentrations of carbonaceous components occurred in autumn and winter compared with spring and summer. Based on the positive matrix factorization model (PMF), the simulation results of source apportionment for PM_2.5 in Beijing, obtained using the annual data, identified the main categories as follows: dust, coal combustion, secondary sulfate and industrial emissions, vehicle emissions and secondary nitrates. Most detected constituents exhibited significantly positive correlations with DTT_v (p < 0.01). The results corresponding to multiple linear regression (MLR) between DTT_v activity and source contribution to PM_2.5 manifested the sensitivity sequence of DTT_v activity for the resolved sources as vehicle emissions > secondary sulfate and industrial emissions > coal combustion > dust.

CAPSULE

Based on a descending sequence of relative contribution, the diagnostic sources of DTT_v activity in PM_2.5 from Beijing included primarily vehicle emissions, secondary sulfates and industrial emissions, coal combustion, and dust.

Characteristics of atmospheric PM2.5 composition during the implementation of stringent pollution control measures in shanghai for the 2016 G20 summit

To reduce air pollution within a 300 km radius from Hangzhou (the capital city of Zhejiang Province in East China) for the 2016 G20 summit (9/4-9/5), the 14-day (8/24-9/6) stringent pollution control measures were implemented in Shanghai. Changes in atmospheric concentrations during the same 14-day period from 2014 to 2016 were examined at two Supersites, i.e., urban Pudong site (PD) and Dianshan Lake regional site (DSL). Up to 50% reductions were found for PM_2.5, with 13.1% and 9.7% reductions for SO₂ and NO₂, respectively. No apparent improvements were found for 8-h average O₃ concentrations. Large reductions were also found for SO₄^2- (51.4%), NO₃^- (68.8%), and NH₄⁺ (84.4%), on average. Elevated coefficient of divergence values (0.52-0.56) suggested that pollutant sources differed at the two sites. Biomass burning, resuspended dust, combustion, iron and steel industry, sea salt, secondary aerosol, and vehicle exhaust were identified at the DSL site by Positive Matrix Factorization (PMF). Secondary aerosol and vehicle exhaust accounted for 45.7% of PM_2.5 mass, followed 11.2%-13.7% each by industry, resuspended dust, and coal and oil combustion.

PM2.5-Bound Toxic Elements in an Urban City in East China: Concentrations, Sources, and Health Risks

Concentrations of PM_2.5-bound trace elements have increased in China, with increasing anthropogenic emissions. In this study, long-term measurements of PM_2.5-bound trace elements were conducted from January 2014 to January 2015 in the urban city of Jinan, east China. A positive matrix factorization model (PMF) and health risk assessment were used to evaluate the sources and health risks of these elements, respectively. Compared with most Chinese megacities, there were higher levels of arsenic, manganese, lead, chromium, and zinc in this city. Coal combustion, the smelting industry, vehicle emission, and soil dust were identified as the primary sources of all the measured elements. Heating activities during the heating period led to a factor of 1.3–2.8 higher concentrations for PM_2.5 and all measured elements than those during the non-heating period. Cumulative non-carcinogenic and carcinogenic risks of the toxic elements exceeded the safety levels by 8–15 and 10–18 times, respectively. Arsenic was the critical element having the greatest health risk. Coal combustion caused the highest risk among the four sources. This work provides scientific data for making targeted policies to control air pollutants and protect human health.

Chemical Composition and Deposition Fluxes of Water-Soluble Inorganic Ions on Dry and Wet Deposition Samples in Wuhan, China

Measurement of PM_2.5 concentration, dry and wet deposition of water-soluble inorganic ions (WSII) and their deposition flux was carried out. During sampling, a total number of 31 samples of PM_2.5, five wet deposition samples and seven dry deposition samples were collected. The analyses results showed that the average concentration of PM_2.5 was 122.95 µg/m³ whilst that of WSII was 51.63 µg/m³, equivalent to 42% of the total mass of PM_2.5. The correlation coefficients between WSII in samples of PM_2.5 was significant (r = 0.50 and p-value of 0.0019). Ions of &nbsp; SO 4 2 - , NO 3 - , Cl - , and &nbsp; NH 4 + were dominant in the entire samples (PM_2.5, dry and wet depositions), nevertheless, the average concentration of both SO 4 2 - and Cl - were below the China environmental quality standard for surface water. The ratio of dominant anions in wet deposition ( SO 4 2 - / NO 3 - ) was 1.59, whilst that for dry deposition ( SO 4 2 - / Cl - ) was 1.4, indicating that acidity was mainly derived from sulphate. In the case of dominant cations, the dry and wet deposition ratios ( Ca 2 + / NH 4 + ) were 1.36 and 1.37, respectively, suggesting the alkaline substances were mainly dominated by calcium salts. Days with higher recorded concentrations of PM_2.5 were accompanied by dry and warm boundary layer structure, weak low-level wind and strong inversion layer.

Characteristics and sources of trace elements in PM2.5 in two megacities in Sichuan Basin of southwest China

To characterize major trace elements in PM_2.5 and associated sources in two megacities, Chengdu (CD) and Chongqing (CQ), in Sichuan Basin of southwest China, daily PM_2.5 samples were collected at one urban site in each city from October 2014 to July 2015 and were analyzed for their contents of thirteen trace elements including four crustal elements (Al, Ca, Fe, and Ti), eight trace metals (K, Cr, Zn, Cu, Mn, Pb, Ni, and V), and As. Multiple approaches including correlation analysis, enrichment factor, principal component analysis, and conditional probability function (CPF) were applied to identify potential sources of these elements. Most of the measured trace elements in Sichuan Basin were found to have lower concentrations than in the other regions of China. K and Fe were the most abundant elements at CD with an annual mean concentrations of 720 ± 357 and 456 ± 248 ng m^-3, accounting for 34.6% and 21.9% of the total analyzed trace elements, respectively. Ca presented the highest concentration among all of the elements at CQ with annual mean of 824 ± 633 ng m^-3 (29.1% of the total). Crustal elements had the highest concentrations in spring while heavy metals had distinct seasonal variations typically with the highest concentrations in winter and the lowest in summer. Ti and Al were identified to be primarily from soil while most of the analyzed heavy metals (Cr, Mn, Cu, Zn, Pb, Ni) and As were from anthropogenic sources associated with coal combustion, industrial emission from glassmaking production and iron/steel manufacturing, and non-exhaust vehicle emission.