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Size-segregated ambient particulate matter (PM) samples were collected seasonally in suburban Nanjing of east China from 2016 to 2017 and chemically speciated. In both fine (2.1 µm, PM

Gas–particle partitioning of water-soluble organic compounds plays a significant role in influencing the formation, transport, and lifetime of organic aerosols in the atmosphere, but is poorly characterized. In this work, gas- and particle-phase concentrations of isoprene oxidation products (C5-alkene triols and 2-methylterols), levoglucosan, and sugar polyols were measured simultaneously at a suburban site of the western Yangtze River Delta in east China. All target polyols were primarily distributed into the particle phase (85.9 %–99.8 %). Given the uncertainties in measurements and vapor pressure predictions, a dependence of particle-phase fractions on vapor pressures cannot be determined. To explore the impact of aerosol liquid water on gas–particle partitioning of polyol tracers, three partitioning schemes (Cases 1–3) were proposed based on equilibriums of gas vs. organic and aqueous phases in aerosols. If particulate organic matter (OM) is presumed as the only absorbing phase (Case 1), the measurement-based absorptive partitioning coefficients (Kp,OMm) of isoprene oxidation products and levoglucosan were more than 10 times greater than predicted values (Kp,OMt). The agreement between Kp,OMm and Kp,OMt was substantially improved when solubility in a separate aqueous phase was included, whenever water-soluble and water-insoluble OM partitioned into separate (Case 2) or single (Case 3) liquid phases, suggesting that the partitioning of polyol tracers into the aqueous phase in aerosols should not be ignored. The measurement-based effective Henry's law coefficients (KH,em) of polyol tracers were orders of magnitude higher than their predicted values in pure water (KH,wt). Due to the moderate correlations between log⁡(KH,em/KH,wt) and molality of sulfate ions, the gap between KH,em and KH,wt of polyol tracers could not be fully parameterized by the equation defining “salting-in” effects and might be ascribed to mechanisms of reactive uptake, aqueous phase reaction, “like-dissolves-like” principle, etc. These study results also partly reveal the discrepancy between observation and modeling of organic aerosols.

During the past decade, air quality in China has undergone considerable variation, which is mostly attributable to anthropogenic emissions and meteorological conditions. The relative effects of meteorological conditions in eastern China were quantified using the Comprehensive Air Quality Model with Extensions (CAMx) for the period 2007–2016, and the year 2012 was chosen as the reference. In combination with observations of the air quality, the relative contributions of the two factors were identified. Six regions were selected according to their geolocations and regional climatic features. The results showed that meteorological conditions alone may have caused up to 10% of the variation in the mean annual air quality index. These conditions were generally favorable in coastal regions but unfavorable in inland ones, and they usually exerted a greater influence during winter. On average, anthropogenic emissions contributed approximately 70% of the change in PM10 concentration (relative to 2012) during the studied decade, but the contribution ratio varied significantly by region and year. Most regions exhibited lower anthropogenic ratios before 2012, indicating the major effects of anthropogenic emissions on air quality after this year. Furthermore, the considerable improvement in the air quality of these regions was mainly ascribed to reduced anthropogenic emissions. This study provides clear evidence that the air pollution control efforts that have been initiated in China since 2013, such as the Air Pollution Prevention and Control Action Plan (APPCAP), have succeeded in improving the air quality. However, attention must also be directed to the effects of meteorological conditions, which may cause severe pollution episodes even during low levels of emissions; thus, air pollution forecasting and appropriate emergency measures should be implemented in the future.

The gaseous or particulate forms of divalent mercury (Hg

Elemental concentrations of ambient aerosols are commonly sampled over 12–24 h, and the low time resolution puts a great limit on current understanding about the temporal variations and source apportionment based on receptor models. In this work, hourly-resolved concentrations of eighteen elements in PM2.5 at an urban site in Nanjing, a megacity in Yangtze River Delta of east China, were obtained by using a Xact 625 ambient metals monitor from 12/12/2016 to 12/31/2017. The influence of traffic activities was clearly reflected by the spikes of crustal elements (e.g., Fe, Ca, and Si) in the morning rush hour, and the firework burning and sandstorm events during the sampling periods were tracked by sharp enrichment of Ba, K and Fe, Ca, Si, Ti in PM2.5, respectively. To evaluate the advantage of hourly-resolved elements data in identifying impacts from specific emission sources, positive matrix factorization (PMF) analysis was performed with the 1-h data set (PMF1-h) and 23-h averaged data (PMF23-h), respectively. The 4- and 6-factor PMF23-h solutions had similar factor profiles and consistent factor contributions as the corresponding PMF1-h solutions. However, due to the limit in inter-sample variability, PMF analysis with 23-h average data misclassified some major (e.g., K, Fe, Zn, Ca, and Si) and trace (e.g., Pb) elements in factor profiles, resulting in different absolute factor contributions between PMF23-h and PMF1-h solutions. These results suggested the use of high time-resolved data to obtain valid and robust source apportionment results.

Crop residue burning is an important source of air pollutants and strongly affects the regional air quality and global climate change. This study presents a detailed emission inventory of major air pollutants from crop residue burning for the year of 2014 in China by the bottom-up method. Activity data were investigated for 296 prefecture-level cities. Emission factors were determined for indoor and in-field burning separately. Regional differences were considered for the proportion of residue burned (PCRB), the ratio between indoor and in-field burning, and the ratio of straw to grain production. The emissions were estimated at prefecture-city level as the first step; then they were redistributed within a city based on 1-km resolution land-use, MODIS fire counts, and rural population. Temporal variation was determined according to farming practices in different regions and MODIS fire counts. Uncertainties were estimated using the Monte Carlo method. The total emissions from crop residue burning in China were estimated to be 0.13 (−47–92%) for BC, 0.71 (−48–92%) for OC, 1.77 (−48–91%) for PM2.5, 2.04 (−50–100%) for PM10, 0.16 (−59–133%) for SO2, 0.53 (−55–105%) for NOX, 0.12 (−47–93%) for NH3, 1.07 (−55–102%) for CH4, 1.85 (−43–74%) for NMVOC, 18.33 (−46–85%) for CO and 305.20 (−45–80%) for CO2, in unit of Tg yr−1. Our results are remarkably lower than those reported in previous studies, mainly because of the PCRB has decreased significantly in recent years. For most of the pollutants, indoor burning accounted for about 50–70% of the emissions. Rice, wheat and corn contributed more than 85% of the emissions, but their relative contributions varied a lot with region and season. High emissions were mostly located in the eastern China, central China and northeastern China, and temporally peaked in April, June and October, with different intensities in the north and the south. This study provides a useful basis for air quality modeling and the policy making of pollution control strategies.

Black carbon (BC) emissions in China have been changing significantly due to rapid evolution of fuel consumption. In this study, BC emissions from fossil fuel consumption in different sectors were estimated in 2015 based on up-to-date activity data and emission factors (EFs). While for the future scenarios in 2020 and 2030, it was estimated according to relative changes in the activity level and EFs. In 2015, total BC emissions were estimated to be 1.48 Tg, mostly from the industrial, residential, and transportation sectors. Emission fluxes were found to have remarkable spatial features, where high fluxes generally located in eastern China. About 25% of the terrestrial area of China showed an annual flux above 0.2 t km−2. Total BC emissions will be decreased to 1.33 (2020) and 1.16 Tg (2030). Most reduction will occur in the industrial and residential sectors, while the transportation sector will see an obvious increase. The dramatic reduction of BC emissions in future is a new indication to our current understanding of the emission and its effects as well, and it may provide guidance for future scientific research and policy making in the field of climate change and air quality control.

The presence of PM2.5 may affect the photodegradation of benzene in the natural atmosphere. On one hand, the photodegradation of benzene may be promoted with the increase in PM2.5 concentrations, owing to adsorption and catalysis effect of PM2.5 surface; On the other hand, PM2.5 can scatter or block ultraviolet light and lead to weakening the photochemical reactions in the atmospheric system. It is very difficult to prove which process is dominant in the real atmosphere due to the complexity of the atmosphere. Based on coupling detrended fluctuation analysis, the goal of this work is to reveal the role of PM2.5 in the photodegradation of benzene in real atmosphere over long time scales. The 9 years regular monitoring data from 2007 to 2016 in Puzi of Taiwan are analyzed. A new nonlinear parameter (PDB) is established to characterize the photodegradation degree of atmospheric benzene. Based on sliding window technique, the correlations between the temporal variation of PDB and PM2.5 are analyzed. The results show that there is a positive correlation between PDB and PM2.5 in daytime and little correlation between them in nighttime. It indicates that PM2.5 mainly plays the promoting effect on the photodegradation of atmospheric benzene. This is the first study to directly determine the role of PM2.5 in the photochemical behavior of atmospheric benzene based on long term field observation data. Moreover, the results suggest that the regional transport of PM2.5 could seriously affect the geochemistry cycle of some VOCs. This research provides a new analysis method to directly quantify the effect of PM2.5 on the photodegradation of VOCs in the real atmosphere. It is helpful for evaluating the role of PM2.5 in the complex photochemical system.

Industrial processes, coal combustion, biomass burning (BB), and vehicular transport are important sources of atmospheric fine particles (PM2.5) and contribute to ambient air concentrations of health-hazardous species, such as heavy metals, polycyclic aromatic hydrocarbons (PAH), and oxygenated-PAHs (OPAH). In China, emission controls have been implemented to improve air quality during large events, like the Youth Olympic Games (YOG) in August 2014 in Nanjing. In this work, six measurement campaigns between January 2014 and August 2015 were undertaken in Nanjing to determine the effects of emission controls and meteorological factors on PM2.5 concentration and composition. PAHs, OPAHs, hopanes, n-alkanes, heavy metals, and several other inorganic elements were measured. PM2.5 and potassium concentrations were the highest in May-June 2014 indicating the prevalence of BB plumes in Nanjing. Emission controls substantially reduced concentrations of PM2.5 (31%), total PAHs (59%), OPAHs (37%), and most heavy metals (44-89%) during the YOG compared to August 2015. In addition, regional atmospheric transport and meteorological parameters partly explained the observed differences between the campaigns. The most abundant PAHs and OPAHs were benzo [b,k] fluoranthenes, fluoranthene, pyrene, chrysene, 1,8-naphthalic anhydride, and 9,10-anthracenedione in all campaigns. Carbon preference index and the contribution of wax n-alkanes indicated mainly biogenic sources of n-alkanes in May-June 2014 and anthropogenic sources in the other campaigns. Hopane indexes pointed to vehicular transport as the major source of hopanes, but contribution of coal combustion was detected in winter 2015. The results provide evidence to the local government of the impacts of the air protection regulations. However, differences between individual components were observed, e.g., concentrations of potentially more harmful OPAHs decreased less than concentrations of PAHs. The results suggest that the proportions of hazardous components in the PM2.5 may also change considerably due to emission control measures.

Great efforts have been made to control air pollution in China, and these have markedly changed air quality. Here, a detailed analysis of changes in air pollution in Nanjingbetween 2011 and 2017 based on hourly concentration measurements of six air pollutants is presented. The concentrations of most of these pollutants have decreased since 2013. This has resulted in the annual proportion of days meeting the new Chinese air quality standards increasing by 17.5%, as well as the proportion of days of severe or strong pollution decreasing by 8.0%. However, the ozone (O3) concentration increased between 2011 and 2017, and the number of days that O3 concentrations exceeded the Chinese standard dramatically increased from 8 days in 2011 to 60 days in 2017. Clearly, O3 has replaced fine particulate matter (PM2.5) as the most frequent dominant pollutant since 2016. Our results indicate that air pollution in Nanjing has evolved from being dominated by primary pollutants to being dominated by secondary pollutants, reflecting interaction of multiple emissions and chemical processes. Current policies and strategies need to be reassessed and modified to deal with interactions between emissions from different sources under variable meteorological conditions.

The National Air Pollution Control Plan implemented by China in 2013 reduced the concentrations of air pollutants, especially PM2.5 (aerosol particles with an aerodynamic diameter equal to or less than 2.5 µm), between 2014 and 2017. This reduction in PM2.5 potentially affected the intensity of urban heat islands (UHIs), as the presence of fine particles can influence the energy balance of the earth-atmosphere system. In this study, the effect of the pollution control plan on the UHI intensity in the Yangtze River Delta, China, was investigated via observational analysis and numerical modeling. According to the observational data, the PM2.5 concentrations in the megacities of the Yangtze River Delta, viz., Shanghai, Nanjing, Hangzhou and Hefei, in 2017 were ~35 µg m–3, showing decreases of approximately 48.36%, 28.25%, 29.41% and 32.5%, respectively, compared to 2014. Furthermore, these reductions in the PM2.5 concentration correlated well with the strengthened diurnal intensity (increasing by up to 1 K) and the weakened nocturnal intensity (decreasing by up to 1 K) of the UHIs. Numerical simulations confirmed that this “seesaw effect” on the UHI intensity was due to the decrease in PM2.5 and the consequent increase in the downward surface shortwave radiation and the outgoing top-of-the-atmosphere longwave radiation. Thus, the Air Pollution Control Plan noticeably affected the UHI intensity by reducing PM2.5—a factor which should be considered in future studies on urban climate and environmental planning.

Gas-particle partitioning of water-soluble organic compounds plays a significant role in the formation and source apportionment of organic aerosols, but is poorly characterized. In this work, gas- and particle-phase concentrations of isoprene oxidation products (C5-alkene triols and 2-methylterols), levoglucosan, and sugar polyols were measured simultaneously at a suburban site of the western Yangtze River Delta in east China. All target polyols were primarily distributed into the particle phase (85.9–99.8 %), and their average particle-phase fractions were not strictly dependent on vapor pressures. Moreover, the measurement-based partitioning coefficients (Kp,OM) of isoprene oxidation products and levoglucosan were 102 to 104 times larger than their predicted Kp,OM based on the equilibrium absorptive partitioning model. These are likely attributed to the hygroscopic properties of polyol tracers and high aerosol liquid water (ALW) concentrations (~20 µg m−3) of the study location. Due to the large gaps (up to 107) between measurement-based effective Henry's law coefficients (KH,e) and predicted values in pure water (KH,w), the gas-particle partitioning of polyol tracers could not be depicted using Henry's law alone either. The regressions of log (KH,w/KH,e) versus molality of major water-soluble components in ALW indicated that sulfate ions (salting-in effect) and water-soluble organic carbon can promote the partitioning of polyol tracers into the aqueous phase. These results suggest a partitioning mechanism of enhanced aqueous-phase uptake for polyol tracers, which partly reveals the discrepancy between observation and modeling of secondary organic aerosols.

N-containing aromatic compounds (NACs) are an important group of light-absorbing molecules in the atmosphere. They are often observed in combustion emissions, but their chemical formulas and structural characteristics remain uncertain. In this study, red oakwood and charcoal fuels were burned in cookstoves using the standard water-boiling test (WBT) procedure. Submicron aerosol particles in the cookstove emissions were collected using quartz (Qf) and polytetrafluoroethylene (PTFE) filter membranes positioned in parallel. A backup quartz filter (Qb) was also installed downstream of the PTFE filter to evaluate the effect of sampling artifacts on NAC measurements. Liquid chromatography–mass spectroscopy (LC–MS) techniques identified 17 NAC chemical formulas in the cookstove emissions. The average concentrations of total NACs in Qb samples (0.37±0.31–1.79±0.77 µg m−3) were greater than 50 % of those observed in the Qf samples (0.51±0.43–3.91±2.06 µg m−3), and the Qb-to-Qf mass ratios of individual NACs had a range of 0.02–2.71, indicating that the identified NACs might have substantial fractions remaining in the gas phase. In comparison to other sources, cookstove emissions from red oak or charcoal fuels did not exhibit unique NAC structural features but had distinct NAC composition. However, before identifying NAC sources by combining their structural and compositional information, the gas-particle partitioning behaviors of NACs should be further investigated. The average contributions of total NACs to the light absorption of organic matter at λ=365 nm (1.10 %–2.57 %) in Qf and Qb samples (10.7 %–21.0 %) are up to 10 times larger than their mass contributions (Qf: 0.31 %–1.01 %; Qb: 1.08 %–3.31 %), so the identified NACs are mostly strong light absorbers. To explain more sample extract absorption, future research is needed to understand the chemical and optical properties of high-molecular-weight (e.g., molecular weight, MW>500 Da) entities in particulate matter.

The health risks of air pollutants and ambient particulate matter (PM) are widely known. PM composition and toxicity have shown substantial spatiotemporal variability. Yet, the connections between PM composition and toxicological and health effects are vaguely understood. This is a crucial gap in knowledge that needs to be addressed in order to establish air quality guidelines and limit values that consider the chemical composition of PM instead of the current assumption of equal toxicity per inhaled dose. Here, we demonstrate further evidence for varying toxicological effects of urban PM at equal mass concentrations, and estimate how PM composition and emission source characteristics influenced this variation. We exposed a co-culture model mimicking alveolar epithelial cells and macrophages with size-segregated urban ambient PM collected before, during, and after the Nanjing Youth Olympic Games 2014. We measured the release of a set of cytokines, cell cycle alterations, and genotoxicity, and assessed the spatiotemporal variations in these responses by factorial multiple regression analysis. Additionally, we investigated how a previously identified set of emission sources and chemical components affected these variations by mixed model analysis. PM-exposure induced cytokine signaling, most notably by inducing dose-dependent increases of macrophage-regulating GM-CSF and proinflammatory TNFα, IL-6, and IL-1β concentrations, modest dose-dependent increase for cytoprotective VEGF-A, but very low to no responses for anti-inflammatory IL-10 and immunoregulatory IFNγ, respectively. We observed substantial differences in proinflammatory cytokine production depending on PM sampling period, location, and time of day. The proinflammatory response correlated positively with cell cycle arrest in G1/G0 phase and loss of cellular metabolic activity. Furthermore, PM

N-containing aromatic compounds (NACs) are an important group of light-absorbing molecules in the atmosphere. They are often observed in combustion emissions, but their chemical formulas and structural characteristics remain uncertain. In this study, red oak wood and charcoal fuels were burned in cookstoves using the standard water boiling test (WBT) procedure. Submicron aerosol particles in the cookstove emissions were collected using quartz (Qf) and polytetrafluoroethylene (PTFE) filter membranes positioned in parallel. A back-up quartz filter (Qb) was also installed downstream of the PTFE filter to evaluate the effect of sampling artifact on NACs measurements. Liquid chromatography-mass spectroscopy (LC-MS) techniques identified seventeen NAC chemical formulas in the cookstove emissions. The average concentrations of total NACs in Qb samples (0.37 ± 0.31–1.78 ± 0.78 µg m−3) were greater than 50 % of those observed in the Qf samples (0.47 ± 0.40–3.54 ± 1.63 µg m−3), and the Qb to Qf mass ratios of individual NACs had a range of 0.02–2.71, indicating that the identified NACs might have substantial fractions remaining in the gas-phase. In comparison to other sources, cookstove emissions from red oak or charcoal fuels did not exhibit unique NAC structural features, but had distinct NACs composition. However, before identifying NACs sources by combining their structural and compositional information, the gas-particle partitioning behaviors of NACs should be further investigated. The average contributions of total NACs to the light absorption of organic matter at λ = 365 nm (1.10–2.58 %) in Qf samples are much lower than those in Qb samples (10.7–21.0 %). These results suggest that more research is needed to understand the chemical and optical properties of gaseous chromophores and heavier molecular weight (e.g., MW > 500 Da) entities in particulate matter.

Atmospheric black carbon (BC) in the Tibetan Plateau (TP) can largely impact regional and global climate. Still, studies on the interannual variation in atmospheric BC over the TP and associated variation in BC sources and controlling factors are rather limited. In this study, we characterize the variations in atmospheric BC over the TP surface layer through analysis of 20-year (1995–2014) simulations from a global chemical transport model, GEOS-Chem. The results show that, of all areas in the TP, surface BC concentrations are highest over the eastern and southern TP, where surface BC are susceptible respectively to BC transport from East Asia and South Asia. Combining the GEOS-Chem simulations and trajectories from the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model, we assess the contributions of different source regions to surface BC in the TP. On the 20-year average, over 90 % surface BC in the TP comes from South Asia (47 %) and East Asia (46 %). Regarding seasonal variation in foreign influences, South Asia and East Asia are dominant source regions in winter and summer, respectively, in terms of both magnitude and affected areas in the TP. In spring and autumn, the influences from the two source regions are somewhat comparable. Interannually, surface BC over the TP is largely modulated by atmospheric transport of BC from foreign regions year-round and by biomass burning in South Asia, mostly in spring. We find that the extremely strong biomass burning in South Asia in the spring of 1999 greatly enhanced surface BC concentrations in the TP (31 % relative to the climatology). We find that the strength of the Asian monsoon correlates significantly with the interannual variation in the amount of BC transported to the TP from foreign regions. In summer, strong East Asian summer monsoon and South Asian summer monsoon tend to, respectively, increase BC transport from central China and northeast South Asia to the TP. In winter, BC transport from central China is enhanced in years with strong East Asia winter monsoon or Siberian High. A strong Siberian High can also increase BC transport from northern South Asia to the TP. This study underscores the impacts of atmospheric transport and biomass burning on the interannual variation in surface BC over the TP. It reveals a close connection between the atmospheric transport of BC from foreign regions to the TP and the Asian monsoon.

In this study, hourly concentrations of PM

An aethalometer was employed in a 1-year campaign (November 2014–November 2015) in Nanjing, China, that aimed to estimate the contributions of black carbon (BC; annual average ± std = 4.0 ± 3.3 µg m–3) and non-BC absorbers, such as brown carbon, to the aerosol absorption coefficient. We applied two methods: 1) the traditional calculation from the aethalometer data, assuming an absorption Angstrom exponent (AAE) of unity for BC (“AE method”), which provided an overall average of 27.2% for the non-BC contribution, and 2) a recently developed method based on the wavelength dependence of AAE (the “WDA method”), which indicated the existence of non-BC absorbers in 25.3% of the samples on average. We utilized trajectory and source area analyses and, in agreement with the results from other studies in this region, verified biomass burning emission sources, mainly to the northwest of the measurement site.

The relationship between ozone and its main precursors exhibits complex non-linear feature in the atmospheric photochemical system. Therefore, sophisticated mathematical and nonlinear methods are very important for studying the O3 sensitivity to its precursors and improving the O3 prediction model. In this study, the coupling detrended fluctuation analysis (CDFA) method has been used to investigate the multi-temporal scaling pattern of coupling correlations between O3 and its precursors. Hourly concentrations of ozone (O3), nitrogen oxide (NOx) and non-methane hydrocarbons (NMHCs) from 1 March 2016 to 28 February 2017 of two traffic monitoring sites in Taiwan are analyzed. Coupling multifractality features are confirmed in the temporal distribution of coupling correlations between O3 and its precursors. And the sources of coupling multifractal features are investigated by the phase randomized surrogates and the shuffling procedures. Moreover, in order to confirm the ozone sensitivity to its precursors at different time scales, a novel dynamical index, namely the coupling sensitivity degree (CSD), is introduced based on CDFA method. High temporal scale resolution of the O3-NMHCs-NOx sensitivity is presented based on the concept of sliding window. And the O3-NMHCs-NOx sensitivity regime can be shown visually by the temporal evolutions of the CSD on the whole year. Furthermore, statistics of seasonal CSD values are obtained by averaging the hourly sliding values. Result shows that the CSD values for both NMHCs and NOx are greatest in summer due to the more active photochemical reaction, compared to the other seasons. Meanwhile, the photochemical system is more sensitive to NMHCs for the two sites, which is consistent with the characteristics of pollutant emissions in the urban traffic area. At last, the diurnal pattern of the CSD for NMHCs and NOx are investigated. It is found that the greatest CSD for both NMHCs and NOx series are synchronized to the maximum O3 generation. This study provides a feasible and effective dynamical index to describe O3-NOx-NMHCs sensitivity, and suggests a new approach to improve the ozone prediction models in the photochemical system.

Particulate matter (PM) exposure may contribute to depressive-like response in mice. However, few studies have evaluated the adaptive impacts of long-term PM exposure on depressive-like response associated with systemic inflammation and brain-derived neurotrophic factor (BDNF) signaling pathway. We studied the association among depressive-like behaviors, mRNA levels of pro and anti-inflammatory cytokines, and the expression of BDNF signaling pathway in mice by long-term PM exposure. C57BL/6 male mice were exposed to ambient air alongside control mice breathing air filtered through a high-efficiency air PM (HEPA) filter. Depressive-like behaviors were assessed together with proinflammatory, anti-inflammatory cytokine mRNA levels and the modulation of BDNF pathway in hippocampus and olfactory-bulb of mice exposed to PM for 4, 8, and 12 weeks. Exposure to HEPA-filtered air for 4 weeks may exert antidepressant like effects in mice. Proinflammatory cytokines were up-regulated while the expression of BDNF, its high-affinity receptor tropomyosin-related kinase B (TrkB), and the transcription factor (cyclic adenosine monophosphate)-response element-binding protein (CREB) were down-regulated in ambient air mice. However, after 8 weeks, there was no significant difference in the rate of depressive-like behaviors between the 2 groups. After 12 weeks, mice exposed to ambient air again had a higher rate of depressive-like behaviors, significant up-regulation of proinflammatory cytokines, down-regulation of interleukin-10, BDNF, TrkB, and CREB than HEPA mice. Ultrafine PM in brain tissues of mice exposed to ambient air was observed. Our results suggest continuous high-level PM exposure alters the depressive-like response in mice and induces a damage-repair-imbalance reaction.

Anthropogenic heat emission (AHE) is an important contributor to regional climate change, and may affect air quality in many ways. To gain a complete picture of global AHEs and lay a basis for modeling, in this study, global and regional AHEs from energy consumption are estimated for the past nearly five decades, and projected for the future through the year 2100. From 1965 to 2013, global AHE increased from 148 to 485 EJ/year, and the anthropogenic heat flux (AHF) over land increased from 0.03 to 0.10 W/m2. Meanwhile, AHE per capita increased from 44.6 to 68.1 GJ. Regional differences are remarkable. In 2013, AHFs in Asia Pacific (AP), the Middle East (ME), North America (NA), Europe and Eurasia (EE), South and Central America (SCA), and Africa (AF) were 0.23, 0.22, 0.09, 0.08, 0.04, and 0.02 W/m2, respectively. During the past 50 years, AHFs in ME, AP, AF, and SCA have increased by factors of 15.3, 10.8, 5.6, and 4.0. However, growth in NA and EE has been relatively slow. In the high, moderate, and low scenarios, by 2100, the terrestrial AHFs are projected to be 0.28, 0.24, and 0.19 W/m2, respectively. The largest increase would occur in Asia and ME. Although the mean AHF is small compared to the forcing of GHGs, it may exert quite distinctive effects on the climate and the environment because of the surface-based emissions and uneven geographical distribution.

Size-fractionated heavy metal concentrations were observed in airborne particulate matter (PM) samples collected from 2014 to 2015 (spanning all four seasons) from suburban (Xianlin) and industrial (Pukou) areas in Nanjing, a megacity of southeast China. Rapid prediction models of size-fractionated metals were established based on multiple linear regression (MLR), back propagation artificial neural network (BP-ANN) and support vector machine (SVM) by using meteorological factors and PM concentrations as input parameters. About 38% and 77% of PM2.5 concentrations in Xianlin and Pukou, respectively, were beyond the Chinese National Ambient Air Quality Standard limit of 75 μg/m3. Nearly all elements had higher concentrations in industrial areas, and in winter among the four seasons. Anthropogenic elements such as Pb, Zn, Cd and Cu showed larger percentages in the fine fraction (o≤2.5 μm), whereas the crustal elements including Al, Ba, Fe, Ni, Sr and Ti showed larger percentages in the coarse fraction (o > 2.5 μm). SVM showed a higher training correlation coefficient (R), and lower mean absolute error (MAE) as well as lower root mean square error (RMSE), than MLR and BP-ANN for most metals. All the three methods showed better prediction results for Ni, Al, V, Cd and As, whereas relatively poor for Cr and Fe. The daily airborne metal concentrations in 2015 were then predicted by the fully trained SVM models and the results showed the heaviest pollution of airborne heavy metals occurred in December and January, whereas the lightest pollution occurred in June and July.

Information on chemical partitioning and associated risk of airborne metals, particularly during a haze–fog episode, is limited. Fine particulate matter (PM2.5) was collected during a severe haze–fog event in winter and non-haze–fog periods in summer and fall from an urban region of a typical Chinese mega-city, Nanjing. The particulate-bound metals (Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, Pb, Sr, Ti, V, and Zn) were chemically fractionated in a four-step sequential extraction procedure and human health risk was assessed. During the haze–fog episode, PM2.5 was extremely elevated with a mean concentration of 281 μg/m3 (range: 77–431 μg/m3), whereas the mean PM2.5 concentrations in summer and fall periods were 86 μg/m3 (range: 66–111 μg/m3) and 77 μg/m3 (range: 42–131 μg/m3), respectively. All elements had significantly higher concentrations and many metals exceeded relevant limits on haze–fog days. K, Na, Sr, Zn, Mo, Ca, Cd, Mg, Mn, Cu, Ba, Cr and As all showed relatively high proportions of the soluble and exchangeable fraction and strong bio-accessible potential. High temperature and humidity may increase the bio-accessible fraction of many airborne metals. The hazard index for potential toxic metals was 0.115, which was lower than the safe limit (1). However, the combined carcinogenic risk was 1.32 × 10− 6 for children and 5.29 × 10− 6 for adults, with both values being higher than the precautionary criterion (10− 6). Results of this study provide information for the behavior and risk mitigation of airborne metals.

To analyze the characteristics of regional background carbonaceous aerosols in western Yangtze River Delta (YRD), hourly organic carbon (OC) and elemental carbon (EC) in fine particular matter (PM 2.5 ) were measured with a semi-continuous carbon analyzer at a suburban site in upwind Nanjing from June 2013 to May 2015. Relatively low OC, EC and OC/EC were observed compared to other studies conducted in Nanjing. The reasons include the limited primary emissions around the observation site, the improved emission controls in recent years, and the use of denuder to reduce positive artifact in OC measurement. Resulting from the stable atmosphere conditions and emission variations, the highest concentrations of carbonaceous aerosols were found in both winters, with average OC and EC observed at 11.8 ± 10.0 and 5.9 ± 3.4 μg/m 3 for the first one, and 8.1 ± 5 and 4.5 ± 2.4 μg/m 3 for the second one, respectively. Compared to 2013, reduced OC and EC were found in summer and autumn 2014, demonstrating the benefits of emission control polices implemented for the Nanjing Youth Olympic, while elevated OC observed in spring 2015 was attributed probably to the increased biomass burning. For the hazy event in winter 2013, the back trajectories of air masses suggested that heavy pollution were from eastern Jiangsu, northern Anhui and Jiangsu, downtown Nanjing, and Shanghai. Secondary aerosol formation played an important role indicated by the larger mass fraction of OC and increased OC/EC in PM 2.5 during the heavy pollution period. In the harvest season, biomass burning was estimated to contribute 51% and 16% of OC and EC concentrations, respectively.

Elemental concentrations of ambient aerosols are commonly sampled over 12-24 h, and the low time resolution puts a great limit on current understanding about the temporal variations and source apportionment based on receptor models. In this work, hourly-resolved concentrations of eighteen elements in PM

Particulate matter with aerodynamic diameters no greater than 2.5 μm (PM2.5) affects solar radiation through direct and indirect means, and the effects vary with different compositions. The heterogeneous distributions of the concentration and compositions of PM2.5 between the urban centre and the suburban areas lead to changes in the urban heat island (UHI) intensity. This study investigated the direct and indirect effects of PM2.5 and the impact of scattering and absorption by PM2.5 on UHI intensity in Nanjing, China, using numerical modelling. The results showed that both the direct and indirect effects of PM2.5 reduced the UHI intensity (approximately between 0.04 K and 0.07 K) during the daytime and strengthened it during the night-time (approximately between 0.05 K and 0.08 K). Furthermore, scattering and absorbing compositions have a comparable impact on UHI where the concentration of scattering compositions is nine times the concentration of the absorbing compositions. They both decreased UHI intensity during the daytime (up to approximately 0.1 K) and increased it during the night-time (up to approximately 0.12 K). The existence of absorbing compositions of PM2.5 and their high concentrations may have worked in tandem to mask the UHI phenomenon and other problems encountered in urban development in the last few decades.

Long-term observation of atmospheric mercury (Hg) concentration and observation-based statistical methods are important tools to quantify the impacts of anthropogenic and natural perturbation on the global atmospheric Hg reservoir. In this study, two campaigns were conducted at a suburban site in eastern China with continuous measurements of gaseous elemental mercury (GEM) during the periods of August 2014 to July 2015 (Campaign 1) and May 2018 to April 2019 (Campaign 2). The overall mean GEM concentrations were 3.77 ± 1.32 and 3.24 ± 1.26 ng m−3, respectively. The potential source contribution function (PSCF) model based on backward trajectories were used to examine the variation of the potential source regions for GEM in different seasons. Generalized additive models (GAMs) were utilized in this study to quantify the impacts of local anthropogenic emissions, regional transport, and meteorological factors on the GEM concentration. Case studies with results from GAMs and observations of other air pollutants were conducted to provide more evidence for impacting mechanisms. The reduction of model residuals and the variation of contributions from direction and distance of air parcel transport imply the alleviation of local and regional anthropogenic Hg emissions from Campaign 1 to Campaign 2, respectively. The impact of relative humidity on GEM was crucial via the reduction of Hg(II) in droplets or on particles in the atmosphere. The impact of air stagnation on GEM was embodied mainly through the contribution of wind speed and partially by day of year (DOY) in winter. One DOY-controlled case also indicates the impacts of the 2015 El Nino event. With the decrease of anthropogenic emissions, the impacts of meteorological factors on GEM are getting more and more prominent. GAMs provide a promising tool for better understanding how anthropogenic and natural perturbations affect atmospheric Hg pollution.

In this study, collocated samples of particulate matter with aerodynamic diameter less than 2.5 μm (PM2.5) were collected every sixth day on quartz filters (Qf) at a suburban site in northern Nanjing, China for one year. A backup quartz filter (Qb) was installed behind Qf to estimate positive artifacts. The analysis of gravimetric mass, water-soluble inorganic ions (WSIIs), total organic (OC) and elemental carbon (EC), water-soluble OC (WSOC), total nitrogen (WSTN) and organic nitrogen (WSON) were performed on both Qf and Qb. Due to the high mass loadings on Qf (17.9 ± 7.82 mg filter−1, 4.71–38.5 mg filter−1), the collocated precision of gravimetric mass and dominant species (NH4+, NO3−, SO42−, OC, and EC) is better than that from previous work. Except K+, EC, and WSON, all other target components were detected on Qb with average Qb/Qf ratios ranging from 3.02 ± 3.48–21.7 ± 22.4%. The final concentrations and uncertainties of PM2.5 components were determined based on duplicate Qf–Qb data. The results suggest that using an error fraction of 10% will underestimate the uncertainty of less concentrated species (e.g., Ca2+ and Mg2+) in PM2.5. Due to the evaporation loss of semi-volatile materials from the Qf, the Qf–Qb calculation would lead to an estimate of the lower limit for particulate NH4+, NO3−, and OC. Synchronized hourly data of PM2.5 mass and components were obtained at downtown Nanjing. The comparisons of gravimetric versus reconstructed PM2.5 and filter-based versus continuous measurements of PM2.5 components indicate that a substantial fraction of the unexplained gravimetric PM2.5 can be attributed to aerosol water.

In this study, hourly concentrations of PM2.5 water-soluble inorganic ions, bulk organic carbon (OC), and elemental carbon (EC) were monitored from 1/1/2017 to 12/31/2017 and validated using filter-based offline analysis at an urban site in Nanjing, China. Compared with 2013 or before, the annual average of PM2.5 concentration (36.5 ± 32.9 μg m-3) in 2017 decreased by more than 40%, NO3- (12.8 ± 11.4 μg m-3) became the most abundant water-soluble ion instead of SO42- (9.29 ± 6.07 μg m-3), and the relative contribution of OC (5.92 ± 3.40 μg m-3) and EC (2.95 ± 1.53 μg m-3) to bulk PM2.5 (24.9 ± 9.31%) increased substantially, indicating the effectiveness of the control policy for reducing gaseous precursor emissions. Based on the diurnal variations of water-soluble ions and gaseous pollutants, NH4+, SO42-, and NO3- were secondarily formed and NH4NO3 dominated the composition of ammonium salts in PM2.5. The diurnal changes of OC, EC, and OC/EC ratios reflected prominent influences from local traffic patterns. Positive matrix factorization was performed using hourly data of PM2.5 components (PMF1-h), of which the results were justified by comparing to those using 23-h averaged data (PMF23-h). Given that the secondary ion formation was still the dominant source (68.2%) of PM2.5, and the average PM2.5 concentration in urban Nanjing remained higher than Tier II limit (35 μg m-3) of the Chinese National Ambient Air Quality Standard, controlling emissions of PM2.5 precursor gases should be continued after the completion of Air Pollution Prevention and Control Action Plan in 2017.

PM2.5 aerosol samples were collected during a haze–fog event in winter, as well as in spring, summer, and fall in 2013 within an urban area (Xianlin) and city center area (Gulou) of Nanjing, a megacity of SE China. The PM2.5 showed typical seasonality of waxing in winter and waning in summer or fall with annual average concentrations of 145 and 139 μg/m3 in Xianlin and Gulou, respectively. Concentrations of SO42 −, NO3−, NH4+, Cl−, and K+, EC, OC, secondary organic carbon, and most elements were elevated in winter. The sulfur oxidation ratio and concentrations of SO42 − and Cl− were significantly higher in Xianlin than Gulou (p

Haze caused by high particulate matter loadings is an important environmental issue. PM2.5 was collected in Nanjing, China, during a severe haze-fog event and clear periods. The particulate-bound elements were chemically fractionated using sequential extractions. The average PM2.5 concentration was 3.4 times higher during haze-fog (96-518 μg/m(3)) than non-haze fog periods (49-142 μg/m(3)). Nearly all elements showed significantly higher concentrations during haze-fog than non-haze fog periods. Zn, As, Pb, Cd, Mo and Cu were considered to have higher bioavailability and enrichment degree in the atmosphere. Highly bioavailable fractions of elements were associated with high temperatures. The integrated carcinogenic risk for two possible scenarios to individuals exposed to metals was higher than the accepted criterion of 10(-6), whereas noncarcinogenic risk was lower than the safe level of 1. Residents of a city burdened with haze will incur health risks caused by exposure to airborne metals.

Few studies have focused on the impact of particulate matter (PM) exposure with respect to the relationship between PM-induced inflammation and the levels of trace metals in tissues and organs. In this study, C57BL/6 male mice were exposed to ambient air alongside control mice breathing air filtered through a high-efficiency particulate air (HEPA) filter. In both groups, mRNA levels of pro- and anti-inflammatory cytokines were measured after 4, 8 and 12 weeks together with the trace metal contents of the lungs, heart, liver, hippocampus and blood. PM exposure resulted in a general upward trend in the levels of pro-inflammatory cytokines in lung, heart, liver and hippocampus. By contrast, IL-10 mRNA expression varied depending on the organ, with a continuous upward trend in heart and liver and an up-regulation at 8 weeks followed by a down-regulation at 12 weeks in lung and hippocampus. The disturbed homeostasis of inflammatory cytokines was accompanied by changes in trace metal levels in the mice. These alterations may have constituted a compensatory effect conferring protection from inflammatory damage. However, prolonged PM exposure finally resulted in the deficiency of several essential trace metals in the lungs and hippocampus, which may have contributed to the observed histological changes typical of an inflammatory response.

Ambient particulate matter (PM) is a leading global environmental health risk. Current air quality regulations are based on airborne mass concentration. However, PM from different sources have distinct chemical compositions and varied toxicity. Connections between emission control measures, air quality, PM composition, and toxicity remain insufficiently elucidated. The current study assessed the composition and toxicity of PM collected in Nanjing, China before, during, and after an air quality intervention for the 2014 Youth Olympic Games. A co-culture model that mimics the alveolar epithelium with the associated macrophages was created using A549 and THP-1 cells. These cells were exposed to size-segregated inhalable PM samples. The composition and toxicity of the PM samples were influenced by several factors including seasonal variation, emission sources, and the air quality intervention. For example, we observed a size-dependent shift in particle mass concentrations during the air quality intervention with an emphasized proportion of smaller particles (PM2.5) present in the air. The roles of industrial and fuel combustion and traffic emissions were magnified during the emission control period. Our analyses revealed that the PM samples demonstrated differential cytotoxic potencies at equal mass concentrations between sampling periods, locations, and time of day, influenced by variations in the predominant emission sources. Coal combustion and industrial emissions were the most important sources affecting the toxicological responses and displayed the least variation in emission contributions between the sampling periods. In conclusion, emission control mitigated cytotoxicity and oxidative stress for particles larger than 0.2 μm, but there was inadequate evidence to determine if it was the key factor reducing the harmful effects of PM0.2.

Energy consumption, especially the combustion of fossil fuels, is the main source of air pollutants emissions. Emissions of SO2, NOx, CO, PM10, PM2.5, BC, OC, and NH3 from fossil fuel consumption in different sectors were estimated for 2015, 2020, and 2030 based on updated and projected activity data and emission factors (EFs) in this study. The emissions in 2015 were: 22.8 Tg SO2, 19.8 Tg NOx, 140.7 Tg CO, 8.6 Tg PM10, 5.4 Tg PM2.5, 1.5 Tg BC, 2.1 Tg OC, and 0.3 Tg NH3. The industrial sector and coal consumption was the major source of pollutants except NH3, and the contribution of transportation to NOx, CO, and NH3 cannot be ignored. In the future, significant decline in industrial emissions may occur and the transportation sector may be the dominant source of emissions. It was predicted that the emissions of NOx will show an upward trend in 2030 due to increased vehicle emissions, while the range of areas with high emission fluxes will gradually narrow and the emissions will shift from point to nonpoint sources. The predicted results indicated that the emphasis of future mitigation policies should not only focus on the industrial sector and heavily polluted areas where emission fluxes will remain intensive, but also focus on the pollution control of the transportation sector to prevent NOx emissions from rising in some regions.

Crop residue burning is an important source of air pollutants and strongly affects the regional air quality and global climate change. This study presents a detailed emission inventory of major air pollutants from crop residue burning for the year of 2014 in China. Activity data were investigated for 296 prefecture-level cities, and emissions were firstly estimated for each city and then redistributed using 1-km resolution land use data. Temporal variation was determined according to the farming practice in different regions. The MODIS fire product was applied to verify the spatial and temporal variations of the inventory. Results indicates that the total emissions of BC, OC, PM2.5, PM10, SO2, NOX, NH3, CH4, NMVOC, CO and CO2 from crop residue burning (including open and household fuel burnings) were estimated to be 0.16, 0.82, 2.30, 2.66, 0.09, 0.70, 0.14, 0.81, 1.70, 13.70 and 309.04 Tg, respectively. Rice, wheat and corn were the three major contributors, but their relative contributions varied with region and season. High emissions were generally located in the eastern China, central China and northeastern China, and temporally peaking in June and October relating with harvesting time. The spatially and temporal distributions agree well with the fire pixel counts from MODIS. Uncertainties were estimated using the Monte Carlo method. This study provides a useful basis for air quality modeling and the policy making of pollution control strategies.

Ambient inhalable particulate matter (PM) is a serious health concern worldwide, but especially so in China where high PM concentrations affect huge populations. Atmospheric processes and emission sources cause spatial and temporal variations in PM concentration and chemical composition, but their influence on the toxicological characteristics of PM are still inadequately understood. In this study, we report an extensive chemical and toxicological characterization of size-segregated urban air inhalable PM collected in August and October 2013 from Nanjing, and assess the effects of atmospheric processes and likely emission sources. A549 human alveolar epithelial cells were exposed to day- and nighttime PM samples (25, 75, 150, 200, 300 μg/ml) followed by analyses of cytotoxicity, genotoxicity, cell cycle, and inflammatory response. PM10–2.5 and PM0.2 caused the greatest toxicological responses for different endpoints, illustrating that particles with differing size and chemical composition activate distinct toxicological pathways in A549 cells. PM10–2.5 displayed the greatest oxidative stress and genotoxic responses; both were higher for the August samples compared with October. In contrast, PM0.2 and PM2.5–1.0 samples displayed high cytotoxicity and substantially disrupted cell cycle; August samples were more cytotoxic whereas October samples displayed higher cell cycle disruption. Several components associated with combustion, traffic, and industrial emissions displayed strong correlations with these toxicological responses. The lower responses for PM1.0–0.2 compared to PM0.2 and PM2.5–1.0 indicate diminished toxicological effects likely due to aerosol aging and lower proportion of fresh emission particles rich in highly reactive chemical components in the PM1.0–0.2 fraction. Different emission sources and atmospheric processes caused variations in the chemical composition and toxicological responses between PM fractions, sampling campaigns, and day and night. The results indicate different toxicological pathways for coarse-mode particles compared to the smaller particle fractions with typically higher content of combustion-derived components. The variable responses inside PM fractions demonstrate that differences in chemical composition influence the induced toxicological responses. &nbsp

Urban air particulate pollution is a known cause for adverse human health effects worldwide. China has encountered air quality problems in recent years due to rapid industrialization. Toxicological effects induced by particulate air pollution vary with particle sizes and season. However, it is not known how distinctively different photochemical activity and different emission sources during the day and the night affect the chemical composition of the PM size ranges and subsequently how it is reflected to the toxicological properties of the PM exposures. The particulate matter (PM) samples were collected in four different size ranges (PM10-2.5; PM2.5-1; PM1-0.2 and PM0.2) with a high volume cascade impactor. The PM samples were extracted with methanol, dried and thereafter used in the chemical and toxicological analyses. RAW264.7 macrophages were exposed to the particulate samples in four different doses for 24 h. Cytotoxicity, inflammatory parameters, cell cycle and genotoxicity were measured after exposure of the cells to particulate samples. Particles were characterized for their chemical composition, including ions, element and PAH compounds, and transmission electron microscopy (TEM) was used to take images of the PM samples. Chemical composition and the induced toxicological responses of the size segregated PM samples showed considerable size dependent differences as well as day to night variation. The PM10-2.5 and the PM0.2 samples had the highest inflammatory potency among the size ranges. Instead, almost all the PM samples were equally cytotoxic and only minor differences were seen in genotoxicity and cell cycle effects. Overall, the PM0.2 samples had the highest toxic potential among the different size ranges in many parameters. PAH compounds in the samples and were generally more abundant during the night than the day, indicating possible photo-oxidation of the PAH compounds due to solar radiation. This was reflected to different toxicity in the PM samples. Some of the day to night difference may have been caused also by differing wind directions transporting air masses from different emission sources during the day and the night. The present findings indicate the important role of the local particle sources and atmospheric processes on the health related toxicological properties of the PM. The varying toxicological responses evoked by the PM samples showed the importance of examining various particle sizes. Especially the detected considerable toxicological activity by PM0.2 size range suggests they're attributable to combustion sources, new particle formation and atmospheric processes.

Anthropogenic heat emissions (AHEs) are a contributor to global climate change and may affect the climate and air quality in many ways. To gain a complete picture of AHEs in mainland China and to lay the groundwork for modelling of regional climate and the environment, AHEs from energy consumption and human metabolism were estimated, and an inventory was established with gridded distributions and profiles of temporal variations. This was based on the top–down inventory approach by using officially published statistical data. Results indicated that total AHE of the mainland was 1.2 × 1020 J·a−1, of which industry, transportation, buildings and human metabolism contributed 73.0, 11.6, 10.6 and 4.8%, respectively. Coal and electricity accounted for approximately 74% of the total emissions from energy consumption. The annual average heat flux of the mainland was 0.4 W·m−2, with a sharp difference between the eastern and western regions. Fluxes in the eastern regions were mostly between 0.5 and 20 W·m−2, and they were between 0 and 0.05 W·m−2 in the western regions. In urban or built-up areas of typical cities, the heat fluxes may be much higher than the average for larger areas, typically ranging from 20 to 100 W·m−2. Region-specific profiles of temporal variations will improve the inventory in the future, which can be applied to climatic and environmental models to obtain in-depth knowledge of the effects of AHEs.

A four-step sequential extraction procedure was used to study the chemical fractionation of As and heavy metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) in fine particulate matter (PM2.5) collected from Nanjing, China. The mass concentrations of most PM2.5 samples exceeded the 24 h standard (75 μg/m3) recommended by the new national ambient air quality standard of China. The most abundant elements were Fe, Zn and Pb, while As and Cd were present at the lowest concentrations. As, Cd, Cu, Mn, Pb and Zn were mostly present in the two mobile fractions, including the soluble and exchangeable fraction (F1), and carbonates, oxides and reducible fraction (F2). Fe had the highest proportion present in the residual fraction (F4). Relatively high proportions of the metals Ni and Cr were present in the oxidizable and sulfidic fraction (F3). High proportions of Zn, As and Cu and lower proportions of Cd, Cr and Fe were present in the potentially mobile phases. The enrichment factor, contamination factor and risk assessment code were calculated to analyze the main sources and assess the environmental risks of the metals in PM2.5. The carcinogenic risks of As, Cd, Ni and Pb were all lower than the accepted criterion of 10−6, whereas the carcinogenic risks of Cr for children and As and Cr for adults were higher than 10−6. The non-carcinogenic health risk of As and heavy metals because of PM2.5 exposure for children and adults were lower than but close to the safe level of 1.

The development of a reasonable statistical method of predicting the concentrations of fine-particle-bound heavy metals remains challenging. In this study, daily PM2.5 samples were collected within four different seasons from a Chinese mega-city. The annual average PM2.5 concentrations determined in industrial, city center, and suburban areas were 90, 81, and 85 μg m−3, respectively. Environmental magnetic measurements, including magnetic susceptibility, anhysteretic remanent magnetization, isothermal remanent magnetization, hysteresis loops, and thermomagnetism, indicated that the main magnetic mineral of PM2.5 is low-coercivity pseudosingle domain (PSD) magnetite. Using a support vector machine (SVM), both the volume- and mass-related concentrations of heavy metals were predicted by the PM2.5 mass concentrations and meteorological factors, with or without magnetic properties as input variables. The inclusion of magnetic variables significantly improved the prediction results for most heavy metals. Predi...

Background Ambient fine particulate matter (PM 2.5 ) pollution is currently a most severe and worrisome environmental problem in China. However, current knowledge of the health effects of this pollution is insufficient. Objectives This study aims to provide an overall understanding regarding the long-term mortality effects of current PM 2.5 pollution in China and the potential health benefits of realizing the goals stipulated in the ongoing action plan of Air Pollution Prevention and Control (APPC) and the targets suggested by the WHO. Methods Three typical causes and all-cause of PM 2.5 -related mortality were considered. The log-linear exposure-response function was adopted, and a meta-analysis was used to determine the exposure-response coefficients, based on newly available data in China and abroad. Results In the 74 leading cities of China, approximately 32% of the reported deaths, with a mortality rate of 1.9‰, were associated with PM 2.5 in 2013, in which deaths from cardiovascular, respiratory and lung-cancer causes accounted for 20% of the reported deaths, with a mortality rate of 1.2‰. The regional difference is remarkable for the mortalities and proportions of the different causes. If the PM 2.5 concentration goals of the APPC plan, the first interim and the guideline targets of the WHO could be achieved, the PM 2.5 -related all-cause mortality would be reduced by 25%, 64% and 95%, respectively, compared with that of 2013. Conclusions PM 2.5 pollution in China has incurred great health risks that are even worse than those of tobacco smoking. The health benefits of the APPC plan could be outstanding, although there is still great potential to improve future air quality.