High-Performance Ir1/CeO2 Single-Atom Catalyst for the Oxidation of Toluene.

The elimination of toluene is an obligatory target with increasing VOC emission in recent years. This study successfully prepared a single-atom Ir catalyst (Ir1/CeO2) by a simple incipient wetness impregnation method, confirmed by in situ CO DRIFTS and AC-HAADF-STEM. Compared to the cluster Ir catalyst (Ir/CeO2-C), Ir1/CeO2 exhibited excellent catalytic performance, stability, and water resistance for the oxidation of toluene. By Raman, H2-TPR, O2-TPD, and XPS experiments, abundant oxygen defects and a unique Ir3+-Ov-Ce3+ structure were formed for the Ir1/CeO2 sample because it had a lower oxygen vacancy formation energy. Furthermore, the DFT results revealed that the Ir1/CeO2 sample had a lower ring-opening energy barrier and adsorption energy of the ring-opening products, which was the rate-determining step for the oxidation of toluene. This work provides instructive insights into the construction of Ir/CeO2 catalysts for the highly efficient removal of VOCs.

Elucidating the Mechanism on the Transition-Metal Ion-Synergetic-Catalyzed Oxidation of SO2 with Implications for Sulfate Formation in Beijing Haze.

Currently, atmospheric sulfate aerosols cannot be predicted reliably by numerical models because the pathways and kinetics of sulfate formation are unclear. Here, we systematically investigated the synergetic catalyzing role of transition-metal ions (TMIs, Fe3+/Mn2+) in the oxidation of SO2 by O2 on aerosols using chamber experiments. Our results showed that the synergetic effect of TMIs is critically dependent on aerosol pH due to the solubility of Fe(III) species sensitive to the aqueous phase acidity, which is effective only under pH < 3 conditions. The sulfate formation rate on aerosols is 2 orders of magnitude larger than that in bulk solution and increases significantly on smaller aerosols, suggesting that such a synergetic-catalyzed oxidation occurs on the aerosol surface. The kinetic reaction rate can be described as R = k*[H+]-2.95[Mn(II)][Fe(III)][S(IV)] (pH ≤ 3.0). We found that TMI-synergetic-catalyzed oxidation is the dominant pathway of sulfate formation in Beijing when haze particles are very acidic, while heterogeneous oxidation of SO2 by NO2 is the most important pathway when haze particles are weakly acidic. Our work for the first time clarified the role and kinetics of TMI-synergetic-catalyzed oxidation of SO2 by O2 in haze periods, which can be parameterized into models for future studies of sulfate formation.

Interannual evolution of the chemical composition, sources and processes of PM2.5 in Chengdu, China: Insights from observations in four winters.

The air quality in China has improved significantly in the last decade and, correspondingly, the characteristics of PM2.5 have also changed. We studied the interannual variation of PM2.5 in Chengdu, one of the most heavily polluted megacities in southwest China, during the most polluted season (winter). Our results show that the mass concentrations of PM2.5 decreased significantly year-by-year, from 195.8 ± 91.0 µg/m3 in winter 2016 to 96.1 ± 39.3 µg/m3 in winter 2020. The mass concentrations of organic matter (OM), SO42-, NH4+ and NO3- decreased by 49.6%, 57.1%, 49.7% and 28.7%, respectively. The differential reduction in the concentrations of chemical components increased the contributions from secondary organic carbon and NO3- and there was a larger contribution from mobile sources. The contribution of OM and NO3- not only increased with increasing levels of pollution, but also increased year-by-year at the same level of pollution. Four sources of PM2.5 were identified: combustion sources, vehicular emissions, dust and secondary aerosols. Secondary aerosols made the highest contribution and increased year-by-year, from 40.6% in winter 2016 to 46.3% in winter 2020. By contrast, the contribution from combustion sources decreased from 14.4% to 8.7%. Our results show the effectiveness of earlier pollution reduction policies and emphasizes that priority should be given to key pollutants (e.g., OM and NO3-) and sources (secondary aerosols and vehicular emissions) in future policies for the reduction of pollution in Chengdu during the winter months.

Emission and optical characteristics of brown carbon in size-segregated particles from three types of Chinese ships.

Brown carbon (BrC) is one of the important light absorption substances that have high light absorption ability under short wavelength light. However, limit studies have focused on the BrC emission from ships. In this study, size-segregated particulate matters (PM) were collected from three different types of ships, light absorption characteristics and size distribution of methanol-soluble BrC and water-soluble BrC in PM from ship exhausts were investigated. Results showed that four-stroke low-power diesel fishing boat (4-LDF) had the highest mass concentrations of methanol-soluble organic carbon (MSOC) and water-soluble organic carbon (WSOC), followed by 2-stroke high-power heavy-fuel-oil vessel (2-HHV), and four-stroke high-power marine-diesel vessel (4-HMV). While 2-HHV had obviously higher light absorption coefficients of methanol-soluble BrC (Abs365,M) and water-soluble BrC (Abs365,W) in unit weight of PM than the other two types of ships. The tested ships presented comparable or higher absorption efficiency of BrC in water extracts (MAE365,W) compared with other BrC emission sources. Majority of BrC was concentrated in fine particles, and the particle size distributions of both Abs365,M and Abs365,W showed bimodal patterns, peaking at 0.43-0.65 µm and 4.7-5.8 µm, respectively. However, different particle size distributions were found for MAE365,M between diesel and heavy fuel oil ships. Besides, different wavelength dependence in particles with different size were also detected. Ship exhaust could be confirmed as a non-ignorable BrC emission source, and complex influencing factor could affect the light absorption characteristics of ship emissions. Particle size should also be considered when light absorption ability of BrC was evaluated.

Secondary Formation of Atmospheric Brown Carbon in China Haze: Implication for an Enhancing Role of Ammonia.

Optical characteristics and molecular compositions of brown carbon (BrC) were investigated during winter 2019 at a rural site of China with a focus on nitro-aromatic compounds (NACs) and imidazoles (IMs). The abundance of gaseous nitrophenols relative to CO during the campaign maximized at noontime, being similar to O3, while the particulate NACs during the haze periods strongly correlated with toluene and NO2, suggesting that NACs in the region are largely formed from the gas-phase photooxidation. Strong correlations of particulate IMs in the dry haze periods with the mass ratio of EC/PM2.5 and the concentration of levoglucosan were observed, indicating that IMs during the dry events are largely derived from biomass burning emissions. However, an increase in IMs with the increasing aerosol liquid water content and pH was observed in the humid haze events, along with much lower abundances of levoglucosan and K+ relative to PM2.5, suggesting that IMs were mostly formed from aqueous reactions in the humid haze periods. These IMs exponentially increased with an increasing NH3 owing to an aqueous reaction of carbonyls with free ammonia. Our findings for the first time revealed an enhancing effect of ammonia on BrC formation in China, especially in humid haze periods.

Double-Edged Role of VOCs Reduction in Nitrate Formation: Insights from Observations during the China International Import Expo 2018.

Aerosol nitrate (NO3-) constitutes a significant component of fine particles in China. Prioritizing the control of volatile organic compounds (VOCs) is a crucial step toward achieving clean air, yet its impact on NO3- pollution remains inadequately understood. Here, we examined the role of VOCs in NO3- formation by combining comprehensive field measurements conducted during the China International Import Expo (CIIE) in Shanghai (from 10 October to 22 November 2018) and multiphase chemical modeling. Despite a decline in primary pollutants during the CIIE, NO3- levels increased compared to pre-CIIE and post-CIIE─NO3- concentrations decreased in the daytime (by -10 and -26%) while increasing in the nighttime (by 8 and 30%). Analysis of the observations and backward trajectory indicates that the diurnal variation in NO3- was mainly attributed to local chemistry rather than meteorological conditions. Decreasing VOCs lowered the daytime NO3- production by reducing the hydroxyl radical level, whereas the greater VOCs reduction at night than that in the daytime increased the nitrate radical level, thereby promoting the nocturnal NO3- production. These results reveal the double-edged role of VOCs in NO3- formation, underscoring the need for transferring large VOC-emitting enterprises from the daytime to the nighttime, which should be considered in formulating corresponding policies.

An unexpected catalyst dominates formation and radiative forcing of regional haze.

Although regional haze adversely affects human health and possibly counteracts global warming from increasing levels of greenhouse gases, the formation and radiative forcing of regional haze on climate remain uncertain. By combining field measurements, laboratory experiments, and model simulations, we show a remarkable role of black carbon (BC) particles in driving the formation and trend of regional haze. Our analysis of long-term measurements in China indicates declined frequency of heavy haze events along with significantly reduced SO2, but negligibly alleviated haze severity. Also, no improving trend exists for moderate haze events. Our complementary laboratory experiments demonstrate that SO2 oxidation is efficiently catalyzed on BC particles in the presence of NO2 and NH3, even at low SO2 and intermediate relative humidity levels. Inclusion of the BC reaction accounts for about 90-100% and 30-50% of the sulfate production during moderate and heavy haze events, respectively. Calculations using a radiative transfer model and accounting for the sulfate formation on BC yield an invariant radiative forcing of nearly zero W m-2 on the top of the atmosphere throughout haze development, indicating small net climatic cooling/warming but large surface cooling, atmospheric heating, and air stagnation. This BC catalytic chemistry facilitates haze development and explains the observed trends of regional haze in China. Our results imply that reduction of SO2 alone is insufficient in mitigating haze occurrence and highlight the necessity of accurate representation of the BC chemical and radiative properties in predicting the formation and assessing the impacts of regional haze.

Progress in quantitative research on the relationship between atmospheric oxidation and air quality.

Atmospheric oxidizing capacity (AOC) is an essential driving force of troposphere chemistry and self-cleaning, but the definition of AOC and its quantitative representation remain uncertain. Driven by national demand for air pollution control in recent years, Chinese scholars have carried out studies on theories of atmospheric chemistry and have made considerable progress in AOC research. This paper will give a brief review of these developments. First, AOC indexes were established that represent apparent atmospheric oxidizing ability (AOIe) and potential atmospheric oxidizing ability (AOIp) based on aspects of macrothermodynamics and microdynamics, respectively. A closed study refined the quantitative contributions of heterogeneous chemistry to AOC in Beijing, and these AOC methods were further applied in Beijing-Tianjin-Hebei and key areas across the country. In addition, the detection of ground or vertical profiles for atmospheric OH·, HO2·, NO3· radicals and reservoir molecules can now be obtained with domestic instruments in diverse environments. Moreover, laboratory smoke chamber simulations revealed heterogeneous processes involving reactions of O3 and NO2, which are typical oxidants in the surface/interface atmosphere, and the evolutionary and budgetary implications of atmospheric oxidants reacting under multispecies, multiphase and multi-interface conditions were obtained. Finally, based on the GRAPES-CUACE adjoint model improved by Chinese scholars, simulations of key substances affecting atmospheric oxidation and secondary organic and inorganic aerosol formation have been optimized. Normalized numerical simulations of AOIe and AOIp were performed, and regional coordination of AOC was adjusted. An optimized plan for controlling O3 and PM2.5 was analyzed by scenario simulation.

Ammonia in urban atmosphere can be substantially reduced by vehicle emission control: A case study in Shanghai, China.

To investigate the impact of emission controls on ammonia (NH3) pollution in urban atmosphere, observation on NH3 (1 hr interval) was performed in Shanghai before, during and after the 2019 China International Import Expo (CIIE) event, along with measurements on inorganic ions, organic tracers and stable nitrogen isotope compositions of ammonium in PM2.5. NH3 during the CIIE period was 6.5±1.0 µg/m3, which is 41% and 32% lower than that before and after the event, respectively. Such a decrease was largely ascribed to the emission controls in nonagricultural sources, of which contribution for measured NH3 in control phase abated by ∼20% compared to that during uncontrol period. Molecular compositions of PAHs and hopanes further suggested a dominant role of the reduced vehicle emissions in the urban NH3 abatement during the CIIE period. Our results revealed that vehicle exhaust emission control is an effective way to mitigate NH3 pollution and improve air quality in Chinese urban areas.

Significant coal combustion contribution to water-soluble brown carbon during winter in Xingtai, China: Optical properties and sources.

To understand the characteristics of atmospheric brown carbon (BrC), daily PM2.5 samples in Xingtai, a small city in North China Plain (NCP), during the four seasons of 2018-2019, were collected and analyzed for optical properties and chemical compositions. The light absorption at 365 nm (absλ=365 nm) displayed a strong seasonal variation with the highest value in winter (29.0±14.3 M/m), which was 3.2∼5.4-fold of that in other seasons. A strong correlation of absλ=365 nm with benzo(b)fluoranthene (BbF) was only observed in winter, indicating that coal combustion was the major source for BrC in the season due to the enhanced domestic heating. The mass absorbing efficiency of BrC also exhibited a similar seasonal pattern, and was found to correlate linearly with the aerosol pH, suggesting a positive effect of aerosol acidity on the optical properties and formation of BrC in the city. Positive matrix factorization (PMF) analysis further showed that on a yearly basis the major source for BrC was biomass burning, which accounted for 34% of the total BrC, followed by secondary formation (26.7%), coal combustion (21.3%) and fugitive dust (18%). However, the contribution from coal combustion was remarkably enhanced in winter, accounting for ∼40% of the total. Our work revealed that more efforts of "shifting coal to clean energy" are necessary in rural areas and small cities in NCP in order to further mitigate PM2.5 pollution in China.

Gas-to-Aerosol Phase Partitioning of Atmospheric Water-Soluble Organic Compounds at a Rural Site in China: An Enhancing Effect of NH3 on SOA Formation.

Partitioning gaseous water-soluble organic compounds (WSOC) to the aerosol phase is a major formation pathway of atmospheric secondary organic aerosols (SOA). However, the fundamental mechanism of the WSOC-partitioning process remains elusive. By simultaneous measurements of both gas-phase WSOC (WSOCg) and aerosol-phase WSOC (WSOCp) and formic and acetic acids at a rural site in the Yangtze River Delta (YRD) region of China during winter 2019, we showed that WSOCg during the campaign dominantly partitioned to the organic phase in the dry period (relative humidity (RH) < 80%) but to aerosol liquid water (ALW) in the humid period (RH > 80%), suggesting two distinct SOA formation processes in the region. In the dry period, temperature was the driving factor for the uptake of WSOCg. In contrast, in the humid period, the factors controlling WSOCg absorption were ALW content and pH, both of which were significantly elevated by NH3 through the formation of NH4NO3 and neutralization with organic acids. Additionally, we found that the relative abundances of WSOCp and NH4NO3 showed a strong linear correlation throughout China with a spatial distribution consistent with that of NH3, further indicating a key role of NH3 in WSOCp formation at a national scale. Since WSOCp constitutes the major part of SOA, such a promoting effect of NH3 on SOA production by elevating ALW formation and WSOCg partitioning suggests that emission control of NH3 is necessary for mitigating haze pollution, especially SOA, in China.

Evolution of aerosol chemistry in Beijing under strong influence of anthropogenic pollutants: Composition, sources, and secondary formation of fine particulate nitrated aromatic compounds.

Nitrated aromatic compounds (NACs) constitute a key segment of brown carbon (BrC), thereby contributing to the light-absorbing characteristics of aerosols in the atmosphere. However, until recently, there is a scarcity of research on their generation in the urban environment. The current study is based upon an extensive field study of NACs from fine particle samples obtained at an urban location in Beijing in the spring and summer of 2017, which was characterized by both high anthropogenic volatile organic compounds (VOCs) and high-NOx dominated conditions. The mean total concentration of the nine NACs was 8.58 ng m-3 in spring and 8.54 ng m-3 in summer. In the spring, the most abundant NACs were 4-nitrophenol (33.7%) and 4-nitrocatechol (19.3%), while in the summer, the most abundant NACs were 4-nitroguaiacol (34.9%) and 2, 4-dinitrophenol (23%). Atmospheric NACs were primarily produced from coal combustion (52%) and biomass burning (32%) in spring, and originated from the secondary formation (37%) and traffic (35%) in summer. NO2 could promote the formation of NACs with a significant effect on their compositions, especially for nitrophenols and nitrocatechols. It can also affect the formation of nitrated aerosols and their existing form. Inorganic nitrates were increased to conversion in the daytime when NO2 concentrations were higher than 30 ppb, but the corresponding oxidation products shifted to primarily organic ones at night. The transition was VOC-sensitive regimes for NAC formation, and nitration of toluene was a more important pathway during the campaign in Beijing.

In-vitro oxidative potential and inflammatory response of ambient PM2.5 in a rural region of Northwest China: Association with chemical compositions and source contribution.

Overproduction of reactive oxygen species (ROS) induced by atmospheric particles and subsequent inflammatory responses are considered as one of the most important pathological mechanisms with regard to the adverse effects of air pollution exposure. In this study, fine particulate matter (PM2.5) samples were collected at a rural site in Guanzhong Basin, Northwest China, in both summer (August 3-23, 2016) and winter (January 5-February 1, 2017). Then, human bronchial epithelial BEAS-2B cells were exposed to the PM2.5, cultured for 24 h, and then assayed for particle-induced ROS and three inflammatory factors (tumor necrosis-α (TNF-α), interleukin-6 (IL-6), and interferon-γ (IFN-γ)) in vitro. The oxidative potential (OP) induced by winter PM2.5 samples was higher than that induced by summertime samples, whereas inflammatory values showed contrasting seasonal variations. Both OP and inflammatory factors were significantly correlated with most chemical compounds in winter, but not in summer, which was thought to be related mainly to the higher contribution from secondary aerosols formed during the warm season. Source apportionment results showed secondary aerosols formation have significant contribution to OP of PM2.5 in both seasons, but the dominant oxidation processes is different. Secondary nitrates-related process was the major contributors regulating the OP in winter; however, secondary sulfates formation were mainly responsible for the ROS responses in summer. For primary emission, biomass burning, rather than coal emission or vehicle exhaust, was the significant source for OP of PM2.5 in winter. In most cases, the source contribution of each inflammatory factor was similar to that of the ROS. Our results highlighted the significant health risk of atmospheric aerosols from biomass burning in the rural regions of Guanzhong Basin, Northwest China.

Sustainable nano-pesticide platform based on Pyrethrins II for prevention and control Monochamus alternatus.

BACKGROUND: Pine wilt disease as a devastating forest disaster result from Bursaphelenchus xylophilus that spread by stem-borers Monochamus alternatus feeding on pine leaves, which has brought inestimable economic losses to the world's forestry due to lack of effective prevention and control measures. In this paper, we put forward a proposal for utilizing nanoHKUST-1 to encapusulate the Pyrethrins II that a nerve agent extracted from plant to control M. alternatus, including toxicity mechanism research, traceable biopesticide monitoring, and environment assessment for the first time. The highly biocompatible nanoHKUST-1 can solve the problems of poor water solubility, easy degradation and low control efficiency of Pyrethrins II. RESULTS: The results illustrated the biopesticide loading efficiency of PthII@HKUST-1 reached 85% and the cumulative release of pH-dependent PthII@HKUST-1 was up to 15 days (90%), and also effectively avoid photodegradation (pH 7.0, retention 60.9%). 50 nm PthII@HKUST-1 made it easily penetrate the body wall of MA larvae and transmit to tissue cells through contact and diffusion. Moreover, PthII@HKUST-1 can effectively enhance the cytotoxicity and utilization of Pyrethrins II, which will provide valuable research value for the application of typical plant-derived nerve agents in the prevention and control of forestry pests. PthII@HKUST-1 as an environmentally friendly nano-pesticide can efficiently deliver Pyrethrins II to the larval intestines and absorbed by the larvae. PthII@HKUST-1 could also be transmitted to the epidemic wood and dead wood at a low concentration (10 mg/L). CONCLUSION: Here we speculate that nanoHKUST-1 will bring new opportunity to research biopesticide inhibition mechanism of different agricultural and forestry pests, which will break through the existing research limitations on development, utilization and traceable monitoring of biopesticide, especially for the study of targeting specific proteins.

Simultaneous immobilization of arsenic, lead and cadmium by magnesium-aluminum modified biochar in mining soil.

Owing to the human activities such as smelting and mining, arsenic (As), lead (Pb) and cadmium (Cd) seriously polluted the soil of non-ferrous metal mining areas, thus efficient methods for the simultaneous immobilization of the three heavy metals are urgently needed. In the present study, Mg-Al modified biochars (MABs) were synthesized through a simple one-pot pyrolysis method to immobilize the three heavy metals. According to the BET (Brunauer-Emmett-Teller) test method, MABs had larger specific surface areas than biochar. Compared to the materials obtained at 300 °C and 700 °C, MAB with a pyrolysis temperature of 500 °C (MAB 500) had a significant immobilization effect on As, Pb and Cd in the Gansu mining area. Compared with BC, the removal efficiencies of As, Pb and Cd increased from -62%, 17% and 5% to 52%, 100% and 66%, respectively. And the toxicity characteristic leaching procedure (TCLP) test showed that the leaching concentrations of the three heavy metals in the treated soil were all lower than the standard value. X-ray photoelectron spectroscopy and kinetic experiments showed that there were various mechanisms in the immobilization process of the three heavy metals, and the large specific surface area and the multi-Mg/Al-OH of MABs play an important role in this process. More charges were provided by larger specific surface for ion exchange with heavy metals. In addition, larger specific surface area also provided more adsorption sites. More complex sites were provided by Mg/Al-OH to form Mg/Al-O-M then immobilize the heavy metals. In summary, the immobilization mechanism may involve electrostatic attraction, precipitation/co-precipitation, and surface complexation.

Effect of NOx and RH on the secondary organic aerosol formation from toluene photooxidation.

The secondary organic aerosol (SOA) formation mechanism and physicochemical properties can highly be influenced by relative humidity (RH) and NOx concentration. In this study, we performed a laboratory investigation of the SOA formation from toluene/OH photooxidation system in the presence or absence of NOx in dry and wet conditions. The chemical composition of toluene-derived SOA was measured using Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). It was found that the mass concentration of toluene decreased with increasing RH and NOx concentration. However, the change of SOA chemistry composition (f44, O/C) with increased RH was not consistent in the condition with or without NOx. The light absorption and mass absorption coefficient (MAC) of the toluene-derived SOA only increased with RH in the presence of NOx. In contrast, MAC is invariant with RH in the absence of NOx. HR-ToF-AMS results showed that, in the presence of NOx, the increased nitro-aromatic compounds and N/C ratio concurrently caused the increase of SOA light absorption and O/C in wet conditions, respectively. The relative intensity of CHON and CHOxN family to the total nitrogen-containing organic compounds (NOCs) increased with the increasing RH, and be the major components of NOCs in wet condition. This work revealed a synergy effect of NOx and RH on SOA formation from toluene photooxidation.

Metal-Containing Nanoparticles in Low-Rank Coal-Derived Fly Ash from China: Characterization and Implications toward Human Lung Toxicity.

Characterization of nanoparticles (NPs) in coal fly ashes (CFAs) is critical for better understanding the potential health-related risks resulting from coal combustion. Based on single-particle (SP)-inductively coupled plasma mass spectrometry (ICP-MS) coupled with transmission electron microscopy techniques, this study is the first to determine the concentrations and sizes of metal-containing NPs in low-rank coal-derived fly ashes. Despite only comprising a minor component of the studied CFAs by mass, NPs were the dominant fraction by particle number. Fe- and Ti-containing NPs were identified as the dominant NPs with their particle number concentration ranging from 2.5 × 107 to 2.5 × 108 particles/mg. In addition, the differences of Fe-/Ti-containing NPs in various CFAs were regulated by the coalification degree of feed coals and combustion conditions of all of the low-rank CFAs tested. In the cases where these NPs in CFAs become airborne and are inhaled, they can be taken up in pulmonary interstitial fluids. This study shows that in Gamble's solution (a lung fluid simulant), 51-87% of Fe and 63-89% of Ti (ratio of the mass of Fe-/Ti-containing NPs to the total mass of Fe/Ti) exist in the NP form and remain suspended in pulmonary fluid simulants. These NPs are bioavailable and may induce lung tissue damage.

Impacts of Chinese spring festival on household PM2.5 pollution and blood pressure of rural residents.

BACKGROUND: Household air pollution (HAP) from residential combustion considerably affects human health in rural China. Large-scale population migration and rural lifestyle changes during the Spring Festival are supposed to change the household air pollution and health risks; however, limited field study has determined its impacts on HAP and short-term health outcomes. METHODS: A field study was conducted in rural areas of Southern China before and during the Spring Festival to explore the associations between HAP and blood pressure considering different factors such as cooking fuel, heating fuel, and smoking. Stationary real-time PM2.5 monitors were used to measure PM2.5 concentrations of the kitchen, living room, and yard of 156 randomly selected households. Personal exposure to PM2.5 was calculated based on the results of stationary samplers and corresponding time local residents spent in different microenvironments, and one adult resident was recruited of each family for the blood pressure measurement. RESULTS: Both personal exposure to PM2.5 and blood pressures of local residents increased during Spring Festival compared to the days before the holiday. Based on generalized linear model coupled with dominance analysis approach, it was found that personal PM2.5 exposure was positively associated with the factors of population size and the types of cooking and heating fuels with the relative contributions of approximately 82%, and systolic blood pressure (SBP, 100-120 mmHg as normal range for adults) was positively and significantly associated with personal PM2.5 exposures with the relative contribution of 11%. CONCLUSION: The findings in this study demonstrated that Spring Festival can give rise to increase of HAP and hypertension risks, also related to tremendous solid fuel use, suggesting further policy making on promoting cleaner energy in rural areas and more attention on large population migration during national holidays.

Characteristics of Chemical Speciation in PM1 in Six Representative Regions in China.

A better knowledge of aerosol properties is of great significance for elucidating the complex mechanisms behind frequently occurring haze pollution events. In this study, we examine the temporal and spatial variations in both PM1 and its major chemical constituents using three-year field measurements that were collected in six representative regions in China between 2012 and 2014. Our results show that both PM1 and its chemical compositions varied significantly in space and time, with high PM1 loadings mainly observed in the winter. By comparing chemical constituents between clean and polluted episodes, we find that the elevated PM1 mass concentration during pollution events should be largely attributable to significant increases in organic matter (OM) and inorganic aerosols like sulfate, nitrate, and ammonium (SNA), indicative of the critical role of primary emissions and secondary aerosols in elevating PM1 pollution levels. The ratios of PM1/PM2.5 are found to be generally high in Shanghai and Guangzhou, while relatively low ratios are seen in Xi'an and Chengdu, indicating anthropogenic emissions were more likely to accumulate in forms of finer particles. With respect to the relative importance of chemical components and meteorological factors quantified via statistical modeling practices, we find that primary emissions and secondary aerosols were the two leading factors contributing to PM1 variations, though meteorological factors also played important roles in regulating the dispersion of atmospheric PM.

Spatial and Temporal Distributions and Sources of Anthropogenic NMVOCs in the Atmosphere of China: A Review.

As the key precursors of O3, anthropogenic non-methane volatile organic compounds (NMVOCs) have been studied intensively. This paper performed a meta-analysis on the spatial and temporal variations of NMVOCs, their roles in photochemical reactions, and their sources in China, based on published research. The results showed that both non-methane hydrocarbons (NMHCs) and oxygenated VOCs (OVOCs) in China have higher mixing ratios in the eastern developed cities compared to those in the central and western areas. Alkanes are the most abundant NMHCs species in all reported sites while formaldehyde is the most abundant among the OVOCs. OVOCs have the highest mixing ratios in summer and the lowest in winter, which is opposite to NMHCs. Among all NMVOCs, the top eight species account for 50%-70% of the total ozone formation potential (OFP) with different compositions and contributions in different areas. In devolved regions, OFP-NMHCs are the highest in winter while OFP-OVOCs are the highest in summer. Based on positive matrix factorization (PMF) analysis, vehicle exhaust, industrial emissions, and solvent usage in China are the main sources for NMHCs. However, the emission trend analysis showed that solvent usage and industrial emissions will exceed vehicle exhaust and become the two major sources of NMVOCs in near future. Based on the meta-analysis conducted in this work, we believe that the spatio-temporal variations and oxidation mechanisms of atmospheric OVOCs, as well as generating a higher spatial resolution of emission inventories of NMVOCs represent an area for future studies on NMVOCs in China.