Publications by authors named "Limin Zeng"

66 Publications

Characteristics and sources of volatile organic compounds during pollution episodes and clean periods in the Beijing-Tianjin-Hebei region.

Sci Total Environ 2021 Aug 5;799:149491. Epub 2021 Aug 5.

State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China.

Volatile organic compounds (VOCs) play an important role in air pollution. In this study, we conducted comprehensive field observations to investigate wintertime air pollution in Beijing, Wangdu, and Dezhou in the Beijing-Tianjin-Hebei region during 2017 and 2018. The average VOC concentrations of the three sites were 35.6 ± 26.6, 70.9 ± 56.3, and 50.5 ± 40.0 ppbv, respectively. The species with the highest concentration were similar in all three sites and included ethane, ethylene, acetylene, acetone, and toluene. The VOC mixing ratios of the three sites showed synchronous growth during pollution episodes and were 1.2-2 times higher than those during clean periods. Moreover, the OH loss rates (L) during pollution episodes were 1.2-1.7 times that during clean periods. The crucial reactive species in the three sites were ethylene, propylene, and acetaldehyde, contributing approximately 70% to the total L during pollution periods. According to the source apportionment analysis, vehicle exhausts were the largest source of VOCs in Beijing, accounting for more than 50% of the total emissions. During the pollution episodes, Beijing's industrial emissions decreased, but the secondary and background sources increased. Coal combustion was significant (approximately 40%) in Wangdu and should therefore be prioritized in emission reduction policies. In Dezhou, industrial emissions had a considerable impact on the VOC mixing ratio during pollution periods and should therefore be prioritized. The backward trajectory analysis showed that VOCs from the southern region likely contribute to Beijing's VOC pollution, highlighting the importance of regional integration for air quality management.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.scitotenv.2021.149491DOI Listing
August 2021

Direct evidence of local photochemical production driven ozone episode in Beijing: A case study.

Sci Total Environ 2021 Aug 5;800:148868. Epub 2021 Aug 5.

State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, China; International Joint laboratory for Regional pollution Control (IJRC), Peking University, Beijing, China; Beijing Innovation Center for Engineering Sciences and Advanced Technology, Peking University, 100871 Beijing, China. Electronic address:

We present a comprehensive field campaign conducted in Beijing, September 2016, to elucidate the photochemical smog pollution, i.e. Ozone (O). The observed daily maximum hydroxyl radical (OH) and hydroperoxy radical (HO) concentrations were up to 1 × 10 cm and 6 × 10 cm, respectively, indicating the active photochemistry in autumn Beijing. Photolysis of nitrous acid (HONO) and O contributed 1-2 ppbv h to OH primary production during daytime. OH termination were dominated by the reaction with nitric oxide (NO) and nitrogen dioxide (NO), which were in general larger than primary production rates, indicating other primary radical sources maybe important. The measurement of radicals facilitates the direct determination of local ozone production rate P (O) (O = O + NO). The integrated P(O) reached 75 ppbv in afternoon (for 4 h) when planetary boundary layer was well developed. At the same time period, the observed total oxidant concentrations O, increased significantly by 70 ppbv. In addition, the O measurement showed compact increase in 12 stations both temporally and spatially in Beijing, indicating that active photochemical production happened homogenously throughout the city. The back-trajectory analysis showed that Beijing was isolated from the other cities during the episode, which further proved that the fast ozone pollution was contributed by local photochemical production rather than regional advection.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.scitotenv.2021.148868DOI Listing
August 2021

Corrigendum to "Compositions, sources, and potential health risks of volatile organic compounds in the heavily polluted rural North China Plain during the heating season" [Sci. Total Environ. 789 (2021) 147956 10.1016/j.scitotenv.2021.147956].

Sci Total Environ 2021 Oct 30;792:149284. Epub 2021 Jul 30.

Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, Department of Environmental Science & Engineering, Fudan University, Shanghai 200438, China; IRDR International Center of Excellence on Risk Interconnectivity and Governance on Weather/Climate Extremes Impact and Public Health, Institute of Atmospheric Sciences, Fudan University, Shanghai 200438, China. Electronic address:

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.scitotenv.2021.149284DOI Listing
October 2021

Characterizing nitrate radical budget trends in Beijing during 2013-2019.

Sci Total Environ 2021 Nov 7;795:148869. Epub 2021 Jul 7.

State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China.

Nitrate (NO) radical is an important oxidant in the atmosphere as it regulates the NO budget and impacts secondary pollutant formation. Here, a long-term observational dataset of NO-related species at an urban site in Beijing was used to investigate changes in the NO budget and their atmospheric impacts during 2013-2019, in this period the Clean Air Actions Plan was carried out in China. We found that (1) changes in NO precursors (NO and O) led to a significant increase in NO formation in the surface layer in winter but a decrease in summer; (2) a reduction in NO promoted thermal equilibrium, favoring the formation of NO rather than dinitrogen pentoxide (NO). The simultaneous decrease in PM, during these years, further weakened the NO heterogeneous uptake; (3) a box model simulation revealed that both the reactions of NO with volatile organic compounds (VOC) and NO uptake were weakened in summer, implying that the policy actions implemented help to moderate secondary aerosol formation caused by NO and NO chemistry in summer; and (4) during winter, both NO + VOC and NO uptake were enhanced. Specifically, for the NO uptake, the rapid increase in NO production, or to some extent, NO oxidation capacity, far outweighed the negative shift effect, leading to a net enhancement of NO uptake in winter, which indicates that the action policy implemented led to an adverse effect on particulate nitrate formation via NO uptake in winter. This may explain the persistent winter particulate nitrate pollution in recent years. Our results highlight the systematic changes in the NO budget between 2013 and 2019 in Beijing, which subsequently affect secondary aerosol formation in different seasons.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.scitotenv.2021.148869DOI Listing
November 2021

Secondary aerosol formation from a Chinese gasoline vehicle: Impacts of fuel (E10, gasoline) and driving conditions (idling, cruising).

Sci Total Environ 2021 Nov 6;795:148809. Epub 2021 Jul 6.

State Key Joint Laboratory of Environmental Simulation and Pollution Control, International Joint Laboratory for Regional Pollution Control, Ministry of Education (IJRC), College of Environmental Sciences and Engineering, Peking University, Beijing 100871, PR China; Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, Nanjing University of Information Science & Technology, Nanjing 210044, PR China.

Chassis dynamometer experiments were conducted to investigate the effect of vehicle speed and usage of ethanol-blended gasoline (E10) on formation and evolution of gasoline vehicular secondary organic aerosol (SOA) using a Gothenburg Potential Aerosol Mass (Go: PAM) reactor. The SOA forms rapidly, and its concentration exceeds that of primary organic aerosol (POA) at an equivalent photochemical age (EPA) of ~1 day. The particle effective densities grow from 0.62 ± 0.02 g cm to 1.43 ± 0.07 g cm with increased hydroxyl radical (OH) exposure. The maximum SOA production under idling conditions (4259-7394 mg kg-fuel) is ~20 times greater than under cruising conditions. There was no statistical difference between SOA formation from pure gasoline and its formation from E10. The slopes in Van Krevelen diagram indicate that the formation pathways of bulk SOA includes the addition of both alcohol/peroxide functional groups and carboxylic acid formation from fragmentation. A closure estimation of SOA based on bottom-up and top-down methods shows that only 16%-38% of the measured SOA can be explained by the oxidation of measured volatile organic compounds (VOCs), suggesting the existence of missing precursors, e.g. unmeasured VOCs and probably semivolatile or intermediate volatile organic compounds (S/IVOCs). Our results suggest that applying parameters obtained from unified driving cycles to model SOA concentrations may lead to large discrepancies between modeled and ambient vehicular SOA. No reduction in vehicular `SOA production is realized by replacing normal gasoline with E10.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.scitotenv.2021.148809DOI Listing
November 2021

Assessing the Ratios of Formaldehyde and Glyoxal to NO as Indicators of O-NO-VOC Sensitivity.

Environ Sci Technol 2021 Jul 28. Epub 2021 Jul 28.

State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China.

Ozone (O) pollution has a negative effect on the public health and crop yields. Accurate diagnosis of O production sensitivity and targeted reduction of O precursors [i.e., nitrogen oxides (NO) or volatile organic compounds (VOCs)] are effective for mitigating O pollution. This study assesses the indicative roles of the surface formaldehyde-to-NO ratio (FNR) and glyoxal-to-NO ratio (GNR) on surface O-NO-VOC sensitivity based on a meta-analysis consisting of multiple field observations and model simulations. Thresholds of the FNR and GNR are determined using the relationship between the relative change of the O production rate and the two indicators, which are 0.55 ± 0.16 and 1.0 ± 0.3 for the FNR and 0.009 ± 0.003 and 0.024 ± 0.007 for the GNR. The sensitivity analysis indicated that the surface FNR is likely to be affected by formaldehyde primary sources under certain conditions, whereas the GNR might not be. As glyoxal measurements are becoming increasingly available, using the FNR and GNR together as O sensitivity indicators has broad potential applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.est.0c07506DOI Listing
July 2021

The particle phase state during the biomass burning events.

Sci Total Environ 2021 Oct 1;792:148035. Epub 2021 Jun 1.

State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China.

The phase state of biomass burning aerosols (BBA) remains largely unclear, impeding our understanding of their effects on air quality, climate and human health, due to its profound roles in mass transfer between gaseous and particulate phase. In this study, the phase state of BBA was investigated by measuring the particle rebound fraction ƒ combining field observations and laboratory experiments. We found that both ambient and laboratory-generated BBA had unexpectedly lower rebound fraction ƒ (<0.6) under the dry conditions (RH = 20-50%), indicating that BBA were in non-solid state at such low RH. This was obviously different from the secondary organic aerosols (SOA) derived from the oxidation of both anthropogenic and biogenic volatile organic compounds, typically with a rebound fraction ƒ larger than 0.8 at RH below 50%. Therefore, we proposed that the diffusion coefficient of gaseous molecular in the bulk of BBA might be much higher than SOA under the dry conditions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.scitotenv.2021.148035DOI Listing
October 2021

More Significant Impacts From New Particle Formation on Haze Formation During COVID-19 Lockdown.

Geophys Res Lett 2021 Apr;48(8):e2020GL091591

State Key Joint Laboratory of Environmental Simulation and Pollution Control International Joint Laboratory for Regional Pollution Control Ministry of Education (IJRC) College of Environmental Sciences and Engineering Peking University Beijing China.

During the COVID-19 lockdown in 2020, large-scale industrial and transportation emissions were reduced, but high PM concentration still occurred. This study investigated the variation of particle number size distribution during the lockdown, and analyzed the characteristics of new particle formation (NPF) events and its potential impact on haze formation. Through measurement conducted in urban Beijing during the first 3 months of 2020, and comparison with year-over-year data, the decrease of primary Aitken-mode particles was observed. However, frequencies, formation rates and growth rates of NPF events remained stable between 2020 and 2019 in the same period. As a result, >25 nm particles produced by NPF events, would play a more important role in serving as the haze formation "seeds" compared to those produced by primary emissions. This finding emphasizes the significance on the understanding of NPF mechanisms when making pollution mitigation policy in the future.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1029/2020GL091591DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8206662PMC
April 2021

Quantifying the role of PM dropping in variations of ground-level ozone: Inter-comparison between Beijing and Los Angeles.

Sci Total Environ 2021 Sep 18;788:147712. Epub 2021 May 18.

College of Environmental Sciences and Engineering, Peking University, Beijing, China.

In recent decade the ambient fine particle (PM) levels have shown a trend of distinct dropping in China, while ground-level ozone concentrations have been increasing in Beijing and many other Chinese mega-cities. The variation pattern in Los Angeles was markedly different, with PM and ozone decreasing together over past decades. In this study, we utilize observation-based methods to establish the parametric relationship between PM concentration and key aerosol physical properties (including aerosol optical depth and aerosol surface concentration), and an observation-based 1-D photochemical model to quantify the response of PM decline in enhancing ground-level ozone pollution over a large PM concentration range (10-120 μg m). We find that the significance of ozone enhancement due to PM dropping depends on both the PM levels and optical properties of particles. Ozone formation increased by 37% in 2006-2016 due to PM dropping in Beijing, while it becomes less important (7%) as PM reaches below 40 μg/m, similar to Los Angeles since 1980s. Therefore, the two cities show the convergence of air pollutant characteristics. Hence a control strategy prioritizing reactive volatile organic compound abatement is projected to yield simultaneous ozone and PM reductions in Beijing, as experienced in Los Angeles.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.scitotenv.2021.147712DOI Listing
September 2021

Compositions, sources, and potential health risks of volatile organic compounds in the heavily polluted rural North China Plain during the heating season.

Sci Total Environ 2021 Oct 23;789:147956. Epub 2021 May 23.

Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, Department of Environmental Science & Engineering, Fudan University, Shanghai 200438, China; IRDR International Center of Excellence on Risk Interconnectivity and Governance on Weather/Climate Extremes Impact and Public Health, Institute of Atmospheric Sciences, Fudan University, Shanghai 200438, China. Electronic address:

Severe volatile organic compound (VOC) pollution has become an urgent problem during the heating season in the North China Plain (NCP), as exposure to hazardous VOCs can lead to chronic or acute diseases. A campaign with online VOC measurements was conducted at a rural site in Wangdu, NCP during the 2018 heating season to characterize the compositions and associated sources of VOCs and to assess their potential health risks. The total concentration of VOCs with 94 identified species was 77.21 ± 54.39 ppb. Seven source factors were identified by non-negative matrix factorization, including coal combustion (36.1%), LPG usage (21.1%), solvent usage (13.9%), biomass burning and secondary formation (14.2%), background (7.0%), industrial emissions (4.5%), and vehicle emissions (3.3%). The point estimate approach and Monte Carlo simulation were used to estimate the carcinogenic and non-carcinogenic risks of harzadous VOCs. The results showed that the cumulative health risk of VOCs was above the safety level. Acrolein, 1.2-dichloroethane, 1,2-dichloropropane, chloroform, 1,3-butadiene, and benzene were identified as the key hazardous VOCs in Wangdu. Benzene had the highest average carcinogenic risk. Solvent usage and secondary formation were the dominant sources of adverse health effects. During the Spring Festival, most sources were sharply reduced; and VOC concentration declined by 49%. However, coal and biomass consumptions remained relatively large, probably due to heating demand. This study provides important references for the control strategies of VOCs during the heating season in heavily polluted rural areas in the NCP.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.scitotenv.2021.147956DOI Listing
October 2021

Links between the optical properties and chemical compositions of brown carbon chromophores in different environments: Contributions and formation of functionalized aromatic compounds.

Sci Total Environ 2021 Sep 4;786:147418. Epub 2021 May 4.

State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China.

Links between the optical properties and chemical compositions of brown carbon (BrC) are poorly understood because of the complexity of BrC chromophores. We conducted field studies simultaneously at both vehicle-influenced site and biomass burning-affected site in China in polluted winter. The chemical compositions and light absorption values of functionalized aromatic compounds, including phenyl aldehyde, phenyl acid, and nitroaromatic compounds, were measured. P-phthalic acid, nitrophenols and nitrocatechols were dominant BrC species, accounting for over 50% of the concentration of identified chromophores. Nitrophenols and nitrocatechols contributed more than 50% of the identified BrC absorbance between 300 and 400 nm. Oxidation of biomass burning-related products (e.g., pyrocatechol and methylcatechols) and anthropogenic volatile organic compounds (e.g., benzene and toluene) generated similar BrC chromophores, implying that these functionalized aromatic compounds play an important role in both environments. Compared with the biomass burning-affected site (22%), functionalized aromatic compounds at vehicle-influenced site accounted for a higher percentage of BrC absorption (25%). This research improves our understanding of the links between optical properties and composition of BrC, and the difference between BrC chromophores from BB-influenced area and vehicle-affected area under polluted atmospheric conditions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.scitotenv.2021.147418DOI Listing
September 2021

Secondary Production of Gaseous Nitrated Phenols in Polluted Urban Environments.

Environ Sci Technol 2021 04 1;55(8):4410-4419. Epub 2021 Apr 1.

State Key Joint Laboratory of Environmental Simulation and Pollution Control, BIC-ESAT and IJRC, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China.

Nitrated phenols (NPs) are important atmospheric pollutants that affect air quality, radiation, and health. The recent development of the time-of-flight chemical ionization mass spectrometer (ToF-CIMS) allows quantitative online measurements of NPs for a better understanding of their sources and environmental impacts. Herein, we deployed nitrate ions as reagent ions in the ToF-CIMS and quantified six classes of gaseous NPs in Beijing. The concentrations of NPs are in the range of 1 to 520 ng m. Nitrophenol (NPh) has the greatest mean concentration. Dinitrophenol (DNP) shows the greatest haze-to-clean concentration ratio, which may be associated with aqueous production. The high concentrations and distinct diurnal profiles of NPs indicate a strong secondary formation to overweigh losses, driven by high emissions of precursors, strong oxidative capacity, and high NO levels. The budget analysis on the basis of our measurements and box-model calculations suggest a minor role of the photolysis of NPs (<1 ppb h) in producing OH radicals. NPs therefore cannot explain the underestimated OH production in urban environments. Discrepancies between these results and the laboratory measurements of the NP photolysis rates indicate the need for further studies aimed at understanding the production and losses of NPs in polluted urban environments.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.est.0c07988DOI Listing
April 2021

Observations and modeling of OH and HO radicals in Chengdu, China in summer 2019.

Sci Total Environ 2021 Jun 27;772:144829. Epub 2021 Jan 27.

State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, China; International Joint laboratory for Regional pollution Control (IJRC), Peking University, Beijing, China; Beijing Innovation Center for Engineering Sciences and Advanced Technology, Peking University, Beijing, China; CAS Center for Excellence in Regional Atmospheric Environment, Chinese Academy of Science, Xiamen, China. Electronic address:

This study reports on the first continuous measurements of ambient OH and HO radicals at a suburban site in Chengdu, Southwest China, which were collected during 2019 as part of a comprehensive field campaign 'CompreHensive field experiment to explOre the photochemical Ozone formation mechaniSm in summEr - 2019 (CHOOSE-2019)'. The mean concentrations (11:00-15:00) of the observed OH and HO radicals were 9.5 × 10 and 9.0 × 10 cm, respectively. To investigate the state-of-the-art chemical mechanism of radical, closure experiments were conducted with a box model, in which the RACM2 mechanism updated with the latest isoprene chemistry (RACM2-LIM1) was used. In the base run, OH radicals were underestimated by the model for the low-NO regime, which was likely due to the missing OH recycling. However, good agreement between the observed and modeled OH concentrations was achieved when an additional species X (equivalent to 0.25 ppb of NO mixing ratio) from one new OH regeneration cycle (RO + X → HO, HO + X → OH) was added into the model. Additionally, in the base run, the model could reproduce the observed HO concentrations. Discrepancies in the observed and modeled HO concentrations were found in the sensitivity runs with HO heterogeneous uptake, indicating that the impact of the uptake may be less significant in Chengdu because of the relatively low aerosol concentrations. The ROx (= OH + HO + RO) primary source was dominated by photolysis reactions, in which HONO, O, and HCHO photolysis accounted for 34%, 19%, and 23% during the daytime, respectively. The efficiency of radical cycling was quantified by the radical chain length, which was determined by the NO to NO ratio successfully. The parameterization of the radical chain length may be very useful for the further determinations of radical recycling.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.scitotenv.2020.144829DOI Listing
June 2021

Humidity-Dependent Phase State of Gasoline Vehicle Emission-Related Aerosols.

Environ Sci Technol 2021 01 30;55(2):832-841. Epub 2020 Dec 30.

State Key Joint Laboratory of Environmental Simulation and Pollution Control, International Joint Laboratory for Regional Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China.

The phase states of primarily emitted and secondarily formed aerosols from gasoline vehicle exhausts were investigated by quantifying the particle rebound fraction (). The rebound behaviors of gasoline vehicle emission-related aerosols varied with engines, fuel types, and photochemical aging time, showing distinguished differences from biogenic secondary organic aerosols. The nonliquid-to-liquid phase transition of primary aerosols emitted from port fuel injection (PFI) and gasoline direct injection (GDI) vehicles started at a relative humidity (RH) = 50 and 60%, and liquefaction was accomplished at 60 and 70%, respectively. The RH at which declined to 0.5 decreased from 70 to 65% for the PFI case with 92# fuel, corresponding to the photochemical aging time from 0.37 to 4.62 days. For the GDI case, such RH enhanced from 60 to 65%. Our results can be used to imply the phase state of traffic-related aerosols and further understand their roles in urban atmospheric chemistry. Taking Beijing, China, as an example, traffic-related aerosols were mainly nonliquid during winter with the majority ambient RH below 50%, whereas they were mostly liquid during the morning rush hour of summer, and traffic-related secondary aerosols fluctuated between nonliquid and liquid during the daytime and tended to be liquid at night with increased ambient RH.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.est.0c05478DOI Listing
January 2021

A novel algorithm to determine the scattering coefficient of ambient organic aerosols.

Environ Pollut 2021 Feb 2;270:116209. Epub 2020 Dec 2.

State Key Joint Laboratory of Environmental Simulation and Pollution Control, International Joint Laboratory for Regional Pollution Control (IJRC), Ministry of Education, College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, PR China.

In the present work, we propose a novel algorithm to determine the scattering coefficient of OA by evaluating the relationships of the MSEs for primary organic aerosol (POA) and secondary organic aerosol (SOA) with their mass concentrations at three distinct sites, i.e. an urban site, a rural site, and a background site in China. Our results showed that the MSEs for POA and SOA increased rapidly as a function of mass concentration in low mass loading. While the increasing rate declined after a threshold of mass loading of 50 μg/m for POA, and 15 μg/m for SOA, respectively. The dry scattering coefficients of submicron particles (PM) were reconstructed based on the algorithm for POA and SOA scattering coefficient and further verified by using multi-site data. The calculated dry scattering coefficients using our reconstructing algorithm have good consistency with the measured ones, with the high correlation and small deviation in Shanghai (R = 0.98; deviations: 2.9%) and Dezhou (R = 0.90; deviations: 4.7%), indicating that our algorithms for OA and PM are applicable to predict the scattering coefficient of OA and Submicron particle (PM) in China.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.envpol.2020.116209DOI Listing
February 2021

Elucidating the effect of HONO on O pollution by a case study in southwest China.

Sci Total Environ 2021 Feb 25;756:144127. Epub 2020 Nov 25.

State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China; International Joint Laboratory for Regional Pollution Control, Ministry of Education, Beijing 100816, China; Collaborative Innovation Centre of Atmospheric Environment and Equipment Technology, Nanjing University of Information Science & Technology, Nanjing 210044, China.

Photolysis of nitrous acid (HONO) is one of the major sources for atmospheric hydroxyl radicals (OH), playing significant role in initiating tropospheric photochemical reactions for ozone (O) production. However, scarce field investigations were conducted to elucidate this effect. In this study, a field campaign was conducted at a suburban site in southwest China. The whole observation was classified into three periods based on O levels and data coverage: the serious O pollution period (Aug 13-18 as P1), the O pollution period (Aug 22-28 as P2) and the clean period (Sep 3-12 as P3), with average O peak values of 96 ppb, 82 ppb and 44 ppb, respectively. There was no significant difference of the levels of O precursors (VOCs and NOx) between P1 and P2, and thus the evident elevation of OH peak values in P1 was suspected to be the most possible explanation for the higher O peak values. Considering the larger contribution of HONO photolysis to HO primary production than photolysis of HCHO, O and ozonolysis of Alkenes, sensitivity tests of HONO reduction on O production rate in P1 are conducted by a 0-dimension model. Reduced HONO concentration effectively slows the O production in the morning, and such effect correlates with the calculated production rate of OH radicals from HONO photolysis. Higher HONO level supplying for OH radical initiation in the early morning might be the main reason for the higher O peak values in P1, which explained the correlation (R = 0.51) between average O value during daytime (10:00-19:00 LT) and average HONO value during early morning (00:00-05:00 LT). For nighttime accumulation, a suitable range of relative humidity that favored NO conversion within P1 was assumed to be the reason for the higher HONO concentration in the following early morning which promoted O peak values.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.scitotenv.2020.144127DOI Listing
February 2021

Impact of COVID-19 lockdown on ambient levels and sources of volatile organic compounds (VOCs) in Nanjing, China.

Sci Total Environ 2021 Feb 20;757:143823. Epub 2020 Nov 20.

Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, School of Environmental Science and Engineering, Nanjing University of Information Science & Technology, Nanjing 210044, China.

A lot of restrictive measures were implemented in China during January-February 2020 to control rapid spread of COVID-19. Many studies reported impact of COVID-19 lockdown on air quality, but little research focused on ambient volatile organic compounds (VOCs) till now, which play important roles in production of ozone and secondary organic aerosol. In this study, impact of COVID-19 lockdown on VOCs mixing ratios and sources were assessed based on online measurements of VOCs in Nanjing during December 20, 2019-Feburary 15, 2020 (P1-P2) and April 15-May 13, 2020 (P3). Average VOCs levels during COVID-19 lockdown period (P2) was 26.9 ppb, about half of value for pre-lockdown period (P1). Chemical composition of VOCs also showed significant changes. Aromatics contribution during decreased from 13% during P1 to 9% during P2, whereas alkanes contribution increased from 64% to 68%. Positive matrix factorization (PMF) was then applied for non-methane hydrocarbons (NMHCs) sources apportionment. Five sources were identified, including a source related to transport and background air masses, three sources related to petrochemical industry or chemical industry (petrochemical industry#1-propene/ethene, petrochemical industry#2-C7-C9 aromatics, and chemical industry-benzene), and a source attributed to gasoline evaporation and vehicular emission. During P2, NMHCs levels from petrochemical industry#2-C7-C9 aromatics showed the largest relative decline of 94%, followed by petrochemical industry#1-propene/ethene (67%), and gasoline evaporation and vehicular emission (67%). Furthermore, ratios of OH reactivity of NMHCs versus NO level (R/NO) and total oxidant production rate (P (O)) were calculated to assess potential influences of COVID-19 lockdown on O formation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.scitotenv.2020.143823DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7677035PMC
February 2021

Cross-regional transport of PM nitrate in the Pearl River Delta, China: Contributions and mechanisms.

Sci Total Environ 2021 Jan 21;753:142439. Epub 2020 Sep 21.

State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China; International Joint Laboratory for Regional Pollution Control, Ministry of Education, Beijing 100816, China; Beijing Innovation Center for Engineering Science and Advanced Technology, Peking University, Beijing 100871, China; CAS Center for Excellence in Regional Atmospheric Environment, Chinese Academy of Sciences, Xiamen 361021, China. Electronic address:

Cross-regional transport potentially contributes to PM nitrate (pNO), and this can occur as indirect transport, through which pNO precursors are transported to targeted regions, wherein they subsequently react with locally emitted ones to produce pNO. However, the process has been rarely studied, which limits its comprehensive understanding. We applied the CMAQ model to study the contributions and mechanisms of pNO transport during autumn in the Pearl River Delta (PRD), a metropolitan region under the growing influence of cross-regional transport on PM pollution. Results showed that cross-regional transport contributed to 58% pNO monthly in the PRD, and this mostly occurred as indirect transport contributions (accounting for 43% among all contributions). For the first time, we identified the mechanism of indirect pNO transport in the PRD, which mainly involves transported O and locally emitted NO reacting to produce pNO through NO heterogeneous hydrolysis. pNO contributions in different periods and regions indicated differences in the indirect transport contributions to NO heterogeneous hydrolysis under varying O availability conditions, which are determined by wind fields and the intensity of NO emissions. On the regional scale, the pNO level is controlled by both transported O and local NO emissions, but pNO sensitivity to these two precursors varies among cities. This study demonstrates the notable effect and complex process of cross-regional pNO transport in the PRD. Considering the important role of transported O for pNO, O reduction within a larger scale is required to achieve PM pollution control target.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.scitotenv.2020.142439DOI Listing
January 2021

Discovery of Phthalazinone Derivatives as Novel Hepatitis B Virus Capsid Inhibitors.

J Med Chem 2020 08 21;63(15):8134-8145. Epub 2020 Jul 21.

State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 ZuChongZhi Road, Shanghai 201203, China.

HBV capsid assembly has been viewed as an attractive target for new antiviral therapies against HBV. On the basis of a lead compound , we further investigated this target to identify novel active compounds with appropriate anti-HBV potencies and improved pharmacokinetic (PK) properties. Structure-activity relationship studies based on metabolic pathways of led to the identification of a phthalazinone derivative with appropriate anti-HBV potencies (IC = 0.014 ± 0.004 μM ), which demonstrated high oral bioavailability and liver exposure. In the AAV-HBV/mouse model, administration of resulted in a 2.67 log reduction of the HBV DNA viral load during a 4-week treatment with 150 mg/kg dosing twice daily.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.jmedchem.0c00346DOI Listing
August 2020

Field Determination of Nitrate Formation Pathway in Winter Beijing.

Environ Sci Technol 2020 08 10;54(15):9243-9253. Epub 2020 Jul 10.

State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China.

Particulate nitrate (pNO) has often been found to be the major component of fine particles in urban air-sheds in China, the United States, and Europe during winter haze episodes in recent years. However, there is a lack of knowledge regarding the experimentally determined contribution of different chemical pathways to the formation of pNO. Here, for the first time, we combine ground and tall-tower observations to quantify the chemical formation of pNO using observationally constrained model approach based on direct observations of OH and NO for the urban air-shed. We find that the gas-phase oxidation pathway (OH+NO) during the daytime is the dominant channel over the nocturnal uptake of NO during pollution episodes, with percentages of 74% in urban areas and 76% in suburban areas. This is quite different from previous studies in some regions of the US, in which the uptake of NO was concluded to account for a larger contribution in winter. These results indicate that the driving factor of nitrate pollution in Beijing and different regions of the US is different, as are the mitigation strategies for particulate nitrate.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.est.0c00972DOI Listing
August 2020

No Evidence for a Significant Impact of Heterogeneous Chemistry on Radical Concentrations in the North China Plain in Summer 2014.

Environ Sci Technol 2020 05 7;54(10):5973-5979. Epub 2020 May 7.

Institute of Energy and Climate Research, IEK-8: Troposphere, Forschungszentrum Jülich GmbH, 52428 Jülich, Germany.

The oxidation of nitric oxide to nitrogen dioxide by hydroperoxy (HO) and organic peroxy radicals (RO) is responsible for the chemical net ozone production in the troposphere and for the regeneration of hydroxyl radicals, the most important oxidant in the atmosphere. In Summer 2014, a field campaign was conducted in the North China Plain, where increasingly severe ozone pollution has been experienced in the last years. Chemical conditions in the campaign were representative for this area. Radical and trace gas concentrations were measured, allowing for calculating the turnover rates of gas-phase radical reactions. Therefore, the importance of heterogeneous HO uptake on aerosol could be experimentally determined. HO uptake could have suppressed ozone formation at that time because of the competition with gas-phase reactions that produce ozone. The successful reduction of the aerosol load in the North China Plain in the last years could have led to a significant decrease of HO loss on particles, so that ozone-forming reactions could have gained importance in the last years. However, the analysis of the measured radical budget in this campaign shows that HO aerosol uptake did not impact radical chemistry for chemical conditions in 2014. Therefore, reduced HO uptake on aerosol since then is likely not the reason for the increasing number of ozone pollution events in the North China Plain, contradicting conclusions made from model calculations reported in the literature.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.est.0c00525DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7240937PMC
May 2020

Significant impact of coal combustion on VOCs emissions in winter in a North China rural site.

Sci Total Environ 2020 Jun 2;720:137617. Epub 2020 Mar 2.

Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP3), Department of Environmental Science & Engineering, Institute of Atmospheric Sciences, Fudan University, Shanghai 200438, China; Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100191, China; Institute of Eco-Chongming, Shanghai 200062, China. Electronic address:

The measurement of volatile organic compounds (VOCs) was carried out using an online GC-FID/MS at a rural site in North China Plain from 1 Nov. 2017 to 21 Jan. 2018. Their concentrations, emission ratios and source apportionment are investigated. During the entire experiment period, the average mixing ratio of VOCs was 69.5 ± 51.9 ppb, among which alkanes contributed the most (37% on average). Eight sources were identified in the non-negative matrix factorization (NMF) model as short-chain alkanes (13.3%), biomass burning (4.6%), solvent (10.8%), industry (3.7%), coal combustion (41.1%), background (4.5%), vehicular emission (7.7%) and secondary formation (14.2%). In addition to the formation of OVOCs through photochemical reactions, the primary sources, such as coal combustion, biomass burning, vehicular emission, solvent and industry, can also contribute to OVOCs emissions. High OVOCs emission ratios thus were observed at Wangdu site. Primary emission was estimated to contribute 50%, 45%, 73%, 77%, 40%, and 29% on average to acrolein, acetone, methylvinylketone (MVK), methylethylketone (MEK), methacrolein and n-hexanal according to NMF analysis, respectively, which was well consistent with the contribution from photochemical age method. Secondary organic aerosol formation potential (SOAFP) was evaluated by SOA yield, which was significantly higher under low-NOx condition (13.4 μg m ppm) than that under high-NOx condition (3.2 μg m ppm). Moreover, the photochemical reactivity and sources of VOCs showed differences in seven observed pollution episodes. Among, the largest OH loss rate and SOAFP were found in severe pollution plumes, which were induced primarily by coal combustion. Therefore, mitigation strategies for severe pollution formation should focus on reducing coal combustion emitted VOCs that lead to SOA formation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.scitotenv.2020.137617DOI Listing
June 2020

Profiling Aerosol Liquid Water Content Using a Polarization Lidar.

Environ Sci Technol 2020 03 5;54(6):3129-3137. Epub 2020 Mar 5.

State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Science & Engineering, Peking University, Beijing, 100871, China.

Aerosol liquid water content (ALWC) plays fundamental roles in atmospheric radiation and chemical processes. However, there is little information about ALWC vertical distribution due to the lack of sufficient measurement. In this study, a novel method to retrieve ALWC using a polarization lidar is proposed. By analyzing lidar measurement combined with in situ chemical composition measurements at the surface, the particle linear depolarization ratio δ is found to be well correlated with the liquid water mass fraction. The method is built upon a valid relationship between δ and the ratio of ALWC to the particle backscatter coefficient. ALWC can be retrieved with a relative error of 30% with this method. A case study shows that the ALWC in upper levels of the boundary layer may be different from that at the ground, suggesting the importance of measuring ALWC vertical profiles during haze episodes. The study proves that polarization lidars have the potential to retrieve vertical distributions of ALWC which will benefit studies on haze formation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.est.9b07502DOI Listing
March 2020

Understanding the sources and spatiotemporal characteristics of VOCs in the Chengdu Plain, China, through measurement and emission inventory.

Sci Total Environ 2020 Apr 15;714:136692. Epub 2020 Jan 15.

College of Environmental Sciences and Engineering, State Key Joint Laboratory of Environmental Simulation and Pollution Control, Peking University, Beijing 100871, PR China. Electronic address:

In order to evaluate the volatile organic compounds (VOCs) pollution characteristics in Chengdu and to identify their sources, ambient air sample collection and measurement were conducted at 28 sampling sites covering all districts/counties of Chengdu from May 2016 to January 2017. Meanwhile, a county-level anthropogenic speciated VOCs emission inventory was established by "bottom-up" method for 2016. Then, a comparison was made between the VOCs emissions, spatial variations, and source structures derived from the measurement and emission inventory. Ambient measurements showed that the annual average mixing ratios of VOCs in Chengdu were 57.54 ppbv (12.36 to 456.04 ppbv), of which mainly dominated by alkanes (38.8%) and OVOCs (22.0%). The ambient VOCs in Chengdu have distinct spatiotemporal characteristics, with a high concentration in January at the middle-northern part of the city and a low concentration in September at the southwestern part. The spatial distribution of VOCs estimated by the emission inventory was in good agreement with ambient measurements. Comparison of individual VOCs emissions indicated that the emissions of non-methane hydrocarbon species agreed within ±100% between the two methods. Both positive matrix factorization (PMF) model results and emission inventory showed that vehicle emissions were the major contributor of anthropogenic VOCs in Chengdu (31% and 37%), followed by solvent utilization (26% and 27%) and industrial processes (23% and 30%). The large discrepancies were found between the relative contribution of combustion sources, and the PMF resolved more contributions (20%) than the emission inventory (6%). Overall, this study demonstrates that measurement results and emission inventory were in a good agreement. However, to improve the reliability of the emission inventory, we suggest significant revision on source profiles of oxygenated volatile organic compounds (OVOCs) and halocarbons, as well as more detailed investigation should be made in terms of energy consumption in household.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.scitotenv.2020.136692DOI Listing
April 2020

Remarkable nucleation and growth of ultrafine particles from vehicular exhaust.

Proc Natl Acad Sci U S A 2020 02 3;117(7):3427-3432. Epub 2020 Feb 3.

Department of Atmospheric Sciences, Texas A&M University, College Station, TX 77843;

High levels of ultrafine particles (UFPs; diameter of less than 50 nm) are frequently produced from new particle formation under urban conditions, with profound implications on human health, weather, and climate. However, the fundamental mechanisms of new particle formation remain elusive, and few experimental studies have realistically replicated the relevant atmospheric conditions. Previous experimental studies simulated oxidation of one compound or a mixture of a few compounds, and extrapolation of the laboratory results to chemically complex air was uncertain. Here, we show striking formation of UFPs in urban air from combining ambient and chamber measurements. By capturing the ambient conditions (i.e., temperature, relative humidity, sunlight, and the types and abundances of chemical species), we elucidate the roles of existing particles, photochemistry, and synergy of multipollutants in new particle formation. Aerosol nucleation in urban air is limited by existing particles but negligibly by nitrogen oxides. Photooxidation of vehicular exhaust yields abundant precursors, and organics, rather than sulfuric acid or base species, dominate formation of UFPs under urban conditions. Recognition of this source of UFPs is essential to assessing their impacts and developing mitigation policies. Our results imply that reduction of primary particles or removal of existing particles without simultaneously limiting organics from automobile emissions is ineffective and can even exacerbate this problem.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1073/pnas.1916366117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7035480PMC
February 2020

Novel Class of Colony-Stimulating Factor 1 Receptor Kinase Inhibitors Based on an -Aminopyridyl Alkynyl Scaffold as Potential Treatment for Inflammatory Disorders.

J Med Chem 2020 02 14;63(3):1397-1414. Epub 2020 Jan 14.

State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica , Chinese Academy of Sciences , No. 555 Zu-Chong-Zhi Road, Zhangjiang Hi-Tech Park , Shanghai 201203 , China.

Colony-stimulating factor 1 receptor (CSF-1R) is involved in inflammatory disorders as well as in many types of cancer. Based on high-throughput screening and docking results, we performed a detailed structure-activity-relationship study, leading to the discovery of a new series of compounds with nanomolar IC values against CSF-1R without the inhibition of fibroblast growth factor receptors. One of the most promising hits, compound , potently inhibited CSF-1R kinase with an IC value of 0.7 nM, while it showed no inhibition to the same family member FMS-like tyrosine kinase 3. Compound displayed excellent anti-inflammatory effects against RAW264.7 macrophages indicated by significant inhibition against the activation of the CSF-1R pathway with low cytotoxicity. In addition, compound exhibited strong in vivo anti-inflammatory efficacy alongside favorable drug characteristics. This novel compound may serve as a new drug candidate with promising applications in inflammatory disorders.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.jmedchem.9b01912DOI Listing
February 2020

Sensitive Detection of Ambient Formaldehyde by Incoherent Broadband Cavity Enhanced Absorption Spectroscopy.

Anal Chem 2020 02 10;92(3):2697-2705. Epub 2020 Jan 10.

State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering , Peking University , Beijing 100871 , China.

Formaldehyde (HCHO) is the most abundant atmospheric carbonyl compound and plays an important role in the troposphere. However, HCHO detection via traditional incoherent broadband cavity enhanced absorption spectroscopy (IBBCEAS) is limited by short optical path lengths and weak light intensity. Thus, a new light-emitting diode (LED)-based IBBCEAS was developed herein to measure HCHO in ambient air. Two LEDs (325 and 340 nm) coupled by a Y-type fiber bundle were used as an IBBCEAS light source, which provided both high light intensity and a wide spectral fitting range. The reflectivity of the two cavity mirrors used herein was 0.99965 (1 - reflectivity = 350 ppm loss) at 350 nm, which corresponded with an effective optical path length of 2.15 km within a 0.84 m cavity. At an integration time of 30 s, the measurement precision (1σ) for HCHO was 380 parts per trillion volume (pptv), and the corresponding uncertainty was 8.3%. The instrument was successfully deployed for the first time in a field campaign and delivered results that correlated well with those of a commercial wet-chemical instrument based on Hantzsch fluorimetry ( = 0.769). The combined light source based on a Y-type fiber bundle overcomes the difficulty of measuring ambient HCHO via IBBCEAS in near-ultraviolet range, which may extend IBBCEAS technology to measure other atmospheric trace gases with high precision.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.analchem.9b04821DOI Listing
February 2020

Enhanced aqueous-phase formation of secondary organic aerosols due to the regional biomass burning over North China Plain.

Environ Pollut 2020 Jan 12;256:113401. Epub 2019 Nov 12.

Institute of Low Temperature Science, Hokkaido University, Sapporo, 060-0891, Japan.

This study reveals the impact of biomass burning (BB) on secondary organic aerosols (SOA) formation in the North China Plain (NCP). Filter samples were analyzed for secondary inorganic aerosols (SIA), oxalic acid (C) and related aqueous-phase SOA compounds (aqSOA), stable carbon isotope composition of C (δC(C)) and aerosol liquid water content (ALWC). Based on the PM loadings, BB tracer concentrations, wildfire spots and air-mass back trajectories, we distinguished two episodes from the whole campaign, Episode I and Episode II, which were characteristic of regional and local BB, respectively. The abundances of PM and organic matter in the two events were comparable, but concentrations and fractions of SIA, aqSOA during Episode I were much higher than those during Episode II, along with heavier δC(C), suggesting an enhanced aqSOA formation in the earlier period. We found that the enhancement of aqSOA formation during Episode I was caused by an increased ALWC, which was mainly driven by SIA during the regional BB event. Our work showed that intensive burning of crop residue in East Asia can sharply enhance aqSOA production on a large scale, which may have a significant impact on the regional climate and human health.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.envpol.2019.113401DOI Listing
January 2020

Ambient volatile organic compounds in a suburban site between Beijing and Tianjin: Concentration levels, source apportionment and health risk assessment.

Sci Total Environ 2019 Dec 12;695:133889. Epub 2019 Aug 12.

Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China; University of the Chinese Academy of Sciences, Beijing 100049, China; Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China. Electronic address:

Volatile organic compounds (VOCs) have vital implications for secondary pollutants, atmospheric oxidation and human health. Ambient VOCs were investigated using an online system, gas chromatography-mass spectrometry/flame ionization detector (GC-MS/FID), at a suburban site in Xianghe in the North China Plain from 6 November 2017 to 29 January 2018. Positive matrix factorization (PMF) receptor model was applied to identify the major VOC contributing sources. Four-step health risk assessment method was used to estimate risks of all risk-posing VOC species. A total of 101 VOCs were quantified, and the mean concentration of total VOCs was 61.04 ± 65.18 ppbv. The VOCs were dominated by alkanes (38.76%), followed by alkenes, aromatics, halocarbons, OVOCs, acetylene and acetonitrile. The results of PMF revealed that vehicle exhaust, industrial emissions, liquefied petroleum gas & natural gas, solvent utilization and secondary and long-lived species contributed 31.0%, 26.4%, 18.6%, 13.6% and 10.4%, respectively, to the total VOCs. Pollutant-specific and source-specific noncarcinogenic and carcinogenic risk estimates were conducted, which showed that acrolein and vehicle exhaust had evident noncarcinogenic risks of 4.9 and 0.9, respectively. The carcinogenic risks of specific species (1,3-butadiene, acetaldehyde, benzene, chloroform and 1,2-dichloroethane) and identified sources were above the United States Environmental Protection Agency (USEPA) acceptable level (1.0 × 10) but below the tolerable risk level (1.0 × 10). Vehicle exhaust was the largest contributor (56.2%) to noncarcinogenic risk, but solvent utilization (32.6%) to carcinogenic risk. Moreover, with the evolution of pollution levels, almost all VOC species, contributions of alkenes, aromatics, solvent utilization and vehicle exhaust, and pollutant-specific and source-specific risks increased continuously and noticeably. Collectively, our findings unraveled the importance of alkenes, aromatics, solvent utilization and vehicle exhaust in the evolution of pollution levels. Future studies should consider targeting these VOC groups and sources when focusing on effective reduction strategies and assessing public health risks.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.scitotenv.2019.133889DOI Listing
December 2019

Fast Photochemistry in Wintertime Haze: Consequences for Pollution Mitigation Strategies.

Environ Sci Technol 2019 Sep 26;53(18):10676-10684. Epub 2019 Aug 26.

CAS Center for Excellence in Regional Atmospheric Environment , Chinese Academy of Science , Xiamen 361021 , China.

In contrast to summer smog, the contribution of photochemistry to the formation of winter haze in northern mid-to-high latitude is generally assumed to be minor due to reduced solar UV and water vapor concentrations. Our comprehensive observations of atmospheric radicals and relevant parameters during several haze events in winter 2016 Beijing, however, reveal surprisingly high hydroxyl radical oxidation rates up to 15 ppbv/h, which is comparable to the high values reported in summer photochemical smog and is two to three times larger than those determined in previous observations during winter in Birmingham (Heard et al. 2004, 31, (18)), Tokyo (Kanaya et al. 2007, 112, (D21)), and New York (Ren et al. 2006, 40, 252-263). The active photochemistry facilitates the production of secondary pollutants. It is mainly initiated by the photolysis of nitrous acid and ozonolysis of olefins and maintained by an extremely efficiently radical cycling process driven by nitric oxide. This boosted radical recycling generates fast photochemical ozone production rates that are again comparable to those during summer photochemical smog. The formation of ozone, however, is currently masked by its efficient chemical removal by nitrogen oxides contributing to the high level of wintertime particles. The future emission regulations, such as the reduction of nitrogen oxide emissions, therefore are facing the challenge of reducing haze and avoiding an increase in ozone pollution at the same time. Efficient control strategies to mitigate winter haze in Beijing may require measures similar as implemented to avoid photochemical smog in summer.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.est.9b02422DOI Listing
September 2019
-->