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1.
Environ Sci Technol ; 2021 Jan 11.
Artigo em Inglês | MEDLINE | ID: mdl-33423493

RESUMO

Levoglucosan (LG) emitted from non-biomass burning (non-BB) sources has given rise to biased or even unreasonable source identification results when adopting LG as a distinct marker of biomass burning (BB). The estimation of LG emission and its spatiotemporal variation for various sources are the keys to reducing uncertainty. This study first developed a LG emission inventory for China from 25 sub-type sources belonging to eight categories, with a 3 km × 3 km spatial resolution and monthly distribution. The total LG emission in 2014 was 145.7 Gg. Domestic BB and open BB contributed 39.2 and 34.3% of the total emission. Non-BB sources, including municipal solid waste burning (9.7%), firework burning (9.6%), meat cooking (5.4%), domestic coal burning (1.5%), ritual item burning (0.2%), and industrial coal burning (0.1%), contributed to 26.5% of the total emission. LG emission varied spatially and temporally. Non-BB sources have a significant spatiotemporal impact on BB source contributions, even in high BB emission regions or in sowing, harvesting, and winter heating seasons. The local BB contributions have been substantially overestimated by 4.28-369% in previous studies, wherein LG was solely referred to as the BB source. By 2018, LG emission from BB might decrease to 63.9% of its total emission. This high-resolution LG emission inventory can be greatly useful for source identification studies in China. It also supports future research on the modeling of smoke aging and pollution control.

2.
Faraday Discuss ; 2021 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-33411881

RESUMO

Haze episodes, characterised by extremely high aerosol concentrations and a reduction in visibility to less than 10 km, are a frequent occurrence in wintertime Beijing, despite policy interventions leading to an overall improvement in average annual air quality. The main drivers in the onset of haze episodes in wintertime Beijing are changing synoptic conditions, however, aerosol-radiation interactions and their feedback on boundary layer meteorology are thought to play an essential role in the intensity and longevity of haze episodes. In this study we use a coupled LES aerosol-radiation model (UCLALES-SALSA), which we have recently configured for the urban environment of Beijing. The model's high resolution and control over meteorological and aerosol conditions as well as atmospheric processes means we can directly elucidate and quantify the importance of specific aspects of the aerosol-radiation-meteorology feedback in the cumulative stage of Beijing haze. The main results presented here show (a) synoptic scale meteorology has a larger impact on boundary layer suppression than high aerosol concentrations and (b) unlike previous results obtained using regional models or observationally driven analyses, there is no threshold value at which the aerosol-radiation-meteorology feedback has a significant effect on PBL height. Rather, our work shows that for the aerosol composition in this case study, the role of the feedback effect in reducing PBL height increases under shallow boundary layer conditions and with increasing pollution loading in an almost linear fashion. This lack of a threshold found for our case study has important policy implications since interventions based on such a value will not result in large reductions associated with turning off the feedback process. Furthermore, this work directly shows that although the right synoptic changes are a prerequisite for pollution episodes in Beijing, local and regional emissions drive increases in aerosol load that are sufficient to initiate the aerosol feedback loop. This further drives suppression of the boundary layer top and promotes stagnation of air and increased stability, which can be self-sustaining. This results in higher surface aerosol concentrations for extended periods of time, with severe consequences for human health [Lv et al., Atmos. Environ., 2016, 124, 98-108; Wang et al., Atmos. Chem. Phys., 2019, 19(10), 6949-6967].

3.
Environ Int ; 146: 106197, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33271442

RESUMO

Biological particles in the Earth's atmosphere are a distinctive category of ice nucleating particles (INPs) due to their capability of facilitating ice crystal formation in clouds at relatively warm temperatures. Field observations and model simulations have shown that biological INPs affect cloud and precipitation formation and regulate regional or even global climate, although there are considerable uncertainties in modeling and large gaps between observed and model simulated contribution of biological particles to atmospheric INPs. This paper overviews the latest researches about biological INPs in the atmosphere. Firstly, we describe the primary ice nucleation mechanisms, and measurements and model simulations of atmospheric biological INPs. Secondly, we summarize the ice nucleating properties of biological INPs from diverse sources such as soils or dust, vegetation (e.g., leaves and pollen grains), sea spray, and fresh waters, and controlling factors of biological INPs in the atmosphere. Then we review the abundance and distribution of atmospheric biological INPs in diverse ecosystems. Finally, we discuss the open questions in further studies on atmospheric biological INPs, including the requirements for developing novel detection techniques and simulation models, as well as the comprehensive investigation of characteristics and influencing factors of atmospheric biological INPs.

4.
Environ Pollut ; 268(Pt A): 115906, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-33120333

RESUMO

Fluorescence spectroscopy is a commonly used technique to analyze dissolved organic matter in aquatic environments. Given the high sensitivity and non-destructive analysis, fluorescence has recently been used to study water-soluble organic carbon (WSOC) in atmospheric aerosols, which have substantial abundance, various sources and play an important role in climate change. Yet, current research on WSOC characterization is rather sparse and limited to a few isolated sites, making it challenging to draw fundamental and mechanistic conclusions. Here we presented a review of the fluorescence properties of atmospheric WSOC reported in various field and laboratory studies, to discuss the current advances and limitations of fluorescence applications. We highlighted that photochemical reactions and relevant aging processes have profound impacts on fluorescence properties of atmospheric WSOC, which were previously unnoticed for organic matter in aquatic environments. Furthermore, we discussed the differences in sources and chemical compositions of fluorescent components between the atmosphere and hydrosphere. We concluded that the commonly used fluorescence characteristics derived from aquatic environments may not be applicable as references for atmospheric WSOC. We emphasized that there is a need for more systematic studies on the fluorescence properties of atmospheric WSOC and to establish a more robust reference and dataset for fluorescence studies in atmosphere based on extensive source-specific experiments.


Assuntos
Poluentes Atmosféricos , Carbono , Aerossóis/análise , Poluentes Atmosféricos/análise , Carbono/análise , Monitoramento Ambiental , Fluorescência , Material Particulado/análise , Água
5.
Environ Pollut ; 268(Pt B): 115952, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-33168376

RESUMO

Severe haze episodes in cold season in Beijing have been mitigated greatly during the last decade. However, the changes in aerosol chemistry as responses to the large reductions in gaseous precursors during the two phases of clean air action, i.e., phase Ⅰ (2013-2017) and phase Ⅱ (2018-2020), are less understood. Here we characterized such changes in cold season (January-March) by using five-year real-time aerosol particle composition measurements. Our results showed consistently large reductions for all chemical species from 2013 to 2020 with the largest decreases being chloride (95%) and organics (74%) followed by sulfate (69%), while the decreases in nitrate were comparatively small (44%). However, the contributions of sulfate were fairly stable despite the increased nitrate contributions from 18% in 2013 to 30% in 2020. Organic aerosol (OA) composition also changed significantly since 2018 with large increases in the contributions of secondary OA and corresponding decreases in primary OA from fossil fuel combustion and cooking emissions. The changes in aerosol chemistry were closely related to the different reductions in gaseous precursors, e.g., SO2 vs. NO2, and the enhanced secondary processes, e.g., the increases in O3, sulfur and nitrogen oxidation efficiency. Further, we found that the changes in aerosol chemistry in cold season during the phase Ⅱ of clean air action (2018-2020) started to slow down with relatively small changes in PM2.5 and secondary inorganic species. Our results point towards a future challenge in mitigating air pollution in cold season, and the need of more stringent and scientific strategies to control secondary aerosol pollution in an environment with enhanced oxidation capacity and high precursors.


Assuntos
Poluentes Atmosféricos , Poluição do Ar , Aerossóis/análise , Poluentes Atmosféricos/análise , Poluição do Ar/análise , Pequim , China , Monitoramento Ambiental , Material Particulado/análise , Estações do Ano
6.
Environ Pollut ; : 116031, 2020 Nov 23.
Artigo em Inglês | MEDLINE | ID: mdl-33261960

RESUMO

Air quality has been significantly improved in China in recent years; however, our knowledge of the long-term changes in health risks from exposure to air pollutants remain less understood. Here we investigated the temporal variations and spatial distributions of six criteria pollutants (SO2, NO2, O3, CO, PM2.5 and PM10) in Beijing-Tianjin-Hebei (BTH), Yangtze River Delta (YRD) and Pearl River Delta (PRD) during 2015-2019. SO2 showed 36-60% reductions in three regions, comparatively, NO2 decreased by 3-17% in BTH and YRD and had a 5% increase in PRD. PM2.5 and PM10 showed the largest reductions in BTH (30-33%) and the lowest in PRD (7-13%), while O3 increased by 9% during 2015-2019 particularly in BTH and YRD. Assuming that only air pollutants above given thresholds exert excess risk (ERtotal) of mortality, we found that the different variations of pollutants have caused ERtotal in BTH decreasing significantly from 4.8% in 2015 to 2.0% in 2019, while from 1.9% to 1.0% in YRD, and a small change in PRD. These results indicate substantially decreased health risks of mortality from exposure to air pollutants as a response to improved air quality. Overall, PM2.5 dominated ERtotal accounting for 42-53% in BTH and 58-64% in YRD with steadily increased contributions, yet ERtotal presented strong seasonal dependence on air pollutants with largely increased contribution of O3 in summer. The ERtotal caused by SO2 was decreased substantially and became negligible except in winter in BTH, while NO2 only played a role in winter. We also found that ERPM2.5 was compositional dependent with organics being the major contributor at low ERPM2.5 while nitrate was more important at high ERPM2.5. Our results highlight that evaluation of public health risks of air pollution needs to consider chemical differences of PM in different regions in addition to dominant air pollutants in different seasons.

7.
Faraday Discuss ; 2020 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-33284304

RESUMO

Fine-particle pollution associated with winter haze threatens the health of more than 400 million people in the North China Plain. The Multiphase chemistry experiment in Fogs and Aerosols in the North China Plain (McFAN) investigated the physicochemical mechanisms leading to haze formation with a focus on the contributions of multiphase processes in aerosols and fogs. We integrated observations on multiple platforms with regional and box model simulations to identify and characterize the key oxidation processes producing sulfate, nitrate and secondary organic aerosols. An outdoor twin-chamber system was deployed to conduct kinetic experiments under real atmospheric conditions in comparison to literature kinetic data from laboratory studies. The experiments were spanning multiple years since 2017 and an intensive field campaign was performed in the winter of 2018. The location of the site minimizes fast transition between clean and polluted air masses, and regimes representative for the North China Plain were observed at the measurement location in Gucheng near Beijing. The consecutive multi-year experiments document recent trends of PM2.5 pollution and corresponding changes of aerosol physical and chemical properties, enabling in-depth investigations of established and newly proposed chemical mechanisms of haze formation. This study is mainly focusing on the data obtained from the winter campaign 2018. To investigate multiphase chemistry, the results are presented and discussed by means of three characteristic cases: low humidity, high humidity and fog. We find a strong relative humidity dependence of aerosol chemical compositions, suggesting an important role of multiphase chemistry. Compared with the low humidity period, both PM1 and PM2.5 show higher mass fraction of secondary inorganic aerosols (SIA, mainly as nitrate, sulfate and ammonium) and secondary organic aerosols (SOA) during high humidity and fog episodes. The changes in aerosol composition further influence aerosol physical properties, e.g., with higher aerosol hygroscopicity parameter κ and single scattering albedo SSA under high humidity and fog cases. The campaign-averaged aerosol pH is 5.1 ± 0.9, of which the variation is mainly driven by the aerosol water content (AWC) concentrations. Overall, the McFAN experiment provides new evidence of the key role of multiphase reactions in regulating aerosol chemical composition and physical properties in polluted regions.

8.
Faraday Discuss ; 2020 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-33283833

RESUMO

Wintertime urban air pollution in many global megacities is characterised by episodic rapid increase in particulate matter concentrations associated with elevated relative humidity - so-called haze episodes, which have become characteristic of cities such as Beijing. Atmospheric chemistry within haze combines gas- and condensed-phase chemical processes, leading to the growth in secondary species such as sulphate aerosols. Here, we integrate observations of reactive gas phase species (HONO, OH, NOx) and time-resolved aerosol composition, to explore observational constraints on the mechanisms responsible for sulphate growth during the onset of haze events. We show that HONO abundance is dominated by established fast gas-phase photochemistry, but the consideration of the additional formation potentially associated with condensed-phase oxidation of S species by aqueous NO2 leading to NO2- production and hence HONO release, improves agreement between observed and calculated gas-phase HONO levels. This conclusion is highly dependent upon aerosol pH, ionic strength and particularly the parameterisation employed for S(iv) oxidation kinetics, for which an upper limit is derived.

9.
Faraday Discuss ; 2020 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-33237085

RESUMO

Organic aerosols, complicated mixtures of organic compounds, are important constituents of atmospheric particulate matter. However, little is known about the size distributions and vertical profiles of these constituents at a molecular level in the urban boundary layer. Here, we characterized the molecular compositions of size-segregated samples collected simultaneously at two heights (8 m and 260 m above ground level) in urban Beijing during the winter of 2018. The CHO, CHNO, CHOS, and CHNOS subgroups in water-soluble organic carbon were characterized using a 15-T ultrahigh-resolution Fourier transform-ion cyclotron resonance (FT-ICR) mass spectrometer. We found that both their numbers and magnitudes increased with a decrease in the particle size, especially for high molecular weight (HMW) compounds, except CHNOS. The number of CHNOS species also increased in the coarse mode, presumably because the alkalinity could inhibit their hydrolysis in the coarse mode. The compounds in small particles with higher O/C ratios and carbon oxidation state were possibly more aged, while the coarse particles with more lipid- and peptide-like compounds should originate from fresh emissions. Moreover, as the oxidation state increases in small particles, functionalization is enhanced for sulfur-containing compounds with fracturing of the benzene ring, while CHO and CHNO are potentially dominated by demethylation with ring-retaining products. It is worth noting that common compounds with the same molecular characteristics accounted for more than 86% of the total compounds between 260 m and ground level (8 m), demonstrating that the aerosols were well mixed in the urban boundary layer. Nonetheless, the relative content of the compounds was higher at ground level due to the impact of primary emissions, which increased with the particle size. In addition, the compounds in submicron particles were more oxidized at 260 m, while the opposite was observed in the coarse mode.

10.
Sci Total Environ ; : 143081, 2020 Oct 17.
Artigo em Inglês | MEDLINE | ID: mdl-33190904

RESUMO

The variations in physicochemical properties of airborne particles collected during a typical transition from haze to dust were investigated using single particle analysis with transmission and scanning electron microscopes combined with online measurement of chemical compositions of airborne particles in Beijing in February 2013. The transition was divided into three phases based on the weather condition. During haze pollution (Phase 1), gaseous and particle pollutants enhanced gradually. Results from single particle analysis showed that more coatings and more anthropogenic elements (e.g., S) appeared on the surface of fine and coarse particles, which was probably caused by efficient aqueous-phase reactions under high humidity (70%) condition. Phase 2 was dust intrusion episode. PM10 reached over 1000 µg m-3. Larger fractions of mineral particles and bare-like soot particles were observed in fine particles, while the fraction of secondary particles with coatings decreased. The proportion of black carbon in submicron particles also increased. Photochemical oxidation in gas phase likely dominated in secondary formation under high O3 concentration. After the dust episode (Phase 3), secondary formation enhanced obviously. Soot aged quickly and had a larger mode of 0.45 µm than the other phases. The size modes of airborne fine particles during Phases 1 and 3 were 0.35 µm, which were a bit larger than that during Phase 2 (0.24 µm). These results indicate that dust plumes accompanied with strong wind brought mineral particles in both fine and coarse modes and freshly emitted particles with smaller sizes, and swept away pre-presence air pollutants. This study could provide detailed information on the physicochemical properties of airborne particles during typical severe pollution processes in a short time. Such short-term change should be taken into account in order to more accurately assess the environmental, climatic and health-related effects of airborne particles.

11.
Faraday Discuss ; 2020 Nov 26.
Artigo em Inglês | MEDLINE | ID: mdl-33241811

RESUMO

This study aims to critically evaluate the source apportionment of fine particles by multiple receptor modelling approaches, including carbon mass balance modelling of filter-based radiocarbon (14C) data, Chemical Mass Balance (CMB) and Positive Matrix Factorization (PMF) analysis on filter-based chemical speciation data, and PMF analysis on Aerosol Mass Spectrometer (AMS-PMF) or Aerosol Chemical Speciation Monitor (ACSM-PMF) data. These data were collected as part of the APHH-Beijing (Atmospheric Pollution and Human Health in a Chinese Megacity) field observation campaigns from 10th November to 12th December in winter 2016 and from 22nd May to 24th June in summer 2017. 14C analysis revealed the predominant contribution of fossil fuel combustion to carbonaceous aerosols in winter compared with non-fossil fuel sources, which is supported by the results from other methods. An extended Gelencsér (EG) method incorporating 14C data, as well as the CMB and AMS/ACSM-PMF methods, generated a consistent source apportionment for fossil fuel related primary organic carbon. Coal combustion, traffic and biomass burning POC were comparable for CMB and AMS/ACSM-PMF. There are uncertainties in the EG method when estimating biomass burning and cooking OC. The POC from cooking estimated by different methods was poorly correlated, suggesting a large uncertainty when differentiating this source type. The PM2.5 source apportionment results varied between different methods. Through a comparison and correlation analysis of CMB, PMF and AMS/ACSM-PMF, the CMB method appears to give the most complete and representative source apportionment of Beijing aerosols. Based upon the CMB results, fine aerosols in Beijing were mainly secondary inorganic ion formation, secondary organic aerosol formation, primary coal combustion and from biomass burning emissions.

12.
Faraday Discuss ; 2020 Nov 26.
Artigo em Inglês | MEDLINE | ID: mdl-33241817

RESUMO

The hygroscopicity and ability of aerosol particles to act as cloud condensation nuclei (CCN) is important in determining their lifetime and role in aerosol-cloud interactions, thereby influencing cloud formation and climate. Previous studies have used the aerosol hygroscopic properties measured at the ground to evaluate the influence on cloud formation in the atmosphere, which may introduce uncertainty associated with aerosol hygroscopicity variability with altitude. In this study, the CCN behaviour and hygroscopic properties of daily filter collections of PM2.5 from three different heights (8, 120, 260 m) on a tower in Beijing were determined in the laboratory using water, water/methanol and methanol as the atomization solvents. Whilst there was substantial temporal variability in particle concentration and composition, there was little obvious difference in aerosol CCN and hygroscopic behaviour at different heights, although the planetary boundary layer height (PBLH) reduced to below the tower height during the nighttime, suggesting that use of surface hygroscopicity measurements is sufficient for the estimation of aerosol particle activation in clouds. Additionally, the critical coating thickness (in terms of mass ratio of coating/refractory BC, MRc) defining the BC transition between being hydrophobic to hydrophilic, was determined by combining hygroscopic tandem differential mobility analyser (H-TDMA), centrifugal particle mass analyzer (CPMA) and single particle soot photometer (SP2) measurements. The MRc of 250 nm BC-containing particles increased from a background value of between 0.8 and 1.6 to around 4.6 at the onset of the growth event of nanoparticles, decreasing monotonically back to the background level as the event progressed. This indicates that large particles do not act as an effective pre-existing condensation sink of the hygroscopic vapours during the nanoparticle growth events, leading to the 250 nm BC particles requiring more coating materials to transition between being hydrophobic and hydrophilic. These findings show that large particles may be less important in suppressing the new particle formation and subsequent growth in the atmosphere.

13.
Sci Total Environ ; : 143089, 2020 Oct 27.
Artigo em Inglês | MEDLINE | ID: mdl-33160669

RESUMO

Biogenic organic aerosols are important components of atmospheric organic aerosols and play vital roles in atmospheric chemistry, global climate, and biogeochemical cycles of carbon. However, studies on biogenic organic aerosols in the vast regions of the Southern Ocean and over the coastal waters of the Antarctic, especially Antarctic Peninsula, are still extremely limited. To understand the concentrations, molecular composition and seasonality of biogenic organic aerosols in Antarctica, atmospheric aerosols were collected at the Palmer Station on the west Antarctic Peninsula experiencing dramatic climate warming. Molecular marker compounds of fungal spores and secondary organic aerosols formed from the photooxidation of isoprene and monoterpene were analyzed using gas chromatography/mass spectrometry. Concentrations of sugar alcohols and biogenic SOA tracers both presented seasonal patterns with higher average concentrations in summer (90.7 and 122 pg m-3) than in winter (8.88 and 57.2 pg m-3). Sugar alcohols and biogenic SOA tracers were predominated by mannitol and isoprene oxidation products. Relative contributions of fungal-spore organic carbon (OC), isoprene-derived secondary OC (SOC) and monoterpene-derived SOC estimated with tracer-based methods were 26.2%, 55.6% and 18.2%, respectively. The observed seasonality of total biogenic SOA and some molecular species at the Antarctic Peninsula was further supported by the results from the global model CESM/IMPACT. Model results also suggest higher biogenic SOA in East Antarctica than that in West Antarctica, which is attributed to the influence of vertical atmospheric circulation. Our results of air-mass trajectory indicate the potential influence of marine emissions on the biogenic organic aerosols over the Antarctic Peninsula.

14.
Sci Total Environ ; 742: 140739, 2020 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-32721760

RESUMO

The rapidly spread coronavirus disease (COVID-19) has limited people's outdoor activities and hence caused substantial reductions in anthropogenic emissions around the world. However, the air quality in some megacities has not been improved as expected due to the complex responses of aerosol chemistry to the changes in precursors and meteorology. Here we demonstrate the responses of primary and secondary aerosol species to the changes in anthropogenic emissions during the COVID-19 outbreak in Beijing, China along with the Chinese New Year (CNY) holiday effects on air pollution by using six-year aerosol particle composition measurements. Our results showed large reductions in primary aerosol species associated with traffic, cooking and coal combustion emissions by 30-50% on average during the CNY, while the decreases in secondary aerosol species were much small (5-12%). These results point towards a future challenge in mitigating secondary air pollution because the reduced gaseous precursors may not suppress secondary aerosol formation efficiently under stagnant meteorological conditions. By analyzing the long-term measurements from 2012 to 2020, we found considerable increases in the ratios of nitrate to sulfate, secondary to primary OA, and sulfur and nitrogen oxidation capacity despite the overall decreasing trends in mass concentrations of most aerosol species, suggesting that the decreases in anthropogenic emissions have facilitated secondary formation processes during the last decade. Therefore, a better understanding of the mechanisms driving the chemical responses of secondary aerosol to the changes in anthropogenic emissions under complex meteorological environment is essential for future mitigation of air pollution in China.


Assuntos
Poluentes Atmosféricos/análise , Poluição do Ar/análise , Infecções por Coronavirus , Coronavirus , Pandemias , Pneumonia Viral , Aerossóis/análise , Pequim , Betacoronavirus , China , Monitoramento Ambiental , Férias e Feriados , Humanos , Material Particulado/análise
15.
J Environ Sci (China) ; 95: 33-42, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32653190

RESUMO

Vertical profiles of isoprene and monoterpenes were measured by a proton transfer reaction-time of flight-mass spectrometry (PTR-ToF-MS) at heights of 3, 15, 32, 64, and 102 m above the ground on the Institute of Atmospheric Physics (IAP) tower in central Beijing during the winter of 2016 and the summer of 2017. Isoprene mixing ratios were larger in summer due to much stronger local emissions whereas monoterpenes were lower in summer due largely to their consumption by much higher levels of ozone. Isoprene mixing ratios were the highest at the 32 m in summer (1.64 ± 0.66 ppbV) and at 15 m in winter (1.41 ± 0.64 ppbV) with decreasing concentrations to the ground and to the 102 m, indicating emission from the tree canopy of the surrounding parks. Monoterpene mixing ratios were the highest at the 3 m height in both the winter (0.71 ± 0.42 ppbV) and summer (0.16 ± 0.10 ppbV) with a gradual decreasing trend to 102 m, indicting an emission from near the ground level. The lowest isoprene and monoterpene mixing ratios all occurred at 102 m, which were 0.71 ± 0.42 ppbV (winter) and 1.35 ± 0.51 ppbV (summer) for isoprene, and 0.42 ± 0.22 ppbV (winter) and 0.07 ± 0.06 ppbV (summer) for monoterpenes. Isoprene in the summer and monoterpenes in the winter, as observed at the five heights, showed significant mutual correlations. In the winter monoterpenes were positively correlated with combustion tracers CO and acetonitrile at 3 m, suggesting possible anthropogenic sources.


Assuntos
Poluentes Atmosféricos/análise , Ozônio/análise , Compostos Orgânicos Voláteis/análise , Pequim , Monitoramento Ambiental , Monoterpenos/análise
16.
Environ Sci Process Impacts ; 22(8): 1616-1653, 2020 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-32672265

RESUMO

Anthropogenic emissions in Asia have significantly increased during the last two decades; as a result, the induced air pollution and its influences on radiative forcing and public health are becoming increasingly prominent. The Aerodyne Aerosol Mass Spectrometer (AMS) has been widely deployed in Asia for real-time characterization of aerosol chemistry. In this paper, we review the AMS measurements in Asia, mainly in China, Korea, Japan, and India since 2001 and summarize the key results and findings. The mass concentrations of non-refractory submicron aerosol species (NR-PM1) showed large spatial distributions with high mass loadings occurring in India and north and northwest China (60.2-81.3 µg m-3), whereas much lower values were observed in Korea, Japan, Singapore and regional background sites (7.5-15.1 µg m-3). Aerosol composition varied largely in different regions, but was overall dominated by organic aerosols (OA, 32-75%), especially in south and southeast Asia due to the impact of biomass burning. While sulfate and nitrate showed comparable contributions in urban and suburban regions in north China, sulfate dominated inorganic aerosols in south China, Japan and regional background sites. Positive matrix factorization analysis identified multiple OA factors from different sources and processes in different atmospheric environments, e.g., biomass burning OA in south and southeast Asia and agricultural seasons in China, cooking OA in urban areas, and coal combustion in north China. However, secondary OA (SOA) was a ubiquitous and dominant aerosol component in all regions, accounting for 43-78% of OA. The formation of different SOA subtypes associated with photochemical production or aqueous-phase/fog processing was widely investigated. The roles of primary emissions, secondary production, regional transport, and meteorology on severe haze episodes, and different chemical responses of primary and secondary aerosol species to source emission changes and meteorology were also demonstrated. Finally, future prospects of AMS studies on long-term and aircraft measurements, water-soluble OA, the link of OA volatility, oxidation levels, and phase state were discussed.


Assuntos
Poluentes Atmosféricos , Material Particulado , Aerossóis , Ásia , China , Monitoramento Ambiental , Índia , Japão , República da Coreia
17.
Environ Int ; 142: 105878, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32580116

RESUMO

Stand-alone portable air purifiers (APs) have become an increasingly popular method of controlling individual inhalation exposure. Exposure to bacterial endotoxins has a causative role in respiratory inhalation health. Here, we studied the changes in endotoxin levels in indoor air before and after purification by a portable AP equipped with HEPA (high-efficiency particulate air) filters. An increase in endotoxins was observed when a previously used AP was turned on to clean the air. Replacing the HEPA filters in the AP helped to mitigate the increase in endotoxins of larger sizes but not endotoxins of smaller sizes. Consequently, the use of APs could lead to increased endotoxin deposition in airways, especially in the alveolar region. The endotoxin concentrations on the HEPA filters were well correlated with the free DNA concentrations on the HEPA filters. This correlation indicates that the disrupted bacteria, which released free DNA, could also release endotoxins, thus making HEPA filters a source of indoor airborne endotoxins. Our results illustrate a potential endotoxin inhalation risk associated with HEPA-APs as an air cleaning strategy and highlight the importance of composition-specific air cleaning while reducing the particle number/mass.


Assuntos
Filtros de Ar , Poluição do Ar em Ambientes Fechados , Poluição do Ar em Ambientes Fechados/análise , Bactérias , Poeira , Endotoxinas
18.
Sci Total Environ ; 739: 139791, 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-32535462

RESUMO

The effect of the nonsphericity of mineral dust aerosols on its deposition and transport was investigated based on model simulation for a typical dust event over northern China from April 6 to 12, 2018. The settling velocity related to morphological change in dust size was considered in Nested Air Quality Prediction Modeling System (NAQPMS) to simulate the dust spatial distribution. Comparison of these results with observations showed that the model reproduced the temporal variability in the mass concentration of particles along the dust plume pathway. The most frequently reported aspect ratio (λ) was 1.7 ± 0.2 for Asian dust aerosols. Changing the nonsphericity of the particle from typical prolate ellipsoids (λ = 1.7) to spherical ellipsoids (λ = 1) caused an ~3% decrease in the surface dust concentration on average. For particles with diameters >5 µm, nonsphericity caused a change in the surface dust concentration up to 10%, especially at the periphery of the dust source region. The overall effects on the fine dust (<2.5 µm) were not significant. A sensitivity study using a more extreme nonspherical shape (λ = 2) showed that the differences in PM10 concentration were evident, and the surface dust concentration increased by 15 ± 5% as a result of an ~10% decrease in settling velocity. These results confirmed that the effect of the variability in the nonsphericity of Asian dust particles on their regional transport highly depended on synoptical and pollution conditions, and the adoption of a deposition value that changes over time due to this morphological variability could improve the performance of dust modeling and the assessment of climate effects on a global scale, especially for transboundary processes.

19.
Mass Spectrom Rev ; 2020 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-32412674

RESUMO

Among the different techniques for mass analysis, ultra-high-resolution Fourier transform ion cyclotron resonance (FTICR) is the method of choice for highly complex samples, as it offers unrivaled mass accuracy and resolving power, combined with a high degree of flexibility in hybrid instruments as well as for ion activation techniques. FTICR instruments are readily embraced by the biological and biomedical research communities and applied over a wide range of applications for the analysis of biomolecules such as carbohydrates, lipids, nucleic acids, and proteins. In the field of natural organic matter (NOM) analysis, petroleum-related studies currently dominate FTICR-MS applications. Recently, however, there is a growing interest in developing high-performance MS methods for the characterization of NOM samples from natural aquatic and terrestrial environments. Here, we present an overview of FTICR-MS techniques for complex, non-petroleum NOM samples, including data analysis and novel tandem mass spectrometry (MS/MS) methods for structural classifications. © 2020 The Authors. Mass Spectrometry Reviews published by John Wiley & Sons Ltd.

20.
Chemosphere ; 255: 126850, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32402868

RESUMO

Water-soluble organic aerosol (WSOA) constitutes a large fraction of OA and plays an important role in formation of secondary OA (SOA). Here we characterized the sources and molecular composition of WSOA in summer in Beijing using high-resolution aerosol mass spectrometer and orbitrap mass spectrometer equipped with electrospray ionization. Our results showed that WSOA was the major fraction of OA on average accounting for 69% in summer, which is much higher than that (47%) in winter. However, the oxidation degree of WSOA was comparable between summer and winter (O/C = 0.62 vs. 0.63). Positive matrix factorization analysis showed that SOA contributed dominantly to WSOA (72%) indicating that WSOA was mainly from secondary formation. The two water-soluble SOA factors that are associated with regional processing (OOA-1) and photochemical production (OOA-2), respectively, showed very different behaviors throughout the study. OOA-2 showed much enhanced contribution during polluted periods with low relative humidity (RH), while OOA-1 played a more important role during high RH periods. Molecular composition analysis of WSOA revealed a high diversity of CHO (compounds only containing carbon, hydrogen and oxygen) and CHOS (sulfur-containing organics) in WSOA in summer. Particularly, the relative intensity fraction of CHOS- compounds was increased by 42% from clean to polluted days which was associated with large increases (20%) in organosulfates (OSs) with lower O∗/C (0.1-0.4), and OOA-1. These results suggest the formation of more unsaturated OSs in OOA-1 during polluted days in summer. Comparatively, the biogenic-derived OSs remained relatively stable (24-31%) for the entire study highlighting the ubiquitous importance of biogenic SOA in summer.


Assuntos
Aerossóis/análise , Poluentes Atmosféricos/análise , Monitoramento Ambiental , Pequim , Umidade , Espectrometria de Massas , Oxirredução , Estações do Ano , Água/análise
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