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  • Weekly patterns and weekend effects of air pollution in the Moscow megacity
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-24
    N.F. Elansky; A.V. Shilkin; N.A. Ponomarev; E.G. Semutnikova; P.V. Zakharova

    The weekly cycle and weekend effect in the O3, NO, NO2, CO, CH4, SO2, NMHC, and PM10 concentrations were investigated in the Moscow megacity using in-situ measurements from January 1, 2005 to December 31, 2014 at 49 stations of the Moscow Environment Monitoring network. Daily variations in the CO, NOx, NMHC, and PM10 concentrations depend mainly on motor transport emissions and the atmospheric boundary layer vertical stratification. The characteristic feature of Moscow is the time coincidence of rush hours and surface temperature inversion during the cold season, which results in pollutant accumulation in the atmospheric surface layer. It was found that the surface concentrations of the pollutants (except ozone and methane) decrease on weekends. Weekday (Tuesday–Friday)-Sunday differences in the daytime (08:00–22:00 LT) NO, NO2, CO, SO2, NMHC, and PM10 concentrations relative to those of weekday period averaged for all stations over 2005–2014 amounted to 23.9 ± 5.8, 16.7 ± 2.8, 13.6 ± 3.3, 7.6 ± 6.5, 6.3 ± 2.2, and 14.5 ± 5.1%, respectively. The ozone concentration increased on Sunday by 16.5 ± 4.8%. The methane concentration on weekends was the same as on weekdays. The weekend effects in all pollutant concentrations were weakened within the greenbelt around Moscow. In different sectors of Moscow the pollutant weekend effects except that in SO2 were approximately the same. The vertical structure of the NO, NO2, and CO weekend effects was analyzed based on data obtained from measurements at the TV tower 500 m in height. These weekend effects decreased nonlinearly with height. Estimates obtained for basic criteria of activity of photochemical processes determining the formation of the weekly cycle and weekend effect of ozone (NMHC/NOx ratio, fraction of radical loss via NOx chemistry, concentration of Ox) show that the VOC-limited chemistry is characteristic of Moscow.

    更新日期:2020-01-24
  • Atmospheric reactive nitrogen concentration and deposition trends from 2011 to 2018 at an urban site in north China
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-24
    Xiaosheng Luo; Xuejun Liu; Yuepeng Pan; Zhang Wen; Wen Xu; Lin Zhang; Changlin Kou; Jinling Lv; Keith Goulding

    Atmospheric reactive nitrogen (Nr) emission and deposition have caused much damage to the global environment and also impacted human health. Determining long-term trends in atmospheric Nr concentrations and deposition is important for evaluating air quality and ecosystem effects and formulating control measures to reduce negative impacts. We measured monthly concentrations of NH3, pNH4+, HNO3, pNO3-, and NO2 and calculated their dry deposition rates using an inferential method from 2011 to 2018 at an urban site in Zhengzhou in the North China Plain. Inorganic N (NH4+ and NO3−) concentrations in precipitation and wet/bulk N deposition were also quantified in 2011, 2016, 2017 and 2018. The results showed high concentrations of atmospheric Nr species, with considerable variation in some species over the monitoring period. Annual mean NH3 concentrations significantly increased from 2011 to 2018 (p < 0.001) with that in 2018 being twice that in 2011. However, pNO3- and pNH4+ concentrations decreased after 2013. The annual mean NO2 concentration in 2018 had decreased by 33.4% compared to the peak in 2011. Highest NH3 concentrations were measured in spring or summer, and lowest concentrations in winter. pNH4+ and pNO3- concentrations peaked mainly in winter. Total dry N deposition ranged from 21.9 to 41.2 kg N ha−1. Bulk NH4+ and NO3− deposition was lower in 2016–2018 than in 2011. However, atmospheric Nr concentrations and N deposition remained high in this urban ecosystem. NH3 emissions urgently need control measures, and Nr impacts on the surrounding ecosystems and human health should be considered. Continuous long-term measurements of atmospheric Nr concentrations and deposition at a regional scale are necessary to help formulate emission control measures and protect human and ecosystem health.

    更新日期:2020-01-24
  • Asian dust observed during KORUS-AQ facilitates the uptake and incorporation of soluble pollutants during transport to South Korea
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-24
    E.W. Heim; J. Dibb; E. Scheuer; P. Campuzano Jost; B.A. Nault; J.L. Jimenez; D. Peterson; C. Knote; M. Fenn; J. Hair; A.J. Beyersdorf; C. Corr; B.E. Anderson

    The air quality of South Korea was the focus of the NASA/NIER KORean -United States Air Quality (KORUS-AQ) mission of 2016. KORUS-AQ was planned for the period after the spring peak in outbreaks of Asian dust. Regardless of this strategic planning, quantifiable dust was still observed via instrumentation on the NASA DC-8 in early May. A novel analysis of supermicron dust and associated supermicron ionic relationships was completed using two size dependent instruments. This supermicron dust provided surface area for heterogeneous chemistry between CaCO3, the gases HNO3, NO2, and SO2, and particulate (NH4)2SO4. Uptake of the pollutant gases is greatly enhanced by formation of an aqueous layer on the surface of the dust particles. More water is attracted to particles where uptake of HNO3 has replaced surface CaCO3 with Ca(NO3)2 generating a dynamic aqueous layer on the dust particle. We propose that particulate (NH4)2SO4 coagulated with dust to form (NH4)2Ca(SO4)2 on the particle surface, which rapidly formed CaSO4 and NH4+ in a Ca(NO3)2 facilitated aqueous layer. A conceptual model is proposed to explain these dust uptake chemical processes. We define the nanoequivalent concentration of supermicron SO42− plus NO3− over the nanoequivalent concentration of supermicron NH4+ plus Ca2+ as the Dust Pollution Index (DPI), used to quantify the extent to which carbonate dust has been modified. DPI values range from 0 (pure dust) to 1 (completely reacted); thus, it represents the conversion of CaCO3 into secondary salts. This mechanism should be used to better predict chemical dynamics in atmospheric models while also helping to further explain the importance of dust and secondary coating on cloud formation processes and dust optical properties. Air masses containing dust that traversed industrial China while mixing with polluted southern air had significantly higher DPI values (average = 0.82, 1σ = 0.10) compared to air masses that limited interaction with such pollution (average = 0.51, 1σ = 0.13).

    更新日期:2020-01-24
  • Real-world emissions from non-road mobile machinery in London
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-24
    C.D. Desouza; D.J. Marsh; S.D. Beevers; N. Molden; D.C. Green
    更新日期:2020-01-24
  • Fluorescence characteristics of particulate water-soluble Organic Compounds Emitted from coal-fired boilers
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-23
    Yanrong Yang; Juanjuan Qin; Ting Qi; Xueming Zhou; Rongzhi Chen; Jihua Tan; Kang Xiao; Dongsheng Ji; Kebin He; Xiaoting Chen
    更新日期:2020-01-23
  • Contrasts in chemical composition and oxidative potential in PM10 near flares in oil extraction and refining areas in Ecuador
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-23
    F. Barraza; G. Uzu; J.-L. Jaffrezo; E. Schreck; H. Budzinski; K. Le Menach; M.-H. Dévier; H. Guyard; A. Calas; M.-I. Perez; L.-A. Villacreces; L. Maurice
    更新日期:2020-01-23
  • Interannual variation of the East Asia Jet Stream and its impact on the horizontal distribution of aerosol in boreal spring
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-22
    Seunghee Lee; Myong-In Lee; Chang-Keun Song; Kyu-Myong Kim; Arlindo M. da Silva

    Interannual variation of the aerosol optical depth (AOD) in East Asia has been investigated using Moderate Resolution Imaging Spectroradiometer (MODIS) data and Modern Era Retrospective analysis for Research and Applications Version 2 (MERRA-2) data for 2000–2018. The data analysis focuses on boreal spring when Siberian biomass burning is at its seasonal maximum. The results indicate that the significant increase in organic and black carbon is primarily caused by emissions from biomass burning in East Asia, which leads to significant interannual variations in aerosol loading and pan-Pacific transport. The anomalous large-scale climate variability associated with the East Asia Jet Stream (EAJS) provides favorable conditions for increasing the AOD of organic and black carbon in Northeast Asia and may represent an underlying physical mechanism. When the EAJS shows greater weakening than normal, abnormal high-pressure anomalies are maintained in East Asia, which tend to drive warm advection over Northeast Asia. This warm advection expedites the melting of the Eurasian snow cover, which helps increase surface dryness in late spring and provides favorable conditions for biomass burning. The EAJS index can be predictable with statistical significance up to lead 1 month by the dynamical ensemble seasonal forecasts, suggesting a possible implementation of the empirical AOD forecasts using climate forecast models.

    更新日期:2020-01-22
  • Analysis of black carbon on filters by image-based reflectance
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-20
    Matthew Jeronimo; Quinn Stewart; Andrew T. Weakley; Jason Giacomo; Xiaolu Zhang; Nicole Hyslop; Ann M. Dillner; Matthew Shupler; Michael Brauer

    Black carbon (BC) is an important contributor to global particulate matter emissions. BC is associated with adverse health effects, and an important short-lived climate pollutant. Here, we describe a low cost method of analysis that utilizes images of PTFE filters taken with a digital camera to estimate BC content on filters. This method is compared with two existing optical methods for analyzing BC (Smokestain Reflectance and Hybrid Integrating Plate and Sphere System) as well as the standard chemical analysis method for determining elemental carbon (Thermal-Optical Reflectance). In comparisons of aerosol generated under controlled conditions (using an inverted diffusion flame burner to cover a range of mass loading and reflectance levels) (N = 12) and in field samples collected from residential solid fuel combustion in China and India (N = 50), the image-based method was found to correlate well (normalized RMSE <10% for all comparisons) with existing methods. A correlational analysis of field samples between the optical methods and Fourier-transform infrared spectroscopy indicated that the same functional groups were predominantly responsible for light attenuation in each optical method. This method offers reduced equipment cost, rapid analysis time, and is available at no cost, which may facilitate more measurement of BC where PM2.5 mass concentrations are already measured, especially in low income countries or other sampling efforts with limited resources.

    更新日期:2020-01-21
  • Use of low-cost PM monitors and a multi-wavelength aethalometer to characterize PM2.5 in the Yakama Nation reservation
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-20
    Orly Stampfer; Elena Austin; Terry Ganuelas; Tremain Fiander; Edmund Seto; Catherine Karr

    Rural lower Yakima Valley, Washington is home to the reservation of the Confederated Tribes and Bands of the Yakama Nation, and is a major agricultural region. Episodic poor air quality impacts this area, reflecting sources of particulate matter with a diameter of less than 2.5 μm (PM2.5) that include residential wood smoke, agricultural biomass burning and other emissions, truck traffic, backyard burning, and wildfire smoke. University of Washington partnered with the Yakama Nation Environmental Management Program to investigate characteristics of PM2.5 using 9 months of data from a combination of low-cost optical particle counters and a 5-wavelength aethalometer (MA200 Aethlabs) over 4 seasons and an episode of summer wildfire smoke. The greatest percentage of hours sampled with PM2.5 >12 μg/m3 occurred during the wildfire smoke episode (59%), followed by fall (23%) and then winter (21%). Mean (SD) values of Delta-C (μg/m3), which has been posited as an indicator of wood smoke, and determined as the mass absorbance difference at 375–880 nm, were: summer – wildfire smoke 0.34 (0.52), winter 0.27 (0.32), fall 0.10 (0.22), spring 0.05 (0.11), and summer – no wildfire smoke 0.04 (0.14). Mean (95% confidence interval) values of the absorption Ångström exponent, an indicator of the wavelength dependence of the aerosol, were: winter 1.5 (1.2–1.8), summer – wildfire smoke 1.4 (1.0–1.8), fall 1.3 (1.1–1.4), spring 1.2 (1.1–1.4), and summer – no wildfire smoke 1.2 (1.0–1.3). The trends in Delta-C and absorption Ångström exponents are consistent with expectations that a higher value reflects more biomass burning. These results suggest that biomass burning is an important contributor to PM2.5 in the wintertime, and emissions associated with diesel and soot are important contributors in the fall; however, the variety of emissions sources and combustion conditions present in this region may limit the utility of traditional interpretations of aethalometer data. Further understanding of how to interpret aethalometer data in regions with complex emissions would contribute to much-needed research in communities impacted by air pollution from agricultural as well as residential sources of combustion.

    更新日期:2020-01-21
  • Relative contribution of mineral dust versus black carbon to Third Pole glacier melting
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-18
    Zhaofu Hu; Shichang Kang; Xiaofei Li; Chaoliu Li; Mika Sillanpää
    更新日期:2020-01-21
  • Characteristics and determinants of personal exposure to PM2.5 mass and components in adult subjects in the megacity of Guangzhou, China
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-18
    Xiao-Cui Chen; Heiko J. Jahn; Tony J. Ward; Hung Chak Ho; Ming Luo; Guenter Engling; Alexander Kraemer

    Understanding the heterogeneity between ambient concentration and personal exposure is crucial in studies regarding the health risks of air pollution exposure. We performed a panel study with 4–19 (average = 10) repeated personal monitoring in 16 adult subjects (ages 18–30) for three consecutive weeks during the winter and summer of 2011–2012 in the Chinese megacity of Guangzhou. Also, we conducted simultaneous ambient measurements at eight districts (including five urban sites, two suburban locations, and one rural site) of Guangzhou. Significant seasonal variations were shown in personal PM2.5 exposure for most of the analyzed components (p < 0.05), with higher levels in winter than in summer. Average personal exposures exhibited a pattern of central urban > suburban > rural areas for PM2.5 mass and most of the constituents (e.g., carbonaceous aerosols, ions). We applied mixed-effects models to estimate within- and between-subject variance components and determinants of personal PM2.5 exposure after adjusting for potential confounders. The within-subject variance component dominated the total variability (63.7–95.6%) for most of the investigated PM2.5 components. Ambient PM2.5 mass and its components were the dominant predictors and contributors of the corresponding personal exposures (0.11 < Rc2 < 0.97; p < 0.05). The results indicate that season and district type affect personal PM2.5 exposure and its components, contributing to 4.9–51.6% and 8.0–77.8% of the variability. Time indoors and outdoors were also factors affecting personal exposure. The study findings revealed ambient concentrations at a fixed monitoring station underestimated residents’ true exposure levels. In conclusion, the current study emphasizes the need for incorporating spatio-temporal activity patterns complementing evenly-distributed air quality monitoring networks to increase the estimation power in epidemiological analysis linking true personal exposure to health effects.

    更新日期:2020-01-21
  • Integrating low-cost air quality sensor networks with fixed and satellite monitoring systems to study ground-level PM2.5
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-17
    Jiayu Li; Huang Zhang; Chun-Ying Chaoa; Chih-Hsiang Chien; Chang-Yu Wu; Cyuan Heng Luo; Ling-Jyh Chen; Pratim Biswas

    Airborne particulate matter (PM) mass concentrations measured by conventional monitoring stations are reliable data sources for air quality communication, pollution mapping, and exposure estimation. A high spatiotemporal density of monitoring stations can provide a better understanding of PM transport on a regional and global scale and help to reduce exposure misclassification leading to a better assessment of the health impacts associated with PM exposure. However, due to the cost and operational complexities, only a limited number of such PM monitors can be deployed. Apart from conventional measurements, PM mass concentration can be estimated from aerosol optical depth (AOD) data observations by using empirical, semi-empirical or modeling methods, but these datasets are usually compromised by weather conditions and lack of knowledge of aerosol properties. In addition to the above methods, a network of low-cost PM sensors is also a promising approach to increase the measurement density. In this study, we propose an integration of information from multiple measurement approaches. We demonstrate this approach by synergizing the data from 75 monitoring stations, 2,363 Air Box low-cost sensors (the amount of data entries is ∼10 million), and the Terra remote sensing satellite to estimate surface concentrations of PM for Taiwan Main Island during July 14 2018 to Oct 31 in 2018. A machine learning method selects the useful data from the low-cost sensor datasets, and the ordinary Kriging method is used to create a visual daily PM distribution map. The integration of datasets can enhance the overall data quantity and quality, leading to more accurate pollution maps with greater detail. The maps created from these three data sources demonstrate an approximate 30-fold synergistic improvement in the spatial resolution of PM mapping. The Root Mean Square Error (RMSE) of the predicted maps was analyzed through leave-one-out cross-validation, ten-fold cross-validation, and standard data validation. It shows that including low-cost PM sensor data brings in greater detail and largely enhances the spatial distribution while maintaining the pollution mapping characteristics. The approach described here will greatly assist the validation of PM transport models and enhance the accuracy of exposure estimations in future studies.

    更新日期:2020-01-21
  • Towards the coupling of a chemical transport model with a micro-scale Lagrangian modelling system for evaluation of urban NOx levels in a European hotspot
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-17
    Giorgio Veratti; Sara Fabbi; Alessandro Bigi; Aurelia Lupascu; Gianni Tinarelli; Sergio Teggi; Giuseppe Brusasca; Tim M. Butler; Grazia Ghermandi
    更新日期:2020-01-21
  • Cross-sectional associations between ambient air pollution and respiratory signs and symptoms among young children in Tehran
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-17
    Zahra Namvar; Masud Yunesian; Mansour Shamsipour; Mohammad Sadegh Hassanvand; Kazem Naddafi; Elahe Shahhosseini
    更新日期:2020-01-17
  • Application of land use regression to assess exposure and identify potential sources in PM2.5, BC, NO2 concentrations
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-17
    Jing Cai; Yihui Ge; Huichu Li; Changyuan Yang; Cong Liu; Xia Meng; Weidong Wang; Can Niu; Lena Kan; Tamara Schikowski; Beizhan Yan; Steven N. Chillrud; Haidong Kan; Li Jin
    更新日期:2020-01-17
  • Nitrogen and sulfur deposition over a region in SW Europe based on a regional atmospheric chemical transport model
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-16
    M.A. Oliveira; S.J. Tomlinson; E.J. Carnell; A.J. Dore; H.C. Serrano; M. Vieno; C.M.d.S. Cordovil; U. Dragosits; M.A. Sutton; C. Branquinho; P. Pinho

    Air quality affects both ecosystems and human health. To assess the effects of air pollution, spatially explicit information of pollutants is needed. Atmospheric chemistry transport models are the best option to estimate concentrations and deposition of pollutants from local to regional scales. However, concentration and deposition maps derived from available regional and global models are typically given at spatial resolutions of 10–50 km and do not contain information at sufficiently high spatial resolution (i.e. ≤ 5 km × 5 km) to identify risks and to develop solutions to protect ecosystems and human health. Here we provide deposition and concentrations of nitrogen (N) and sulfur (S) at a 5 km × 5 km resolution for the western Iberian Peninsula. The new maps are a major improvement over existing information due to the higher spatial resolution. Comparisons with measurements indicate that all maps for N compounds are fit for purpose. Nitrogen deposition in W Iberia ranged from 3 to 38.6 kg N·ha−1·year−1, averaging ∼8.2 kg N·ha−1·year−1 with a higher contribution from reduced N forms (62%). Deposition of oxidized forms mainly prevailed in urban and industrial areas and in coastal locations. The contribution of wet deposition was slightly higher (55%) than dry deposition and more important in the North, following the pattern of precipitation. Dry deposition is higher closer to emission sources. Due to their high spatial resolution, these maps can be used for policy development to support ecosystem protection, through the identification of areas at greater risk due to high N deposition. National policy efforts to reduce N pollution must, foremost, target ammonia (NH3) emissions in rural areas and oxidized nitrogen (NOx) emissions in urban and industrialized areas.

    更新日期:2020-01-17
  • A comprehensive study of particulate and gaseous emissions characterization from an ocean-going cargo vessel under different operating conditions
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-16
    Jingbo Zhao; Yanjie Zhang; Zhiwen Yang; Yan Liu; Shitao Peng; Ningning Hong; Jianbo Hu; Ting Wang; Hongjun Mao

    This study investigated particulate and gaseous emission factors (EFs) from an ocean-going cargo vessel operating under different real-world conditions. EFs were determined for criteria gaseous (including NO, NO2, CO, CO2, SO2) and particulate pollutants (including PM2.5 and PM2.5 components, such as organic carbon, elemental carbon, BC, water-soluble inorganic ions and metal elements). The results showed that the gaseous emissions were dominated by CO2 and NO, the EFs of which were ranging from 489 g/kWh to 1040 g/kWh, and 11.2 g/kWh to 29.1 g/kWh, respectively. And the EFs of PM2.5 were ranging from 0.13 g/kWh to 1.12 g/kWh. Vanadium, silicon, calcium and nickel were the main contributors to the presence of inorganic metal elements. Marine diesel oil (MDO) and heavy fuel oil (HFO) were used in the cargo vessels sailing along the coastline and in the ocean, respectively. When using MDO instead of HFO, the SO2, NOX and PM2.5 emissions were reduced by 5%, 90% and 60%, respectively. There seemed no obvious effect of the fuel type on the CO2 emission. Besides, the CO2 and SO2 emissions of HFO were linearly correlated with PM2.5. Moreover, the energy efficiency management system (EEMS) was used to estimate the relationship between emissions and engine working conditions. Effective thermal efficiency (ηet) was calculated based on combustion status. CO and BC decreased with increasing ηet for both HFO and MDO, while NO increased with increasing ηet. These results could provide important data support for the use of certification values for emissions inventories.

    更新日期:2020-01-16
  • On-road tailpipe emission characteristics and ozone formation potentials of VOCs from gasoline, diesel and liquefied petroleum gas fueled vehicles
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-14
    Menglei Wang; Shunyi Li; Rencheng Zhu; Ruiqin Zhang; Lei Zu; Yunjing Wang; Xiaofeng Bao

    Volatile organic compounds (VOCs) of motor vehicles contribute greatly to ground-level ozone formation, especially in the megacity regions. While the variations of tailpipe VOC emissions along with the vehicle technologies and road conditions are rarely investigated systematically. Thus, on-road tailpipe VOC emissions from in-use vehicles, including light-duty gasoline vehicles (LDGV), light-duty diesel trucks (LDDT), heavy-duty diesel truck (HDDT) and liquefied petroleum gas-electric hybrid bus (LPGB), were sampled with a combined portable emission measurement system (PEMS). A total of 102 individual VOC species were quantified by a gas chromatography mass spectrometry detector (GC-MSD), and the maximum incremental reactivity (MIR) scale was used to calculate the ozone formation potentials (OFPs). Results showed that aromatics and alkanes were the major VOC groups regardless of the vehicle type, accounting for 68.1–98.0%. For the LDGV, i-pentane, acetone, and propane were the top three VOC species. Naphthalene, dodecane and n-undecane were main VOC constituents in the diesel exhaust. Acetone was the most abundant VOC species for the LPGB, followed by i-pentane, i-butane and n-butane. Road conditions had a significant impact on the VOC emission factors. Specifically, emission factors on urban roads were 3.3–7.0 times those on the highway. The OFPs were 70.7, 128.1, 2189.4 and 124.7 mg O3/km for the LDGV, LDDT, HDDT and LPGB, respectively; aromatics were the main contributors, occupying 49.6–93.4% of the total OFPs. Results indicated that emission factors and dominant species of VOCs were strongly affected by vehicle technologies and road conditions, but aromatics were the major group for both VOC composition and OFPs.

    更新日期:2020-01-15
  • Improved method for the optical analysis of particulate black carbon (BC) using smartphones
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-13
    Gang Chen; Qi Wang; Yunfei Fan; Yiqun Han; Yanwen Wang; Bruce Urch; Frances Silverman; Mi Tian; Yushan Su; Xinghua Qiu; Tong Zhu; Arthur W.H. Chan

    Black carbon (BC) is a major component in atmospheric particulate matter (PM), which causes adverse health impacts and contributes significantly to climate change. Without widespread and accurate BC measurements, it remains difficult to track incomplete combustion sources and reduce BC emissions. Currently commercial BC sensors remain too costly to be deployed widely. In this work, a fast, cost-effective, and easily accessible method based on a smartphone camera was used to quantify color information of PM collected on filters to estimate BC and elemental carbon (EC) loadings. A robust RGB (red, green, blue)-based linear interaction model was built and validated using 1,878 PM samples collected in three different regions with collocated BC and EC measurements. After applying image correction methods, this model shows a good predictability with an R-squared (R2) of 0.904 with state-of-the-art BC measurement techniques, and a coefficient of variation of the root mean square error (CV(RMSE)) of 25.3% despite the complex sources and different reference measurement techniques. This work validates the viabilities of using smartphones to quantify BC or EC loading on PM filters with a unified model and track incomplete combustion sources.

    更新日期:2020-01-14
  • 更新日期:2020-01-13
  • Low-cost sensor networks and land-use regression: Interpolating nitrogen dioxide concentration at high temporal and spatial resolution in Southern California
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-13
    Lena Weissert; Kyle Alberti; Elaine Miles; Georgia Miskell; Brandon Feenstra; Geoff S. Henshaw; Vasileios Papapostolou; Hamesh Patel; Andrea Polidori; Jennifer A. Salmond; David E. Williams
    更新日期:2020-01-13
  • Influence of Arctic Oscillation abnormalities on spatio-temporal haze distributions in China
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-11
    Shuhua Lu; Jianjun He; Sunling Gong; Lei Zhang

    This study investigates the impact of Arctic Oscillation (AO) abnormalities on the haze days in China for 57 winters from 1961 to 2017. The results reveal that that AO abnormalities mainly affected meteorological conditions and haze pollution in northern and central China, while their impact on the southeast coastal and Guangdong-Guangxi regions is not significant. During years with an abnormally high AO index (AOI) in winter, the number of haze days increased in northern and central China, especially in the Shanxi–Shandong–Hebei–Beijing–Tianjin and Hubei–Hunan–Henan–Jiangxi regions, while the number of haze days decreased during years of abnormally low AOI. When in the years of abnormally high AOI, the weakening of the East Asian trough caused the decrease of the meridional circulation and the increase of zonal winds compared with normal years. Furthermore, the weakening of the Siberian high pressure and the enhancement of the westerly circulation affected several meteorological factors, including the boundary layer height, surface temperature, wind speeds, and precipitations. These changes effectively inhibited the development of low-level vertical motion and the vertical diffusion of pollutants in the air, leading to the accumulation of haze pollution. The situation was the opposite for low AOI years, but the impact on the meteorological conditions was relatively weak compared to that during high AOI years. The impacts of the regional characteristics of AO abnormalities on the haze days are also investigated in this study.

    更新日期:2020-01-13
  • Asthma mortality is triggered by short-term exposures to ambient air pollutants: Evidence from a Chinese urban population
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-10
    Yunquan Zhang; Qianqian Xiang; Chuanhua Yu; Zhiming Yang

    Background Short-term exposure to ambient air pollution (AAP) has been widely linked to asthma morbidity such as outpatient and emergency visits and hospitalization. Up to date, however, the acute effects of AAP exposure on asthma mortality remained largely unknown possibly due to the rare occurrence of asthma deaths. Objectives This study aimed to investigate whether the death risks from asthma are triggered by short-term AAP exposures in a Chinese urban population who suffered poor air quality. Methods 1385 asthma death cases were identified from the total 61.3 thousand death records in two urban districts in Wuhan, central China, 2003–2013. We performed a time-stratified case-crossover design and conditional logistic regression models were applied to assess short-term associations of air pollutants (particulate matter with aerodynamic diameter ≤10 μm [PM10], sulfur dioxide [SO2], and nitrogen dioxide [NO2]) along different exposure days with asthma mortality. Results A total of 1385 case days and 4668 control days were investigated during the study period. Daily mean concentrations of PM10, SO2, and NO2 were 116.6 μg/m3, 53.4 μg/m3, and 60.7 μg/m3, respectively. A 10 μg/m3 rise in exposure to SO2 and NO2 at 2 days prior to death (lag 2 days), was associated with increased asthma death risks of 2.9% (odds ratio [OR] = 1.029, 95% confidence interval [CI]: 1.006, 1.053) and 4.3% (OR = 1.043, 95% CI: 1.012, 1.076), respectively. No evident PM10-asthma associations were identified in all subpopulations except for those aged 85 + years (OR = 1.022, 95% CI: 1.001 to 1.044). In our stratified analyses, significant effects of SO2 and NO2 were only observed in female, the older elderly, 7+ years-educated and unmarried persons, as well as those died outside the hospital and in cold season. We observed some evidence for effect modification by age, with p-values of 0.032 for PM10 and 0.051 for SO2, suggesting higher vulnerability to air pollution among the older asthma cases. Conclusions This study provided suggestive evidence for the short-term association between air pollution exposure and asthma death in highly polluted urban areas. Several days’ high-level exposures to air pollutants, particularly SO2 and NO2, may elevate risks of asthma death. Our findings highlighted the potential health benefits from intervention and preventive actions targeted to reducing AAP exposure among asthma patients.

    更新日期:2020-01-11
  • ‘Envilution™’ chamber for performance evaluation of low-cost sensors
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-08
    Hamid Omidvarborna; Prashant Kumar; Arvind Tiwari
    更新日期:2020-01-09
  • Apportioning prescribed fire impacts on PM2.5 among individual fires through dispersion modeling
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-08
    Ran Huang; Momei Qin; Yongtao Hu; Armistead G. Russell; M.Talat Odman

    Prescribed burning is a prominent source of PM2.5 in the southeastern U.S. An air quality forecasting system called HiRes2 currently serves most areas in the southeastern U.S. to forecast PM2.5 concentrations one day in advance, including the impact of forecast prescribed burning activity. The output prescribed fire impact from the HiRes2 forecasting system is the combined impact of all the fires in the domain. When there are many fires close to each other, it is difficult to distinguish the ones that are more likely to lead to air quality issues. A novel source apportionment method, Dispersive Apportionment of Source Impacts (DASI), has been developed and applied to split the combined prescribed fire impact obtained from a chemical transport model (CTM) by using simulated fields from a dispersion model. Comparisons of apportioned fire impacts with single burn impacts simulated directly by the CTM show that DASI works well with large and small fires that do not have too much interaction with other fires. Individual fire impacts obtained by splitting the combined fire impacts from CTMs could help local land and air quality managers to evaluate which burns should be allowed or restricted based on their individual impacts on air quality and public health in areas of concern.

    更新日期:2020-01-08
  • Cigarette smoking increases deaths associated with air pollution in Hong Kong
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-08
    Shengzhi Sun; Wangnan Cao; King-Pan Chan; Jinjun Ran; Yang Ge; Yunquan Zhang; Yilin Feng; Qiang Zeng; Ruby Siu-yin Lee; Chit-Ming Wong; Linwei Tian; Yujie Lei

    Background Ambient air pollution and cigarette smoking are two significant risk factors for mortality; however, less is known about their interaction. Objectives We aimed to assess effect modification of cigarette smoking on the association between short-term exposure to air pollution and mortality in the Chinese Elderly Health Service Cohort in Hong Kong. Methods We included 16,290 Chinese elders aged 65 years or older who died between 1 July 1998 and 31 December 2011. Smoking history was collected through face-to-face interviews by registered nurses or doctors using a standardized structured questionnaire when they were recruited into the cohort. We used a time-stratified case-crossover approach to estimate the percent excess risk (ER%) of all-natural mortality per 10 μg/m3 increase in fine particulate matter (PM2.5), respirable particulate matter (PM10), and nitrogen dioxide (NO2) among current-, ex-, and never-smokers, and to estimate the additional percent excess risk (ΔER%) for current- and ex-smokers relative to never-smokers. We performed secondary analysis to assess whether the estimated additional risks varied by personal characteristics. Results There were a greater ER % associated with air pollutants among current- and ex-smokers relative to never-smokers. We found ΔER% per 10 μg/m3 increase in air pollutants was statistically significant for PM2.5 among ex-smokers [2.63% (95% CI: 0.39%, 4.88%) at 1 day prior to death (lag1)], and PM10 among current-smokers [2.21% (95% CI: 0.08%, 4.33%) at lag1] and ex-smokers [1.96% (95% CI: 0.26%, 3.65%) at lag1]. The increased risks associated with cigarette smoking were more pronounced among males, overweight or obese elders, elders with three or more comorbidities, or elders received primary or lower education. Conclusion Ever-smokers were more susceptible to excess mortality risk associated with daily air pollution, especially for males, overweight or obese elders, and those with poor health conditions or received lower educational attainment. Tobacco control can reduce the health burdens attributable to air pollution.

    更新日期:2020-01-08
  • The present-day atmospheric dust deposition process in the South China Sea
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-07
    Shuhuan Du; Rong Xiang; Jianguo Liu; Paul Liu; G.M. Ariful Islam; Muhong Chen

    Modern dust plays essential roles in marine and climate processes, which bring continental material to the ocean and sensitivity in marine ecosystems. However, the atmospheric dust deposition process has rarely been studied in the South China Sea (SCS). Here, we present 51 atmospheric dust samples, collected along the SCS, to investigate the grain size distribution, depositional flux, and features revealed by scanning electron microscopy, combined with 5-day back trajectories to indicate the present-day dust deposition process for the first time. The grain size distribution and depositional flux of aerosol samples illustrate the seasonal trend, coarser particle and higher flux mass in winter than summer, reflected in average grain size (5.75 μm during winter and 3.62 μm from summer) and 1.4 times depositional flux in former than that in summer, both are related to the transport pathway and power of the East Asian monsoon. Modeled 5-day back trajectories of dust samples suggest a southwesterly transport pathway in summer and the Southeast Asian monsoon as a possible source of the dust loading, while the northeast winds drove the aeolian dust transport during the winter monsoon from the Asian continent. Meanwhile, westerly circulation conveys the fine particles (∼0.63 μm) as the stable terrigenous component into the SCS, deposited through the entire dust deposition process from the atmosphere and water to the surface sediment. Furthermore, the surface of quartz particles from atmospheric dust shows the unique structure in the aeolian environment as a reference to distinguish the different continental components in the sediments. This study provides new insights into the present-day dust deposition process in the SCS, significantly extending the current understanding of the relationship between atmospheric dust and the marginal sea.

    更新日期:2020-01-07
  • Control of both PM2.5 and O3 in Beijing-Tianjin-Hebei and the surrounding areas
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-07
    Songlin Xiang; Junfeng Liu; Wei Tao; Kan Yi; Jiayu Xu; Xiurong Hu; Huazhen Liu; Yuqing Wang; Yizhou Zhang; Haozhe Yang; Jianying Hu; Yi Wan; Xuejun Wang; Jianmin Ma; Xilong Wang; Shu Tao

    Serious haze pollution (e.g., PM2.5, particulate matter with aerodynamic diameters less than 2.5 μm) and increased ground-level ozone are severe air quality issues in China. In Beijing-Tianjin-Hebei and the surrounding areas (denoted as BTH&SA), although recently the particulate matter pollution appeared to be under control due to stringent pollution mitigation measures, ozone pollution rebounded rapidly, especially during summers. Thus, the exploration of strategies for efficiently lowering both ground-level ozone and PM2.5 concentrations is urgently needed. In this study, we target on the precursors contributing to both ozone and PM2.5 formation (i.e., NOx and volatile organic compounds (VOCs)) and adopt a Combined Empirical Kinetics Modeling Approach (CEKMA) to synthetically evaluate the cost-effective mitigation strategies for air quality control. We find that over the BTH&SA region, the choice of mitigation strategy in the initial stage (e.g., within 20% reductions on NOx or VOCs emissions) is critical because NOx-focused strategies may exacerbate O3 pollution. In addition, equally reducing NOx and VOCs emissions may have the least benefit for air pollution improvement. From a long-term perspective, we suggest reducing VOCs emissions by ∼60% and NOx emissions by ∼20% in the first stage, thereby avoiding the potential increase in ambient O3. Then in the second stage, the remaining VOCs and NOx emissions should be phased out to reach a deep mitigation of PM2.5 and O3. With those steps, both PM2.5 and ozone can be mitigated efficiently over the BTH&SA region.

    更新日期:2020-01-07
  • Characteristics of the atmospheric boundary layer and its relation with PM2.5 during haze episodes in winter in the north China Plain
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-07
    Qianhui Li; Bingui Wu; Jingle Liu; Hongsheng Zhang; Xuhui Cai; Yu Song

    Interactions between the spatiotemporal distribution of pollutants and the structure of the atmospheric boundary layer were studied using data obtained by GPS (Global Positioning System) sounding balloons in an intensive observation period from December 2018 to January 2019 at the Dezhou experimental station in the North China Plain. Under haze weather conditions, negligible variation or a slight increase in temperature, higher relative humidity (RH) and lower wind speed with uncertain wind direction are common characteristics. The concentration distribution of particulate matter ≤2.5 μm (PM2.5) has a close relationship with the inversion layer, which contributes to the accumulation of PM2.5 in the lower atmosphere. The reduction of pollutants suspended in the upper layer during haze periods is closely related to low-level jets and intermittent turbulence. Higher RH values are also favourable for the formation of heavy haze, and the value of PM2.5 increases with an increase in humidity. During hazy days, the heat fluxes and turbulent kinetic energy (TKE) are much smaller than those during clear days. The values of the average maxima of net radiation, sensible heat flux, and latent heat flux are 154, 76, and 15 W/m2, respectively, and the value of TKE is approximately 0.67 m2/s2. The decrease in atmospheric boundary layer height (ABLH) is caused by weaker turbulent transfer during haze episodes. The ABLH is approximately 400 m during the daytime and 240 m at night. The power function relationship is shown by a negative correlation between the ABLH and surface PM2.5 concentration in the convective boundary layer.

    更新日期:2020-01-07
  • The vertical profiles of carbonaceous aerosols and key influencing factors during wintertime over western Sichuan Basin, China
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-07
    Daiying Yin; Suping Zhao; Jianjun Qu; Ye Yu; Shichang Kang; Xiaolin Ren; Jing Zhang; Yong Zou; Longxiang Dong; Jianglin Li; Jianjun He; Ping Li; Dahe Qin

    With Tibetan Plateau higher than 4 km to the west, the location of Sichuan Basin is unique all around the world and provides a good platform to study air pollution in the urban agglomerations over the complex terrain. To fill in the blanks on vertical distributions of PM1 (the particles smaller than 1 μm) and carbonaceous aerosols within the basin, by means of high topographic relief, PM1 were off-line sampled during 20 January to 2 February 2018 at eight sites with increasing altitudes from the basin to southeastern margins of the Tibetan Plateau. The regional potential sources for each site were revealed by HYbrid-Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model and concentration-weighted trajectory (CWT) method. The lowest carbonaceous aerosol levels occurred at Lixian, while the highest OC (organic carbon) (EC, elemental carbon) was at Hongyuan (the altitude of 3500 m) (Ande, a rural site) due to more primary emissions. The pollutants inside the basin can be transported the altitudes from 2 km to 3 km by vertical dispersion, but they cannot be dispersed to higher altitudes. The vertical stratification of the pollutants was obvious and easily formed “high-low-high” pattern from Sichuan Basin to southeastern Tibetan Plateau, especially during highly polluted episodes. The regional potential sources significantly varied as the increased altitudes. Regional pollution was significant inside the basin. The sources at the altitudes from 2 km to 3 km originated from southeastern margins of the Plateau and surrounding cities, while those at higher altitudes were transported from southeastern margins of the Plateau. The impact of basic meteorological variables (temperature, wind speed and vapor pressure) on carbonaceous aerosols was opposite between the basin and Plateau sites. This study was essential to understanding formation mechanisms of severe pollution episodes and thus to making control measures for the urban agglomerations inside the mountainous terrain.

    更新日期:2020-01-07
  • Impact of Chinese air pollutants on a record-breaking PMs episode in South Korea for 11–15 January 2019
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-07
    Hye-Ryun Oh; Chang-Hoi Ho; Youn-Seo Koo; Kwan-Gu Baek; Hui-Young Yun; Sun-Kyong Hur; Dae-Ryun Choi; Jong-Ghap Jhun; Jae-Seol Shim

    A record-breaking episode of highly concentrated particulate matter (PM) with diameters ≤ 2.5 μm (PM2.5) and ≤10 μm (PM10) occurred in South Korea during the period January 11–15, 2019: the hourly PM2.5 (PM10) in Seoul was 188 μg m−3 (262 μg m−3) on January 14. At the Baengnyeong and Socheongcho stations, located in the Yellow Sea between China and Korea, the hourly PM2.5 concentration reached up to 155 μg m−3 and 119.8 μg m−3, respectively, 16−19-h prior to this episode. This and the fact that the maximum PM10 concentration at Baengnyeong was 199 μg m−3 indicated a westerly transport of air pollutants. Satellite observations and 72-h back trajectory analysis clearly indicate that air pollutants from China flowed into Korea via the westerlies. According to contribution analysis using particulate matter source apportionment technology in the Comprehensive Air-quality Model with extension, air pollutants originating from northeastern China including Hebei and Shandong provinces were largely linked to the present record-breaking high concentration event in Seoul. This study will elucidate the mechanism of transboundary transport of air pollutants and help East Asian countries cooperate on air quality management.

    更新日期:2020-01-07
  • Health effects of PM2.5 emissions from on-road vehicles during weekdays and weekends in Beijing, China
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-03
    Ruipeng Tong; Jiefeng Liu; Wei Wang; Yingqian Fang
    更新日期:2020-01-04
  • Variation of the aerosol optical properties and validation of MODIS AOD products over the eastern edge of the Tibetan Plateau based on ground-based remote sensing in 2017
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-02
    Yinchang You; Tianliang Zhao; Yong Xie; Yu Zheng; Jun Zhu; Junrong Xia; Le Cao; Chenggang Wang; Huizheng Che; Yao Liao; Jingxin Duan; Jiashu Zhou; Xiaoou Zhou

    The aerosol change over the Tibetan Plateau (TP) is poorly understood due to the scarcity of aerosol measurements over the TP. The aerosol optical properties were measured with a CE-318 sun photometer from January to December in 2017 at the Litang station (30.00°N, 100.16°E, 3950.5 m a.s.l.) over the eastern edge of the TP to characterize the variations in the aerosol optical properties and assess the applicability of MODIS AOD products at the eastern edge of TP. The analyses show that the annual mean aerosol optical depth at 440 nm (AOD440nm) is 0.08 ± 0.03. The mean annual Angström exponent between 440 and 870 nm (AE440–870nm) is 0.72 ± 0.23. The monthly-averaged AOD440nm exhibits a maximum (0.11 ± 0.04) in July and minimum (0.05 ± 0.02) in January, while the monthly mean AE440–870nm shows a maximum (1.08 ± 0.19) in July and minimum (0.48 ± 0.32) in February. The findings based on measured AOD440nm and AE440–870nm indicate low AOD, dominated by coarse particles in winter and fine particles in summer over the eastern TP edge. Three datasets of MODIS AOD products with 3 km spatial resolution as well as with 10 km spatial resolution based on Dark Target (DT) and Deep Blue (DB) algorithms are validated using the ground-based measurements over the eastern edge of the TP. Although the validations show a low accuracy of MODIS AOD products of the three datasets over this TP region, the MODIS AOD products based on the DB algorithm with 10 km resolution could be used in the atmospheric environment over the eastern edge of the TP based on the best match between AOD data and ground-based measurements, the lowest retrieval error, and the largest percentage falling within the expected error envelope.

    更新日期:2020-01-02
  • Classification of circulation patterns during the formation and dissipation of continuous pollution weather over the Sichuan Basin, China
    Atmos. Environ. (IF 4.012) Pub Date : 2020-01-01
    Yu Sun; Tao Niu; Jianjun He; Zhenfeng Ma; Ping Liu; Dixiang Xiao; Junfeng Hu; Jingchao Yang; Xiaolu Yan

    Pollution weather may cause serious damages to human life and property. Meteorological conditions like large-scale circulation can affect the formation and dissipation of pollution weather. We apply the hierarchical clustering method to classify circulation patterns based on the National Centers for Environmental Prediction (NCEP) Final Operational Global Analysis (FNL) sea level pressure (SLP) daily data and investigate their features during the formation and dissipation process of the defined 31 continuous pollution weather (CPW) cases in the Sichuan Basin using the meteorological data from 104 surface observation stations during 2007–2017. We find that the Sichuan Basin during the formation process is controlled by the large scale high-pressure circulation at sea level, and the SLP can be divided into high-pressure front type FC1 (32%) with the high pressure located in the west of the Basin, weak high-pressure type FC2 (35%) with the weak high pressure located in the Basin, and uniform pressure field type FC3 (33%) with the near homogeneous pressure distributed in the Basin. The Sichuan Basin during the dissipation process is dominated by the low-pressure circulation at sea level, and the SLP can be classified as low-pressure type DC1 (35%) with the low pressure centralize in the Basin, low-pressure front type DC2 (38%) with the low pressure center in the west of the Basin, and low-pressure bottom type DC3 (27%) with the low pressure in the north of the Basin. Besides, the wind, relative humidity, geopotential height and temperature data are used to explore the formation and dissipation mechanisms of the CPW. The wind speed and temperature are lower during the formation phase of the CPW compared to those from the dissipation phase. Furthermore, we estimate the effects of the CPW on pollutants based on the air quality index and Particulate Matter (PM10 and PM2.5) concentration from environmental protection monitoring data during 2013–2017. The FC2 type shows the strongest enhancement of pollutants (36%), and the DC3 circumstance generates the most efficient scavenging mechanism to dispel pollutants (−57%).

    更新日期:2020-01-01
  • Identifying key factors influencing model performance on ground-level ozone over urban areas in Japan through model inter-comparisons
    Atmos. Environ. (IF 4.012) Pub Date : 2019-12-31
    Satoru Chatani; Kazuyo Yamaji; Syuichi Itahashi; Masahiko Saito; Masayuki Takigawa; Tazuko Morikawa; Isao Kanda; Yukako Miya; Hiroaki Komatsu; Tatsuya Sakurai; Yu Morino; Tatsuya Nagashima; Kyo Kitayama; Hikari Shimadera; Katsushige Uranishi; Yuzuru Fujiwara; Soma Shintani; Hiroshi Hayami

    Ozone is one of remaining air quality issues in Japan. Effective strategies are required to reduce ozone at the ground level. Regional chemical transport models are useful in investigating relationships between precursor emissions and ambient concentrations of secondary pollutants including ozone. Model performance on ozone concentrations over urban areas in Japan were thoroughly evaluated in model inter-comparisons conducted in Japan's study for reference air quality modeling (J-STREAM). Specifically, 33 models with different configurations including the Community Multiscale Air Quality Modeling System (CMAQ), the Comprehensive Air Quality Model with Extensions (CAMx), and the Weather Research and Forecasting (WRF) model coupled with Chemistry (WRF-Chem) participated. They realized inter-comparisons with an unprecedented number of different model configurations. All the participating models overestimated ozone concentrations by 22 ± 4.6 ppb over urban areas in Japan during the summer. Spatial and temporal variations in model performance suggest the influence of background ozone concentrations. Based on differences in the participating model configurations, halogen chemistry and deposition, dry deposition velocity, precursor emissions in other countries, and vertical transport were identified as the key factors influencing simulated background ozone concentrations. Specific sensitivity analyses were conducted to evaluate the effects of the key influencing factors. Halogen chemistry and deposition implemented in recent versions of CMAQ caused more than 10 ppb reduction of simulated ozone over the ocean surrounding Japan, while the original dry deposition schemes used in CAMx and WRF-Chem, without any effect of halogen, can also cause larger dry deposition. Horizontal and downward transport of ozone kept in a residual layer over the continent can spread the effect of precursor emissions in other countries to downwind regions, including Japan. Differences in vertical transport can alter the spatial extent of their effects. It is essential to improve the influence of the aforementioned key factors to realize better model performance on ozone concentrations over urban areas, not only in Japan, but all over the world.

    更新日期:2019-12-31
  • Observations of ozone formation in southern African savanna and grassland fire plumes
    Atmos. Environ. (IF 4.012) Pub Date : 2019-12-30
    Ville Vakkari; Johan P. Beukes; Miroslav Josipovic; Pieter G. van Zyl

    Open biomass burning is one of the largest sources of aerosols and reactive trace gases into the atmosphere, having a significant effect on earth's radiative budget and air quality. Biomass burning degrades air quality by increasing both particulate matter and ozone levels. Unlike aerosols, ozone is not directly emitted in fires but it is frequently formed in ageing plumes. This is not surprising, as many of the reactive trace gases emitted in biomass burning including nitrogen oxides, carbon monoxide and volatile organic compounds, act as precursors for ozone formation. Geographically, Africa is the most significant source region of biomass burning emissions. Here, we report rapid ozone formation in daytime savanna and grassland fire plumes observed in South Africa. We observed higher ozone production in more flaming cases for plumes fresher than 1.5h. However, in plumes aged >1.5h combustion characteristics have no effect, but ozone production is positively correlated with nitrogen oxides. Furthermore, the plumes with highest ozone production also had the strongest secondary aerosol formation during plume ageing. Additionally, we report emission factors of nitric oxide and sulphur dioxide for southern African savanna and grassland fires. SO2 emission factor was on average 1.1 g kg−1, which is two to three times higher than previous observations for savanna and grassland. On the other hand, the average NO emission factor (2.6 g kg−1) agrees well with previous observations.

    更新日期:2019-12-31
  • Seasonal variability of VOCs in Nanjing, Yangtze River delta: Implications for emission sources and photochemistry
    Atmos. Environ. (IF 4.012) Pub Date : 2019-12-30
    Wang Ming; Qin Wei; Chen Wentai; Zhang Lin; Zhang Yong; Zhang Xiangzhi; Xie Xin
    更新日期:2019-12-30
  • Spatiotemporal variation in the impact of meteorological conditions on PM2.5 pollution in China from 2000 to 2017
    Atmos. Environ. (IF 4.012) Pub Date : 2019-12-28
    Yanling Xu; Wenbo Xue; Yu Lei; Qing Huang; Yang Zhao; Shuiyuan Cheng; Zhenhai Ren; Jinnan Wang

    Fine particulate matter (PM2.5) concentration that exceeds standards is causing poor air quality in most Chinese cities. Meteorological conditions are an important factor affecting PM2.5 concentration, but few quantitative studies have been conducted on the effects of long-term and large-scale changes in meteorological factors on PM2.5 pollution. In this study, a Weather Research and Forecasting/Community Multiscale Air Quality (WRF/CMAQ) modeling system was applied to study the spatial and temporal distributions of the impact of meteorological conditions on PM2.5 pollution in China from 2000 to 2017. During the study period, Me-PM2.5 decreased in general (P = 0.0018) in nationwide, and showed significant spatiotemporal variations. There was an overall increasing trend for Beijing, Fujian, Shaanxi, Gansu, and Qinghai provinces (P < 0.05) as the meteorological conditions deteriorated, and there was an overall negative trend for nine provinces (P < 0.05) which indicated meteorological conditions were causing a decrease in concentrations. Substantial differences in the impact of meteorological changes on PM2.5 pollution were observed across the provinces, with FMe-PM2.5 (fluctuating range of Me-PM2.5) between 9.3% and 55.1%. In addition, the best, typical, and worst meteorological years were selected based on Me-PM2.5; these should be considered when setting air quality goals and pollution control plans.

    更新日期:2019-12-29
  • Impacts of some co-dissolved inorganics on in-cloud photochemistry of aqueous brown carbon
    Atmos. Environ. (IF 4.012) Pub Date : 2019-12-28
    Debajyoti Ray; Sanjay K. Ghosh; Sibaji Raha

    This experimental study explored the impacts of some codissolved inorganic ions (in particular, sulfate, nitrate and chloride) on the photo-bleaching kinetics of the aqueous solutions of brown carbon (BrC) extracted from rice-straw smoldering aerosol. All the aqueous BrC solutions showed two distinct phases of decreasing mass absorption coefficient (MAC) with irradiation time, where the first phase (0–1h) was 2.4–5.3 times faster than the second phase (1–3h). Interestingly, the photo-bleaching process was slowed down for both phases when SO42− (0–1h: 0.196±0.02 h−1; 1–3h: 0.045±0.01 h−1), NO3− (0–1h: 0.158±0.004 h−1; 1–3h: 0.066±0.007 h−1) and Cl− (0–1h: 0.169±0.007 h−1; 1–3h: 0.032±0.006 h−1) salt solutions were added separately to the BrC extracts (0–1h: 0.27±0.04 h−1; 1–3h: 0.067±0.01 h−1). Alternatively, the corresponding lifetimes of the light-absorbing organic species were enhanced in the salt-added BrC solutions. In addition, the magnitudes of the fluorescence quantum yields were measured to be of the order of 10−3−10−2, implying that most of the absorbed solar energy would convert into heat rather than fluorescing back into the atmosphere. The findings of this study are suggestive of possible increase in heating of BrC containing atmospheric aqueous bodies like cloud-water, resulting in water evaporation and hence reduced precipitation (semi-direct effect).

    更新日期:2019-12-29
  • Physical and chemical properties of non-exhaust particles generated from wear between pavements and tyres
    Atmos. Environ. (IF 4.012) Pub Date : 2019-12-28
    C.A. Alves; A.M.P. Vicente; A.I. Calvo; D. Baumgardner; F. Amato; X. Querol; C. Pio; M. Gustafsson

    A road simulator was used to generate wear particles from the interaction between two tyre brands and a composite pavement. Particle size distributions were monitored using a scanning mobility particle sizer and an aerosol particle sizer. Continuous measurements of particle mass concentrations were also made. Collection of inhalable particles (PM10) was conducted using a high-volume sampler equipped with quartz filters, which were then analysed for organic and elemental carbon, organic constituents and elemental composition. Tyre fragments chopped into tiny chips were also subjected to detailed organic and elemental speciation. The number concentration was dominated by particles <0.5 μm, whereas most of the mass was found in particles >0.5 μm. The emission factor from wear between pavements and tyres was of the order of 2 mg km−1 veh−1. Organic carbon represented about 10% of the PM10 mass, encompassing multiple aliphatic compounds (n-alkanes, alkenes, hopanes, and steranes), PAHs, thiazols, n-alkanols, polyols, some fragrant compounds, sugars, triterpenoids, sterols, phenolic constituents, phthalate plasticisers and several types of acids, among others. The relationship between airborne particulate organic constituents and organic matter in tyre debris is discussed. The detection of compounds that have been extensively used as biomass burning tracers (e.g. retene, dehydroabietic acid and levoglucosan) in both the shredded tiny tyre chips and the wear particles from the interaction between tyres and pavement puts into question their uniqueness as markers of wood combustion. Trace and major elements accounted for about 5% of the mass of the tyre fragments but represented 15–18% of the PM10 from wear, denoting the contribution of mineral elements from the pavement. Sulphur and zinc were abundant constituents in all samples.

    更新日期:2019-12-29
  • Characteristics and meteorological mechanisms of transboundary air pollution in a persistent heavy PM2.5 pollution episode in Central-East China
    Atmos. Environ. (IF 4.012) Pub Date : 2019-12-28
    Shi Chune; Ifeanyichukwu C. Nduka; Yang Yuanjian; Huang Yong; Yao Risheng; Zhang Hao; He Bingfang; Xie Chengbo; Wang Zhenzhu; Steve H.L. Yim

    Previous research has shown the significant transboundary air pollution (TAP) in China. Despite its adverse environmental and human health impacts, the characteristics and mechanisms of TAP have yet to be fully understood. This study comprehensively analyzed intensive ground and upper levels measurements along with the atmospheric modeling approach to determine the driving meteorological conditions to the formation and evolution of a persistent severe PM2.5 pollution episode in Central-East China (CEC, 112°E −118°E, 30°N −34°N) starting from 18:00 on Dec. 3 to 18:00 on Dec. 5, 2017, which had obvious characteristics of TAP and explosive increases in PM2.5 concentration. We assessed and quantified contributions of local and nonlocal emissions to PM2.5 in the region and different cities during the episode and determined the altitude level at which TAP occurred. Results show that PM2.5 concentration in most cities in CEC region experienced two major increases: the first increase was due to the change in wind direction from south to north, transporting pollutants from north China to CEC; the second increase was driven by several important meteorological factors, including warm/cold advection at different altitudes, large-scale subsidence, and radiative cooling, jointly resulting in a deep (reaching around 800 m) and strong elevated temperature inversion with a significant reduction in mixing layer thickness and thus causing a rapid increase in PM2.5 concentration in CEC region. On average, TAP accounted for 42% of total PM2.5 concentration in the region during the event, in which the TAP impact varied by cities, ranging from ∼26% to ∼70%. Our findings demonstrate the synergetic effect of TAP and large-scale subsidence, providing a critical reference for air pollution forecast and assessment in the eastern China.

    更新日期:2019-12-29
  • Precipitation chemistry and atmospheric nitrogen deposition at a rural site in Beijing, China
    Atmos. Environ. (IF 4.012) Pub Date : 2019-12-28
    Wen Xu; Zhang Wen; Bo Shang; Anthony J. Dore; Aohan Tang; Xiaoping Xia; Aihua Zheng; Mengjuan Han; Lin Zhang; Yuanhong Zhao; Guozhong Zhang; Zhaozhong Feng; Xuejun Liu; Fusuo Zhang

    Precipitation chemistry and atmospheric nitrogen (N) deposition are of great concern worldwide due to their close relationships with air quality and impacts on ecosystems. However, evaluation of the chemical composition of precipitation and N deposition flux in rural areas of Beijing has received little attention to date. This paper presents the chemical constituents, possible sources and wet deposition fluxes of water-soluble ions (NH4+, NO3−, SO42−, Cl−, Na+, K+, Ca2+, Mg2+) in precipitation samples collected during 2017–2018 at a rural site located at northwest of Beijing city; meanwhile, dry deposition of reactive N species (gaseous ammonia, nitrogen dioxide, nitric acid, and particulate (p) NH4+ and NO3−) were also quantified. During this 2-year period, the volume-weighted mean (VWM) pH of precipitation was 6.73, and all samples had pH values above 6.0. The VWM electric conductivity of precipitation and the mean sum of all measured ions was 43.8 μS cm−1 and 591.9 μeq L−1, respectively, indicating a significant impact of atmospheric pollution. Ca2+ and NH4+ were the dominant neutralizing species for precipitation acidity. Positive matrix factorization analysis further confirmed five sources for water-soluble ions, including sea salt aging, secondary formation, agriculture, crust, and biomass burning. The annual mean wet N deposition was 4.6, 3.4 and 8.0 kg N ha−1 yr−1 for NH4+, NO3− and total inorganic N, respectively. The total dry N deposition was dominated by gaseous ammonia (11.5 kg N ha−1 yr−1). The total N deposition (wet plus dry) was 27.7 kg N ha−1 yr−1, where dry deposition contributed to 75% and wet deposition 25% of the total. The simulations from the GEOS-Chem model indicate that agricultural (fertilizer use and livestock) and nonagricultural sources (industry, power plant, and transportation) are both important contributors to total N deposition. These results could be useful in evaluating/developing emission control policies to protect the eco-environment in Beijing.

    更新日期:2019-12-29
  • Evaluation and improvement of MODIS aerosol optical depth products over China
    Atmos. Environ. (IF 4.012) Pub Date : 2019-12-28
    Yi Li; Guoping Shi; Zhian Sun

    In this study, we use the level-1.5 and level-2.0 aerosol optical depth (AOD) from the Aerosol Robotic Network (AERONET) Version 3 dataset at 12 sites in China to evaluate the MODIS Collection 6.1 (C6.1) AOD products retrieved using three distinct algorithms: Dark Target (DT), Deep Blue (DB), and DTB merged from DT and DB from Terra and Aqua. The performance of the three algorithms is evaluated. Based on these evaluations, a simple and efficient AOD retrieval algorithm at a high spatial resolution of 1.0 km for China is proposed. AODs at this spatial resolution over China are then retrieved using the methods of DT and DB, respectively. The evaluation results showed that: (1) there is little difference in the AOD products derived from Terra and Aqua. The differences in the determination coefficient (R2) between the two platforms at most sites are less than 0.05. (2) There are relatively large differences in AODs between the AERONET level-1.5 dataset and MODIS dataset while these differences are mostly filtered out by the quality assurance process of the AERONET level-2.0 dataset. The statistical tests indicate that the MODIS DTB AOD product is generally better than those from the other two algorithms. Using the new algorithm developed in this study, the AODs at a high spatial resolution of 1 km in the whole of China are determined and the results are compared with the MODIS DTB product. The results show that the AODs determined using the new method agree reasonably well with those of the MODIS DTB dataset though the new results have slightly negative biases in the wintertime. However, these negative biases may not be a negative sign due to the fact that the MODIS AODs are subject to a positive bias relative to the AERONET AODs.

    更新日期:2019-12-29
  • Re-evaluation of BioSampler and its improvement for on-line, time-resolved monitoring of environmental coarse aerosol
    Atmos. Environ. (IF 4.012) Pub Date : 2019-12-26
    Yongyang Su; Wei Wang; Wenliang Wang; Lihua Zhai; Xiaopan Shen; Jiang Xu; Zhiming Li

    BioSampler is now being widely used for bioaerosol sampling. However, the sampling efficiency in wide size range especially for nanoparticles as well as the size-dependent retention efficiency have not been well evaluated until now. Through literature review, theoretic analysis and experiments, this paper reviews the sampling process, collection mechanism and sampling performance of commercial BioSampler including pressure drop as a function of sampling flow rate, the mass loss rate and temperature of the collection fluid as a function of sampling time, the variation of retention efficiency with time, and the sampling efficiency in wide size range from nanometers to microns. The effects of low pressure and high relative humidity on determination of sampling efficiency in literature were carefully analyzed. To compensate the collection fluid loss and extract the insoluble/dissolved sample for further analysis, Continuous-Extraction BioSampler (CEBS) is proposed. The retention efficiency for particles of different sizes as well as the collection efficiency were determined and found to be identical with commercial BioSampler when no steam was introduced into CEBS. Finally, the combination uses of CEBS and Inductively-Coupled-Plasma Mass Spectrometer (ICP-MS) was developed. Exponentially Modified Gaussian (EMG) Model was derived and verified to describe the temporal concentration of the dissolved component originating from individual soluble droplet. Using internal standard calibration method and EMG fitting of signal curve, the target element amount in individual droplet could be determined accurately. For continuously-collected soluble droplet with duration of minutes, the observed signal curve can be described by EMG model and the fitted value of area varies linearly with the sample amount introduced. This paper not only provides comprehensive performance evaluation of commercial BioSampler, but also demonstrates that the proposed CEBS-ICPMS is capable of monitoring environmental coarse aerosol with time resolution of ∼17 min.

    更新日期:2019-12-27
  • 更新日期:2019-12-27
  • A city-level inventory for atmospheric mercury emissions from coal combustion in China in 2010
    Atmos. Environ. (IF 4.012) Pub Date : 2019-12-26
    Zhujuan Wu; Huafeng Ye; Yuli Shan; Bin Chen; Jiashuo Li
    更新日期:2019-12-27
  • A critical view of long-term AVHRR aerosol data record in China: Retrieval frequency and heavy pollution
    Atmos. Environ. (IF 4.012) Pub Date : 2019-12-26
    Minghui Tao; Rong Li; Lili Wang; Feng Lan; Zifeng Wang; Jinhua Tao; Huizheng Che; Lunche Wang; Liangfu Chen

    The recent AVHRR aerosol products expended from MODIS Deep Blue (DB) algorithm provide an unprecedented long-term data record over land that dates back to 1980s. Unlike previous studies focused on performance of AVHRR retrievals, here we present a critical view into the influence of retrieval frequency on consistency of AVHRR Aerosol Optical Depth (AOD) with other satellite DB products, and application potential in characterizing the dramatic aerosol loading in China. Despite the good consistency of collocated AVHRR, SeaWiFS, and MODIS DB AOD, their different retrieval frequency leads to distinct distribution of annual or seasonal AOD. In particular, the over-strict cloud screening of AVHRR with fewer bands tends to filter out high-AOD and clean bright surface, with the overall AOD frequency only half of MODIS's. Retrieval frequency and selection criterion of AOD quality can determine representativity and consistency of conventional averaged satellite AOD, uncertainties of which should be considered according to specific application purpose. The time series variation of AVHRR AOD shows that early 1990s is a key time point when frequent haze pollution appears and increases in eastern China. By contrast, aerosol loading in 1995–1999 has reached similar level as in 2000s with notable hotspot of high-AOD (∼0.8–0.9) and slight changes. Our results shows that full record of AVHRR aerosol products with corresponding improvement can greatly renew the understanding of aerosols in China.

    更新日期:2019-12-27
  • Aqueous-phase oxidation of three phenolic compounds by hydroxyl radical: Insight into secondary organic aerosol formation yields, mechanisms, products and optical properties
    Atmos. Environ. (IF 4.012) Pub Date : 2019-12-24
    Zhaolian Ye; Yu Zhuang; Yantong Chen; Zhuzi Zhao; Shuaishuai Ma; Hongying Huang; Yanfang Chen; Xinlei Ge

    This work performed a systematic investigation on the aqueous hydroxyl radical (OH) - induced photochemical oxidation of three modestly-soluble precursors from biomass combustion including 4-methylsyringol (DMP), eugenol (Eug), and 2,4,6-trimethylphenol (TRMP) under both simulated sunlight and ultraviolet (UV) light irradiations. An Aerodyne soot particle aerosol mass spectrometer (SP-AMS) was used to monitor the bulk chemical and elemental compositions of aqueous secondary organic aerosol (aqSOA) formed. AqSOA mass yields varied in ranges of 80–190% and 0–200% under sunlight and UV light conditions, respectively. AqSOA oxygen-to-carbon (O/C) ratio and carbon oxidation state increased steadily under sunlight + OH condition, but increased then decreased under UV + OH condition. Organic acids including malic acid, glycolic acid, formic acid and oxalic acid were formed, and their total accounted for ∼12% of SOA mass. The UV–vis spectral change suggested formation of light-absorbing organics. Reaction pathways were proposed by combining gas chromatography-mass spectrometry (GC-MS) and SP-AMS results. Under sunlight + OH condition, oligomerization, functionalization, and fragmentation processes all involved in aqSOA evolution, with more contribution from functionalization via hydroxylation and oxygenation reactions. Reaction mechanism of UV + OH oxidation was initially dominated by functionalization then by fragmentation, indicating by the decrease of total organic carbon (TOC) contents, formation of small organic acids and low-molecular-weight products. Our work highlight that combination of SP-AMS with GC-MS is a powerful method for laboratory investigation of aqueous-phase reactions.

    更新日期:2019-12-25
  • Absorbing aerosol influence on temperature maxima: An observation based study over India
    Atmos. Environ. (IF 4.012) Pub Date : 2019-12-23
    P. Dave; M. Bhushan; C. Venkataraman

    Increasing trends in summer-time temperature maxima (Tmax) over India, show consequent increases in the intensity and frequency of heatwave events in recent years. Heat waves have been largely attributed to large-scale meteorological blocking, characterized by subsidence, clear skies and low soil moisture, in observational studies, or greenhouse gas enhancements in model studies. While radiative effects of absorbing aerosols are acknowledged, the association of absorbing aerosols with temperature maxima has not been investigated comprehensively. In the current study, statistical tools (such as correlation and Granger causality) were applied to long term (1979–2013) satellite and ground based observations to evaluate influence of absorbing aerosols on Tmax in north-west India (Tmax-NW). Regional absorbing aerosol index (AAI) in the north-west (AAI-NW) and central-India (AAI-CI) showed co-variability with Tmax-NW, implying connections to both local and non-local absorbing aerosols. The effects persisted on seasonal and heatwave event scales, becoming stronger on heatwave days with presence of enhanced AAI loadings. Causal effects of AAI-NW and AAI-CI were identified on Tmax-NW with a lag of 1–11 days, across multiple years, thereby establishing the influence of absorbing aerosols on heatwave events. The absence of confounding effects of surface pressure on these links suggests that, even during heat wave events linked to atmospheric blocking, absorbing aerosols can further enhance temperature maxima and related heat-wave intensity.

    更新日期:2019-12-23
  • Ceramic industry at Morbi as a large source of SO2 emissions in India
    Atmos. Environ. (IF 4.012) Pub Date : 2019-12-23
    S.K. Kharol; V. Fioletov; C.A. McLinden; M.W. Shephard; C.E. Sioris; C. Li; N.A. Krotkov

    Observations from the Ozone Monitoring Instrument (OMI), onboard the NASA's Earth Observing System (EOS) Aura satellite, reveal a large SO2 “hotspot” over Morbi, Gujarat, India, while the available emissions inventories do not report any major sources in this region. There are no industries that are typically associated with the elevated SO2 such as large power plants, smelters, or oil refineries in the Morbi region. Our analysis shows that the elevated SO2 source is attributed to the ceramic industries in an area of ∼7 × 7 km2 near the city. OMI-estimated SO2 emissions from the Morbi ceramic industries have been near or above 100 kt y−1 since 2009, which are similar to emission levels from larger Indian oil refineries (such as Essar and Jamnagar) and power stations (such as Mundra Thermal Power Station and Ultra Mega Power Plant) located in Gujarat, India. According to OMI measurements, the SO2 emissions from the Morbi ceramic industries are presently five times higher than they were in 2005. This study demonstrates that in the absence of any other information about SO2 emissions from the ceramic industry, these satellite-based estimates can fill the gap in emission inventories in a timely fashion.

    更新日期:2019-12-23
  • Land use regression models revealing spatiotemporal co-variation in NO2, NO, and O3 in the Netherlands
    Atmos. Environ. (IF 4.012) Pub Date : 2019-12-23
    Meng Lu; Ivan Soenarioy; Marco Helbich; Oliver Schmitz; Gerard Hoek; Michiel van der Molen; Derek Karssenberg

    Land use regression (LUR) modeling has been applied to study the spatiotemporal patterns of air pollution, which when combined with human space-time activity, is important in understanding the health effects of air pollution. However, most of these studies focus either on the temporal or the spatial domain and do not consider the variability in both space and time. A temporally aggregated model does not reflect the temporal variability caused by traffic and atmospheric conditions and leads to inaccurate estimation of personal exposure. Besides, most studies focus on a single air pollutant (e.g., O3, NO2, or NO). These pollutants have a strong interaction due to photochemical processes. For studying relations between spatial and temporal patterns in these pollutants it is preferable to use a uniform data source and modelling approach which makes comparison of pollution surfaces between pollutants more reliable as they are produced with the same methodology. We developed temporal land use regression models of O3, NO2 and NO to study the co-variability of these pollutants and the relations with typical weather conditions over the year. We use hourly concentrations from the measurement network of the Dutch National Institute for Public Health and the Environment and aggregate them by hour, for weekday/weekend and month, and fit a regression model for each hour of the day. 70 candidate predictors that are known to have a strong relationship with combustion-related emissions are evaluated in the LUR modelling process. For all pollutants, the optimal LUR was identified with 4 predictors and the temporal variability was determined by the explained variance of each temporal model. Our temporal models for O3, NO2, and NO strongly reflect the photochemical processes in space and time. O3 shows a high background value throughout the day and only dips in the (close) vicinity of roads. The diminishing rate is affected by traffic intensity. The NO2 LUR is validated against NO2 measurements from the Traffic-Related Air pollution and Children's respiratory HEalth and Allergies (TRACHEA) study, resulting in an R2 of 0.61.

    更新日期:2019-12-23
  • A high-time resolution study of PM2.5, organic carbon, and elemental carbon at an urban traffic site in Istanbul
    Atmos. Environ. (IF 4.012) Pub Date : 2019-12-23
    Rosa M. Flores; Elif Mertoğlu; Hüseyin Özdemir; Bülent O. Akkoyunlu; Göksel Demir; Alper Ünal; Mete Tayanç
    更新日期:2019-12-23
  • 更新日期:2019-12-23
  • Chemistry and sources of PM2.5 and volatile organic compounds breathed inside urban commuting and tourist buses
    Atmos. Environ. (IF 4.012) Pub Date : 2019-12-21
    Amaia Fernández-Iriarte; Fulvio Amato; Natalia Moreno; Antonio Pacitto; Cristina Reche; Esther Marco; Joan O. Grimalt; Xavier Querol; Teresa Moreno

    Inhalable particulate matter (size <2.5 μm: PM2.5) inside commuting and tourist buses moving through the city of Barcelona, Spain, was chemically analysed. The analyses show PM dominated by organic carbon (mostly 10–20 μg/m3) and elemental carbon (mostly 3–6 μg/m3; OC/EC = 3.4), followed by SO42, Fe, Ca, K, Al2O3, Mg, and Na, with calculated mineral content being around one third that of total carbon. Elemental carbon levels are higher inside diesel buses than those powered by natural gas or electricity, and higher in the upper floor of open-top double decker tourist buses than in the lower floor. Overall, major element concentrations inside the buses are typically 2–8 times higher than 24 h-averaged urban background levels, although some metallic trace elements, notably Cu and Sb, are exceptionally enriched due to the presence of brake particles, especially on routes involving higher gradients and therefore more brake use. In contrast, Cu and Sb concentrations in electric buses are unexceptional, presumably because these buses rely more on regenerative braking and are hermetically sealed when moving. Seasonal differences reveal PM to be more mineral in winter (Al2O3 1.3 μg/m3 vs. summer average of 0.3 μg/m3), with summer enrichment in Na, Mg, P, V, Ni and SO42− being attributed to marine aerosols contaminated by port emissions. Source apportionment calculations identify 6 main factors: road dust resuspension, metalliferous (brake wear and metallurgy), local urban dust, secondary sulphate and shipping (6%), vehicle exhaust (19%), and an indoor source (46%) interpreted as likely related to the textile fibres and skin flakes of bus occupants. Volatile Organic Compounds measured inside all buses except one were dominated by 2-Methylpentane (14–36 μg/m3), Toluene (10–30 μg/m3), Xylene isomers (10–28 μg/m3, with m- » o- > p-Xylene) and n-Pentane (5–15 μg/m3). ƩBTEX concentrations were <70 μg/m3, with Toluene being commonest, followed by m-Xylene, with p-Xylene, o-Xylene and Ethylbenzene each below 7 μg/m3 and Benzene concentrations always less than the EU limit value of 5 μg/m3. The VOCs mixture is similar to that recently reported from inside Barcelona taxis (although inside the larger volume bus VOC concentrations are lower than in the taxis) and is interpreted as providing a chemical fingerprint characterising traffic-contaminated ambient air in the city road environment. The notable exception to the VOC content was a brand new hybrid diesel bus still offgassing volatiles to such an extent that Ʃ(alkane + alkene + aromatic) indoor concentrations exceeded 800 μg/m3, with ƩBTEX ten times higher than normal.

    更新日期:2019-12-21
  • 更新日期:2019-12-20
  • O3 photochemistry on O3 episode days and non-O3 episode days in Wuhan, Central China
    Atmos. Environ. (IF 4.012) Pub Date : 2019-12-20
    Jiaxin Zhu; Hairong Cheng; Jin Peng; Pei Zeng; Zuwu Wang; Xiaopu Lyu; Hai Guo

    Simultaneous field measurements of ozone (O3) and its precursors were conducted at an urban site (Zi Yang, ZY) and a suburban site (Huang Pi, HP) in August 2018 in Wuhan, China. The observation results revealed that the mean levels of nitric oxide (NO), nitrogen dioxide (NO2), carbon monoxide (CO) and non-methane hydrocarbons (NMHCs) were higher at ZY than those detected at HP, while the opposite trend was observed for O3 levels. Compared to non-O3 episode days, higher levels of O3 and its precursors (i.e. NMHCs, NO and CO) were observed on O3 episode days at both ZY and HP. A chemical box model was used to investigate the O3 photochemistry on O3 episode days and non-O3 episode days at ZY and HP, and the O3 production was found to be dominated by the reaction of HO2 + NO at the two sites. In terms of O3 destruction, OH + NO2 was the major contributor at ZY, while the highest contribution at HP was from the reaction of O(1D) + H2O. The net O3 production rates increased significantly from non-O3 episode days to O3 episode days at both ZY and HP, indicating increased O3 accumulation on O3 episode days. In addition, the model simulation indicated that O3 formation was controlled by volatile organic compounds (VOCs) at ZY, whereas O3 formation was cooperative controlled by VOCs and NO at HP. Overall, these findings can provide valuable information on formulating and implementing O3 control strategies in urban and suburban areas in China.

    更新日期:2019-12-20
  • Evaluation of the MISR fine resolution aerosol product using MODIS, MISR, and ground observations over China
    Atmos. Environ. (IF 4.012) Pub Date : 2019-12-20
    Yidan Si; Liangfu Chen; Xiaozhen Xiong; Shuaiyi Shi; Letu Husi; Kun Cai

    Recently, NASA's Multiangle Imaging SpectroRadiometer (MISR) team released the Version 23 (V23) 4.4-km Aerosol Optical Depth (AOD) product, which has better spatial resolution than V22 at 17.6 km. However, its quality has not been validated in China. Here, V23 products for different spatiotemporal domains are obtained for validation against Aerosol Robotic NETwork (AERONET) AOD measurements for 29 sites from 2008 to 2017. Based on the national daily mean, V23 AOD yields a correlation coefficient (R) of 0.902 with AERONET; 59.45% of retrievals fall within the expected error (=EE; ±0.05 or ±0.2×AOD). A mean error (ME) of −0.0605 with 24.11% of retrievals falling below the EE indicates that MISR data are still underestimated at high AODs. The sample numbers and accuracies of spatially averaged 17.6-km and 50-km data are greatly improved relative to V22. The seasonal mean of V23 retrievals = EE in fall and winter are highest, followed by those in summer and spring; the validation results at 17.6 km are generally better than those at 50 km. By region, V23 retrievals = EE in the Beijing–Tianjin–Hebei (BTH), Yangtze River Delta (YRD) and Pearl River Delta (PRD) regions are 68.87%, 61.43%, and 73.13% respectively, while that of Taiwan is below 60% (55.75%). No V22 records exist in PRD, and V23 products over other regions in all seasons perform well; V22 retrievals in summer are also recommended. Compared with Terra/MODIS 3-km AOD in 2016, the V23 product has a slightly higher R value (0.925) with AERONET than MODIS (0.909). The MISR AOD bias is lower, and MODIS AOD is overestimated relative to the ground truth; both present consistent seasonality characteristics (spring > winter > summer > autumn), with the maximum in March and minimum in August. To investigate the spatiotemporal characteristics over long-term AOD, MISR V23 4.4-km AOD can be used in combination with other observation data.

    更新日期:2019-12-20
  • Arctic ship-based evidence of new particle formation events in the Chukchi and East Siberian Seas
    Atmos. Environ. (IF 4.012) Pub Date : 2019-12-19
    M. Dall´Osto; Jiyeon Park; Joo-Hong Kim; Sung-Ho Kang; Kihong Park; David Beddows; Roy Harrison; Y.J. Yoon

    Arctic aerosol-climate interactions are controlled by multiple factors including sources, processes and removal mechanisms of particles. The Arctic is mostly ocean, surrounded by mostly land, and our understanding of Arctic aerosol processes is incomplete due to scarce measurements carried out in sea ice regions. In particular, it is currently not known if these particular regions are sources of aerosols of primary or secondary origin. We present new results from ship-based measurements illustrating that marine new particle production and growth events occur in open ocean and melting sea ice regions in the Chukchi and East Siberian Seas. We report two new particle formation events during which a recently formed nucleation mode (<15 nm diameter) is detected and is observed to slowly grow into an Aitken mode (0.1–3.8 nm h−1). Our results suggest that new particle formation occurs in the marine boundary layer contributing to the Arctic aerosol population in the study region for the first time studied and herein reported.

    更新日期:2019-12-19
  • Distinction of two kinds of haze
    Atmos. Environ. (IF 4.012) Pub Date : 2019-12-19
    Ke Wei; Xiaoyan Tang; Guiqian Tang; Junxia Wang; Luyang Xu; Jing Li; Chunhuan Ni; Yanjun Zhou; Yeyi Ding; Wenjun Liu

    Haze is a phenomenon caused by suspension of fine particulate matters in the air that leads to impaired visibility. In the meteorological practice, a haze day is determined using the observation of visibility and relative humidity, after screening the special weather days of rain, snow, dust, fog and others. While in the environmental monitoring practice and relevant studies, the term haze is also commonly used and a haze day is determined using the reading of particulate matters (PM). This has actually caused two different kinds of haze day, i.e., meteorological haze days (MHDs) and environmental haze days (EHDs), each with different definition and standard. Our analysis shows that although MHDs and EHDs overlap, the proportion of MHDs in EHDS is 43% in Beijing, 44% in Shanghai, and 46% in Guangzhou. Meanwhile, there are large percentage of MHDs that are not EHDs, about 21% in Beijing, 42% in Shanghai and 67% in Guangzhou. Therefore, an explicit distinction of the two haze definitions should be made in the study of PM pollution variation and cause in China, which will have important applications in addressing air pollution, formulating environmental policy, and dealing with health effect of haze in China.

    更新日期:2019-12-19
  • Pathological damage, immune-related protein expression, and oxidative stress in lungs of BALB/c mice induced by haze PM2.5 biological components exposure
    Atmos. Environ. (IF 4.012) Pub Date : 2019-12-18
    Bo Wu; Yunxiang Dong; Meng Wang; Wenhui Yang; Lingfei Hu; Dongsheng Zhou; Jing Lv; Tongjie Chai

    Particulate matter (PM) pollution poses a huge public health threat, and exposure to haze pollution for short or long periods of time cause health problems. In this study, 16S rDNA and ITS high-throughput sequencing were used to analyze the microbial components of fine particulate matter (PM2.5) collected between December 20th and December 27th of 2016 during a severe haze in Tai'an, China. Although most inhalable microorganisms are not pathogenic to humans, we detected the presence of some types of bacteria that cause respiratory inflammation (such as Pseudomonas and Corynebacterium), allergic reactions (such as Alternaria), and lung inflammation (such as Nesterenkonia). Acute and chronic haze PM2.5 exposure experiments were conducted using BALB/c mice to gain insight about the harm these microbes may have on human health. Results indicate that acute exposure to haze PM2.5 can cause pathological lung damage, decrease the expressions of oxidative stress indicators T-AOC, SOD, and GSH-PX, increase the expression of MDA, and induce apoptosis. Furthermore, chronic exposure was found to cause more damage. Toll-like receptors can be used identify molecular patterns associated with microbial pathogens. The expression of TLR2 and TLR4 were increased in both single- and repeated-exposure groups, but they were significantly increased in the repeated-exposure group (P < 0.05). The role of biological components in PM in mediating inflammation and pathological damage should not be neglected.

    更新日期:2019-12-19
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